diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile index 34929f2..884c36b 100644 --- a/Documentation/DocBook/Makefile +++ b/Documentation/DocBook/Makefile @@ -14,7 +14,7 @@ DOCBOOKS := z8530book.xml mcabook.xml device-drivers.xml \ genericirq.xml s390-drivers.xml uio-howto.xml scsi.xml \ mac80211.xml debugobjects.xml sh.xml regulator.xml \ alsa-driver-api.xml writing-an-alsa-driver.xml \ - tracepoint.xml media.xml drm.xml + tracepoint.xml utrace.xml media.xml drm.xml ### # The build process is as follows (targets): diff --git a/Documentation/DocBook/utrace.tmpl b/Documentation/DocBook/utrace.tmpl new file mode 100644 index 0000000..0c40add --- /dev/null +++ b/Documentation/DocBook/utrace.tmpl @@ -0,0 +1,589 @@ + + + + + + The utrace User Debugging Infrastructure + + + + + utrace concepts + + Introduction + + + utrace is infrastructure code for tracing + and controlling user threads. This is the foundation for writing + tracing engines, which can be loadable kernel modules. + + + + The basic actors in utrace are the thread + and the tracing engine. A tracing engine is some body of code that + calls into the <linux/utrace.h> + interfaces, represented by a struct + utrace_engine_ops. (Usually it's a kernel module, + though the legacy ptrace support is a tracing + engine that is not in a kernel module.) The interface operates on + individual threads (struct task_struct). + If an engine wants to treat several threads as a group, that is up + to its higher-level code. + + + + Tracing begins by attaching an engine to a thread, using + utrace_attach_task or + utrace_attach_pid. If successful, it returns a + pointer that is the handle used in all other calls. + + + + + Events and Callbacks + + + An attached engine does nothing by default. An engine makes something + happen by requesting callbacks via utrace_set_events + and poking the thread with utrace_control. + The synchronization issues related to these two calls + are discussed further below in . + + + + Events are specified using the macro + UTRACE_EVENT(type). + Each event type is associated with a callback in struct + utrace_engine_ops. A tracing engine can leave unused + callbacks NULL. The only callbacks required + are those used by the event flags it sets. + + + + Many engines can be attached to each thread. When a thread has an + event, each engine gets a callback if it has set the event flag for + that event type. For most events, engines are called in the order they + attached. Engines that attach after the event has occurred do not get + callbacks for that event. This includes any new engines just attached + by an existing engine's callback function. Once the sequence of + callbacks for that one event has completed, such new engines are then + eligible in the next sequence that starts when there is another event. + + + + Event reporting callbacks have details particular to the event type, + but are all called in similar environments and have the same + constraints. Callbacks are made from safe points, where no locks + are held, no special resources are pinned (usually), and the + user-mode state of the thread is accessible. So, callback code has + a pretty free hand. But to be a good citizen, callback code should + never block for long periods. It is fine to block in + kmalloc and the like, but never wait for i/o or + for user mode to do something. If you need the thread to wait, use + UTRACE_STOP and return from the callback + quickly. When your i/o finishes or whatever, you can use + utrace_control to resume the thread. + + + + The UTRACE_EVENT(SYSCALL_ENTRY) event is a special + case. While other events happen in the kernel when it will return to + user mode soon, this event happens when entering the kernel before it + will proceed with the work requested from user mode. Because of this + difference, the report_syscall_entry callback is + special in two ways. For this event, engines are called in reverse of + the normal order (this includes the report_quiesce + call that precedes a report_syscall_entry call). + This preserves the semantics that the last engine to attach is called + "closest to user mode"--the engine that is first to see a thread's user + state when it enters the kernel is also the last to see that state when + the thread returns to user mode. For the same reason, if these + callbacks use UTRACE_STOP (see the next section), + the thread stops immediately after callbacks rather than only when it's + ready to return to user mode; when allowed to resume, it will actually + attempt the system call indicated by the register values at that time. + + + + + Stopping Safely + + Writing well-behaved callbacks + + + Well-behaved callbacks are important to maintain two essential + properties of the interface. The first of these is that unrelated + tracing engines should not interfere with each other. If your engine's + event callback does not return quickly, then another engine won't get + the event notification in a timely manner. The second important + property is that tracing should be as noninvasive as possible to the + normal operation of the system overall and of the traced thread in + particular. That is, attached tracing engines should not perturb a + thread's behavior, except to the extent that changing its user-visible + state is explicitly what you want to do. (Obviously some perturbation + is unavoidable, primarily timing changes, ranging from small delays due + to the overhead of tracing, to arbitrary pauses in user code execution + when a user stops a thread with a debugger for examination.) Even when + you explicitly want the perturbation of making the traced thread block, + just blocking directly in your callback has more unwanted effects. For + example, the CLONE event callbacks are called when + the new child thread has been created but not yet started running; the + child can never be scheduled until the CLONE + tracing callbacks return. (This allows engines tracing the parent to + attach to the child.) If a CLONE event callback + blocks the parent thread, it also prevents the child thread from + running (even to process a SIGKILL). If what you + want is to make both the parent and child block, then use + utrace_attach_task on the child and then use + UTRACE_STOP on both threads. A more crucial + problem with blocking in callbacks is that it can prevent + SIGKILL from working. A thread that is blocking + due to UTRACE_STOP will still wake up and die + immediately when sent a SIGKILL, as all threads + should. Relying on the utrace + infrastructure rather than on private synchronization calls in event + callbacks is an important way to help keep tracing robustly + noninvasive. + + + + + Using <constant>UTRACE_STOP</constant> + + + To control another thread and access its state, it must be stopped + with UTRACE_STOP. This means that it is + stopped and won't start running again while we access it. When a + thread is not already stopped, utrace_control + returns -EINPROGRESS and an engine must wait + for an event callback when the thread is ready to stop. The thread + may be running on another CPU or may be blocked. When it is ready + to be examined, it will make callbacks to engines that set the + UTRACE_EVENT(QUIESCE) event bit. To wake up an + interruptible wait, use UTRACE_INTERRUPT. + + + + As long as some engine has used UTRACE_STOP and + not called utrace_control to resume the thread, + then the thread will remain stopped. SIGKILL + will wake it up, but it will not run user code. When the stop is + cleared with utrace_control or a callback + return value, the thread starts running again. + (See also .) + + + + + + + Tear-down Races + + Primacy of <constant>SIGKILL</constant> + + Ordinarily synchronization issues for tracing engines are kept fairly + straightforward by using UTRACE_STOP. You ask a + thread to stop, and then once it makes the + report_quiesce callback it cannot do anything else + that would result in another callback, until you let it with a + utrace_control call. This simple arrangement + avoids complex and error-prone code in each one of a tracing engine's + event callbacks to keep them serialized with the engine's other + operations done on that thread from another thread of control. + However, giving tracing engines complete power to keep a traced thread + stuck in place runs afoul of a more important kind of simplicity that + the kernel overall guarantees: nothing can prevent or delay + SIGKILL from making a thread die and release its + resources. To preserve this important property of + SIGKILL, it as a special case can break + UTRACE_STOP like nothing else normally can. This + includes both explicit SIGKILL signals and the + implicit SIGKILL sent to each other thread in the + same thread group by a thread doing an exec, or processing a fatal + signal, or making an exit_group system call. A + tracing engine can prevent a thread from beginning the exit or exec or + dying by signal (other than SIGKILL) if it is + attached to that thread, but once the operation begins, no tracing + engine can prevent or delay all other threads in the same thread group + dying. + + + + Final callbacks + + The report_reap callback is always the final event + in the life cycle of a traced thread. Tracing engines can use this as + the trigger to clean up their own data structures. The + report_death callback is always the penultimate + event a tracing engine might see; it's seen unless the thread was + already in the midst of dying when the engine attached. Many tracing + engines will have no interest in when a parent reaps a dead process, + and nothing they want to do with a zombie thread once it dies; for + them, the report_death callback is the natural + place to clean up data structures and detach. To facilitate writing + such engines robustly, given the asynchrony of + SIGKILL, and without error-prone manual + implementation of synchronization schemes, the + utrace infrastructure provides some special + guarantees about the report_death and + report_reap callbacks. It still takes some care + to be sure your tracing engine is robust to tear-down races, but these + rules make it reasonably straightforward and concise to handle a lot of + corner cases correctly. + + + + Engine and task pointers + + The first sort of guarantee concerns the core data structures + themselves. struct utrace_engine is + a reference-counted data structure. While you hold a reference, an + engine pointer will always stay valid so that you can safely pass it to + any utrace call. Each call to + utrace_attach_task or + utrace_attach_pid returns an engine pointer with a + reference belonging to the caller. You own that reference until you + drop it using utrace_engine_put. There is an + implicit reference on the engine while it is attached. So if you drop + your only reference, and then use + utrace_attach_task without + UTRACE_ATTACH_CREATE to look up that same engine, + you will get the same pointer with a new reference to replace the one + you dropped, just like calling utrace_engine_get. + When an engine has been detached, either explicitly with + UTRACE_DETACH or implicitly after + report_reap, then any references you hold are all + that keep the old engine pointer alive. + + + + There is nothing a kernel module can do to keep a struct + task_struct alive outside of + rcu_read_lock. When the task dies and is reaped + by its parent (or itself), that structure can be freed so that any + dangling pointers you have stored become invalid. + utrace will not prevent this, but it can + help you detect it safely. By definition, a task that has been reaped + has had all its engines detached. All + utrace calls can be safely called on a + detached engine if the caller holds a reference on that engine pointer, + even if the task pointer passed in the call is invalid. All calls + return -ESRCH for a detached engine, which tells + you that the task pointer you passed could be invalid now. Since + utrace_control and + utrace_set_events do not block, you can call those + inside a rcu_read_lock section and be sure after + they don't return -ESRCH that the task pointer is + still valid until rcu_read_unlock. The + infrastructure never holds task references of its own. Though neither + rcu_read_lock nor any other lock is held while + making a callback, it's always guaranteed that the struct + task_struct and the struct + utrace_engine passed as arguments remain valid + until the callback function returns. + + + + The common means for safely holding task pointers that is available to + kernel modules is to use struct pid, which + permits put_pid from kernel modules. When using + that, the calls utrace_attach_pid, + utrace_control_pid, + utrace_set_events_pid, and + utrace_barrier_pid are available. + + + + + + Serialization of <constant>DEATH</constant> and <constant>REAP</constant> + + + The second guarantee is the serialization of + DEATH and REAP event + callbacks for a given thread. The actual reaping by the parent + (release_task call) can occur simultaneously + while the thread is still doing the final steps of dying, including + the report_death callback. If a tracing engine + has requested both DEATH and + REAP event reports, it's guaranteed that the + report_reap callback will not be made until + after the report_death callback has returned. + If the report_death callback itself detaches + from the thread, then the report_reap callback + will never be made. Thus it is safe for a + report_death callback to clean up data + structures and detach. + + + + Interlock with final callbacks + + The final sort of guarantee is that a tracing engine will know for sure + whether or not the report_death and/or + report_reap callbacks will be made for a certain + thread. These tear-down races are disambiguated by the error return + values of utrace_set_events and + utrace_control. Normally + utrace_control called with + UTRACE_DETACH returns zero, and this means that no + more callbacks will be made. If the thread is in the midst of dying, + it returns -EALREADY to indicate that the + report_death callback may already be in progress; + when you get this error, you know that any cleanup your + report_death callback does is about to happen or + has just happened--note that if the report_death + callback does not detach, the engine remains attached until the thread + gets reaped. If the thread is in the midst of being reaped, + utrace_control returns -ESRCH + to indicate that the report_reap callback may + already be in progress; this means the engine is implicitly detached + when the callback completes. This makes it possible for a tracing + engine that has decided asynchronously to detach from a thread to + safely clean up its data structures, knowing that no + report_death or report_reap + callback will try to do the same. utrace_detach + returns -ESRCH when the struct + utrace_engine has already been detached, but is + still a valid pointer because of its reference count. A tracing engine + can use this to safely synchronize its own independent multiple threads + of control with each other and with its event callbacks that detach. + + + + In the same vein, utrace_set_events normally + returns zero; if the target thread was stopped before the call, then + after a successful call, no event callbacks not requested in the new + flags will be made. It fails with -EALREADY if + you try to clear UTRACE_EVENT(DEATH) when the + report_death callback may already have begun, or if + you try to newly set UTRACE_EVENT(DEATH) or + UTRACE_EVENT(QUIESCE) when the target is already + dead or dying. Like utrace_control, it returns + -ESRCH when the report_reap + callback may already have begun, or the thread has already been detached + (including forcible detach on reaping). This lets the tracing engine + know for sure which event callbacks it will or won't see after + utrace_set_events has returned. By checking for + errors, it can know whether to clean up its data structures immediately + or to let its callbacks do the work. + + + + Using <function>utrace_barrier</function> + + When a thread is safely stopped, calling + utrace_control with UTRACE_DETACH + or calling utrace_set_events to disable some events + ensures synchronously that your engine won't get any more of the callbacks + that have been disabled (none at all when detaching). But these can also + be used while the thread is not stopped, when it might be simultaneously + making a callback to your engine. For this situation, these calls return + -EINPROGRESS when it's possible a callback is in + progress. If you are not prepared to have your old callbacks still run, + then you can synchronize to be sure all the old callbacks are finished, + using utrace_barrier. This is necessary if the + kernel module containing your callback code is going to be unloaded. + + + After using UTRACE_DETACH once, further calls to + utrace_control with the same engine pointer will + return -ESRCH. In contrast, after getting + -EINPROGRESS from + utrace_set_events, you can call + utrace_set_events again later and if it returns zero + then know the old callbacks have finished. + + + Unlike all other calls, utrace_barrier (and + utrace_barrier_pid) will accept any engine pointer you + hold a reference on, even if UTRACE_DETACH has already + been used. After any utrace_control or + utrace_set_events call (these do not block), you can + call utrace_barrier to block until callbacks have + finished. This returns -ESRCH only if the engine is + completely detached (finished all callbacks). Otherwise it waits + until the thread is definitely not in the midst of a callback to this + engine and then returns zero, but can return + -ERESTARTSYS if its wait is interrupted. + + + + + + + +utrace core API + + + The utrace API is declared in <linux/utrace.h>. + + +!Iinclude/linux/utrace.h +!Ekernel/utrace.c + + + +Machine State + + + The task_current_syscall function can be used on any + valid struct task_struct at any time, and does + not even require that utrace_attach_task was used at all. + + + + The other ways to access the registers and other machine-dependent state of + a task can only be used on a task that is at a known safe point. The safe + points are all the places where utrace_set_events can + request callbacks (except for the DEATH and + REAP events). So at any event callback, it is safe to + examine current. + + + + One task can examine another only after a callback in the target task that + returns UTRACE_STOP so that task will not return to user + mode after the safe point. This guarantees that the task will not resume + until the same engine uses utrace_control, unless the + task dies suddenly. To examine safely, one must use a pair of calls to + utrace_prepare_examine and + utrace_finish_examine surrounding the calls to + struct user_regset functions or direct examination + of task data structures. utrace_prepare_examine returns + an error if the task is not properly stopped, or is dead. After a + successful examination, the paired utrace_finish_examine + call returns an error if the task ever woke up during the examination. If + so, any data gathered may be scrambled and should be discarded. This means + there was a spurious wake-up (which should not happen), or a sudden death. + + +<structname>struct user_regset</structname> + + + The struct user_regset API + is declared in <linux/regset.h>. + + +!Finclude/linux/regset.h + + + + + <filename>System Call Information</filename> + + + This function is declared in <linux/ptrace.h>. + + +!Elib/syscall.c + + + +<filename>System Call Tracing</filename> + + + The arch API for system call information is declared in + <asm/syscall.h>. + Each of these calls can be used only at system call entry tracing, + or can be used only at system call exit and the subsequent safe points + before returning to user mode. + At system call entry tracing means either during a + report_syscall_entry callback, + or any time after that callback has returned UTRACE_STOP. + + +!Finclude/asm-generic/syscall.h + + + + + +Kernel Internals + + + This chapter covers the interface to the tracing infrastructure + from the core of the kernel and the architecture-specific code. + This is for maintainers of the kernel and arch code, and not relevant + to using the tracing facilities described in preceding chapters. + + +Core Calls In + + + These calls are declared in <linux/tracehook.h>. + The core kernel calls these functions at various important places. + + +!Finclude/linux/tracehook.h + + + +Architecture Calls Out + + + An arch that has done all these things sets + CONFIG_HAVE_ARCH_TRACEHOOK. + This is required to enable the utrace code. + + +<filename><asm/ptrace.h></filename> + + + An arch defines these in <asm/ptrace.h> + if it supports hardware single-step or block-step features. + + +!Finclude/linux/ptrace.h arch_has_single_step arch_has_block_step +!Finclude/linux/ptrace.h user_enable_single_step user_enable_block_step +!Finclude/linux/ptrace.h user_disable_single_step + + + + + <filename><asm/syscall.h></filename> + + + An arch provides <asm/syscall.h> that + defines these as inlines, or declares them as exported functions. + These interfaces are described in . + + + + + + <filename><linux/tracehook.h></filename> + + + An arch must define TIF_NOTIFY_RESUME + and TIF_SYSCALL_TRACE + in its <asm/thread_info.h>. + The arch code must call the following functions, all declared + in <linux/tracehook.h> and + described in : + + + + tracehook_notify_resume + + + tracehook_report_syscall_entry + + + tracehook_report_syscall_exit + + + tracehook_signal_handler + + + + + + + + + + + + diff --git a/fs/proc/array.c b/fs/proc/array.c index fff6572..a67bd83 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -81,6 +81,7 @@ #include #include #include +#include #include #include @@ -192,6 +193,8 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns, cred->uid, cred->euid, cred->suid, cred->fsuid, cred->gid, cred->egid, cred->sgid, cred->fsgid); + task_utrace_proc_status(m, p); + task_lock(p); if (p->files) fdt = files_fdtable(p->files); diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index 4272521..235c1b0 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -99,12 +99,13 @@ #include /* For unlikely. */ #include /* For struct task_struct. */ - +extern void ptrace_notify_stop(struct task_struct *tracee); extern long arch_ptrace(struct task_struct *child, long request, long addr, long data); extern int ptrace_traceme(void); extern int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len); extern int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len); extern int ptrace_attach(struct task_struct *tsk); +extern bool __ptrace_detach(struct task_struct *tracer, struct task_struct *tracee); extern int ptrace_detach(struct task_struct *, unsigned int); extern void ptrace_disable(struct task_struct *); extern int ptrace_check_attach(struct task_struct *task, int kill); diff --git a/include/linux/sched.h b/include/linux/sched.h index ce160d6..66a1ec8 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1339,6 +1339,11 @@ struct task_struct { #endif seccomp_t seccomp; +#ifdef CONFIG_UTRACE + struct utrace *utrace; + unsigned long utrace_flags; +#endif + /* Thread group tracking */ u32 parent_exec_id; u32 self_exec_id; @@ -2030,6 +2035,7 @@ extern int kill_pgrp(struct pid *pid, int sig, int priv); extern int kill_pid(struct pid *pid, int sig, int priv); extern int kill_proc_info(int, struct siginfo *, pid_t); extern int do_notify_parent(struct task_struct *, int); +extern void do_notify_parent_cldstop(struct task_struct *, int); extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent); extern void force_sig(int, struct task_struct *); extern int send_sig(int, struct task_struct *, int); diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h index 10db010..71fa250 100644 --- a/include/linux/tracehook.h +++ b/include/linux/tracehook.h @@ -49,6 +49,7 @@ #include #include #include +#include struct linux_binprm; /** @@ -63,6 +64,8 @@ struct linux_binprm; */ static inline int tracehook_expect_breakpoints(struct task_struct *task) { + if (unlikely(task_utrace_flags(task) & UTRACE_EVENT(SIGNAL_CORE))) + return 1; return (task_ptrace(task) & PT_PTRACED) != 0; } @@ -111,6 +114,9 @@ static inline void ptrace_report_syscall(struct pt_regs *regs) static inline __must_check int tracehook_report_syscall_entry( struct pt_regs *regs) { + if ((task_utrace_flags(current) & UTRACE_EVENT(SYSCALL_ENTRY)) && + utrace_report_syscall_entry(regs)) + return 1; ptrace_report_syscall(regs); return 0; } @@ -134,7 +140,10 @@ static inline __must_check int tracehook_report_syscall_entry( */ static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) { - if (step) { + if (task_utrace_flags(current) & UTRACE_EVENT(SYSCALL_EXIT)) + utrace_report_syscall_exit(regs); + + if (step && (task_ptrace(current) & PT_PTRACED)) { siginfo_t info; user_single_step_siginfo(current, regs, &info); force_sig_info(SIGTRAP, &info, current); @@ -156,7 +165,7 @@ static inline int tracehook_unsafe_exec(struct task_struct *task) { int unsafe = 0; int ptrace = task_ptrace(task); - if (ptrace & PT_PTRACED) { + if (ptrace) { if (ptrace & PT_PTRACE_CAP) unsafe |= LSM_UNSAFE_PTRACE_CAP; else @@ -178,7 +187,7 @@ static inline int tracehook_unsafe_exec(struct task_struct *task) */ static inline struct task_struct *tracehook_tracer_task(struct task_struct *tsk) { - if (task_ptrace(tsk) & PT_PTRACED) + if (task_ptrace(tsk)) return rcu_dereference(tsk->parent); return NULL; } @@ -201,6 +210,8 @@ static inline void tracehook_report_exec(struct linux_binfmt *fmt, struct linux_binprm *bprm, struct pt_regs *regs) { + if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(EXEC))) + utrace_report_exec(fmt, bprm, regs); if (!ptrace_event(PT_TRACE_EXEC, PTRACE_EVENT_EXEC, 0) && unlikely(task_ptrace(current) & PT_PTRACED)) send_sig(SIGTRAP, current, 0); @@ -218,10 +229,37 @@ static inline void tracehook_report_exec(struct linux_binfmt *fmt, */ static inline void tracehook_report_exit(long *exit_code) { + if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(EXIT))) + utrace_report_exit(exit_code); ptrace_event(PT_TRACE_EXIT, PTRACE_EVENT_EXIT, *exit_code); } /** + * tracehook_init_task - task_struct has just been copied + * @task: new &struct task_struct just copied from parent + * + * Called from do_fork() when @task has just been duplicated. + * After this, @task will be passed to tracehook_free_task() + * even if the rest of its setup fails before it is fully created. + */ +static inline void tracehook_init_task(struct task_struct *task) +{ + utrace_init_task(task); +} + +/** + * tracehook_free_task - task_struct is being freed + * @task: dead &struct task_struct being freed + * + * Called from free_task() when @task is no longer in use. + */ +static inline void tracehook_free_task(struct task_struct *task) +{ + if (task_utrace_struct(task)) + utrace_free_task(task); +} + +/** * tracehook_prepare_clone - prepare for new child to be cloned * @clone_flags: %CLONE_* flags from clone/fork/vfork system call * @@ -285,6 +323,8 @@ static inline void tracehook_report_clone(struct pt_regs *regs, unsigned long clone_flags, pid_t pid, struct task_struct *child) { + if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(CLONE))) + utrace_report_clone(clone_flags, child); if (unlikely(task_ptrace(child))) { /* * It doesn't matter who attached/attaching to this @@ -317,6 +357,9 @@ static inline void tracehook_report_clone_complete(int trace, pid_t pid, struct task_struct *child) { + if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(CLONE)) && + (clone_flags & CLONE_VFORK)) + utrace_finish_vfork(current); if (unlikely(trace)) ptrace_event(0, trace, pid); } @@ -351,6 +394,10 @@ static inline void tracehook_report_vfork_done(struct task_struct *child, */ static inline void tracehook_prepare_release_task(struct task_struct *task) { + /* see utrace_add_engine() about this barrier */ + smp_mb(); + if (task_utrace_flags(task)) + utrace_maybe_reap(task, task_utrace_struct(task), true); } /** @@ -365,6 +412,7 @@ static inline void tracehook_prepare_release_task(struct task_struct *task) static inline void tracehook_finish_release_task(struct task_struct *task) { ptrace_release_task(task); + BUG_ON(task->exit_state != EXIT_DEAD); } /** @@ -386,7 +434,9 @@ static inline void tracehook_signal_handler(int sig, siginfo_t *info, const struct k_sigaction *ka, struct pt_regs *regs, int stepping) { - if (stepping) + if (task_utrace_flags(current)) + utrace_signal_handler(current, stepping); + if (stepping && (task_ptrace(current) & PT_PTRACED)) ptrace_notify(SIGTRAP); } @@ -403,6 +453,8 @@ static inline void tracehook_signal_handler(int sig, siginfo_t *info, static inline int tracehook_consider_ignored_signal(struct task_struct *task, int sig) { + if (unlikely(task_utrace_flags(task) & UTRACE_EVENT(SIGNAL_IGN))) + return 1; return (task_ptrace(task) & PT_PTRACED) != 0; } @@ -422,6 +474,9 @@ static inline int tracehook_consider_ignored_signal(struct task_struct *task, static inline int tracehook_consider_fatal_signal(struct task_struct *task, int sig) { + if (unlikely(task_utrace_flags(task) & (UTRACE_EVENT(SIGNAL_TERM) | + UTRACE_EVENT(SIGNAL_CORE)))) + return 1; return (task_ptrace(task) & PT_PTRACED) != 0; } @@ -436,6 +491,8 @@ static inline int tracehook_consider_fatal_signal(struct task_struct *task, */ static inline int tracehook_force_sigpending(void) { + if (unlikely(task_utrace_flags(current))) + return utrace_interrupt_pending(); return 0; } @@ -465,6 +522,8 @@ static inline int tracehook_get_signal(struct task_struct *task, siginfo_t *info, struct k_sigaction *return_ka) { + if (unlikely(task_utrace_flags(task))) + return utrace_get_signal(task, regs, info, return_ka); return 0; } @@ -492,7 +551,9 @@ static inline int tracehook_get_signal(struct task_struct *task, */ static inline int tracehook_notify_jctl(int notify, int why) { - return notify ?: (current->ptrace & PT_PTRACED) ? why : 0; + if (task_utrace_flags(current) & UTRACE_EVENT(JCTL)) + utrace_report_jctl(notify, why); + return notify ?: task_ptrace(current) ? why : 0; } /** @@ -502,6 +563,8 @@ static inline int tracehook_notify_jctl(int notify, int why) */ static inline void tracehook_finish_jctl(void) { + if (task_utrace_flags(current)) + utrace_finish_stop(); } #define DEATH_REAP -1 @@ -524,6 +587,8 @@ static inline void tracehook_finish_jctl(void) static inline int tracehook_notify_death(struct task_struct *task, void **death_cookie, int group_dead) { + *death_cookie = task_utrace_struct(task); + if (task_detached(task)) return task->ptrace ? SIGCHLD : DEATH_REAP; @@ -560,6 +625,15 @@ static inline void tracehook_report_death(struct task_struct *task, int signal, void *death_cookie, int group_dead) { + /* + * If utrace_set_events() was just called to enable + * UTRACE_EVENT(DEATH), then we are obliged to call + * utrace_report_death() and not miss it. utrace_set_events() + * checks @task->exit_state under tasklist_lock to synchronize + * with exit_notify(), the caller. + */ + if (task_utrace_flags(task) & _UTRACE_DEATH_EVENTS) + utrace_report_death(task, death_cookie, group_dead, signal); } #ifdef TIF_NOTIFY_RESUME @@ -589,10 +663,21 @@ static inline void set_notify_resume(struct task_struct *task) * asynchronously, this will be called again before we return to * user mode. * - * Called without locks. + * Called without locks. However, on some machines this may be + * called with interrupts disabled. */ static inline void tracehook_notify_resume(struct pt_regs *regs) { + struct task_struct *task = current; + /* + * Prevent the following store/load from getting ahead of the + * caller which clears TIF_NOTIFY_RESUME. This pairs with the + * implicit mb() before setting TIF_NOTIFY_RESUME in + * set_notify_resume(). + */ + smp_mb(); + if (task_utrace_flags(task)) + utrace_resume(task, regs); } #endif /* TIF_NOTIFY_RESUME */ diff --git a/include/linux/utrace.h b/include/linux/utrace.h new file mode 100644 index 0000000..f251efe --- /dev/null +++ b/include/linux/utrace.h @@ -0,0 +1,692 @@ +/* + * utrace infrastructure interface for debugging user processes + * + * Copyright (C) 2006-2009 Red Hat, Inc. All rights reserved. + * + * This copyrighted material is made available to anyone wishing to use, + * modify, copy, or redistribute it subject to the terms and conditions + * of the GNU General Public License v.2. + * + * Red Hat Author: Roland McGrath. + * + * This interface allows for notification of interesting events in a + * thread. It also mediates access to thread state such as registers. + * Multiple unrelated users can be associated with a single thread. + * We call each of these a tracing engine. + * + * A tracing engine starts by calling utrace_attach_task() or + * utrace_attach_pid() on the chosen thread, passing in a set of hooks + * (&struct utrace_engine_ops), and some associated data. This produces a + * &struct utrace_engine, which is the handle used for all other + * operations. An attached engine has its ops vector, its data, and an + * event mask controlled by utrace_set_events(). + * + * For each event bit that is set, that engine will get the + * appropriate ops->report_*() callback when the event occurs. The + * &struct utrace_engine_ops need not provide callbacks for an event + * unless the engine sets one of the associated event bits. + */ + +#ifndef _LINUX_UTRACE_H +#define _LINUX_UTRACE_H 1 + +#include +#include +#include +#include + +struct linux_binprm; +struct pt_regs; +struct utrace; +struct user_regset; +struct user_regset_view; + +/* + * Event bits passed to utrace_set_events(). + * These appear in &struct task_struct.@utrace_flags + * and &struct utrace_engine.@flags. + */ +enum utrace_events { + _UTRACE_EVENT_QUIESCE, /* Thread is available for examination. */ + _UTRACE_EVENT_REAP, /* Zombie reaped, no more tracing possible. */ + _UTRACE_EVENT_CLONE, /* Successful clone/fork/vfork just done. */ + _UTRACE_EVENT_EXEC, /* Successful execve just completed. */ + _UTRACE_EVENT_EXIT, /* Thread exit in progress. */ + _UTRACE_EVENT_DEATH, /* Thread has died. */ + _UTRACE_EVENT_SYSCALL_ENTRY, /* User entered kernel for system call. */ + _UTRACE_EVENT_SYSCALL_EXIT, /* Returning to user after system call. */ + _UTRACE_EVENT_SIGNAL, /* Signal delivery will run a user handler. */ + _UTRACE_EVENT_SIGNAL_IGN, /* No-op signal to be delivered. */ + _UTRACE_EVENT_SIGNAL_STOP, /* Signal delivery will suspend. */ + _UTRACE_EVENT_SIGNAL_TERM, /* Signal delivery will terminate. */ + _UTRACE_EVENT_SIGNAL_CORE, /* Signal delivery will dump core. */ + _UTRACE_EVENT_JCTL, /* Job control stop or continue completed. */ + _UTRACE_NEVENTS +}; +#define UTRACE_EVENT(type) (1UL << _UTRACE_EVENT_##type) + +/* + * All the kinds of signal events. + * These all use the @report_signal() callback. + */ +#define UTRACE_EVENT_SIGNAL_ALL (UTRACE_EVENT(SIGNAL) \ + | UTRACE_EVENT(SIGNAL_IGN) \ + | UTRACE_EVENT(SIGNAL_STOP) \ + | UTRACE_EVENT(SIGNAL_TERM) \ + | UTRACE_EVENT(SIGNAL_CORE)) +/* + * Both kinds of syscall events; these call the @report_syscall_entry() + * and @report_syscall_exit() callbacks, respectively. + */ +#define UTRACE_EVENT_SYSCALL \ + (UTRACE_EVENT(SYSCALL_ENTRY) | UTRACE_EVENT(SYSCALL_EXIT)) + +/* + * The event reports triggered synchronously by task death. + */ +#define _UTRACE_DEATH_EVENTS (UTRACE_EVENT(DEATH) | UTRACE_EVENT(QUIESCE)) + +/* + * Hooks in call these entry points to the utrace dispatch. + */ +void utrace_free_task(struct task_struct *); +bool utrace_interrupt_pending(void); +void utrace_resume(struct task_struct *, struct pt_regs *); +void utrace_finish_stop(void); +void utrace_maybe_reap(struct task_struct *, struct utrace *, bool); +int utrace_get_signal(struct task_struct *, struct pt_regs *, + siginfo_t *, struct k_sigaction *); +void utrace_report_clone(unsigned long, struct task_struct *); +void utrace_finish_vfork(struct task_struct *); +void utrace_report_exit(long *exit_code); +void utrace_report_death(struct task_struct *, struct utrace *, bool, int); +void utrace_report_jctl(int notify, int type); +void utrace_report_exec(struct linux_binfmt *, struct linux_binprm *, + struct pt_regs *regs); +bool utrace_report_syscall_entry(struct pt_regs *); +void utrace_report_syscall_exit(struct pt_regs *); +void utrace_signal_handler(struct task_struct *, int); + +#ifndef CONFIG_UTRACE + +/* + * uses these accessors to avoid #ifdef CONFIG_UTRACE. + */ +static inline unsigned long task_utrace_flags(struct task_struct *task) +{ + return 0; +} +static inline struct utrace *task_utrace_struct(struct task_struct *task) +{ + return NULL; +} +static inline void utrace_init_task(struct task_struct *child) +{ +} + +static inline void task_utrace_proc_status(struct seq_file *m, + struct task_struct *p) +{ +} + +#else /* CONFIG_UTRACE */ + +static inline unsigned long task_utrace_flags(struct task_struct *task) +{ + return task->utrace_flags; +} + +static inline struct utrace *task_utrace_struct(struct task_struct *task) +{ + struct utrace *utrace; + + /* + * This barrier ensures that any prior load of task->utrace_flags + * is ordered before this load of task->utrace. We use those + * utrace_flags checks in the hot path to decide to call into + * the utrace code. The first attach installs task->utrace before + * setting task->utrace_flags nonzero with implicit barrier in + * between, see utrace_add_engine(). + */ + smp_rmb(); + utrace = task->utrace; + + smp_read_barrier_depends(); /* See utrace_task_alloc(). */ + return utrace; +} + +static inline void utrace_init_task(struct task_struct *task) +{ + task->utrace_flags = 0; + task->utrace = NULL; +} + +void task_utrace_proc_status(struct seq_file *m, struct task_struct *p); + + +/* + * Version number of the API defined in this file. This will change + * whenever a tracing engine's code would need some updates to keep + * working. We maintain this here for the benefit of tracing engine code + * that is developed concurrently with utrace API improvements before they + * are merged into the kernel, making LINUX_VERSION_CODE checks unwieldy. + */ +#define UTRACE_API_VERSION 20091216 + +/** + * enum utrace_resume_action - engine's choice of action for a traced task + * @UTRACE_STOP: Stay quiescent after callbacks. + * @UTRACE_INTERRUPT: Make @report_signal() callback soon. + * @UTRACE_REPORT: Make some callback soon. + * @UTRACE_SINGLESTEP: Resume in user mode for one instruction. + * @UTRACE_BLOCKSTEP: Resume in user mode until next branch. + * @UTRACE_RESUME: Resume normally in user mode. + * @UTRACE_DETACH: Detach my engine (implies %UTRACE_RESUME). + * + * See utrace_control() for detailed descriptions of each action. This is + * encoded in the @action argument and the return value for every callback + * with a &u32 return value. + * + * The order of these is important. When there is more than one engine, + * each supplies its choice and the smallest value prevails. + */ +enum utrace_resume_action { + UTRACE_STOP, + UTRACE_INTERRUPT, + UTRACE_REPORT, + UTRACE_SINGLESTEP, + UTRACE_BLOCKSTEP, + UTRACE_RESUME, + UTRACE_DETACH, + UTRACE_RESUME_MAX +}; +#define UTRACE_RESUME_BITS (ilog2(UTRACE_RESUME_MAX) + 1) +#define UTRACE_RESUME_MASK ((1 << UTRACE_RESUME_BITS) - 1) + +/** + * utrace_resume_action - &enum utrace_resume_action from callback action + * @action: &u32 callback @action argument or return value + * + * This extracts the &enum utrace_resume_action from @action, + * which is the @action argument to a &struct utrace_engine_ops + * callback or the return value from one. + */ +static inline enum utrace_resume_action utrace_resume_action(u32 action) +{ + return action & UTRACE_RESUME_MASK; +} + +/** + * enum utrace_signal_action - disposition of signal + * @UTRACE_SIGNAL_DELIVER: Deliver according to sigaction. + * @UTRACE_SIGNAL_IGN: Ignore the signal. + * @UTRACE_SIGNAL_TERM: Terminate the process. + * @UTRACE_SIGNAL_CORE: Terminate with core dump. + * @UTRACE_SIGNAL_STOP: Deliver as absolute stop. + * @UTRACE_SIGNAL_TSTP: Deliver as job control stop. + * @UTRACE_SIGNAL_REPORT: Reporting before pending signals. + * @UTRACE_SIGNAL_HANDLER: Reporting after signal handler setup. + * + * This is encoded in the @action argument and the return value for + * a @report_signal() callback. It says what will happen to the + * signal described by the &siginfo_t parameter to the callback. + * + * The %UTRACE_SIGNAL_REPORT value is used in an @action argument when + * a tracing report is being made before dequeuing any pending signal. + * If this is immediately after a signal handler has been set up, then + * %UTRACE_SIGNAL_HANDLER is used instead. A @report_signal callback + * that uses %UTRACE_SIGNAL_DELIVER|%UTRACE_SINGLESTEP will ensure + * it sees a %UTRACE_SIGNAL_HANDLER report. + */ +enum utrace_signal_action { + UTRACE_SIGNAL_DELIVER = 0x00, + UTRACE_SIGNAL_IGN = 0x10, + UTRACE_SIGNAL_TERM = 0x20, + UTRACE_SIGNAL_CORE = 0x30, + UTRACE_SIGNAL_STOP = 0x40, + UTRACE_SIGNAL_TSTP = 0x50, + UTRACE_SIGNAL_REPORT = 0x60, + UTRACE_SIGNAL_HANDLER = 0x70 +}; +#define UTRACE_SIGNAL_MASK 0xf0 +#define UTRACE_SIGNAL_HOLD 0x100 /* Flag, push signal back on queue. */ + +/** + * utrace_signal_action - &enum utrace_signal_action from callback action + * @action: @report_signal callback @action argument or return value + * + * This extracts the &enum utrace_signal_action from @action, which + * is the @action argument to a @report_signal callback or the + * return value from one. + */ +static inline enum utrace_signal_action utrace_signal_action(u32 action) +{ + return action & UTRACE_SIGNAL_MASK; +} + +/** + * enum utrace_syscall_action - disposition of system call attempt + * @UTRACE_SYSCALL_RUN: Run the system call. + * @UTRACE_SYSCALL_ABORT: Don't run the system call. + * + * This is encoded in the @action argument and the return value for + * a @report_syscall_entry callback. + */ +enum utrace_syscall_action { + UTRACE_SYSCALL_RUN = 0x00, + UTRACE_SYSCALL_ABORT = 0x10 +}; +#define UTRACE_SYSCALL_MASK 0xf0 +#define UTRACE_SYSCALL_RESUMED 0x100 /* Flag, report_syscall_entry() repeats */ + +/** + * utrace_syscall_action - &enum utrace_syscall_action from callback action + * @action: @report_syscall_entry callback @action or return value + * + * This extracts the &enum utrace_syscall_action from @action, which + * is the @action argument to a @report_syscall_entry callback or the + * return value from one. + */ +static inline enum utrace_syscall_action utrace_syscall_action(u32 action) +{ + return action & UTRACE_SYSCALL_MASK; +} + +/* + * Flags for utrace_attach_task() and utrace_attach_pid(). + */ +#define UTRACE_ATTACH_MATCH_OPS 0x0001 /* Match engines on ops. */ +#define UTRACE_ATTACH_MATCH_DATA 0x0002 /* Match engines on data. */ +#define UTRACE_ATTACH_MATCH_MASK 0x000f +#define UTRACE_ATTACH_CREATE 0x0010 /* Attach a new engine. */ +#define UTRACE_ATTACH_EXCLUSIVE 0x0020 /* Refuse if existing match. */ + +/** + * struct utrace_engine - per-engine structure + * @ops: &struct utrace_engine_ops pointer passed to utrace_attach_task() + * @data: engine-private &void * passed to utrace_attach_task() + * @flags: event mask set by utrace_set_events() plus internal flag bits + * + * The task itself never has to worry about engines detaching while + * it's doing event callbacks. These structures are removed from the + * task's active list only when it's stopped, or by the task itself. + * + * utrace_engine_get() and utrace_engine_put() maintain a reference count. + * When it drops to zero, the structure is freed. One reference is held + * implicitly while the engine is attached to its task. + */ +struct utrace_engine { +/* private: */ + struct kref kref; + void (*release)(void *); + struct list_head entry; + +/* public: */ + const struct utrace_engine_ops *ops; + void *data; + + unsigned long flags; +}; + +/** + * utrace_engine_get - acquire a reference on a &struct utrace_engine + * @engine: &struct utrace_engine pointer + * + * You must hold a reference on @engine, and you get another. + */ +static inline void utrace_engine_get(struct utrace_engine *engine) +{ + kref_get(&engine->kref); +} + +void __utrace_engine_release(struct kref *); + +/** + * utrace_engine_put - release a reference on a &struct utrace_engine + * @engine: &struct utrace_engine pointer + * + * You must hold a reference on @engine, and you lose that reference. + * If it was the last one, @engine becomes an invalid pointer. + */ +static inline void utrace_engine_put(struct utrace_engine *engine) +{ + kref_put(&engine->kref, __utrace_engine_release); +} + +/** + * struct utrace_engine_ops - tracing engine callbacks + * + * Each @report_*() callback corresponds to an %UTRACE_EVENT(*) bit. + * utrace_set_events() calls on @engine choose which callbacks will + * be made to @engine from @task. + * + * Most callbacks take an @action argument, giving the resume action + * chosen by other tracing engines. All callbacks take an @engine + * argument. The @report_reap callback takes a @task argument that + * might or might not be @current. All other @report_* callbacks + * report an event in the @current task. + * + * For some calls, @action also includes bits specific to that event + * and utrace_resume_action() is used to extract the resume action. + * This shows what would happen if @engine wasn't there, or will if + * the callback's return value uses %UTRACE_RESUME. This always + * starts as %UTRACE_RESUME when no other tracing is being done on + * this task. + * + * All return values contain &enum utrace_resume_action bits. For + * some calls, other bits specific to that kind of event are added to + * the resume action bits with OR. These are the same bits used in + * the @action argument. The resume action returned by a callback + * does not override previous engines' choices, it only says what + * @engine wants done. What @current actually does is the action that's + * most constrained among the choices made by all attached engines. + * See utrace_control() for more information on the actions. + * + * When %UTRACE_STOP is used in @report_syscall_entry, then @current + * stops before attempting the system call. In this case, another + * @report_syscall_entry callback will follow after @current resumes if + * %UTRACE_REPORT or %UTRACE_INTERRUPT was returned by some callback + * or passed to utrace_control(). In a second or later callback, + * %UTRACE_SYSCALL_RESUMED is set in the @action argument to indicate + * a repeat callback still waiting to attempt the same system call + * invocation. This repeat callback gives each engine an opportunity + * to reexamine registers another engine might have changed while + * @current was held in %UTRACE_STOP. + * + * In other cases, the resume action does not take effect until @current + * is ready to check for signals and return to user mode. If there + * are more callbacks to be made, the last round of calls determines + * the final action. A @report_quiesce callback with @event zero, or + * a @report_signal callback, will always be the last one made before + * @current resumes. Only %UTRACE_STOP is "sticky"--if @engine returned + * %UTRACE_STOP then @current stays stopped unless @engine returns + * different from a following callback. + * + * The report_death() and report_reap() callbacks do not take @action + * arguments, and only %UTRACE_DETACH is meaningful in the return value + * from a report_death() callback. None of the resume actions applies + * to a dead thread. + * + * All @report_*() hooks are called with no locks held, in a generally + * safe environment when we will be returning to user mode soon (or just + * entered the kernel). It is fine to block for memory allocation and + * the like, but all hooks are asynchronous and must not block on + * external events! If you want the thread to block, use %UTRACE_STOP + * in your hook's return value; then later wake it up with utrace_control(). + * + * @report_quiesce: + * Requested by %UTRACE_EVENT(%QUIESCE). + * This does not indicate any event, but just that @current is in a + * safe place for examination. This call is made before each specific + * event callback, except for @report_reap. The @event argument gives + * the %UTRACE_EVENT(@which) value for the event occurring. This + * callback might be made for events @engine has not requested, if + * some other engine is tracing the event; calling utrace_set_events() + * call here can request the immediate callback for this occurrence of + * @event. @event is zero when there is no other event, @current is + * now ready to check for signals and return to user mode, and some + * engine has used %UTRACE_REPORT or %UTRACE_INTERRUPT to request this + * callback. For this case, if @report_signal is not %NULL, the + * @report_quiesce callback may be replaced with a @report_signal + * callback passing %UTRACE_SIGNAL_REPORT in its @action argument, + * whenever @current is entering the signal-check path anyway. + * + * @report_signal: + * Requested by %UTRACE_EVENT(%SIGNAL_*) or %UTRACE_EVENT(%QUIESCE). + * Use utrace_signal_action() and utrace_resume_action() on @action. + * The signal action is %UTRACE_SIGNAL_REPORT when some engine has + * used %UTRACE_REPORT or %UTRACE_INTERRUPT; the callback can choose + * to stop or to deliver an artificial signal, before pending signals. + * It's %UTRACE_SIGNAL_HANDLER instead when signal handler setup just + * finished (after a previous %UTRACE_SIGNAL_DELIVER return); this + * serves in lieu of any %UTRACE_SIGNAL_REPORT callback requested by + * %UTRACE_REPORT or %UTRACE_INTERRUPT, and is also implicitly + * requested by %UTRACE_SINGLESTEP or %UTRACE_BLOCKSTEP into the + * signal delivery. The other signal actions indicate a signal about + * to be delivered; the previous engine's return value sets the signal + * action seen by the the following engine's callback. The @info data + * can be changed at will, including @info->si_signo. The settings in + * @return_ka determines what %UTRACE_SIGNAL_DELIVER does. @orig_ka + * is what was in force before other tracing engines intervened, and + * it's %NULL when this report began as %UTRACE_SIGNAL_REPORT or + * %UTRACE_SIGNAL_HANDLER. For a report without a new signal, @info + * is left uninitialized and must be set completely by an engine that + * chooses to deliver a signal; if there was a previous @report_signal + * callback ending in %UTRACE_STOP and it was just resumed using + * %UTRACE_REPORT or %UTRACE_INTERRUPT, then @info is left unchanged + * from the previous callback. In this way, the original signal can + * be left in @info while returning %UTRACE_STOP|%UTRACE_SIGNAL_IGN + * and then found again when resuming with %UTRACE_INTERRUPT. + * The %UTRACE_SIGNAL_HOLD flag bit can be OR'd into the return value, + * and might be in @action if the previous engine returned it. This + * flag asks that the signal in @info be pushed back on @current's queue + * so that it will be seen again after whatever action is taken now. + * + * @report_clone: + * Requested by %UTRACE_EVENT(%CLONE). + * Event reported for parent, before the new task @child might run. + * @clone_flags gives the flags used in the clone system call, or + * equivalent flags for a fork() or vfork() system call. This + * function can use utrace_attach_task() on @child. Then passing + * %UTRACE_STOP to utrace_control() on @child here keeps the child + * stopped before it ever runs in user mode, %UTRACE_REPORT or + * %UTRACE_INTERRUPT ensures a callback from @child before it + * starts in user mode. + * + * @report_jctl: + * Requested by %UTRACE_EVENT(%JCTL). + * Job control event; @type is %CLD_STOPPED or %CLD_CONTINUED, + * indicating whether we are stopping or resuming now. If @notify + * is nonzero, @current is the last thread to stop and so will send + * %SIGCHLD to its parent after this callback; @notify reflects + * what the parent's %SIGCHLD has in @si_code, which can sometimes + * be %CLD_STOPPED even when @type is %CLD_CONTINUED. + * + * @report_exec: + * Requested by %UTRACE_EVENT(%EXEC). + * An execve system call has succeeded and the new program is about to + * start running. The initial user register state is handy to be tweaked + * directly in @regs. @fmt and @bprm gives the details of this exec. + * + * @report_syscall_entry: + * Requested by %UTRACE_EVENT(%SYSCALL_ENTRY). + * Thread has entered the kernel to request a system call. + * The user register state is handy to be tweaked directly in @regs. + * The @action argument contains an &enum utrace_syscall_action, + * use utrace_syscall_action() to extract it. The return value + * overrides the last engine's action for the system call. + * If the final action is %UTRACE_SYSCALL_ABORT, no system call + * is made. The details of the system call being attempted can + * be fetched here with syscall_get_nr() and syscall_get_arguments(). + * The parameter registers can be changed with syscall_set_arguments(). + * See above about the %UTRACE_SYSCALL_RESUMED flag in @action. + * Use %UTRACE_REPORT in the return value to guarantee you get + * another callback (with %UTRACE_SYSCALL_RESUMED flag) in case + * @current stops with %UTRACE_STOP before attempting the system call. + * + * @report_syscall_exit: + * Requested by %UTRACE_EVENT(%SYSCALL_EXIT). + * Thread is about to leave the kernel after a system call request. + * The user register state is handy to be tweaked directly in @regs. + * The results of the system call attempt can be examined here using + * syscall_get_error() and syscall_get_return_value(). It is safe + * here to call syscall_set_return_value() or syscall_rollback(). + * + * @report_exit: + * Requested by %UTRACE_EVENT(%EXIT). + * Thread is exiting and cannot be prevented from doing so, + * but all its state is still live. The @code value will be + * the wait result seen by the parent, and can be changed by + * this engine or others. The @orig_code value is the real + * status, not changed by any tracing engine. Returning %UTRACE_STOP + * here keeps @current stopped before it cleans up its state and dies, + * so it can be examined by other processes. When @current is allowed + * to run, it will die and get to the @report_death callback. + * + * @report_death: + * Requested by %UTRACE_EVENT(%DEATH). + * Thread is really dead now. It might be reaped by its parent at + * any time, or self-reap immediately. Though the actual reaping + * may happen in parallel, a report_reap() callback will always be + * ordered after a report_death() callback. + * + * @report_reap: + * Requested by %UTRACE_EVENT(%REAP). + * Called when someone reaps the dead task (parent, init, or self). + * This means the parent called wait, or else this was a detached + * thread or a process whose parent ignores SIGCHLD. + * No more callbacks are made after this one. + * The engine is always detached. + * There is nothing more a tracing engine can do about this thread. + * After this callback, the @engine pointer will become invalid. + * The @task pointer may become invalid if get_task_struct() hasn't + * been used to keep it alive. + * An engine should always request this callback if it stores the + * @engine pointer or stores any pointer in @engine->data, so it + * can clean up its data structures. + * Unlike other callbacks, this can be called from the parent's context + * rather than from the traced thread itself--it must not delay the + * parent by blocking. + * + * @release: + * If not %NULL, this is called after the last utrace_engine_put() + * call for a &struct utrace_engine, which could be implicit after + * a %UTRACE_DETACH return from another callback. Its argument is + * the engine's @data member. + */ +struct utrace_engine_ops { + u32 (*report_quiesce)(u32 action, struct utrace_engine *engine, + unsigned long event); + u32 (*report_signal)(u32 action, struct utrace_engine *engine, + struct pt_regs *regs, + siginfo_t *info, + const struct k_sigaction *orig_ka, + struct k_sigaction *return_ka); + u32 (*report_clone)(u32 action, struct utrace_engine *engine, + unsigned long clone_flags, + struct task_struct *child); + u32 (*report_jctl)(u32 action, struct utrace_engine *engine, + int type, int notify); + u32 (*report_exec)(u32 action, struct utrace_engine *engine, + const struct linux_binfmt *fmt, + const struct linux_binprm *bprm, + struct pt_regs *regs); + u32 (*report_syscall_entry)(u32 action, struct utrace_engine *engine, + struct pt_regs *regs); + u32 (*report_syscall_exit)(u32 action, struct utrace_engine *engine, + struct pt_regs *regs); + u32 (*report_exit)(u32 action, struct utrace_engine *engine, + long orig_code, long *code); + u32 (*report_death)(struct utrace_engine *engine, + bool group_dead, int signal); + void (*report_reap)(struct utrace_engine *engine, + struct task_struct *task); + void (*release)(void *data); +}; + +/** + * struct utrace_examiner - private state for using utrace_prepare_examine() + * + * The members of &struct utrace_examiner are private to the implementation. + * This data type holds the state from a call to utrace_prepare_examine() + * to be used by a call to utrace_finish_examine(). + */ +struct utrace_examiner { +/* private: */ + long state; + unsigned long ncsw; +}; + +/* + * These are the exported entry points for tracing engines to use. + * See kernel/utrace.c for their kerneldoc comments with interface details. + */ +struct utrace_engine *utrace_attach_task(struct task_struct *, int, + const struct utrace_engine_ops *, + void *); +struct utrace_engine *utrace_attach_pid(struct pid *, int, + const struct utrace_engine_ops *, + void *); +int __must_check utrace_control(struct task_struct *, + struct utrace_engine *, + enum utrace_resume_action); +int __must_check utrace_set_events(struct task_struct *, + struct utrace_engine *, + unsigned long eventmask); +int __must_check utrace_barrier(struct task_struct *, + struct utrace_engine *); +int __must_check utrace_prepare_examine(struct task_struct *, + struct utrace_engine *, + struct utrace_examiner *); +int __must_check utrace_finish_examine(struct task_struct *, + struct utrace_engine *, + struct utrace_examiner *); + +/** + * utrace_control_pid - control a thread being traced by a tracing engine + * @pid: thread to affect + * @engine: attached engine to affect + * @action: &enum utrace_resume_action for thread to do + * + * This is the same as utrace_control(), but takes a &struct pid + * pointer rather than a &struct task_struct pointer. The caller must + * hold a ref on @pid, but does not need to worry about the task + * staying valid. If it's been reaped so that @pid points nowhere, + * then this call returns -%ESRCH. + */ +static inline __must_check int utrace_control_pid( + struct pid *pid, struct utrace_engine *engine, + enum utrace_resume_action action) +{ + /* + * We don't bother with rcu_read_lock() here to protect the + * task_struct pointer, because utrace_control will return + * -ESRCH without looking at that pointer if the engine is + * already detached. A task_struct pointer can't die before + * all the engines are detached in release_task() first. + */ + struct task_struct *task = pid_task(pid, PIDTYPE_PID); + return unlikely(!task) ? -ESRCH : utrace_control(task, engine, action); +} + +/** + * utrace_set_events_pid - choose which event reports a tracing engine gets + * @pid: thread to affect + * @engine: attached engine to affect + * @eventmask: new event mask + * + * This is the same as utrace_set_events(), but takes a &struct pid + * pointer rather than a &struct task_struct pointer. The caller must + * hold a ref on @pid, but does not need to worry about the task + * staying valid. If it's been reaped so that @pid points nowhere, + * then this call returns -%ESRCH. + */ +static inline __must_check int utrace_set_events_pid( + struct pid *pid, struct utrace_engine *engine, unsigned long eventmask) +{ + struct task_struct *task = pid_task(pid, PIDTYPE_PID); + return unlikely(!task) ? -ESRCH : + utrace_set_events(task, engine, eventmask); +} + +/** + * utrace_barrier_pid - synchronize with simultaneous tracing callbacks + * @pid: thread to affect + * @engine: engine to affect (can be detached) + * + * This is the same as utrace_barrier(), but takes a &struct pid + * pointer rather than a &struct task_struct pointer. The caller must + * hold a ref on @pid, but does not need to worry about the task + * staying valid. If it's been reaped so that @pid points nowhere, + * then this call returns -%ESRCH. + */ +static inline __must_check int utrace_barrier_pid(struct pid *pid, + struct utrace_engine *engine) +{ + struct task_struct *task = pid_task(pid, PIDTYPE_PID); + return unlikely(!task) ? -ESRCH : utrace_barrier(task, engine); +} + +#endif /* CONFIG_UTRACE */ + +#endif /* linux/utrace.h */ diff --git a/init/Kconfig b/init/Kconfig index 2de5b1c..a283086 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -332,6 +332,15 @@ config AUDIT_TREE depends on AUDITSYSCALL select FSNOTIFY +config UTRACE + bool "Infrastructure for tracing and debugging user processes" + depends on EXPERIMENTAL + depends on HAVE_ARCH_TRACEHOOK + help + Enable the utrace process tracing interface. This is an internal + kernel interface exported to kernel modules, to track events in + user threads, extract and change user thread state. + menu "RCU Subsystem" choice diff --git a/kernel/Makefile b/kernel/Makefile index 0b72d1a..b09c9a5 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -70,6 +70,8 @@ obj-$(CONFIG_IKCONFIG) += configs.o obj-$(CONFIG_RESOURCE_COUNTERS) += res_counter.o obj-$(CONFIG_SMP) += stop_machine.o obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o +obj-$(CONFIG_UTRACE) += utrace.o +obj-$(CONFIG_UTRACE) += ptrace-utrace.o obj-$(CONFIG_AUDIT) += audit.o auditfilter.o obj-$(CONFIG_AUDITSYSCALL) += auditsc.o obj-$(CONFIG_AUDIT_WATCH) += audit_watch.o diff --git a/kernel/fork.c b/kernel/fork.c index 98b4508..3ceff6f 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -161,6 +161,7 @@ void free_task(struct task_struct *tsk) free_thread_info(tsk->stack); rt_mutex_debug_task_free(tsk); ftrace_graph_exit_task(tsk); + tracehook_free_task(tsk); free_task_struct(tsk); } EXPORT_SYMBOL(free_task); @@ -1008,6 +1009,8 @@ static struct task_struct *copy_process(unsigned long clone_flags, if (!p) goto fork_out; + tracehook_init_task(p); + ftrace_graph_init_task(p); rt_mutex_init_task(p); diff --git a/kernel/ptrace-utrace.c b/kernel/ptrace-utrace.c new file mode 100644 index 0000000..1a8ba5e --- /dev/null +++ b/kernel/ptrace-utrace.c @@ -0,0 +1,1125 @@ +/* + * linux/kernel/ptrace.c + * + * (C) Copyright 1999 Linus Torvalds + * + * Common interfaces for "ptrace()" which we do not want + * to continually duplicate across every architecture. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* + * ptrace a task: make the debugger its new parent and + * move it to the ptrace list. + * + * Must be called with the tasklist lock write-held. + */ +void __ptrace_link(struct task_struct *child, struct task_struct *new_parent) +{ + BUG_ON(!list_empty(&child->ptrace_entry)); + list_add(&child->ptrace_entry, &new_parent->ptraced); + child->parent = new_parent; +} + +/* + * unptrace a task: move it back to its original parent and + * remove it from the ptrace list. + * + * Must be called with the tasklist lock write-held. + */ +void __ptrace_unlink(struct task_struct *child) +{ + BUG_ON(!child->ptrace); + + child->ptrace = 0; + child->parent = child->real_parent; + list_del_init(&child->ptrace_entry); +} + +struct ptrace_context { + int options; + + int signr; + siginfo_t *siginfo; + + int stop_code; + unsigned long eventmsg; + + enum utrace_resume_action resume; +}; + +#define PT_UTRACED 0x00001000 + +#define PTRACE_O_SYSEMU 0x100 + +#define PTRACE_EVENT_SYSCALL (1 << 16) +#define PTRACE_EVENT_SIGTRAP (2 << 16) +#define PTRACE_EVENT_SIGNAL (3 << 16) +/* events visible to user-space */ +#define PTRACE_EVENT_MASK 0xFFFF + +static inline bool ptrace_event_pending(struct ptrace_context *ctx) +{ + return ctx->stop_code != 0; +} + +static inline int get_stop_event(struct ptrace_context *ctx) +{ + return ctx->stop_code >> 8; +} + +static inline void set_stop_code(struct ptrace_context *ctx, int event) +{ + ctx->stop_code = (event << 8) | SIGTRAP; +} + +static inline struct ptrace_context * +ptrace_context(struct utrace_engine *engine) +{ + return engine->data; +} + +static const struct utrace_engine_ops ptrace_utrace_ops; /* forward decl */ + +static struct utrace_engine *ptrace_lookup_engine(struct task_struct *tracee) +{ + return utrace_attach_task(tracee, UTRACE_ATTACH_MATCH_OPS, + &ptrace_utrace_ops, NULL); +} + +static struct utrace_engine * +ptrace_reuse_engine(struct task_struct *tracee) +{ + struct utrace_engine *engine; + struct ptrace_context *ctx; + int err = -EPERM; + + engine = ptrace_lookup_engine(tracee); + if (IS_ERR(engine)) + return engine; + + ctx = ptrace_context(engine); + if (unlikely(ctx->resume == UTRACE_DETACH)) { + /* + * Try to reuse this self-detaching engine. + * The only caller which can hit this case is ptrace_attach(), + * it holds ->cred_guard_mutex. + */ + ctx->options = 0; + ctx->eventmsg = 0; + + /* make sure we don't get unwanted reports */ + err = utrace_set_events(tracee, engine, UTRACE_EVENT(QUIESCE)); + if (!err || err == -EINPROGRESS) { + ctx->resume = UTRACE_RESUME; + /* synchronize with ptrace_report_signal() */ + err = utrace_barrier(tracee, engine); + } + WARN_ON(!err != (engine->ops == &ptrace_utrace_ops)); + + if (!err) + return engine; + } + + utrace_engine_put(engine); + return ERR_PTR(err); +} + +static struct utrace_engine * +ptrace_attach_engine(struct task_struct *tracee) +{ + struct utrace_engine *engine; + struct ptrace_context *ctx; + + if (unlikely(task_utrace_flags(tracee))) { + engine = ptrace_reuse_engine(tracee); + if (!IS_ERR(engine) || IS_ERR(engine) == -EPERM) + return engine; + } + + ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); + if (unlikely(!ctx)) + return ERR_PTR(-ENOMEM); + + ctx->resume = UTRACE_RESUME; + + engine = utrace_attach_task(tracee, UTRACE_ATTACH_CREATE | + UTRACE_ATTACH_EXCLUSIVE | + UTRACE_ATTACH_MATCH_OPS, + &ptrace_utrace_ops, ctx); + if (unlikely(IS_ERR(engine))) { + if (engine != ERR_PTR(-ESRCH) && + engine != ERR_PTR(-ERESTARTNOINTR)) + engine = ERR_PTR(-EPERM); + kfree(ctx); + } + + return engine; +} + +static inline int ptrace_set_events(struct task_struct *target, + struct utrace_engine *engine, + unsigned long options) +{ + struct ptrace_context *ctx = ptrace_context(engine); + /* + * We need QUIESCE for resume handling, CLONE to check + * for CLONE_PTRACE, other events are always reported. + */ + unsigned long events = UTRACE_EVENT(QUIESCE) | UTRACE_EVENT(CLONE) | + UTRACE_EVENT(EXEC) | UTRACE_EVENT_SIGNAL_ALL; + + ctx->options = options; + if (options & PTRACE_O_TRACEEXIT) + events |= UTRACE_EVENT(EXIT); + + return utrace_set_events(target, engine, events); +} + +/* + * Attach a utrace engine for ptrace and set up its event mask. + * Returns error code or 0 on success. + */ +static int ptrace_attach_task(struct task_struct *tracee, int options) +{ + struct utrace_engine *engine; + int err; + + engine = ptrace_attach_engine(tracee); + if (IS_ERR(engine)) + return PTR_ERR(engine); + /* + * It can fail only if the tracee is dead, the caller + * must notice this before setting PT_UTRACED. + */ + err = ptrace_set_events(tracee, engine, options); + WARN_ON(err && !tracee->exit_state); + utrace_engine_put(engine); + return 0; +} + +static int ptrace_wake_up(struct task_struct *tracee, + struct utrace_engine *engine, + enum utrace_resume_action action, + bool force_wakeup) +{ + if (force_wakeup) { + unsigned long flags; + /* + * Preserve the compatibility bug. Historically ptrace + * wakes up the tracee even if it should not. Clear + * SIGNAL_STOP_STOPPED for utrace_wakeup(). + */ + if (lock_task_sighand(tracee, &flags)) { + tracee->signal->flags &= ~SIGNAL_STOP_STOPPED; + unlock_task_sighand(tracee, &flags); + } + } + + if (action != UTRACE_REPORT) + ptrace_context(engine)->stop_code = 0; + + return utrace_control(tracee, engine, action); +} + +static void ptrace_detach_task(struct task_struct *tracee, int sig) +{ + /* + * If true, the caller is PTRACE_DETACH, otherwise + * the tracer detaches implicitly during exit. + */ + bool voluntary = (sig >= 0); + struct utrace_engine *engine = ptrace_lookup_engine(tracee); + enum utrace_resume_action action = UTRACE_DETACH; + + if (unlikely(IS_ERR(engine))) + return; + + if (sig) { + struct ptrace_context *ctx = ptrace_context(engine); + + switch (get_stop_event(ctx)) { + case PTRACE_EVENT_SYSCALL: + if (voluntary) + send_sig_info(sig, SEND_SIG_PRIV, tracee); + break; + + case PTRACE_EVENT_SIGNAL: + if (voluntary) + ctx->signr = sig; + ctx->resume = UTRACE_DETACH; + action = UTRACE_RESUME; + break; + } + } + + ptrace_wake_up(tracee, engine, action, voluntary); + utrace_engine_put(engine); +} + +static void ptrace_abort_attach(struct task_struct *tracee) +{ + ptrace_detach_task(tracee, 0); +} + +static u32 ptrace_report_exit(u32 action, struct utrace_engine *engine, + long orig_code, long *code) +{ + struct ptrace_context *ctx = ptrace_context(engine); + + WARN_ON(ptrace_event_pending(ctx) && + !signal_group_exit(current->signal)); + + set_stop_code(ctx, PTRACE_EVENT_EXIT); + ctx->eventmsg = *code; + + return UTRACE_STOP; +} + +static void ptrace_clone_attach(struct task_struct *child, + int options) +{ + struct task_struct *parent = current; + struct task_struct *tracer; + bool abort = true; + + if (unlikely(ptrace_attach_task(child, options))) { + WARN_ON(1); + return; + } + + write_lock_irq(&tasklist_lock); + tracer = parent->parent; + if (!(tracer->flags & PF_EXITING) && parent->ptrace) { + child->ptrace = parent->ptrace; + __ptrace_link(child, tracer); + abort = false; + } + write_unlock_irq(&tasklist_lock); + if (unlikely(abort)) { + ptrace_abort_attach(child); + return; + } + + sigaddset(&child->pending.signal, SIGSTOP); + set_tsk_thread_flag(child, TIF_SIGPENDING); +} + +static u32 ptrace_report_clone(u32 action, struct utrace_engine *engine, + unsigned long clone_flags, + struct task_struct *child) +{ + struct ptrace_context *ctx = ptrace_context(engine); + int event = 0; + + WARN_ON(ptrace_event_pending(ctx)); + + if (clone_flags & CLONE_UNTRACED) { + /* no events reported */ + } else if (clone_flags & CLONE_VFORK) { + if (ctx->options & PTRACE_O_TRACEVFORK) + event = PTRACE_EVENT_VFORK; + else if (ctx->options & PTRACE_O_TRACEVFORKDONE) + event = PTRACE_EVENT_VFORK_DONE; + } else if ((clone_flags & CSIGNAL) != SIGCHLD) { + if (ctx->options & PTRACE_O_TRACECLONE) + event = PTRACE_EVENT_CLONE; + } else if (ctx->options & PTRACE_O_TRACEFORK) { + event = PTRACE_EVENT_FORK; + } + /* + * Any of these reports implies auto-attaching the new child. + * So does CLONE_PTRACE, even with no event to report. + */ + if ((event && event != PTRACE_EVENT_VFORK_DONE) || + (clone_flags & CLONE_PTRACE)) + ptrace_clone_attach(child, ctx->options); + + if (!event) + return UTRACE_RESUME; + + set_stop_code(ctx, event); + ctx->eventmsg = child->pid; + /* + * We shouldn't stop now, inside the do_fork() path. + * We will stop later, before return to user-mode. + */ + if (event == PTRACE_EVENT_VFORK_DONE) + return UTRACE_REPORT; + else + return UTRACE_STOP; +} + +static inline void set_syscall_code(struct ptrace_context *ctx) +{ + set_stop_code(ctx, PTRACE_EVENT_SYSCALL); + if (ctx->options & PTRACE_O_TRACESYSGOOD) + ctx->stop_code |= 0x80; +} + +static u32 ptrace_report_syscall_entry(u32 action, struct utrace_engine *engine, + struct pt_regs *regs) +{ + struct ptrace_context *ctx = ptrace_context(engine); + + if (action & UTRACE_SYSCALL_RESUMED) { + /* + * We already reported the first time. + * Nothing more to do now. + */ + if (unlikely(ctx->options & PTRACE_O_SYSEMU)) + return UTRACE_SYSCALL_ABORT | UTRACE_REPORT; + return utrace_syscall_action(action) | UTRACE_RESUME; + } + + WARN_ON(ptrace_event_pending(ctx)); + + set_syscall_code(ctx); + + if (unlikely(ctx->options & PTRACE_O_SYSEMU)) + return UTRACE_SYSCALL_ABORT | UTRACE_REPORT; + /* + * Stop now to report. We will get another callback after + * we resume, with the UTRACE_SYSCALL_RESUMED flag set. + */ + return UTRACE_SYSCALL_RUN | UTRACE_STOP; +} + +static u32 ptrace_report_syscall_exit(u32 action, struct utrace_engine *engine, + struct pt_regs *regs) +{ + struct ptrace_context *ctx = ptrace_context(engine); + + if (ptrace_event_pending(ctx)) + return UTRACE_STOP; + + if (ctx->resume != UTRACE_RESUME) { + WARN_ON(ctx->resume != UTRACE_BLOCKSTEP && + ctx->resume != UTRACE_SINGLESTEP); + ctx->resume = UTRACE_RESUME; + + ctx->signr = SIGTRAP; + return UTRACE_INTERRUPT; + } + + set_syscall_code(ctx); + return UTRACE_STOP; +} + +static u32 ptrace_report_exec(u32 action, struct utrace_engine *engine, + const struct linux_binfmt *fmt, + const struct linux_binprm *bprm, + struct pt_regs *regs) +{ + struct ptrace_context *ctx = ptrace_context(engine); + + WARN_ON(ptrace_event_pending(ctx)); + + if (!(ctx->options & PTRACE_O_TRACEEXEC)) { + /* + * Old-fashioned ptrace'd exec just posts a plain signal. + */ + send_sig(SIGTRAP, current, 0); + return UTRACE_RESUME; + } + + set_stop_code(ctx, PTRACE_EVENT_EXEC); + return UTRACE_STOP; +} + +static enum utrace_signal_action resume_signal(struct ptrace_context *ctx, + struct k_sigaction *return_ka) +{ + siginfo_t *info = ctx->siginfo; + int signr = ctx->signr; + + ctx->siginfo = NULL; + ctx->signr = 0; + + /* Did the debugger cancel the sig? */ + if (!signr) + return UTRACE_SIGNAL_IGN; + /* + * Update the siginfo structure if the signal has changed. + * If the debugger wanted something specific in the siginfo + * then it should have updated *info via PTRACE_SETSIGINFO. + */ + if (info->si_signo != signr) { + info->si_signo = signr; + info->si_errno = 0; + info->si_code = SI_USER; + info->si_pid = task_pid_vnr(current->parent); + info->si_uid = task_uid(current->parent); + } + + /* If the (new) signal is now blocked, requeue it. */ + if (sigismember(¤t->blocked, signr)) { + send_sig_info(signr, info, current); + return UTRACE_SIGNAL_IGN; + } + + spin_lock_irq(¤t->sighand->siglock); + *return_ka = current->sighand->action[signr - 1]; + spin_unlock_irq(¤t->sighand->siglock); + + return UTRACE_SIGNAL_DELIVER; +} + +static u32 ptrace_report_signal(u32 action, struct utrace_engine *engine, + struct pt_regs *regs, + siginfo_t *info, + const struct k_sigaction *orig_ka, + struct k_sigaction *return_ka) +{ + struct ptrace_context *ctx = ptrace_context(engine); + enum utrace_resume_action resume = ctx->resume; + + if (ptrace_event_pending(ctx)) { + action = utrace_signal_action(action); + WARN_ON(action != UTRACE_SIGNAL_REPORT); + return action | UTRACE_STOP; + } + + switch (utrace_signal_action(action)) { + case UTRACE_SIGNAL_HANDLER: + if (WARN_ON(ctx->siginfo)) + ctx->siginfo = NULL; + + if (resume != UTRACE_RESUME) { + WARN_ON(resume != UTRACE_BLOCKSTEP && + resume != UTRACE_SINGLESTEP); + + set_stop_code(ctx, PTRACE_EVENT_SIGTRAP); + return UTRACE_STOP | UTRACE_SIGNAL_IGN; + } + + case UTRACE_SIGNAL_REPORT: + if (!ctx->siginfo) { + if (ctx->signr) { + /* set by ptrace_resume(SYSCALL_EXIT) */ + WARN_ON(ctx->signr != SIGTRAP); + user_single_step_siginfo(current, regs, info); + force_sig_info(SIGTRAP, info, current); + } + + return resume | UTRACE_SIGNAL_IGN; + } + + if (WARN_ON(ctx->siginfo != info)) + return resume | UTRACE_SIGNAL_IGN; + + return resume | resume_signal(ctx, return_ka); + + default: + break; + } + + WARN_ON(ctx->siginfo); + ctx->siginfo = info; + /* + * ctx->siginfo points to the caller's stack. + * Make sure the subsequent UTRACE_SIGNAL_REPORT clears + * ->siginfo before return from get_signal_to_deliver(). + */ + if (utrace_control(current, engine, UTRACE_INTERRUPT)) + WARN_ON(1); + + ctx->signr = info->si_signo; + ctx->stop_code = (PTRACE_EVENT_SIGNAL << 8) | ctx->signr; + + return UTRACE_STOP | UTRACE_SIGNAL_IGN; +} + +static u32 ptrace_report_quiesce(u32 action, struct utrace_engine *engine, + unsigned long event) +{ + struct ptrace_context *ctx = ptrace_context(engine); + + if (ptrace_event_pending(ctx)) + return UTRACE_STOP; + + return event ? UTRACE_RESUME : ctx->resume; +} + +static void ptrace_release(void *data) +{ + kfree(data); +} + +static const struct utrace_engine_ops ptrace_utrace_ops = { + .report_signal = ptrace_report_signal, + .report_quiesce = ptrace_report_quiesce, + .report_exec = ptrace_report_exec, + .report_exit = ptrace_report_exit, + .report_clone = ptrace_report_clone, + .report_syscall_entry = ptrace_report_syscall_entry, + .report_syscall_exit = ptrace_report_syscall_exit, + .release = ptrace_release, +}; + +int ptrace_check_attach(struct task_struct *child, int kill) +{ + struct utrace_engine *engine; + struct utrace_examiner exam; + int ret = -ESRCH; + + engine = ptrace_lookup_engine(child); + if (IS_ERR(engine)) + return ret; + + if (child->parent != current) + goto out; + + if (unlikely(kill)) + ret = 0; + + if (!task_is_stopped_or_traced(child)) + goto out; + /* + * Make sure our engine has already stopped the child. + * Then wait for it to be off the CPU. + */ + if (!utrace_control(child, engine, UTRACE_STOP) && + !utrace_prepare_examine(child, engine, &exam)) + ret = 0; +out: + utrace_engine_put(engine); + return ret; +} + +int ptrace_attach(struct task_struct *task) +{ + int retval; + + audit_ptrace(task); + + retval = -EPERM; + if (unlikely(task->flags & PF_KTHREAD)) + goto out; + if (same_thread_group(task, current)) + goto out; + + /* + * Protect exec's credential calculations against our interference; + * interference; SUID, SGID and LSM creds get determined differently + * under ptrace. + */ + retval = -ERESTARTNOINTR; + if (mutex_lock_interruptible(&task->cred_guard_mutex)) + goto out; + + task_lock(task); + retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH); + task_unlock(task); + if (retval) + goto unlock_creds; + + retval = ptrace_attach_task(task, 0); + if (unlikely(retval)) + goto unlock_creds; + + write_lock_irq(&tasklist_lock); + retval = -EPERM; + if (unlikely(task->exit_state)) + goto unlock_tasklist; + + BUG_ON(task->ptrace); + task->ptrace = PT_UTRACED; + if (capable(CAP_SYS_PTRACE)) + task->ptrace |= PT_PTRACE_CAP; + + __ptrace_link(task, current); + send_sig_info(SIGSTOP, SEND_SIG_FORCED, task); + + retval = 0; +unlock_tasklist: + write_unlock_irq(&tasklist_lock); +unlock_creds: + mutex_unlock(&task->cred_guard_mutex); +out: + return retval; +} + +/* + * Performs checks and sets PT_UTRACED. + * Should be used by all ptrace implementations for PTRACE_TRACEME. + */ +int ptrace_traceme(void) +{ + bool detach = true; + int ret = ptrace_attach_task(current, 0); + + if (unlikely(ret)) + return ret; + + ret = -EPERM; + write_lock_irq(&tasklist_lock); + BUG_ON(current->ptrace); + ret = security_ptrace_traceme(current->parent); + /* + * Check PF_EXITING to ensure ->real_parent has not passed + * exit_ptrace(). Otherwise we don't report the error but + * pretend ->real_parent untraces us right after return. + */ + if (!ret && !(current->real_parent->flags & PF_EXITING)) { + current->ptrace = PT_UTRACED; + __ptrace_link(current, current->real_parent); + detach = false; + } + write_unlock_irq(&tasklist_lock); + + if (detach) + ptrace_abort_attach(current); + return ret; +} + +static void ptrace_do_detach(struct task_struct *tracee, unsigned int data) +{ + bool detach, release; + + write_lock_irq(&tasklist_lock); + /* + * This tracee can be already killed. Make sure de_thread() or + * our sub-thread doing do_wait() didn't do release_task() yet. + */ + detach = tracee->ptrace != 0; + release = false; + if (likely(detach)) + release = __ptrace_detach(current, tracee); + write_unlock_irq(&tasklist_lock); + + if (unlikely(release)) + release_task(tracee); + else if (likely(detach)) + ptrace_detach_task(tracee, data); +} + +int ptrace_detach(struct task_struct *child, unsigned int data) +{ + if (!valid_signal(data)) + return -EIO; + + ptrace_do_detach(child, data); + + return 0; +} + +/* + * Detach all tasks we were using ptrace on. + */ +void exit_ptrace(struct task_struct *tracer) +{ + for (;;) { + struct task_struct *tracee = NULL; + + read_lock(&tasklist_lock); + if (!list_empty(&tracer->ptraced)) { + tracee = list_first_entry(&tracer->ptraced, + struct task_struct, ptrace_entry); + get_task_struct(tracee); + } + read_unlock(&tasklist_lock); + if (!tracee) + break; + + ptrace_do_detach(tracee, -1); + put_task_struct(tracee); + } +} + +static int ptrace_set_options(struct task_struct *tracee, + struct utrace_engine *engine, long data) +{ + BUILD_BUG_ON(PTRACE_O_MASK & PTRACE_O_SYSEMU); + + ptrace_set_events(tracee, engine, data & PTRACE_O_MASK); + return (data & ~PTRACE_O_MASK) ? -EINVAL : 0; +} + +static int ptrace_rw_siginfo(struct task_struct *tracee, + struct ptrace_context *ctx, + siginfo_t *info, bool write) +{ + unsigned long flags; + int err; + + switch (get_stop_event(ctx)) { + case 0: /* jctl stop */ + return -EINVAL; + + case PTRACE_EVENT_SIGNAL: + err = -ESRCH; + if (lock_task_sighand(tracee, &flags)) { + if (likely(task_is_traced(tracee))) { + if (write) + *ctx->siginfo = *info; + else + *info = *ctx->siginfo; + err = 0; + } + unlock_task_sighand(tracee, &flags); + } + + return err; + + default: + if (!write) { + memset(info, 0, sizeof(*info)); + info->si_signo = SIGTRAP; + info->si_code = ctx->stop_code & PTRACE_EVENT_MASK; + info->si_pid = task_pid_vnr(tracee); + info->si_uid = task_uid(tracee); + } + + return 0; + } +} + +static void do_ptrace_notify_stop(struct ptrace_context *ctx, + struct task_struct *tracee) +{ + /* + * This can race with SIGKILL, but we borrow this race from + * the old ptrace implementation. ->exit_code is only needed + * for wait_task_stopped()->task_stopped_code(), we should + * change it to use ptrace_context. + */ + tracee->exit_code = ctx->stop_code & PTRACE_EVENT_MASK; + WARN_ON(!tracee->exit_code); + + read_lock(&tasklist_lock); + /* + * Don't want to allow preemption here, because + * sys_ptrace() needs this task to be inactive. + */ + preempt_disable(); + /* + * It can be killed and then released by our subthread, + * or ptrace_attach() has not completed yet. + */ + if (task_ptrace(tracee)) + do_notify_parent_cldstop(tracee, CLD_TRAPPED); + read_unlock(&tasklist_lock); + preempt_enable_no_resched(); +} + +void ptrace_notify_stop(struct task_struct *tracee) +{ + struct utrace_engine *engine = ptrace_lookup_engine(tracee); + + if (IS_ERR(engine)) + return; + + do_ptrace_notify_stop(ptrace_context(engine), tracee); + utrace_engine_put(engine); +} + +static int ptrace_resume_action(struct task_struct *tracee, + struct utrace_engine *engine, long request) +{ + struct ptrace_context *ctx = ptrace_context(engine); + unsigned long events; + int action; + + ctx->options &= ~PTRACE_O_SYSEMU; + events = engine->flags & ~UTRACE_EVENT_SYSCALL; + action = UTRACE_RESUME; + + switch (request) { +#ifdef PTRACE_SINGLEBLOCK + case PTRACE_SINGLEBLOCK: + if (unlikely(!arch_has_block_step())) + return -EIO; + action = UTRACE_BLOCKSTEP; + events |= UTRACE_EVENT(SYSCALL_EXIT); + break; +#endif + +#ifdef PTRACE_SINGLESTEP + case PTRACE_SINGLESTEP: + if (unlikely(!arch_has_single_step())) + return -EIO; + action = UTRACE_SINGLESTEP; + events |= UTRACE_EVENT(SYSCALL_EXIT); + break; +#endif + +#ifdef PTRACE_SYSEMU + case PTRACE_SYSEMU_SINGLESTEP: + if (unlikely(!arch_has_single_step())) + return -EIO; + action = UTRACE_SINGLESTEP; + case PTRACE_SYSEMU: + ctx->options |= PTRACE_O_SYSEMU; + events |= UTRACE_EVENT(SYSCALL_ENTRY); + break; +#endif + + case PTRACE_SYSCALL: + events |= UTRACE_EVENT_SYSCALL; + break; + + case PTRACE_CONT: + break; + default: + return -EIO; + } + + if (events != engine->flags && + utrace_set_events(tracee, engine, events)) + return -ESRCH; + + return action; +} + +static int ptrace_resume(struct task_struct *tracee, + struct utrace_engine *engine, + long request, long data) +{ + struct ptrace_context *ctx = ptrace_context(engine); + int action; + + if (!valid_signal(data)) + return -EIO; + + action = ptrace_resume_action(tracee, engine, request); + if (action < 0) + return action; + + switch (get_stop_event(ctx)) { + case PTRACE_EVENT_VFORK: + if (ctx->options & PTRACE_O_TRACEVFORKDONE) { + set_stop_code(ctx, PTRACE_EVENT_VFORK_DONE); + action = UTRACE_REPORT; + } + break; + + case PTRACE_EVENT_EXEC: + case PTRACE_EVENT_FORK: + case PTRACE_EVENT_CLONE: + case PTRACE_EVENT_VFORK_DONE: + if (request == PTRACE_SYSCALL) { + set_syscall_code(ctx); + do_ptrace_notify_stop(ctx, tracee); + return 0; + } + + if (action != UTRACE_RESUME) { + /* + * single-stepping. UTRACE_SIGNAL_REPORT will + * synthesize a trap to follow the syscall insn. + */ + ctx->signr = SIGTRAP; + action = UTRACE_INTERRUPT; + } + break; + + case PTRACE_EVENT_SYSCALL: + if (data) + send_sig_info(data, SEND_SIG_PRIV, tracee); + break; + + case PTRACE_EVENT_SIGNAL: + ctx->signr = data; + break; + } + + ctx->resume = action; + ptrace_wake_up(tracee, engine, action, true); + return 0; +} + +extern int ptrace_regset(struct task_struct *task, int req, unsigned int type, + struct iovec *kiov); + +int ptrace_request(struct task_struct *child, long request, + long addr, long data) +{ + struct utrace_engine *engine = ptrace_lookup_engine(child); + siginfo_t siginfo; + int ret; + + if (unlikely(IS_ERR(engine))) + return -ESRCH; + + switch (request) { + case PTRACE_PEEKTEXT: + case PTRACE_PEEKDATA: + ret = generic_ptrace_peekdata(child, addr, data); + break; + case PTRACE_POKETEXT: + case PTRACE_POKEDATA: + ret = generic_ptrace_pokedata(child, addr, data); + break; + +#ifdef PTRACE_OLDSETOPTIONS + case PTRACE_OLDSETOPTIONS: +#endif + case PTRACE_SETOPTIONS: + ret = ptrace_set_options(child, engine, data); + break; + case PTRACE_GETEVENTMSG: + ret = put_user(ptrace_context(engine)->eventmsg, + (unsigned long __user *) data); + break; + + case PTRACE_GETSIGINFO: + ret = ptrace_rw_siginfo(child, ptrace_context(engine), + &siginfo, false); + if (!ret) + ret = copy_siginfo_to_user((siginfo_t __user *) data, + &siginfo); + break; + + case PTRACE_SETSIGINFO: + if (copy_from_user(&siginfo, (siginfo_t __user *) data, + sizeof siginfo)) + ret = -EFAULT; + else + ret = ptrace_rw_siginfo(child, ptrace_context(engine), + &siginfo, true); + break; + + case PTRACE_DETACH: /* detach a process that was attached. */ + ret = ptrace_detach(child, data); + break; + + case PTRACE_KILL: + /* Ugly historical behaviour. */ + if (task_is_traced(child)) + ptrace_resume(child, engine, PTRACE_CONT, SIGKILL); + ret = 0; + break; + + case PTRACE_GETREGSET: + case PTRACE_SETREGSET: + { + struct iovec kiov; + struct iovec __user *uiov = (struct iovec __user *) data; + + if (!access_ok(VERIFY_WRITE, uiov, sizeof(*uiov))) + return -EFAULT; + + if (__get_user(kiov.iov_base, &uiov->iov_base) || + __get_user(kiov.iov_len, &uiov->iov_len)) + return -EFAULT; + + ret = ptrace_regset(child, request, addr, &kiov); + if (!ret) + ret = __put_user(kiov.iov_len, &uiov->iov_len); + break; + } + + default: + ret = ptrace_resume(child, engine, request, data); + break; + } + + utrace_engine_put(engine); + return ret; +} + +#if defined CONFIG_COMPAT +#include + +int compat_ptrace_request(struct task_struct *child, compat_long_t request, + compat_ulong_t addr, compat_ulong_t data) +{ + struct utrace_engine *engine = ptrace_lookup_engine(child); + compat_ulong_t __user *datap = compat_ptr(data); + compat_ulong_t word; + siginfo_t siginfo; + int ret; + + if (unlikely(IS_ERR(engine))) + return -ESRCH; + + switch (request) { + case PTRACE_PEEKTEXT: + case PTRACE_PEEKDATA: + ret = access_process_vm(child, addr, &word, sizeof(word), 0); + if (ret != sizeof(word)) + ret = -EIO; + else + ret = put_user(word, datap); + break; + + case PTRACE_POKETEXT: + case PTRACE_POKEDATA: + ret = access_process_vm(child, addr, &data, sizeof(data), 1); + ret = (ret != sizeof(data) ? -EIO : 0); + break; + + case PTRACE_GETEVENTMSG: + ret = put_user((compat_ulong_t)ptrace_context(engine)->eventmsg, + datap); + break; + + case PTRACE_GETSIGINFO: + ret = ptrace_rw_siginfo(child, ptrace_context(engine), + &siginfo, false); + if (!ret) + ret = copy_siginfo_to_user32( + (struct compat_siginfo __user *) datap, + &siginfo); + break; + + case PTRACE_SETSIGINFO: + memset(&siginfo, 0, sizeof siginfo); + if (copy_siginfo_from_user32( + &siginfo, (struct compat_siginfo __user *) datap)) + ret = -EFAULT; + else + ret = ptrace_rw_siginfo(child, ptrace_context(engine), + &siginfo, true); + break; + + case PTRACE_GETREGSET: + case PTRACE_SETREGSET: + { + struct iovec kiov; + struct compat_iovec __user *uiov = + (struct compat_iovec __user *) datap; + compat_uptr_t ptr; + compat_size_t len; + + if (!access_ok(VERIFY_WRITE, uiov, sizeof(*uiov))) + return -EFAULT; + + if (__get_user(ptr, &uiov->iov_base) || + __get_user(len, &uiov->iov_len)) + return -EFAULT; + + kiov.iov_base = compat_ptr(ptr); + kiov.iov_len = len; + + ret = ptrace_regset(child, request, addr, &kiov); + if (!ret) + ret = __put_user(kiov.iov_len, &uiov->iov_len); + break; + } + + default: + ret = ptrace_request(child, request, addr, data); + } + + utrace_engine_put(engine); + return ret; +} +#endif /* CONFIG_COMPAT */ diff --git a/kernel/ptrace.c b/kernel/ptrace.c index f34d798..daed9e8 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -23,7 +23,317 @@ #include #include +int __ptrace_may_access(struct task_struct *task, unsigned int mode) +{ + const struct cred *cred = current_cred(), *tcred; + + /* May we inspect the given task? + * This check is used both for attaching with ptrace + * and for allowing access to sensitive information in /proc. + * + * ptrace_attach denies several cases that /proc allows + * because setting up the necessary parent/child relationship + * or halting the specified task is impossible. + */ + int dumpable = 0; + /* Don't let security modules deny introspection */ + if (task == current) + return 0; + rcu_read_lock(); + tcred = __task_cred(task); + if ((cred->uid != tcred->euid || + cred->uid != tcred->suid || + cred->uid != tcred->uid || + cred->gid != tcred->egid || + cred->gid != tcred->sgid || + cred->gid != tcred->gid) && + !capable(CAP_SYS_PTRACE)) { + rcu_read_unlock(); + return -EPERM; + } + rcu_read_unlock(); + smp_rmb(); + if (task->mm) + dumpable = get_dumpable(task->mm); + if (!dumpable && !capable(CAP_SYS_PTRACE)) + return -EPERM; + + return security_ptrace_access_check(task, mode); +} + +bool ptrace_may_access(struct task_struct *task, unsigned int mode) +{ + int err; + task_lock(task); + err = __ptrace_may_access(task, mode); + task_unlock(task); + return !err; +} + +/* + * Called with irqs disabled, returns true if childs should reap themselves. + */ +static int ignoring_children(struct sighand_struct *sigh) +{ + int ret; + spin_lock(&sigh->siglock); + ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) || + (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT); + spin_unlock(&sigh->siglock); + return ret; +} + +/* + * Called with tasklist_lock held for writing. + * Unlink a traced task, and clean it up if it was a traced zombie. + * Return true if it needs to be reaped with release_task(). + * (We can't call release_task() here because we already hold tasklist_lock.) + * + * If it's a zombie, our attachedness prevented normal parent notification + * or self-reaping. Do notification now if it would have happened earlier. + * If it should reap itself, return true. + * + * If it's our own child, there is no notification to do. But if our normal + * children self-reap, then this child was prevented by ptrace and we must + * reap it now, in that case we must also wake up sub-threads sleeping in + * do_wait(). + */ +bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p) +{ + __ptrace_unlink(p); + + if (p->exit_state == EXIT_ZOMBIE) { + if (!task_detached(p) && thread_group_empty(p)) { + if (!same_thread_group(p->real_parent, tracer)) + do_notify_parent(p, p->exit_signal); + else if (ignoring_children(tracer->sighand)) { + __wake_up_parent(p, tracer); + p->exit_signal = -1; + } + } + if (task_detached(p)) { + /* Mark it as in the process of being reaped. */ + p->exit_state = EXIT_DEAD; + return true; + } + } + + return false; +} + +int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len) +{ + int copied = 0; + + while (len > 0) { + char buf[128]; + int this_len, retval; + + this_len = (len > sizeof(buf)) ? sizeof(buf) : len; + retval = access_process_vm(tsk, src, buf, this_len, 0); + if (!retval) { + if (copied) + break; + return -EIO; + } + if (copy_to_user(dst, buf, retval)) + return -EFAULT; + copied += retval; + src += retval; + dst += retval; + len -= retval; + } + return copied; +} + +int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len) +{ + int copied = 0; + + while (len > 0) { + char buf[128]; + int this_len, retval; + + this_len = (len > sizeof(buf)) ? sizeof(buf) : len; + if (copy_from_user(buf, src, this_len)) + return -EFAULT; + retval = access_process_vm(tsk, dst, buf, this_len, 1); + if (!retval) { + if (copied) + break; + return -EIO; + } + copied += retval; + src += retval; + dst += retval; + len -= retval; + } + return copied; +} + +#ifdef CONFIG_HAVE_ARCH_TRACEHOOK + +static const struct user_regset * +find_regset(const struct user_regset_view *view, unsigned int type) +{ + const struct user_regset *regset; + int n; + + for (n = 0; n < view->n; ++n) { + regset = view->regsets + n; + if (regset->core_note_type == type) + return regset; + } + + return NULL; +} + +int ptrace_regset(struct task_struct *task, int req, unsigned int type, + struct iovec *kiov) +{ + const struct user_regset_view *view = task_user_regset_view(task); + const struct user_regset *regset = find_regset(view, type); + int regset_no; + + if (!regset || (kiov->iov_len % regset->size) != 0) + return -EINVAL; + + regset_no = regset - view->regsets; + kiov->iov_len = min(kiov->iov_len, + (__kernel_size_t) (regset->n * regset->size)); + + if (req == PTRACE_GETREGSET) + return copy_regset_to_user(task, view, regset_no, 0, + kiov->iov_len, kiov->iov_base); + else + return copy_regset_from_user(task, view, regset_no, 0, + kiov->iov_len, kiov->iov_base); +} + +#endif + +static struct task_struct *ptrace_get_task_struct(pid_t pid) +{ + struct task_struct *child; + + rcu_read_lock(); + child = find_task_by_vpid(pid); + if (child) + get_task_struct(child); + rcu_read_unlock(); + + if (!child) + return ERR_PTR(-ESRCH); + return child; +} + +#ifndef arch_ptrace_attach +#define arch_ptrace_attach(child) do { } while (0) +#endif + +SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data) +{ + struct task_struct *child; + long ret; + + if (request == PTRACE_TRACEME) { + ret = ptrace_traceme(); + if (!ret) + arch_ptrace_attach(current); + goto out; + } + + child = ptrace_get_task_struct(pid); + if (IS_ERR(child)) { + ret = PTR_ERR(child); + goto out; + } + + if (request == PTRACE_ATTACH) { + ret = ptrace_attach(child); + /* + * Some architectures need to do book-keeping after + * a ptrace attach. + */ + if (!ret) + arch_ptrace_attach(child); + goto out_put_task_struct; + } + + ret = ptrace_check_attach(child, request == PTRACE_KILL); + if (ret < 0) + goto out_put_task_struct; + + ret = arch_ptrace(child, request, addr, data); + + out_put_task_struct: + put_task_struct(child); + out: + return ret; +} +int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data) +{ + unsigned long tmp; + int copied; + + copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0); + if (copied != sizeof(tmp)) + return -EIO; + return put_user(tmp, (unsigned long __user *)data); +} + +int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data) +{ + int copied; + + copied = access_process_vm(tsk, addr, &data, sizeof(data), 1); + return (copied == sizeof(data)) ? 0 : -EIO; +} + +#if defined CONFIG_COMPAT +#include + +asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid, + compat_long_t addr, compat_long_t data) +{ + struct task_struct *child; + long ret; + + if (request == PTRACE_TRACEME) { + ret = ptrace_traceme(); + goto out; + } + + child = ptrace_get_task_struct(pid); + if (IS_ERR(child)) { + ret = PTR_ERR(child); + goto out; + } + + if (request == PTRACE_ATTACH) { + ret = ptrace_attach(child); + /* + * Some architectures need to do book-keeping after + * a ptrace attach. + */ + if (!ret) + arch_ptrace_attach(child); + goto out_put_task_struct; + } + + ret = ptrace_check_attach(child, request == PTRACE_KILL); + if (!ret) + ret = compat_arch_ptrace(child, request, addr, data); + + out_put_task_struct: + put_task_struct(child); + out: + return ret; +} +#endif /* CONFIG_COMPAT */ + +#ifndef CONFIG_UTRACE /* * ptrace a task: make the debugger its new parent and * move it to the ptrace list. @@ -116,53 +426,6 @@ int ptrace_check_attach(struct task_struct *child, int kill) return ret; } -int __ptrace_may_access(struct task_struct *task, unsigned int mode) -{ - const struct cred *cred = current_cred(), *tcred; - - /* May we inspect the given task? - * This check is used both for attaching with ptrace - * and for allowing access to sensitive information in /proc. - * - * ptrace_attach denies several cases that /proc allows - * because setting up the necessary parent/child relationship - * or halting the specified task is impossible. - */ - int dumpable = 0; - /* Don't let security modules deny introspection */ - if (task == current) - return 0; - rcu_read_lock(); - tcred = __task_cred(task); - if ((cred->uid != tcred->euid || - cred->uid != tcred->suid || - cred->uid != tcred->uid || - cred->gid != tcred->egid || - cred->gid != tcred->sgid || - cred->gid != tcred->gid) && - !capable(CAP_SYS_PTRACE)) { - rcu_read_unlock(); - return -EPERM; - } - rcu_read_unlock(); - smp_rmb(); - if (task->mm) - dumpable = get_dumpable(task->mm); - if (!dumpable && !capable(CAP_SYS_PTRACE)) - return -EPERM; - - return security_ptrace_access_check(task, mode); -} - -bool ptrace_may_access(struct task_struct *task, unsigned int mode) -{ - int err; - task_lock(task); - err = __ptrace_may_access(task, mode); - task_unlock(task); - return !err; -} - int ptrace_attach(struct task_struct *task) { int retval; @@ -205,92 +468,41 @@ int ptrace_attach(struct task_struct *task) send_sig_info(SIGSTOP, SEND_SIG_FORCED, task); retval = 0; -unlock_tasklist: - write_unlock_irq(&tasklist_lock); -unlock_creds: - mutex_unlock(&task->cred_guard_mutex); -out: - return retval; -} - -/** - * ptrace_traceme -- helper for PTRACE_TRACEME - * - * Performs checks and sets PT_PTRACED. - * Should be used by all ptrace implementations for PTRACE_TRACEME. - */ -int ptrace_traceme(void) -{ - int ret = -EPERM; - - write_lock_irq(&tasklist_lock); - /* Are we already being traced? */ - if (!current->ptrace) { - ret = security_ptrace_traceme(current->parent); - /* - * Check PF_EXITING to ensure ->real_parent has not passed - * exit_ptrace(). Otherwise we don't report the error but - * pretend ->real_parent untraces us right after return. - */ - if (!ret && !(current->real_parent->flags & PF_EXITING)) { - current->ptrace = PT_PTRACED; - __ptrace_link(current, current->real_parent); - } - } - write_unlock_irq(&tasklist_lock); - - return ret; -} - -/* - * Called with irqs disabled, returns true if childs should reap themselves. - */ -static int ignoring_children(struct sighand_struct *sigh) -{ - int ret; - spin_lock(&sigh->siglock); - ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) || - (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT); - spin_unlock(&sigh->siglock); - return ret; -} - -/* - * Called with tasklist_lock held for writing. - * Unlink a traced task, and clean it up if it was a traced zombie. - * Return true if it needs to be reaped with release_task(). - * (We can't call release_task() here because we already hold tasklist_lock.) - * - * If it's a zombie, our attachedness prevented normal parent notification - * or self-reaping. Do notification now if it would have happened earlier. - * If it should reap itself, return true. +unlock_tasklist: + write_unlock_irq(&tasklist_lock); +unlock_creds: + mutex_unlock(&task->cred_guard_mutex); +out: + return retval; +} + +/** + * ptrace_traceme -- helper for PTRACE_TRACEME * - * If it's our own child, there is no notification to do. But if our normal - * children self-reap, then this child was prevented by ptrace and we must - * reap it now, in that case we must also wake up sub-threads sleeping in - * do_wait(). + * Performs checks and sets PT_PTRACED. + * Should be used by all ptrace implementations for PTRACE_TRACEME. */ -static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p) +int ptrace_traceme(void) { - __ptrace_unlink(p); + int ret = -EPERM; - if (p->exit_state == EXIT_ZOMBIE) { - if (!task_detached(p) && thread_group_empty(p)) { - if (!same_thread_group(p->real_parent, tracer)) - do_notify_parent(p, p->exit_signal); - else if (ignoring_children(tracer->sighand)) { - __wake_up_parent(p, tracer); - p->exit_signal = -1; - } - } - if (task_detached(p)) { - /* Mark it as in the process of being reaped. */ - p->exit_state = EXIT_DEAD; - return true; + write_lock_irq(&tasklist_lock); + /* Are we already being traced? */ + if (!current->ptrace) { + ret = security_ptrace_traceme(current->parent); + /* + * Check PF_EXITING to ensure ->real_parent has not passed + * exit_ptrace(). Otherwise we don't report the error but + * pretend ->real_parent untraces us right after return. + */ + if (!ret && !(current->real_parent->flags & PF_EXITING)) { + current->ptrace = PT_PTRACED; + __ptrace_link(current, current->real_parent); } } + write_unlock_irq(&tasklist_lock); - return false; + return ret; } int ptrace_detach(struct task_struct *child, unsigned int data) @@ -352,56 +564,6 @@ void exit_ptrace(struct task_struct *tracer) write_lock_irq(&tasklist_lock); } -int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len) -{ - int copied = 0; - - while (len > 0) { - char buf[128]; - int this_len, retval; - - this_len = (len > sizeof(buf)) ? sizeof(buf) : len; - retval = access_process_vm(tsk, src, buf, this_len, 0); - if (!retval) { - if (copied) - break; - return -EIO; - } - if (copy_to_user(dst, buf, retval)) - return -EFAULT; - copied += retval; - src += retval; - dst += retval; - len -= retval; - } - return copied; -} - -int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len) -{ - int copied = 0; - - while (len > 0) { - char buf[128]; - int this_len, retval; - - this_len = (len > sizeof(buf)) ? sizeof(buf) : len; - if (copy_from_user(buf, src, this_len)) - return -EFAULT; - retval = access_process_vm(tsk, dst, buf, this_len, 1); - if (!retval) { - if (copied) - break; - return -EIO; - } - copied += retval; - src += retval; - dst += retval; - len -= retval; - } - return copied; -} - static int ptrace_setoptions(struct task_struct *child, long data) { child->ptrace &= ~PT_TRACE_MASK; @@ -462,7 +624,6 @@ static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info) return error; } - #ifdef PTRACE_SINGLESTEP #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP) #else @@ -516,47 +677,6 @@ static int ptrace_resume(struct task_struct *child, long request, long data) return 0; } -#ifdef CONFIG_HAVE_ARCH_TRACEHOOK - -static const struct user_regset * -find_regset(const struct user_regset_view *view, unsigned int type) -{ - const struct user_regset *regset; - int n; - - for (n = 0; n < view->n; ++n) { - regset = view->regsets + n; - if (regset->core_note_type == type) - return regset; - } - - return NULL; -} - -static int ptrace_regset(struct task_struct *task, int req, unsigned int type, - struct iovec *kiov) -{ - const struct user_regset_view *view = task_user_regset_view(task); - const struct user_regset *regset = find_regset(view, type); - int regset_no; - - if (!regset || (kiov->iov_len % regset->size) != 0) - return -EINVAL; - - regset_no = regset - view->regsets; - kiov->iov_len = min(kiov->iov_len, - (__kernel_size_t) (regset->n * regset->size)); - - if (req == PTRACE_GETREGSET) - return copy_regset_to_user(task, view, regset_no, 0, - kiov->iov_len, kiov->iov_base); - else - return copy_regset_from_user(task, view, regset_no, 0, - kiov->iov_len, kiov->iov_base); -} - -#endif - int ptrace_request(struct task_struct *child, long request, long addr, long data) { @@ -672,88 +792,7 @@ int ptrace_request(struct task_struct *child, long request, return ret; } -static struct task_struct *ptrace_get_task_struct(pid_t pid) -{ - struct task_struct *child; - - rcu_read_lock(); - child = find_task_by_vpid(pid); - if (child) - get_task_struct(child); - rcu_read_unlock(); - - if (!child) - return ERR_PTR(-ESRCH); - return child; -} - -#ifndef arch_ptrace_attach -#define arch_ptrace_attach(child) do { } while (0) -#endif - -SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data) -{ - struct task_struct *child; - long ret; - - if (request == PTRACE_TRACEME) { - ret = ptrace_traceme(); - if (!ret) - arch_ptrace_attach(current); - goto out; - } - - child = ptrace_get_task_struct(pid); - if (IS_ERR(child)) { - ret = PTR_ERR(child); - goto out; - } - - if (request == PTRACE_ATTACH) { - ret = ptrace_attach(child); - /* - * Some architectures need to do book-keeping after - * a ptrace attach. - */ - if (!ret) - arch_ptrace_attach(child); - goto out_put_task_struct; - } - - ret = ptrace_check_attach(child, request == PTRACE_KILL); - if (ret < 0) - goto out_put_task_struct; - - ret = arch_ptrace(child, request, addr, data); - - out_put_task_struct: - put_task_struct(child); - out: - return ret; -} - -int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data) -{ - unsigned long tmp; - int copied; - - copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0); - if (copied != sizeof(tmp)) - return -EIO; - return put_user(tmp, (unsigned long __user *)data); -} - -int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data) -{ - int copied; - - copied = access_process_vm(tsk, addr, &data, sizeof(data), 1); - return (copied == sizeof(data)) ? 0 : -EIO; -} - #if defined CONFIG_COMPAT -#include - int compat_ptrace_request(struct task_struct *child, compat_long_t request, compat_ulong_t addr, compat_ulong_t data) { @@ -831,42 +870,5 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request, return ret; } - -asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid, - compat_long_t addr, compat_long_t data) -{ - struct task_struct *child; - long ret; - - if (request == PTRACE_TRACEME) { - ret = ptrace_traceme(); - goto out; - } - - child = ptrace_get_task_struct(pid); - if (IS_ERR(child)) { - ret = PTR_ERR(child); - goto out; - } - - if (request == PTRACE_ATTACH) { - ret = ptrace_attach(child); - /* - * Some architectures need to do book-keeping after - * a ptrace attach. - */ - if (!ret) - arch_ptrace_attach(child); - goto out_put_task_struct; - } - - ret = ptrace_check_attach(child, request == PTRACE_KILL); - if (!ret) - ret = compat_arch_ptrace(child, request, addr, data); - - out_put_task_struct: - put_task_struct(child); - out: - return ret; -} #endif /* CONFIG_COMPAT */ +#endif /* CONFIG_UTRACE */ diff --git a/kernel/signal.c b/kernel/signal.c index bded651..6d13d9f 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1521,7 +1521,7 @@ int do_notify_parent(struct task_struct *tsk, int sig) return ret; } -static void do_notify_parent_cldstop(struct task_struct *tsk, int why) +void do_notify_parent_cldstop(struct task_struct *tsk, int why) { struct siginfo info; unsigned long flags; @@ -1791,7 +1791,7 @@ static int do_signal_stop(int signr) static int ptrace_signal(int signr, siginfo_t *info, struct pt_regs *regs, void *cookie) { - if (!task_ptrace(current)) + if (!(task_ptrace(current) & PT_PTRACED)) return signr; ptrace_signal_deliver(regs, cookie); diff --git a/kernel/utrace.c b/kernel/utrace.c new file mode 100644 index 0000000..4d61096 --- /dev/null +++ b/kernel/utrace.c @@ -0,0 +1,2450 @@ +/* + * utrace infrastructure interface for debugging user processes + * + * Copyright (C) 2006-2010 Red Hat, Inc. All rights reserved. + * + * This copyrighted material is made available to anyone wishing to use, + * modify, copy, or redistribute it subject to the terms and conditions + * of the GNU General Public License v.2. + * + * Red Hat Author: Roland McGrath. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + + +/* + * Per-thread structure private to utrace implementation. + * If task_struct.utrace_flags is nonzero, task_struct.utrace + * has always been allocated first. Once allocated, it is + * never freed until free_task(). + * + * The common event reporting loops are done by the task making the + * report without ever taking any locks. To facilitate this, the two + * lists @attached and @attaching work together for smooth asynchronous + * attaching with low overhead. Modifying either list requires @lock. + * The @attaching list can be modified any time while holding @lock. + * New engines being attached always go on this list. + * + * The @attached list is what the task itself uses for its reporting + * loops. When the task itself is not quiescent, it can use the + * @attached list without taking any lock. Nobody may modify the list + * when the task is not quiescent. When it is quiescent, that means + * that it won't run again without taking @lock itself before using + * the list. + * + * At each place where we know the task is quiescent (or it's current), + * while holding @lock, we call splice_attaching(), below. This moves + * the @attaching list members on to the end of the @attached list. + * Since this happens at the start of any reporting pass, any new + * engines attached asynchronously go on the stable @attached list + * in time to have their callbacks seen. + */ +struct utrace { + spinlock_t lock; + struct list_head attached, attaching; + + struct task_struct *cloning; + + struct utrace_engine *reporting; + + enum utrace_resume_action resume:UTRACE_RESUME_BITS; + unsigned int signal_handler:1; + unsigned int vfork_stop:1; /* need utrace_stop() before vfork wait */ + unsigned int death:1; /* in utrace_report_death() now */ + unsigned int reap:1; /* release_task() has run */ + unsigned int pending_attach:1; /* need splice_attaching() */ +}; + +static struct kmem_cache *utrace_cachep; +static struct kmem_cache *utrace_engine_cachep; +static const struct utrace_engine_ops utrace_detached_ops; /* forward decl */ + +static int __init utrace_init(void) +{ + utrace_cachep = KMEM_CACHE(utrace, SLAB_PANIC); + utrace_engine_cachep = KMEM_CACHE(utrace_engine, SLAB_PANIC); + return 0; +} +module_init(utrace_init); + +/* + * Set up @task.utrace for the first time. We can have races + * between two utrace_attach_task() calls here. The task_lock() + * governs installing the new pointer. If another one got in first, + * we just punt the new one we allocated. + * + * This returns false only in case of a memory allocation failure. + */ +static bool utrace_task_alloc(struct task_struct *task) +{ + struct utrace *utrace = kmem_cache_zalloc(utrace_cachep, GFP_KERNEL); + if (unlikely(!utrace)) + return false; + spin_lock_init(&utrace->lock); + INIT_LIST_HEAD(&utrace->attached); + INIT_LIST_HEAD(&utrace->attaching); + utrace->resume = UTRACE_RESUME; + task_lock(task); + if (likely(!task->utrace)) { + /* + * This barrier makes sure the initialization of the struct + * precedes the installation of the pointer. This pairs + * with smp_read_barrier_depends() in task_utrace_struct(). + */ + smp_wmb(); + task->utrace = utrace; + } + task_unlock(task); + + if (unlikely(task->utrace != utrace)) + kmem_cache_free(utrace_cachep, utrace); + return true; +} + +/* + * This is called via tracehook_free_task() from free_task() + * when @task is being deallocated. + */ +void utrace_free_task(struct task_struct *task) +{ + kmem_cache_free(utrace_cachep, task->utrace); +} + +/* + * This is calledwhen the task is safely quiescent, i.e. it won't consult + * utrace->attached without the lock. Move any engines attached + * asynchronously from @utrace->attaching onto the @utrace->attached list. + */ +static void splice_attaching(struct utrace *utrace) +{ + lockdep_assert_held(&utrace->lock); + list_splice_tail_init(&utrace->attaching, &utrace->attached); + utrace->pending_attach = 0; +} + +/* + * This is the exported function used by the utrace_engine_put() inline. + */ +void __utrace_engine_release(struct kref *kref) +{ + struct utrace_engine *engine = container_of(kref, struct utrace_engine, + kref); + BUG_ON(!list_empty(&engine->entry)); + if (engine->release) + (*engine->release)(engine->data); + kmem_cache_free(utrace_engine_cachep, engine); +} +EXPORT_SYMBOL_GPL(__utrace_engine_release); + +static bool engine_matches(struct utrace_engine *engine, int flags, + const struct utrace_engine_ops *ops, void *data) +{ + if ((flags & UTRACE_ATTACH_MATCH_OPS) && engine->ops != ops) + return false; + if ((flags & UTRACE_ATTACH_MATCH_DATA) && engine->data != data) + return false; + return engine->ops && engine->ops != &utrace_detached_ops; +} + +static struct utrace_engine *find_matching_engine( + struct utrace *utrace, int flags, + const struct utrace_engine_ops *ops, void *data) +{ + struct utrace_engine *engine; + list_for_each_entry(engine, &utrace->attached, entry) + if (engine_matches(engine, flags, ops, data)) + return engine; + list_for_each_entry(engine, &utrace->attaching, entry) + if (engine_matches(engine, flags, ops, data)) + return engine; + return NULL; +} + +/* + * Enqueue @engine, or maybe don't if UTRACE_ATTACH_EXCLUSIVE. + */ +static int utrace_add_engine(struct task_struct *target, + struct utrace *utrace, + struct utrace_engine *engine, + int flags, + const struct utrace_engine_ops *ops, + void *data) +{ + int ret; + + spin_lock(&utrace->lock); + + ret = -EEXIST; + if ((flags & UTRACE_ATTACH_EXCLUSIVE) && + unlikely(find_matching_engine(utrace, flags, ops, data))) + goto unlock; + + /* + * In case we had no engines before, make sure that + * utrace_flags is not zero. Since we did unlock+lock + * at least once after utrace_task_alloc() installed + * ->utrace, we have the necessary barrier which pairs + * with rmb() in task_utrace_struct(). + */ + ret = -ESRCH; + if (!target->utrace_flags) { + target->utrace_flags = UTRACE_EVENT(REAP); + /* + * If we race with tracehook_prepare_release_task() + * make sure that either it sees utrace_flags != 0 + * or we see exit_state == EXIT_DEAD. + */ + smp_mb(); + if (unlikely(target->exit_state == EXIT_DEAD)) { + target->utrace_flags = 0; + goto unlock; + } + } + + /* + * Put the new engine on the pending ->attaching list. + * Make sure it gets onto the ->attached list by the next + * time it's examined. Setting ->pending_attach ensures + * that start_report() takes the lock and splices the lists + * before the next new reporting pass. + * + * When target == current, it would be safe just to call + * splice_attaching() right here. But if we're inside a + * callback, that would mean the new engine also gets + * notified about the event that precipitated its own + * creation. This is not what the user wants. + */ + list_add_tail(&engine->entry, &utrace->attaching); + utrace->pending_attach = 1; + utrace_engine_get(engine); + ret = 0; +unlock: + spin_unlock(&utrace->lock); + + return ret; +} + +/** + * utrace_attach_task - attach new engine, or look up an attached engine + * @target: thread to attach to + * @flags: flag bits combined with OR, see below + * @ops: callback table for new engine + * @data: engine private data pointer + * + * The caller must ensure that the @target thread does not get freed, + * i.e. hold a ref or be its parent. It is always safe to call this + * on @current, or on the @child pointer in a @report_clone callback. + * For most other cases, it's easier to use utrace_attach_pid() instead. + * + * UTRACE_ATTACH_CREATE: + * Create a new engine. If %UTRACE_ATTACH_CREATE is not specified, you + * only look up an existing engine already attached to the thread. + * + * UTRACE_ATTACH_EXCLUSIVE: + * Attempting to attach a second (matching) engine fails with -%EEXIST. + * + * UTRACE_ATTACH_MATCH_OPS: Only consider engines matching @ops. + * UTRACE_ATTACH_MATCH_DATA: Only consider engines matching @data. + * + * Calls with neither %UTRACE_ATTACH_MATCH_OPS nor %UTRACE_ATTACH_MATCH_DATA + * match the first among any engines attached to @target. That means that + * %UTRACE_ATTACH_EXCLUSIVE in such a call fails with -%EEXIST if there + * are any engines on @target at all. + */ +struct utrace_engine *utrace_attach_task( + struct task_struct *target, int flags, + const struct utrace_engine_ops *ops, void *data) +{ + struct utrace *utrace = task_utrace_struct(target); + struct utrace_engine *engine; + int ret; + + if (!(flags & UTRACE_ATTACH_CREATE)) { + if (unlikely(!utrace)) + return ERR_PTR(-ENOENT); + spin_lock(&utrace->lock); + engine = find_matching_engine(utrace, flags, ops, data); + if (engine) + utrace_engine_get(engine); + spin_unlock(&utrace->lock); + return engine ?: ERR_PTR(-ENOENT); + } + + if (unlikely(!ops) || unlikely(ops == &utrace_detached_ops)) + return ERR_PTR(-EINVAL); + + if (unlikely(target->flags & PF_KTHREAD)) + /* + * Silly kernel, utrace is for users! + */ + return ERR_PTR(-EPERM); + + if (!utrace) { + if (unlikely(!utrace_task_alloc(target))) + return ERR_PTR(-ENOMEM); + utrace = task_utrace_struct(target); + } + + engine = kmem_cache_alloc(utrace_engine_cachep, GFP_KERNEL); + if (unlikely(!engine)) + return ERR_PTR(-ENOMEM); + + /* + * Initialize the new engine structure. It starts out with one ref + * to return. utrace_add_engine() adds another for being attached. + */ + kref_init(&engine->kref); + engine->flags = 0; + engine->ops = ops; + engine->data = data; + engine->release = ops->release; + + ret = utrace_add_engine(target, utrace, engine, flags, ops, data); + + if (unlikely(ret)) { + kmem_cache_free(utrace_engine_cachep, engine); + engine = ERR_PTR(ret); + } + + + return engine; +} +EXPORT_SYMBOL_GPL(utrace_attach_task); + +/** + * utrace_attach_pid - attach new engine, or look up an attached engine + * @pid: &struct pid pointer representing thread to attach to + * @flags: flag bits combined with OR, see utrace_attach_task() + * @ops: callback table for new engine + * @data: engine private data pointer + * + * This is the same as utrace_attach_task(), but takes a &struct pid + * pointer rather than a &struct task_struct pointer. The caller must + * hold a ref on @pid, but does not need to worry about the task + * staying valid. If it's been reaped so that @pid points nowhere, + * then this call returns -%ESRCH. + */ +struct utrace_engine *utrace_attach_pid( + struct pid *pid, int flags, + const struct utrace_engine_ops *ops, void *data) +{ + struct utrace_engine *engine = ERR_PTR(-ESRCH); + struct task_struct *task = get_pid_task(pid, PIDTYPE_PID); + if (task) { + engine = utrace_attach_task(task, flags, ops, data); + put_task_struct(task); + } + return engine; +} +EXPORT_SYMBOL_GPL(utrace_attach_pid); + +/* + * When an engine is detached, the target thread may still see it and + * make callbacks until it quiesces. We install a special ops vector + * with these two callbacks. When the target thread quiesces, it can + * safely free the engine itself. For any event we will always get + * the report_quiesce() callback first, so we only need this one + * pointer to be set. The only exception is report_reap(), so we + * supply that callback too. + */ +static u32 utrace_detached_quiesce(u32 action, struct utrace_engine *engine, + unsigned long event) +{ + return UTRACE_DETACH; +} + +static void utrace_detached_reap(struct utrace_engine *engine, + struct task_struct *task) +{ +} + +static const struct utrace_engine_ops utrace_detached_ops = { + .report_quiesce = &utrace_detached_quiesce, + .report_reap = &utrace_detached_reap +}; + +/* + * The caller has to hold a ref on the engine. If the attached flag is + * true (all but utrace_barrier() calls), the engine is supposed to be + * attached. If the attached flag is false (utrace_barrier() only), + * then return -ERESTARTSYS for an engine marked for detach but not yet + * fully detached. The task pointer can be invalid if the engine is + * detached. + * + * Get the utrace lock for the target task. + * Returns the struct if locked, or ERR_PTR(-errno). + * + * This has to be robust against races with: + * utrace_control(target, UTRACE_DETACH) calls + * UTRACE_DETACH after reports + * utrace_report_death + * utrace_release_task + */ +static struct utrace *get_utrace_lock(struct task_struct *target, + struct utrace_engine *engine, + bool attached) + __acquires(utrace->lock) +{ + struct utrace *utrace; + + rcu_read_lock(); + + /* + * If this engine was already detached, bail out before we look at + * the task_struct pointer at all. If it's detached after this + * check, then RCU is still keeping this task_struct pointer valid. + * + * The ops pointer is NULL when the engine is fully detached. + * It's &utrace_detached_ops when it's marked detached but still + * on the list. In the latter case, utrace_barrier() still works, + * since the target might be in the middle of an old callback. + */ + if (unlikely(!engine->ops)) { + rcu_read_unlock(); + return ERR_PTR(-ESRCH); + } + + if (unlikely(engine->ops == &utrace_detached_ops)) { + rcu_read_unlock(); + return attached ? ERR_PTR(-ESRCH) : ERR_PTR(-ERESTARTSYS); + } + + utrace = task_utrace_struct(target); + spin_lock(&utrace->lock); + if (unlikely(utrace->reap) || unlikely(!engine->ops) || + unlikely(engine->ops == &utrace_detached_ops)) { + /* + * By the time we got the utrace lock, + * it had been reaped or detached already. + */ + spin_unlock(&utrace->lock); + utrace = ERR_PTR(-ESRCH); + if (!attached && engine->ops == &utrace_detached_ops) + utrace = ERR_PTR(-ERESTARTSYS); + } + rcu_read_unlock(); + + return utrace; +} + +/* + * Now that we don't hold any locks, run through any + * detached engines and free their references. Each + * engine had one implicit ref while it was attached. + */ +static void put_detached_list(struct list_head *list) +{ + struct utrace_engine *engine, *next; + list_for_each_entry_safe(engine, next, list, entry) { + list_del_init(&engine->entry); + utrace_engine_put(engine); + } +} + +/* + * We use an extra bit in utrace_engine.flags past the event bits, + * to record whether the engine is keeping the target thread stopped. + * + * This bit is set in task_struct.utrace_flags whenever it is set in any + * engine's flags. Only utrace_reset() resets it in utrace_flags. + */ +#define ENGINE_STOP (1UL << _UTRACE_NEVENTS) + +static void mark_engine_wants_stop(struct task_struct *task, + struct utrace_engine *engine) +{ + engine->flags |= ENGINE_STOP; + task->utrace_flags |= ENGINE_STOP; +} + +static void clear_engine_wants_stop(struct utrace_engine *engine) +{ + engine->flags &= ~ENGINE_STOP; +} + +static bool engine_wants_stop(struct utrace_engine *engine) +{ + return (engine->flags & ENGINE_STOP) != 0; +} + +/** + * utrace_set_events - choose which event reports a tracing engine gets + * @target: thread to affect + * @engine: attached engine to affect + * @events: new event mask + * + * This changes the set of events for which @engine wants callbacks made. + * + * This fails with -%EALREADY and does nothing if you try to clear + * %UTRACE_EVENT(%DEATH) when the @report_death callback may already have + * begun, or if you try to newly set %UTRACE_EVENT(%DEATH) or + * %UTRACE_EVENT(%QUIESCE) when @target is already dead or dying. + * + * This fails with -%ESRCH if you try to clear %UTRACE_EVENT(%REAP) when + * the @report_reap callback may already have begun, or when @target has + * already been detached, including forcible detach on reaping. + * + * If @target was stopped before the call, then after a successful call, + * no event callbacks not requested in @events will be made; if + * %UTRACE_EVENT(%QUIESCE) is included in @events, then a + * @report_quiesce callback will be made when @target resumes. + * + * If @target was not stopped and @events excludes some bits that were + * set before, this can return -%EINPROGRESS to indicate that @target + * may have been making some callback to @engine. When this returns + * zero, you can be sure that no event callbacks you've disabled in + * @events can be made. If @events only sets new bits that were not set + * before on @engine, then -%EINPROGRESS will never be returned. + * + * To synchronize after an -%EINPROGRESS return, see utrace_barrier(). + * + * When @target is @current, -%EINPROGRESS is not returned. But note + * that a newly-created engine will not receive any callbacks related to + * an event notification already in progress. This call enables @events + * callbacks to be made as soon as @engine becomes eligible for any + * callbacks, see utrace_attach_task(). + * + * These rules provide for coherent synchronization based on %UTRACE_STOP, + * even when %SIGKILL is breaking its normal simple rules. + */ +int utrace_set_events(struct task_struct *target, + struct utrace_engine *engine, + unsigned long events) +{ + struct utrace *utrace; + unsigned long old_flags, old_utrace_flags; + int ret = -EALREADY; + + /* + * We just ignore the internal bit, so callers can use + * engine->flags to seed bitwise ops for our argument. + */ + events &= ~ENGINE_STOP; + + utrace = get_utrace_lock(target, engine, true); + if (unlikely(IS_ERR(utrace))) + return PTR_ERR(utrace); + + old_utrace_flags = target->utrace_flags; + old_flags = engine->flags & ~ENGINE_STOP; + + /* + * If utrace_report_death() is already progress now, + * it's too late to clear the death event bits. + */ + if (((old_flags & ~events) & _UTRACE_DEATH_EVENTS) && utrace->death) + goto unlock; + + /* + * When setting these flags, it's essential that we really + * synchronize with exit_notify(). They cannot be set after + * exit_notify() takes the tasklist_lock. By holding the read + * lock here while setting the flags, we ensure that the calls + * to tracehook_notify_death() and tracehook_report_death() will + * see the new flags. This ensures that utrace_release_task() + * knows positively that utrace_report_death() will be called or + * that it won't. + */ + if ((events & ~old_flags) & _UTRACE_DEATH_EVENTS) { + read_lock(&tasklist_lock); + if (unlikely(target->exit_state)) { + read_unlock(&tasklist_lock); + goto unlock; + } + target->utrace_flags |= events; + read_unlock(&tasklist_lock); + } + + engine->flags = events | (engine->flags & ENGINE_STOP); + target->utrace_flags |= events; + + if ((events & UTRACE_EVENT_SYSCALL) && + !(old_utrace_flags & UTRACE_EVENT_SYSCALL)) + set_tsk_thread_flag(target, TIF_SYSCALL_TRACE); + + ret = 0; + if ((old_flags & ~events) && target != current && + !task_is_stopped_or_traced(target) && !target->exit_state) { + /* + * This barrier ensures that our engine->flags changes + * have hit before we examine utrace->reporting, + * pairing with the barrier in start_callback(). If + * @target has not yet hit finish_callback() to clear + * utrace->reporting, we might be in the middle of a + * callback to @engine. + */ + smp_mb(); + if (utrace->reporting == engine) + ret = -EINPROGRESS; + } +unlock: + spin_unlock(&utrace->lock); + + return ret; +} +EXPORT_SYMBOL_GPL(utrace_set_events); + +/* + * Asynchronously mark an engine as being detached. + * + * This must work while the target thread races with us doing + * start_callback(), defined below. It uses smp_rmb() between checking + * @engine->flags and using @engine->ops. Here we change @engine->ops + * first, then use smp_wmb() before changing @engine->flags. This ensures + * it can check the old flags before using the old ops, or check the old + * flags before using the new ops, or check the new flags before using the + * new ops, but can never check the new flags before using the old ops. + * Hence, utrace_detached_ops might be used with any old flags in place. + * It has report_quiesce() and report_reap() callbacks to handle all cases. + */ +static void mark_engine_detached(struct utrace_engine *engine) +{ + engine->ops = &utrace_detached_ops; + smp_wmb(); + engine->flags = UTRACE_EVENT(QUIESCE); +} + +/* + * Get @target to stop and return true if it is already stopped now. + * If we return false, it will make some event callback soonish. + * Called with @utrace locked. + */ +static bool utrace_do_stop(struct task_struct *target, struct utrace *utrace) +{ + if (task_is_stopped(target)) { + /* + * Stopped is considered quiescent; when it wakes up, it will + * go through utrace_finish_stop() before doing anything else. + */ + spin_lock_irq(&target->sighand->siglock); + if (likely(task_is_stopped(target))) + __set_task_state(target, TASK_TRACED); + spin_unlock_irq(&target->sighand->siglock); + } else if (utrace->resume > UTRACE_REPORT) { + utrace->resume = UTRACE_REPORT; + set_notify_resume(target); + } + + return task_is_traced(target); +} + +/* + * If the target is not dead it should not be in tracing + * stop any more. Wake it unless it's in job control stop. + */ +static void utrace_wakeup(struct task_struct *target, struct utrace *utrace) +{ + lockdep_assert_held(&utrace->lock); + spin_lock_irq(&target->sighand->siglock); + if (target->signal->flags & SIGNAL_STOP_STOPPED || + target->signal->group_stop_count) + target->state = TASK_STOPPED; + else + wake_up_state(target, __TASK_TRACED); + spin_unlock_irq(&target->sighand->siglock); +} + +/* + * This is called when there might be some detached engines on the list or + * some stale bits in @task->utrace_flags. Clean them up and recompute the + * flags. Returns true if we're now fully detached. + * + * Called with @utrace->lock held, returns with it released. + * After this returns, @utrace might be freed if everything detached. + */ +static bool utrace_reset(struct task_struct *task, struct utrace *utrace) + __releases(utrace->lock) +{ + struct utrace_engine *engine, *next; + unsigned long flags = 0; + LIST_HEAD(detached); + + splice_attaching(utrace); + + /* + * Update the set of events of interest from the union + * of the interests of the remaining tracing engines. + * For any engine marked detached, remove it from the list. + * We'll collect them on the detached list. + */ + list_for_each_entry_safe(engine, next, &utrace->attached, entry) { + if (engine->ops == &utrace_detached_ops) { + engine->ops = NULL; + list_move(&engine->entry, &detached); + } else { + flags |= engine->flags | UTRACE_EVENT(REAP); + } + } + + if (task->exit_state) { + /* + * Once it's already dead, we never install any flags + * except REAP. When ->exit_state is set and events + * like DEATH are not set, then they never can be set. + * This ensures that utrace_release_task() knows + * positively that utrace_report_death() can never run. + */ + BUG_ON(utrace->death); + flags &= UTRACE_EVENT(REAP); + } else if (!(flags & UTRACE_EVENT_SYSCALL) && + test_tsk_thread_flag(task, TIF_SYSCALL_TRACE)) { + clear_tsk_thread_flag(task, TIF_SYSCALL_TRACE); + } + + if (!flags) { + /* + * No more engines, cleared out the utrace. + */ + utrace->resume = UTRACE_RESUME; + utrace->signal_handler = 0; + } + + /* + * If no more engines want it stopped, wake it up. + */ + if (task_is_traced(task) && !(flags & ENGINE_STOP)) + utrace_wakeup(task, utrace); + + /* + * In theory spin_lock() doesn't imply rcu_read_lock(). + * Once we clear ->utrace_flags this task_struct can go away + * because tracehook_prepare_release_task() path does not take + * utrace->lock when ->utrace_flags == 0. + */ + rcu_read_lock(); + task->utrace_flags = flags; + spin_unlock(&utrace->lock); + rcu_read_unlock(); + + put_detached_list(&detached); + + return !flags; +} + +void utrace_finish_stop(void) +{ + /* + * If we were task_is_traced() and then SIGKILL'ed, make + * sure we do nothing until the tracer drops utrace->lock. + */ + if (unlikely(__fatal_signal_pending(current))) { + struct utrace *utrace = task_utrace_struct(current); + spin_unlock_wait(&utrace->lock); + } +} + +/* + * Perform %UTRACE_STOP, i.e. block in TASK_TRACED until woken up. + * @task == current, @utrace == current->utrace, which is not locked. + * Return true if we were woken up by SIGKILL even though some utrace + * engine may still want us to stay stopped. + */ +static void utrace_stop(struct task_struct *task, struct utrace *utrace, + enum utrace_resume_action action) +{ +relock: + spin_lock(&utrace->lock); + + if (action < utrace->resume) { + /* + * Ensure a reporting pass when we're resumed. + */ + utrace->resume = action; + if (action == UTRACE_INTERRUPT) + set_thread_flag(TIF_SIGPENDING); + else + set_thread_flag(TIF_NOTIFY_RESUME); + } + + /* + * If the ENGINE_STOP bit is clear in utrace_flags, that means + * utrace_reset() ran after we processed some UTRACE_STOP return + * values from callbacks to get here. If all engines have detached + * or resumed us, we don't stop. This check doesn't require + * siglock, but it should follow the interrupt/report bookkeeping + * steps (this can matter for UTRACE_RESUME but not UTRACE_DETACH). + */ + if (unlikely(!(task->utrace_flags & ENGINE_STOP))) { + utrace_reset(task, utrace); + if (task->utrace_flags & ENGINE_STOP) + goto relock; + return; + } + + /* + * The siglock protects us against signals. As well as SIGKILL + * waking us up, we must synchronize with the signal bookkeeping + * for stop signals and SIGCONT. + */ + spin_lock_irq(&task->sighand->siglock); + + if (unlikely(__fatal_signal_pending(task))) { + spin_unlock_irq(&task->sighand->siglock); + spin_unlock(&utrace->lock); + return; + } + + __set_current_state(TASK_TRACED); + + /* + * If there is a group stop in progress, + * we must participate in the bookkeeping. + */ + if (unlikely(task->signal->group_stop_count) && + !--task->signal->group_stop_count) + task->signal->flags = SIGNAL_STOP_STOPPED; + + spin_unlock_irq(&task->sighand->siglock); + spin_unlock(&utrace->lock); + + /* + * If ptrace is among the reasons for this stop, do its + * notification now. This could not just be done in + * ptrace's own event report callbacks because it has to + * be done after we are in TASK_TRACED. This makes the + * synchronization with ptrace_do_wait() work right. + * + * It's only because of the bad old overloading of the do_wait() + * logic for handling ptrace stops that we need this special case + * here. One day we will clean up ptrace so it does not need to + * work this way. New things that are designed sensibly don't need + * a wakeup that synchronizes with tasklist_lock and ->state, so + * the proper utrace API does not try to support this weirdness. + */ + ptrace_notify_stop(task); + + schedule(); + + utrace_finish_stop(); + + /* + * While in TASK_TRACED, we were considered "frozen enough". + * Now that we woke up, it's crucial if we're supposed to be + * frozen that we freeze now before running anything substantial. + */ + try_to_freeze(); + + /* + * While we were in TASK_TRACED, complete_signal() considered + * us "uninterested" in signal wakeups. Now make sure our + * TIF_SIGPENDING state is correct for normal running. + */ + spin_lock_irq(&task->sighand->siglock); + recalc_sigpending(); + spin_unlock_irq(&task->sighand->siglock); +} + +/* + * Called by release_task() with @reap set to true. + * Called by utrace_report_death() with @reap set to false. + * On reap, make report_reap callbacks and clean out @utrace + * unless still making callbacks. On death, update bookkeeping + * and handle the reap work if release_task() came in first. + */ +void utrace_maybe_reap(struct task_struct *target, struct utrace *utrace, + bool reap) +{ + struct utrace_engine *engine, *next; + struct list_head attached; + + spin_lock(&utrace->lock); + + if (reap) { + /* + * If the target will do some final callbacks but hasn't + * finished them yet, we know because it clears these event + * bits after it's done. Instead of cleaning up here and + * requiring utrace_report_death() to cope with it, we + * delay the REAP report and the teardown until after the + * target finishes its death reports. + */ + utrace->reap = 1; + + if (target->utrace_flags & _UTRACE_DEATH_EVENTS) { + spin_unlock(&utrace->lock); + return; + } + } else { + /* + * After we unlock with this flag clear, any competing + * utrace_control/utrace_set_events calls know that we've + * finished our callbacks and any detach bookkeeping. + */ + utrace->death = 0; + + if (!utrace->reap) { + /* + * We're just dead, not reaped yet. This will + * reset @target->utrace_flags so the later call + * with @reap set won't hit the check above. + */ + utrace_reset(target, utrace); + return; + } + } + + /* + * utrace_add_engine() checks ->utrace_flags != 0. Since + * @utrace->reap is set, nobody can set or clear UTRACE_EVENT(REAP) + * in @engine->flags or change @engine->ops and nobody can change + * @utrace->attached after we drop the lock. + */ + target->utrace_flags = 0; + + /* + * We clear out @utrace->attached before we drop the lock so + * that find_matching_engine() can't come across any old engine + * while we are busy tearing it down. + */ + list_replace_init(&utrace->attached, &attached); + list_splice_tail_init(&utrace->attaching, &attached); + + spin_unlock(&utrace->lock); + + list_for_each_entry_safe(engine, next, &attached, entry) { + if (engine->flags & UTRACE_EVENT(REAP)) + engine->ops->report_reap(engine, target); + + engine->ops = NULL; + engine->flags = 0; + list_del_init(&engine->entry); + + utrace_engine_put(engine); + } +} + +/* + * You can't do anything to a dead task but detach it. + * If release_task() has been called, you can't do that. + * + * On the exit path, DEATH and QUIESCE event bits are set only + * before utrace_report_death() has taken the lock. At that point, + * the death report will come soon, so disallow detach until it's + * done. This prevents us from racing with it detaching itself. + * + * Called only when @target->exit_state is nonzero. + */ +static inline int utrace_control_dead(struct task_struct *target, + struct utrace *utrace, + enum utrace_resume_action action) +{ + lockdep_assert_held(&utrace->lock); + + if (action != UTRACE_DETACH || unlikely(utrace->reap)) + return -ESRCH; + + if (unlikely(utrace->death)) + /* + * We have already started the death report. We can't + * prevent the report_death and report_reap callbacks, + * so tell the caller they will happen. + */ + return -EALREADY; + + return 0; +} + +/** + * utrace_control - control a thread being traced by a tracing engine + * @target: thread to affect + * @engine: attached engine to affect + * @action: &enum utrace_resume_action for thread to do + * + * This is how a tracing engine asks a traced thread to do something. + * This call is controlled by the @action argument, which has the + * same meaning as the &enum utrace_resume_action value returned by + * event reporting callbacks. + * + * If @target is already dead (@target->exit_state nonzero), + * all actions except %UTRACE_DETACH fail with -%ESRCH. + * + * The following sections describe each option for the @action argument. + * + * UTRACE_DETACH: + * + * After this, the @engine data structure is no longer accessible, + * and the thread might be reaped. The thread will start running + * again if it was stopped and no longer has any attached engines + * that want it stopped. + * + * If the @report_reap callback may already have begun, this fails + * with -%ESRCH. If the @report_death callback may already have + * begun, this fails with -%EALREADY. + * + * If @target is not already stopped, then a callback to this engine + * might be in progress or about to start on another CPU. If so, + * then this returns -%EINPROGRESS; the detach happens as soon as + * the pending callback is finished. To synchronize after an + * -%EINPROGRESS return, see utrace_barrier(). + * + * If @target is properly stopped before utrace_control() is called, + * then after successful return it's guaranteed that no more callbacks + * to the @engine->ops vector will be made. + * + * The only exception is %SIGKILL (and exec or group-exit by another + * thread in the group), which can cause asynchronous @report_death + * and/or @report_reap callbacks even when %UTRACE_STOP was used. + * (In that event, this fails with -%ESRCH or -%EALREADY, see above.) + * + * UTRACE_STOP: + * + * This asks that @target stop running. This returns 0 only if + * @target is already stopped, either for tracing or for job + * control. Then @target will remain stopped until another + * utrace_control() call is made on @engine; @target can be woken + * only by %SIGKILL (or equivalent, such as exec or termination by + * another thread in the same thread group). + * + * This returns -%EINPROGRESS if @target is not already stopped. + * Then the effect is like %UTRACE_REPORT. A @report_quiesce or + * @report_signal callback will be made soon. Your callback can + * then return %UTRACE_STOP to keep @target stopped. + * + * This does not interrupt system calls in progress, including ones + * that sleep for a long time. For that, use %UTRACE_INTERRUPT. + * To interrupt system calls and then keep @target stopped, your + * @report_signal callback can return %UTRACE_STOP. + * + * UTRACE_RESUME: + * + * Just let @target continue running normally, reversing the effect + * of a previous %UTRACE_STOP. If another engine is keeping @target + * stopped, then it remains stopped until all engines let it resume. + * If @target was not stopped, this has no effect. + * + * UTRACE_REPORT: + * + * This is like %UTRACE_RESUME, but also ensures that there will be + * a @report_quiesce or @report_signal callback made soon. If + * @target had been stopped, then there will be a callback before it + * resumes running normally. If another engine is keeping @target + * stopped, then there might be no callbacks until all engines let + * it resume. + * + * Since this is meaningless unless @report_quiesce callbacks will + * be made, it returns -%EINVAL if @engine lacks %UTRACE_EVENT(%QUIESCE). + * + * UTRACE_INTERRUPT: + * + * This is like %UTRACE_REPORT, but ensures that @target will make a + * @report_signal callback before it resumes or delivers signals. + * If @target was in a system call or about to enter one, work in + * progress will be interrupted as if by %SIGSTOP. If another + * engine is keeping @target stopped, then there might be no + * callbacks until all engines let it resume. + * + * This gives @engine an opportunity to introduce a forced signal + * disposition via its @report_signal callback. + * + * UTRACE_SINGLESTEP: + * + * It's invalid to use this unless arch_has_single_step() returned true. + * This is like %UTRACE_RESUME, but resumes for one user instruction only. + * + * Note that passing %UTRACE_SINGLESTEP or %UTRACE_BLOCKSTEP to + * utrace_control() or returning it from an event callback alone does + * not necessarily ensure that stepping will be enabled. If there are + * more callbacks made to any engine before returning to user mode, + * then the resume action is chosen only by the last set of callbacks. + * To be sure, enable %UTRACE_EVENT(%QUIESCE) and look for the + * @report_quiesce callback with a zero event mask, or the + * @report_signal callback with %UTRACE_SIGNAL_REPORT. + * + * Since this is not robust unless @report_quiesce callbacks will + * be made, it returns -%EINVAL if @engine lacks %UTRACE_EVENT(%QUIESCE). + * + * UTRACE_BLOCKSTEP: + * + * It's invalid to use this unless arch_has_block_step() returned true. + * This is like %UTRACE_SINGLESTEP, but resumes for one whole basic + * block of user instructions. + * + * Since this is not robust unless @report_quiesce callbacks will + * be made, it returns -%EINVAL if @engine lacks %UTRACE_EVENT(%QUIESCE). + * + * %UTRACE_BLOCKSTEP devolves to %UTRACE_SINGLESTEP when another + * tracing engine is using %UTRACE_SINGLESTEP at the same time. + */ +int utrace_control(struct task_struct *target, + struct utrace_engine *engine, + enum utrace_resume_action action) +{ + struct utrace *utrace; + bool reset; + int ret; + + if (unlikely(action >= UTRACE_RESUME_MAX)) { + WARN(1, "invalid action argument to utrace_control()!"); + return -EINVAL; + } + + /* + * This is a sanity check for a programming error in the caller. + * Their request can only work properly in all cases by relying on + * a follow-up callback, but they didn't set one up! This check + * doesn't do locking, but it shouldn't matter. The caller has to + * be synchronously sure the callback is set up to be operating the + * interface properly. + */ + if (action >= UTRACE_REPORT && action < UTRACE_RESUME && + unlikely(!(engine->flags & UTRACE_EVENT(QUIESCE)))) { + WARN(1, "utrace_control() with no QUIESCE callback in place!"); + return -EINVAL; + } + + utrace = get_utrace_lock(target, engine, true); + if (unlikely(IS_ERR(utrace))) + return PTR_ERR(utrace); + + reset = task_is_traced(target); + ret = 0; + + /* + * ->exit_state can change under us, this doesn't matter. + * We do not care about ->exit_state in fact, but we do + * care about ->reap and ->death. If either flag is set, + * we must also see ->exit_state != 0. + */ + if (unlikely(target->exit_state)) { + ret = utrace_control_dead(target, utrace, action); + if (ret) { + spin_unlock(&utrace->lock); + return ret; + } + reset = true; + } + + switch (action) { + case UTRACE_STOP: + mark_engine_wants_stop(target, engine); + if (!reset && !utrace_do_stop(target, utrace)) + ret = -EINPROGRESS; + reset = false; + break; + + case UTRACE_DETACH: + if (engine_wants_stop(engine)) + target->utrace_flags &= ~ENGINE_STOP; + mark_engine_detached(engine); + reset = reset || utrace_do_stop(target, utrace); + if (!reset) { + /* + * As in utrace_set_events(), this barrier ensures + * that our engine->flags changes have hit before we + * examine utrace->reporting, pairing with the barrier + * in start_callback(). If @target has not yet hit + * finish_callback() to clear utrace->reporting, we + * might be in the middle of a callback to @engine. + */ + smp_mb(); + if (utrace->reporting == engine) + ret = -EINPROGRESS; + } + break; + + case UTRACE_RESUME: + /* + * This and all other cases imply resuming if stopped. + * There might not be another report before it just + * resumes, so make sure single-step is not left set. + */ + clear_engine_wants_stop(engine); + if (likely(reset)) + user_disable_single_step(target); + break; + + case UTRACE_BLOCKSTEP: + /* + * Resume from stopped, step one block. + * We fall through to treat it like UTRACE_SINGLESTEP. + */ + if (unlikely(!arch_has_block_step())) { + WARN(1, "UTRACE_BLOCKSTEP when !arch_has_block_step()"); + action = UTRACE_SINGLESTEP; + } + + case UTRACE_SINGLESTEP: + /* + * Resume from stopped, step one instruction. + * We fall through to the UTRACE_REPORT case. + */ + if (unlikely(!arch_has_single_step())) { + WARN(1, + "UTRACE_SINGLESTEP when !arch_has_single_step()"); + reset = false; + ret = -EOPNOTSUPP; + break; + } + + case UTRACE_REPORT: + /* + * Make the thread call tracehook_notify_resume() soon. + * But don't bother if it's already been interrupted. + * In that case, utrace_get_signal() will be reporting soon. + */ + clear_engine_wants_stop(engine); + if (action < utrace->resume) { + utrace->resume = action; + set_notify_resume(target); + } + break; + + case UTRACE_INTERRUPT: + /* + * Make the thread call tracehook_get_signal() soon. + */ + clear_engine_wants_stop(engine); + if (utrace->resume == UTRACE_INTERRUPT) + break; + utrace->resume = UTRACE_INTERRUPT; + + /* + * If it's not already stopped, interrupt it now. We need + * the siglock here in case it calls recalc_sigpending() + * and clears its own TIF_SIGPENDING. By taking the lock, + * we've serialized any later recalc_sigpending() after our + * setting of utrace->resume to force it on. + */ + if (reset) { + /* + * This is really just to keep the invariant that + * TIF_SIGPENDING is set with UTRACE_INTERRUPT. + * When it's stopped, we know it's always going + * through utrace_get_signal() and will recalculate. + */ + set_tsk_thread_flag(target, TIF_SIGPENDING); + } else { + struct sighand_struct *sighand; + unsigned long irqflags; + sighand = lock_task_sighand(target, &irqflags); + if (likely(sighand)) { + signal_wake_up(target, 0); + unlock_task_sighand(target, &irqflags); + } + } + break; + + default: + BUG(); /* We checked it on entry. */ + } + + /* + * Let the thread resume running. If it's not stopped now, + * there is nothing more we need to do. + */ + if (reset) + utrace_reset(target, utrace); + else + spin_unlock(&utrace->lock); + + return ret; +} +EXPORT_SYMBOL_GPL(utrace_control); + +/** + * utrace_barrier - synchronize with simultaneous tracing callbacks + * @target: thread to affect + * @engine: engine to affect (can be detached) + * + * This blocks while @target might be in the midst of making a callback to + * @engine. It can be interrupted by signals and will return -%ERESTARTSYS. + * A return value of zero means no callback from @target to @engine was + * in progress. Any effect of its return value (such as %UTRACE_STOP) has + * already been applied to @engine. + * + * It's not necessary to keep the @target pointer alive for this call. + * It's only necessary to hold a ref on @engine. This will return + * safely even if @target has been reaped and has no task refs. + * + * A successful return from utrace_barrier() guarantees its ordering + * with respect to utrace_set_events() and utrace_control() calls. If + * @target was not properly stopped, event callbacks just disabled might + * still be in progress; utrace_barrier() waits until there is no chance + * an unwanted callback can be in progress. + */ +int utrace_barrier(struct task_struct *target, struct utrace_engine *engine) +{ + struct utrace *utrace; + int ret = -ERESTARTSYS; + + if (unlikely(target == current)) + return 0; + + do { + utrace = get_utrace_lock(target, engine, false); + if (unlikely(IS_ERR(utrace))) { + ret = PTR_ERR(utrace); + if (ret != -ERESTARTSYS) + break; + } else { + /* + * All engine state changes are done while + * holding the lock, i.e. before we get here. + * Since we have the lock, we only need to + * worry about @target making a callback. + * When it has entered start_callback() but + * not yet gotten to finish_callback(), we + * will see utrace->reporting == @engine. + * When @target doesn't take the lock, it uses + * barriers to order setting utrace->reporting + * before it examines the engine state. + */ + if (utrace->reporting != engine) + ret = 0; + spin_unlock(&utrace->lock); + if (!ret) + break; + } + schedule_timeout_interruptible(1); + } while (!signal_pending(current)); + + return ret; +} +EXPORT_SYMBOL_GPL(utrace_barrier); + +/* + * This is local state used for reporting loops, perhaps optimized away. + */ +struct utrace_report { + u32 result; + enum utrace_resume_action action; + enum utrace_resume_action resume_action; + bool detaches; + bool spurious; +}; + +#define INIT_REPORT(var) \ + struct utrace_report var = { \ + .action = UTRACE_RESUME, \ + .resume_action = UTRACE_RESUME, \ + .spurious = true \ + } + +/* + * We are now making the report, so clear the flag saying we need one. + * When there is a new attach, ->pending_attach is set just so we will + * know to do splice_attaching() here before the callback loop. + */ +static enum utrace_resume_action start_report(struct utrace *utrace) +{ + enum utrace_resume_action resume = utrace->resume; + if (utrace->pending_attach || + (resume > UTRACE_INTERRUPT && resume < UTRACE_RESUME)) { + spin_lock(&utrace->lock); + splice_attaching(utrace); + resume = utrace->resume; + if (resume > UTRACE_INTERRUPT) + utrace->resume = UTRACE_RESUME; + spin_unlock(&utrace->lock); + } + return resume; +} + +static inline void finish_report_reset(struct task_struct *task, + struct utrace *utrace, + struct utrace_report *report) +{ + if (unlikely(report->spurious || report->detaches)) { + spin_lock(&utrace->lock); + if (utrace_reset(task, utrace)) + report->action = UTRACE_RESUME; + } +} + +/* + * Complete a normal reporting pass, pairing with a start_report() call. + * This handles any UTRACE_DETACH or UTRACE_REPORT or UTRACE_INTERRUPT + * returns from engine callbacks. If @will_not_stop is true and any + * engine's last callback used UTRACE_STOP, we do UTRACE_REPORT here to + * ensure we stop before user mode. If there were no callbacks made, it + * will recompute @task->utrace_flags to avoid another false-positive. + */ +static void finish_report(struct task_struct *task, struct utrace *utrace, + struct utrace_report *report, bool will_not_stop) +{ + enum utrace_resume_action resume = report->action; + + if (resume == UTRACE_STOP) + resume = will_not_stop ? UTRACE_REPORT : UTRACE_RESUME; + + if (resume < utrace->resume) { + spin_lock(&utrace->lock); + utrace->resume = resume; + if (resume == UTRACE_INTERRUPT) + set_tsk_thread_flag(task, TIF_SIGPENDING); + else + set_tsk_thread_flag(task, TIF_NOTIFY_RESUME); + spin_unlock(&utrace->lock); + } + + finish_report_reset(task, utrace, report); +} + +static void finish_callback_report(struct task_struct *task, + struct utrace *utrace, + struct utrace_report *report, + struct utrace_engine *engine, + enum utrace_resume_action action) +{ + if (action == UTRACE_DETACH) { + /* + * By holding the lock here, we make sure that + * utrace_barrier() (really get_utrace_lock()) sees the + * effect of this detach. Otherwise utrace_barrier() could + * return 0 after this callback had returned UTRACE_DETACH. + * This way, a 0 return is an unambiguous indicator that any + * callback returning UTRACE_DETACH has indeed caused detach. + */ + spin_lock(&utrace->lock); + engine->ops = &utrace_detached_ops; + spin_unlock(&utrace->lock); + } + + /* + * If utrace_control() was used, treat that like UTRACE_DETACH here. + */ + if (engine->ops == &utrace_detached_ops) { + report->detaches = true; + return; + } + + if (action < report->action) + report->action = action; + + if (action != UTRACE_STOP) { + if (action < report->resume_action) + report->resume_action = action; + + if (engine_wants_stop(engine)) { + spin_lock(&utrace->lock); + clear_engine_wants_stop(engine); + spin_unlock(&utrace->lock); + } + + return; + } + + if (!engine_wants_stop(engine)) { + spin_lock(&utrace->lock); + /* + * If utrace_control() came in and detached us + * before we got the lock, we must not stop now. + */ + if (unlikely(engine->ops == &utrace_detached_ops)) + report->detaches = true; + else + mark_engine_wants_stop(task, engine); + spin_unlock(&utrace->lock); + } +} + +/* + * Apply the return value of one engine callback to @report. + * Returns true if @engine detached and should not get any more callbacks. + */ +static bool finish_callback(struct task_struct *task, struct utrace *utrace, + struct utrace_report *report, + struct utrace_engine *engine, + u32 ret) +{ + report->result = ret & ~UTRACE_RESUME_MASK; + finish_callback_report(task, utrace, report, engine, + utrace_resume_action(ret)); + + /* + * Now that we have applied the effect of the return value, + * clear this so that utrace_barrier() can stop waiting. + * A subsequent utrace_control() can stop or resume @engine + * and know this was ordered after its callback's action. + * + * We don't need any barriers here because utrace_barrier() + * takes utrace->lock. If we touched engine->flags above, + * the lock guaranteed this change was before utrace_barrier() + * examined utrace->reporting. + */ + utrace->reporting = NULL; + + /* + * We've just done an engine callback. These are allowed to sleep, + * though all well-behaved ones restrict that to blocking kalloc() + * or quickly-acquired mutex_lock() and the like. This is a good + * place to make sure tracing engines don't introduce too much + * latency under voluntary preemption. + */ + might_sleep(); + + return engine->ops == &utrace_detached_ops; +} + +/* + * Start the callbacks for @engine to consider @event (a bit mask). + * This makes the report_quiesce() callback first. If @engine wants + * a specific callback for @event, we return the ops vector to use. + * If not, we return NULL. The return value from the ops->callback + * function called should be passed to finish_callback(). + */ +static const struct utrace_engine_ops *start_callback( + struct utrace *utrace, struct utrace_report *report, + struct utrace_engine *engine, struct task_struct *task, + unsigned long event) +{ + const struct utrace_engine_ops *ops; + unsigned long want; + + /* + * This barrier ensures that we've set utrace->reporting before + * we examine engine->flags or engine->ops. utrace_barrier() + * relies on this ordering to indicate that the effect of any + * utrace_control() and utrace_set_events() calls is in place + * by the time utrace->reporting can be seen to be NULL. + */ + utrace->reporting = engine; + smp_mb(); + + /* + * This pairs with the barrier in mark_engine_detached(). + * It makes sure that we never see the old ops vector with + * the new flags, in case the original vector had no report_quiesce. + */ + want = engine->flags; + smp_rmb(); + ops = engine->ops; + + if (want & UTRACE_EVENT(QUIESCE)) { + if (finish_callback(task, utrace, report, engine, + (*ops->report_quiesce)(report->action, + engine, event))) + return NULL; + + /* + * finish_callback() reset utrace->reporting after the + * quiesce callback. Now we set it again (as above) + * before re-examining engine->flags, which could have + * been changed synchronously by ->report_quiesce or + * asynchronously by utrace_control() or utrace_set_events(). + */ + utrace->reporting = engine; + smp_mb(); + want = engine->flags; + } + + if (want & ENGINE_STOP) + report->action = UTRACE_STOP; + + if (want & event) { + report->spurious = false; + return ops; + } + + utrace->reporting = NULL; + return NULL; +} + +/* + * Do a normal reporting pass for engines interested in @event. + * @callback is the name of the member in the ops vector, and remaining + * args are the extras it takes after the standard three args. + */ +#define REPORT_CALLBACKS(rev, task, utrace, report, event, callback, ...) \ + do { \ + struct utrace_engine *engine; \ + const struct utrace_engine_ops *ops; \ + list_for_each_entry##rev(engine, &utrace->attached, entry) { \ + ops = start_callback(utrace, report, engine, task, \ + event); \ + if (!ops) \ + continue; \ + finish_callback(task, utrace, report, engine, \ + (*ops->callback)(__VA_ARGS__)); \ + } \ + } while (0) +#define REPORT(task, utrace, report, event, callback, ...) \ + do { \ + start_report(utrace); \ + REPORT_CALLBACKS(, task, utrace, report, event, callback, \ + (report)->action, engine, ## __VA_ARGS__); \ + finish_report(task, utrace, report, true); \ + } while (0) + +/* + * Called iff UTRACE_EVENT(EXEC) flag is set. + */ +void utrace_report_exec(struct linux_binfmt *fmt, struct linux_binprm *bprm, + struct pt_regs *regs) +{ + struct task_struct *task = current; + struct utrace *utrace = task_utrace_struct(task); + INIT_REPORT(report); + + REPORT(task, utrace, &report, UTRACE_EVENT(EXEC), + report_exec, fmt, bprm, regs); +} + +static u32 do_report_syscall_entry(struct pt_regs *regs, + struct task_struct *task, + struct utrace *utrace, + struct utrace_report *report, + u32 resume_report) +{ + start_report(utrace); + REPORT_CALLBACKS(_reverse, task, utrace, report, + UTRACE_EVENT(SYSCALL_ENTRY), report_syscall_entry, + resume_report | report->result | report->action, + engine, regs); + finish_report(task, utrace, report, false); + + if (report->action != UTRACE_STOP) + return 0; + + utrace_stop(task, utrace, report->resume_action); + + if (fatal_signal_pending(task)) { + /* + * We are continuing despite UTRACE_STOP because of a + * SIGKILL. Don't let the system call actually proceed. + */ + report->result = UTRACE_SYSCALL_ABORT; + } else if (utrace->resume <= UTRACE_REPORT) { + /* + * If we've been asked for another report after our stop, + * go back to report (and maybe stop) again before we run + * the system call. The second (and later) reports are + * marked with the UTRACE_SYSCALL_RESUMED flag so that + * engines know this is a second report at the same + * entry. This gives them the chance to examine the + * registers anew after they might have been changed + * while we were stopped. + */ + report->detaches = false; + report->spurious = true; + report->action = report->resume_action = UTRACE_RESUME; + return UTRACE_SYSCALL_RESUMED; + } + + return 0; +} + +/* + * Called iff UTRACE_EVENT(SYSCALL_ENTRY) flag is set. + * Return true to prevent the system call. + */ +bool utrace_report_syscall_entry(struct pt_regs *regs) +{ + struct task_struct *task = current; + struct utrace *utrace = task_utrace_struct(task); + INIT_REPORT(report); + u32 resume_report = 0; + + do { + resume_report = do_report_syscall_entry(regs, task, utrace, + &report, resume_report); + } while (resume_report); + + return utrace_syscall_action(report.result) == UTRACE_SYSCALL_ABORT; +} + +/* + * Called iff UTRACE_EVENT(SYSCALL_EXIT) flag is set. + */ +void utrace_report_syscall_exit(struct pt_regs *regs) +{ + struct task_struct *task = current; + struct utrace *utrace = task_utrace_struct(task); + INIT_REPORT(report); + + REPORT(task, utrace, &report, UTRACE_EVENT(SYSCALL_EXIT), + report_syscall_exit, regs); +} + +/* + * Called iff UTRACE_EVENT(CLONE) flag is set. + * This notification call blocks the wake_up_new_task call on the child. + * So we must not quiesce here. tracehook_report_clone_complete will do + * a quiescence check momentarily. + */ +void utrace_report_clone(unsigned long clone_flags, struct task_struct *child) +{ + struct task_struct *task = current; + struct utrace *utrace = task_utrace_struct(task); + INIT_REPORT(report); + + /* + * We don't use the REPORT() macro here, because we need + * to clear utrace->cloning before finish_report(). + * After finish_report(), utrace can be a stale pointer + * in cases when report.action is still UTRACE_RESUME. + */ + start_report(utrace); + utrace->cloning = child; + + REPORT_CALLBACKS(, task, utrace, &report, + UTRACE_EVENT(CLONE), report_clone, + report.action, engine, clone_flags, child); + + utrace->cloning = NULL; + finish_report(task, utrace, &report, !(clone_flags & CLONE_VFORK)); + + /* + * For a vfork, we will go into an uninterruptible block waiting + * for the child. We need UTRACE_STOP to happen before this, not + * after. For CLONE_VFORK, utrace_finish_vfork() will be called. + */ + if (report.action == UTRACE_STOP && (clone_flags & CLONE_VFORK)) { + spin_lock(&utrace->lock); + utrace->vfork_stop = 1; + spin_unlock(&utrace->lock); + } +} + +/* + * We're called after utrace_report_clone() for a CLONE_VFORK. + * If UTRACE_STOP was left from the clone report, we stop here. + * After this, we'll enter the uninterruptible wait_for_completion() + * waiting for the child. + */ +void utrace_finish_vfork(struct task_struct *task) +{ + struct utrace *utrace = task_utrace_struct(task); + + if (utrace->vfork_stop) { + spin_lock(&utrace->lock); + utrace->vfork_stop = 0; + spin_unlock(&utrace->lock); + utrace_stop(task, utrace, UTRACE_RESUME); /* XXX */ + } +} + +/* + * Called iff UTRACE_EVENT(JCTL) flag is set. + * + * Called with siglock held. + */ +void utrace_report_jctl(int notify, int what) +{ + struct task_struct *task = current; + struct utrace *utrace = task_utrace_struct(task); + INIT_REPORT(report); + + spin_unlock_irq(&task->sighand->siglock); + + REPORT(task, utrace, &report, UTRACE_EVENT(JCTL), + report_jctl, what, notify); + + spin_lock_irq(&task->sighand->siglock); +} + +/* + * Called iff UTRACE_EVENT(EXIT) flag is set. + */ +void utrace_report_exit(long *exit_code) +{ + struct task_struct *task = current; + struct utrace *utrace = task_utrace_struct(task); + INIT_REPORT(report); + long orig_code = *exit_code; + + REPORT(task, utrace, &report, UTRACE_EVENT(EXIT), + report_exit, orig_code, exit_code); + + if (report.action == UTRACE_STOP) + utrace_stop(task, utrace, report.resume_action); +} + +/* + * Called iff UTRACE_EVENT(DEATH) or UTRACE_EVENT(QUIESCE) flag is set. + * + * It is always possible that we are racing with utrace_release_task here. + * For this reason, utrace_release_task checks for the event bits that get + * us here, and delays its cleanup for us to do. + */ +void utrace_report_death(struct task_struct *task, struct utrace *utrace, + bool group_dead, int signal) +{ + INIT_REPORT(report); + + BUG_ON(!task->exit_state); + + /* + * We are presently considered "quiescent"--which is accurate + * inasmuch as we won't run any more user instructions ever again. + * But for utrace_control and utrace_set_events to be robust, they + * must be sure whether or not we will run any more callbacks. If + * a call comes in before we do, taking the lock here synchronizes + * us so we don't run any callbacks just disabled. Calls that come + * in while we're running the callbacks will see the exit.death + * flag and know that we are not yet fully quiescent for purposes + * of detach bookkeeping. + */ + spin_lock(&utrace->lock); + BUG_ON(utrace->death); + utrace->death = 1; + utrace->resume = UTRACE_RESUME; + splice_attaching(utrace); + spin_unlock(&utrace->lock); + + REPORT_CALLBACKS(, task, utrace, &report, UTRACE_EVENT(DEATH), + report_death, engine, group_dead, signal); + + utrace_maybe_reap(task, utrace, false); +} + +/* + * Finish the last reporting pass before returning to user mode. + */ +static void finish_resume_report(struct task_struct *task, + struct utrace *utrace, + struct utrace_report *report) +{ + finish_report_reset(task, utrace, report); + + switch (report->action) { + case UTRACE_STOP: + utrace_stop(task, utrace, report->resume_action); + break; + + case UTRACE_INTERRUPT: + if (!signal_pending(task)) + set_tsk_thread_flag(task, TIF_SIGPENDING); + break; + + case UTRACE_BLOCKSTEP: + if (likely(arch_has_block_step())) { + user_enable_block_step(task); + break; + } + + /* + * This means some callback is to blame for failing + * to check arch_has_block_step() itself. Warn and + * then fall through to treat it as SINGLESTEP. + */ + WARN(1, "UTRACE_BLOCKSTEP when !arch_has_block_step()"); + + case UTRACE_SINGLESTEP: + if (likely(arch_has_single_step())) { + user_enable_single_step(task); + } else { + /* + * This means some callback is to blame for failing + * to check arch_has_single_step() itself. Spew + * about it so the loser will fix his module. + */ + WARN(1, + "UTRACE_SINGLESTEP when !arch_has_single_step()"); + } + break; + + case UTRACE_REPORT: + case UTRACE_RESUME: + default: + user_disable_single_step(task); + break; + } +} + +/* + * This is called when TIF_NOTIFY_RESUME had been set (and is now clear). + * We are close to user mode, and this is the place to report or stop. + * When we return, we're going to user mode or into the signals code. + */ +void utrace_resume(struct task_struct *task, struct pt_regs *regs) +{ + struct utrace *utrace = task_utrace_struct(task); + INIT_REPORT(report); + struct utrace_engine *engine; + + /* + * Some machines get here with interrupts disabled. The same arch + * code path leads to calling into get_signal_to_deliver(), which + * implicitly reenables them by virtue of spin_unlock_irq. + */ + local_irq_enable(); + + /* + * If this flag is still set it's because there was a signal + * handler setup done but no report_signal following it. Clear + * the flag before we get to user so it doesn't confuse us later. + */ + if (unlikely(utrace->signal_handler)) { + spin_lock(&utrace->lock); + utrace->signal_handler = 0; + spin_unlock(&utrace->lock); + } + + /* + * Update our bookkeeping even if there are no callbacks made here. + */ + report.action = start_report(utrace); + + switch (report.action) { + case UTRACE_RESUME: + /* + * Anything we might have done was already handled by + * utrace_get_signal(), or this is an entirely spurious + * call. (The arch might use TIF_NOTIFY_RESUME for other + * purposes as well as calling us.) + */ + return; + case UTRACE_REPORT: + if (unlikely(!(task->utrace_flags & UTRACE_EVENT(QUIESCE)))) + break; + /* + * Do a simple reporting pass, with no specific + * callback after report_quiesce. + */ + report.action = UTRACE_RESUME; + list_for_each_entry(engine, &utrace->attached, entry) + start_callback(utrace, &report, engine, task, 0); + break; + default: + /* + * Even if this report was truly spurious, there is no need + * for utrace_reset() now. TIF_NOTIFY_RESUME was already + * cleared--it doesn't stay spuriously set. + */ + report.spurious = false; + break; + } + + /* + * Finish the report and either stop or get ready to resume. + * If utrace->resume was not UTRACE_REPORT, this applies its + * effect now (i.e. step or interrupt). + */ + finish_resume_report(task, utrace, &report); +} + +/* + * Return true if current has forced signal_pending(). + * + * This is called only when current->utrace_flags is nonzero, so we know + * that current->utrace must be set. It's not inlined in tracehook.h + * just so that struct utrace can stay opaque outside this file. + */ +bool utrace_interrupt_pending(void) +{ + return task_utrace_struct(current)->resume == UTRACE_INTERRUPT; +} + +/* + * Take the siglock and push @info back on our queue. + * Returns with @task->sighand->siglock held. + */ +static void push_back_signal(struct task_struct *task, siginfo_t *info) + __acquires(task->sighand->siglock) +{ + struct sigqueue *q; + + if (unlikely(!info->si_signo)) { /* Oh, a wise guy! */ + spin_lock_irq(&task->sighand->siglock); + return; + } + + q = sigqueue_alloc(); + if (likely(q)) { + q->flags = 0; + copy_siginfo(&q->info, info); + } + + spin_lock_irq(&task->sighand->siglock); + + sigaddset(&task->pending.signal, info->si_signo); + if (likely(q)) + list_add(&q->list, &task->pending.list); + + set_tsk_thread_flag(task, TIF_SIGPENDING); +} + +/* + * This is the hook from the signals code, called with the siglock held. + * Here is the ideal place to stop. We also dequeue and intercept signals. + */ +int utrace_get_signal(struct task_struct *task, struct pt_regs *regs, + siginfo_t *info, struct k_sigaction *return_ka) + __releases(task->sighand->siglock) + __acquires(task->sighand->siglock) +{ + struct utrace *utrace; + struct k_sigaction *ka; + INIT_REPORT(report); + struct utrace_engine *engine; + const struct utrace_engine_ops *ops; + unsigned long event, want; + u32 ret; + int signr; + + utrace = task_utrace_struct(task); + if (utrace->resume < UTRACE_RESUME || + utrace->pending_attach || utrace->signal_handler) { + enum utrace_resume_action resume; + + /* + * We've been asked for an explicit report before we + * even check for pending signals. + */ + + spin_unlock_irq(&task->sighand->siglock); + + spin_lock(&utrace->lock); + + splice_attaching(utrace); + + report.result = utrace->signal_handler ? + UTRACE_SIGNAL_HANDLER : UTRACE_SIGNAL_REPORT; + utrace->signal_handler = 0; + + resume = utrace->resume; + utrace->resume = UTRACE_RESUME; + + spin_unlock(&utrace->lock); + + /* + * Make sure signal_pending() only returns true + * if there are real signals pending. + */ + if (signal_pending(task)) { + spin_lock_irq(&task->sighand->siglock); + recalc_sigpending(); + spin_unlock_irq(&task->sighand->siglock); + } + + if (resume > UTRACE_REPORT) { + /* + * We only got here to process utrace->resume. + * Despite no callbacks, this report is not spurious. + */ + report.action = resume; + report.spurious = false; + finish_resume_report(task, utrace, &report); + return -1; + } else if (!(task->utrace_flags & UTRACE_EVENT(QUIESCE))) { + /* + * We only got here to clear utrace->signal_handler. + */ + return -1; + } + + /* + * Do a reporting pass for no signal, just for EVENT(QUIESCE). + * The engine callbacks can fill in *info and *return_ka. + * We'll pass NULL for the @orig_ka argument to indicate + * that there was no original signal. + */ + event = 0; + ka = NULL; + memset(return_ka, 0, sizeof *return_ka); + } else if (!(task->utrace_flags & UTRACE_EVENT_SIGNAL_ALL) || + unlikely(task->signal->group_stop_count)) { + /* + * If no engine is interested in intercepting signals or + * we must stop, let the caller just dequeue them normally + * or participate in group-stop. + */ + return 0; + } else { + /* + * Steal the next signal so we can let tracing engines + * examine it. From the signal number and sigaction, + * determine what normal delivery would do. If no + * engine perturbs it, we'll do that by returning the + * signal number after setting *return_ka. + */ + signr = dequeue_signal(task, &task->blocked, info); + if (signr == 0) + return signr; + BUG_ON(signr != info->si_signo); + + ka = &task->sighand->action[signr - 1]; + *return_ka = *ka; + + /* + * We are never allowed to interfere with SIGKILL. + * Just punt after filling in *return_ka for our caller. + */ + if (signr == SIGKILL) + return signr; + + if (ka->sa.sa_handler == SIG_IGN) { + event = UTRACE_EVENT(SIGNAL_IGN); + report.result = UTRACE_SIGNAL_IGN; + } else if (ka->sa.sa_handler != SIG_DFL) { + event = UTRACE_EVENT(SIGNAL); + report.result = UTRACE_SIGNAL_DELIVER; + } else if (sig_kernel_coredump(signr)) { + event = UTRACE_EVENT(SIGNAL_CORE); + report.result = UTRACE_SIGNAL_CORE; + } else if (sig_kernel_ignore(signr)) { + event = UTRACE_EVENT(SIGNAL_IGN); + report.result = UTRACE_SIGNAL_IGN; + } else if (signr == SIGSTOP) { + event = UTRACE_EVENT(SIGNAL_STOP); + report.result = UTRACE_SIGNAL_STOP; + } else if (sig_kernel_stop(signr)) { + event = UTRACE_EVENT(SIGNAL_STOP); + report.result = UTRACE_SIGNAL_TSTP; + } else { + event = UTRACE_EVENT(SIGNAL_TERM); + report.result = UTRACE_SIGNAL_TERM; + } + + /* + * Now that we know what event type this signal is, we + * can short-circuit if no engines care about those. + */ + if ((task->utrace_flags & (event | UTRACE_EVENT(QUIESCE))) == 0) + return signr; + + /* + * We have some interested engines, so tell them about + * the signal and let them change its disposition. + */ + spin_unlock_irq(&task->sighand->siglock); + } + + /* + * This reporting pass chooses what signal disposition we'll act on. + */ + list_for_each_entry(engine, &utrace->attached, entry) { + /* + * See start_callback() comment about this barrier. + */ + utrace->reporting = engine; + smp_mb(); + + /* + * This pairs with the barrier in mark_engine_detached(), + * see start_callback() comments. + */ + want = engine->flags; + smp_rmb(); + ops = engine->ops; + + if ((want & (event | UTRACE_EVENT(QUIESCE))) == 0) { + utrace->reporting = NULL; + continue; + } + + if (ops->report_signal) + ret = (*ops->report_signal)( + report.result | report.action, engine, + regs, info, ka, return_ka); + else + ret = (report.result | (*ops->report_quiesce)( + report.action, engine, event)); + + /* + * Avoid a tight loop reporting again and again if some + * engine is too stupid. + */ + switch (utrace_resume_action(ret)) { + default: + break; + case UTRACE_INTERRUPT: + case UTRACE_REPORT: + ret = (ret & ~UTRACE_RESUME_MASK) | UTRACE_RESUME; + break; + } + + finish_callback(task, utrace, &report, engine, ret); + } + + /* + * We express the chosen action to the signals code in terms + * of a representative signal whose default action does it. + * Our caller uses our return value (signr) to decide what to + * do, but uses info->si_signo as the signal number to report. + */ + switch (utrace_signal_action(report.result)) { + case UTRACE_SIGNAL_TERM: + signr = SIGTERM; + break; + + case UTRACE_SIGNAL_CORE: + signr = SIGQUIT; + break; + + case UTRACE_SIGNAL_STOP: + signr = SIGSTOP; + break; + + case UTRACE_SIGNAL_TSTP: + signr = SIGTSTP; + break; + + case UTRACE_SIGNAL_DELIVER: + signr = info->si_signo; + + if (return_ka->sa.sa_handler == SIG_DFL) { + /* + * We'll do signr's normal default action. + * For ignore, we'll fall through below. + * For stop/death, break locks and returns it. + */ + if (likely(signr) && !sig_kernel_ignore(signr)) + break; + } else if (return_ka->sa.sa_handler != SIG_IGN && + likely(signr)) { + /* + * Complete the bookkeeping after the report. + * The handler will run. If an engine wanted to + * stop or step, then make sure we do another + * report after signal handler setup. + */ + if (report.action != UTRACE_RESUME) + report.action = UTRACE_INTERRUPT; + finish_report(task, utrace, &report, true); + + if (unlikely(report.result & UTRACE_SIGNAL_HOLD)) + push_back_signal(task, info); + else + spin_lock_irq(&task->sighand->siglock); + + /* + * We do the SA_ONESHOT work here since the + * normal path will only touch *return_ka now. + */ + if (unlikely(return_ka->sa.sa_flags & SA_ONESHOT)) { + return_ka->sa.sa_flags &= ~SA_ONESHOT; + if (likely(valid_signal(signr))) { + ka = &task->sighand->action[signr - 1]; + ka->sa.sa_handler = SIG_DFL; + } + } + + return signr; + } + + /* Fall through for an ignored signal. */ + + case UTRACE_SIGNAL_IGN: + case UTRACE_SIGNAL_REPORT: + default: + /* + * If the signal is being ignored, then we are on the way + * directly back to user mode. We can stop here, or step, + * as in utrace_resume(), above. After we've dealt with that, + * our caller will relock and come back through here. + */ + finish_resume_report(task, utrace, &report); + + if (unlikely(fatal_signal_pending(task))) { + /* + * The only reason we woke up now was because of a + * SIGKILL. Don't do normal dequeuing in case it + * might get a signal other than SIGKILL. That would + * perturb the death state so it might differ from + * what the debugger would have allowed to happen. + * Instead, pluck out just the SIGKILL to be sure + * we'll die immediately with nothing else different + * from the quiescent state the debugger wanted us in. + */ + sigset_t sigkill_only; + siginitsetinv(&sigkill_only, sigmask(SIGKILL)); + spin_lock_irq(&task->sighand->siglock); + signr = dequeue_signal(task, &sigkill_only, info); + BUG_ON(signr != SIGKILL); + *return_ka = task->sighand->action[SIGKILL - 1]; + return signr; + } + + if (unlikely(report.result & UTRACE_SIGNAL_HOLD)) { + push_back_signal(task, info); + spin_unlock_irq(&task->sighand->siglock); + } + + return -1; + } + + /* + * Complete the bookkeeping after the report. + * This sets utrace->resume if UTRACE_STOP was used. + */ + finish_report(task, utrace, &report, true); + + return_ka->sa.sa_handler = SIG_DFL; + + /* + * If this signal is fatal, si_signo gets through as exit_code. + * We can't allow a completely bogus value there or else core + * kernel code can freak out. (If an engine wants to control + * the exit_code value exactly, it can do so in report_exit.) + * We'll produce a big complaint in dmesg, but won't crash. + * That's nicer for debugging your utrace engine. + */ + if (unlikely(info->si_signo & 0x80)) { + WARN(1, "utrace engine left bogus si_signo value!"); + info->si_signo = SIGTRAP; + } + + if (unlikely(report.result & UTRACE_SIGNAL_HOLD)) + push_back_signal(task, info); + else + spin_lock_irq(&task->sighand->siglock); + + if (sig_kernel_stop(signr)) + task->signal->flags |= SIGNAL_STOP_DEQUEUED; + + return signr; +} + +/* + * This gets called after a signal handler has been set up. + * We set a flag so the next report knows it happened. + * If we're already stepping, make sure we do a report_signal. + * If not, make sure we get into utrace_resume() where we can + * clear the signal_handler flag before resuming. + */ +void utrace_signal_handler(struct task_struct *task, int stepping) +{ + struct utrace *utrace = task_utrace_struct(task); + + spin_lock(&utrace->lock); + + utrace->signal_handler = 1; + if (utrace->resume > UTRACE_INTERRUPT) { + if (stepping) { + utrace->resume = UTRACE_INTERRUPT; + set_tsk_thread_flag(task, TIF_SIGPENDING); + } else if (utrace->resume == UTRACE_RESUME) { + set_tsk_thread_flag(task, TIF_NOTIFY_RESUME); + } + } + + spin_unlock(&utrace->lock); +} + +/** + * utrace_prepare_examine - prepare to examine thread state + * @target: thread of interest, a &struct task_struct pointer + * @engine: engine pointer returned by utrace_attach_task() + * @exam: temporary state, a &struct utrace_examiner pointer + * + * This call prepares to safely examine the thread @target using + * &struct user_regset calls, or direct access to thread-synchronous fields. + * + * When @target is current, this call is superfluous. When @target is + * another thread, it must be held stopped via %UTRACE_STOP by @engine. + * + * This call may block the caller until @target stays stopped, so it must + * be called only after the caller is sure @target is about to unschedule. + * This means a zero return from a utrace_control() call on @engine giving + * %UTRACE_STOP, or a report_quiesce() or report_signal() callback to + * @engine that used %UTRACE_STOP in its return value. + * + * Returns -%ESRCH if @target is dead or -%EINVAL if %UTRACE_STOP was + * not used. If @target has started running again despite %UTRACE_STOP + * (for %SIGKILL or a spurious wakeup), this call returns -%EAGAIN. + * + * When this call returns zero, it's safe to use &struct user_regset + * calls and task_user_regset_view() on @target and to examine some of + * its fields directly. When the examination is complete, a + * utrace_finish_examine() call must follow to check whether it was + * completed safely. + */ +int utrace_prepare_examine(struct task_struct *target, + struct utrace_engine *engine, + struct utrace_examiner *exam) +{ + int ret = 0; + + if (unlikely(target == current)) + return 0; + + rcu_read_lock(); + if (unlikely(!engine_wants_stop(engine))) + ret = -EINVAL; + else if (unlikely(target->exit_state)) + ret = -ESRCH; + else { + exam->state = target->state; + if (unlikely(exam->state == TASK_RUNNING)) + ret = -EAGAIN; + else + get_task_struct(target); + } + rcu_read_unlock(); + + if (likely(!ret)) { + exam->ncsw = wait_task_inactive(target, exam->state); + put_task_struct(target); + if (unlikely(!exam->ncsw)) + ret = -EAGAIN; + } + + return ret; +} +EXPORT_SYMBOL_GPL(utrace_prepare_examine); + +/** + * utrace_finish_examine - complete an examination of thread state + * @target: thread of interest, a &struct task_struct pointer + * @engine: engine pointer returned by utrace_attach_task() + * @exam: pointer passed to utrace_prepare_examine() call + * + * This call completes an examination on the thread @target begun by a + * paired utrace_prepare_examine() call with the same arguments that + * returned success (zero). + * + * When @target is current, this call is superfluous. When @target is + * another thread, this returns zero if @target has remained unscheduled + * since the paired utrace_prepare_examine() call returned zero. + * + * When this returns an error, any examination done since the paired + * utrace_prepare_examine() call is unreliable and the data extracted + * should be discarded. The error is -%EINVAL if @engine is not + * keeping @target stopped, or -%EAGAIN if @target woke up unexpectedly. + */ +int utrace_finish_examine(struct task_struct *target, + struct utrace_engine *engine, + struct utrace_examiner *exam) +{ + int ret = 0; + + if (unlikely(target == current)) + return 0; + + rcu_read_lock(); + if (unlikely(!engine_wants_stop(engine))) + ret = -EINVAL; + else if (unlikely(target->state != exam->state)) + ret = -EAGAIN; + else + get_task_struct(target); + rcu_read_unlock(); + + if (likely(!ret)) { + unsigned long ncsw = wait_task_inactive(target, exam->state); + if (unlikely(ncsw != exam->ncsw)) + ret = -EAGAIN; + put_task_struct(target); + } + + return ret; +} +EXPORT_SYMBOL_GPL(utrace_finish_examine); + +/* + * This is declared in linux/regset.h and defined in machine-dependent + * code. We put the export here to ensure no machine forgets it. + */ +EXPORT_SYMBOL_GPL(task_user_regset_view); + +/* + * Called with rcu_read_lock() held. + */ +void task_utrace_proc_status(struct seq_file *m, struct task_struct *p) +{ + seq_printf(m, "Utrace:\t%lx\n", p->utrace_flags); +}