commit 97017da5ef946c6d38c252f56c8cb7c205b732fa Author: Florian Weimer Date: Fri Jul 4 21:46:16 2025 +0200 elf: Introduce _dl_debug_change_state It combines updating r_state with the debugger notification. The second change to _dl_open introduces an additional debugger notification for dlmopen, but debuggers are expected to ignore it. Reviewed-by: H.J. Lu (cherry picked from commit 8329939a37f483a16013dd8af8303cbcb86d92cb) diff --git a/elf/dl-close.c b/elf/dl-close.c index 4c963097f4dc8d79..fb27a1231c1c5b66 100644 --- a/elf/dl-close.c +++ b/elf/dl-close.c @@ -433,8 +433,7 @@ _dl_close_worker (struct link_map *map, bool force) /* Notify the debugger we are about to remove some loaded objects. LA_ACT_DELETE has already been signalled above for !unload_any. */ struct r_debug *r = _dl_debug_update (nsid); - r->r_state = RT_DELETE; - _dl_debug_state (); + _dl_debug_change_state (r, RT_DELETE); LIBC_PROBE (unmap_start, 2, nsid, r); if (unload_global) @@ -726,8 +725,7 @@ _dl_close_worker (struct link_map *map, bool force) __rtld_lock_unlock_recursive (GL(dl_load_tls_lock)); /* Notify the debugger those objects are finalized and gone. */ - r->r_state = RT_CONSISTENT; - _dl_debug_state (); + _dl_debug_change_state (r, RT_CONSISTENT); LIBC_PROBE (unmap_complete, 2, nsid, r); #ifdef SHARED diff --git a/elf/dl-debug.c b/elf/dl-debug.c index 5c49fa847e91bd81..b3777ffc136469cf 100644 --- a/elf/dl-debug.c +++ b/elf/dl-debug.c @@ -67,6 +67,13 @@ _dl_debug_update (Lmid_t ns) return &r->base; } +void +_dl_debug_change_state (struct r_debug *r, int state) +{ + atomic_store_release (&r->r_state, state); + _dl_debug_state (); +} + /* Initialize _r_debug_extended for the namespace NS. LDBASE is the run-time load address of the dynamic linker, to be put in _r_debug_extended.r_ldbase. Return the address of _r_debug. */ diff --git a/elf/dl-load.c b/elf/dl-load.c index 75a7187c649e0202..8b0890499d66f67a 100644 --- a/elf/dl-load.c +++ b/elf/dl-load.c @@ -947,8 +947,7 @@ _dl_notify_new_object (int mode, Lmid_t nsid, struct link_map *l) /* Notify the debugger we have added some objects. We need to call _dl_debug_initialize in a static program in case dynamic linking has not been used before. */ - r->r_state = RT_ADD; - _dl_debug_state (); + _dl_debug_change_state (r, RT_ADD); LIBC_PROBE (map_start, 2, nsid, r); } else diff --git a/elf/dl-open.c b/elf/dl-open.c index 80f084d5c838fc1c..6f6d3ddbf94c764c 100644 --- a/elf/dl-open.c +++ b/elf/dl-open.c @@ -792,8 +792,7 @@ dl_open_worker (void *a) #ifdef SHARED bool was_not_consistent = r->r_state != RT_CONSISTENT; #endif - r->r_state = RT_CONSISTENT; - _dl_debug_state (); + _dl_debug_change_state (r, RT_CONSISTENT); LIBC_PROBE (map_complete, 3, nsid, r, args->map); #ifdef SHARED @@ -871,7 +870,7 @@ no more namespaces available for dlmopen()")); } GL(dl_ns)[nsid].libc_map = NULL; - _dl_debug_update (nsid)->r_state = RT_CONSISTENT; + _dl_debug_change_state (_dl_debug_update (nsid), RT_CONSISTENT); } /* Never allow loading a DSO in a namespace which is empty. Such direct placements is only causing problems. Also don't allow diff --git a/elf/rtld.c b/elf/rtld.c index 809fc807989b285e..43bfc7378afc6cc7 100644 --- a/elf/rtld.c +++ b/elf/rtld.c @@ -1850,8 +1850,7 @@ dl_main (const ElfW(Phdr) *phdr, elf_setup_debug_entry (main_map, r); /* We start adding objects. */ - r->r_state = RT_ADD; - _dl_debug_state (); + _dl_debug_change_state (r, RT_ADD); LIBC_PROBE (init_start, 2, LM_ID_BASE, r); /* Auditing checkpoint: we are ready to signal that the initial map @@ -2402,8 +2401,7 @@ dl_main (const ElfW(Phdr) *phdr, /* Notify the debugger all new objects are now ready to go. We must re-get the address since by now the variable might be in another object. */ r = _dl_debug_update (LM_ID_BASE); - r->r_state = RT_CONSISTENT; - _dl_debug_state (); + _dl_debug_change_state (r, RT_CONSISTENT); LIBC_PROBE (init_complete, 2, LM_ID_BASE, r); /* Auditing checkpoint: we have added all objects. */ diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 8b9ae3783056a29f..017406e7fa93c941 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -1067,8 +1067,14 @@ extern void _dl_debug_state (void); rtld_hidden_proto (_dl_debug_state) /* Initialize `struct r_debug_extended' for the namespace NS. LDBASE - is the run-time load address of the dynamic linker, to be put in the - `r_ldbase' member. Return the address of the structure. */ + is the run-time load address of the dynamic linker, to be put in + the `r_ldbase' member. + + Return the address of the r_debug structure for the namespace. + This is not merely a convenience or optimization, but it is + necessary for the LIBC_PROBE Systemtap/debugger probes to work + reliably: direct variable access can create probes that tools + cannot consume. */ extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns) attribute_hidden; @@ -1076,6 +1082,10 @@ extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns) of the namespace NS. */ extern struct r_debug *_dl_debug_update (Lmid_t ns) attribute_hidden; +/* Update R->r_state to STATE and notify the debugger by calling + _dl_debug_state. */ +void _dl_debug_change_state (struct r_debug *r, int state) attribute_hidden; + /* Initialize the basic data structure for the search paths. SOURCE is either "LD_LIBRARY_PATH" or "--library-path". GLIBC_HWCAPS_PREPEND adds additional glibc-hwcaps subdirectories to