104 lines
3.5 KiB
Diff
104 lines
3.5 KiB
Diff
From 24a9db7784ddfcf0af2d2be2f51616ed960ae7e8 Mon Sep 17 00:00:00 2001
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From: Xavier Leroy <xavierleroy@users.noreply.github.com>
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Date: Fri, 5 Mar 2021 19:14:07 +0100
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Subject: [PATCH 6/6] Dynamically allocate the alternate signal stack (#10266)
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In Glibc 2.34 and later, SIGSTKSZ may not be a compile-time constant.
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It is no longer possible to statically allocate the alternate signal
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stack for the main thread, as we've been doing for the last 25 years.
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This commit implements dynamic allocation of the alternate signal stack
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even for the main thread. It reuses the code already in place to allocate
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the alternate signal stack for other threads.
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Fixes: #10250.
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(cherry picked from commit fc9534746bf5d08a4c109f22e344cf49d5d46d54)
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---
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runtime/caml/signals.h | 2 +-
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runtime/signals_byt.c | 2 +-
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runtime/signals_nat.c | 25 ++++++++++++++-----------
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3 files changed, 16 insertions(+), 13 deletions(-)
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diff --git a/runtime/caml/signals.h b/runtime/caml/signals.h
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index 7ec1ad3ba..98b75107b 100644
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--- a/runtime/caml/signals.h
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+++ b/runtime/caml/signals.h
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@@ -82,7 +82,7 @@ void caml_set_action_pending (void);
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value caml_do_pending_actions_exn (void);
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value caml_process_pending_actions_with_root (value extra_root); // raises
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int caml_set_signal_action(int signo, int action);
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-void caml_setup_stack_overflow_detection(void);
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+CAMLextern int caml_setup_stack_overflow_detection(void);
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CAMLextern void (*caml_enter_blocking_section_hook)(void);
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CAMLextern void (*caml_leave_blocking_section_hook)(void);
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diff --git a/runtime/signals_byt.c b/runtime/signals_byt.c
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index 040de03c5..9bd2b20c6 100644
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--- a/runtime/signals_byt.c
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+++ b/runtime/signals_byt.c
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@@ -86,4 +86,4 @@ int caml_set_signal_action(int signo, int action)
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return 0;
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}
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-void caml_setup_stack_overflow_detection(void) {}
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+CAMLexport int caml_setup_stack_overflow_detection(void) { return 0; }
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diff --git a/runtime/signals_nat.c b/runtime/signals_nat.c
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index fc5a77f84..f56fce6b7 100644
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--- a/runtime/signals_nat.c
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+++ b/runtime/signals_nat.c
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@@ -195,8 +195,6 @@ DECLARE_SIGNAL_HANDLER(trap_handler)
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#error "CONTEXT_SP is required if HAS_STACK_OVERFLOW_DETECTION is defined"
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#endif
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-static char sig_alt_stack[SIGSTKSZ];
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-
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/* Code compiled with ocamlopt never accesses more than
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EXTRA_STACK bytes below the stack pointer. */
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#define EXTRA_STACK 256
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@@ -282,28 +280,33 @@ void caml_init_signals(void)
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#endif
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#ifdef HAS_STACK_OVERFLOW_DETECTION
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- {
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- stack_t stk;
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+ if (caml_setup_stack_overflow_detection() != -1) {
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struct sigaction act;
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- stk.ss_sp = sig_alt_stack;
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- stk.ss_size = SIGSTKSZ;
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- stk.ss_flags = 0;
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SET_SIGACT(act, segv_handler);
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act.sa_flags |= SA_ONSTACK | SA_NODEFER;
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sigemptyset(&act.sa_mask);
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- if (sigaltstack(&stk, NULL) == 0) { sigaction(SIGSEGV, &act, NULL); }
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+ sigaction(SIGSEGV, &act, NULL);
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}
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#endif
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}
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-void caml_setup_stack_overflow_detection(void)
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+/* Allocate and select an alternate stack for handling signals,
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+ especially SIGSEGV signals.
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+ Each thread needs its own alternate stack.
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+ The alternate stack used to be statically-allocated for the main thread,
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+ but this is incompatible with Glibc 2.34 and newer, where SIGSTKSZ
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+ may not be a compile-time constant (issue #10250). */
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+
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+CAMLexport int caml_setup_stack_overflow_detection(void)
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{
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#ifdef HAS_STACK_OVERFLOW_DETECTION
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stack_t stk;
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stk.ss_sp = malloc(SIGSTKSZ);
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+ if (stk.ss_sp == NULL) return -1;
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stk.ss_size = SIGSTKSZ;
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stk.ss_flags = 0;
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- if (stk.ss_sp)
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- sigaltstack(&stk, NULL);
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+ return sigaltstack(&stk, NULL);
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+#else
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+ return 0;
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#endif
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}
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--
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2.32.0
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