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packages/ocaml/ocaml-base-compiler.4.08.1/files/alt-signal-stack.patch
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From 17df117b4939486d3285031900587afce5262c8c Mon Sep 17 00:00:00 2001 | ||
From: Xavier Leroy <xavierleroy@users.noreply.github.com> | ||
Date: Fri, 5 Mar 2021 19:14:07 +0100 | ||
Subject: [PATCH] Dynamically allocate the alternate signal stack | ||
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||
In Glibc 2.34 and later, SIGSTKSZ may not be a compile-time constant. | ||
It is no longer possible to statically allocate the alternate signal | ||
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 | ||
even for the main thread. It reuses the code already in place to allocate | ||
the alternate signal stack for other threads. | ||
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||
The alternate signal stack is freed when the main OCaml code / an OCaml thread | ||
stops. | ||
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(partial back-port of PR#10266 and PR#10726) | ||
--- | ||
runtime/fail_nat.c | 7 ++++- | ||
runtime/signals_nat.c | 64 +++++++++++++++++++++++++++++++++++++------ | ||
runtime/startup_nat.c | 7 ++++- | ||
runtime/sys.c | 5 ++++ | ||
4 files changed, 72 insertions(+), 11 deletions(-) | ||
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diff --git a/runtime/fail_nat.c b/runtime/fail_nat.c | ||
index ec5bfebc961e..c372bc14f8ee 100644 | ||
--- a/runtime/fail_nat.c | ||
+++ b/runtime/fail_nat.c | ||
@@ -31,6 +31,8 @@ | ||
#include "caml/roots.h" | ||
#include "caml/callback.h" | ||
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+extern void caml_terminate_signals(void); | ||
+ | ||
/* The globals holding predefined exceptions */ | ||
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typedef value caml_generated_constant[1]; | ||
@@ -60,7 +62,10 @@ char * caml_exception_pointer = NULL; | ||
void caml_raise(value v) | ||
{ | ||
Unlock_exn(); | ||
- if (caml_exception_pointer == NULL) caml_fatal_uncaught_exception(v); | ||
+ if (caml_exception_pointer == NULL) { | ||
+ caml_terminate_signals(); | ||
+ caml_fatal_uncaught_exception(v); | ||
+ } | ||
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||
while (caml_local_roots != NULL && | ||
(char *) caml_local_roots < caml_exception_pointer) { | ||
diff --git a/runtime/signals_nat.c b/runtime/signals_nat.c | ||
index 29a5f49e6251..351b575a08e5 100644 | ||
--- a/runtime/signals_nat.c | ||
+++ b/runtime/signals_nat.c | ||
@@ -182,7 +182,6 @@ DECLARE_SIGNAL_HANDLER(trap_handler) | ||
#ifdef HAS_STACK_OVERFLOW_DETECTION | ||
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static char * system_stack_top; | ||
-static char sig_alt_stack[SIGSTKSZ]; | ||
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#if defined(SYS_linux) | ||
/* PR#4746: recent Linux kernels with support for stack randomization | ||
@@ -275,14 +274,61 @@ void caml_init_signals(void) | ||
{ | ||
stack_t stk; | ||
struct sigaction act; | ||
- stk.ss_sp = sig_alt_stack; | ||
- stk.ss_size = SIGSTKSZ; | ||
- stk.ss_flags = 0; | ||
- SET_SIGACT(act, segv_handler); | ||
- act.sa_flags |= SA_ONSTACK | SA_NODEFER; | ||
- sigemptyset(&act.sa_mask); | ||
- system_stack_top = (char *) &act; | ||
- if (sigaltstack(&stk, NULL) == 0) { sigaction(SIGSEGV, &act, NULL); } | ||
+ /* Allocate and select an alternate stack for handling signals, | ||
+ especially SIGSEGV signals. | ||
+ The alternate stack used to be statically-allocated for the main thread, | ||
+ but this is incompatible with Glibc 2.34 and newer, where SIGSTKSZ | ||
+ may not be a compile-time constant. */ | ||
+ stk.ss_sp = malloc(SIGSTKSZ); | ||
+ if (stk.ss_sp != NULL) { | ||
+ stk.ss_size = SIGSTKSZ; | ||
+ stk.ss_flags = 0; | ||
+ SET_SIGACT(act, segv_handler); | ||
+ act.sa_flags |= SA_ONSTACK | SA_NODEFER; | ||
+ sigemptyset(&act.sa_mask); | ||
+ system_stack_top = (char *) &act; | ||
+ if (sigaltstack(&stk, NULL) == 0) | ||
+ sigaction(SIGSEGV, &act, NULL); | ||
+ else | ||
+ free(stk.ss_sp); | ||
+ } | ||
+ } | ||
+#endif | ||
+} | ||
+ | ||
+/* Termination of signal stuff */ | ||
+ | ||
+#if defined(TARGET_power) || defined(TARGET_s390x) \ | ||
+ || defined(HAS_STACK_OVERFLOW_DETECTION) | ||
+static void set_signal_default(int signum) | ||
+{ | ||
+ struct sigaction act; | ||
+ sigemptyset(&act.sa_mask); | ||
+ act.sa_handler = SIG_DFL; | ||
+ act.sa_flags = 0; | ||
+ sigaction(signum, &act, NULL); | ||
+} | ||
+#endif | ||
+ | ||
+void caml_terminate_signals(void) | ||
+{ | ||
+#if defined(TARGET_power) | ||
+ set_signal_default(SIGTRAP); | ||
+#endif | ||
+ | ||
+#if defined(TARGET_s390x) | ||
+ set_signal_default(SIGFPE); | ||
+#endif | ||
+ | ||
+#ifdef HAS_STACK_OVERFLOW_DETECTION | ||
+ set_signal_default(SIGSEGV); | ||
+ stack_t oldstk, stk; | ||
+ stk.ss_flags = SS_DISABLE; | ||
+ if (sigaltstack(&stk, &oldstk) == 0) { | ||
+ /* If caml_init_signals failed, we are not using an alternate signal stack. | ||
+ SS_DISABLE will be set in oldstk, and there is nothing to free in this | ||
+ case. */ | ||
+ if (! (oldstk.ss_flags & SS_DISABLE)) free(oldstk.ss_sp); | ||
} | ||
#endif | ||
} | ||
diff --git a/runtime/startup_nat.c b/runtime/startup_nat.c | ||
index 5b200362f7e2..0cfa61dc4eca 100644 | ||
--- a/runtime/startup_nat.c | ||
+++ b/runtime/startup_nat.c | ||
@@ -92,6 +92,7 @@ void (*caml_termination_hook)(void *) = NULL; | ||
extern value caml_start_program (void); | ||
extern void caml_init_ieee_floats (void); | ||
extern void caml_init_signals (void); | ||
+extern void caml_terminate_signals(void); | ||
#ifdef _WIN32 | ||
extern void caml_win32_overflow_detection (void); | ||
#endif | ||
@@ -106,6 +107,7 @@ extern void caml_install_invalid_parameter_handler(); | ||
value caml_startup_common(char_os **argv, int pooling) | ||
{ | ||
char_os * exe_name, * proc_self_exe; | ||
+ value res; | ||
char tos; | ||
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/* Determine options */ | ||
@@ -153,10 +155,13 @@ value caml_startup_common(char_os **argv, int pooling) | ||
exe_name = caml_search_exe_in_path(exe_name); | ||
caml_sys_init(exe_name, argv); | ||
if (sigsetjmp(caml_termination_jmpbuf.buf, 0)) { | ||
+ caml_terminate_signals(); | ||
if (caml_termination_hook != NULL) caml_termination_hook(NULL); | ||
return Val_unit; | ||
} | ||
- return caml_start_program(); | ||
+ res = caml_start_program(); | ||
+ caml_terminate_signals(); | ||
+ return res; | ||
} | ||
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value caml_startup_exn(char_os **argv) | ||
diff --git a/runtime/sys.c b/runtime/sys.c | ||
index c019ee9f7e73..e951c636eb68 100644 | ||
--- a/runtime/sys.c | ||
+++ b/runtime/sys.c | ||
@@ -112,6 +112,8 @@ static void caml_sys_check_path(value name) | ||
} | ||
} | ||
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+extern void caml_terminate_signals(void); | ||
+ | ||
CAMLprim value caml_sys_exit(value retcode_v) | ||
{ | ||
int retcode = Int_val(retcode_v); | ||
@@ -155,6 +157,9 @@ CAMLprim value caml_sys_exit(value retcode_v) | ||
caml_shutdown(); | ||
#ifdef _WIN32 | ||
caml_restore_win32_terminal(); | ||
+#endif | ||
+#ifdef NATIVE_CODE | ||
+ caml_terminate_signals(); | ||
#endif | ||
exit(retcode); | ||
} |
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