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erts: Fix alternate signal stack sizing on musl (AT_MINSIGSTKSZ) #11249

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erts: Fix alternate signal stack sizing on musl (AT_MINSIGSTKSZ) #11249

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25 changes: 12 additions & 13 deletions erts/emulator/sys/unix/sys_signal_stack.c
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Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,9 @@
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#if defined(__linux__)
# include <sys/auxv.h>
#endif

#include "sys.h"
#include "erl_alloc.h"
Expand All @@ -88,29 +91,25 @@
#endif

/*
* Set alternate signal stack for the invoking thread.
* Set up alternate signal stack for an Erlang process scheduler thread.
*/
static void sys_sigaltstack(void *ss_sp) {
void sys_thread_init_signal_stack(void) {
stack_t ss;

ss.ss_sp = ss_sp;
ss.ss_flags = 0;
#if defined(__linux__) && defined(AT_MINSIGSTKSZ)
ss.ss_size = (size_t) getauxval(AT_MINSIGSTKSZ);
ss.ss_size = MAX(ss.ss_size, SIGSTKSZ);
#else
ss.ss_size = SIGSTKSZ;
#endif
ss.ss_sp = malloc(ss.ss_size); // Never freed
ss.ss_flags = 0;

if (sigaltstack(&ss, NULL) < 0) {
ERTS_INTERNAL_ERROR("Failed to set alternate signal stack");
}
}

/*
* Set up alternate signal stack for an Erlang process scheduler thread.
*/
void sys_thread_init_signal_stack(void) {
/* This will never be freed. */
char *stack = malloc(SIGSTKSZ);
sys_sigaltstack(stack);
}

/*
* 1. Set up alternate signal stack for the main thread.
* 2. Add SA_ONSTACK to existing user-defined signal handlers.
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