musl/src/signal/sigaction.c

#include <signal.h>
#include <errno.h>
#include <string.h>
#include "syscall.h"
#include "pthread_impl.h"
#include "libc.h"
#include "ksigaction.h"

volatile int dummy_lock[1] = { 0 };

__attribute__((__visibility__("hidden")))
weak_alias(dummy_lock, __abort_lock);

static int unmask_done;
static unsigned long handler_set[_NSIG/(8*sizeof(long))];

void __get_handler_set(sigset_t *set)
{
	memcpy(set, handler_set, sizeof handler_set);
}

int __libc_sigaction(int sig, const struct sigaction *restrict sa, struct sigaction *restrict old)
{
	struct k_sigaction ksa, ksa_old;
	unsigned long set[_NSIG/(8*sizeof(long))];
	if (sa) {
		if ((uintptr_t)sa->sa_handler > 1UL) {
			a_or_l(handler_set+(sig-1)/(8*sizeof(long)),
				1UL<<(sig-1)%(8*sizeof(long)));

			/* If pthread_create has not yet been called,
			 * implementation-internal signals might not
			 * yet have been unblocked. They must be
			 * unblocked before any signal handler is
			 * installed, so that an application cannot
			 * receive an illegal sigset_t (with them
			 * blocked) as part of the ucontext_t passed
			 * to the signal handler. */
			if (!libc.threaded && !unmask_done) {
				__syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
					SIGPT_SET, 0, _NSIG/8);
				unmask_done = 1;
			}
		}
		/* Changing the disposition of SIGABRT to anything but
		 * SIG_DFL requires a lock, so that it cannot be changed
		 * while abort is terminating the process after simply
		 * calling raise(SIGABRT) failed to do so. */
		if (sa->sa_handler != SIG_DFL && sig == SIGABRT) {
			__block_all_sigs(&set);
			LOCK(__abort_lock);
		}
		ksa.handler = sa->sa_handler;
		ksa.flags = sa->sa_flags | SA_RESTORER;
		ksa.restorer = (sa->sa_flags & SA_SIGINFO) ? __restore_rt : __restore;
		memcpy(&ksa.mask, &sa->sa_mask, _NSIG/8);
	}
	int r = __syscall(SYS_rt_sigaction, sig, sa?&ksa:0, old?&ksa_old:0, _NSIG/8);
	if (sig == SIGABRT && sa && sa->sa_handler != SIG_DFL) {
		UNLOCK(__abort_lock);
		__restore_sigs(&set);
	}
	if (old && !r) {
		old->sa_handler = ksa_old.handler;
		old->sa_flags = ksa_old.flags;
		memcpy(&old->sa_mask, &ksa_old.mask, _NSIG/8);
	}
	return __syscall_ret(r);
}

int __sigaction(int sig, const struct sigaction *restrict sa, struct sigaction *restrict old)
{
	if (sig-32U < 3 || sig-1U >= _NSIG-1) {
		errno = EINVAL;
		return -1;
	}
	return __libc_sigaction(sig, sa, old);
}

weak_alias(__sigaction, sigaction);