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/*
* sigaction.c
*/
#include <signal.h>
#include <sys/syscall.h>
/* We use -mno-pic so our function pointers are straight to the function entry
point, but the kernel always expects a descriptor. Thus we create a fake
descriptor for each possible signal, update it, and pass that to the kernel
instead (the descriptor must remain valid after returning from sigaction
until it is replaced). */
static struct {
uintptr_t entry;
uintptr_t gp;
} signal_descriptors[_NSIG];
__extern int ____rt_sigaction(int, const struct sigaction *, struct sigaction *,
size_t);
int __rt_sigaction(int sig, struct sigaction *act,
struct sigaction *oact, size_t size)
{
sigset_t signal_mask, old_signal_mask;
uintptr_t old_entry;
int rv;
if (sig < 0 || sig >= _NSIG) {
errno = EINVAL;
return -1;
}
/* Mask the signal to avoid races on access to its descriptor */
sigemptyset(&signal_mask);
sigaddset(&signal_mask, sig);
rv = sigprocmask(SIG_BLOCK, &signal_mask, &old_signal_mask);
if (rv)
return -1;
if (oact) {
old_entry = signal_descriptors[sig].entry;
}
if (act && act->sa_handler != SIG_IGN && act->sa_handler != SIG_DFL) {
signal_descriptors[sig].entry = (uintptr_t)act->sa_handler;
act->sa_handler =
(__sighandler_t)(uintptr_t)&signal_descriptors[sig];
}
rv = ____rt_sigaction(sig, act, oact, size);
if (rv)
signal_descriptors[sig].entry = old_entry;
/* Restore signal mask */
(void)sigprocmask(SIG_SETMASK, &old_signal_mask, NULL);
if (oact && oact->sa_handler != SIG_IGN &&
oact->sa_handler != SIG_DFL) {
oact->sa_handler = (__sighandler_t)old_entry;
}
return rv;
}
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