rt_sigaction.c

#include <asm/signal.h>

static volatile int stop = 0;

static void handle_sig(int sig)
{
	printf("sig = %d\n", sig);
	stop = 1;
}

static void __restore_rt(void)
{
	__asm__ volatile (
		"syscall"
		:
		: "a"(15)
		: "memory", "rcx", "r11"
	);
	__builtin_unreachable();
}

static int __rt_sigaction(int sig, const struct sigaction *act,
			  struct sigaction *oact, size_t sigsetsize)
{
	int ret = 13;
	register size_t size __asm__("r10") = sigsetsize;

	__asm__ volatile (
		"syscall"
		: "+d"(oact), /* %rdx */
		  "+a"(ret)   /* %rax */
		: "D"(sig),   /* %rdi */
		  "S"(act),   /* %rsi */
		  "r"(size)   /* %r10 */
		: "memory", "rcx", "r11"
	);

	return ret;
}

static int rt_sigaction(int sig, struct sigaction *act, struct sigaction *oact,
			size_t size)
{
	int ret;
	act->sa_flags |= SA_RESTORER;
	act->sa_restorer = __restore_rt;
	ret = __rt_sigaction(sig, act, oact, sizeof(sigset_t));
	return ret;
}

static inline void cpu_relax(void)
{
	__asm__ volatile ("rep; nop;" ::: "memory");
}

int main(void)
{
	struct sigaction act;

	memset(&act, 0, sizeof(act));
	act.sa_handler = handle_sig;
	rt_sigaction(SIGINT, &act, NULL, 0);

	while (!stop)
		cpu_relax();

	return 0;
}