#include <fcntl.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/ucontext.h>
#include <unistd.h>

static int dnprintf(int fd, const char *fmt, ...)
{
	va_list ap;
#define BUFSIZE 1024
	static char buf[BUFSIZE];
	va_start(ap, fmt);
	vsnprintf(buf, BUFSIZE, fmt, ap);
	va_end(ap);
	return write(fd, buf, strnlen(buf, BUFSIZE));
}

static void write_hex(int fd, void *p, unsigned int n)
{
	while (n--) {
		unsigned int i = *(unsigned char *)p++;
		dnprintf(fd, "%02x", i & 0xff);
	}
}

static volatile sig_atomic_t done;

static void handler(int sig, siginfo_t *info, void *ucontext)
{
	ucontext_t *uc = ucontext;

	dnprintf(2, "%s: si_signo %2d, si_code %3d, si_addr 0x%08x, ",
	       __func__, info->si_signo, info->si_code, info->si_addr);
	dnprintf(2, "uc_mcontext ");
	write_hex(2, &uc->uc_mcontext, sizeof(uc->uc_mcontext));
	dnprintf(2, ", __glibc_reserved1 ");
	write_hex(2, &uc->__glibc_reserved1, sizeof(uc->__glibc_reserved1));
	dnprintf(2, "\n");

	switch (sig) {
	case SIGALRM:
		// Arrange for signal delivery on return from handler
		dnprintf(2, "%s: raise(SIGUSR1), raise(SIGUSR2)\n", __func__);
		raise(SIGUSR1);
		raise(SIGUSR2);
		break;
	case SIGUSR1:
	case SIGUSR2:
		// Nothing to do
		break;
	case SIGFPE:
		// Fix up divisor
		uc->uc_mcontext.gregs[2] = 1; // REG_D2
		break;
	case SIGBUS:
		// Give up
		raise(SIGABRT);
	}
	done = 1;
}

int main(void)
{
	sigset_t mask;
	sigfillset(&mask);

	struct sigaction sa = {
		.sa_sigaction = handler,
		.sa_mask = mask,
		.sa_flags = SA_SIGINFO,
	};
	sigaction(SIGALRM, &sa, NULL);
	sigaction(SIGUSR1, &sa, NULL);
	sigaction(SIGUSR2, &sa, NULL);
	sigaction(SIGFPE, &sa, NULL);
	sigaction(SIGBUS, &sa, NULL);

	// Arrange for signal delivery on return from trap
	dnprintf(2, "%s: raise(SIGALRM)\n", __func__);
	raise(SIGALRM);

	// Signal delivery on return from interrupt
	dnprintf(2, "%s: alarm(2)\n", __func__);
	alarm(2);
	done = 0;
	while (!done)
		continue;

	// Signal delivery on return from exception
	dnprintf(2, "%s: divide by zero\n", __func__);
	asm("clrl  %%d2       \n\
	     divsl %%d2,%%d1  \n\
	     " : : : "d1", "d2");

	// Signal delivery on return from fault
	char pattern[] = "/tmp/sigXXXXXX";
	int fd = mkstemp(pattern);
	if (fd == -1)
		return 1;
	unlink(pattern);
	volatile char *addr = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE,
	                           MAP_PRIVATE, fd, 0);
	if (addr == (char *)-1)
		return 2;
	dnprintf(2, "%s: read pointer %p\n", __func__, addr);
	*addr;
}