gistfile1.txt

/* See LICENSE file for copyright and license details. */

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include "util.h"

#define ERR ((void*) -1)

static void sigpoweroff(void);
static void sigreap(void);
static void sigreboot(void);
static void spawn(char *const []);

char* strerror(int err);
static void diee(const char* msg, const char* arg);

static struct {
	int sig;
	void (*handler)(void);
} sigmap[] = {
	{ SIGUSR1, sigpoweroff },
	{ SIGCHLD, sigreap     },
	{ SIGINT,  sigreboot   },
};

#include "config.h"

static sigset_t set;

int
main(void)
{
	int sig;
	size_t i;

	//if (getpid() != 1)
	//	return EXIT_FAILURE;

	//chdir("/");

	sigemptyset(&set);
	for (i = 0; i < LEN(sigmap); i++)
		sigaddset(&set, sigmap[i].sig);
	sigprocmask(SIG_BLOCK, &set, NULL);

	spawn(rcinitcmd);

	while (1) {
		sigwait(&set, &sig);
		for (i = 0; i < LEN(sigmap); i++)
			if (sigmap[i].sig == sig)
				sigmap[i].handler();
	}

	/* not reachable */
	return EXIT_SUCCESS;
}

static void
sigpoweroff(void)
{
	spawn(rcpoweroffcmd);
}

static void
sigreap(void)
{
	while (waitpid(-1, NULL, WNOHANG) > 0)
		;
}

static void
sigreboot(void)
{
	spawn(rcrebootcmd);
}

static void
spawn(char *const argv[])
{
	pid_t pid;

	pid = fork();
	if (pid < 0) {
		diee("fork failed", ERR);
	} else if (pid == 0) {
		sigprocmask(SIG_UNBLOCK, &set, NULL);
		setsid();
		setpgid(0, 0);
		execve(argv[0], argv, NULL);
		diee("fork failed", ERR);
		_exit(EXIT_FAILURE);
	}
}

static void diee(const char* msg, const char* arg)
{
	char buf[256];
	int len = strlen(msg);
	int max = sizeof(buf) - 2;

	strncpy(buf, msg, max);

	if(arg == ERR)
		arg = strerror(errno);
	if(arg)
		strncpy(buf + len, arg, max - len);

	len = strlen(buf);
	buf[len++] = '\n';

	write(2, buf, len);
	_exit(-1);
}

#define r(sym) case sym: return #sym

char* strerror(int err)
{
	static char buf[10];

	switch(err) {
		r(ENOENT);	/* open */
		r(ELOOP);	/* open, unlikely */
		r(ENFILE);	/* open, socket, accept */
		r(EPIPE);	/* sendmsg */
		r(ENOMEM);	/* mmap and a buch of other calls */
		r(ECONNREFUSED);/* connect in telinit */
		r(EINTR);	/* poll; unlikely for other syscalls */
		r(EINVAL);	/* generic, unlikely */
		r(EACCES);	/* execve */
		r(EIO);		/* unlikely, bad news */
	}

	int i = sizeof(buf)-1;
	buf[i--] = '\0';
	while(err && i >= 0) {
		buf[i--] = err % 10;
		err /= 10;
	};

	return buf + i + 1;
}