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/*
* Oracle Linux DTrace; become a daemon.
* Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
* Licensed under the Universal Permissive License v 1.0 as shown at
* http://oss.oracle.com/licenses/upl.
*/
#include <sys/compiler.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdlib.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <port.h>
/*
* Write an error return featuring errno down the synchronization pipe, and
* terminate.
*
* If fd is < 0, write to stderr instead.
*/
_dt_noreturn_
void
daemon_perr(int fd, const char *err, int err_no)
{
char sep[] = ": ";
char *errstr;
/*
* Not a paranoid write: see above.
*/
if (fd >= 0) {
write(fd, err, strlen(err));
if ((errstr = strerror(err_no)) != NULL) {
write(fd, sep, strlen(sep));
write(fd, errstr, strlen(errstr));
}
} else
fprintf(stderr, "%s: %s\n", err, strerror(err_no));
_exit(1);
}
/*
* Log a message down the synchronization pipe, using a va_list.
*
* If fd is < 0, write to stderr instead.
*/
void
daemon_vlog(int fd, const char *fmt, va_list ap)
{
char *errstr;
if (vasprintf(&errstr, fmt, ap) < 0)
daemon_perr(fd, "cannot format log string", errno);
/*
* Not a paranoid write: see above.
*/
if (fd >= 0)
write(fd, errstr, strlen(errstr));
else
fprintf(stderr, "%s", errstr);
free(errstr);
}
/*
* Log a message down the synchronization pipe.
*
* If fd is < 0, write to stderr instead.
*/
_dt_printflike_(2, 3)
void
daemon_log(int fd, const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
daemon_vlog(fd, fmt, ap);
va_end(ap);
}
/*
* On failure, returns -1 in the parent.
*
* On success, returns the fd of the synchronization pipe in the child: write
* down it to indicate an error that should prevent daemonization, or close it
* to indicate success. That error will then trigger a return in the parent.
*/
int
daemonize(int close_fds)
{
size_t i;
struct sigaction sa = { 0 };
sigset_t mask;
int initialized[2];
if (close_fds)
if (close_range(3, ~0U, 0) < 0)
return -1; /* errno is set for us. */
if (pipe(initialized) < 0)
return -1; /* errno is set for us. */
/*
* Explicitly avoid checking for errors here -- not all signals can be
* reset, and we can't do anything if reset fails anyway.
*/
sa.sa_handler = SIG_DFL;
for (i = 0; i < _NSIG; i++)
(void) sigaction(i, &sa, NULL);
sigemptyset(&mask);
(void) sigprocmask(SIG_SETMASK, &mask, NULL);
switch (fork()) {
case -1: perror("cannot fork");
return -1;
case 0: break;
default:
{
char errsync[1024];
char *errsyncp = errsync;
int count = 0;
memset(errsync, 0, sizeof(errsync));
close(initialized[1]);
/*
* Wait for successful daemonization of the child. If it
* fails, print the message passed back as an error.
*
* Be very paranoid here: we know almost nothing about the state
* of the child *or* ourselves.
*/
for (errno = 0; (sizeof(errsync) - (errsyncp - errsync) >= 0) &&
(count > 0 || (count < 0 && errno == EINTR));
errno = 0) {
count = read(initialized[0], errsyncp,
sizeof(errsync) - (errsyncp - errsync));
if (count > 0)
errsyncp += count;
}
close(initialized[0]);
/*
* Child successfully initialized: terminate parent.
*/
if (errno == 0 && errsyncp == errsync)
_exit(0);
if (errno != 0) {
perror("cannot synchronize with daemon: state unknown");
return -1;
}
fprintf(stderr, "%s\n", errsync);
return -1;
}
}
close(initialized[0]);
(void) setsid();
switch (fork()) {
case -1: daemon_perr(initialized[1], "cannot fork", errno);
case 0: break;
default: _exit(0);
}
close(0);
if (open("/dev/null", O_RDWR) != 0)
daemon_perr(initialized[1], "cannot open /dev/null", errno);
if (dup2(0, 1) < 0 ||
dup2(0, 2) < 0)
daemon_perr(initialized[1], "cannot dup2 standard fds", errno);
umask(0);
if (chdir("/") < 0)
daemon_perr(initialized[1], "cannot chdir to /", errno);
return initialized[1];
}
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