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/* vi: set sw=4 ts=4: */
/*
* Rexec program for system have fork() as vfork() with foreground option
*
* Copyright (C) Vladimir N. Oleynik <dzo@simtreas.ru>
* Copyright (C) 2003 Russ Dill <Russ.Dill@asu.edu>
*
* daemon() portion taken from uClibc:
*
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* Modified for uClibc by Erik Andersen <andersee@debian.org>
*
* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
*/
#include <paths.h>
#include "busybox.h" /* for struct bb_applet */
/* This does a fork/exec in one call, using vfork(). Returns PID of new child,
* -1 for failure. Runs argv[0], searching path if that has no / in it. */
pid_t spawn(char **argv)
{
/* Compiler should not optimize stores here */
volatile int failed;
pid_t pid;
// Ain't it a good place to fflush(NULL)?
/* Be nice to nommu machines. */
failed = 0;
pid = vfork();
if (pid < 0) /* error */
return pid;
if (!pid) { /* child */
/* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */
BB_EXECVP(argv[0], argv);
/* We are (maybe) sharing a stack with blocked parent,
* let parent know we failed and then exit to unblock parent
* (but don't run atexit() stuff, which would screw up parent.)
*/
failed = errno;
_exit(111);
}
/* parent */
/* Unfortunately, this is not reliable: according to standards
* vfork() can be equivalent to fork() and we won't see value
* of 'failed'.
* Interested party can wait on pid and learn exit code.
* If 111 - then it (most probably) failed to exec */
if (failed) {
errno = failed;
return -1;
}
return pid;
}
/* Die with an error message if we can't spawn a child process. */
pid_t xspawn(char **argv)
{
pid_t pid = spawn(argv);
if (pid < 0)
bb_perror_msg_and_die("%s", *argv);
return pid;
}
// Wait for the specified child PID to exit, returning child's error return.
int wait4pid(int pid)
{
int status;
if (pid <= 0) {
/*errno = ECHILD; -- wrong. */
/* we expect errno to be already set from failed [v]fork/exec */
return -1;
}
if (waitpid(pid, &status, 0) == -1)
return -1;
if (WIFEXITED(status))
return WEXITSTATUS(status);
if (WIFSIGNALED(status))
return WTERMSIG(status) + 1000;
return 0;
}
int wait_nohang(int *wstat)
{
return waitpid(-1, wstat, WNOHANG);
}
int wait_pid(int *wstat, int pid)
{
int r;
do
r = waitpid(pid, wstat, 0);
while ((r == -1) && (errno == EINTR));
return r;
}
int spawn_and_wait(char **argv)
{
#if ENABLE_FEATURE_EXEC_PREFER_APPLETS
int rc;
const struct bb_applet *a = find_applet_by_name(argv[0]);
if (a && (a->nofork
#ifndef BB_NOMMU
|| a->noexec /* NOEXEC cannot be used on NOMMU */
#endif
)) {
int argc = 1;
char **pp = argv;
while (*++pp)
argc++;
#ifndef BB_NOMMU
if (a->nofork)
#endif
{
int old_sleep = die_sleep;
int old_x = xfunc_error_retval;
die_sleep = -1; /* special flag */
/* xfunc_die() checks for it */
rc = setjmp(die_jmp);
if (!rc) {
const struct bb_applet *old_a = current_applet;
current_applet = a;
applet_name = a->name;
// what else should we save/restore?
// TODO: what if applet will mangle argv vector?
// xargs needs argv untouched because it frees the vector!
// shouldn't we pass a copy?
rc = a->main(argc, argv);
current_applet = old_a;
applet_name = old_a->name;
} else {
/* xfunc died in NOFORK applet */
if (rc == -111)
rc = 0;
}
die_sleep = old_sleep;
xfunc_error_retval = old_x;
return rc;
}
#ifndef BB_NOMMU /* MMU only */
/* a->noexec is true */
rc = fork();
if (rc)
goto w;
/* child */
current_applet = a;
run_current_applet_and_exit(argc, argv);
#endif
}
rc = spawn(argv);
w:
return wait4pid(rc);
#else /* !FEATURE_EXEC_PREFER_APPLETS */
return wait4pid(spawn(argv));
#endif
}
#ifdef BB_NOMMU
void forkexit_or_rexec(char **argv)
{
pid_t pid;
/* Maybe we are already re-execed and come here again? */
if (re_execed)
return;
pid = vfork();
if (pid < 0) /* wtf? */
bb_perror_msg_and_die("vfork");
if (pid) /* parent */
exit(0);
/* child - re-exec ourself */
/* high-order bit of first char in argv[0] is a hidden
* "we have (alrealy) re-execed, don't do it again" flag */
argv[0][0] |= 0x80;
execv(CONFIG_BUSYBOX_EXEC_PATH, argv);
bb_perror_msg_and_die("exec %s", CONFIG_BUSYBOX_EXEC_PATH);
}
#else
/* Dance around (void)...*/
#undef forkexit_or_rexec
void forkexit_or_rexec(void)
{
pid_t pid;
pid = fork();
if (pid < 0) /* wtf? */
bb_perror_msg_and_die("fork");
if (pid) /* parent */
exit(0);
/* child */
}
#define forkexit_or_rexec(argv) forkexit_or_rexec()
#endif
/* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
* char **argv "vanishes" */
void bb_daemonize_or_rexec(int flags, char **argv)
{
int fd;
fd = xopen(bb_dev_null, O_RDWR);
if (flags & DAEMON_CHDIR_ROOT)
xchdir("/");
if (flags & DAEMON_DEVNULL_STDIO) {
close(0);
close(1);
close(2);
}
while ((unsigned)fd < 2)
fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
if (!(flags & DAEMON_ONLY_SANITIZE)) {
forkexit_or_rexec(argv);
/* if daemonizing, make sure we detach from stdio */
setsid();
dup2(fd, 0);
dup2(fd, 1);
dup2(fd, 2);
}
if (fd > 2)
close(fd--);
if (flags & DAEMON_CLOSE_EXTRA_FDS)
while (fd > 2)
close(fd--); /* close everything after fd#2 */
}
void bb_sanitize_stdio(void)
{
bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);
}
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