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286 lines
6.4 KiB
C
286 lines
6.4 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Rexec program for system have fork() as vfork() with foreground option
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*
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* Copyright (C) Vladimir N. Oleynik <dzo@simtreas.ru>
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* Copyright (C) 2003 Russ Dill <Russ.Dill@asu.edu>
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*
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* daemon() portion taken from uClibc:
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*
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Modified for uClibc by Erik Andersen <andersee@debian.org>
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*
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* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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*/
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#include <paths.h>
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#include "busybox.h" /* for struct bb_applet */
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/* This does a fork/exec in one call, using vfork(). Returns PID of new child,
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* -1 for failure. Runs argv[0], searching path if that has no / in it. */
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pid_t spawn(char **argv)
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{
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/* Compiler should not optimize stores here */
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volatile int failed;
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pid_t pid;
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// Ain't it a good place to fflush(NULL)?
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/* Be nice to nommu machines. */
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failed = 0;
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pid = vfork();
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if (pid < 0) /* error */
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return pid;
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if (!pid) { /* child */
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/* This macro is ok - it doesn't do NOEXEC/NOFORK tricks */
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BB_EXECVP(argv[0], argv);
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/* We are (maybe) sharing a stack with blocked parent,
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* let parent know we failed and then exit to unblock parent
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* (but don't run atexit() stuff, which would screw up parent.)
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*/
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failed = errno;
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_exit(111);
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}
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/* parent */
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/* Unfortunately, this is not reliable: according to standards
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* vfork() can be equivalent to fork() and we won't see value
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* of 'failed'.
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* Interested party can wait on pid and learn exit code.
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* If 111 - then it (most probably) failed to exec */
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if (failed) {
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errno = failed;
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return -1;
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}
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return pid;
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}
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/* Die with an error message if we can't spawn a child process. */
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pid_t xspawn(char **argv)
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{
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pid_t pid = spawn(argv);
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if (pid < 0)
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bb_perror_msg_and_die("%s", *argv);
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return pid;
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}
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// Wait for the specified child PID to exit, returning child's error return.
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int wait4pid(int pid)
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{
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int status;
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if (pid <= 0) {
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/*errno = ECHILD; -- wrong. */
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/* we expect errno to be already set from failed [v]fork/exec */
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return -1;
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}
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if (waitpid(pid, &status, 0) == -1)
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return -1;
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if (WIFEXITED(status))
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return WEXITSTATUS(status);
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if (WIFSIGNALED(status))
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return WTERMSIG(status) + 1000;
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return 0;
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}
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int wait_nohang(int *wstat)
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{
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return waitpid(-1, wstat, WNOHANG);
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}
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int wait_pid(int *wstat, int pid)
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{
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int r;
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do
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r = waitpid(pid, wstat, 0);
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while ((r == -1) && (errno == EINTR));
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return r;
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}
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#if ENABLE_FEATURE_PREFER_APPLETS
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void save_nofork_data(struct nofork_save_area *save)
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{
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memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
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save->current_applet = current_applet;
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save->xfunc_error_retval = xfunc_error_retval;
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save->option_mask32 = option_mask32;
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save->die_sleep = die_sleep;
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save->saved = 1;
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}
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void restore_nofork_data(struct nofork_save_area *save)
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{
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memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
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current_applet = save->current_applet;
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xfunc_error_retval = save->xfunc_error_retval;
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option_mask32 = save->option_mask32;
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die_sleep = save->die_sleep;
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applet_name = current_applet->name;
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}
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int run_nofork_applet_prime(struct nofork_save_area *old, const struct bb_applet *a, char **argv)
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{
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int rc, argc;
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current_applet = a;
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applet_name = a->name;
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xfunc_error_retval = EXIT_FAILURE;
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/*option_mask32 = 0; - not needed */
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/* special flag for xfunc_die(). If xfunc will "die"
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* in NOFORK applet, xfunc_die() sees negative
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* die_sleep and longjmp here instead. */
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die_sleep = -1;
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argc = 1;
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while (argv[argc])
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argc++;
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rc = setjmp(die_jmp);
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if (!rc) {
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/* Some callers (xargs)
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* need argv untouched because they free argv[i]! */
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char *tmp_argv[argc+1];
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memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
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/* Finally we can call NOFORK applet's main() */
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rc = a->main(argc, tmp_argv);
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} else { /* xfunc died in NOFORK applet */
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/* in case they meant to return 0... */
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if (rc == -2222)
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rc = 0;
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}
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/* Restoring globals */
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restore_nofork_data(old);
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return rc;
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}
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int run_nofork_applet(const struct bb_applet *a, char **argv)
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{
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struct nofork_save_area old;
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/* Saving globals */
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save_nofork_data(&old);
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return run_nofork_applet_prime(&old, a, argv);
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}
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#endif /* FEATURE_PREFER_APPLETS */
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int spawn_and_wait(char **argv)
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{
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int rc;
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#if ENABLE_FEATURE_PREFER_APPLETS
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const struct bb_applet *a = find_applet_by_name(argv[0]);
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if (a && (a->nofork
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#if BB_MMU
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|| a->noexec /* NOEXEC trick needs fork() */
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#endif
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)) {
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#if BB_MMU
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if (a->nofork)
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#endif
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{
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return run_nofork_applet(a, argv);
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}
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#if BB_MMU
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/* MMU only */
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/* a->noexec is true */
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rc = fork();
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if (rc) /* parent or error */
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return wait4pid(rc);
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/* child */
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xfunc_error_retval = EXIT_FAILURE;
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current_applet = a;
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run_current_applet_and_exit(argv);
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#endif
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}
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#endif /* FEATURE_PREFER_APPLETS */
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rc = spawn(argv);
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return wait4pid(rc);
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}
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#if !BB_MMU
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void re_exec(char **argv)
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{
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/* high-order bit of first char in argv[0] is a hidden
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* "we have (already) re-execed, don't do it again" flag */
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argv[0][0] |= 0x80;
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execv(bb_busybox_exec_path, argv);
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bb_perror_msg_and_die("exec %s", bb_busybox_exec_path);
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}
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void forkexit_or_rexec(char **argv)
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{
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pid_t pid;
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/* Maybe we are already re-execed and come here again? */
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if (re_execed)
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return;
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pid = vfork();
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if (pid < 0) /* wtf? */
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bb_perror_msg_and_die("vfork");
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if (pid) /* parent */
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exit(0);
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/* child - re-exec ourself */
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re_exec(argv);
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}
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#else
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/* Dance around (void)...*/
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#undef forkexit_or_rexec
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void forkexit_or_rexec(void)
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{
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pid_t pid;
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pid = fork();
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if (pid < 0) /* wtf? */
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bb_perror_msg_and_die("fork");
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if (pid) /* parent */
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exit(0);
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/* child */
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}
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#define forkexit_or_rexec(argv) forkexit_or_rexec()
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#endif
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/* Due to a #define in libbb.h on MMU systems we actually have 1 argument -
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* char **argv "vanishes" */
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void bb_daemonize_or_rexec(int flags, char **argv)
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{
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int fd;
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if (flags & DAEMON_CHDIR_ROOT)
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xchdir("/");
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if (flags & DAEMON_DEVNULL_STDIO) {
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close(0);
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close(1);
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close(2);
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}
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fd = xopen(bb_dev_null, O_RDWR);
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while ((unsigned)fd < 2)
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fd = dup(fd); /* have 0,1,2 open at least to /dev/null */
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if (!(flags & DAEMON_ONLY_SANITIZE)) {
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forkexit_or_rexec(argv);
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/* if daemonizing, make sure we detach from stdio & ctty */
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setsid();
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dup2(fd, 0);
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dup2(fd, 1);
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dup2(fd, 2);
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}
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while (fd > 2) {
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close(fd--);
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if (!(flags & DAEMON_CLOSE_EXTRA_FDS))
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return;
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/* else close everything after fd#2 */
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}
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}
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void bb_sanitize_stdio(void)
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{
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bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE, NULL);
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}
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