*: introduce and use xvfork()

function                                             old     new   delta
time_main                                           1052    1285    +233
crontab_main                                         623     856    +233
ifupdown_main                                       2202    2403    +201
xvfork                                                 -      20     +20
passwd_main                                         1049    1053      +4
grave                                               1068    1066      -2
script_main                                          935     921     -14
vfork_or_die                                          20       -     -20
vfork_compressor                                     206     175     -31
open_as_user                                         109       -    -109
popen2                                               218       -    -218
edit_file                                            910     690    -220
run_command                                          268       -    -268
------------------------------------------------------------------------------
(add/remove: 1/4 grow/shrink: 4/4 up/down: 691/-882)         Total: -191 bytes

12 files changed, 18 insertions, 42 deletions

diff --git a/archival/libunarchive/open_transformer.c b/archival/libunarchive/open_transformer.c
index a6bc623..16ca6a5 100644
--- a/archival/libunarchive/open_transformer.c
+++ b/archival/libunarchive/open_transformer.c
@@ -25,9 +25,7 @@ int FAST_FUNC open_transformer(int src_fd,
 	if (pid == -1)
 		bb_perror_msg_and_die("can't fork");
 #else
-	pid = vfork();
-	if (pid == -1)
-		bb_perror_msg_and_die("can't vfork");
+	pid = xvfork();
 #endif
 
 	if (pid == 0) {
diff --git a/archival/tar.c b/archival/tar.c
index 526edb6..17ac6c5 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -536,9 +536,7 @@ static void NOINLINE vfork_compressor(int tar_fd, int gzip)
 	(void) &zip_exec;
 #endif
 
-	gzipPid = vfork();
-	if (gzipPid < 0)
-		bb_perror_msg_and_die("can't vfork");
+	gzipPid = xvfork();
 
 	if (gzipPid == 0) {
 		/* child */
diff --git a/debianutils/start_stop_daemon.c b/debianutils/start_stop_daemon.c
index 459fb77..f10572d 100644
--- a/debianutils/start_stop_daemon.c
+++ b/debianutils/start_stop_daemon.c
@@ -404,9 +404,7 @@ int start_stop_daemon_main(int argc ATTRIBUTE_UNUSED, char **argv)
 		/* DAEMON_DEVNULL_STDIO is superfluous -
 		 * it's always done by bb_daemonize() */
 #else
-		pid_t pid = vfork();
-		if (pid < 0) /* error */
-			bb_perror_msg_and_die("vfork");
+		pid_t pid = xvfork();
 		if (pid != 0) {
 			/* parent */
 			/* why _exit? the child may have changed the stack,
diff --git a/include/libbb.h b/include/libbb.h
index 54601f8..33e465c 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -719,6 +719,8 @@ int bb_execvp(const char *file, char *const argv[]) FAST_FUNC;
 #define BB_EXECLP(prog,cmd,...) execlp(prog,cmd, __VA_ARGS__)
 #endif
 
+pid_t xvfork(void) FAST_FUNC;
+
 /* NOMMU friendy fork+exec */
 pid_t spawn(char **argv) FAST_FUNC;
 pid_t xspawn(char **argv) FAST_FUNC;
diff --git a/libbb/Kbuild b/libbb/Kbuild
index 5cbecd5..5ace87c 100644
--- a/libbb/Kbuild
+++ b/libbb/Kbuild
@@ -109,6 +109,7 @@ lib-y += xfunc_die.o
 lib-y += xgetcwd.o
 lib-y += xgethostbyname.o
 lib-y += xreadlink.o
+lib-y += xvfork.o
 
 # conditionally compiled objects:
 lib-$(CONFIG_FEATURE_MOUNT_LOOP) += loop.o
diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c
index 37d4c27..9baa813 100644
--- a/libbb/vfork_daemon_rexec.c
+++ b/libbb/vfork_daemon_rexec.c
@@ -226,9 +226,7 @@ void FAST_FUNC forkexit_or_rexec(char **argv)
 	if (re_execed)
 		return;
 
-	pid = vfork();
-	if (pid < 0) /* wtf? */
-		bb_perror_msg_and_die("vfork");
+	pid = xvfork();
 	if (pid) /* parent */
 		exit(EXIT_SUCCESS);
 	/* child - re-exec ourself */
diff --git a/miscutils/crontab.c b/miscutils/crontab.c
index dc3179d..4bba9fb 100644
--- a/miscutils/crontab.c
+++ b/miscutils/crontab.c
@@ -38,10 +38,8 @@ static void change_user(const struct passwd *pas)
 static void edit_file(const struct passwd *pas, const char *file)
 {
 	const char *ptr;
-	int pid = vfork();
+	int pid = xvfork();
 
-	if (pid < 0) /* failure */
-		bb_perror_msg_and_die("vfork");
 	if (pid) { /* parent */
 		wait4pid(pid);
 		return;
@@ -65,9 +63,7 @@ static int open_as_user(const struct passwd *pas, const char *file)
 	pid_t pid;
 	char c;
 
-	pid = vfork();
-	if (pid < 0) /* ERROR */
-		bb_perror_msg_and_die("vfork");
+	pid = xvfork();
 	if (pid) { /* PARENT */
 		if (wait4pid(pid) == 0) {
 			/* exitcode 0: child says it can read */
diff --git a/miscutils/time.c b/miscutils/time.c
index a6d158c..104548c 100644
--- a/miscutils/time.c
+++ b/miscutils/time.c
@@ -372,9 +372,7 @@ static void run_command(char *const *cmd, resource_t *resp)
 	void (*quit_signal)(int);
 
 	resp->elapsed_ms = monotonic_us() / 1000;
-	pid = vfork();		/* Run CMD as child process.  */
-	if (pid < 0)
-		bb_error_msg_and_die("cannot fork");
+	pid = xvfork();		/* Run CMD as child process.  */
 	if (pid == 0) {	/* If child.  */
 		/* Don't cast execvp arguments; that causes errors on some systems,
 		   versus merely warnings if the cast is left off.  */
diff --git a/networking/ifupdown.c b/networking/ifupdown.c
index c123918..8caff3f 100644
--- a/networking/ifupdown.c
+++ b/networking/ifupdown.c
@@ -1008,12 +1008,9 @@ static int popen2(FILE **in, FILE **out, char *command, char *param)
 	xpiped_pair(outfd);
 
 	fflush(NULL);
-	pid = vfork();
+	pid = xvfork();
 
-	switch (pid) {
-	case -1:  /* failure */
-		bb_perror_msg_and_die("vfork");
-	case 0:  /* child */
+	if (pid == 0) { /* child */
 		/* NB: close _first_, then move fds! */
 		close(infd.wr);
 		close(outfd.rd);
diff --git a/networking/sendmail.c b/networking/sendmail.c
index 1c23ca2..c195cc0 100644
--- a/networking/sendmail.c
+++ b/networking/sendmail.c
@@ -120,15 +120,6 @@ static void signal_handler(int signo)
 #undef err
 }
 
-/* libbb candidate */
-static pid_t vfork_or_die(void)
-{
-	pid_t pid = vfork();
-	if (pid < 0)
-		bb_perror_msg_and_die("vfork");
-	return pid;
-}
-
 static void launch_helper(const char **argv)
 {
 	// setup vanilla unidirectional pipes interchange
@@ -137,7 +128,7 @@ static void launch_helper(const char **argv)
 
 	xpipe(pipes);
 	xpipe(pipes+2);
-	helper_pid = vfork_or_die();
+	helper_pid = xvfork();
 	idx = (!helper_pid) * 2;
 	xdup2(pipes[idx], STDIN_FILENO);
 	xdup2(pipes[3-idx], STDOUT_FILENO);
diff --git a/shell/hush.c b/shell/hush.c
index 72186f9..59d8f3f 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -3096,9 +3096,11 @@ static FILE *generate_stream_from_list(struct pipe *head)
  * huge=`cat TESTFILE` # will block here forever
  * echo OK
  */
-	pid = BB_MMU ? fork() : vfork();
+	pid = BB_MMU ? fork() : xvfork();
+#if BB_MMU
 	if (pid < 0)
-		bb_perror_msg_and_die(BB_MMU ? "fork" : "vfork");
+		bb_perror_msg_and_die("fork");
+#endif
 	if (pid == 0) { /* child */
 		if (ENABLE_HUSH_JOB)
 			die_sleep = 0; /* let nofork's xfuncs die */
diff --git a/util-linux/script.c b/util-linux/script.c
index e70294e..a6c1ab8 100644
--- a/util-linux/script.c
+++ b/util-linux/script.c
@@ -87,10 +87,7 @@ int script_main(int argc ATTRIBUTE_UNUSED, char **argv)
 
 	/* TODO: SIGWINCH? pass window size changes down to slave? */
 
-	child_pid = vfork();
-	if (child_pid < 0) {
-		bb_perror_msg_and_die("vfork");
-	}
+	child_pid = xvfork();
 
 	if (child_pid) {
 		/* parent */