From 7d1ffcb72ac881b52c8b79bedbb120e92ee7141b Mon Sep 17 00:00:00 2001
From: Peter Wemm <peter@FreeBSD.org>
Date: Tue, 13 Aug 2013 20:38:55 +0000
Subject: [PATCH] vfork(2) was listed as deprecated in 1994 (r1573) and was the
 false reports of its impending demise were removed in 2009 (r199257).

However, in 1996 (r16117) system(3) was switched from vfork(2) to
fork(2) based partly on this.  Switch back to vfork(2).  This has a
dramatic effect in cases of extreme mmap use - such as excessive
abuse (500+) of shared libraries.

popen(3) has used vfork(2) for a while.  vfork(2) isn't going anywhere.
---
 lib/libc/stdlib/system.c | 38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/lib/libc/stdlib/system.c b/lib/libc/stdlib/system.c
index b552a63fd904..64a544714564 100644
--- a/lib/libc/stdlib/system.c
+++ b/lib/libc/stdlib/system.c
@@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$");
 #include <signal.h>
 #include <stdlib.h>
 #include <stddef.h>
+#include <string.h>
 #include <unistd.h>
 #include <paths.h>
 #include <errno.h>
@@ -56,37 +57,36 @@ __system(const char *command)
 	if (!command)		/* just checking... */
 		return(1);
 
-	/*
-	 * Ignore SIGINT and SIGQUIT, block SIGCHLD. Remember to save
-	 * existing signal dispositions.
-	 */
-	ign.sa_handler = SIG_IGN;
-	(void)sigemptyset(&ign.sa_mask);
-	ign.sa_flags = 0;
-	(void)_sigaction(SIGINT, &ign, &intact);
-	(void)_sigaction(SIGQUIT, &ign, &quitact);
 	(void)sigemptyset(&newsigblock);
 	(void)sigaddset(&newsigblock, SIGCHLD);
 	(void)_sigprocmask(SIG_BLOCK, &newsigblock, &oldsigblock);
-	switch(pid = fork()) {
+	switch(pid = vfork()) {
 	case -1:			/* error */
-		break;
+		(void)_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);
+		return (-1);
 	case 0:				/* child */
 		/*
 		 * Restore original signal dispositions and exec the command.
 		 */
-		(void)_sigaction(SIGINT, &intact, NULL);
-		(void)_sigaction(SIGQUIT,  &quitact, NULL);
 		(void)_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);
 		execl(_PATH_BSHELL, "sh", "-c", command, (char *)NULL);
 		_exit(127);
-	default:			/* parent */
-		savedpid = pid;
-		do {
-			pid = _wait4(savedpid, &pstat, 0, (struct rusage *)0);
-		} while (pid == -1 && errno == EINTR);
-		break;
 	}
+	/* 
+	 * If we are running means that the child has either completed
+	 * its execve, or has failed.
+	 * Block SIGINT/QUIT because sh -c handles it and wait for
+	 * it to clean up.
+	 */
+	memset(&ign, 0, sizeof(ign));
+	ign.sa_handler = SIG_IGN;
+	(void)sigemptyset(&ign.sa_mask);
+	(void)_sigaction(SIGINT, &ign, &intact);
+	(void)_sigaction(SIGQUIT, &ign, &quitact);
+	savedpid = pid;
+	do {
+		pid = _wait4(savedpid, &pstat, 0, (struct rusage *)0);
+	} while (pid == -1 && errno == EINTR);
 	(void)_sigaction(SIGINT, &intact, NULL);
 	(void)_sigaction(SIGQUIT,  &quitact, NULL);
 	(void)_sigprocmask(SIG_SETMASK, &oldsigblock, NULL);