[PATCH v4 7/8] vfork_daemon_rexec: implement bb_system using spawn_and_wait

[Nadav Tasher]

Implemented bb_system using spawn_and_wait in conjuction with "sh",
to allow bb_system to execute the internal shell when using the
FEATURE_PREFER_APPLETS config option.

When FEATURE_PREFER_APPLETS is disabled, libc "system()" is used.

Signed-off-by: Nadav Tasher <tashernadav at gmail.com>
---
 include/libbb.h            |  1 +
 libbb/vfork_daemon_rexec.c | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/include/libbb.h b/include/libbb.h
index 39ca6d811..e04321dc8 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1280,6 +1280,7 @@ int wait_for_exitstatus(pid_t pid) FAST_FUNC;
 /************************************************************************/
 /* Same as wait4pid(spawn(argv)), but with NOFORK/NOEXEC if configured: */
 int spawn_and_wait(char **argv) FAST_FUNC;
+int bb_system(const char *command) FAST_FUNC;
 /* Does NOT check that applet is NOFORK, just blindly runs it */
 int run_nofork_applet(int applet_no, char **argv) FAST_FUNC;
 void run_noexec_applet_and_exit(int a, const char *name, char **argv) NORETURN FAST_FUNC;
diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c
index 43f09f2f1..5dd92abe9 100644
--- a/libbb/vfork_daemon_rexec.c
+++ b/libbb/vfork_daemon_rexec.c
@@ -249,6 +249,18 @@ int FAST_FUNC spawn_and_wait(char **argv)
 	return wait4pid(rc);
 }
 
+int FAST_FUNC bb_system(const char *command) {
+#if ENABLE_FEATURE_PREFER_APPLETS
+	/* we use sh because it might launch ash */
+	const char* system_argv[] = {"sh", "-c", command, NULL};
+
+	/* just use spawn and wait - returns the exit code */
+	return spawn_and_wait((char**) system_argv);
+#else
+	return system(command);
+#endif
+}
+
 #if !BB_MMU
 void FAST_FUNC re_exec(char **argv)
 {
-- 
2.43.0