remove global "jmp_buf die_jmp" from !FEATURE_PREFER_APPLETS builds

function                                             old     new   delta
xfunc_has_died                                         -      21     +21
sleep_much                                             -      12     +12
sleep10                                                -       9      +9
die_func                                               -       4      +4
fflush_stdout_and_exit                                35      36      +1
builtin_type                                         121     119      -2
die_sleep                                              4       -      -4
xfunc_die                                             60      24     -36
hush_main                                           1128    1011    -117
die_jmp                                              156       -    -156
------------------------------------------------------------------------------
(add/remove: 4/2 grow/shrink: 1/3 up/down: 47/-315)          Total: -268 bytes
   text	   data	    bss	    dec	    hex	filename
 939992	    992	  17652	 958636	  ea0ac	busybox_old
 939880	    992	  17496	 958368	  e9fa0	busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 25 insertions, 14 deletions

diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c
index ed1f86f0c..d6ca7b263 100644
--- a/libbb/vfork_daemon_rexec.c
+++ b/libbb/vfork_daemon_rexec.c
@@ -69,28 +69,44 @@ pid_t FAST_FUNC xspawn(char **argv)
 }
 
 #if ENABLE_FEATURE_PREFER_APPLETS
+static jmp_buf die_jmp;
+static void jump(void)
+{
+	/* Special case. We arrive here if NOFORK applet
+	 * calls xfunc, which then decides to die.
+	 * We don't die, but jump instead back to caller.
+	 * NOFORK applets still cannot carelessly call xfuncs:
+	 * p = xmalloc(10);
+	 * q = xmalloc(10); // BUG! if this dies, we leak p!
+	 */
+	/* | 0x100 allows to pass zero exitcode (longjmp can't pass 0).
+	 * This works because exitcodes are bytes,
+	 * run_nofork_applet() ensures that by "& 0xff" */
+	longjmp(die_jmp, xfunc_error_retval | 0x100);
+}
+
 struct nofork_save_area {
 	jmp_buf die_jmp;
+	void (*die_func)(void);
 	const char *applet_name;
 	uint32_t option_mask32;
-	int die_sleep;
 	uint8_t xfunc_error_retval;
 };
 static void save_nofork_data(struct nofork_save_area *save)
 {
 	memcpy(&save->die_jmp, &die_jmp, sizeof(die_jmp));
+	save->die_func = die_func;
 	save->applet_name = applet_name;
-	save->xfunc_error_retval = xfunc_error_retval;
 	save->option_mask32 = option_mask32;
-	save->die_sleep = die_sleep;
+	save->xfunc_error_retval = xfunc_error_retval;
 }
 static void restore_nofork_data(struct nofork_save_area *save)
 {
 	memcpy(&die_jmp, &save->die_jmp, sizeof(die_jmp));
+	die_func = save->die_func;
 	applet_name = save->applet_name;
-	xfunc_error_retval = save->xfunc_error_retval;
 	option_mask32 = save->option_mask32;
-	die_sleep = save->die_sleep;
+	xfunc_error_retval = save->xfunc_error_retval;
 }
 
 int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
@@ -133,11 +149,8 @@ int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
 	while (argv[argc])
 		argc++;
 
-	/* Special flag for xfunc_die(). If xfunc will "die"
-	 * in NOFORK applet, xfunc_die() sees negative
-	 * die_sleep and longjmp here instead. */
-	die_sleep = -1;
-
+	/* If xfunc "dies" in NOFORK applet, die_func longjmp's here instead */
+	die_func = jump;
 	rc = setjmp(die_jmp);
 	if (!rc) {
 		/* Some callers (xargs)
@@ -146,10 +159,8 @@ int FAST_FUNC run_nofork_applet(int applet_no, char **argv)
 		memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0]));
 		/* Finally we can call NOFORK applet's main() */
 		rc = applet_main[applet_no](argc, tmp_argv);
-	} else { /* xfunc died in NOFORK applet */
-		/* in case they meant to return 0... */
-		if (rc == -2222)
-			rc = 0;
+	} else {
+		/* xfunc died in NOFORK applet */
 	}
 
 	/* Restoring some globals */