[PATCH v8 04/14] libbb: implement reset_all_signals

[Nadav Tasher]

This commit adds the reset_all_signals() function,
which resets all custom signal handlers to the default
signal handler (SIG_DFL).

Signed-off-by: Nadav Tasher <tashernadav at gmail.com>
---
 include/libbb.h |  2 ++
 libbb/signals.c | 26 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/libbb.h b/include/libbb.h
index ed2af5af2..11d2c27ec 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -649,6 +649,8 @@ int sigprocmask2(int how, sigset_t *set) FAST_FUNC;
 /* Standard handler which just records signo */
 extern smallint bb_got_signal;
 void record_signo(int signo); /* not FAST_FUNC! */
+/* Resets all signal handlers just like exec() does */
+void reset_all_signals(void) FAST_FUNC;
 
 
 void xsetgid(gid_t gid) FAST_FUNC;
diff --git a/libbb/signals.c b/libbb/signals.c
index 0bebc847d..460befd75 100644
--- a/libbb/signals.c
+++ b/libbb/signals.c
@@ -128,3 +128,29 @@ void FAST_FUNC signal_no_SA_RESTART_empty_mask(int sig, void (*handler)(int))
 	sa.sa_handler = handler;
 	sigaction_set(sig, &sa);
 }
+
+void FAST_FUNC reset_all_signals(void)
+{
+    struct sigaction sa;
+    memset(&sa, 0, sizeof(sa));
+
+	/* used as the default sigaction */
+    sa.sa_handler = SIG_DFL;
+
+    for (int sig = 1; sig < NSIG; ++sig) {
+        struct sigaction old;
+
+		/* returns 0 on success*/
+        if (sigaction(sig, NULL, &old) != 0)
+			continue;
+
+		if (old.sa_handler == SIG_IGN)
+			continue;
+
+		if (old.sa_handler == SIG_DFL)
+			continue;
+		
+		/* change signal handler to default */
+		sigaction(sig, &sa, NULL);
+    }
+}
\ No newline at end of file
-- 
2.43.0