Ensure that the kill signal undergoing testing is not ignored.

ok bluhm@

Author: anton

src/regress/lib/libc/sys/t_kill.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: t_kill.c,v 1.1.1.1 2019/11/19 19:57:03 bluhm Exp $	*/
+/*	$OpenBSD: t_kill.c,v 1.2 2021/07/29 15:33:17 anton Exp $	*/
 /* $NetBSD: t_kill.c,v 1.1 2011/07/07 06:57:53 jruoho Exp $ */
 
 /*-
@@ -60,6 +60,17 @@ ATF_TC_BODY(kill_basic, tc)
 	int sta;
 
 	for (i = 0; i < __arraycount(sig); i++) {
+		struct sigaction act, oact;
+
+		/* Ensure the signal is not ignored. */
+		if (sig[i] != SIGKILL) {
+			memset(&act, 0, sizeof(act));
+			act.sa_handler = SIG_DFL;
+			ATF_REQUIRE(sigaction(sig[i], &act, &oact) == 0);
+		} else {
+			ATF_REQUIRE(sigaction(sig[i], &act, &oact) != 0);
+			ATF_REQUIRE(errno == EINVAL);
+		}
 
 		pid = fork();
 		ATF_REQUIRE(pid >= 0);
@@ -78,6 +89,9 @@ ATF_TC_BODY(kill_basic, tc)
 
 		if (WIFSIGNALED(sta) == 0 || WTERMSIG(sta) != sig[i])
 			atf_tc_fail("kill(2) failed to kill child");
+
+		if (sig[i] != SIGKILL)
+			ATF_REQUIRE(sigaction(sig[i], &oact, NULL) == 0);
 	}
 }