From f9ceaedad0959c024e24ed5ad06280f2c9d7fa65 Mon Sep 17 00:00:00 2001
From: thorpej <thorpej@NetBSD.org>
Date: Sun, 10 Oct 2021 18:11:31 +0000
Subject: [PATCH] The knotes for EVFILT_SIGNAL and EVFILT_PROC are maintained
 on a single per-process list, and kern_event.c,v 1.129 has several KASSERT()s
 in various code paths that process this list related to the mixing of these
 two knote types.  This new unit test is designed specifically to exercise
 those KASSERT()s and thus validate their assumptions.

---
 tests/kernel/kqueue/t_sig.c | 84 +++++++++++++++++++++++++++++++++++--
 1 file changed, 81 insertions(+), 3 deletions(-)

diff --git a/tests/kernel/kqueue/t_sig.c b/tests/kernel/kqueue/t_sig.c
index e0efe825a46b..9d29cb8ed383 100644
--- a/tests/kernel/kqueue/t_sig.c
+++ b/tests/kernel/kqueue/t_sig.c
@@ -1,7 +1,7 @@
-/* $NetBSD: t_sig.c,v 1.3 2017/01/13 21:30:41 christos Exp $ */
+/* $NetBSD: t_sig.c,v 1.4 2021/10/10 18:11:31 thorpej Exp $ */
 
 /*-
- * Copyright (c) 2002, 2008 The NetBSD Foundation, Inc.
+ * Copyright (c) 2002, 2008, 2021 The NetBSD Foundation, Inc.
  * All rights reserved.
  *
  * This code is derived from software contributed to The NetBSD Foundation
@@ -32,7 +32,7 @@
 #include <sys/cdefs.h>
 __COPYRIGHT("@(#) Copyright (c) 2008\
  The NetBSD Foundation, inc. All rights reserved.");
-__RCSID("$NetBSD: t_sig.c,v 1.3 2017/01/13 21:30:41 christos Exp $");
+__RCSID("$NetBSD: t_sig.c,v 1.4 2021/10/10 18:11:31 thorpej Exp $");
 
 #include <sys/event.h>
 #include <sys/ioctl.h>
@@ -125,9 +125,87 @@ ATF_TC_BODY(sig, tc)
 	(void)printf("sig: finished successfully\n");
 }
 
+/*
+ * This test case exercises code paths in the kernel that KASSERT()
+ * some assumptions about EVFILT_SIGNAL and EVFILT_PROC implementation
+ * details.
+ */
+ATF_TC(sig_and_proc);
+ATF_TC_HEAD(sig_and_proc, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Validates implementation detail assumptions about "
+	    "EVFILT_SIGNAL and EVFILT_PROC");
+}
+ATF_TC_BODY(sig_and_proc, tc)
+{
+	struct kevent events[3];
+	pid_t pid;
+	int kq;
+
+	pid = fork();
+	ATF_REQUIRE(pid != -1);
+
+	if (pid == 0) {
+		/*
+		 * Child: create a kqueue and attach signal knotes
+		 * to curproc->p_klist.
+		 */
+		kq = kqueue();
+		ATF_REQUIRE(kq >= 0);
+
+		ATF_REQUIRE(signal(SIGUSR1, SIG_IGN) != SIG_ERR);
+		ATF_REQUIRE(signal(SIGUSR2, SIG_IGN) != SIG_ERR);
+
+		EV_SET(&events[0], SIGUSR1, EVFILT_SIGNAL, EV_ADD, 0, 0, NULL);
+		EV_SET(&events[1], SIGUSR2, EVFILT_SIGNAL, EV_ADD, 0, 0, NULL);
+
+		ATF_REQUIRE(kevent(kq, events, 2, &events[2], 1, NULL) == 1);
+		ATF_REQUIRE(events[2].filter == EVFILT_SIGNAL);
+		ATF_REQUIRE(events[2].ident == SIGUSR1);
+
+		/*
+		 * When we exit here, the kernel will close all of
+		 * its file descriptors (including our kq), which
+		 * will in turn remove the signal notes from
+		 * curproc->p_klist.
+		 *
+		 * Then, later on, the kernel will post a NOTE_EXIT
+		 * on our parent's kqueue using the proc note that
+		 * our parent attached to (our) curproc->p_klist.
+		 * That code path KASSERT()s that the signal knotes
+		 * have already been removed.
+		 */
+		_exit(0);
+	}
+
+	/*
+	 * Parent: create a kqueue and attach a proc note to
+	 * child->p_klist.
+	 */
+	kq = kqueue();
+	ATF_REQUIRE(kq >= 0);
+
+	EV_SET(&events[0], pid, EVFILT_PROC, EV_ADD, NOTE_EXIT, 0, NULL);
+
+	ATF_REQUIRE(kevent(kq, events, 1, NULL, 0, NULL) == 0);
+
+	/* Ensure we never see stale data. */
+	memset(events, 0, sizeof(events));
+
+	/* Signal child to exit. */
+	ATF_REQUIRE(kill(pid, SIGUSR1) == 0);
+
+	ATF_REQUIRE(kevent(kq, NULL, 0, events, 1, NULL) == 1);
+	ATF_REQUIRE(events[0].filter == EVFILT_PROC);
+	ATF_REQUIRE(events[0].ident == (uintptr_t)pid);
+	ATF_REQUIRE(events[0].fflags = NOTE_EXIT);
+}
+
 ATF_TP_ADD_TCS(tp)
 {
 	ATF_TP_ADD_TC(tp, sig);
+	ATF_TP_ADD_TC(tp, sig_and_proc);
 
 	return atf_no_error();
 }