tests: kern: add some tests for recently added logsigexit

We don't bother tweaking the sysctl in these tests, we'll just try with
it forced both on and off via proccontrol(1).  This could be problematic
in the face of pid wrapping if we got really unfortunate, but the
potential solutions need careful consideration- you probably don't want
to assume a certain velocity of messages into syslog, so just checking
the last N lines is probably similarly flakey.

tests/sys/kern/Makefile

@@ -58,6 +58,7 @@ ATF_TESTS_C+=	sigsys
 TEST_METADATA.sigsys+=	is_exclusive="true"
 
 ATF_TESTS_SH+=	coredump_phnum_test
+ATF_TESTS_SH+=	logsigexit_test
 ATF_TESTS_SH+=	sonewconn_overflow
 TEST_METADATA.sonewconn_overflow+=	required_programs="python"
 TEST_METADATA.sonewconn_overflow+=	required_user="root"

tests/sys/kern/logsigexit_test.sh

@@ -0,0 +1,36 @@
+#
+# Copyright (c) 2024 Kyle Evans <[email protected]>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+
+atf_test_case basic
+basic_body()
+{
+
+	# SIGABRT carefully chosen to avoid issues when run under Kyua.  No
+	# matter the value of the global kern.logsigexit, these should force
+	# the messages as appropriate and we'll all be happy.
+	proccontrol -m logsigexit -s enable \
+	    sh -c 'echo $$ > enabled.out; kill -ABRT $$'
+	proccontrol -m logsigexit -s disable \
+	    sh -c 'echo $$ > disabled.out; kill -ABRT $$'
+
+	atf_check test -s enabled.out
+	atf_check test -s disabled.out
+
+	read enpid < enabled.out
+	read dispid < disabled.out
+
+	1>&2 echo "$enpid"
+	1>&2 echo "$dispid"
+
+	atf_check grep -Eq "$enpid.+exited on signal" /var/log/messages
+	atf_check -s not-exit:0 \
+	    grep -Eq "$dispid.+exited on signal" /var/log/messages
+}
+
+atf_init_test_cases()
+{
+	atf_add_test_case basic
+}