lib/test_sysctl: support testing of sysctl. boot parameter

Testing is done by a new parameter debug.test_sysctl.boot_int which
defaults to 0 and it's expected that the tester passes a boot parameter
that sets it to 1.  The test checks if it's set to 1.

To distinguish true failure from parameter not being set, the test
checks /proc/cmdline for the expected parameter, and whether test_sysctl
is built-in and not a module.

[vbabka@suse.cz: skip the new test if boot_int sysctl is not present]
  Link: http://lkml.kernel.org/r/305af605-1e60-cf84-fada-6ce1ca37c102@suse.czSigned-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Guilherme G . Piccoli" <gpiccoli@canonical.com>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Ivan Teterevkov <ivan.teterevkov@nutanix.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200427180433.7029-6-vbabka@suse.czSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/test_sysctl.c

@@ -44,6 +44,8 @@ struct test_sysctl_data {
 	int int_0002;
 	int int_0003[4];
 
+	int boot_int;
+
 	unsigned int uint_0001;
 
 	char string_0001[65];
@@ -61,6 +63,8 @@ static struct test_sysctl_data test_data = {
 	.int_0003[2] = 2,
 	.int_0003[3] = 3,
 
+	.boot_int = 0,
+
 	.uint_0001 = 314,
 
 	.string_0001 = "(none)",
@@ -91,6 +95,15 @@ static struct ctl_table test_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
+	{
+		.procname	= "boot_int",
+		.data		= &test_data.boot_int,
+		.maxlen		= sizeof(test_data.boot_int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= SYSCTL_ZERO,
+		.extra2         = SYSCTL_ONE,
+	},
 	{
 		.procname	= "uint_0001",
 		.data		= &test_data.uint_0001,

tools/testing/selftests/sysctl/sysctl.sh

@@ -39,6 +39,7 @@ ALL_TESTS="$ALL_TESTS 0003:1:1:int_0002"
 ALL_TESTS="$ALL_TESTS 0004:1:1:uint_0001"
 ALL_TESTS="$ALL_TESTS 0005:3:1:int_0003"
 ALL_TESTS="$ALL_TESTS 0006:50:1:bitmap_0001"
+ALL_TESTS="$ALL_TESTS 0007:1:1:boot_int"
 
 test_modprobe()
 {
@@ -752,6 +753,46 @@ sysctl_test_0006()
 	run_bitmaptest
 }
 
+sysctl_test_0007()
+{
+	TARGET="${SYSCTL}/boot_int"
+	if [ ! -f $TARGET ]; then
+		echo "Skipping test for $TARGET as it is not present ..."
+		return $ksft_skip
+	fi
+
+	if [ -d $DIR ]; then
+		echo "Boot param test only possible sysctl_test is built-in, not module:"
+		cat $TEST_DIR/config >&2
+		return $ksft_skip
+	fi
+
+	echo -n "Testing if $TARGET is set to 1 ..."
+	ORIG=$(cat "${TARGET}")
+
+	if [ x$ORIG = "x1" ]; then
+		echo "ok"
+		return 0
+	fi
+	echo "FAIL"
+	echo "Checking if /proc/cmdline contains setting of the expected parameter ..."
+	if [ ! -f /proc/cmdline ]; then
+		echo "/proc/cmdline does not exist, test inconclusive"
+		return 0
+	fi
+
+	FOUND=$(grep -c "sysctl[./]debug[./]test_sysctl[./]boot_int=1" /proc/cmdline)
+	if [ $FOUND = "1" ]; then
+		echo "Kernel param found but $TARGET is not 1, TEST FAILED"
+		rc=1
+		test_rc
+	fi
+
+	echo "Skipping test, expected kernel parameter missing."
+	echo "To perform this test, make sure kernel is booted with parameter: sysctl.debug.test_sysctl.boot_int=1"
+	return $ksft_skip
+}
+
 list_tests()
 {
 	echo "Test ID list:"
@@ -766,6 +807,7 @@ list_tests()
 	echo "0004 x $(get_test_count 0004) - tests proc_douintvec()"
 	echo "0005 x $(get_test_count 0005) - tests proc_douintvec() array"
 	echo "0006 x $(get_test_count 0006) - tests proc_do_large_bitmap()"
+	echo "0007 x $(get_test_count 0007) - tests setting sysctl from kernel boot param"
 }
 
 usage()