[PATCH v2 8/8] selftests/mm: Check that no_mseal_sys_mappings unseals system mappings

[Chris Down]

Booting with no_mseal_sys_mappings currently makes check_sealed skip and
expect_sealed fail, so nothing checks that the parameter actually turns
sealing off.

So let's check /proc/cmdline for it, and when it's there, expect [vdso]
and the other system mappings to be unsealed rather than skipping or
failing. The vdso tests already expect munmap(), mremap() and mprotect()
to succeed when [vdso] isn't sealed, so that covers what the parameter
allows as well.

Suggested-by: Jeff Xu <jeffxu at google.com>
Signed-off-by: Chris Down <chris at chrisdown.name>
---
 tools/testing/selftests/mm/sysmap_is_sealed.c | 25 ++++++++++++++++---
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/mm/sysmap_is_sealed.c b/tools/testing/selftests/mm/sysmap_is_sealed.c
index bfa140e01d8a..158e116ca3b4 100644
--- a/tools/testing/selftests/mm/sysmap_is_sealed.c
+++ b/tools/testing/selftests/mm/sysmap_is_sealed.c
@@ -56,6 +56,21 @@ static bool sysmaps_sealed(void)
 	return vdso && check_vmflag_sealed(vdso);
 }
 
+static bool sysmaps_disabled(void)
+{
+	char cmdline[4096];
+	bool disabled = false;
+	FILE *f;
+
+	f = fopen("/proc/cmdline", "r");
+	if (!f)
+		return false;
+	if (fgets(cmdline, sizeof(cmdline), f))
+		disabled = strstr(cmdline, "no_mseal_sys_mappings");
+	fclose(f);
+	return disabled;
+}
+
 /*
  * Kernels built without CONFIG_MSEAL_SYSTEM_MAPPINGS don't seal system
  * mappings either, so check_sealed skips if they aren't sealed. This fails
@@ -63,7 +78,7 @@ static bool sysmaps_sealed(void)
  */
 TEST(expect_sealed)
 {
-	EXPECT_TRUE(sysmaps_sealed());
+	EXPECT_EQ(!sysmaps_disabled(), sysmaps_sealed());
 }
 
 FIXTURE(basic) {
@@ -127,7 +142,9 @@ FIXTURE_VARIANT_ADD(basic, stack) {
 
 TEST_F(basic, check_sealed)
 {
-	if (!sysmaps_sealed())
+	bool disabled = sysmaps_disabled();
+
+	if (!disabled && !sysmaps_sealed())
 		SKIP(return, "system mappings are not sealed");
 
 	if (!has_mapping(variant->name, self->maps)) {
@@ -135,8 +152,8 @@ TEST_F(basic, check_sealed)
 			variant->name);
 	}
 
-	EXPECT_EQ(variant->sealed,
-		mapping_is_sealed(variant->name, self->maps));
+	EXPECT_EQ(variant->sealed && !disabled,
+		  mapping_is_sealed(variant->name, self->maps));
 };
 
 static void *find_vdso(struct procmap_fd *procmap, size_t *size)
-- 
2.54.0