linux-kernel - [PATCH 2/2] selftests/mm: Add mseal test for no-discard madvise

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Message-ID: <20240807173336.2523757-3-pedro.falcato@gmail.com>
Date: Wed,  7 Aug 2024 18:33:36 +0100
From: Pedro Falcato <pedro.falcato@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Shuah Khan <shuah@...nel.org>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Jeff Xu <jeffxu@...omium.org>,
	Kees Cook <kees@...nel.org>,
	linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	Pedro Falcato <pedro.falcato@...il.com>
Subject: [PATCH 2/2] selftests/mm: Add mseal test for no-discard madvise

Add an mseal test for madvise() operations that aren't considered
"discard" (e.g purely advisory ops such as MADV_RANDOM).

Signed-off-by: Pedro Falcato <pedro.falcato@...il.com>
---
 tools/testing/selftests/mm/mseal_test.c | 34 +++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/tools/testing/selftests/mm/mseal_test.c b/tools/testing/selftests/mm/mseal_test.c
index a818f010de4..2dcda7440eb 100644
--- a/tools/testing/selftests/mm/mseal_test.c
+++ b/tools/testing/selftests/mm/mseal_test.c
@@ -1731,6 +1731,38 @@ static void test_seal_discard_ro_anon(bool seal)
 	REPORT_TEST_PASS();
 }
 
+static void test_seal_madvise_nodiscard(bool seal)
+{
+	void *ptr;
+	unsigned long page_size = getpagesize();
+	unsigned long size = 4 * page_size;
+	int ret;
+
+	setup_single_address(size, &ptr);
+	FAIL_TEST_IF_FALSE(ptr != (void *)-1);
+
+	if (seal) {
+		ret = seal_single_address(ptr, size);
+		FAIL_TEST_IF_FALSE(!ret);
+	}
+
+	/*
+	 * Test a random madvise flag like MADV_RANDOM that does not touch page
+	 * contents (and thus should work for msealed VMAs). RANDOM also happens to
+	 * share bits with other discard-ish flags like REMOVE.
+	 */
+	ret = sys_madvise(ptr, size, MADV_RANDOM);
+	FAIL_TEST_IF_FALSE(!ret);
+
+	ret = sys_munmap(ptr, size);
+	if (seal)
+		FAIL_TEST_IF_FALSE(ret < 0);
+	else
+		FAIL_TEST_IF_FALSE(!ret);
+
+	REPORT_TEST_PASS();
+}
+
 int main(int argc, char **argv)
 {
 	bool test_seal = seal_support();
@@ -1822,6 +1854,8 @@ int main(int argc, char **argv)
 	test_seal_mremap_move_fixed_zero(true);
 	test_seal_mremap_move_dontunmap_anyaddr(false);
 	test_seal_mremap_move_dontunmap_anyaddr(true);
+	test_seal_madvise_nodiscard(false);
+	test_seal_madvise_nodiscard(true);
 	test_seal_discard_ro_anon(false);
 	test_seal_discard_ro_anon(true);
 	test_seal_discard_ro_anon_on_rw(false);
-- 
2.46.0