linux-kernel - [PATCH v2 7/8] selftest/mm: ksm_functional_tests: test in mmap_and_merge

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230801124844.278698-8-david@redhat.com>
Date:   Tue,  1 Aug 2023 14:48:43 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        liubo <liubo254@...wei.com>, Peter Xu <peterx@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Hugh Dickins <hughd@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>,
        Mel Gorman <mgorman@...e.de>, Shuah Khan <shuah@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH v2 7/8] selftest/mm: ksm_functional_tests: test in mmap_and_merge_range() if anything got merged

Let's extend mmap_and_merge_range() to test if anything in the current
process was merged. range_maps_duplicates() is too unreliable for that
use case, so instead look at KSM stats.

Trigger a complete unmerge first, to cleanup the stable tree and
stabilize accounting of merged pages.

Note that we're using /proc/self/ksm_merging_pages instead of
/proc/self/ksm_stat, because that one is available in more existing
kernels.

If /proc/self/ksm_merging_pages can't be opened, we can't perform any
checks and simply skip them.

We have to special-case the shared zeropage for now. But the only user
-- test_unmerge_zero_pages() -- performs its own merge checks.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 .../selftests/mm/ksm_functional_tests.c       | 47 +++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
index 0de9d33cd565..cb63b600cb4f 100644
--- a/tools/testing/selftests/mm/ksm_functional_tests.c
+++ b/tools/testing/selftests/mm/ksm_functional_tests.c
@@ -30,6 +30,7 @@
 static int ksm_fd;
 static int ksm_full_scans_fd;
 static int proc_self_ksm_stat_fd;
+static int proc_self_ksm_merging_pages_fd;
 static int ksm_use_zero_pages_fd;
 static int pagemap_fd;
 static size_t pagesize;
@@ -88,6 +89,22 @@ static long get_my_ksm_zero_pages(void)
 	return my_ksm_zero_pages;
 }
 
+static long get_my_merging_pages(void)
+{
+	char buf[10];
+	ssize_t ret;
+
+	if (proc_self_ksm_merging_pages_fd < 0)
+		return proc_self_ksm_merging_pages_fd;
+
+	ret = pread(proc_self_ksm_merging_pages_fd, buf, sizeof(buf) - 1, 0);
+	if (ret <= 0)
+		return -errno;
+	buf[ret] = 0;
+
+	return strtol(buf, NULL, 10);
+}
+
 static long ksm_get_full_scans(void)
 {
 	char buf[10];
@@ -120,11 +137,29 @@ static int ksm_merge(void)
 	return 0;
 }
 
+static int ksm_unmerge(void)
+{
+	if (write(ksm_fd, "2", 1) != 1)
+		return -errno;
+	return 0;
+}
+
 static char *mmap_and_merge_range(char val, unsigned long size, bool use_prctl)
 {
 	char *map;
 	int ret;
 
+	/* Stabilize accounting by disabling KSM completely. */
+	if (ksm_unmerge()) {
+		ksft_test_result_fail("Disabling (unmerging) KSM failed\n");
+		goto unmap;
+	}
+
+	if (get_my_merging_pages() > 0) {
+		ksft_test_result_fail("Still pages merged\n");
+		goto unmap;
+	}
+
 	map = mmap(NULL, size, PROT_READ|PROT_WRITE,
 		   MAP_PRIVATE|MAP_ANON, -1, 0);
 	if (map == MAP_FAILED) {
@@ -160,6 +195,16 @@ static char *mmap_and_merge_range(char val, unsigned long size, bool use_prctl)
 		ksft_test_result_fail("Running KSM failed\n");
 		goto unmap;
 	}
+
+	/*
+	 * Check if anything was merged at all. Ignore the zero page that is
+	 * accounted differently (depending on kernel support).
+	 */
+	if (val && !get_my_merging_pages()) {
+		ksft_test_result_fail("No pages got merged\n");
+		goto unmap;
+	}
+
 	return map;
 unmap:
 	munmap(map, size);
@@ -473,6 +518,8 @@ int main(int argc, char **argv)
 	if (pagemap_fd < 0)
 		ksft_exit_skip("open(\"/proc/self/pagemap\") failed\n");
 	proc_self_ksm_stat_fd = open("/proc/self/ksm_stat", O_RDONLY);
+	proc_self_ksm_merging_pages_fd = open("/proc/self/ksm_merging_pages",
+					      O_RDONLY);
 	ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR);
 
 	test_unmerge();
-- 
2.41.0