[PATCH bpf-next v2 3/3] bpf: selftests: Skip kmem test when cgroup.memory=nokmem is set

[Hui Zhu <hui.zhu@linux.dev>]

From: Hui Zhu <zhuhui@kylinos.cn>

When cgroup.memory=nokmem is set in the kernel command line, kmem
accounting is disabled. This causes the test_kmem subtest in
cgroup_iter_memcg to fail because it expects non-zero kmem values.

Fix this by checking /proc/cmdline for the nokmem parameter. If
found, verify that kmem value is zero and return early, skipping
the pipe creation test that would otherwise fail.

Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
---
 .../bpf/prog_tests/cgroup_iter_memcg.c        | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c b/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c
index 897b17b58df3..2b9c148cebf0 100644
--- a/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c
+++ b/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c
@@ -134,11 +134,41 @@ static void test_shmem(struct bpf_link *link, struct memcg_query *memcg_query)
 	shm_unlink("/tmp_shmem");
 }
 
+static bool cmdline_has(const char *arg)
+{
+	char cmdline[4096];
+	int fd;
+	ssize_t len;
+	bool ret = false;
+
+	fd = open("/proc/cmdline", O_RDONLY);
+	if (fd < 0)
+		return false;
+
+	len = read(fd, cmdline, sizeof(cmdline) - 1);
+	close(fd);
+	if (len < 0)
+		return false;
+
+	cmdline[len] = '\0';
+	if (strstr(cmdline, arg))
+		ret = true;
+
+	return ret;
+}
+
 #define NR_PIPES 64
 static void test_kmem(struct bpf_link *link, struct memcg_query *memcg_query)
 {
 	int fds[NR_PIPES][2], i;
 
+	if (cmdline_has("cgroup.memory=nokmem")) {
+		if (!ASSERT_OK(read_stats(link), "read stats"))
+			return;
+		ASSERT_EQ(memcg_query->memcg_kmem, 0, "kmem value");
+		return;
+	}
+
 	/*
 	 * Increase kmem value by creating pipes which will allocate some
 	 * kernel buffers.
-- 
2.43.0