selftests/landlock: Replace hard-coded 16 with a constant

The next commit will reuse this number.  Make it a shared constant to
future-proof changes.

Signed-off-by: Tingmao Wang <m@maowtm.org>
Link: https://patch.msgid.link/eff35caa9b4ac51aa83a88d67c4dd67f4f8b3a4a.1781228815.git.m@maowtm.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>

tools/testing/selftests/landlock/audit_test.c

@@ -76,7 +76,7 @@ TEST_F(audit, layers)
 		.scoped = LANDLOCK_SCOPE_SIGNAL,
 	};
 	int status, ruleset_fd, i;
-	__u64(*domain_stack)[16];
+	__u64(*domain_stack)[LANDLOCK_MAX_NUM_LAYERS];
 	__u64 prev_dom = 3;
 	pid_t child;
 

tools/testing/selftests/landlock/common.h

@@ -25,6 +25,8 @@
 /* TEST_F_FORK() should not be used for new tests. */
 #define TEST_F_FORK(fixture_name, test_name) TEST_F(fixture_name, test_name)
 
+#define LANDLOCK_MAX_NUM_LAYERS 16
+
 static const char bin_sandbox_and_launch[] = "./sandbox-and-launch";
 static const char bin_wait_pipe[] = "./wait-pipe";
 static const char bin_wait_pipe_sandbox[] = "./wait-pipe-sandbox";

tools/testing/selftests/landlock/fs_test.c

@@ -1441,7 +1441,7 @@ TEST_F_FORK(layout0, max_layers)
 	};
 	const int ruleset_fd = create_ruleset(_metadata, ACCESS_RW, rules);
 
-	for (i = 0; i < 16; i++)
+	for (i = 0; i < LANDLOCK_MAX_NUM_LAYERS; i++)
 		enforce_ruleset(_metadata, ruleset_fd);
 
 	for (i = 0; i < 2; i++) {