selftests/bpf: Add uprobe_multi pid filter tests

Running api and link tests also with pid filter and checking
the probe gets executed only for specific pid.

Spawning extra process to trigger attached uprobes and checking
we get correct counts from executed programs.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-28-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: olsajiri

tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c

@@ -25,14 +25,87 @@ noinline void uprobe_multi_func_3(void)
 	asm volatile ("");
 }
 
-static void uprobe_multi_test_run(struct uprobe_multi *skel)
+struct child {
+	int go[2];
+	int pid;
+};
+
+static void release_child(struct child *child)
+{
+	int child_status;
+
+	if (!child)
+		return;
+	close(child->go[1]);
+	close(child->go[0]);
+	if (child->pid > 0)
+		waitpid(child->pid, &child_status, 0);
+}
+
+static void kick_child(struct child *child)
+{
+	char c = 1;
+
+	if (child) {
+		write(child->go[1], &c, 1);
+		release_child(child);
+	}
+	fflush(NULL);
+}
+
+static struct child *spawn_child(void)
+{
+	static struct child child;
+	int err;
+	int c;
+
+	/* pipe to notify child to execute the trigger functions */
+	if (pipe(child.go))
+		return NULL;
+
+	child.pid = fork();
+	if (child.pid < 0) {
+		release_child(&child);
+		errno = EINVAL;
+		return NULL;
+	}
+
+	/* child */
+	if (child.pid == 0) {
+		close(child.go[1]);
+
+		/* wait for parent's kick */
+		err = read(child.go[0], &c, 1);
+		if (err != 1)
+			exit(err);
+
+		uprobe_multi_func_1();
+		uprobe_multi_func_2();
+		uprobe_multi_func_3();
+
+		exit(errno);
+	}
+
+	return &child;
+}
+
+static void uprobe_multi_test_run(struct uprobe_multi *skel, struct child *child)
 {
 	skel->bss->uprobe_multi_func_1_addr = (__u64) uprobe_multi_func_1;
 	skel->bss->uprobe_multi_func_2_addr = (__u64) uprobe_multi_func_2;
 	skel->bss->uprobe_multi_func_3_addr = (__u64) uprobe_multi_func_3;
 
 	skel->bss->user_ptr = test_data;
-	skel->bss->pid = getpid();
+
+	/*
+	 * Disable pid check in bpf program if we are pid filter test,
+	 * because the probe should be executed only by child->pid
+	 * passed at the probe attach.
+	 */
+	skel->bss->pid = child ? 0 : getpid();
+
+	if (child)
+		kick_child(child);
 
 	/* trigger all probes */
 	uprobe_multi_func_1();
@@ -52,6 +125,9 @@ static void uprobe_multi_test_run(struct uprobe_multi *skel)
 	ASSERT_EQ(skel->bss->uretprobe_multi_func_3_result, 2, "uretprobe_multi_func_3_result");
 
 	ASSERT_EQ(skel->bss->uprobe_multi_sleep_result, 6, "uprobe_multi_sleep_result");
+
+	if (child)
+		ASSERT_EQ(skel->bss->child_pid, child->pid, "uprobe_multi_child_pid");
 }
 
 static void test_skel_api(void)
@@ -67,51 +143,69 @@ static void test_skel_api(void)
 	if (!ASSERT_OK(err, "uprobe_multi__attach"))
 		goto cleanup;
 
-	uprobe_multi_test_run(skel);
+	uprobe_multi_test_run(skel, NULL);
 
 cleanup:
 	uprobe_multi__destroy(skel);
 }
 
 static void
-test_attach_api(const char *binary, const char *pattern, struct bpf_uprobe_multi_opts *opts)
+__test_attach_api(const char *binary, const char *pattern, struct bpf_uprobe_multi_opts *opts,
+		  struct child *child)
 {
+	pid_t pid = child ? child->pid : -1;
 	struct uprobe_multi *skel = NULL;
 
 	skel = uprobe_multi__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "uprobe_multi__open_and_load"))
 		goto cleanup;
 
 	opts->retprobe = false;
-	skel->links.uprobe = bpf_program__attach_uprobe_multi(skel->progs.uprobe, -1,
+	skel->links.uprobe = bpf_program__attach_uprobe_multi(skel->progs.uprobe, pid,
 							      binary, pattern, opts);
 	if (!ASSERT_OK_PTR(skel->links.uprobe, "bpf_program__attach_uprobe_multi"))
 		goto cleanup;
 
 	opts->retprobe = true;
-	skel->links.uretprobe = bpf_program__attach_uprobe_multi(skel->progs.uretprobe, -1,
+	skel->links.uretprobe = bpf_program__attach_uprobe_multi(skel->progs.uretprobe, pid,
 								 binary, pattern, opts);
 	if (!ASSERT_OK_PTR(skel->links.uretprobe, "bpf_program__attach_uprobe_multi"))
 		goto cleanup;
 
 	opts->retprobe = false;
-	skel->links.uprobe_sleep = bpf_program__attach_uprobe_multi(skel->progs.uprobe_sleep, -1,
+	skel->links.uprobe_sleep = bpf_program__attach_uprobe_multi(skel->progs.uprobe_sleep, pid,
 								    binary, pattern, opts);
 	if (!ASSERT_OK_PTR(skel->links.uprobe_sleep, "bpf_program__attach_uprobe_multi"))
 		goto cleanup;
 
 	opts->retprobe = true;
 	skel->links.uretprobe_sleep = bpf_program__attach_uprobe_multi(skel->progs.uretprobe_sleep,
-								       -1, binary, pattern, opts);
+								       pid, binary, pattern, opts);
 	if (!ASSERT_OK_PTR(skel->links.uretprobe_sleep, "bpf_program__attach_uprobe_multi"))
 		goto cleanup;
 
-	uprobe_multi_test_run(skel);
+	uprobe_multi_test_run(skel, child);
 
 cleanup:
 	uprobe_multi__destroy(skel);
 }
 
+static void
+test_attach_api(const char *binary, const char *pattern, struct bpf_uprobe_multi_opts *opts)
+{
+	struct child *child;
+
+	/* no pid filter */
+	__test_attach_api(binary, pattern, opts, NULL);
+
+	/* pid filter */
+	child = spawn_child();
+	if (!ASSERT_OK_PTR(child, "spawn_child"))
+		return;
+
+	__test_attach_api(binary, pattern, opts, child);
+}
+
 static void test_attach_api_pattern(void)
 {
 	LIBBPF_OPTS(bpf_uprobe_multi_opts, opts);
@@ -134,7 +228,7 @@ static void test_attach_api_syms(void)
 	test_attach_api("/proc/self/exe", NULL, &opts);
 }
 
-static void test_link_api(void)
+static void __test_link_api(struct child *child)
 {
 	int prog_fd, link1_fd = -1, link2_fd = -1, link3_fd = -1, link4_fd = -1;
 	LIBBPF_OPTS(bpf_link_create_opts, opts);
@@ -155,6 +249,7 @@ static void test_link_api(void)
 	opts.uprobe_multi.path = path;
 	opts.uprobe_multi.offsets = offsets;
 	opts.uprobe_multi.cnt = ARRAY_SIZE(syms);
+	opts.uprobe_multi.pid = child ? child->pid : 0;
 
 	skel = uprobe_multi__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "uprobe_multi__open_and_load"))
@@ -184,7 +279,7 @@ static void test_link_api(void)
 	if (!ASSERT_GE(link4_fd, 0, "link4_fd"))
 		goto cleanup;
 
-	uprobe_multi_test_run(skel);
+	uprobe_multi_test_run(skel, child);
 
 cleanup:
 	if (link1_fd >= 0)
@@ -200,6 +295,21 @@ static void test_link_api(void)
 	free(offsets);
 }
 
+void test_link_api(void)
+{
+	struct child *child;
+
+	/* no pid filter */
+	__test_link_api(NULL);
+
+	/* pid filter */
+	child = spawn_child();
+	if (!ASSERT_OK_PTR(child, "spawn_child"))
+		return;
+
+	__test_link_api(child);
+}
+
 static void test_bench_attach_uprobe(void)
 {
 	long attach_start_ns = 0, attach_end_ns = 0;

tools/testing/selftests/bpf/progs/uprobe_multi.c

@@ -21,6 +21,8 @@ __u64 uretprobe_multi_func_3_result = 0;
 __u64 uprobe_multi_sleep_result = 0;
 
 int pid = 0;
+int child_pid = 0;
+
 bool test_cookie = false;
 void *user_ptr = 0;
 
@@ -34,7 +36,9 @@ static __always_inline bool verify_sleepable_user_copy(void)
 
 static void uprobe_multi_check(void *ctx, bool is_return, bool is_sleep)
 {
-	if (bpf_get_current_pid_tgid() >> 32 != pid)
+	child_pid = bpf_get_current_pid_tgid() >> 32;
+
+	if (pid && child_pid != pid)
 		return;
 
 	__u64 cookie = test_cookie ? bpf_get_attach_cookie(ctx) : 0;