tools/bpf: add a test for bpf_get_stack with tracepoint prog

The test_stacktrace_map and test_stacktrace_build_id are
enhanced to call bpf_get_stack in the helper to get the
stack trace as well.  The stack traces from bpf_get_stack
and bpf_get_stackid are compared to ensure that for the
same stack as represented as the same hash, their ip addresses
or build id's must be the same.

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/test_progs.c

@@ -906,11 +906,47 @@ static int compare_map_keys(int map1_fd, int map2_fd)
 	return 0;
 }
 
+static int compare_stack_ips(int smap_fd, int amap_fd, int stack_trace_len)
+{
+	__u32 key, next_key, *cur_key_p, *next_key_p;
+	char *val_buf1, *val_buf2;
+	int i, err = 0;
+
+	val_buf1 = malloc(stack_trace_len);
+	val_buf2 = malloc(stack_trace_len);
+	cur_key_p = NULL;
+	next_key_p = &key;
+	while (bpf_map_get_next_key(smap_fd, cur_key_p, next_key_p) == 0) {
+		err = bpf_map_lookup_elem(smap_fd, next_key_p, val_buf1);
+		if (err)
+			goto out;
+		err = bpf_map_lookup_elem(amap_fd, next_key_p, val_buf2);
+		if (err)
+			goto out;
+		for (i = 0; i < stack_trace_len; i++) {
+			if (val_buf1[i] != val_buf2[i]) {
+				err = -1;
+				goto out;
+			}
+		}
+		key = *next_key_p;
+		cur_key_p = &key;
+		next_key_p = &next_key;
+	}
+	if (errno != ENOENT)
+		err = -1;
+
+out:
+	free(val_buf1);
+	free(val_buf2);
+	return err;
+}
+
 static void test_stacktrace_map()
 {
-	int control_map_fd, stackid_hmap_fd, stackmap_fd;
+	int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
 	const char *file = "./test_stacktrace_map.o";
-	int bytes, efd, err, pmu_fd, prog_fd;
+	int bytes, efd, err, pmu_fd, prog_fd, stack_trace_len;
 	struct perf_event_attr attr = {};
 	__u32 key, val, duration = 0;
 	struct bpf_object *obj;
@@ -966,6 +1002,10 @@ static void test_stacktrace_map()
 	if (stackmap_fd < 0)
 		goto disable_pmu;
 
+	stack_amap_fd = bpf_find_map(__func__, obj, "stack_amap");
+	if (stack_amap_fd < 0)
+		goto disable_pmu;
+
 	/* give some time for bpf program run */
 	sleep(1);
 
@@ -987,6 +1027,12 @@ static void test_stacktrace_map()
 		  "err %d errno %d\n", err, errno))
 		goto disable_pmu_noerr;
 
+	stack_trace_len = PERF_MAX_STACK_DEPTH * sizeof(__u64);
+	err = compare_stack_ips(stackmap_fd, stack_amap_fd, stack_trace_len);
+	if (CHECK(err, "compare_stack_ips stackmap vs. stack_amap",
+		  "err %d errno %d\n", err, errno))
+		goto disable_pmu_noerr;
+
 	goto disable_pmu_noerr;
 disable_pmu:
 	error_cnt++;
@@ -1080,9 +1126,9 @@ err:
 
 static void test_stacktrace_build_id(void)
 {
-	int control_map_fd, stackid_hmap_fd, stackmap_fd;
+	int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
 	const char *file = "./test_stacktrace_build_id.o";
-	int bytes, efd, err, pmu_fd, prog_fd;
+	int bytes, efd, err, pmu_fd, prog_fd, stack_trace_len;
 	struct perf_event_attr attr = {};
 	__u32 key, previous_key, val, duration = 0;
 	struct bpf_object *obj;
@@ -1147,6 +1193,11 @@ static void test_stacktrace_build_id(void)
 		  err, errno))
 		goto disable_pmu;
 
+	stack_amap_fd = bpf_find_map(__func__, obj, "stack_amap");
+	if (CHECK(stack_amap_fd < 0, "bpf_find_map stack_amap",
+		  "err %d errno %d\n", err, errno))
+		goto disable_pmu;
+
 	assert(system("dd if=/dev/urandom of=/dev/zero count=4 2> /dev/null")
 	       == 0);
 	assert(system("./urandom_read if=/dev/urandom of=/dev/zero count=4 2> /dev/null") == 0);
@@ -1198,8 +1249,15 @@ static void test_stacktrace_build_id(void)
 		previous_key = key;
 	} while (bpf_map_get_next_key(stackmap_fd, &previous_key, &key) == 0);
 
-	CHECK(build_id_matches < 1, "build id match",
-	      "Didn't find expected build ID from the map");
+	if (CHECK(build_id_matches < 1, "build id match",
+		  "Didn't find expected build ID from the map"))
+		goto disable_pmu;
+
+	stack_trace_len = PERF_MAX_STACK_DEPTH
+		* sizeof(struct bpf_stack_build_id);
+	err = compare_stack_ips(stackmap_fd, stack_amap_fd, stack_trace_len);
+	CHECK(err, "compare_stack_ips stackmap vs. stack_amap",
+	      "err %d errno %d\n", err, errno);
 
 disable_pmu:
 	ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);

tools/testing/selftests/bpf/test_stacktrace_build_id.c

@@ -19,7 +19,7 @@ struct bpf_map_def SEC("maps") stackid_hmap = {
 	.type = BPF_MAP_TYPE_HASH,
 	.key_size = sizeof(__u32),
 	.value_size = sizeof(__u32),
-	.max_entries = 10000,
+	.max_entries = 16384,
 };
 
 struct bpf_map_def SEC("maps") stackmap = {
@@ -31,6 +31,14 @@ struct bpf_map_def SEC("maps") stackmap = {
 	.map_flags = BPF_F_STACK_BUILD_ID,
 };
 
+struct bpf_map_def SEC("maps") stack_amap = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(struct bpf_stack_build_id)
+		* PERF_MAX_STACK_DEPTH,
+	.max_entries = 128,
+};
+
 /* taken from /sys/kernel/debug/tracing/events/random/urandom_read/format */
 struct random_urandom_args {
 	unsigned long long pad;
@@ -42,7 +50,10 @@ struct random_urandom_args {
 SEC("tracepoint/random/urandom_read")
 int oncpu(struct random_urandom_args *args)
 {
+	__u32 max_len = sizeof(struct bpf_stack_build_id)
+			* PERF_MAX_STACK_DEPTH;
 	__u32 key = 0, val = 0, *value_p;
+	void *stack_p;
 
 	value_p = bpf_map_lookup_elem(&control_map, &key);
 	if (value_p && *value_p)
@@ -50,8 +61,13 @@ int oncpu(struct random_urandom_args *args)
 
 	/* The size of stackmap and stackid_hmap should be the same */
 	key = bpf_get_stackid(args, &stackmap, BPF_F_USER_STACK);
-	if ((int)key >= 0)
+	if ((int)key >= 0) {
 		bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
+		stack_p = bpf_map_lookup_elem(&stack_amap, &key);
+		if (stack_p)
+			bpf_get_stack(args, stack_p, max_len,
+				      BPF_F_USER_STACK | BPF_F_USER_BUILD_ID);
+	}
 
 	return 0;
 }

tools/testing/selftests/bpf/test_stacktrace_map.c

@@ -19,14 +19,21 @@ struct bpf_map_def SEC("maps") stackid_hmap = {
 	.type = BPF_MAP_TYPE_HASH,
 	.key_size = sizeof(__u32),
 	.value_size = sizeof(__u32),
-	.max_entries = 10000,
+	.max_entries = 16384,
 };
 
 struct bpf_map_def SEC("maps") stackmap = {
 	.type = BPF_MAP_TYPE_STACK_TRACE,
 	.key_size = sizeof(__u32),
 	.value_size = sizeof(__u64) * PERF_MAX_STACK_DEPTH,
-	.max_entries = 10000,
+	.max_entries = 16384,
+};
+
+struct bpf_map_def SEC("maps") stack_amap = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(__u64) * PERF_MAX_STACK_DEPTH,
+	.max_entries = 16384,
 };
 
 /* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
@@ -44,7 +51,9 @@ struct sched_switch_args {
 SEC("tracepoint/sched/sched_switch")
 int oncpu(struct sched_switch_args *ctx)
 {
+	__u32 max_len = PERF_MAX_STACK_DEPTH * sizeof(__u64);
 	__u32 key = 0, val = 0, *value_p;
+	void *stack_p;
 
 	value_p = bpf_map_lookup_elem(&control_map, &key);
 	if (value_p && *value_p)
@@ -52,8 +61,12 @@ int oncpu(struct sched_switch_args *ctx)
 
 	/* The size of stackmap and stackid_hmap should be the same */
 	key = bpf_get_stackid(ctx, &stackmap, 0);
-	if ((int)key >= 0)
+	if ((int)key >= 0) {
 		bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
+		stack_p = bpf_map_lookup_elem(&stack_amap, &key);
+		if (stack_p)
+			bpf_get_stack(ctx, stack_p, max_len, 0);
+	}
 
 	return 0;
 }