tools/bpf: add a bpf selftest for stacktrace

Added a bpf selftest in test_progs at tools directory for stacktrace.
The test will populate a hashtable map and a stacktrace map
at the same time with the same key, stackid.
The user space will compare both maps, using BPF_MAP_LOOKUP_ELEM
command and BPF_MAP_GET_NEXT_KEY command, to ensure that both have
the same set of keys.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

3 files changed, 190 insertions, 1 deletions

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 1304753d29ea..a8aa7e251c8e 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -19,7 +19,7 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
 TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test_obj_id.o \
         test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \
         sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o test_tracepoint.o \
-        test_l4lb_noinline.o test_xdp_noinline.o
+        test_l4lb_noinline.o test_xdp_noinline.o test_stacktrace_map.o
 
 TEST_PROGS := test_kmod.sh test_xdp_redirect.sh test_xdp_meta.sh \
         test_offload.py
diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index 09087ab12293..b549308abd19 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -837,6 +837,132 @@ static void test_tp_attach_query(void)
         free(query);
 }
 
+static int compare_map_keys(int map1_fd, int map2_fd)
+{
+        __u32 key, next_key;
+        char val_buf[PERF_MAX_STACK_DEPTH * sizeof(__u64)];
+        int err;
+
+        err = bpf_map_get_next_key(map1_fd, NULL, &key);
+        if (err)
+                return err;
+        err = bpf_map_lookup_elem(map2_fd, &key, val_buf);
+        if (err)
+                return err;
+
+        while (bpf_map_get_next_key(map1_fd, &key, &next_key) == 0) {
+                err = bpf_map_lookup_elem(map2_fd, &next_key, val_buf);
+                if (err)
+                        return err;
+
+                key = next_key;
+        }
+        if (errno != ENOENT)
+                return -1;
+
+        return 0;
+}
+
+static void test_stacktrace_map()
+{
+        int control_map_fd, stackid_hmap_fd, stackmap_fd;
+        const char *file = "./test_stacktrace_map.o";
+        int bytes, efd, err, pmu_fd, prog_fd;
+        struct perf_event_attr attr = {};
+        __u32 key, val, duration = 0;
+        struct bpf_object *obj;
+        char buf[256];
+
+        err = bpf_prog_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj, &prog_fd);
+        if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
+                goto out;
+
+        /* Get the ID for the sched/sched_switch tracepoint */
+        snprintf(buf, sizeof(buf),
+                 "/sys/kernel/debug/tracing/events/sched/sched_switch/id");
+        efd = open(buf, O_RDONLY, 0);
+        if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
+                goto close_prog;
+
+        bytes = read(efd, buf, sizeof(buf));
+        close(efd);
+        if (CHECK(bytes <= 0 || bytes >= sizeof(buf),
+                  "read", "bytes %d errno %d\n", bytes, errno))
+                goto close_prog;
+
+        /* Open the perf event and attach bpf progrram */
+        attr.config = strtol(buf, NULL, 0);
+        attr.type = PERF_TYPE_TRACEPOINT;
+        attr.sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_CALLCHAIN;
+        attr.sample_period = 1;
+        attr.wakeup_events = 1;
+        pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
+                         0 /* cpu 0 */, -1 /* group id */,
+                         0 /* flags */);
+        if (CHECK(pmu_fd < 0, "perf_event_open", "err %d errno %d\n",
+                  pmu_fd, errno))
+                goto close_prog;
+
+        err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
+        if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n",
+                  err, errno))
+                goto close_pmu;
+
+        err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
+        if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n",
+                  err, errno))
+                goto disable_pmu;
+
+        /* find map fds */
+        control_map_fd = bpf_find_map(__func__, obj, "control_map");
+        if (CHECK(control_map_fd < 0, "bpf_find_map control_map",
+                  "err %d errno %d\n", err, errno))
+                goto disable_pmu;
+
+        stackid_hmap_fd = bpf_find_map(__func__, obj, "stackid_hmap");
+        if (CHECK(stackid_hmap_fd < 0, "bpf_find_map stackid_hmap",
+                  "err %d errno %d\n", err, errno))
+                goto disable_pmu;
+
+        stackmap_fd = bpf_find_map(__func__, obj, "stackmap");
+        if (CHECK(stackmap_fd < 0, "bpf_find_map stackmap", "err %d errno %d\n",
+                  err, errno))
+                goto disable_pmu;
+
+        /* give some time for bpf program run */
+        sleep(1);
+
+        /* disable stack trace collection */
+        key = 0;
+        val = 1;
+        bpf_map_update_elem(control_map_fd, &key, &val, 0);
+
+        /* for every element in stackid_hmap, we can find a corresponding one
+         * in stackmap, and vise versa.
+         */
+        err = compare_map_keys(stackid_hmap_fd, stackmap_fd);
+        if (CHECK(err, "compare_map_keys stackid_hmap vs. stackmap",
+                  "err %d errno %d\n", err, errno))
+                goto disable_pmu;
+
+        err = compare_map_keys(stackmap_fd, stackid_hmap_fd);
+        if (CHECK(err, "compare_map_keys stackmap vs. stackid_hmap",
+                  "err %d errno %d\n", err, errno))
+                ; /* fall through */
+
+disable_pmu:
+        ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
+
+close_pmu:
+        close(pmu_fd);
+
+close_prog:
+        bpf_object__close(obj);
+
+out:
+        return;
+}
+
 int main(void)
 {
         struct rlimit rinf = { RLIM_INFINITY, RLIM_INFINITY };
@@ -852,6 +978,7 @@ int main(void)
         test_pkt_md_access();
         test_obj_name();
         test_tp_attach_query();
+        test_stacktrace_map();
 
         printf("Summary: %d PASSED, %d FAILED\n", pass_cnt, error_cnt);
         return error_cnt ? EXIT_FAILURE : EXIT_SUCCESS;
diff --git a/tools/testing/selftests/bpf/test_stacktrace_map.c b/tools/testing/selftests/bpf/test_stacktrace_map.c
new file mode 100644
index 000000000000..76d85c5d08bd
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_stacktrace_map.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+#ifndef PERF_MAX_STACK_DEPTH
+#define PERF_MAX_STACK_DEPTH         127
+#endif
+
+struct bpf_map_def SEC("maps") control_map = {
+        .type = BPF_MAP_TYPE_ARRAY,
+        .key_size = sizeof(__u32),
+        .value_size = sizeof(__u32),
+        .max_entries = 1,
+};
+
+struct bpf_map_def SEC("maps") stackid_hmap = {
+        .type = BPF_MAP_TYPE_HASH,
+        .key_size = sizeof(__u32),
+        .value_size = sizeof(__u32),
+        .max_entries = 10000,
+};
+
+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,
+};
+
+/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
+struct sched_switch_args {
+        unsigned long long pad;
+        char prev_comm[16];
+        int prev_pid;
+        int prev_prio;
+        long long prev_state;
+        char next_comm[16];
+        int next_pid;
+        int next_prio;
+};
+
+SEC("tracepoint/sched/sched_switch")
+int oncpu(struct sched_switch_args *ctx)
+{
+        __u32 key = 0, val = 0, *value_p;
+
+        value_p = bpf_map_lookup_elem(&control_map, &key);
+        if (value_p && *value_p)
+                return 0; /* skip if non-zero *value_p */
+
+        /* The size of stackmap and stackid_hmap should be the same */
+        key = bpf_get_stackid(ctx, &stackmap, 0);
+        if ((int)key >= 0)
+                bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
+
+        return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+__u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */