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Subject[PATCH v6 bpf-next 2/2] selftests/bpf: add bpf_read_branch_records() selftest
Date
Add a selftest to test:

* default bpf_read_branch_records() behavior
* BPF_F_GET_BRANCH_RECORDS_SIZE flag behavior
* error path on non branch record perf events
* using helper to write to stack
* using helper to write to map

On host with hardware counter support:

# ./test_progs -t perf_branches
#27/1 perf_branches_hw:OK
#27/2 perf_branches_no_hw:OK
#27 perf_branches:OK
Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED

On host without hardware counter support (VM):

# ./test_progs -t perf_branches
#27/1 perf_branches_hw:OK
#27/2 perf_branches_no_hw:OK
#27 perf_branches:OK
Summary: 1/2 PASSED, 1 SKIPPED, 0 FAILED

Also sync tools/include/uapi/linux/bpf.h.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
tools/include/uapi/linux/bpf.h | 25 ++-
.../selftests/bpf/prog_tests/perf_branches.c | 182 ++++++++++++++++++
.../selftests/bpf/progs/test_perf_branches.c | 74 +++++++
3 files changed, 280 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_branches.c
create mode 100644 tools/testing/selftests/bpf/progs/test_perf_branches.c

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index f1d74a2bd234..332aa433d045 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2892,6 +2892,25 @@ union bpf_attr {
* Obtain the 64bit jiffies
* Return
* The 64 bit jiffies
+ *
+ * int bpf_read_branch_records(struct bpf_perf_event_data *ctx, void *buf, u32 buf_size, u64 flags)
+ * Description
+ * For an eBPF program attached to a perf event, retrieve the
+ * branch records (struct perf_branch_entry) associated to *ctx*
+ * and store it in the buffer pointed by *buf* up to size
+ * *buf_size* bytes.
+ *
+ * The *flags* can be set to **BPF_F_GET_BRANCH_RECORDS_SIZE** to
+ * instead return the number of bytes required to store all the
+ * branch entries. If this flag is set, *buf* may be NULL.
+ * Return
+ * On success, number of bytes written to *buf*. On error, a
+ * negative value.
+ *
+ * **-EINVAL** if arguments invalid or **buf_size** not a multiple
+ * of sizeof(struct perf_branch_entry).
+ *
+ * **-ENOENT** if architecture does not support branch records.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3012,7 +3031,8 @@ union bpf_attr {
FN(probe_read_kernel_str), \
FN(tcp_send_ack), \
FN(send_signal_thread), \
- FN(jiffies64),
+ FN(jiffies64), \
+ FN(read_branch_records),

/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
@@ -3091,6 +3111,9 @@ enum bpf_func_id {
/* BPF_FUNC_sk_storage_get flags */
#define BPF_SK_STORAGE_GET_F_CREATE (1ULL << 0)

+/* BPF_FUNC_read_branch_records flags. */
+#define BPF_F_GET_BRANCH_RECORDS_SIZE (1ULL << 0)
+
/* Mode for BPF_FUNC_skb_adjust_room helper. */
enum bpf_adj_room_mode {
BPF_ADJ_ROOM_NET,
diff --git a/tools/testing/selftests/bpf/prog_tests/perf_branches.c b/tools/testing/selftests/bpf/prog_tests/perf_branches.c
new file mode 100644
index 000000000000..bceefaea85b9
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/perf_branches.c
@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <pthread.h>
+#include <sched.h>
+#include <sys/socket.h>
+#include <test_progs.h>
+#include "bpf/libbpf_internal.h"
+#include "test_perf_branches.skel.h"
+
+struct output {
+ int required_size;
+ int written_stack;
+ int written_map;
+};
+
+static void on_good_sample(void *ctx, int cpu, void *data, __u32 size)
+{
+ int required_size = ((struct output *)data)->required_size;
+ int written_stack = ((struct output *)data)->written_stack;
+ int written_map = ((struct output *)data)->written_map;
+ int pbe_size = sizeof(struct perf_branch_entry);
+ int duration = 0;
+
+ /*
+ * It's hard to validate the contents of the branch entries b/c it
+ * would require some kind of disassembler and also encoding the
+ * valid jump instructions for supported architectures. So just check
+ * the easy stuff for now.
+ */
+ CHECK(required_size <= 0, "read_branches_size", "err %d\n", required_size);
+ CHECK(written_stack < 0, "read_branches_stack", "err %d\n", written_stack);
+ CHECK(written_stack % pbe_size != 0, "read_branches_stack",
+ "stack bytes written=%d not multiple of struct size=%d\n",
+ written_stack, pbe_size);
+ CHECK(written_map < 0, "read_branches_map", "err %d\n", written_map);
+ CHECK(written_map % pbe_size != 0, "read_branches_map",
+ "map bytes written=%d not multiple of struct size=%d\n",
+ written_map, pbe_size);
+ CHECK(written_map < written_stack, "read_branches_size",
+ "written_map=%d < written_stack=%d\n", written_map, written_stack);
+
+ *(int *)ctx = 1;
+}
+
+static void on_bad_sample(void *ctx, int cpu, void *data, __u32 size)
+{
+ int required_size = ((struct output *)data)->required_size;
+ int written_stack = ((struct output *)data)->written_stack;
+ int written_map = ((struct output *)data)->written_map;
+ int duration = 0;
+
+ CHECK((required_size != -EINVAL && required_size != -ENOENT),
+ "read_branches_size", "err %d\n", required_size);
+ CHECK((written_stack != -EINVAL && written_stack != -ENOENT),
+ "read_branches_stack", "written %d\n", written_stack);
+ CHECK((written_map != -EINVAL && written_map != -ENOENT),
+ "read_branches_map", "written %d\n", written_map);
+
+ *(int *)ctx = 1;
+}
+
+static void test_perf_branches_common(int perf_fd, void *sample_cb)
+{
+ struct perf_buffer_opts pb_opts = {};
+ int err, i, duration = 0, ok = 0;
+ struct test_perf_branches *skel;
+ struct perf_buffer *pb;
+ struct bpf_link *link;
+ volatile int j = 0;
+ cpu_set_t cpu_set;
+
+ skel = test_perf_branches__open_and_load();
+ if (CHECK(!skel, "test_perf_branches_load",
+ "perf_branches skeleton failed\n"))
+ goto out_destroy;
+
+ /* attach perf_event */
+ link = bpf_program__attach_perf_event(skel->progs.perf_branches, perf_fd);
+ if (CHECK(IS_ERR(link), "attach_perf_event", "err %ld\n", PTR_ERR(link)))
+ goto out_destroy;
+
+ /* set up perf buffer */
+ pb_opts.sample_cb = sample_cb;
+ pb_opts.ctx = &ok;
+ pb = perf_buffer__new(bpf_map__fd(skel->maps.perf_buf_map), 1, &pb_opts);
+ if (CHECK(IS_ERR(pb), "perf_buf__new", "err %ld\n", PTR_ERR(pb)))
+ goto out_detach;
+
+ /* generate some branches on cpu 0 */
+ CPU_ZERO(&cpu_set);
+ CPU_SET(0, &cpu_set);
+ err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set), &cpu_set);
+ if (CHECK(err, "set_affinity", "cpu #0, err %d\n", err))
+ goto out_free_pb;
+ /* spin the loop for a while (random high number) */
+ for (i = 0; i < 1000000; ++i)
+ ++j;
+
+ /* read perf buffer */
+ err = perf_buffer__poll(pb, 500);
+ if (CHECK(err < 0, "perf_buffer__poll", "err %d\n", err))
+ goto out_free_pb;
+
+ if (CHECK(!ok, "ok", "not ok\n"))
+ goto out_free_pb;
+
+out_free_pb:
+ perf_buffer__free(pb);
+out_detach:
+ bpf_link__destroy(link);
+out_destroy:
+ test_perf_branches__destroy(skel);
+}
+
+static void test_perf_branches_hw(void)
+{
+ struct perf_event_attr attr = {0};
+ int duration = 0;
+ int pfd;
+
+ /* create perf event */
+ attr.size = sizeof(attr);
+ attr.type = PERF_TYPE_HARDWARE;
+ attr.config = PERF_COUNT_HW_CPU_CYCLES;
+ attr.freq = 1;
+ attr.sample_freq = 4000;
+ attr.sample_type = PERF_SAMPLE_BRANCH_STACK;
+ attr.branch_sample_type = PERF_SAMPLE_BRANCH_USER | PERF_SAMPLE_BRANCH_ANY;
+ pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
+
+ /*
+ * Some setups don't support branch records (virtual machines, !x86),
+ * so skip test in this case.
+ */
+ if (pfd == -1) {
+ if (errno == ENOENT) {
+ printf("%s:SKIP:no PERF_SAMPLE_BRANCH_STACK\n",
+ __func__);
+ test__skip();
+ return;
+ }
+ if (CHECK(pfd < 0, "perf_event_open", "err %d\n", pfd))
+ return;
+ }
+
+ test_perf_branches_common(pfd, on_good_sample);
+
+ close(pfd);
+}
+
+/*
+ * Tests negative case -- run bpf_read_branch_records() on improperly configured
+ * perf event.
+ */
+static void test_perf_branches_no_hw(void)
+{
+ struct perf_event_attr attr = {0};
+ int duration = 0;
+ int pfd;
+
+ /* create perf event */
+ attr.size = sizeof(attr);
+ attr.type = PERF_TYPE_SOFTWARE;
+ attr.config = PERF_COUNT_SW_CPU_CLOCK;
+ attr.freq = 1;
+ attr.sample_freq = 4000;
+ pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
+ if (CHECK(pfd < 0, "perf_event_open", "err %d\n", pfd))
+ return;
+
+ test_perf_branches_common(pfd, on_bad_sample);
+
+ close(pfd);
+}
+
+void test_perf_branches(void)
+{
+ if (test__start_subtest("perf_branches_hw"))
+ test_perf_branches_hw();
+ if (test__start_subtest("perf_branches_no_hw"))
+ test_perf_branches_no_hw();
+}
diff --git a/tools/testing/selftests/bpf/progs/test_perf_branches.c b/tools/testing/selftests/bpf/progs/test_perf_branches.c
new file mode 100644
index 000000000000..60327d512400
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_perf_branches.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <stddef.h>
+#include <linux/ptrace.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_trace_helpers.h"
+
+struct fake_perf_branch_entry {
+ __u64 _a;
+ __u64 _b;
+ __u64 _c;
+};
+
+struct output {
+ int required_size;
+ int written_stack;
+ int written_map;
+};
+
+struct {
+ __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
+ __uint(key_size, sizeof(int));
+ __uint(value_size, sizeof(int));
+} perf_buf_map SEC(".maps");
+
+typedef struct fake_perf_branch_entry fpbe_t[30];
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 1);
+ __type(key, __u32);
+ __type(value, fpbe_t);
+} scratch_map SEC(".maps");
+
+SEC("perf_event")
+int perf_branches(void *ctx)
+{
+ struct fake_perf_branch_entry entries[4] = {0};
+ struct output output = {0};
+ __u32 key = 0, *value;
+
+ /* write to stack */
+ output.written_stack = bpf_read_branch_records(ctx, entries,
+ sizeof(entries), 0);
+ /* ignore spurious events */
+ if (!output.written_stack)
+ return 1;
+
+ /* get required size */
+ output.required_size =
+ bpf_read_branch_records(ctx, NULL, 0,
+ BPF_F_GET_BRANCH_RECORDS_SIZE);
+
+ /* write to map */
+ value = bpf_map_lookup_elem(&scratch_map, &key);
+ if (value)
+ output.written_map =
+ bpf_read_branch_records(ctx,
+ value,
+ 30 * sizeof(struct fake_perf_branch_entry),
+ 0);
+
+ /* ignore spurious events */
+ if (!output.written_map)
+ return 1;
+
+ bpf_perf_event_output(ctx, &perf_buf_map, BPF_F_CURRENT_CPU,
+ &output, sizeof(output));
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.21.1
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