Re: [PATCH v2 bpf-next 2/2] selftests/bpf: add callchain_stackid
From: Andrii Nakryiko <hidden>
Date: 2020-07-16 06:05:15
Also in:
bpf, lkml
On Tue, Jul 14, 2020 at 11:09 PM Song Liu [off-list ref] wrote:
This tests new helper function bpf_get_stackid_pe and bpf_get_stack_pe. These two helpers have different implementation for perf_event with PEB entries. Signed-off-by: Song Liu <redacted> --- .../bpf/prog_tests/perf_event_stackmap.c | 120 ++++++++++++++++++ .../selftests/bpf/progs/perf_event_stackmap.c | 64 ++++++++++ 2 files changed, 184 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_event_stackmap.c create mode 100644 tools/testing/selftests/bpf/progs/perf_event_stackmap.c
Just few simplification suggestions, but overall looks good, so please add: Acked-by: Andrii Nakryiko <redacted> [...]
+
+void test_perf_event_stackmap(void)
+{
+ struct perf_event_attr attr = {
+ /* .type = PERF_TYPE_SOFTWARE, */
+ .type = PERF_TYPE_HARDWARE,
+ .config = PERF_COUNT_HW_CPU_CYCLES,
+ .precise_ip = 2,
+ .sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_BRANCH_STACK |
+ PERF_SAMPLE_CALLCHAIN,
+ .branch_sample_type = PERF_SAMPLE_BRANCH_USER |
+ PERF_SAMPLE_BRANCH_NO_FLAGS |
+ PERF_SAMPLE_BRANCH_NO_CYCLES |
+ PERF_SAMPLE_BRANCH_CALL_STACK,
+ .sample_period = 5000,
+ .size = sizeof(struct perf_event_attr),
+ };
+ struct perf_event_stackmap *skel;
+ __u32 duration = 0;
+ cpu_set_t cpu_set;
+ int pmu_fd, err;
+
+ skel = perf_event_stackmap__open();
+
+ if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
+ return;
+
+ /* override program type */
+ bpf_program__set_perf_event(skel->progs.oncpu);this should be unnecessary, didn't libbpf detect the type correctly from SEC? If not, let's fix that.
+
+ err = perf_event_stackmap__load(skel);
+ if (CHECK(err, "skel_load", "skeleton load failed: %d\n", err))
+ goto cleanup;
+
+ 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", "err %d, errno %d\n", err, errno))
+ goto cleanup;
+
+ pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
+ 0 /* cpu 0 */, -1 /* group id */,
+ 0 /* flags */);
+ if (pmu_fd < 0) {
+ printf("%s:SKIP:cpu doesn't support the event\n", __func__);
+ test__skip();
+ goto cleanup;
+ }
+
+ skel->links.oncpu = bpf_program__attach_perf_event(skel->progs.oncpu,
+ pmu_fd);
+ if (CHECK(IS_ERR(skel->links.oncpu), "attach_perf_event",
+ "err %ld\n", PTR_ERR(skel->links.oncpu))) {
+ close(pmu_fd);
+ goto cleanup;
+ }
+
+ /* create kernel and user stack traces for testing */
+ func_6();
+
+ CHECK(skel->data->stackid_kernel != 2, "get_stackid_kernel", "failed\n");
+ CHECK(skel->data->stackid_user != 2, "get_stackid_user", "failed\n");
+ CHECK(skel->data->stack_kernel != 2, "get_stack_kernel", "failed\n");
+ CHECK(skel->data->stack_user != 2, "get_stack_user", "failed\n");
+ close(pmu_fd);I think pmu_fd will be closed by perf_event_stackmap__destory (through closing the link)
quoted hunk
+ +cleanup: + perf_event_stackmap__destroy(skel); +}diff --git a/tools/testing/selftests/bpf/progs/perf_event_stackmap.c b/tools/testing/selftests/bpf/progs/perf_event_stackmap.c new file mode 100644 index 0000000000000..1b0457efeedec --- /dev/null +++ b/tools/testing/selftests/bpf/progs/perf_event_stackmap.c@@ -0,0 +1,64 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (c) 2020 Facebook +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> + +#ifndef PERF_MAX_STACK_DEPTH +#define PERF_MAX_STACK_DEPTH 127 +#endif + +#ifndef BPF_F_USER_STACK +#define BPF_F_USER_STACK (1ULL << 8) +#endif
BPF_F_USER_STACK should be in vmlinux.h already, similarly to BPF_F_CURRENT_CPU
+
+typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
+struct {
+ __uint(type, BPF_MAP_TYPE_STACK_TRACE);
+ __uint(max_entries, 16384);
+ __uint(key_size, sizeof(__u32));
+ __uint(value_size, sizeof(stack_trace_t));
+} stackmap SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+ __uint(max_entries, 1);
+ __type(key, __u32);
+ __type(value, stack_trace_t);
+} stackdata_map SEC(".maps");
+
+long stackid_kernel = 1;
+long stackid_user = 1;
+long stack_kernel = 1;
+long stack_user = 1;
+nit: kind of unusual to go from 1 -> 2, why no zero to one as a flag? those variables will be available through skel->bss, btw
+SEC("perf_event")
+int oncpu(void *ctx)
+{
+ int max_len = PERF_MAX_STACK_DEPTH * sizeof(__u64);
+ stack_trace_t *trace;
+ __u32 key = 0;
+ long val;
+
+ val = bpf_get_stackid(ctx, &stackmap, 0);
+ if (val > 0)
+ stackid_kernel = 2;
+ val = bpf_get_stackid(ctx, &stackmap, BPF_F_USER_STACK);
+ if (val > 0)
+ stackid_user = 2;
+
+ trace = bpf_map_lookup_elem(&stackdata_map, &key);
+ if (!trace)
+ return 0;
+
+ val = bpf_get_stack(ctx, trace, max_len, 0);
given you don't care about contents of trace, you could have used
`stack_trace_t trace = {}` global variable instead of PERCPU_ARRAY.
+ if (val > 0) + stack_kernel = 2; + + val = bpf_get_stack(ctx, trace, max_len, BPF_F_USER_STACK);
nit: max_len == sizeof(stack_trace_t) ?
+ if (val > 0)
+ stack_user = 2;
+
+ return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";
--
2.24.1