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Date: Sat, 6 Jul 2019 17:18:47 +0000
From: Yonghong Song <yhs@...com>
To: Andrii Nakryiko <andriin@...com>,
"andrii.nakryiko@...il.com" <andrii.nakryiko@...il.com>,
"bpf@...r.kernel.org" <bpf@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Alexei Starovoitov <ast@...com>,
"daniel@...earbox.net" <daniel@...earbox.net>,
Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH v6 bpf-next 3/5] selftests/bpf: test perf buffer API
On 7/5/19 11:02 PM, Andrii Nakryiko wrote:
> Add test verifying perf buffer API functionality.
>
> Signed-off-by: Andrii Nakryiko <andriin@...com>
> Acked-by: Song Liu <songliubraving@...com>
> ---
> .../selftests/bpf/prog_tests/perf_buffer.c | 94 +++++++++++++++++++
> .../selftests/bpf/progs/test_perf_buffer.c | 25 +++++
> 2 files changed, 119 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_buffer.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_perf_buffer.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/perf_buffer.c b/tools/testing/selftests/bpf/prog_tests/perf_buffer.c
> new file mode 100644
> index 000000000000..64556ab0d1a9
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/perf_buffer.c
> @@ -0,0 +1,94 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <pthread.h>
> +#include <sched.h>
> +#include <sys/socket.h>
> +#include <test_progs.h>
> +
> +static void on_sample(void *ctx, int cpu, void *data, __u32 size)
> +{
> + int cpu_data = *(int *)data, duration = 0;
> + cpu_set_t *cpu_seen = ctx;
> +
> + if (cpu_data != cpu)
> + CHECK(cpu_data != cpu, "check_cpu_data",
> + "cpu_data %d != cpu %d\n", cpu_data, cpu);
> +
> + CPU_SET(cpu, cpu_seen);
> +}
> +
> +void test_perf_buffer(void)
> +{
> + int err, prog_fd, nr_cpus, i, duration = 0;
> + const char *prog_name = "kprobe/sys_nanosleep";
> + const char *file = "./test_perf_buffer.o";
> + struct perf_buffer_opts pb_opts = {};
> + struct bpf_map *perf_buf_map;
> + cpu_set_t cpu_set, cpu_seen;
> + struct bpf_program *prog;
> + struct bpf_object *obj;
> + struct perf_buffer *pb;
> + struct bpf_link *link;
> +
> + nr_cpus = libbpf_num_possible_cpus();
> + if (CHECK(nr_cpus < 0, "nr_cpus", "err %d\n", nr_cpus))
> + return;
> +
> + /* load program */
> + err = bpf_prog_load(file, BPF_PROG_TYPE_KPROBE, &obj, &prog_fd);
> + if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno))
> + return;
> +
> + prog = bpf_object__find_program_by_title(obj, prog_name);
> + if (CHECK(!prog, "find_probe", "prog '%s' not found\n", prog_name))
> + goto out_close;
> +
> + /* load map */
> + perf_buf_map = bpf_object__find_map_by_name(obj, "perf_buf_map");
> + if (CHECK(!perf_buf_map, "find_perf_buf_map", "not found\n"))
> + goto out_close;
> +
> + /* attach kprobe */
> + link = bpf_program__attach_kprobe(prog, false /* retprobe */,
> + "sys_nanosleep");
The attach function "sys_nanosleep" won't work. You can have something
similar to attach_probe.c.
#ifdef __x86_64__
#define SYS_KPROBE_NAME "__x64_sys_nanosleep"
#else
#define SYS_KPROBE_NAME "sys_nanosleep"
#endif
> + if (CHECK(IS_ERR(link), "attach_kprobe", "err %ld\n", PTR_ERR(link)))
> + goto out_close;
> +
> + /* set up perf buffer */
> + pb_opts.sample_cb = on_sample;
> + pb_opts.ctx = &cpu_seen;
> + pb = perf_buffer__new(bpf_map__fd(perf_buf_map), 1, &pb_opts);
> + if (CHECK(IS_ERR(pb), "perf_buf__new", "err %ld\n", PTR_ERR(pb)))
> + goto out_detach;
> +
> + /* trigger kprobe on every CPU */
> + CPU_ZERO(&cpu_seen);
> + for (i = 0; i < nr_cpus; i++) {
> + CPU_ZERO(&cpu_set);
> + CPU_SET(i, &cpu_set);
> +
> + err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set),
> + &cpu_set);
> + if (err && CHECK(err, "set_affinity", "cpu #%d, err %d\n",
> + i, err))
> + goto out_detach;
> +
> + usleep(1);
> + }
> +
> + /* read perf buffer */
> + err = perf_buffer__poll(pb, 100);
> + if (CHECK(err < 0, "perf_buffer__poll", "err %d\n", err))
> + goto out_free_pb;
> +
> + if (CHECK(CPU_COUNT(&cpu_seen) != nr_cpus, "seen_cpu_cnt",
> + "expect %d, seen %d\n", nr_cpus, CPU_COUNT(&cpu_seen)))
> + goto out_free_pb;
> +
> +out_free_pb:
> + perf_buffer__free(pb);
> +out_detach:
> + bpf_link__destroy(link);
> +out_close:
> + bpf_object__close(obj);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_perf_buffer.c b/tools/testing/selftests/bpf/progs/test_perf_buffer.c
> new file mode 100644
> index 000000000000..876c27deb65a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_perf_buffer.c
> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2019 Facebook
> +
> +#include <linux/ptrace.h>
> +#include <linux/bpf.h>
> +#include "bpf_helpers.h"
> +
> +struct {
> + __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
> + __uint(key_size, sizeof(int));
> + __uint(value_size, sizeof(int));
> +} perf_buf_map SEC(".maps");
> +
> +SEC("kprobe/sys_nanosleep")
> +int handle_sys_nanosleep_entry(struct pt_regs *ctx)
> +{
> + int cpu = bpf_get_smp_processor_id();
> +
> + bpf_perf_event_output(ctx, &perf_buf_map, BPF_F_CURRENT_CPU,
> + &cpu, sizeof(cpu));
> + return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> +__u32 _version SEC("version") = 1;
>
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