selftests/bpf: test perf buffer API

// SPDX-License-Identifier: GPL-2.0

#define _GNU_SOURCE

#include <pthread.h>

#include <sched.h>

#include <sys/socket.h>

#include <test_progs.h>

#ifdef __x86_64__

#define SYS_KPROBE_NAME "__x64_sys_nanosleep"

#else

#define SYS_KPROBE_NAME "sys_nanosleep"

#endif

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_KPROBE_NAME);

	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);

}

// 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;