selftests/bpf: test perf buffer API

Add test verifying perf buffer API functionality.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/prog_tests/perf_buffer.c

+// 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);
+}

tools/testing/selftests/bpf/progs/test_perf_buffer.c

+// 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;