selftests/bpf: Test low-level perf BPF link API

// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2021 Facebook */

#define _GNU_SOURCE

#include <pthread.h>

#include <sched.h>

#include <test_progs.h>

#include "test_perf_link.skel.h"

static void burn_cpu(void)

{

	volatile int j = 0;

	cpu_set_t cpu_set;

	int i, err;

	/* 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);

	ASSERT_OK(err, "set_thread_affinity");

	/* spin the loop for a while (random high number) */

	for (i = 0; i < 1000000; ++i)

		++j;

}

void test_perf_link(void)

{

	struct test_perf_link *skel = NULL;

	struct perf_event_attr attr;

	int pfd = -1, link_fd = -1, err;

	int run_cnt_before, run_cnt_after;

	struct bpf_link_info info;

	__u32 info_len = sizeof(info);

	/* create perf event */

	memset(&attr, 0, sizeof(attr));

	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 (!ASSERT_GE(pfd, 0, "perf_fd"))

		goto cleanup;

	skel = test_perf_link__open_and_load();

	if (!ASSERT_OK_PTR(skel, "skel_load"))

		goto cleanup;

	link_fd = bpf_link_create(bpf_program__fd(skel->progs.handler), pfd,

				  BPF_PERF_EVENT, NULL);

	if (!ASSERT_GE(link_fd, 0, "link_fd"))

		goto cleanup;

	memset(&info, 0, sizeof(info));

	err = bpf_obj_get_info_by_fd(link_fd, &info, &info_len);

	if (!ASSERT_OK(err, "link_get_info"))

		goto cleanup;

	ASSERT_EQ(info.type, BPF_LINK_TYPE_PERF_EVENT, "link_type");

	ASSERT_GT(info.id, 0, "link_id");

	ASSERT_GT(info.prog_id, 0, "link_prog_id");

	/* ensure we get at least one perf_event prog execution */

	burn_cpu();

	ASSERT_GT(skel->bss->run_cnt, 0, "run_cnt");

	/* perf_event is still active, but we close link and BPF program

	 * shouldn't be executed anymore

	 */

	close(link_fd);

	link_fd = -1;

	/* make sure there are no stragglers */

	kern_sync_rcu();

	run_cnt_before = skel->bss->run_cnt;

	burn_cpu();

	run_cnt_after = skel->bss->run_cnt;

	ASSERT_EQ(run_cnt_before, run_cnt_after, "run_cnt_before_after");

cleanup:

	if (link_fd >= 0)

		close(link_fd);

	if (pfd >= 0)

		close(pfd);

	test_perf_link__destroy(skel);

}

// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2021 Facebook */

#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>

int run_cnt = 0;

SEC("perf_event")

int handler(struct pt_regs *ctx)

{

	__sync_fetch_and_add(&run_cnt, 1);

	return 0;

}

char _license[] SEC("license") = "GPL";