bpf/prog_tests/perf_link.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /* Copyright (c) 2021 Facebook */
0003 #define _GNU_SOURCE
0004 #include <pthread.h>
0005 #include <sched.h>
0006 #include <test_progs.h>
0007 #include "test_perf_link.skel.h"
0008
0009 static void burn_cpu(void)
0010 {
0011     volatile int j = 0;
0012     cpu_set_t cpu_set;
0013     int i, err;
0014
0015     /* generate some branches on cpu 0 */
0016     CPU_ZERO(&cpu_set);
0017     CPU_SET(0, &cpu_set);
0018     err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set), &cpu_set);
0019     ASSERT_OK(err, "set_thread_affinity");
0020
0021     /* spin the loop for a while (random high number) */
0022     for (i = 0; i < 1000000; ++i)
0023         ++j;
0024 }
0025
0026 /* TODO: often fails in concurrent mode */
0027 void serial_test_perf_link(void)
0028 {
0029     struct test_perf_link *skel = NULL;
0030     struct perf_event_attr attr;
0031     int pfd = -1, link_fd = -1, err;
0032     int run_cnt_before, run_cnt_after;
0033     struct bpf_link_info info;
0034     __u32 info_len = sizeof(info);
0035
0036     /* create perf event */
0037     memset(&attr, 0, sizeof(attr));
0038     attr.size = sizeof(attr);
0039     attr.type = PERF_TYPE_SOFTWARE;
0040     attr.config = PERF_COUNT_SW_CPU_CLOCK;
0041     attr.freq = 1;
0042     attr.sample_freq = 1000;
0043     pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
0044     if (!ASSERT_GE(pfd, 0, "perf_fd"))
0045         goto cleanup;
0046
0047     skel = test_perf_link__open_and_load();
0048     if (!ASSERT_OK_PTR(skel, "skel_load"))
0049         goto cleanup;
0050
0051     link_fd = bpf_link_create(bpf_program__fd(skel->progs.handler), pfd,
0052                   BPF_PERF_EVENT, NULL);
0053     if (!ASSERT_GE(link_fd, 0, "link_fd"))
0054         goto cleanup;
0055
0056     memset(&info, 0, sizeof(info));
0057     err = bpf_obj_get_info_by_fd(link_fd, &info, &info_len);
0058     if (!ASSERT_OK(err, "link_get_info"))
0059         goto cleanup;
0060
0061     ASSERT_EQ(info.type, BPF_LINK_TYPE_PERF_EVENT, "link_type");
0062     ASSERT_GT(info.id, 0, "link_id");
0063     ASSERT_GT(info.prog_id, 0, "link_prog_id");
0064
0065     /* ensure we get at least one perf_event prog execution */
0066     burn_cpu();
0067     ASSERT_GT(skel->bss->run_cnt, 0, "run_cnt");
0068
0069     /* perf_event is still active, but we close link and BPF program
0070      * shouldn't be executed anymore
0071      */
0072     close(link_fd);
0073     link_fd = -1;
0074
0075     /* make sure there are no stragglers */
0076     kern_sync_rcu();
0077
0078     run_cnt_before = skel->bss->run_cnt;
0079     burn_cpu();
0080     run_cnt_after = skel->bss->run_cnt;
0081
0082     ASSERT_EQ(run_cnt_before, run_cnt_after, "run_cnt_before_after");
0083
0084 cleanup:
0085     if (link_fd >= 0)
0086         close(link_fd);
0087     if (pfd >= 0)
0088         close(pfd);
0089     test_perf_link__destroy(skel);
0090 }