LXR linux/samples/bpf/trace_output

   1// SPDX-License-Identifier: GPL-2.0-only
   2#include <stdio.h>
   3#include <fcntl.h>
   4#include <poll.h>
   5#include <time.h>
   6#include <signal.h>
   7#include <bpf/libbpf.h>
   8
   9static __u64 time_get_ns(void)
  10{
  11        struct timespec ts;
  12
  13        clock_gettime(CLOCK_MONOTONIC, &ts);
  14        return ts.tv_sec * 1000000000ull + ts.tv_nsec;
  15}
  16
  17static __u64 start_time;
  18static __u64 cnt;
  19
  20#define MAX_CNT 100000ll
  21
  22static void print_bpf_output(void *ctx, int cpu, void *data, __u32 size)
  23{
  24        struct {
  25                __u64 pid;
  26                __u64 cookie;
  27        } *e = data;
  28
  29        if (e->cookie != 0x12345678) {
  30                printf("BUG pid %llx cookie %llx sized %d\n",
  31                       e->pid, e->cookie, size);
  32                return;
  33        }
  34
  35        cnt++;
  36
  37        if (cnt == MAX_CNT) {
  38                printf("recv %lld events per sec\n",
  39                       MAX_CNT * 1000000000ll / (time_get_ns() - start_time));
  40                return;
  41        }
  42}
  43
  44int main(int argc, char **argv)
  45{
  46        struct perf_buffer_opts pb_opts = {};
  47        struct bpf_link *link = NULL;
  48        struct bpf_program *prog;
  49        struct perf_buffer *pb;
  50        struct bpf_object *obj;
  51        int map_fd, ret = 0;
  52        char filename[256];
  53        FILE *f;
  54
  55        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
  56        obj = bpf_object__open_file(filename, NULL);
  57        if (libbpf_get_error(obj)) {
  58                fprintf(stderr, "ERROR: opening BPF object file failed\n");
  59                return 0;
  60        }
  61
  62        /* load BPF program */
  63        if (bpf_object__load(obj)) {
  64                fprintf(stderr, "ERROR: loading BPF object file failed\n");
  65                goto cleanup;
  66        }
  67
  68        map_fd = bpf_object__find_map_fd_by_name(obj, "my_map");
  69        if (map_fd < 0) {
  70                fprintf(stderr, "ERROR: finding a map in obj file failed\n");
  71                goto cleanup;
  72        }
  73
  74        prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
  75        if (libbpf_get_error(prog)) {
  76                fprintf(stderr, "ERROR: finding a prog in obj file failed\n");
  77                goto cleanup;
  78        }
  79
  80        link = bpf_program__attach(prog);
  81        if (libbpf_get_error(link)) {
  82                fprintf(stderr, "ERROR: bpf_program__attach failed\n");
  83                link = NULL;
  84                goto cleanup;
  85        }
  86
  87        pb_opts.sample_cb = print_bpf_output;
  88        pb = perf_buffer__new(map_fd, 8, &pb_opts);
  89        ret = libbpf_get_error(pb);
  90        if (ret) {
  91                printf("failed to setup perf_buffer: %d\n", ret);
  92                return 1;
  93        }
  94
  95        f = popen("taskset 1 dd if=/dev/zero of=/dev/null", "r");
  96        (void) f;
  97
  98        start_time = time_get_ns();
  99        while ((ret = perf_buffer__poll(pb, 1000)) >= 0 && cnt < MAX_CNT) {
 100        }
 101        kill(0, SIGINT);
 102
 103cleanup:
 104        bpf_link__destroy(link);
 105        bpf_object__close(obj);
 106        return ret;
 107}
 108