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

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (c) 2020 Facebook
   3
   4 #include <linux/bpf.h>
   5 #include <bpf/bpf_helpers.h>
   6 #include "bpf_misc.h"
   7
   8 char _license[] SEC("license") = "GPL";
   9
  10 struct sample {
  11         int pid;
  12         int seq;
  13         long value;
  14         char comm[16];
  15 };
  16
  17 struct {
  18         __uint(type, BPF_MAP_TYPE_RINGBUF);
  19 } ringbuf SEC(".maps");
  20
  21 /* inputs */
  22 int pid = 0;
  23 long value = 0;
  24 long flags = 0;
  25
  26 /* outputs */
  27 long total = 0;
  28 long discarded = 0;
  29 long dropped = 0;
  30
  31 long avail_data = 0;
  32 long ring_size = 0;
  33 long cons_pos = 0;
  34 long prod_pos = 0;
  35
  36 /* inner state */
  37 long seq = 0;
  38
  39 SEC("fentry/" SYS_PREFIX "sys_getpgid")
  40 int test_ringbuf(void *ctx)
  41 {
  42         int cur_pid = bpf_get_current_pid_tgid() >> 32;
  43         struct sample *sample;
  44
  45         if (cur_pid != pid)
  46                 return 0;
  47
  48         sample = bpf_ringbuf_reserve(&ringbuf, sizeof(*sample), 0);
  49         if (!sample) {
  50                 __sync_fetch_and_add(&dropped, 1);
  51                 return 0;
  52         }
  53
  54         sample->pid = pid;
  55         bpf_get_current_comm(sample->comm, sizeof(sample->comm));
  56         sample->value = value;
  57
  58         sample->seq = seq++;
  59         __sync_fetch_and_add(&total, 1);
  60
  61         if (sample->seq & 1) {
  62                 /* copy from reserved sample to a new one... */
  63                 bpf_ringbuf_output(&ringbuf, sample, sizeof(*sample), flags);
  64                 /* ...and then discard reserved sample */
  65                 bpf_ringbuf_discard(sample, flags);
  66                 __sync_fetch_and_add(&discarded, 1);
  67         } else {
  68                 bpf_ringbuf_submit(sample, flags);
  69         }
  70
  71         avail_data = bpf_ringbuf_query(&ringbuf, BPF_RB_AVAIL_DATA);
  72         ring_size = bpf_ringbuf_query(&ringbuf, BPF_RB_RING_SIZE);
  73         cons_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_CONS_POS);
  74         prod_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_PROD_POS);
  75
  76         return 0;
  77 }