samples/bpf/trace_event_kern.c

   1 /* Copyright (c) 2016 Facebook
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  */
   7 #include <linux/ptrace.h>
   8 #include <linux/version.h>
   9 #include <uapi/linux/bpf.h>
  10 #include <uapi/linux/bpf_perf_event.h>
  11 #include <uapi/linux/perf_event.h>
  12 #include "bpf_helpers.h"
  13
  14 struct key_t {
  15         char comm[TASK_COMM_LEN];
  16         u32 kernstack;
  17         u32 userstack;
  18 };
  19
  20 struct bpf_map_def SEC("maps") counts = {
  21         .type = BPF_MAP_TYPE_HASH,
  22         .key_size = sizeof(struct key_t),
  23         .value_size = sizeof(u64),
  24         .max_entries = 10000,
  25 };
  26
  27 struct bpf_map_def SEC("maps") stackmap = {
  28         .type = BPF_MAP_TYPE_STACK_TRACE,
  29         .key_size = sizeof(u32),
  30         .value_size = PERF_MAX_STACK_DEPTH * sizeof(u64),
  31         .max_entries = 10000,
  32 };
  33
  34 #define KERN_STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP)
  35 #define USER_STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP | BPF_F_USER_STACK)
  36
  37 SEC("perf_event")
  38 int bpf_prog1(struct bpf_perf_event_data *ctx)
  39 {
  40         char fmt[] = "CPU-%d period %lld ip %llx";
  41         u32 cpu = bpf_get_smp_processor_id();
  42         struct key_t key;
  43         u64 *val, one = 1;
  44
  45         if (ctx->sample_period < 10000)
  46                 /* ignore warmup */
  47                 return 0;
  48         bpf_get_current_comm(&key.comm, sizeof(key.comm));
  49         key.kernstack = bpf_get_stackid(ctx, &stackmap, KERN_STACKID_FLAGS);
  50         key.userstack = bpf_get_stackid(ctx, &stackmap, USER_STACKID_FLAGS);
  51         if ((int)key.kernstack < 0 && (int)key.userstack < 0) {
  52                 bpf_trace_printk(fmt, sizeof(fmt), cpu, ctx->sample_period,
  53                                  PT_REGS_IP(&ctx->regs));
  54                 return 0;
  55         }
  56
  57         val = bpf_map_lookup_elem(&counts, &key);
  58         if (val)
  59                 (*val)++;
  60         else
  61                 bpf_map_update_elem(&counts, &key, &one, BPF_NOEXIST);
  62         return 0;
  63 }
  64
  65 char _license[] SEC("license") = "GPL";