samples/bpf/tracex4_kern.c

   1 /* Copyright (c) 2015 PLUMgrid, http://plumgrid.com
   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 "bpf_helpers.h"
  11
  12 struct pair {
  13         u64 val;
  14         u64 ip;
  15 };
  16
  17 struct bpf_map_def SEC("maps") my_map = {
  18         .type = BPF_MAP_TYPE_HASH,
  19         .key_size = sizeof(long),
  20         .value_size = sizeof(struct pair),
  21         .max_entries = 1000000,
  22 };
  23
  24 /* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe
  25  * example will no longer be meaningful
  26  */
  27 SEC("kprobe/kmem_cache_free")
  28 int bpf_prog1(struct pt_regs *ctx)
  29 {
  30         long ptr = ctx->si;
  31
  32         bpf_map_delete_elem(&my_map, &ptr);
  33         return 0;
  34 }
  35
  36 SEC("kretprobe/kmem_cache_alloc_node")
  37 int bpf_prog2(struct pt_regs *ctx)
  38 {
  39         long ptr = ctx->ax;
  40         long ip = 0;
  41
  42         /* get ip address of kmem_cache_alloc_node() caller */
  43         bpf_probe_read(&ip, sizeof(ip), (void *)(ctx->bp + sizeof(ip)));
  44
  45         struct pair v = {
  46                 .val = bpf_ktime_get_ns(),
  47                 .ip = ip,
  48         };
  49
  50         bpf_map_update_elem(&my_map, &ptr, &v, BPF_ANY);
  51         return 0;
  52 }
  53 char _license[] SEC("license") = "GPL";
  54 u32 _version SEC("version") = LINUX_VERSION_CODE;