samples/bpf/tracex2_kern.c

   1 /* Copyright (c) 2013-2015 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/skbuff.h>
   8 #include <linux/netdevice.h>
   9 #include <linux/version.h>
  10 #include <uapi/linux/bpf.h>
  11 #include "bpf_helpers.h"
  12
  13 struct bpf_map_def SEC("maps") my_map = {
  14         .type = BPF_MAP_TYPE_HASH,
  15         .key_size = sizeof(long),
  16         .value_size = sizeof(long),
  17         .max_entries = 1024,
  18 };
  19
  20 /* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe
  21  * example will no longer be meaningful
  22  */
  23 SEC("kprobe/kfree_skb")
  24 int bpf_prog2(struct pt_regs *ctx)
  25 {
  26         long loc = 0;
  27         long init_val = 1;
  28         long *value;
  29
  30         /* x64 specific: read ip of kfree_skb caller.
  31          * non-portable version of __builtin_return_address(0)
  32          */
  33         bpf_probe_read(&loc, sizeof(loc), (void *)ctx->sp);
  34
  35         value = bpf_map_lookup_elem(&my_map, &loc);
  36         if (value)
  37                 *value += 1;
  38         else
  39                 bpf_map_update_elem(&my_map, &loc, &init_val, BPF_ANY);
  40         return 0;
  41 }
  42
  43 static unsigned int log2(unsigned int v)
  44 {
  45         unsigned int r;
  46         unsigned int shift;
  47
  48         r = (v > 0xFFFF) << 4; v >>= r;
  49         shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
  50         shift = (v > 0xF) << 2; v >>= shift; r |= shift;
  51         shift = (v > 0x3) << 1; v >>= shift; r |= shift;
  52         r |= (v >> 1);
  53         return r;
  54 }
  55
  56 static unsigned int log2l(unsigned long v)
  57 {
  58         unsigned int hi = v >> 32;
  59         if (hi)
  60                 return log2(hi) + 32;
  61         else
  62                 return log2(v);
  63 }
  64
  65 struct bpf_map_def SEC("maps") my_hist_map = {
  66         .type = BPF_MAP_TYPE_ARRAY,
  67         .key_size = sizeof(u32),
  68         .value_size = sizeof(long),
  69         .max_entries = 64,
  70 };
  71
  72 SEC("kprobe/sys_write")
  73 int bpf_prog3(struct pt_regs *ctx)
  74 {
  75         long write_size = ctx->dx; /* arg3 */
  76         long init_val = 1;
  77         long *value;
  78         u32 index = log2l(write_size);
  79
  80         value = bpf_map_lookup_elem(&my_hist_map, &index);
  81         if (value)
  82                 __sync_fetch_and_add(value, 1);
  83         return 0;
  84 }
  85 char _license[] SEC("license") = "GPL";
  86 u32 _version SEC("version") = LINUX_VERSION_CODE;