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/bpf_helpers.h>
  12 #include <bpf/bpf_tracing.h>
  13
  14 struct bpf_map_def SEC("maps") my_map = {
  15         .type = BPF_MAP_TYPE_HASH,
  16         .key_size = sizeof(long),
  17         .value_size = sizeof(long),
  18         .max_entries = 1024,
  19 };
  20
  21 /* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe
  22  * example will no longer be meaningful
  23  */
  24 SEC("kprobe/kfree_skb")
  25 int bpf_prog2(struct pt_regs *ctx)
  26 {
  27         long loc = 0;
  28         long init_val = 1;
  29         long *value;
  30
  31         /* read ip of kfree_skb caller.
  32          * non-portable version of __builtin_return_address(0)
  33          */
  34         BPF_KPROBE_READ_RET_IP(loc, ctx);
  35
  36         value = bpf_map_lookup_elem(&my_map, &loc);
  37         if (value)
  38                 *value += 1;
  39         else
  40                 bpf_map_update_elem(&my_map, &loc, &init_val, BPF_ANY);
  41         return 0;
  42 }
  43
  44 static unsigned int log2(unsigned int v)
  45 {
  46         unsigned int r;
  47         unsigned int shift;
  48
  49         r = (v > 0xFFFF) << 4; v >>= r;
  50         shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
  51         shift = (v > 0xF) << 2; v >>= shift; r |= shift;
  52         shift = (v > 0x3) << 1; v >>= shift; r |= shift;
  53         r |= (v >> 1);
  54         return r;
  55 }
  56
  57 static unsigned int log2l(unsigned long v)
  58 {
  59         unsigned int hi = v >> 32;
  60         if (hi)
  61                 return log2(hi) + 32;
  62         else
  63                 return log2(v);
  64 }
  65
  66 struct hist_key {
  67         char comm[16];
  68         u64 pid_tgid;
  69         u64 uid_gid;
  70         u64 index;
  71 };
  72
  73 struct bpf_map_def SEC("maps") my_hist_map = {
  74         .type = BPF_MAP_TYPE_PERCPU_HASH,
  75         .key_size = sizeof(struct hist_key),
  76         .value_size = sizeof(long),
  77         .max_entries = 1024,
  78 };
  79
  80 SEC("kprobe/sys_write")
  81 int bpf_prog3(struct pt_regs *ctx)
  82 {
  83         long write_size = PT_REGS_PARM3(ctx);
  84         long init_val = 1;
  85         long *value;
  86         struct hist_key key;
  87
  88         key.index = log2l(write_size);
  89         key.pid_tgid = bpf_get_current_pid_tgid();
  90         key.uid_gid = bpf_get_current_uid_gid();
  91         bpf_get_current_comm(&key.comm, sizeof(key.comm));
  92
  93         value = bpf_map_lookup_elem(&my_hist_map, &key);
  94         if (value)
  95                 __sync_fetch_and_add(value, 1);
  96         else
  97                 bpf_map_update_elem(&my_hist_map, &key, &init_val, BPF_ANY);
  98         return 0;
  99 }
 100 char _license[] SEC("license") = "GPL";
 101 u32 _version SEC("version") = LINUX_VERSION_CODE;