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