LXR linux/samples/bpf/tracex2

   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
  14struct 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 */
  24SEC("kprobe/kfree_skb")
  25int 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
  44static 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
  57static 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
  66struct hist_key {
  67        char comm[16];
  68        u64 pid_tgid;
  69        u64 uid_gid;
  70        u64 index;
  71};
  72
  73struct 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
  80SEC("kprobe/sys_write")
  81int 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}
 100char _license[] SEC("license") = "GPL";
 101u32 _version SEC("version") = LINUX_VERSION_CODE;
 102