LXR linux/samples/bpf/tracex5

   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 <uapi/linux/seccomp.h>
  11#include "bpf_helpers.h"
  12
  13#define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
  14
  15struct bpf_map_def SEC("maps") progs = {
  16        .type = BPF_MAP_TYPE_PROG_ARRAY,
  17        .key_size = sizeof(u32),
  18        .value_size = sizeof(u32),
  19        .max_entries = 1024,
  20};
  21
  22SEC("kprobe/__seccomp_filter")
  23int bpf_prog1(struct pt_regs *ctx)
  24{
  25        int sc_nr = (int)PT_REGS_PARM1(ctx);
  26
  27        /* dispatch into next BPF program depending on syscall number */
  28        bpf_tail_call(ctx, &progs, sc_nr);
  29
  30        /* fall through -> unknown syscall */
  31        if (sc_nr >= __NR_getuid && sc_nr <= __NR_getsid) {
  32                char fmt[] = "syscall=%d (one of get/set uid/pid/gid)\n";
  33                bpf_trace_printk(fmt, sizeof(fmt), sc_nr);
  34        }
  35        return 0;
  36}
  37
  38/* we jump here when syscall number == __NR_write */
  39PROG(__NR_write)(struct pt_regs *ctx)
  40{
  41        struct seccomp_data sd;
  42
  43        bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
  44        if (sd.args[2] == 512) {
  45                char fmt[] = "write(fd=%d, buf=%p, size=%d)\n";
  46                bpf_trace_printk(fmt, sizeof(fmt),
  47                                 sd.args[0], sd.args[1], sd.args[2]);
  48        }
  49        return 0;
  50}
  51
  52PROG(__NR_read)(struct pt_regs *ctx)
  53{
  54        struct seccomp_data sd;
  55
  56        bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
  57        if (sd.args[2] > 128 && sd.args[2] <= 1024) {
  58                char fmt[] = "read(fd=%d, buf=%p, size=%d)\n";
  59                bpf_trace_printk(fmt, sizeof(fmt),
  60                                 sd.args[0], sd.args[1], sd.args[2]);
  61        }
  62        return 0;
  63}
  64
  65PROG(__NR_mmap)(struct pt_regs *ctx)
  66{
  67        char fmt[] = "mmap\n";
  68        bpf_trace_printk(fmt, sizeof(fmt));
  69        return 0;
  70}
  71
  72char _license[] SEC("license") = "GPL";
  73u32 _version SEC("version") = LINUX_VERSION_CODE;
  74