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 <uapi/linux/unistd.h>
  12#include "bpf_helpers.h"
  13
  14#define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
  15
  16struct bpf_map_def SEC("maps") progs = {
  17        .type = BPF_MAP_TYPE_PROG_ARRAY,
  18        .key_size = sizeof(u32),
  19        .value_size = sizeof(u32),
  20        .max_entries = 1024,
  21};
  22
  23SEC("kprobe/__seccomp_filter")
  24int bpf_prog1(struct pt_regs *ctx)
  25{
  26        int sc_nr = (int)PT_REGS_PARM1(ctx);
  27
  28        /* dispatch into next BPF program depending on syscall number */
  29        bpf_tail_call(ctx, &progs, sc_nr);
  30
  31        /* fall through -> unknown syscall */
  32        if (sc_nr >= __NR_getuid && sc_nr <= __NR_getsid) {
  33                char fmt[] = "syscall=%d (one of get/set uid/pid/gid)\n";
  34                bpf_trace_printk(fmt, sizeof(fmt), sc_nr);
  35        }
  36        return 0;
  37}
  38
  39/* we jump here when syscall number == __NR_write */
  40PROG(__NR_write)(struct pt_regs *ctx)
  41{
  42        struct seccomp_data sd;
  43
  44        bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
  45        if (sd.args[2] == 512) {
  46                char fmt[] = "write(fd=%d, buf=%p, size=%d)\n";
  47                bpf_trace_printk(fmt, sizeof(fmt),
  48                                 sd.args[0], sd.args[1], sd.args[2]);
  49        }
  50        return 0;
  51}
  52
  53PROG(__NR_read)(struct pt_regs *ctx)
  54{
  55        struct seccomp_data sd;
  56
  57        bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
  58        if (sd.args[2] > 128 && sd.args[2] <= 1024) {
  59                char fmt[] = "read(fd=%d, buf=%p, size=%d)\n";
  60                bpf_trace_printk(fmt, sizeof(fmt),
  61                                 sd.args[0], sd.args[1], sd.args[2]);
  62        }
  63        return 0;
  64}
  65
  66PROG(__NR_mmap)(struct pt_regs *ctx)
  67{
  68        char fmt[] = "mmap\n";
  69        bpf_trace_printk(fmt, sizeof(fmt));
  70        return 0;
  71}
  72
  73char _license[] SEC("license") = "GPL";
  74u32 _version SEC("version") = LINUX_VERSION_CODE;
  75