samples/bpf/tracex5_kern.c

   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
  15 struct 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
  22 SEC("kprobe/seccomp_phase1")
  23 int bpf_prog1(struct pt_regs *ctx)
  24 {
  25         struct seccomp_data sd = {};
  26
  27         bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
  28
  29         /* dispatch into next BPF program depending on syscall number */
  30         bpf_tail_call(ctx, &progs, sd.nr);
  31
  32         /* fall through -> unknown syscall */
  33         if (sd.nr >= __NR_getuid && sd.nr <= __NR_getsid) {
  34                 char fmt[] = "syscall=%d (one of get/set uid/pid/gid)\n";
  35                 bpf_trace_printk(fmt, sizeof(fmt), sd.nr);
  36         }
  37         return 0;
  38 }
  39
  40 /* we jump here when syscall number == __NR_write */
  41 PROG(__NR_write)(struct pt_regs *ctx)
  42 {
  43         struct seccomp_data sd = {};
  44
  45         bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
  46         if (sd.args[2] == 512) {
  47                 char fmt[] = "write(fd=%d, buf=%p, size=%d)\n";
  48                 bpf_trace_printk(fmt, sizeof(fmt),
  49                                  sd.args[0], sd.args[1], sd.args[2]);
  50         }
  51         return 0;
  52 }
  53
  54 PROG(__NR_read)(struct pt_regs *ctx)
  55 {
  56         struct seccomp_data sd = {};
  57
  58         bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
  59         if (sd.args[2] > 128 && sd.args[2] <= 1024) {
  60                 char fmt[] = "read(fd=%d, buf=%p, size=%d)\n";
  61                 bpf_trace_printk(fmt, sizeof(fmt),
  62                                  sd.args[0], sd.args[1], sd.args[2]);
  63         }
  64         return 0;
  65 }
  66
  67 PROG(__NR_mmap)(struct pt_regs *ctx)
  68 {
  69         char fmt[] = "mmap\n";
  70         bpf_trace_printk(fmt, sizeof(fmt));
  71         return 0;
  72 }
  73
  74 char _license[] SEC("license") = "GPL";
  75 u32 _version SEC("version") = LINUX_VERSION_CODE;