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_filter")
  23 int 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 */
  39 PROG(__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
  52 PROG(__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
  65 PROG(__NR_mmap)(struct pt_regs *ctx)
  66 {
  67         char fmt[] = "mmap\n";
  68         bpf_trace_printk(fmt, sizeof(fmt));
  69         return 0;
  70 }
  71
  72 char _license[] SEC("license") = "GPL";
  73 u32 _version SEC("version") = LINUX_VERSION_CODE;