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 <uapi/linux/unistd.h>
  12 #include "bpf_helpers.h"
  13
  14 #define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
  15
  16 struct 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
  23 SEC("kprobe/__seccomp_filter")
  24 int 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 */
  40 PROG(__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
  53 PROG(__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
  66 PROG(__NR_mmap)(struct pt_regs *ctx)
  67 {
  68         char fmt[] = "mmap\n";
  69         bpf_trace_printk(fmt, sizeof(fmt));
  70         return 0;
  71 }
  72
  73 char _license[] SEC("license") = "GPL";
  74 u32 _version SEC("version") = LINUX_VERSION_CODE;