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 "syscall_nrs.h"
  13 #include "bpf_helpers.h"
  14
  15 #define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
  16
  17 struct bpf_map_def SEC("maps") progs = {
  18         .type = BPF_MAP_TYPE_PROG_ARRAY,
  19         .key_size = sizeof(u32),
  20         .value_size = sizeof(u32),
  21 #ifdef __mips__
  22         .max_entries = 6000, /* MIPS n64 syscalls start at 5000 */
  23 #else
  24         .max_entries = 1024,
  25 #endif
  26 };
  27
  28 SEC("kprobe/__seccomp_filter")
  29 int bpf_prog1(struct pt_regs *ctx)
  30 {
  31         int sc_nr = (int)PT_REGS_PARM1(ctx);
  32
  33         /* dispatch into next BPF program depending on syscall number */
  34         bpf_tail_call(ctx, &progs, sc_nr);
  35
  36         /* fall through -> unknown syscall */
  37         if (sc_nr >= __NR_getuid && sc_nr <= __NR_getsid) {
  38                 char fmt[] = "syscall=%d (one of get/set uid/pid/gid)\n";
  39                 bpf_trace_printk(fmt, sizeof(fmt), sc_nr);
  40         }
  41         return 0;
  42 }
  43
  44 /* we jump here when syscall number == __NR_write */
  45 PROG(SYS__NR_write)(struct pt_regs *ctx)
  46 {
  47         struct seccomp_data sd;
  48
  49         bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
  50         if (sd.args[2] == 512) {
  51                 char fmt[] = "write(fd=%d, buf=%p, size=%d)\n";
  52                 bpf_trace_printk(fmt, sizeof(fmt),
  53                                  sd.args[0], sd.args[1], sd.args[2]);
  54         }
  55         return 0;
  56 }
  57
  58 PROG(SYS__NR_read)(struct pt_regs *ctx)
  59 {
  60         struct seccomp_data sd;
  61
  62         bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
  63         if (sd.args[2] > 128 && sd.args[2] <= 1024) {
  64                 char fmt[] = "read(fd=%d, buf=%p, size=%d)\n";
  65                 bpf_trace_printk(fmt, sizeof(fmt),
  66                                  sd.args[0], sd.args[1], sd.args[2]);
  67         }
  68         return 0;
  69 }
  70
  71 PROG(SYS__NR_mmap)(struct pt_regs *ctx)
  72 {
  73         char fmt[] = "mmap\n";
  74         bpf_trace_printk(fmt, sizeof(fmt));
  75         return 0;
  76 }
  77
  78 char _license[] SEC("license") = "GPL";
  79 u32 _version SEC("version") = LINUX_VERSION_CODE;