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/bpf_helpers.h>
  14 #include <bpf/bpf_tracing.h>
  15
  16 #define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
  17
  18 struct {
  19         __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
  20         __uint(key_size, sizeof(u32));
  21         __uint(value_size, sizeof(u32));
  22 #ifdef __mips__
  23         __uint(max_entries, 6000); /* MIPS n64 syscalls start at 5000 */
  24 #else
  25         __uint(max_entries, 1024);
  26 #endif
  27 } progs SEC(".maps");
  28
  29 SEC("kprobe/__seccomp_filter")
  30 int bpf_prog1(struct pt_regs *ctx)
  31 {
  32         int sc_nr = (int)PT_REGS_PARM1(ctx);
  33
  34         /* dispatch into next BPF program depending on syscall number */
  35         bpf_tail_call(ctx, &progs, sc_nr);
  36
  37         /* fall through -> unknown syscall */
  38         if (sc_nr >= __NR_getuid && sc_nr <= __NR_getsid) {
  39                 char fmt[] = "syscall=%d (one of get/set uid/pid/gid)\n";
  40                 bpf_trace_printk(fmt, sizeof(fmt), sc_nr);
  41         }
  42         return 0;
  43 }
  44
  45 /* we jump here when syscall number == __NR_write */
  46 PROG(SYS__NR_write)(struct pt_regs *ctx)
  47 {
  48         struct seccomp_data sd;
  49
  50         bpf_probe_read_kernel(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
  51         if (sd.args[2] == 512) {
  52                 char fmt[] = "write(fd=%d, buf=%p, size=%d)\n";
  53                 bpf_trace_printk(fmt, sizeof(fmt),
  54                                  sd.args[0], sd.args[1], sd.args[2]);
  55         }
  56         return 0;
  57 }
  58
  59 PROG(SYS__NR_read)(struct pt_regs *ctx)
  60 {
  61         struct seccomp_data sd;
  62
  63         bpf_probe_read_kernel(&sd, sizeof(sd), (void *)PT_REGS_PARM2(ctx));
  64         if (sd.args[2] > 128 && sd.args[2] <= 1024) {
  65                 char fmt[] = "read(fd=%d, buf=%p, size=%d)\n";
  66                 bpf_trace_printk(fmt, sizeof(fmt),
  67                                  sd.args[0], sd.args[1], sd.args[2]);
  68         }
  69         return 0;
  70 }
  71
  72 #ifdef __NR_mmap2
  73 PROG(SYS__NR_mmap2)(struct pt_regs *ctx)
  74 {
  75         char fmt[] = "mmap2\n";
  76
  77         bpf_trace_printk(fmt, sizeof(fmt));
  78         return 0;
  79 }
  80 #endif
  81
  82 #ifdef __NR_mmap
  83 PROG(SYS__NR_mmap)(struct pt_regs *ctx)
  84 {
  85         char fmt[] = "mmap\n";
  86
  87         bpf_trace_printk(fmt, sizeof(fmt));
  88         return 0;
  89 }
  90 #endif
  91
  92 char _license[] SEC("license") = "GPL";
  93 u32 _version SEC("version") = LINUX_VERSION_CODE;