trace/preload.c

   1 /*
   2  * Copyright (C) 2015 John Crispin <blogic@openwrt.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License version 2.1
   6  * as published by the Free Software Foundation
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #define _GNU_SOURCE
  15 #include <sys/ptrace.h>
  16 #include <sys/types.h>
  17 #include <signal.h>
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20 #include <unistd.h>
  21 #include <string.h>
  22 #include <dlfcn.h>
  23
  24 #include "../preload.h"
  25
  26 #define ERROR(fmt, ...) do { \
  27         fprintf(stderr,"perload-jail: "fmt, ## __VA_ARGS__); \
  28         } while (0)
  29
  30 static main_t __main__;
  31
  32 static int __preload_main__(int argc, char **argv, char **envp)
  33 {
  34         unsetenv("LD_PRELOAD");
  35         ptrace(PTRACE_TRACEME);
  36         kill(getpid(), SIGSTOP);
  37
  38         return (*__main__)(argc, argv, envp);
  39 }
  40
  41 int __libc_start_main(main_t main,
  42                         int argc,
  43                         char **argv,
  44                         ElfW(auxv_t) *auxvec,
  45                         __typeof (main) init,
  46                         void (*fini) (void),
  47                         void (*rtld_fini) (void),
  48                         void *stack_end)
  49 {
  50         start_main_t __start_main__;
  51
  52         __start_main__ = dlsym(RTLD_NEXT, "__libc_start_main");
  53         if (!__start_main__)
  54                 ERROR("failed to find __libc_start_main %s\n", dlerror());
  55
  56         __main__ = main;
  57
  58         return (*__start_main__)(__preload_main__, argc, argv, auxvec,
  59                 init, fini, rtld_fini, stack_end);
  60 }
  61
  62 void __uClibc_main(main_t main,
  63                         int argc,
  64                         char **argv,
  65                         void (*app_init)(void),
  66                         void (*app_fini)(void),
  67                         void (*rtld_fini)(void),
  68                         void *stack_end attribute_unused)
  69 {
  70         uClibc_main __start_main__;
  71
  72         __start_main__ = dlsym(RTLD_NEXT, "__uClibc_main");
  73         if (!__start_main__)
  74                 ERROR("failed to find __uClibc_main %s\n", dlerror());
  75
  76         __main__ = main;
  77
  78         return (*__start_main__)(__preload_main__, argc, argv,
  79                 app_init, app_fini, rtld_fini, stack_end);
  80 }