sysdeps/generic/dl-sysdep.c

   1 /* Operating system support for run-time dynamic linker.  Generic Unix version.
   2 Copyright (C) 1995, 96 Free Software Foundation, Inc.
   3 This file is part of the GNU C Library.
   4
   5 The GNU C Library is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 License, or (at your option) any later version.
   9
  10 The GNU C Library is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, USA.  */
  19
  20 #include <elf.h>
  21 #include <sys/types.h>
  22 #include <sys/stat.h>
  23 #include <sys/mman.h>
  24 #include <fcntl.h>
  25 #include <link.h>
  26 #include <unistd.h>
  27 #include <stdarg.h>
  28 #include <string.h>
  29
  30
  31 extern int _dl_argc;
  32 extern char **_dl_argv;
  33 extern char **_environ;
  34 extern void _start (void);
  35
  36 int __libc_enable_secure;
  37
  38 ElfW(Addr)
  39 _dl_sysdep_start (void **start_argptr,
  40                   void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
  41                                    ElfW(Addr) *user_entry))
  42 {
  43   const ElfW(Phdr) *phdr;
  44   ElfW(Word) phnum;
  45   ElfW(Addr) user_entry;
  46   ElfW(auxv_t) *av;
  47   uid_t uid, euid;
  48   gid_t gid, egid;
  49   unsigned int seen;
  50
  51   user_entry = (ElfW(Addr)) &_start;
  52   _dl_argc = *(long *) start_argptr;
  53   _dl_argv = (char **) start_argptr + 1;
  54   _environ = &_dl_argv[_dl_argc + 1];
  55   start_argptr = (void **) _environ;
  56   while (*start_argptr)
  57     ++start_argptr;
  58
  59   seen = 0;
  60 #define M(type) (1 << (type))
  61
  62   for (av = (void *) ++start_argptr;
  63        av->a_type != AT_NULL;
  64        seen |= M ((++av)->a_type))
  65     switch (av->a_type)
  66       {
  67       case AT_PHDR:
  68         phdr = av->a_un.a_ptr;
  69         break;
  70       case AT_PHNUM:
  71         phnum = av->a_un.a_val;
  72         break;
  73       case AT_ENTRY:
  74         user_entry = av->a_un.a_val;
  75         break;
  76       case AT_UID:
  77         uid = av->a_un.a_val;
  78         break;
  79       case AT_GID:
  80         gid = av->a_un.a_val;
  81         break;
  82       case AT_EUID:
  83         euid = av->a_un.a_val;
  84         break;
  85       case AT_EGID:
  86         egid = av->a_un.a_val;
  87         break;
  88       }
  89
  90   /* Linux doesn't provide us with any of these values on the stack
  91      when the dynamic linker is run directly as a program.  */
  92
  93 #define SEE(UID, uid) if ((seen & M (AT_##UID)) == 0) uid = __get##uid ()
  94   SEE (UID, uid);
  95   SEE (GID, gid);
  96   SEE (EUID, euid);
  97   SEE (EGID, egid);
  98
  99
 100   __libc_enable_secure = uid != euid || gid != egid;
 101
 102 #ifdef DL_SYSDEP_INIT
 103   DL_SYSDEP_INIT;
 104 #endif
 105
 106   (*dl_main) (phdr, phnum, &user_entry);
 107   return user_entry;
 108 }
 109
 110 void
 111 _dl_sysdep_start_cleanup (void)
 112 {
 113 }
 114 \f
 115 #ifndef MAP_ANON
 116 /* This is only needed if the system doesn't support MAP_ANON.  */
 117
 118 int
 119 _dl_sysdep_open_zero_fill (void)
 120 {
 121   return __open ("/dev/zero", O_RDONLY);
 122 }
 123 #endif
 124
 125 /* Read the whole contents of FILE into new mmap'd space with given
 126    protections.  *SIZEP gets the size of the file.  */
 127
 128 void *
 129 _dl_sysdep_read_whole_file (const char *file, size_t *sizep, int prot)
 130 {
 131   void *result;
 132   struct stat st;
 133   int fd = __open (file, O_RDONLY);
 134   if (fd < 0)
 135     return NULL;
 136   if (__fstat (fd, &st) < 0)
 137     result = NULL;
 138   else
 139     {
 140       /* Map a copy of the file contents.  */
 141       result = __mmap (0, st.st_size, prot,
 142 #ifdef MAP_COPY
 143                        MAP_COPY
 144 #else
 145                        MAP_PRIVATE
 146 #endif
 147 #ifdef MAP_FILE
 148                        | MAP_FILE
 149 #endif
 150                        , fd, 0);
 151       if (result == (void *) -1)
 152         result = NULL;
 153       else
 154         *sizep = st.st_size;
 155     }
 156   __close (fd);
 157   return result;
 158 }
 159
 160 void
 161 _dl_sysdep_fatal (const char *msg, ...)
 162 {
 163   va_list ap;
 164
 165   va_start (ap, msg);
 166   do
 167     {
 168       size_t len = strlen (msg);
 169       __write (STDERR_FILENO, msg, len);
 170       msg = va_arg (ap, const char *);
 171     } while (msg);
 172   va_end (ap);
 173
 174   _exit (127);
 175 }
 176
 177
 178 void
 179 _dl_sysdep_message (const char *msg, ...)
 180 {
 181   va_list ap;
 182
 183   va_start (ap, msg);
 184   do
 185     {
 186       size_t len = strlen (msg);
 187       __write (STDOUT_FILENO, msg, len);
 188       msg = va_arg (ap, const char *);
 189     } while (msg);
 190   va_end (ap);
 191 }