elf/dl-minimal.c

   1 /* Minimal replacements for basic facilities used in the dynamic linker.
   2 Copyright (C) 1995, 1996 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 <sys/types.h>
  21 #include <sys/mman.h>
  22 #include <unistd.h>
  23 #include <assert.h>
  24 #include <string.h>
  25 #include <link.h>
  26 #include "../stdio-common/_itoa.h"
  27
  28 /* Minimal `malloc' allocator for use while loading shared libraries.
  29    Only small blocks are allocated, and none are ever freed.  */
  30
  31 static void *alloc_ptr, *alloc_end, *alloc_last_block;
  32
  33 void * weak_function
  34 malloc (size_t n)
  35 {
  36 #ifdef MAP_ANON
  37 #define _dl_zerofd (-1)
  38 #else
  39   extern int _dl_zerofd;
  40
  41   if (_dl_zerofd == -1)
  42     _dl_zerofd = _dl_sysdep_open_zero_fill ();
  43 #define MAP_ANON 0
  44 #endif
  45
  46   if (_dl_pagesize == 0)
  47     _dl_pagesize = __getpagesize ();
  48
  49   if (alloc_end == 0)
  50     {
  51       /* Consume any unused space in the last page of our data segment.  */
  52       extern int _end;
  53       alloc_ptr = &_end;
  54       alloc_end = (void *) 0 + (((alloc_ptr - (void *) 0) + _dl_pagesize - 1)
  55                                 & ~(_dl_pagesize - 1));
  56     }
  57
  58   /* Make sure the allocation pointer is ideally aligned.  */
  59   alloc_ptr = (void *) 0 + (((alloc_ptr - (void *) 0) + sizeof (double) - 1)
  60                             & ~(sizeof (double) - 1));
  61
  62   if (alloc_ptr + n >= alloc_end)
  63     {
  64       /* Insufficient space left; allocate another page.  */
  65       caddr_t page;
  66       assert (n <= _dl_pagesize);
  67       page = __mmap (0, _dl_pagesize, PROT_READ|PROT_WRITE,
  68                      MAP_ANON|MAP_PRIVATE, _dl_zerofd, 0);
  69       assert (page != (caddr_t) -1);
  70       if (page != alloc_end)
  71         alloc_ptr = page;
  72       alloc_end = page + _dl_pagesize;
  73     }
  74
  75   alloc_last_block = (void *) alloc_ptr;
  76   alloc_ptr += n;
  77   return alloc_last_block;
  78 }
  79
  80 /* This will rarely be called.  */
  81 void weak_function
  82 free (void *ptr)
  83 {
  84   /* We can free only the last block allocated.  */
  85   if (ptr == alloc_last_block)
  86     alloc_ptr = alloc_last_block;
  87 }
  88
  89 /* This is only called with the most recent block returned by malloc.  */
  90 void * weak_function
  91 realloc (void *ptr, size_t n)
  92 {
  93   void *new;
  94   assert (ptr == alloc_last_block);
  95   alloc_ptr = alloc_last_block;
  96   new = malloc (n);
  97   assert (new == ptr);
  98   return new;
  99 }
 100 \f
 101 /* Avoid signal frobnication in setjmp/longjmp.  Keeps things smaller.  */
 102
 103 #include <setjmp.h>
 104
 105 int weak_function
 106 __sigjmp_save (sigjmp_buf env, int savemask)
 107 { env[0].__mask_was_saved = savemask; return 0; }
 108
 109 void weak_function
 110 longjmp (jmp_buf env, int val) { __longjmp (env[0].__jmpbuf, val); }
 111 \f
 112 /* Define our own stub for the localization function used by strerror.
 113    English-only in the dynamic linker keeps it smaller.  */
 114
 115 char * weak_function
 116 __dgettext (const char *domainname, const char *msgid)
 117 {
 118   assert (domainname == _libc_intl_domainname);
 119   return (char *) msgid;
 120 }
 121 weak_alias (__dgettext, dgettext)
 122 \f
 123 #ifndef NDEBUG
 124
 125 /* Define (weakly) our own assert failure function which doesn't use stdio.
 126    If we are linked into the user program (-ldl), the normal __assert_fail
 127    defn can override this one.  */
 128
 129 void weak_function
 130 __assert_fail (const char *assertion,
 131                const char *file, unsigned int line, const char *function)
 132 {
 133   char buf[64];
 134   buf[sizeof buf - 1] = '\0';
 135   _dl_sysdep_fatal ("BUG IN DYNAMIC LINKER ld.so: ",
 136                     file, ": ", _itoa (line, buf + sizeof buf - 1, 10, 0),
 137                     ": ", function ?: "", function ? ": " : "",
 138                     "Assertion `", assertion, "' failed!\n",
 139                     NULL);
 140
 141 }
 142
 143 void weak_function
 144 __assert_perror_fail (int errnum,
 145                       const char *file, unsigned int line,
 146                       const char *function)
 147 {
 148   char buf[64];
 149   buf[sizeof buf - 1] = '\0';
 150   _dl_sysdep_fatal ("BUG IN DYNAMIC LINKER ld.so: ",
 151                     file, ": ", _itoa (line, buf + sizeof buf - 1, 10, 0),
 152                     ": ", function ?: "", function ? ": " : "",
 153                     "Unexpected error: ", strerror (errnum), "\n", NULL);
 154
 155 }
 156
 157 #endif