elf/dl-minimal.c

   1 /* Minimal replacements for basic facilities used in the dynamic linker.
   2 Copyright (C) 1995 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 *
  34 malloc (size_t n)
  35 {
  36   extern int _dl_zerofd;
  37   static size_t pagesize;
  38
  39   if (pagesize == 0)
  40     pagesize = __getpagesize ();
  41
  42   if (_dl_zerofd == -1)
  43     _dl_zerofd = _dl_sysdep_open_zero_fill ();
  44
  45   if (alloc_end == 0)
  46     {
  47       /* Consume any unused space in the last page of our data segment.  */
  48       extern int _end;
  49       alloc_ptr = &_end;
  50       alloc_end = (void *) 0 + (((alloc_ptr - (void *) 0) + pagesize - 1)
  51                                 & ~(pagesize - 1));
  52     }
  53
  54   /* Make sure the allocation pointer is ideally aligned.  */
  55   alloc_ptr = (void *) 0 + (((alloc_ptr - (void *) 0) + sizeof (double) - 1)
  56                             & ~(sizeof (double) - 1));
  57
  58   if (alloc_ptr + n >= alloc_end)
  59     {
  60       /* Insufficient space left; allocate another page.  */
  61       caddr_t page;
  62       assert (n <= pagesize);
  63       page = mmap (0, pagesize, PROT_READ|PROT_WRITE,
  64                    MAP_ANON|MAP_PRIVATE, _dl_zerofd, 0);
  65       assert (page != (caddr_t) -1);
  66       if (page != alloc_end)
  67         alloc_ptr = page;
  68       alloc_end = page + pagesize;
  69     }
  70
  71   alloc_last_block = (void *) alloc_ptr;
  72   alloc_ptr += n;
  73   return alloc_last_block;
  74 }
  75 weak_symbol (malloc)
  76
  77 /* This will rarely be called.  */
  78 void
  79 free (void *ptr)
  80 {
  81   /* We can free only the last block allocated.  */
  82   if (ptr == alloc_last_block)
  83     alloc_ptr = alloc_last_block;
  84 }
  85 weak_symbol (free)
  86
  87 /* This is never called.  */
  88 void *
  89 realloc (void *ptr, size_t n)
  90 { ptr += n; abort (); }
  91 weak_symbol (realloc)
  92 \f
  93 /* Avoid signal frobnication in setjmp/longjmp.  Keeps things smaller.  */
  94
  95 #include <setjmp.h>
  96
  97 int __sigjmp_save (sigjmp_buf env, int savemask)
  98 { env[0].__mask_was_saved = savemask; return 0; }
  99 weak_symbol (__sigjmp_save)
 100
 101 void
 102 longjmp (jmp_buf env, int val) { __longjmp (env[0].__jmpbuf, val); }
 103 weak_symbol (longjmp)
 104
 105 \f
 106 /* Define our own stub for the localization function used by strerror.
 107    English-only in the dynamic linker keeps it smaller.  */
 108
 109 char *
 110 __dgettext (const char *domainname, const char *msgid)
 111 {
 112   assert (domainname == _libc_intl_domainname);
 113   return (char *) msgid;
 114 }
 115 weak_symbol (__dgettext)
 116 weak_alias (__dgettext, dgettext)
 117 \f
 118 #ifndef NDEBUG
 119
 120 /* Define (weakly) our own assert failure function which doesn't use stdio.
 121    If we are linked into the user program (-ldl), the normal __assert_fail
 122    defn can override this one.  */
 123
 124 void
 125 __assert_fail (const char *assertion,
 126                const char *file, unsigned int line, const char *function)
 127 {
 128   char buf[64];
 129   buf[sizeof buf - 1] = '\0';
 130   _dl_sysdep_fatal ("BUG IN DYNAMIC LINKER ld.so: ",
 131                     file, ": ", _itoa (line, buf + sizeof buf - 1, 10, 0),
 132                     ": ", function ?: "", function ? ": " : "",
 133                     "Assertion `", assertion, "' failed!\n",
 134                     NULL);
 135
 136 }
 137 weak_symbol (__assert_fail)
 138
 139 void
 140 __assert_perror_fail (int errnum,
 141                       const char *file, unsigned int line,
 142                       const char *function)
 143 {
 144   char buf[64];
 145   buf[sizeof buf - 1] = '\0';
 146   _dl_sysdep_fatal ("BUG IN DYNAMIC LINKER ld.so: ",
 147                     file, ": ", _itoa (line, buf + sizeof buf - 1, 10, 0),
 148                     ": ", function ?: "", function ? ": " : "",
 149                     "Unexpected error: ", strerror (errnum), "\n", NULL);
 150
 151 }
 152 weak_symbol (__assert_perror_fail)
 153
 154 #endif