elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995, 1996, 1997, 1998 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 not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <link.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24 #include <sys/mman.h>
  25 #include <sys/types.h>
  26 #include "dynamic-link.h"
  27
  28
  29 void
  30 _dl_relocate_object (struct link_map *l, struct link_map *scope[], int lazy)
  31 {
  32   if (l->l_relocated)
  33     return;
  34
  35   if (_dl_debug_reloc)
  36     _dl_debug_message (1, "\nrelocation processing: ",
  37                        l->l_name[0] ? l->l_name : _dl_argv[0], "\n", NULL);
  38
  39   if (l->l_info[DT_TEXTREL])
  40     {
  41       /* Bletch.  We must make read-only segments writable
  42          long enough to relocate them.  */
  43       const ElfW(Phdr) *ph;
  44       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
  45         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
  46           {
  47             caddr_t mapstart = ((caddr_t) l->l_addr +
  48                                 (ph->p_vaddr & ~(_dl_pagesize - 1)));
  49             caddr_t mapend = ((caddr_t) l->l_addr +
  50                               ((ph->p_vaddr + ph->p_memsz + _dl_pagesize - 1)
  51                                & ~(_dl_pagesize - 1)));
  52             if (__mprotect (mapstart, mapend - mapstart,
  53                             PROT_READ|PROT_WRITE) < 0)
  54               _dl_signal_error (errno, l->l_name,
  55                                 "cannot make segment writable for relocation");
  56           }
  57     }
  58
  59   {
  60     /* Do the actual relocation of the object's GOT and other data.  */
  61
  62     const char *strtab          /* String table object symbols.  */
  63       = ((void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr);
  64
  65     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
  66 #define RESOLVE(ref, version, flags) \
  67     ((version) != NULL && (version)->hash != 0                                \
  68      ? _dl_lookup_versioned_symbol (strtab + (*ref)->st_name, (ref), scope,   \
  69                                     l->l_name, (version), (flags))            \
  70      : _dl_lookup_symbol (strtab + (*ref)->st_name, (ref), scope,             \
  71                           l->l_name, (flags)))
  72
  73 #include "dynamic-link.h"
  74     ELF_DYNAMIC_RELOCATE (l, lazy, 1);
  75
  76     if (_dl_profile_map == l)
  77       {
  78         /* Allocate the array which will contain the already found
  79            relocations.  */
  80         l->l_reloc_result =
  81           (ElfW(Addr) *) calloc (sizeof (ElfW(Addr)),
  82                                  l->l_info[DT_PLTRELSZ]->d_un.d_val);
  83         if (l->l_reloc_result == NULL)
  84           _dl_sysdep_fatal (_dl_argv[0] ?: "<program name unknown>",
  85                             "cannot allocate memory for profiling", NULL);
  86       }
  87   }
  88
  89   /* Mark the object so we know this work has been done.  */
  90   l->l_relocated = 1;
  91
  92   if (l->l_info[DT_TEXTREL])
  93     {
  94       /* Undo the protection change we made before relocating.  */
  95       const ElfW(Phdr) *ph;
  96       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
  97         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
  98           {
  99             caddr_t mapstart = ((caddr_t) l->l_addr +
 100                                 (ph->p_vaddr & ~(_dl_pagesize - 1)));
 101             caddr_t mapend = ((caddr_t) l->l_addr +
 102                               ((ph->p_vaddr + ph->p_memsz + _dl_pagesize - 1)
 103                                & ~(_dl_pagesize - 1)));
 104             int prot = 0;
 105             if (ph->p_flags & PF_R)
 106               prot |= PROT_READ;
 107             if (ph->p_flags & PF_X)
 108               prot |= PROT_EXEC;
 109             if (__mprotect (mapstart, mapend - mapstart, prot) < 0)
 110               _dl_signal_error (errno, l->l_name,
 111                                 "can't restore segment prot after reloc");
 112           }
 113     }
 114 }