elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995, 1996, 1997, 1998, 1999 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 <stdlib.h>
  22 #include <unistd.h>
  23 #include <elf/ldsodefs.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 r_scope_elem *scope[],
  31                      int lazy, int consider_profiling)
  32 {
  33   if (l->l_relocated)
  34     return;
  35
  36   /* If DT_BIND_NOW is set relocate all references in this object.  We
  37      do not do this if we are profiling, of course.  */
  38   if (!consider_profiling && l->l_info[DT_BIND_NOW])
  39     lazy = 0;
  40
  41   if (_dl_debug_reloc)
  42     _dl_debug_message (1, "\nrelocation processing: ",
  43                        l->l_name[0] ? l->l_name : _dl_argv[0],
  44                        lazy ? " (lazy)\n" : "\n", NULL);
  45
  46   if (l->l_info[DT_TEXTREL])
  47     {
  48       /* Bletch.  We must make read-only segments writable
  49          long enough to relocate them.  */
  50       const ElfW(Phdr) *ph;
  51       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
  52         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
  53           {
  54             caddr_t mapstart = ((caddr_t) l->l_addr +
  55                                 (ph->p_vaddr & ~(_dl_pagesize - 1)));
  56             caddr_t mapend = ((caddr_t) l->l_addr +
  57                               ((ph->p_vaddr + ph->p_memsz + _dl_pagesize - 1)
  58                                & ~(_dl_pagesize - 1)));
  59             if (__mprotect (mapstart, mapend - mapstart,
  60                             PROT_READ|PROT_WRITE) < 0)
  61               _dl_signal_error (errno, l->l_name,
  62                                 "cannot make segment writable for relocation");
  63           }
  64     }
  65
  66   {
  67     /* Do the actual relocation of the object's GOT and other data.  */
  68
  69     /* String table object symbols.  */
  70     const char *strtab = (const void *) l->l_info[DT_STRTAB]->d_un.d_ptr;
  71
  72     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
  73 #define RESOLVE(ref, version, flags) \
  74     (ELFW(ST_VISIBILITY) ((*ref)->st_other) != STV_PROTECTED                  \
  75      ? ((version) != NULL && (version)->hash != 0                             \
  76         ? _dl_lookup_versioned_symbol (strtab + (*ref)->st_name, l, (ref),    \
  77                                        scope, (version), (flags))             \
  78         : _dl_lookup_symbol (strtab + (*ref)->st_name, l, (ref), scope,       \
  79                              (flags)))                                        \
  80      : l->l_addr)
  81
  82 #include "dynamic-link.h"
  83     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling);
  84
  85     if (_dl_profile != NULL)
  86       {
  87         /* Allocate the array which will contain the already found
  88            relocations.  */
  89         l->l_reloc_result =
  90           (ElfW(Addr) *) calloc (sizeof (ElfW(Addr)),
  91                                  l->l_info[DT_PLTRELSZ]->d_un.d_val);
  92         if (l->l_reloc_result == NULL)
  93           _dl_sysdep_fatal (_dl_argv[0] ?: "<program name unknown>",
  94                             "cannot allocate memory for profiling", NULL);
  95       }
  96   }
  97
  98   /* Mark the object so we know this work has been done.  */
  99   l->l_relocated = 1;
 100
 101   /* DT_TEXTREL is now in level 2 and might phase out at some time.
 102      But we rewrite the DT_FLAGS entry to make testing easier and
 103      therefore it will be available at all time.  */
 104   if (l->l_info[DT_TEXTREL])
 105     {
 106       /* Undo the protection change we made before relocating.  */
 107       const ElfW(Phdr) *ph;
 108       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
 109         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
 110           {
 111             caddr_t mapstart = ((caddr_t) l->l_addr +
 112                                 (ph->p_vaddr & ~(_dl_pagesize - 1)));
 113             caddr_t mapend = ((caddr_t) l->l_addr +
 114                               ((ph->p_vaddr + ph->p_memsz + _dl_pagesize - 1)
 115                                & ~(_dl_pagesize - 1)));
 116             extern unsigned char _dl_pf_to_prot[8];
 117             int prot;
 118
 119             if ((PF_R | PF_W | PF_X) == 7
 120                 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7)
 121               prot = _dl_pf_to_prot[ph->p_flags & (PF_R | PF_X)];
 122             else
 123               {
 124                 prot = 0;
 125                 if (ph->p_flags & PF_R)
 126                   prot |= PROT_READ;
 127                 if (ph->p_flags & PF_X)
 128                   prot |= PROT_EXEC;
 129               }
 130
 131             if (__mprotect (mapstart, mapend - mapstart, prot) < 0)
 132               _dl_signal_error (errno, l->l_name,
 133                                 "can't restore segment prot after reloc");
 134           }
 135     }
 136 }
 137
 138 #include "../stdio-common/_itoa.h"
 139 #define DIGIT(b)        _itoa_lower_digits[(b) & 0xf];
 140
 141 void
 142 internal_function
 143 _dl_reloc_bad_type (struct link_map *map, uint_fast8_t type, int plt)
 144 {
 145   extern const char _itoa_lower_digits[];
 146   if (plt)
 147     {
 148       char msg[] = "unexpected reloc type 0x??";
 149       msg[sizeof msg - 2] = DIGIT(type >> 8);
 150       msg[sizeof msg - 1] = DIGIT(type);
 151       _dl_signal_error (0, map->l_name, msg);
 152     }
 153   else
 154     {
 155       char msg[] = "unexpected PLT reloc type 0x??";
 156       msg[sizeof msg - 2] = DIGIT(type >> 8);
 157       msg[sizeof msg - 1] = DIGIT(type);
 158       _dl_signal_error (0, map->l_name, msg);
 159     }
 160 }