elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995,96,97,98,99,2000,2001 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 <libintl.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24 #include <ldsodefs.h>
  25 #include <sys/mman.h>
  26 #include <sys/types.h>
  27 #include "dynamic-link.h"
  28
  29
  30 void
  31 _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
  32                      int lazy, int consider_profiling)
  33 {
  34   if (l->l_relocated)
  35     return;
  36
  37   /* If DT_BIND_NOW is set relocate all references in this object.  We
  38      do not do this if we are profiling, of course.  */
  39   if (!consider_profiling
  40       && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
  41     lazy = 0;
  42
  43   if (__builtin_expect (_dl_debug_mask & DL_DEBUG_RELOC, 0))
  44     _dl_debug_message (1, "\nrelocation processing: ",
  45                        l->l_name[0] ? l->l_name : _dl_argv[0],
  46                        lazy ? " (lazy)\n" : "\n", NULL);
  47
  48   if (__builtin_expect (l->l_info[DT_TEXTREL] != NULL, 0))
  49     {
  50       /* Bletch.  We must make read-only segments writable
  51          long enough to relocate them.  */
  52       const ElfW(Phdr) *ph;
  53       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
  54         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
  55           {
  56             caddr_t mapstart = ((caddr_t) l->l_addr +
  57                                 (ph->p_vaddr & ~(_dl_pagesize - 1)));
  58             caddr_t mapend = ((caddr_t) l->l_addr +
  59                               ((ph->p_vaddr + ph->p_memsz + _dl_pagesize - 1)
  60                                & ~(_dl_pagesize - 1)));
  61             if (__builtin_expect (__mprotect (mapstart, mapend - mapstart,
  62                                               PROT_READ|PROT_WRITE), 0) < 0)
  63               _dl_signal_error (errno, l->l_name, N_("\
  64 cannot make segment writable for relocation"));
  65           }
  66     }
  67
  68   {
  69     /* Do the actual relocation of the object's GOT and other data.  */
  70
  71     /* String table object symbols.  */
  72     const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
  73
  74     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
  75 #define RESOLVE_MAP(ref, version, flags) \
  76     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
  77      ? ((version) != NULL && (version)->hash != 0                             \
  78         ? _dl_lookup_versioned_symbol (strtab + (*ref)->st_name, l, (ref),    \
  79                                        scope, (version), (flags), 0)          \
  80         : _dl_lookup_symbol (strtab + (*ref)->st_name, l, (ref), scope,       \
  81                              (flags), 0))                                     \
  82      : l)
  83 #define RESOLVE(ref, version, flags) \
  84     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
  85      ? ((version) != NULL && (version)->hash != 0                             \
  86         ? _dl_lookup_versioned_symbol (strtab + (*ref)->st_name, l, (ref),    \
  87                                        scope, (version), (flags), 0)          \
  88         : _dl_lookup_symbol (strtab + (*ref)->st_name, l, (ref), scope,       \
  89                              (flags), 0))                                     \
  90      : l->l_addr)
  91
  92 #include "dynamic-link.h"
  93     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling);
  94
  95     if (__builtin_expect (_dl_profile != NULL, 0))
  96       {
  97         /* Allocate the array which will contain the already found
  98            relocations.  If the shared object lacks a PLT (for example
  99            if it only contains lead function) the l_info[DT_PLTRELSZ]
 100            will be NULL.  */
 101         if (l->l_info[DT_PLTRELSZ] == NULL)
 102           _dl_sysdep_fatal (_dl_argv[0] ?: "<program name unknown>",
 103                             ": profiler found no PLTREL in object ",
 104                             l->l_name, "\n", NULL);
 105
 106         l->l_reloc_result =
 107           (ElfW(Addr) *) calloc (sizeof (ElfW(Addr)),
 108                                  l->l_info[DT_PLTRELSZ]->d_un.d_val);
 109         if (l->l_reloc_result == NULL)
 110           _dl_sysdep_fatal (_dl_argv[0] ?: "<program name unknown>",
 111                             ": profiler out of memory shadowing PLTREL of ",
 112                             l->l_name, "\n", NULL);
 113       }
 114   }
 115
 116   /* Mark the object so we know this work has been done.  */
 117   l->l_relocated = 1;
 118
 119   /* DT_TEXTREL is now in level 2 and might phase out at some time.
 120      But we rewrite the DT_FLAGS entry to make testing easier and
 121      therefore it will be available at all time.  */
 122   if (__builtin_expect (l->l_info[DT_TEXTREL] != NULL, 0))
 123     {
 124       /* Undo the protection change we made before relocating.  */
 125       const ElfW(Phdr) *ph;
 126       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
 127         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
 128           {
 129             caddr_t mapstart = ((caddr_t) l->l_addr +
 130                                 (ph->p_vaddr & ~(_dl_pagesize - 1)));
 131             caddr_t mapend = ((caddr_t) l->l_addr +
 132                               ((ph->p_vaddr + ph->p_memsz + _dl_pagesize - 1)
 133                                & ~(_dl_pagesize - 1)));
 134             extern unsigned char _dl_pf_to_prot[8];
 135             int prot;
 136
 137             if ((PF_R | PF_W | PF_X) == 7
 138                 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7)
 139               prot = _dl_pf_to_prot[ph->p_flags & (PF_R | PF_X)];
 140             else
 141               {
 142                 prot = 0;
 143                 if (ph->p_flags & PF_R)
 144                   prot |= PROT_READ;
 145                 if (ph->p_flags & PF_X)
 146                   prot |= PROT_EXEC;
 147               }
 148
 149             if (__builtin_expect (__mprotect (mapstart, mapend - mapstart,
 150                                               prot), 0) < 0)
 151               _dl_signal_error (errno, l->l_name,
 152                                 N_("can't restore segment prot after reloc"));
 153
 154 #ifdef CLEAR_CACHE
 155             CLEAR_CACHE (mapstart, mapend);
 156 #endif
 157           }
 158     }
 159 }
 160
 161 #include "../stdio-common/_itoa.h"
 162 #define DIGIT(b)        _itoa_lower_digits[(b) & 0xf];
 163
 164 void
 165 internal_function
 166 _dl_reloc_bad_type (struct link_map *map, uint_fast8_t type, int plt)
 167 {
 168   extern const char _itoa_lower_digits[];
 169   if (plt)
 170     {
 171       /* XXX We cannot translate the message.  */
 172       static char msg[] = "unexpected PLT reloc type 0x??";
 173       msg[sizeof msg - 3] = DIGIT(type >> 4);
 174       msg[sizeof msg - 2] = DIGIT(type);
 175       _dl_signal_error (0, map->l_name, msg);
 176     }
 177   else
 178     {
 179       /* XXX We cannot translate the message.  */
 180       static char msg[] = "unexpected reloc type 0x??";
 181       msg[sizeof msg - 3] = DIGIT(type >> 4);
 182       msg[sizeof msg - 2] = DIGIT(type);
 183       _dl_signal_error (0, map->l_name, msg);
 184     }
 185 }