elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995,96,97,98,99,2000,2001,2002 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    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/param.h>
  27 #include <sys/types.h>
  28 #include "dynamic-link.h"
  29
  30 /* Statistics function.  */
  31 #ifdef SHARED
  32 # define bump_num_cache_relocations() ++GL(dl_num_cache_relocations)
  33 #else
  34 # define bump_num_cache_relocations() ((void) 0)
  35 #endif
  36
  37
  38 void
  39 _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
  40                      int lazy, int consider_profiling)
  41 {
  42   struct textrels
  43   {
  44     caddr_t start;
  45     size_t len;
  46     int prot;
  47     struct textrels *next;
  48   } *textrels = NULL;
  49   /* Initialize it to make the compiler happy.  */
  50   const char *errstring = NULL;
  51
  52   if (l->l_relocated)
  53     return;
  54
  55   /* If DT_BIND_NOW is set relocate all references in this object.  We
  56      do not do this if we are profiling, of course.  */
  57   if (!consider_profiling
  58       && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
  59     lazy = 0;
  60
  61   if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_RELOC, 0))
  62     INTUSE(_dl_debug_printf) ("\nrelocation processing: %s%s\n",
  63                               l->l_name[0] ? l->l_name : _dl_argv[0],
  64                               lazy ? " (lazy)" : "");
  65
  66   /* DT_TEXTREL is now in level 2 and might phase out at some time.
  67      But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
  68      testing easier and therefore it will be available at all time.  */
  69   if (__builtin_expect (l->l_info[DT_TEXTREL] != NULL, 0))
  70     {
  71       /* Bletch.  We must make read-only segments writable
  72          long enough to relocate them.  */
  73       const ElfW(Phdr) *ph;
  74       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
  75         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
  76           {
  77             struct textrels *newp;
  78
  79             newp = (struct textrels *) alloca (sizeof (*newp));
  80             newp->len = (((ph->p_vaddr + ph->p_memsz + GL(dl_pagesize) - 1)
  81                           & ~(GL(dl_pagesize) - 1))
  82                          - (ph->p_vaddr & ~(GL(dl_pagesize) - 1)));
  83             newp->start = ((ph->p_vaddr & ~(GL(dl_pagesize) - 1))
  84                            + (caddr_t) l->l_addr);
  85
  86             if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
  87               {
  88                 errstring = N_("cannot make segment writable for relocation");
  89               call_error:
  90                 INTUSE(_dl_signal_error) (errno, l->l_name, NULL, errstring);
  91               }
  92
  93 #if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
  94             newp->prot = (PF_TO_PROT
  95                           >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
  96 #else
  97             newp->prot = 0;
  98             if (ph->p_flags & PF_R)
  99               newp->prot |= PROT_READ;
 100             if (ph->p_flags & PF_W)
 101               newp->prot |= PROT_WRITE;
 102             if (ph->p_flags & PF_X)
 103               newp->prot |= PROT_EXEC;
 104 #endif
 105             newp->next = textrels;
 106             textrels = newp;
 107           }
 108     }
 109
 110   {
 111     /* Do the actual relocation of the object's GOT and other data.  */
 112
 113     /* String table object symbols.  */
 114     const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
 115
 116     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
 117 #define RESOLVE_MAP(ref, version, r_type) \
 118     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 119      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 120          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 121         ? (bump_num_cache_relocations (),                                     \
 122            (*ref) = l->l_lookup_cache.ret,                                    \
 123            l->l_lookup_cache.value)                                           \
 124         : ({ lookup_t _lr;                                                    \
 125              int _tc = elf_machine_type_class (r_type);                       \
 126              l->l_lookup_cache.type_class = _tc;                              \
 127              l->l_lookup_cache.sym = (*ref);                                  \
 128              _lr = ((version) != NULL && (version)->hash != 0                 \
 129                     ? INTUSE(_dl_lookup_versioned_symbol) (strtab             \
 130                                                            + (*ref)->st_name, \
 131                                                            l, (ref), scope,   \
 132                                                            (version), _tc, 0) \
 133                     : INTUSE(_dl_lookup_symbol) (strtab + (*ref)->st_name, l, \
 134                                                  (ref), scope, _tc, 0));      \
 135              l->l_lookup_cache.ret = (*ref);                                  \
 136              l->l_lookup_cache.value = _lr; }))                               \
 137      : l)
 138 #define RESOLVE(ref, version, r_type) \
 139     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 140      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 141          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 142                 ? (bump_num_cache_relocations (),                             \
 143            (*ref) = l->l_lookup_cache.ret,                                    \
 144            l->l_lookup_cache.value)                                           \
 145         : ({ lookup_t _lr;                                                    \
 146              int _tc = elf_machine_type_class (r_type);                       \
 147              l->l_lookup_cache.type_class = _tc;                              \
 148              l->l_lookup_cache.sym = (*ref);                                  \
 149              _lr = ((version) != NULL && (version)->hash != 0                 \
 150                     ? INTUSE(_dl_lookup_versioned_symbol) (strtab             \
 151                                                            + (*ref)->st_name, \
 152                                                            l, (ref), scope,   \
 153                                                            (version), _tc, 0) \
 154                     : INTUSE(_dl_lookup_symbol) (strtab + (*ref)->st_name, l, \
 155                                                  (ref), scope, _tc, 0));      \
 156              l->l_lookup_cache.ret = (*ref);                                  \
 157              l->l_lookup_cache.value = _lr; }))                               \
 158      : l->l_addr)
 159
 160 #include "dynamic-link.h"
 161
 162     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling);
 163
 164     if (__builtin_expect (consider_profiling, 0))
 165       {
 166         /* Allocate the array which will contain the already found
 167            relocations.  If the shared object lacks a PLT (for example
 168            if it only contains lead function) the l_info[DT_PLTRELSZ]
 169            will be NULL.  */
 170         if (l->l_info[DT_PLTRELSZ] == NULL)
 171           {
 172             errstring = N_("%s: profiler found no PLTREL in object %s\n");
 173           fatal:
 174             _dl_fatal_printf (errstring,
 175                               _dl_argv[0] ?: "<program name unknown>",
 176                               l->l_name);
 177           }
 178
 179         l->l_reloc_result =
 180           (ElfW(Addr) *) calloc (sizeof (ElfW(Addr)),
 181                                  l->l_info[DT_PLTRELSZ]->d_un.d_val);
 182         if (l->l_reloc_result == NULL)
 183           {
 184             errstring = N_("\
 185 %s: profiler out of memory shadowing PLTREL of %s\n");
 186             goto fatal;
 187           }
 188       }
 189   }
 190
 191   /* Mark the object so we know this work has been done.  */
 192   l->l_relocated = 1;
 193
 194   /* Undo the segment protection changes.  */
 195   while (__builtin_expect (textrels != NULL, 0))
 196     {
 197       if (__mprotect (textrels->start, textrels->len, textrels->prot) < 0)
 198         {
 199           errstring = N_("cannot restore segment prot after reloc");
 200           goto call_error;
 201         }
 202
 203       textrels = textrels->next;
 204     }
 205 }
 206 INTDEF (_dl_relocate_object)
 207
 208
 209 void
 210 internal_function
 211 _dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
 212 {
 213   extern const char _itoa_lower_digits[];
 214 #define DIGIT(b)        _itoa_lower_digits[(b) & 0xf];
 215
 216   /* XXX We cannot translate these messages.  */
 217   static const char msg[2][32] = { "unexpected reloc type 0x",
 218                                    "unexpected PLT reloc type 0x" };
 219   char msgbuf[sizeof (msg[0])];
 220   char *cp;
 221
 222   cp = __stpcpy (msgbuf, msg[plt]);
 223   *cp++ = DIGIT (type >> 4);
 224   *cp = DIGIT (type);
 225
 226   INTUSE(_dl_signal_error) (0, map->l_name, NULL, msgbuf);
 227 }