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