elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995-2006, 2008, 2009, 2010 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 /* We are trying to perform a static TLS relocation in MAP, but it was
  39    dynamically loaded.  This can only work if there is enough surplus in
  40    the static TLS area already allocated for each running thread.  If this
  41    object's TLS segment is too big to fit, we fail.  If it fits,
  42    we set MAP->l_tls_offset and return.
  43    This function intentionally does not return any value but signals error
  44    directly, as static TLS should be rare and code handling it should
  45    not be inlined as much as possible.  */
  46 int
  47 internal_function
  48 _dl_try_allocate_static_tls (struct link_map *map)
  49 {
  50   /* If we've already used the variable with dynamic access, or if the
  51      alignment requirements are too high, fail.  */
  52   if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
  53       || map->l_tls_align > GL(dl_tls_static_align))
  54     {
  55     fail:
  56       return -1;
  57     }
  58
  59 #if TLS_TCB_AT_TP
  60   size_t freebytes;
  61   size_t n;
  62   size_t blsize;
  63
  64   freebytes = GL(dl_tls_static_size) - GL(dl_tls_static_used);
  65   if (freebytes < TLS_TCB_SIZE)
  66     goto fail;
  67   freebytes -= TLS_TCB_SIZE;
  68
  69   blsize = map->l_tls_blocksize + map->l_tls_firstbyte_offset;
  70   if (freebytes < blsize)
  71     goto fail;
  72
  73   n = (freebytes - blsize) / map->l_tls_align;
  74
  75   size_t offset = GL(dl_tls_static_used) + (freebytes - n * map->l_tls_align
  76                                             - map->l_tls_firstbyte_offset);
  77
  78   map->l_tls_offset = GL(dl_tls_static_used) = offset;
  79 #elif TLS_DTV_AT_TP
  80   size_t used;
  81   size_t check;
  82
  83   size_t offset = roundup (GL(dl_tls_static_used), map->l_tls_align);
  84   used = offset + map->l_tls_blocksize;
  85   check = used;
  86   /* dl_tls_static_used includes the TCB at the beginning.  */
  87
  88   if (check > GL(dl_tls_static_size))
  89     goto fail;
  90
  91   map->l_tls_offset = offset;
  92   GL(dl_tls_static_used) = used;
  93 #else
  94 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
  95 #endif
  96
  97   /* If the object is not yet relocated we cannot initialize the
  98      static TLS region.  Delay it.  */
  99   if (map->l_real->l_relocated)
 100     {
 101 #ifdef SHARED
 102       if (__builtin_expect (THREAD_DTV()[0].counter != GL(dl_tls_generation),
 103                             0))
 104         /* Update the slot information data for at least the generation of
 105            the DSO we are allocating data for.  */
 106         (void) _dl_update_slotinfo (map->l_tls_modid);
 107 #endif
 108
 109       GL(dl_init_static_tls) (map);
 110     }
 111   else
 112     map->l_need_tls_init = 1;
 113
 114   return 0;
 115 }
 116
 117 void
 118 internal_function __attribute_noinline__
 119 _dl_allocate_static_tls (struct link_map *map)
 120 {
 121   if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
 122       || _dl_try_allocate_static_tls (map))
 123     {
 124       _dl_signal_error (0, map->l_name, NULL, N_("\
 125 cannot allocate memory in static TLS block"));
 126     }
 127 }
 128
 129 /* Initialize static TLS area and DTV for current (only) thread.
 130    libpthread implementations should provide their own hook
 131    to handle all threads.  */
 132 void
 133 _dl_nothread_init_static_tls (struct link_map *map)
 134 {
 135 #if TLS_TCB_AT_TP
 136   void *dest = (char *) THREAD_SELF - map->l_tls_offset;
 137 #elif TLS_DTV_AT_TP
 138   void *dest = (char *) THREAD_SELF + map->l_tls_offset + TLS_PRE_TCB_SIZE;
 139 #else
 140 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 141 #endif
 142
 143   /* Fill in the DTV slot so that a later LD/GD access will find it.  */
 144   dtv_t *dtv = THREAD_DTV ();
 145   assert (map->l_tls_modid <= dtv[-1].counter);
 146   dtv[map->l_tls_modid].pointer.val = dest;
 147   dtv[map->l_tls_modid].pointer.is_static = true;
 148
 149   /* Initialize the memory.  */
 150   memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
 151           '\0', map->l_tls_blocksize - map->l_tls_initimage_size);
 152 }
 153
 154
 155 void
 156 _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
 157                      int reloc_mode, int consider_profiling)
 158 {
 159   struct textrels
 160   {
 161     caddr_t start;
 162     size_t len;
 163     int prot;
 164     struct textrels *next;
 165   } *textrels = NULL;
 166   /* Initialize it to make the compiler happy.  */
 167   const char *errstring = NULL;
 168   int lazy = reloc_mode & RTLD_LAZY;
 169
 170 #ifdef SHARED
 171   /* If we are auditing, install the same handlers we need for profiling.  */
 172   if ((reloc_mode & __RTLD_AUDIT) == 0)
 173     consider_profiling |= GLRO(dl_audit) != NULL;
 174 #elif defined PROF
 175   /* Never use dynamic linker profiling for gprof profiling code.  */
 176 # define consider_profiling 0
 177 #endif
 178
 179   if (l->l_relocated)
 180     return;
 181
 182   /* If DT_BIND_NOW is set relocate all references in this object.  We
 183      do not do this if we are profiling, of course.  */
 184   // XXX Correct for auditing?
 185   if (!consider_profiling
 186       && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
 187     lazy = 0;
 188
 189   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_RELOC, 0))
 190     _dl_debug_printf ("\nrelocation processing: %s%s\n",
 191                       l->l_name[0] ? l->l_name : rtld_progname,
 192                       lazy ? " (lazy)" : "");
 193
 194   /* DT_TEXTREL is now in level 2 and might phase out at some time.
 195      But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
 196      testing easier and therefore it will be available at all time.  */
 197   if (__builtin_expect (l->l_info[DT_TEXTREL] != NULL, 0))
 198     {
 199       /* Bletch.  We must make read-only segments writable
 200          long enough to relocate them.  */
 201       const ElfW(Phdr) *ph;
 202       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
 203         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
 204           {
 205             struct textrels *newp;
 206
 207             newp = (struct textrels *) alloca (sizeof (*newp));
 208             newp->len = (((ph->p_vaddr + ph->p_memsz + GLRO(dl_pagesize) - 1)
 209                           & ~(GLRO(dl_pagesize) - 1))
 210                          - (ph->p_vaddr & ~(GLRO(dl_pagesize) - 1)));
 211             newp->start = ((ph->p_vaddr & ~(GLRO(dl_pagesize) - 1))
 212                            + (caddr_t) l->l_addr);
 213
 214             if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
 215               {
 216                 errstring = N_("cannot make segment writable for relocation");
 217               call_error:
 218                 _dl_signal_error (errno, l->l_name, NULL, errstring);
 219               }
 220
 221 #if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
 222             newp->prot = (PF_TO_PROT
 223                           >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
 224 #else
 225             newp->prot = 0;
 226             if (ph->p_flags & PF_R)
 227               newp->prot |= PROT_READ;
 228             if (ph->p_flags & PF_W)
 229               newp->prot |= PROT_WRITE;
 230             if (ph->p_flags & PF_X)
 231               newp->prot |= PROT_EXEC;
 232 #endif
 233             newp->next = textrels;
 234             textrels = newp;
 235           }
 236     }
 237
 238   {
 239     /* Do the actual relocation of the object's GOT and other data.  */
 240
 241     /* String table object symbols.  */
 242     const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
 243
 244     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
 245 #define RESOLVE_MAP(ref, version, r_type) \
 246     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 247      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 248          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 249         ? (bump_num_cache_relocations (),                                     \
 250            (*ref) = l->l_lookup_cache.ret,                                    \
 251            l->l_lookup_cache.value)                                           \
 252         : ({ lookup_t _lr;                                                    \
 253              int _tc = elf_machine_type_class (r_type);                       \
 254              l->l_lookup_cache.type_class = _tc;                              \
 255              l->l_lookup_cache.sym = (*ref);                                  \
 256              const struct r_found_version *v = NULL;                          \
 257              if ((version) != NULL && (version)->hash != 0)                   \
 258                v = (version);                                                 \
 259              _lr = _dl_lookup_symbol_x (strtab + (*ref)->st_name, l, (ref),   \
 260                                         scope, v, _tc,                        \
 261                                         DL_LOOKUP_ADD_DEPENDENCY, NULL);      \
 262              l->l_lookup_cache.ret = (*ref);                                  \
 263              l->l_lookup_cache.value = _lr; }))                               \
 264      : l)
 265
 266 #include "dynamic-link.h"
 267
 268     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling);
 269
 270 #ifndef PROF
 271     if (__builtin_expect (consider_profiling, 0))
 272       {
 273         /* Allocate the array which will contain the already found
 274            relocations.  If the shared object lacks a PLT (for example
 275            if it only contains lead function) the l_info[DT_PLTRELSZ]
 276            will be NULL.  */
 277         if (l->l_info[DT_PLTRELSZ] == NULL)
 278           {
 279             errstring = N_("%s: no PLTREL found in object %s\n");
 280           fatal:
 281             _dl_fatal_printf (errstring,
 282                               rtld_progname ?: "<program name unknown>",
 283                               l->l_name);
 284           }
 285
 286         l->l_reloc_result = calloc (sizeof (l->l_reloc_result[0]),
 287                                     l->l_info[DT_PLTRELSZ]->d_un.d_val);
 288         if (l->l_reloc_result == NULL)
 289           {
 290             errstring = N_("\
 291 %s: out of memory to store relocation results for %s\n");
 292             goto fatal;
 293           }
 294       }
 295 #endif
 296   }
 297
 298   /* Mark the object so we know this work has been done.  */
 299   l->l_relocated = 1;
 300
 301   /* Undo the segment protection changes.  */
 302   while (__builtin_expect (textrels != NULL, 0))
 303     {
 304       if (__mprotect (textrels->start, textrels->len, textrels->prot) < 0)
 305         {
 306           errstring = N_("cannot restore segment prot after reloc");
 307           goto call_error;
 308         }
 309
 310 #ifdef CLEAR_CACHE
 311       CLEAR_CACHE (textrels->start, textrels->start + textrels->len);
 312 #endif
 313
 314       textrels = textrels->next;
 315     }
 316
 317   /* In case we can protect the data now that the relocations are
 318      done, do it.  */
 319   if (l->l_relro_size != 0)
 320     _dl_protect_relro (l);
 321 }
 322
 323
 324 void internal_function
 325 _dl_protect_relro (struct link_map *l)
 326 {
 327   ElfW(Addr) start = ((l->l_addr + l->l_relro_addr)
 328                       & ~(GLRO(dl_pagesize) - 1));
 329   ElfW(Addr) end = ((l->l_addr + l->l_relro_addr + l->l_relro_size)
 330                     & ~(GLRO(dl_pagesize) - 1));
 331
 332   if (start != end
 333       && __mprotect ((void *) start, end - start, PROT_READ) < 0)
 334     {
 335       static const char errstring[] = N_("\
 336 cannot apply additional memory protection after relocation");
 337       _dl_signal_error (errno, l->l_name, NULL, errstring);
 338     }
 339 }
 340
 341 void
 342 internal_function __attribute_noinline__
 343 _dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
 344 {
 345   extern const char INTUSE(_itoa_lower_digits)[] attribute_hidden;
 346 #define DIGIT(b)        INTUSE(_itoa_lower_digits)[(b) & 0xf];
 347
 348   /* XXX We cannot translate these messages.  */
 349   static const char msg[2][32
 350 #if __ELF_NATIVE_CLASS == 64
 351                            + 6
 352 #endif
 353   ] = { "unexpected reloc type 0x",
 354         "unexpected PLT reloc type 0x" };
 355   char msgbuf[sizeof (msg[0])];
 356   char *cp;
 357
 358   cp = __stpcpy (msgbuf, msg[plt]);
 359 #if __ELF_NATIVE_CLASS == 64
 360   if (__builtin_expect(type > 0xff, 0))
 361     {
 362       *cp++ = DIGIT (type >> 28);
 363       *cp++ = DIGIT (type >> 24);
 364       *cp++ = DIGIT (type >> 20);
 365       *cp++ = DIGIT (type >> 16);
 366       *cp++ = DIGIT (type >> 12);
 367       *cp++ = DIGIT (type >> 8);
 368     }
 369 #endif
 370   *cp++ = DIGIT (type >> 4);
 371   *cp++ = DIGIT (type);
 372   *cp = '\0';
 373
 374   _dl_signal_error (0, map->l_name, NULL, msgbuf);
 375 }