elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995-2014 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <libintl.h>
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <ldsodefs.h>
  24 #include <sys/mman.h>
  25 #include <sys/param.h>
  26 #include <sys/types.h>
  27 #include <_itoa.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 = GL(dl_tls_static_size) - GL(dl_tls_static_used);
  61   if (freebytes < TLS_TCB_SIZE)
  62     goto fail;
  63   freebytes -= TLS_TCB_SIZE;
  64
  65   size_t blsize = map->l_tls_blocksize + map->l_tls_firstbyte_offset;
  66   if (freebytes < blsize)
  67     goto fail;
  68
  69   size_t n = (freebytes - blsize) / map->l_tls_align;
  70
  71   size_t offset = GL(dl_tls_static_used) + (freebytes - n * map->l_tls_align
  72                                             - map->l_tls_firstbyte_offset);
  73
  74   map->l_tls_offset = GL(dl_tls_static_used) = offset;
  75 #elif TLS_DTV_AT_TP
  76   /* dl_tls_static_used includes the TCB at the beginning.  */
  77   size_t offset = (((GL(dl_tls_static_used)
  78                      - map->l_tls_firstbyte_offset
  79                      + map->l_tls_align - 1) & -map->l_tls_align)
  80                    + map->l_tls_firstbyte_offset);
  81   size_t used = offset + map->l_tls_blocksize;
  82
  83   if (used > GL(dl_tls_static_size))
  84     goto fail;
  85
  86   map->l_tls_offset = offset;
  87   map->l_tls_firstbyte_offset = GL(dl_tls_static_used);
  88   GL(dl_tls_static_used) = used;
  89 #else
  90 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
  91 #endif
  92
  93   /* If the object is not yet relocated we cannot initialize the
  94      static TLS region.  Delay it.  */
  95   if (map->l_real->l_relocated)
  96     {
  97 #ifdef SHARED
  98       if (__builtin_expect (THREAD_DTV()[0].counter != GL(dl_tls_generation),
  99                             0))
 100         /* Update the slot information data for at least the generation of
 101            the DSO we are allocating data for.  */
 102         (void) _dl_update_slotinfo (map->l_tls_modid);
 103 #endif
 104
 105       GL(dl_init_static_tls) (map);
 106     }
 107   else
 108     map->l_need_tls_init = 1;
 109
 110   return 0;
 111 }
 112
 113 void
 114 internal_function __attribute_noinline__
 115 _dl_allocate_static_tls (struct link_map *map)
 116 {
 117   if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
 118       || _dl_try_allocate_static_tls (map))
 119     {
 120       _dl_signal_error (0, map->l_name, NULL, N_("\
 121 cannot allocate memory in static TLS block"));
 122     }
 123 }
 124
 125 /* Initialize static TLS area and DTV for current (only) thread.
 126    libpthread implementations should provide their own hook
 127    to handle all threads.  */
 128 void
 129 _dl_nothread_init_static_tls (struct link_map *map)
 130 {
 131 #if TLS_TCB_AT_TP
 132   void *dest = (char *) THREAD_SELF - map->l_tls_offset;
 133 #elif TLS_DTV_AT_TP
 134   void *dest = (char *) THREAD_SELF + map->l_tls_offset + TLS_PRE_TCB_SIZE;
 135 #else
 136 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 137 #endif
 138
 139   /* Fill in the DTV slot so that a later LD/GD access will find it.  */
 140   dtv_t *dtv = THREAD_DTV ();
 141   assert (map->l_tls_modid <= dtv[-1].counter);
 142   dtv[map->l_tls_modid].pointer.val = dest;
 143   dtv[map->l_tls_modid].pointer.is_static = true;
 144
 145   /* Initialize the memory.  */
 146   memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
 147           '\0', map->l_tls_blocksize - map->l_tls_initimage_size);
 148 }
 149
 150
 151 void
 152 _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
 153                      int reloc_mode, int consider_profiling)
 154 {
 155   struct textrels
 156   {
 157     caddr_t start;
 158     size_t len;
 159     int prot;
 160     struct textrels *next;
 161   } *textrels = NULL;
 162   /* Initialize it to make the compiler happy.  */
 163   const char *errstring = NULL;
 164   int lazy = reloc_mode & RTLD_LAZY;
 165   int skip_ifunc = reloc_mode & __RTLD_NOIFUNC;
 166
 167 #ifdef SHARED
 168   /* If we are auditing, install the same handlers we need for profiling.  */
 169   if ((reloc_mode & __RTLD_AUDIT) == 0)
 170     consider_profiling |= GLRO(dl_audit) != NULL;
 171 #elif defined PROF
 172   /* Never use dynamic linker profiling for gprof profiling code.  */
 173 # define consider_profiling 0
 174 #endif
 175
 176   if (l->l_relocated)
 177     return;
 178
 179   /* If DT_BIND_NOW is set relocate all references in this object.  We
 180      do not do this if we are profiling, of course.  */
 181   // XXX Correct for auditing?
 182   if (!consider_profiling
 183       && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
 184     lazy = 0;
 185
 186   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_RELOC))
 187     _dl_debug_printf ("\nrelocation processing: %s%s\n",
 188                       DSO_FILENAME (l->l_name), lazy ? " (lazy)" : "");
 189
 190   /* DT_TEXTREL is now in level 2 and might phase out at some time.
 191      But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
 192      testing easier and therefore it will be available at all time.  */
 193   if (__glibc_unlikely (l->l_info[DT_TEXTREL] != NULL))
 194     {
 195       /* Bletch.  We must make read-only segments writable
 196          long enough to relocate them.  */
 197       const ElfW(Phdr) *ph;
 198       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
 199         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
 200           {
 201             struct textrels *newp;
 202
 203             newp = (struct textrels *) alloca (sizeof (*newp));
 204             newp->len = (((ph->p_vaddr + ph->p_memsz + GLRO(dl_pagesize) - 1)
 205                           & ~(GLRO(dl_pagesize) - 1))
 206                          - (ph->p_vaddr & ~(GLRO(dl_pagesize) - 1)));
 207             newp->start = ((ph->p_vaddr & ~(GLRO(dl_pagesize) - 1))
 208                            + (caddr_t) l->l_addr);
 209
 210             if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
 211               {
 212                 errstring = N_("cannot make segment writable for relocation");
 213               call_error:
 214                 _dl_signal_error (errno, l->l_name, NULL, errstring);
 215               }
 216
 217 #if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
 218             newp->prot = (PF_TO_PROT
 219                           >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
 220 #else
 221             newp->prot = 0;
 222             if (ph->p_flags & PF_R)
 223               newp->prot |= PROT_READ;
 224             if (ph->p_flags & PF_W)
 225               newp->prot |= PROT_WRITE;
 226             if (ph->p_flags & PF_X)
 227               newp->prot |= PROT_EXEC;
 228 #endif
 229             newp->next = textrels;
 230             textrels = newp;
 231           }
 232     }
 233
 234   {
 235     /* Do the actual relocation of the object's GOT and other data.  */
 236
 237     /* String table object symbols.  */
 238     const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
 239
 240     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
 241 #define RESOLVE_MAP(ref, version, r_type) \
 242     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 243      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 244          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 245         ? (bump_num_cache_relocations (),                                     \
 246            (*ref) = l->l_lookup_cache.ret,                                    \
 247            l->l_lookup_cache.value)                                           \
 248         : ({ lookup_t _lr;                                                    \
 249              int _tc = elf_machine_type_class (r_type);                       \
 250              l->l_lookup_cache.type_class = _tc;                              \
 251              l->l_lookup_cache.sym = (*ref);                                  \
 252              const struct r_found_version *v = NULL;                          \
 253              if ((version) != NULL && (version)->hash != 0)                   \
 254                v = (version);                                                 \
 255              _lr = _dl_lookup_symbol_x (strtab + (*ref)->st_name, l, (ref),   \
 256                                         scope, v, _tc,                        \
 257                                         DL_LOOKUP_ADD_DEPENDENCY, NULL);      \
 258              l->l_lookup_cache.ret = (*ref);                                  \
 259              l->l_lookup_cache.value = _lr; }))                               \
 260      : l)
 261
 262 #include "dynamic-link.h"
 263
 264     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling, skip_ifunc);
 265
 266 #ifndef PROF
 267     if (__glibc_unlikely (consider_profiling))
 268       {
 269         /* Allocate the array which will contain the already found
 270            relocations.  If the shared object lacks a PLT (for example
 271            if it only contains lead function) the l_info[DT_PLTRELSZ]
 272            will be NULL.  */
 273         if (l->l_info[DT_PLTRELSZ] == NULL)
 274           {
 275             errstring = N_("%s: no PLTREL found in object %s\n");
 276           fatal:
 277             _dl_fatal_printf (errstring,
 278                               RTLD_PROGNAME,
 279                               l->l_name);
 280           }
 281
 282         l->l_reloc_result = calloc (sizeof (l->l_reloc_result[0]),
 283                                     l->l_info[DT_PLTRELSZ]->d_un.d_val);
 284         if (l->l_reloc_result == NULL)
 285           {
 286             errstring = N_("\
 287 %s: out of memory to store relocation results for %s\n");
 288             goto fatal;
 289           }
 290       }
 291 #endif
 292   }
 293
 294   /* Mark the object so we know this work has been done.  */
 295   l->l_relocated = 1;
 296
 297   /* Undo the segment protection changes.  */
 298   while (__builtin_expect (textrels != NULL, 0))
 299     {
 300       if (__mprotect (textrels->start, textrels->len, textrels->prot) < 0)
 301         {
 302           errstring = N_("cannot restore segment prot after reloc");
 303           goto call_error;
 304         }
 305
 306 #ifdef CLEAR_CACHE
 307       CLEAR_CACHE (textrels->start, textrels->start + textrels->len);
 308 #endif
 309
 310       textrels = textrels->next;
 311     }
 312
 313   /* In case we can protect the data now that the relocations are
 314      done, do it.  */
 315   if (l->l_relro_size != 0)
 316     _dl_protect_relro (l);
 317 }
 318
 319
 320 void internal_function
 321 _dl_protect_relro (struct link_map *l)
 322 {
 323   ElfW(Addr) start = ((l->l_addr + l->l_relro_addr)
 324                       & ~(GLRO(dl_pagesize) - 1));
 325   ElfW(Addr) end = ((l->l_addr + l->l_relro_addr + l->l_relro_size)
 326                     & ~(GLRO(dl_pagesize) - 1));
 327
 328   if (start != end
 329       && __mprotect ((void *) start, end - start, PROT_READ) < 0)
 330     {
 331       static const char errstring[] = N_("\
 332 cannot apply additional memory protection after relocation");
 333       _dl_signal_error (errno, l->l_name, NULL, errstring);
 334     }
 335 }
 336
 337 void
 338 internal_function __attribute_noinline__
 339 _dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
 340 {
 341 #define DIGIT(b)        _itoa_lower_digits[(b) & 0xf];
 342
 343   /* XXX We cannot translate these messages.  */
 344   static const char msg[2][32
 345 #if __ELF_NATIVE_CLASS == 64
 346                            + 6
 347 #endif
 348   ] = { "unexpected reloc type 0x",
 349         "unexpected PLT reloc type 0x" };
 350   char msgbuf[sizeof (msg[0])];
 351   char *cp;
 352
 353   cp = __stpcpy (msgbuf, msg[plt]);
 354 #if __ELF_NATIVE_CLASS == 64
 355   if (__builtin_expect(type > 0xff, 0))
 356     {
 357       *cp++ = DIGIT (type >> 28);
 358       *cp++ = DIGIT (type >> 24);
 359       *cp++ = DIGIT (type >> 20);
 360       *cp++ = DIGIT (type >> 16);
 361       *cp++ = DIGIT (type >> 12);
 362       *cp++ = DIGIT (type >> 8);
 363     }
 364 #endif
 365   *cp++ = DIGIT (type >> 4);
 366   *cp++ = DIGIT (type);
 367   *cp = '\0';
 368
 369   _dl_signal_error (0, map->l_name, NULL, msgbuf);
 370 }