elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995-2004, 2005 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 #ifdef USE_TLS
  39 /* We are trying to perform a static TLS relocation in MAP, but it was
  40    dynamically loaded.  This can only work if there is enough surplus in
  41    the static TLS area already allocated for each running thread.  If this
  42    object's TLS segment is too big to fit, we fail.  If it fits,
  43    we set MAP->l_tls_offset and return.
  44    This function intentionally does not return any value but signals error
  45    directly, as static TLS should be rare and code handling it should
  46    not be inlined as much as possible.  */
  47 void
  48 internal_function __attribute_noinline__
  49 _dl_allocate_static_tls (struct link_map *map)
  50 {
  51   /* If the alignment requirements are too high fail.  */
  52   if (map->l_tls_align > GL(dl_tls_static_align))
  53     {
  54     fail:
  55       _dl_signal_error (0, map->l_name, NULL, N_("\
  56 cannot allocate memory in static TLS block"));
  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) - TLS_TCB_SIZE;
  65
  66   blsize = map->l_tls_blocksize + map->l_tls_firstbyte_offset;
  67   if (freebytes < blsize)
  68     goto fail;
  69
  70   n = (freebytes - blsize) / map->l_tls_align;
  71
  72   size_t offset = GL(dl_tls_static_used) + (freebytes - n * map->l_tls_align
  73                                             - map->l_tls_firstbyte_offset);
  74
  75   map->l_tls_offset = GL(dl_tls_static_used) = offset;
  76 # elif TLS_DTV_AT_TP
  77   size_t used;
  78   size_t check;
  79
  80   size_t offset = roundup (GL(dl_tls_static_used), map->l_tls_align);
  81   used = offset + map->l_tls_blocksize;
  82   check = used;
  83   /* dl_tls_static_used includes the TCB at the beginning.  */
  84
  85   if (check > GL(dl_tls_static_size))
  86     goto fail;
  87
  88   map->l_tls_offset = offset;
  89   GL(dl_tls_static_used) = used;
  90 # else
  91 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
  92 # endif
  93
  94   /* If the object is not yet relocated we cannot initialize the
  95      static TLS region.  Delay it.  */
  96   if (map->l_real->l_relocated)
  97     {
  98 #ifdef SHARED
  99       if (__builtin_expect (THREAD_DTV()[0].counter != GL(dl_tls_generation),
 100                             0))
 101         /* Update the slot information data for at least the generation of
 102            the DSO we are allocating data for.  */
 103         (void) _dl_update_slotinfo (map->l_tls_modid);
 104 #endif
 105
 106       GL(dl_init_static_tls) (map);
 107     }
 108   else
 109     map->l_need_tls_init = 1;
 110 }
 111
 112 /* Initialize static TLS area and DTV for current (only) thread.
 113    libpthread implementations should provide their own hook
 114    to handle all threads.  */
 115 void
 116 _dl_nothread_init_static_tls (struct link_map *map)
 117 {
 118 # if TLS_TCB_AT_TP
 119   void *dest = (char *) THREAD_SELF - map->l_tls_offset;
 120 # elif TLS_DTV_AT_TP
 121   void *dest = (char *) THREAD_SELF + map->l_tls_offset + TLS_PRE_TCB_SIZE;
 122 # else
 123 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 124 # endif
 125
 126   /* Fill in the DTV slot so that a later LD/GD access will find it.  */
 127   dtv_t *dtv = THREAD_DTV ();
 128   assert (map->l_tls_modid <= dtv[-1].counter);
 129   dtv[map->l_tls_modid].pointer.val = dest;
 130   dtv[map->l_tls_modid].pointer.is_static = true;
 131
 132   /* Initialize the memory.  */
 133   memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
 134           '\0', map->l_tls_blocksize - map->l_tls_initimage_size);
 135 }
 136 #endif
 137
 138
 139 void
 140 _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
 141                      int lazy, int consider_profiling)
 142 {
 143   struct textrels
 144   {
 145     caddr_t start;
 146     size_t len;
 147     int prot;
 148     struct textrels *next;
 149   } *textrels = NULL;
 150   /* Initialize it to make the compiler happy.  */
 151   const char *errstring = NULL;
 152
 153 #ifdef SHARED
 154   /* If we are auditing, install the same handlers we need for profiling.  */
 155   consider_profiling |= GLRO(dl_audit) != NULL;
 156 #endif
 157
 158   if (l->l_relocated)
 159     return;
 160
 161   /* If DT_BIND_NOW is set relocate all references in this object.  We
 162      do not do this if we are profiling, of course.  */
 163   // XXX Correct for auditing?
 164   if (!consider_profiling
 165       && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
 166     lazy = 0;
 167
 168   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_RELOC, 0))
 169     _dl_debug_printf ("\nrelocation processing: %s%s\n",
 170                       l->l_name[0] ? l->l_name : rtld_progname,
 171                       lazy ? " (lazy)" : "");
 172
 173   /* DT_TEXTREL is now in level 2 and might phase out at some time.
 174      But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
 175      testing easier and therefore it will be available at all time.  */
 176   if (__builtin_expect (l->l_info[DT_TEXTREL] != NULL, 0))
 177     {
 178       /* Bletch.  We must make read-only segments writable
 179          long enough to relocate them.  */
 180       const ElfW(Phdr) *ph;
 181       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
 182         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
 183           {
 184             struct textrels *newp;
 185
 186             newp = (struct textrels *) alloca (sizeof (*newp));
 187             newp->len = (((ph->p_vaddr + ph->p_memsz + GLRO(dl_pagesize) - 1)
 188                           & ~(GLRO(dl_pagesize) - 1))
 189                          - (ph->p_vaddr & ~(GLRO(dl_pagesize) - 1)));
 190             newp->start = ((ph->p_vaddr & ~(GLRO(dl_pagesize) - 1))
 191                            + (caddr_t) l->l_addr);
 192
 193             if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
 194               {
 195                 errstring = N_("cannot make segment writable for relocation");
 196               call_error:
 197                 _dl_signal_error (errno, l->l_name, NULL, errstring);
 198               }
 199
 200 #if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
 201             newp->prot = (PF_TO_PROT
 202                           >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
 203 #else
 204             newp->prot = 0;
 205             if (ph->p_flags & PF_R)
 206               newp->prot |= PROT_READ;
 207             if (ph->p_flags & PF_W)
 208               newp->prot |= PROT_WRITE;
 209             if (ph->p_flags & PF_X)
 210               newp->prot |= PROT_EXEC;
 211 #endif
 212             newp->next = textrels;
 213             textrels = newp;
 214           }
 215     }
 216
 217   {
 218     /* Do the actual relocation of the object's GOT and other data.  */
 219
 220     /* String table object symbols.  */
 221     const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
 222
 223     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
 224 #define RESOLVE_MAP(ref, version, r_type) \
 225     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 226      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 227          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 228         ? (bump_num_cache_relocations (),                                     \
 229            (*ref) = l->l_lookup_cache.ret,                                    \
 230            l->l_lookup_cache.value)                                           \
 231         : ({ lookup_t _lr;                                                    \
 232              int _tc = elf_machine_type_class (r_type);                       \
 233              l->l_lookup_cache.type_class = _tc;                              \
 234              l->l_lookup_cache.sym = (*ref);                                  \
 235              const struct r_found_version *v = NULL;                          \
 236              int flags = DL_LOOKUP_ADD_DEPENDENCY;                            \
 237              if ((version) != NULL && (version)->hash != 0)                   \
 238                {                                                              \
 239                  v = (version);                                               \
 240                  flags = 0;                                                   \
 241                }                                                              \
 242              _lr = _dl_lookup_symbol_x (strtab + (*ref)->st_name, l, (ref),   \
 243                                         scope, v, _tc, flags, NULL);          \
 244              l->l_lookup_cache.ret = (*ref);                                  \
 245              l->l_lookup_cache.value = _lr; }))                               \
 246      : l)
 247
 248     /* This macro is used as a callback from elf_machine_rel{a,} when a
 249        static TLS reloc is about to be performed.  Since (in dl-load.c) we
 250        permit dynamic loading of objects that might use such relocs, we
 251        have to check whether each use is actually doable.  If the object
 252        whose TLS segment the reference resolves to was allocated space in
 253        the static TLS block at startup, then it's ok.  Otherwise, we make
 254        an attempt to allocate it in surplus space on the fly.  If that
 255        can't be done, we fall back to the error that DF_STATIC_TLS is
 256        intended to produce.  */
 257 #define CHECK_STATIC_TLS(map, sym_map)                                        \
 258     do {                                                                      \
 259       if (__builtin_expect ((sym_map)->l_tls_offset == NO_TLS_OFFSET, 0))     \
 260         _dl_allocate_static_tls (sym_map);                                    \
 261     } while (0)
 262
 263 #include "dynamic-link.h"
 264
 265     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling);
 266
 267     if (__builtin_expect (consider_profiling, 0))
 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 ?: "<program name unknown>",
 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   }
 292
 293   /* Mark the object so we know this work has been done.  */
 294   l->l_relocated = 1;
 295
 296   /* Undo the segment protection changes.  */
 297   while (__builtin_expect (textrels != NULL, 0))
 298     {
 299       if (__mprotect (textrels->start, textrels->len, textrels->prot) < 0)
 300         {
 301           errstring = N_("cannot restore segment prot after reloc");
 302           goto call_error;
 303         }
 304
 305       textrels = textrels->next;
 306     }
 307
 308   /* In case we can protect the data now that the relocations are
 309      done, do it.  */
 310   if (l->l_relro_size != 0)
 311     _dl_protect_relro (l);
 312 }
 313
 314
 315 void internal_function
 316 _dl_protect_relro (struct link_map *l)
 317 {
 318   ElfW(Addr) start = ((l->l_addr + l->l_relro_addr)
 319                       & ~(GLRO(dl_pagesize) - 1));
 320   ElfW(Addr) end = ((l->l_addr + l->l_relro_addr + l->l_relro_size)
 321                     & ~(GLRO(dl_pagesize) - 1));
 322
 323   if (start != end
 324       && __mprotect ((void *) start, end - start, PROT_READ) < 0)
 325     {
 326       static const char errstring[] = N_("\
 327 cannot apply additional memory protection after relocation");
 328       _dl_signal_error (errno, l->l_name, NULL, errstring);
 329     }
 330 }
 331
 332 void
 333 internal_function __attribute_noinline__
 334 _dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
 335 {
 336   extern const char INTUSE(_itoa_lower_digits)[] attribute_hidden;
 337 #define DIGIT(b)        INTUSE(_itoa_lower_digits)[(b) & 0xf];
 338
 339   /* XXX We cannot translate these messages.  */
 340   static const char msg[2][32
 341 #if __ELF_NATIVE_CLASS == 64
 342                            + 6
 343 #endif
 344   ] = { "unexpected reloc type 0x",
 345         "unexpected PLT reloc type 0x" };
 346   char msgbuf[sizeof (msg[0])];
 347   char *cp;
 348
 349   cp = __stpcpy (msgbuf, msg[plt]);
 350 #if __ELF_NATIVE_CLASS == 64
 351   if (__builtin_expect(type > 0xff, 0))
 352     {
 353       *cp++ = DIGIT (type >> 28);
 354       *cp++ = DIGIT (type >> 24);
 355       *cp++ = DIGIT (type >> 20);
 356       *cp++ = DIGIT (type >> 16);
 357       *cp++ = DIGIT (type >> 12);
 358       *cp++ = DIGIT (type >> 8);
 359     }
 360 #endif
 361   *cp++ = DIGIT (type >> 4);
 362   *cp++ = DIGIT (type);
 363   *cp = '\0';
 364
 365   _dl_signal_error (0, map->l_name, NULL, msgbuf);
 366 }