elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995-2006, 2008, 2009 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) - 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   return 0;
 112 }
 113
 114 void
 115 internal_function __attribute_noinline__
 116 _dl_allocate_static_tls (struct link_map *map)
 117 {
 118   if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
 119       || _dl_try_allocate_static_tls (map))
 120     {
 121       _dl_signal_error (0, map->l_name, NULL, N_("\
 122 cannot allocate memory in static TLS block"));
 123     }
 124 }
 125
 126 /* Initialize static TLS area and DTV for current (only) thread.
 127    libpthread implementations should provide their own hook
 128    to handle all threads.  */
 129 void
 130 _dl_nothread_init_static_tls (struct link_map *map)
 131 {
 132 #if TLS_TCB_AT_TP
 133   void *dest = (char *) THREAD_SELF - map->l_tls_offset;
 134 #elif TLS_DTV_AT_TP
 135   void *dest = (char *) THREAD_SELF + map->l_tls_offset + TLS_PRE_TCB_SIZE;
 136 #else
 137 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 138 #endif
 139
 140   /* Fill in the DTV slot so that a later LD/GD access will find it.  */
 141   dtv_t *dtv = THREAD_DTV ();
 142   assert (map->l_tls_modid <= dtv[-1].counter);
 143   dtv[map->l_tls_modid].pointer.val = dest;
 144   dtv[map->l_tls_modid].pointer.is_static = true;
 145
 146   /* Initialize the memory.  */
 147   memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
 148           '\0', map->l_tls_blocksize - map->l_tls_initimage_size);
 149 }
 150
 151
 152 void
 153 _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
 154                      int reloc_mode, int consider_profiling)
 155 {
 156   struct textrels
 157   {
 158     caddr_t start;
 159     size_t len;
 160     int prot;
 161     struct textrels *next;
 162   } *textrels = NULL;
 163   /* Initialize it to make the compiler happy.  */
 164   const char *errstring = NULL;
 165   int lazy = reloc_mode & RTLD_LAZY;
 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 (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_RELOC, 0))
 187     _dl_debug_printf ("\nrelocation processing: %s%s\n",
 188                       l->l_name[0] ? l->l_name : rtld_progname,
 189                       lazy ? " (lazy)" : "");
 190
 191   /* DT_TEXTREL is now in level 2 and might phase out at some time.
 192      But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
 193      testing easier and therefore it will be available at all time.  */
 194   if (__builtin_expect (l->l_info[DT_TEXTREL] != NULL, 0))
 195     {
 196       /* Bletch.  We must make read-only segments writable
 197          long enough to relocate them.  */
 198       const ElfW(Phdr) *ph;
 199       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
 200         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
 201           {
 202             struct textrels *newp;
 203
 204             newp = (struct textrels *) alloca (sizeof (*newp));
 205             newp->len = (((ph->p_vaddr + ph->p_memsz + GLRO(dl_pagesize) - 1)
 206                           & ~(GLRO(dl_pagesize) - 1))
 207                          - (ph->p_vaddr & ~(GLRO(dl_pagesize) - 1)));
 208             newp->start = ((ph->p_vaddr & ~(GLRO(dl_pagesize) - 1))
 209                            + (caddr_t) l->l_addr);
 210
 211             if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
 212               {
 213                 errstring = N_("cannot make segment writable for relocation");
 214               call_error:
 215                 _dl_signal_error (errno, l->l_name, NULL, errstring);
 216               }
 217
 218 #if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
 219             newp->prot = (PF_TO_PROT
 220                           >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
 221 #else
 222             newp->prot = 0;
 223             if (ph->p_flags & PF_R)
 224               newp->prot |= PROT_READ;
 225             if (ph->p_flags & PF_W)
 226               newp->prot |= PROT_WRITE;
 227             if (ph->p_flags & PF_X)
 228               newp->prot |= PROT_EXEC;
 229 #endif
 230             newp->next = textrels;
 231             textrels = newp;
 232           }
 233     }
 234
 235   {
 236     /* Do the actual relocation of the object's GOT and other data.  */
 237
 238     /* String table object symbols.  */
 239     const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
 240
 241     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
 242 #define RESOLVE_MAP(ref, version, r_type) \
 243     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 244      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 245          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 246         ? (bump_num_cache_relocations (),                                     \
 247            (*ref) = l->l_lookup_cache.ret,                                    \
 248            l->l_lookup_cache.value)                                           \
 249         : ({ lookup_t _lr;                                                    \
 250              int _tc = elf_machine_type_class (r_type);                       \
 251              l->l_lookup_cache.type_class = _tc;                              \
 252              l->l_lookup_cache.sym = (*ref);                                  \
 253              const struct r_found_version *v = NULL;                          \
 254              int flags = DL_LOOKUP_ADD_DEPENDENCY;                            \
 255              if ((version) != NULL && (version)->hash != 0)                   \
 256                {                                                              \
 257                  v = (version);                                               \
 258                  flags = 0;                                                   \
 259                }                                                              \
 260              _lr = _dl_lookup_symbol_x (strtab + (*ref)->st_name, l, (ref),   \
 261                                         scope, v, _tc, flags, 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       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   extern const char INTUSE(_itoa_lower_digits)[] attribute_hidden;
 342 #define DIGIT(b)        INTUSE(_itoa_lower_digits)[(b) & 0xf];
 343
 344   /* XXX We cannot translate these messages.  */
 345   static const char msg[2][32
 346 #if __ELF_NATIVE_CLASS == 64
 347                            + 6
 348 #endif
 349   ] = { "unexpected reloc type 0x",
 350         "unexpected PLT reloc type 0x" };
 351   char msgbuf[sizeof (msg[0])];
 352   char *cp;
 353
 354   cp = __stpcpy (msgbuf, msg[plt]);
 355 #if __ELF_NATIVE_CLASS == 64
 356   if (__builtin_expect(type > 0xff, 0))
 357     {
 358       *cp++ = DIGIT (type >> 28);
 359       *cp++ = DIGIT (type >> 24);
 360       *cp++ = DIGIT (type >> 20);
 361       *cp++ = DIGIT (type >> 16);
 362       *cp++ = DIGIT (type >> 12);
 363       *cp++ = DIGIT (type >> 8);
 364     }
 365 #endif
 366   *cp++ = DIGIT (type >> 4);
 367   *cp++ = DIGIT (type);
 368   *cp = '\0';
 369
 370   _dl_signal_error (0, map->l_name, NULL, msgbuf);
 371 }