elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995-2004, 2005, 2006, 2008 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 lazy, 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
 166 #ifdef SHARED
 167   /* If we are auditing, install the same handlers we need for profiling.  */
 168   consider_profiling |= GLRO(dl_audit) != NULL;
 169 #elif defined PROF
 170   /* Never use dynamic linker profiling for gprof profiling code.  */
 171 # define consider_profiling 0
 172 #endif
 173
 174   if (l->l_relocated)
 175     return;
 176
 177   /* If DT_BIND_NOW is set relocate all references in this object.  We
 178      do not do this if we are profiling, of course.  */
 179   // XXX Correct for auditing?
 180   if (!consider_profiling
 181       && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
 182     lazy = 0;
 183
 184   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_RELOC, 0))
 185     _dl_debug_printf ("\nrelocation processing: %s%s\n",
 186                       l->l_name[0] ? l->l_name : rtld_progname,
 187                       lazy ? " (lazy)" : "");
 188
 189   /* DT_TEXTREL is now in level 2 and might phase out at some time.
 190      But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
 191      testing easier and therefore it will be available at all time.  */
 192   if (__builtin_expect (l->l_info[DT_TEXTREL] != NULL, 0))
 193     {
 194       /* Bletch.  We must make read-only segments writable
 195          long enough to relocate them.  */
 196       const ElfW(Phdr) *ph;
 197       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
 198         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
 199           {
 200             struct textrels *newp;
 201
 202             newp = (struct textrels *) alloca (sizeof (*newp));
 203             newp->len = (((ph->p_vaddr + ph->p_memsz + GLRO(dl_pagesize) - 1)
 204                           & ~(GLRO(dl_pagesize) - 1))
 205                          - (ph->p_vaddr & ~(GLRO(dl_pagesize) - 1)));
 206             newp->start = ((ph->p_vaddr & ~(GLRO(dl_pagesize) - 1))
 207                            + (caddr_t) l->l_addr);
 208
 209             if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
 210               {
 211                 errstring = N_("cannot make segment writable for relocation");
 212               call_error:
 213                 _dl_signal_error (errno, l->l_name, NULL, errstring);
 214               }
 215
 216 #if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
 217             newp->prot = (PF_TO_PROT
 218                           >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
 219 #else
 220             newp->prot = 0;
 221             if (ph->p_flags & PF_R)
 222               newp->prot |= PROT_READ;
 223             if (ph->p_flags & PF_W)
 224               newp->prot |= PROT_WRITE;
 225             if (ph->p_flags & PF_X)
 226               newp->prot |= PROT_EXEC;
 227 #endif
 228             newp->next = textrels;
 229             textrels = newp;
 230           }
 231     }
 232
 233   {
 234     /* Do the actual relocation of the object's GOT and other data.  */
 235
 236     /* String table object symbols.  */
 237     const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
 238
 239     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
 240 #define RESOLVE_MAP(ref, version, r_type) \
 241     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 242      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 243          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 244         ? (bump_num_cache_relocations (),                                     \
 245            (*ref) = l->l_lookup_cache.ret,                                    \
 246            l->l_lookup_cache.value)                                           \
 247         : ({ lookup_t _lr;                                                    \
 248              int _tc = elf_machine_type_class (r_type);                       \
 249              l->l_lookup_cache.type_class = _tc;                              \
 250              l->l_lookup_cache.sym = (*ref);                                  \
 251              const struct r_found_version *v = NULL;                          \
 252              int flags = DL_LOOKUP_ADD_DEPENDENCY;                            \
 253              if ((version) != NULL && (version)->hash != 0)                   \
 254                {                                                              \
 255                  v = (version);                                               \
 256                  flags = 0;                                                   \
 257                }                                                              \
 258              _lr = _dl_lookup_symbol_x (strtab + (*ref)->st_name, l, (ref),   \
 259                                         scope, v, _tc, flags, NULL);          \
 260              l->l_lookup_cache.ret = (*ref);                                  \
 261              l->l_lookup_cache.value = _lr; }))                               \
 262      : l)
 263
 264 #include "dynamic-link.h"
 265
 266     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling);
 267
 268 #ifndef PROF
 269     if (__builtin_expect (consider_profiling, 0))
 270       {
 271         /* Allocate the array which will contain the already found
 272            relocations.  If the shared object lacks a PLT (for example
 273            if it only contains lead function) the l_info[DT_PLTRELSZ]
 274            will be NULL.  */
 275         if (l->l_info[DT_PLTRELSZ] == NULL)
 276           {
 277             errstring = N_("%s: no PLTREL found in object %s\n");
 278           fatal:
 279             _dl_fatal_printf (errstring,
 280                               rtld_progname ?: "<program name unknown>",
 281                               l->l_name);
 282           }
 283
 284         l->l_reloc_result = calloc (sizeof (l->l_reloc_result[0]),
 285                                     l->l_info[DT_PLTRELSZ]->d_un.d_val);
 286         if (l->l_reloc_result == NULL)
 287           {
 288             errstring = N_("\
 289 %s: out of memory to store relocation results for %s\n");
 290             goto fatal;
 291           }
 292       }
 293 #endif
 294   }
 295
 296   /* Mark the object so we know this work has been done.  */
 297   l->l_relocated = 1;
 298
 299   /* Undo the segment protection changes.  */
 300   while (__builtin_expect (textrels != NULL, 0))
 301     {
 302       if (__mprotect (textrels->start, textrels->len, textrels->prot) < 0)
 303         {
 304           errstring = N_("cannot restore segment prot after reloc");
 305           goto call_error;
 306         }
 307
 308       textrels = textrels->next;
 309     }
 310
 311   /* In case we can protect the data now that the relocations are
 312      done, do it.  */
 313   if (l->l_relro_size != 0)
 314     _dl_protect_relro (l);
 315 }
 316
 317
 318 void internal_function
 319 _dl_protect_relro (struct link_map *l)
 320 {
 321   ElfW(Addr) start = ((l->l_addr + l->l_relro_addr)
 322                       & ~(GLRO(dl_pagesize) - 1));
 323   ElfW(Addr) end = ((l->l_addr + l->l_relro_addr + l->l_relro_size)
 324                     & ~(GLRO(dl_pagesize) - 1));
 325
 326   if (start != end
 327       && __mprotect ((void *) start, end - start, PROT_READ) < 0)
 328     {
 329       static const char errstring[] = N_("\
 330 cannot apply additional memory protection after relocation");
 331       _dl_signal_error (errno, l->l_name, NULL, errstring);
 332     }
 333 }
 334
 335 void
 336 internal_function __attribute_noinline__
 337 _dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
 338 {
 339   extern const char INTUSE(_itoa_lower_digits)[] attribute_hidden;
 340 #define DIGIT(b)        INTUSE(_itoa_lower_digits)[(b) & 0xf];
 341
 342   /* XXX We cannot translate these messages.  */
 343   static const char msg[2][32
 344 #if __ELF_NATIVE_CLASS == 64
 345                            + 6
 346 #endif
 347   ] = { "unexpected reloc type 0x",
 348         "unexpected PLT reloc type 0x" };
 349   char msgbuf[sizeof (msg[0])];
 350   char *cp;
 351
 352   cp = __stpcpy (msgbuf, msg[plt]);
 353 #if __ELF_NATIVE_CLASS == 64
 354   if (__builtin_expect(type > 0xff, 0))
 355     {
 356       *cp++ = DIGIT (type >> 28);
 357       *cp++ = DIGIT (type >> 24);
 358       *cp++ = DIGIT (type >> 20);
 359       *cp++ = DIGIT (type >> 16);
 360       *cp++ = DIGIT (type >> 12);
 361       *cp++ = DIGIT (type >> 8);
 362     }
 363 #endif
 364   *cp++ = DIGIT (type >> 4);
 365   *cp++ = DIGIT (type);
 366   *cp = '\0';
 367
 368   _dl_signal_error (0, map->l_name, NULL, msgbuf);
 369 }