elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995-2017 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 #include <libc-internal.h>
  30
  31 /* Statistics function.  */
  32 #ifdef SHARED
  33 # define bump_num_cache_relocations() ++GL(dl_num_cache_relocations)
  34 #else
  35 # define bump_num_cache_relocations() ((void) 0)
  36 #endif
  37
  38
  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 int
  48 internal_function
  49 _dl_try_allocate_static_tls (struct link_map *map)
  50 {
  51   /* If we've already used the variable with dynamic access, or if the
  52      alignment requirements are too high, fail.  */
  53   if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
  54       || map->l_tls_align > GL(dl_tls_static_align))
  55     {
  56     fail:
  57       return -1;
  58     }
  59
  60 #if TLS_TCB_AT_TP
  61   size_t freebytes = GL(dl_tls_static_size) - GL(dl_tls_static_used);
  62   if (freebytes < TLS_TCB_SIZE)
  63     goto fail;
  64   freebytes -= TLS_TCB_SIZE;
  65
  66   size_t blsize = map->l_tls_blocksize + map->l_tls_firstbyte_offset;
  67   if (freebytes < blsize)
  68     goto fail;
  69
  70   size_t 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   /* dl_tls_static_used includes the TCB at the beginning.  */
  78   size_t offset = (ALIGN_UP(GL(dl_tls_static_used)
  79                             - map->l_tls_firstbyte_offset,
  80                             map->l_tls_align)
  81                    + map->l_tls_firstbyte_offset);
  82   size_t used = offset + map->l_tls_blocksize;
  83
  84   if (used > GL(dl_tls_static_size))
  85     goto fail;
  86
  87   map->l_tls_offset = offset;
  88   map->l_tls_firstbyte_offset = GL(dl_tls_static_used);
  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.to_free = NULL;
 144   dtv[map->l_tls_modid].pointer.val = dest;
 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   int skip_ifunc = reloc_mode & __RTLD_NOIFUNC;
 167
 168 #ifdef SHARED
 169   /* If we are auditing, install the same handlers we need for profiling.  */
 170   if ((reloc_mode & __RTLD_AUDIT) == 0)
 171     consider_profiling |= GLRO(dl_audit) != NULL;
 172 #elif defined PROF
 173   /* Never use dynamic linker profiling for gprof profiling code.  */
 174 # define consider_profiling 0
 175 #endif
 176
 177   if (l->l_relocated)
 178     return;
 179
 180   /* If DT_BIND_NOW is set relocate all references in this object.  We
 181      do not do this if we are profiling, of course.  */
 182   // XXX Correct for auditing?
 183   if (!consider_profiling
 184       && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
 185     lazy = 0;
 186
 187   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_RELOC))
 188     _dl_debug_printf ("\nrelocation processing: %s%s\n",
 189                       DSO_FILENAME (l->l_name), 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 (__glibc_unlikely (l->l_info[DT_TEXTREL] != NULL))
 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 = ALIGN_UP (ph->p_vaddr + ph->p_memsz, GLRO(dl_pagesize))
 206                         - ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize));
 207             newp->start = PTR_ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize))
 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       && __glibc_likely (!dl_symbol_visibility_binds_local_p (*ref)))         \
 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              if ((version) != NULL && (version)->hash != 0)                   \
 255                v = (version);                                                 \
 256              _lr = _dl_lookup_symbol_x (strtab + (*ref)->st_name, l, (ref),   \
 257                                         scope, v, _tc,                        \
 258                                         DL_LOOKUP_ADD_DEPENDENCY, NULL);      \
 259              l->l_lookup_cache.ret = (*ref);                                  \
 260              l->l_lookup_cache.value = _lr; }))                               \
 261      : l)
 262
 263 #include "dynamic-link.h"
 264
 265     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling, skip_ifunc);
 266
 267 #ifndef PROF
 268     if (__glibc_unlikely (consider_profiling)
 269         && l->l_info[DT_PLTRELSZ] != NULL)
 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         size_t sizeofrel = l->l_info[DT_PLTREL]->d_un.d_val == DT_RELA
 276                            ? sizeof (ElfW(Rela))
 277                            : sizeof (ElfW(Rel));
 278         size_t relcount = l->l_info[DT_PLTRELSZ]->d_un.d_val / sizeofrel;
 279         l->l_reloc_result = calloc (sizeof (l->l_reloc_result[0]), relcount);
 280
 281         if (l->l_reloc_result == NULL)
 282           {
 283             errstring = N_("\
 284 %s: out of memory to store relocation results for %s\n");
 285             _dl_fatal_printf (errstring, RTLD_PROGNAME, l->l_name);
 286           }
 287       }
 288 #endif
 289   }
 290
 291   /* Mark the object so we know this work has been done.  */
 292   l->l_relocated = 1;
 293
 294   /* Undo the segment protection changes.  */
 295   while (__builtin_expect (textrels != NULL, 0))
 296     {
 297       if (__mprotect (textrels->start, textrels->len, textrels->prot) < 0)
 298         {
 299           errstring = N_("cannot restore segment prot after reloc");
 300           goto call_error;
 301         }
 302
 303 #ifdef CLEAR_CACHE
 304       CLEAR_CACHE (textrels->start, textrels->start + textrels->len);
 305 #endif
 306
 307       textrels = textrels->next;
 308     }
 309
 310   /* In case we can protect the data now that the relocations are
 311      done, do it.  */
 312   if (l->l_relro_size != 0)
 313     _dl_protect_relro (l);
 314 }
 315
 316
 317 void internal_function
 318 _dl_protect_relro (struct link_map *l)
 319 {
 320   ElfW(Addr) start = ALIGN_DOWN((l->l_addr
 321                                  + l->l_relro_addr),
 322                                 GLRO(dl_pagesize));
 323   ElfW(Addr) end = ALIGN_DOWN((l->l_addr
 324                                + l->l_relro_addr
 325                                + l->l_relro_size),
 326                               GLRO(dl_pagesize));
 327   if (start != end
 328       && __mprotect ((void *) start, end - start, PROT_READ) < 0)
 329     {
 330       static const char errstring[] = N_("\
 331 cannot apply additional memory protection after relocation");
 332       _dl_signal_error (errno, l->l_name, NULL, errstring);
 333     }
 334 }
 335
 336 void
 337 internal_function __attribute_noinline__
 338 _dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
 339 {
 340 #define DIGIT(b)        _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 }