elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995-2002, 2003 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   size_t offset;
  52
  53   /* If the alignment requirements are too high fail.  */
  54   if (map->l_tls_align > GL(dl_tls_static_align))
  55     {
  56     fail:
  57       INTUSE(_dl_signal_error) (0, map->l_name, NULL, N_("\
  58 cannot allocate memory in static TLS block"));
  59     }
  60
  61 # if TLS_TCB_AT_TP
  62   size_t freebytes;
  63   size_t n;
  64   size_t blsize;
  65
  66   freebytes = GL(dl_tls_static_size) - GL(dl_tls_static_used) - TLS_TCB_SIZE;
  67
  68   blsize = map->l_tls_blocksize + map->l_tls_firstbyte_offset;
  69   if (freebytes < blsize)
  70     goto fail;
  71
  72   n = (freebytes - blsize) / map->l_tls_align;
  73
  74   offset = GL(dl_tls_static_used) + (freebytes - n * map->l_tls_align
  75                                      - map->l_tls_firstbyte_offset);
  76
  77   map->l_tls_offset = GL(dl_tls_static_used) = offset;
  78 # elif TLS_DTV_AT_TP
  79   size_t used;
  80   size_t check;
  81
  82   offset = roundup (GL(dl_tls_static_used), map->l_tls_align);
  83   used = offset + map->l_tls_blocksize;
  84   check = used;
  85   /* dl_tls_static_used includes the TCB at the beginning.  */
  86
  87   if (check > GL(dl_tls_static_size))
  88     goto fail;
  89
  90   map->l_tls_offset = offset;
  91   GL(dl_tls_static_used) = used;
  92 # else
  93 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
  94 # endif
  95
  96   if (map->l_relocated)
  97     GL(dl_init_static_tls) (map);
  98   else
  99     map->l_need_tls_init = 1;
 100 }
 101
 102 /* Initialize static TLS area and DTV for current (only) thread.
 103    libpthread implementations should provide their own hook
 104    to handle all threads.  */
 105 void
 106 _dl_nothread_init_static_tls (struct link_map *map)
 107 {
 108 # if TLS_TCB_AT_TP
 109   void *dest = (char *) THREAD_SELF - map->l_tls_offset;
 110 # elif TLS_DTV_AT_TP
 111   void *dest = (char *) THREAD_SELF + map->l_tls_offset + TLS_PRE_TCB_SIZE;
 112 # else
 113 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 114 # endif
 115
 116   /* Fill in the DTV slot so that a later LD/GD access will find it.  */
 117   THREAD_DTV ()[map->l_tls_modid].pointer = dest;
 118
 119   /* Initialize the memory.  */
 120   memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
 121           '\0', map->l_tls_blocksize - map->l_tls_initimage_size);
 122 }
 123 #endif
 124
 125
 126 void
 127 _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
 128                      int lazy, int consider_profiling)
 129 {
 130   struct textrels
 131   {
 132     caddr_t start;
 133     size_t len;
 134     int prot;
 135     struct textrels *next;
 136   } *textrels = NULL;
 137   /* Initialize it to make the compiler happy.  */
 138   const char *errstring = NULL;
 139
 140   if (l->l_relocated)
 141     return;
 142
 143   /* If DT_BIND_NOW is set relocate all references in this object.  We
 144      do not do this if we are profiling, of course.  */
 145   if (!consider_profiling
 146       && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
 147     lazy = 0;
 148
 149   if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_RELOC, 0))
 150     INTUSE(_dl_debug_printf) ("\nrelocation processing: %s%s\n",
 151                               l->l_name[0] ? l->l_name : rtld_progname,
 152                               lazy ? " (lazy)" : "");
 153
 154   /* DT_TEXTREL is now in level 2 and might phase out at some time.
 155      But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
 156      testing easier and therefore it will be available at all time.  */
 157   if (__builtin_expect (l->l_info[DT_TEXTREL] != NULL, 0))
 158     {
 159       /* Bletch.  We must make read-only segments writable
 160          long enough to relocate them.  */
 161       const ElfW(Phdr) *ph;
 162       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
 163         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
 164           {
 165             struct textrels *newp;
 166
 167             newp = (struct textrels *) alloca (sizeof (*newp));
 168             newp->len = (((ph->p_vaddr + ph->p_memsz + GL(dl_pagesize) - 1)
 169                           & ~(GL(dl_pagesize) - 1))
 170                          - (ph->p_vaddr & ~(GL(dl_pagesize) - 1)));
 171             newp->start = ((ph->p_vaddr & ~(GL(dl_pagesize) - 1))
 172                            + (caddr_t) l->l_addr);
 173
 174             if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
 175               {
 176                 errstring = N_("cannot make segment writable for relocation");
 177               call_error:
 178                 INTUSE(_dl_signal_error) (errno, l->l_name, NULL, errstring);
 179               }
 180
 181 #if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
 182             newp->prot = (PF_TO_PROT
 183                           >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
 184 #else
 185             newp->prot = 0;
 186             if (ph->p_flags & PF_R)
 187               newp->prot |= PROT_READ;
 188             if (ph->p_flags & PF_W)
 189               newp->prot |= PROT_WRITE;
 190             if (ph->p_flags & PF_X)
 191               newp->prot |= PROT_EXEC;
 192 #endif
 193             newp->next = textrels;
 194             textrels = newp;
 195           }
 196     }
 197
 198   {
 199     /* Do the actual relocation of the object's GOT and other data.  */
 200
 201     /* String table object symbols.  */
 202     const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
 203
 204     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
 205 #define RESOLVE_MAP(ref, version, r_type) \
 206     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 207      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 208          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 209         ? (bump_num_cache_relocations (),                                     \
 210            (*ref) = l->l_lookup_cache.ret,                                    \
 211            l->l_lookup_cache.value)                                           \
 212         : ({ lookup_t _lr;                                                    \
 213              int _tc = elf_machine_type_class (r_type);                       \
 214              l->l_lookup_cache.type_class = _tc;                              \
 215              l->l_lookup_cache.sym = (*ref);                                  \
 216              _lr = ((version) != NULL && (version)->hash != 0                 \
 217                     ? INTUSE(_dl_lookup_versioned_symbol) (strtab             \
 218                                                            + (*ref)->st_name, \
 219                                                            l, (ref), scope,   \
 220                                                            (version), _tc, 0) \
 221                     : INTUSE(_dl_lookup_symbol) (strtab + (*ref)->st_name, l, \
 222                                                  (ref), scope, _tc,           \
 223                                                  DL_LOOKUP_ADD_DEPENDENCY));  \
 224              l->l_lookup_cache.ret = (*ref);                                  \
 225              l->l_lookup_cache.value = _lr; }))                               \
 226      : l)
 227 #define RESOLVE(ref, version, r_type) \
 228     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 229      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 230          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 231                 ? (bump_num_cache_relocations (),                             \
 232            (*ref) = l->l_lookup_cache.ret,                                    \
 233            l->l_lookup_cache.value)                                           \
 234         : ({ lookup_t _lr;                                                    \
 235              int _tc = elf_machine_type_class (r_type);                       \
 236              l->l_lookup_cache.type_class = _tc;                              \
 237              l->l_lookup_cache.sym = (*ref);                                  \
 238              _lr = ((version) != NULL && (version)->hash != 0                 \
 239                     ? INTUSE(_dl_lookup_versioned_symbol) (strtab             \
 240                                                            + (*ref)->st_name, \
 241                                                            l, (ref), scope,   \
 242                                                            (version), _tc, 0) \
 243                     : INTUSE(_dl_lookup_symbol) (strtab + (*ref)->st_name, l, \
 244                                                  (ref), scope, _tc,           \
 245                                                  DL_LOOKUP_ADD_DEPENDENCY));  \
 246              l->l_lookup_cache.ret = (*ref);                                  \
 247              l->l_lookup_cache.value = _lr; }))                               \
 248      : l->l_addr)
 249
 250     /* This macro is used as a callback from elf_machine_rel{a,} when a
 251        static TLS reloc is about to be performed.  Since (in dl-load.c) we
 252        permit dynamic loading of objects that might use such relocs, we
 253        have to check whether each use is actually doable.  If the object
 254        whose TLS segment the reference resolves to was allocated space in
 255        the static TLS block at startup, then it's ok.  Otherwise, we make
 256        an attempt to allocate it in surplus space on the fly.  If that
 257        can't be done, we fall back to the error that DF_STATIC_TLS is
 258        intended to produce.  */
 259 #define CHECK_STATIC_TLS(map, sym_map)                                        \
 260     do {                                                                      \
 261       if (__builtin_expect ((sym_map)->l_tls_offset == NO_TLS_OFFSET, 0))     \
 262         _dl_allocate_static_tls (sym_map);                                    \
 263     } while (0)
 264
 265 #include "dynamic-link.h"
 266
 267     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling);
 268
 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: profiler found no PLTREL 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 =
 285           (ElfW(Addr) *) calloc (sizeof (ElfW(Addr)),
 286                                  l->l_info[DT_PLTRELSZ]->d_un.d_val);
 287         if (l->l_reloc_result == NULL)
 288           {
 289             errstring = N_("\
 290 %s: profiler out of memory shadowing PLTREL of %s\n");
 291             goto fatal;
 292           }
 293       }
 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 INTDEF (_dl_relocate_object)
 312
 313
 314 void
 315 internal_function __attribute_noinline__
 316 _dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
 317 {
 318   extern const char INTUSE(_itoa_lower_digits)[] attribute_hidden;
 319 #define DIGIT(b)        INTUSE(_itoa_lower_digits)[(b) & 0xf];
 320
 321   /* XXX We cannot translate these messages.  */
 322   static const char msg[2][32
 323 #if __ELF_NATIVE_CLASS == 64
 324                            + 6
 325 #endif
 326   ] = { "unexpected reloc type 0x",
 327         "unexpected PLT reloc type 0x" };
 328   char msgbuf[sizeof (msg[0])];
 329   char *cp;
 330
 331   cp = __stpcpy (msgbuf, msg[plt]);
 332 #if __ELF_NATIVE_CLASS == 64
 333   if (__builtin_expect(type > 0xff, 0))
 334     {
 335       *cp++ = DIGIT (type >> 28);
 336       *cp++ = DIGIT (type >> 24);
 337       *cp++ = DIGIT (type >> 20);
 338       *cp++ = DIGIT (type >> 16);
 339       *cp++ = DIGIT (type >> 12);
 340       *cp++ = DIGIT (type >> 8);
 341     }
 342 #endif
 343   *cp++ = DIGIT (type >> 4);
 344   *cp++ = DIGIT (type);
 345   *cp = '\0';
 346
 347   INTUSE(_dl_signal_error) (0, map->l_name, NULL, msgbuf);
 348 }