elf/dl-reloc.c

   1 /* Relocate a shared object and resolve its references to other loaded objects.
   2    Copyright (C) 1995-2002, 2003, 2004 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       _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 (GLRO(dl_debug_mask) & DL_DEBUG_RELOC, 0))
 150     _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 + GLRO(dl_pagesize) - 1)
 169                           & ~(GLRO(dl_pagesize) - 1))
 170                          - (ph->p_vaddr & ~(GLRO(dl_pagesize) - 1)));
 171             newp->start = ((ph->p_vaddr & ~(GLRO(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                 _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              const struct r_found_version *v = NULL;                          \
 217              int flags = DL_LOOKUP_ADD_DEPENDENCY;                            \
 218              if ((version) != NULL && (version)->hash != 0)                   \
 219                {                                                              \
 220                  v = (version);                                               \
 221                  flags = 0;                                                   \
 222                }                                                              \
 223              _lr = _dl_lookup_symbol_x (strtab + (*ref)->st_name, l, (ref),   \
 224                                         scope, v, _tc, flags, NULL);          \
 225              l->l_lookup_cache.ret = (*ref);                                  \
 226              l->l_lookup_cache.value = _lr; }))                               \
 227      : l)
 228 #define RESOLVE(ref, version, r_type) \
 229     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 230      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 231          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 232                 ? (bump_num_cache_relocations (),                             \
 233            (*ref) = l->l_lookup_cache.ret,                                    \
 234            l->l_lookup_cache.value)                                           \
 235         : ({ lookup_t _lr;                                                    \
 236              int _tc = elf_machine_type_class (r_type);                       \
 237              l->l_lookup_cache.type_class = _tc;                              \
 238              l->l_lookup_cache.sym = (*ref);                                  \
 239              const struct r_found_version *v = NULL;                          \
 240              int flags = DL_LOOKUP_ADD_DEPENDENCY;                            \
 241              if ((version) != NULL && (version)->hash != 0)                   \
 242                {                                                              \
 243                  v = (version);                                               \
 244                  flags = 0;                                                   \
 245                }                                                              \
 246              _lr = _dl_lookup_symbol_x (strtab + (*ref)->st_name, l, (ref),   \
 247                                         scope, v, _tc, flags, NULL);          \
 248              l->l_lookup_cache.ret = (*ref);                                  \
 249              l->l_lookup_cache.value = _lr; }))                               \
 250      : l->l_addr)
 251
 252     /* This macro is used as a callback from elf_machine_rel{a,} when a
 253        static TLS reloc is about to be performed.  Since (in dl-load.c) we
 254        permit dynamic loading of objects that might use such relocs, we
 255        have to check whether each use is actually doable.  If the object
 256        whose TLS segment the reference resolves to was allocated space in
 257        the static TLS block at startup, then it's ok.  Otherwise, we make
 258        an attempt to allocate it in surplus space on the fly.  If that
 259        can't be done, we fall back to the error that DF_STATIC_TLS is
 260        intended to produce.  */
 261 #define CHECK_STATIC_TLS(map, sym_map)                                        \
 262     do {                                                                      \
 263       if (__builtin_expect ((sym_map)->l_tls_offset == NO_TLS_OFFSET, 0))     \
 264         _dl_allocate_static_tls (sym_map);                                    \
 265     } while (0)
 266
 267 #include "dynamic-link.h"
 268
 269     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling);
 270
 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: profiler found no PLTREL 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 =
 287           (ElfW(Addr) *) calloc (sizeof (ElfW(Addr)),
 288                                  l->l_info[DT_PLTRELSZ]->d_un.d_val);
 289         if (l->l_reloc_result == NULL)
 290           {
 291             errstring = N_("\
 292 %s: profiler out of memory shadowing PLTREL of %s\n");
 293             goto fatal;
 294           }
 295       }
 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 }