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 void
  45 internal_function __attribute_noinline__
  46 _dl_allocate_static_tls (struct link_map *map)
  47 {
  48   size_t offset;
  49   size_t used;
  50   size_t check;
  51
  52 # if TLS_TCB_AT_TP
  53   offset = roundup (GL(dl_tls_static_used) + map->l_tls_blocksize,
  54                     map->l_tls_align);
  55   used = offset;
  56   check = offset + TLS_TCB_SIZE;
  57 # elif TLS_DTV_AT_TP
  58   offset = roundup (GL(dl_tls_static_used), map->l_tls_align);
  59   used = offset + map->l_tls_blocksize;
  60   check = used;
  61   /* dl_tls_static_used includes the TCB at the beginning.  */
  62 # else
  63 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
  64 # endif
  65
  66   if (check > GL(dl_tls_static_size))
  67     {
  68       const char *errstring = N_("\
  69 shared object cannot be dlopen()ed: static TLS memory too small");
  70       INTUSE(_dl_signal_error) (0, (map)->l_name, NULL, errstring);
  71     }
  72
  73   map->l_tls_offset = offset;
  74   GL(dl_tls_static_used) = used;
  75 }
  76 #endif
  77
  78
  79 void
  80 _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
  81                      int lazy, int consider_profiling)
  82 {
  83   struct textrels
  84   {
  85     caddr_t start;
  86     size_t len;
  87     int prot;
  88     struct textrels *next;
  89   } *textrels = NULL;
  90   /* Initialize it to make the compiler happy.  */
  91   const char *errstring = NULL;
  92
  93   if (l->l_relocated)
  94     return;
  95
  96   /* If DT_BIND_NOW is set relocate all references in this object.  We
  97      do not do this if we are profiling, of course.  */
  98   if (!consider_profiling
  99       && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
 100     lazy = 0;
 101
 102   if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_RELOC, 0))
 103     INTUSE(_dl_debug_printf) ("\nrelocation processing: %s%s\n",
 104                               l->l_name[0] ? l->l_name : rtld_progname,
 105                               lazy ? " (lazy)" : "");
 106
 107   /* DT_TEXTREL is now in level 2 and might phase out at some time.
 108      But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
 109      testing easier and therefore it will be available at all time.  */
 110   if (__builtin_expect (l->l_info[DT_TEXTREL] != NULL, 0))
 111     {
 112       /* Bletch.  We must make read-only segments writable
 113          long enough to relocate them.  */
 114       const ElfW(Phdr) *ph;
 115       for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
 116         if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
 117           {
 118             struct textrels *newp;
 119
 120             newp = (struct textrels *) alloca (sizeof (*newp));
 121             newp->len = (((ph->p_vaddr + ph->p_memsz + GL(dl_pagesize) - 1)
 122                           & ~(GL(dl_pagesize) - 1))
 123                          - (ph->p_vaddr & ~(GL(dl_pagesize) - 1)));
 124             newp->start = ((ph->p_vaddr & ~(GL(dl_pagesize) - 1))
 125                            + (caddr_t) l->l_addr);
 126
 127             if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
 128               {
 129                 errstring = N_("cannot make segment writable for relocation");
 130               call_error:
 131                 INTUSE(_dl_signal_error) (errno, l->l_name, NULL, errstring);
 132               }
 133
 134 #if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
 135             newp->prot = (PF_TO_PROT
 136                           >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
 137 #else
 138             newp->prot = 0;
 139             if (ph->p_flags & PF_R)
 140               newp->prot |= PROT_READ;
 141             if (ph->p_flags & PF_W)
 142               newp->prot |= PROT_WRITE;
 143             if (ph->p_flags & PF_X)
 144               newp->prot |= PROT_EXEC;
 145 #endif
 146             newp->next = textrels;
 147             textrels = newp;
 148           }
 149     }
 150
 151   {
 152     /* Do the actual relocation of the object's GOT and other data.  */
 153
 154     /* String table object symbols.  */
 155     const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
 156
 157     /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
 158 #define RESOLVE_MAP(ref, version, r_type) \
 159     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 160      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 161          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 162         ? (bump_num_cache_relocations (),                                     \
 163            (*ref) = l->l_lookup_cache.ret,                                    \
 164            l->l_lookup_cache.value)                                           \
 165         : ({ lookup_t _lr;                                                    \
 166              int _tc = elf_machine_type_class (r_type);                       \
 167              l->l_lookup_cache.type_class = _tc;                              \
 168              l->l_lookup_cache.sym = (*ref);                                  \
 169              _lr = ((version) != NULL && (version)->hash != 0                 \
 170                     ? INTUSE(_dl_lookup_versioned_symbol) (strtab             \
 171                                                            + (*ref)->st_name, \
 172                                                            l, (ref), scope,   \
 173                                                            (version), _tc, 0) \
 174                     : INTUSE(_dl_lookup_symbol) (strtab + (*ref)->st_name, l, \
 175                                                  (ref), scope, _tc,           \
 176                                                  DL_LOOKUP_ADD_DEPENDENCY));  \
 177              l->l_lookup_cache.ret = (*ref);                                  \
 178              l->l_lookup_cache.value = _lr; }))                               \
 179      : l)
 180 #define RESOLVE(ref, version, r_type) \
 181     (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL                             \
 182      ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0)                \
 183          && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)  \
 184                 ? (bump_num_cache_relocations (),                             \
 185            (*ref) = l->l_lookup_cache.ret,                                    \
 186            l->l_lookup_cache.value)                                           \
 187         : ({ lookup_t _lr;                                                    \
 188              int _tc = elf_machine_type_class (r_type);                       \
 189              l->l_lookup_cache.type_class = _tc;                              \
 190              l->l_lookup_cache.sym = (*ref);                                  \
 191              _lr = ((version) != NULL && (version)->hash != 0                 \
 192                     ? INTUSE(_dl_lookup_versioned_symbol) (strtab             \
 193                                                            + (*ref)->st_name, \
 194                                                            l, (ref), scope,   \
 195                                                            (version), _tc, 0) \
 196                     : INTUSE(_dl_lookup_symbol) (strtab + (*ref)->st_name, l, \
 197                                                  (ref), scope, _tc,           \
 198                                                  DL_LOOKUP_ADD_DEPENDENCY));  \
 199              l->l_lookup_cache.ret = (*ref);                                  \
 200              l->l_lookup_cache.value = _lr; }))                               \
 201      : l->l_addr)
 202
 203     /* This macro is used as a callback from elf_machine_rel{a,} when a
 204        static TLS reloc is about to be performed.  Since (in dl-load.c) we
 205        permit dynamic loading of objects that might use such relocs, we
 206        have to check whether each use is actually doable.  If the object
 207        whose TLS segment the reference resolves to was allocated space in
 208        the static TLS block at startup, then it's ok.  Otherwise, we make
 209        an attempt to allocate it in surplus space on the fly.  If that
 210        can't be done, we fall back to the error that DF_STATIC_TLS is
 211        intended to produce.  */
 212 #define CHECK_STATIC_TLS(map, sym_map)                                        \
 213     do {                                                                      \
 214       if (__builtin_expect ((sym_map)->l_tls_offset == NO_TLS_OFFSET, 0))     \
 215         _dl_allocate_static_tls (sym_map);                                    \
 216     } while (0)
 217
 218 #include "dynamic-link.h"
 219
 220     ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling);
 221
 222     if (__builtin_expect (consider_profiling, 0))
 223       {
 224         /* Allocate the array which will contain the already found
 225            relocations.  If the shared object lacks a PLT (for example
 226            if it only contains lead function) the l_info[DT_PLTRELSZ]
 227            will be NULL.  */
 228         if (l->l_info[DT_PLTRELSZ] == NULL)
 229           {
 230             errstring = N_("%s: profiler found no PLTREL in object %s\n");
 231           fatal:
 232             _dl_fatal_printf (errstring,
 233                               rtld_progname ?: "<program name unknown>",
 234                               l->l_name);
 235           }
 236
 237         l->l_reloc_result =
 238           (ElfW(Addr) *) calloc (sizeof (ElfW(Addr)),
 239                                  l->l_info[DT_PLTRELSZ]->d_un.d_val);
 240         if (l->l_reloc_result == NULL)
 241           {
 242             errstring = N_("\
 243 %s: profiler out of memory shadowing PLTREL of %s\n");
 244             goto fatal;
 245           }
 246       }
 247   }
 248
 249   /* Mark the object so we know this work has been done.  */
 250   l->l_relocated = 1;
 251
 252   /* Undo the segment protection changes.  */
 253   while (__builtin_expect (textrels != NULL, 0))
 254     {
 255       if (__mprotect (textrels->start, textrels->len, textrels->prot) < 0)
 256         {
 257           errstring = N_("cannot restore segment prot after reloc");
 258           goto call_error;
 259         }
 260
 261       textrels = textrels->next;
 262     }
 263 }
 264 INTDEF (_dl_relocate_object)
 265
 266
 267 void
 268 internal_function __attribute_noinline__
 269 _dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
 270 {
 271   extern const char INTUSE(_itoa_lower_digits)[] attribute_hidden;
 272 #define DIGIT(b)        INTUSE(_itoa_lower_digits)[(b) & 0xf];
 273
 274   /* XXX We cannot translate these messages.  */
 275   static const char msg[2][32
 276 #if __ELF_NATIVE_CLASS == 64
 277                            + 6
 278 #endif
 279   ] = { "unexpected reloc type 0x",
 280         "unexpected PLT reloc type 0x" };
 281   char msgbuf[sizeof (msg[0])];
 282   char *cp;
 283
 284   cp = __stpcpy (msgbuf, msg[plt]);
 285 #if __ELF_NATIVE_CLASS == 64
 286   if (__builtin_expect(type > 0xff, 0))
 287     {
 288       *cp++ = DIGIT (type >> 28);
 289       *cp++ = DIGIT (type >> 24);
 290       *cp++ = DIGIT (type >> 20);
 291       *cp++ = DIGIT (type >> 16);
 292       *cp++ = DIGIT (type >> 12);
 293       *cp++ = DIGIT (type >> 8);
 294     }
 295 #endif
 296   *cp++ = DIGIT (type >> 4);
 297   *cp++ = DIGIT (type);
 298   *cp = '\0';
 299
 300   INTUSE(_dl_signal_error) (0, map->l_name, NULL, msgbuf);
 301 }