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