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