elf/do-rel.h

   1 /* Do relocations for ELF dynamic linking.
   2    Copyright (C) 1995-2020 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, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 /* This file may be included twice, to define both
  20    `elf_dynamic_do_rel' and `elf_dynamic_do_rela'.  */
  21
  22 #ifdef DO_RELA
  23 # define elf_dynamic_do_Rel             elf_dynamic_do_Rela
  24 # define Rel                            Rela
  25 # define elf_machine_rel                elf_machine_rela
  26 # define elf_machine_rel_relative       elf_machine_rela_relative
  27 #endif
  28
  29 #ifndef DO_ELF_MACHINE_REL_RELATIVE
  30 # define DO_ELF_MACHINE_REL_RELATIVE(map, l_addr, relative) \
  31   elf_machine_rel_relative (l_addr, relative,                                 \
  32                             (void *) (l_addr + relative->r_offset))
  33 #endif
  34
  35 /* Perform the relocations in MAP on the running program image as specified
  36    by RELTAG, SZTAG.  If LAZY is nonzero, this is the first pass on PLT
  37    relocations; they should be set up to call _dl_runtime_resolve, rather
  38    than fully resolved now.  */
  39
  40 auto inline void __attribute__ ((always_inline))
  41 elf_dynamic_do_Rel (struct link_map *map,
  42                     ElfW(Addr) reladdr, ElfW(Addr) relsize,
  43                     __typeof (((ElfW(Dyn) *) 0)->d_un.d_val) nrelative,
  44                     int lazy, int skip_ifunc)
  45 {
  46   const ElfW(Rel) *r = (const void *) reladdr;
  47   const ElfW(Rel) *end = (const void *) (reladdr + relsize);
  48   ElfW(Addr) l_addr = map->l_addr;
  49 # if defined ELF_MACHINE_IRELATIVE && !defined RTLD_BOOTSTRAP
  50   const ElfW(Rel) *r2 = NULL;
  51   const ElfW(Rel) *end2 = NULL;
  52 # endif
  53
  54 #if (!defined DO_RELA || !defined ELF_MACHINE_PLT_REL) && !defined RTLD_BOOTSTRAP
  55   /* We never bind lazily during ld.so bootstrap.  Unfortunately gcc is
  56      not clever enough to see through all the function calls to realize
  57      that.  */
  58   if (lazy)
  59     {
  60       /* Doing lazy PLT relocations; they need very little info.  */
  61       for (; r < end; ++r)
  62 # ifdef ELF_MACHINE_IRELATIVE
  63         if (ELFW(R_TYPE) (r->r_info) == ELF_MACHINE_IRELATIVE)
  64           {
  65             if (r2 == NULL)
  66               r2 = r;
  67             end2 = r;
  68           }
  69         else
  70 # endif
  71           elf_machine_lazy_rel (map, l_addr, r, skip_ifunc);
  72
  73 # ifdef ELF_MACHINE_IRELATIVE
  74       if (r2 != NULL)
  75         for (; r2 <= end2; ++r2)
  76           if (ELFW(R_TYPE) (r2->r_info) == ELF_MACHINE_IRELATIVE)
  77             elf_machine_lazy_rel (map, l_addr, r2, skip_ifunc);
  78 # endif
  79     }
  80   else
  81 #endif
  82     {
  83       const ElfW(Sym) *const symtab =
  84         (const void *) D_PTR (map, l_info[DT_SYMTAB]);
  85       const ElfW(Rel) *relative = r;
  86       r += nrelative;
  87
  88 #ifndef RTLD_BOOTSTRAP
  89       /* This is defined in rtld.c, but nowhere in the static libc.a; make
  90          the reference weak so static programs can still link.  This
  91          declaration cannot be done when compiling rtld.c (i.e. #ifdef
  92          RTLD_BOOTSTRAP) because rtld.c contains the common defn for
  93          _dl_rtld_map, which is incompatible with a weak decl in the same
  94          file.  */
  95 # ifndef SHARED
  96       weak_extern (GL(dl_rtld_map));
  97 # endif
  98       if (map != &GL(dl_rtld_map)) /* Already done in rtld itself.  */
  99 # if !defined DO_RELA || defined ELF_MACHINE_REL_RELATIVE
 100         /* Rela platforms get the offset from r_addend and this must
 101            be copied in the relocation address.  Therefore we can skip
 102            the relative relocations only if this is for rel
 103            relocations or rela relocations if they are computed as
 104            memory_loc += l_addr...  */
 105         if (l_addr != 0)
 106 # else
 107         /* ...or we know the object has been prelinked.  */
 108         if (l_addr != 0 || ! map->l_info[VALIDX(DT_GNU_PRELINKED)])
 109 # endif
 110 #endif
 111           for (; relative < r; ++relative)
 112             DO_ELF_MACHINE_REL_RELATIVE (map, l_addr, relative);
 113
 114 #ifdef RTLD_BOOTSTRAP
 115       /* The dynamic linker always uses versioning.  */
 116       assert (map->l_info[VERSYMIDX (DT_VERSYM)] != NULL);
 117 #else
 118       if (map->l_info[VERSYMIDX (DT_VERSYM)])
 119 #endif
 120         {
 121           const ElfW(Half) *const version =
 122             (const void *) D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);
 123
 124           for (; r < end; ++r)
 125             {
 126 #if defined ELF_MACHINE_IRELATIVE && !defined RTLD_BOOTSTRAP
 127               if (ELFW(R_TYPE) (r->r_info) == ELF_MACHINE_IRELATIVE)
 128                 {
 129                   if (r2 == NULL)
 130                     r2 = r;
 131                   end2 = r;
 132                   continue;
 133                 }
 134 #endif
 135
 136               ElfW(Half) ndx = version[ELFW(R_SYM) (r->r_info)] & 0x7fff;
 137               elf_machine_rel (map, r, &symtab[ELFW(R_SYM) (r->r_info)],
 138                                &map->l_versions[ndx],
 139                                (void *) (l_addr + r->r_offset), skip_ifunc);
 140             }
 141
 142 #if defined ELF_MACHINE_IRELATIVE && !defined RTLD_BOOTSTRAP
 143           if (r2 != NULL)
 144             for (; r2 <= end2; ++r2)
 145               if (ELFW(R_TYPE) (r2->r_info) == ELF_MACHINE_IRELATIVE)
 146                 {
 147                   ElfW(Half) ndx
 148                     = version[ELFW(R_SYM) (r2->r_info)] & 0x7fff;
 149                   elf_machine_rel (map, r2,
 150                                    &symtab[ELFW(R_SYM) (r2->r_info)],
 151                                    &map->l_versions[ndx],
 152                                    (void *) (l_addr + r2->r_offset),
 153                                    skip_ifunc);
 154                 }
 155 #endif
 156         }
 157 #ifndef RTLD_BOOTSTRAP
 158       else
 159         {
 160           for (; r < end; ++r)
 161 # ifdef ELF_MACHINE_IRELATIVE
 162             if (ELFW(R_TYPE) (r->r_info) == ELF_MACHINE_IRELATIVE)
 163               {
 164                 if (r2 == NULL)
 165                   r2 = r;
 166                 end2 = r;
 167               }
 168             else
 169 # endif
 170               elf_machine_rel (map, r, &symtab[ELFW(R_SYM) (r->r_info)], NULL,
 171                                (void *) (l_addr + r->r_offset), skip_ifunc);
 172
 173 # ifdef ELF_MACHINE_IRELATIVE
 174           if (r2 != NULL)
 175             for (; r2 <= end2; ++r2)
 176               if (ELFW(R_TYPE) (r2->r_info) == ELF_MACHINE_IRELATIVE)
 177                 elf_machine_rel (map, r2, &symtab[ELFW(R_SYM) (r2->r_info)],
 178                                  NULL, (void *) (l_addr + r2->r_offset),
 179                                  skip_ifunc);
 180 # endif
 181         }
 182 #endif
 183     }
 184 }
 185
 186 #undef elf_dynamic_do_Rel
 187 #undef Rel
 188 #undef elf_machine_rel
 189 #undef elf_machine_rel_relative
 190 #undef DO_ELF_MACHINE_REL_RELATIVE
 191 #undef DO_RELA