elf/dynamic-link.h

   1 /* Inline functions for dynamic linking.
   2    Copyright (C) 1995-2018 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    <http://www.gnu.org/licenses/>.  */
  18
  19 /* This macro is used as a callback from elf_machine_rel{a,} when a
  20    static TLS reloc is about to be performed.  Since (in dl-load.c) we
  21    permit dynamic loading of objects that might use such relocs, we
  22    have to check whether each use is actually doable.  If the object
  23    whose TLS segment the reference resolves to was allocated space in
  24    the static TLS block at startup, then it's ok.  Otherwise, we make
  25    an attempt to allocate it in surplus space on the fly.  If that
  26    can't be done, we fall back to the error that DF_STATIC_TLS is
  27    intended to produce.  */
  28 #define HAVE_STATIC_TLS(map, sym_map)                                   \
  29     (__builtin_expect ((sym_map)->l_tls_offset != NO_TLS_OFFSET         \
  30                        && ((sym_map)->l_tls_offset                      \
  31                            != FORCED_DYNAMIC_TLS_OFFSET), 1))
  32
  33 #define CHECK_STATIC_TLS(map, sym_map)                                  \
  34     do {                                                                \
  35       if (!HAVE_STATIC_TLS (map, sym_map))                              \
  36         _dl_allocate_static_tls (sym_map);                              \
  37     } while (0)
  38
  39 #define TRY_STATIC_TLS(map, sym_map)                                    \
  40     (__builtin_expect ((sym_map)->l_tls_offset                          \
  41                        != FORCED_DYNAMIC_TLS_OFFSET, 1)                 \
  42      && (__builtin_expect ((sym_map)->l_tls_offset != NO_TLS_OFFSET, 1) \
  43          || _dl_try_allocate_static_tls (sym_map) == 0))
  44
  45 int _dl_try_allocate_static_tls (struct link_map *map) attribute_hidden;
  46
  47 #include <elf.h>
  48
  49 #ifdef RESOLVE_MAP
  50 /* We pass reloc_addr as a pointer to void, as opposed to a pointer to
  51    ElfW(Addr), because not all architectures can assume that the
  52    relocated address is properly aligned, whereas the compiler is
  53    entitled to assume that a pointer to a type is properly aligned for
  54    the type.  Even if we cast the pointer back to some other type with
  55    less strict alignment requirements, the compiler might still
  56    remember that the pointer was originally more aligned, thereby
  57    optimizing away alignment tests or using word instructions for
  58    copying memory, breaking the very code written to handle the
  59    unaligned cases.  */
  60 # if ! ELF_MACHINE_NO_REL
  61 auto inline void __attribute__((always_inline))
  62 elf_machine_rel (struct link_map *map, const ElfW(Rel) *reloc,
  63                  const ElfW(Sym) *sym, const struct r_found_version *version,
  64                  void *const reloc_addr, int skip_ifunc);
  65 auto inline void __attribute__((always_inline))
  66 elf_machine_rel_relative (ElfW(Addr) l_addr, const ElfW(Rel) *reloc,
  67                           void *const reloc_addr);
  68 # endif
  69 # if ! ELF_MACHINE_NO_RELA
  70 auto inline void __attribute__((always_inline))
  71 elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
  72                   const ElfW(Sym) *sym, const struct r_found_version *version,
  73                   void *const reloc_addr, int skip_ifunc);
  74 auto inline void __attribute__((always_inline))
  75 elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
  76                            void *const reloc_addr);
  77 # endif
  78 # if ELF_MACHINE_NO_RELA || defined ELF_MACHINE_PLT_REL
  79 auto inline void __attribute__((always_inline))
  80 elf_machine_lazy_rel (struct link_map *map,
  81                       ElfW(Addr) l_addr, const ElfW(Rel) *reloc,
  82                       int skip_ifunc);
  83 # else
  84 auto inline void __attribute__((always_inline))
  85 elf_machine_lazy_rel (struct link_map *map,
  86                       ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
  87                       int skip_ifunc);
  88 # endif
  89 #endif
  90
  91 #include <dl-machine.h>
  92
  93 #include "get-dynamic-info.h"
  94
  95 #ifdef RESOLVE_MAP
  96
  97 # if defined RTLD_BOOTSTRAP || defined STATIC_PIE_BOOTSTRAP
  98 #  define ELF_DURING_STARTUP (1)
  99 # else
 100 #  define ELF_DURING_STARTUP (0)
 101 # endif
 102
 103 /* Get the definitions of `elf_dynamic_do_rel' and `elf_dynamic_do_rela'.
 104    These functions are almost identical, so we use cpp magic to avoid
 105    duplicating their code.  It cannot be done in a more general function
 106    because we must be able to completely inline.  */
 107
 108 /* On some machines, notably SPARC, DT_REL* includes DT_JMPREL in its
 109    range.  Note that according to the ELF spec, this is completely legal!
 110
 111    We are guarenteed that we have one of three situations.  Either DT_JMPREL
 112    comes immediately after DT_REL*, or there is overlap and DT_JMPREL
 113    consumes precisely the very end of the DT_REL*, or DT_JMPREL and DT_REL*
 114    are completely separate and there is a gap between them.  */
 115
 116 # define _ELF_DYNAMIC_DO_RELOC(RELOC, reloc, map, do_lazy, skip_ifunc, test_rel) \
 117   do {                                                                        \
 118     struct { ElfW(Addr) start, size;                                          \
 119              __typeof (((ElfW(Dyn) *) 0)->d_un.d_val) nrelative; int lazy; }  \
 120       ranges[2] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 } };                         \
 121                                                                               \
 122     if ((map)->l_info[DT_##RELOC])                                            \
 123       {                                                                       \
 124         ranges[0].start = D_PTR ((map), l_info[DT_##RELOC]);                  \
 125         ranges[0].size = (map)->l_info[DT_##RELOC##SZ]->d_un.d_val;           \
 126         if (map->l_info[VERSYMIDX (DT_##RELOC##COUNT)] != NULL)               \
 127           ranges[0].nrelative                                                 \
 128             = map->l_info[VERSYMIDX (DT_##RELOC##COUNT)]->d_un.d_val;         \
 129       }                                                                       \
 130     if ((map)->l_info[DT_PLTREL]                                              \
 131         && (!test_rel || (map)->l_info[DT_PLTREL]->d_un.d_val == DT_##RELOC)) \
 132       {                                                                       \
 133         ElfW(Addr) start = D_PTR ((map), l_info[DT_JMPREL]);                  \
 134         ElfW(Addr) size = (map)->l_info[DT_PLTRELSZ]->d_un.d_val;             \
 135                                                                               \
 136         if (ranges[0].start + ranges[0].size == (start + size))               \
 137           ranges[0].size -= size;                                             \
 138         if (ELF_DURING_STARTUP                                                \
 139             || (!(do_lazy)                                                    \
 140                 && (ranges[0].start + ranges[0].size) == start))              \
 141           {                                                                   \
 142             /* Combine processing the sections.  */                           \
 143             ranges[0].size += size;                                           \
 144           }                                                                   \
 145         else                                                                  \
 146           {                                                                   \
 147             ranges[1].start = start;                                          \
 148             ranges[1].size = size;                                            \
 149             ranges[1].lazy = (do_lazy);                                       \
 150           }                                                                   \
 151       }                                                                       \
 152                                                                               \
 153     if (ELF_DURING_STARTUP)                                                   \
 154       elf_dynamic_do_##reloc ((map), ranges[0].start, ranges[0].size,         \
 155                               ranges[0].nrelative, 0, skip_ifunc);            \
 156     else                                                                      \
 157       {                                                                       \
 158         int ranges_index;                                                     \
 159         for (ranges_index = 0; ranges_index < 2; ++ranges_index)              \
 160           elf_dynamic_do_##reloc ((map),                                      \
 161                                   ranges[ranges_index].start,                 \
 162                                   ranges[ranges_index].size,                  \
 163                                   ranges[ranges_index].nrelative,             \
 164                                   ranges[ranges_index].lazy,                  \
 165                                   skip_ifunc);                                \
 166       }                                                                       \
 167   } while (0)
 168
 169 # if ELF_MACHINE_NO_REL || ELF_MACHINE_NO_RELA
 170 #  define _ELF_CHECK_REL 0
 171 # else
 172 #  define _ELF_CHECK_REL 1
 173 # endif
 174
 175 # if ! ELF_MACHINE_NO_REL
 176 #  include "do-rel.h"
 177 #  define ELF_DYNAMIC_DO_REL(map, lazy, skip_ifunc) \
 178   _ELF_DYNAMIC_DO_RELOC (REL, Rel, map, lazy, skip_ifunc, _ELF_CHECK_REL)
 179 # else
 180 #  define ELF_DYNAMIC_DO_REL(map, lazy, skip_ifunc) /* Nothing to do.  */
 181 # endif
 182
 183 # if ! ELF_MACHINE_NO_RELA
 184 #  define DO_RELA
 185 #  include "do-rel.h"
 186 #  define ELF_DYNAMIC_DO_RELA(map, lazy, skip_ifunc) \
 187   _ELF_DYNAMIC_DO_RELOC (RELA, Rela, map, lazy, skip_ifunc, _ELF_CHECK_REL)
 188 # else
 189 #  define ELF_DYNAMIC_DO_RELA(map, lazy, skip_ifunc) /* Nothing to do.  */
 190 # endif
 191
 192 /* This can't just be an inline function because GCC is too dumb
 193    to inline functions containing inlines themselves.  */
 194 # define ELF_DYNAMIC_RELOCATE(map, lazy, consider_profile, skip_ifunc) \
 195   do {                                                                        \
 196     int edr_lazy = elf_machine_runtime_setup ((map), (lazy),                  \
 197                                               (consider_profile));            \
 198     ELF_DYNAMIC_DO_REL ((map), edr_lazy, skip_ifunc);                         \
 199     ELF_DYNAMIC_DO_RELA ((map), edr_lazy, skip_ifunc);                        \
 200   } while (0)
 201
 202 #endif