elf/dynamic-link.h

   1 /* Inline functions for dynamic linking.
   2    Copyright (C) 1995-2021 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 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, true) == 0))
  44
  45 int _dl_try_allocate_static_tls (struct link_map *map, bool optional)
  46   attribute_hidden;
  47
  48 #include <elf.h>
  49
  50 #ifdef RESOLVE_MAP
  51 /* We pass reloc_addr as a pointer to void, as opposed to a pointer to
  52    ElfW(Addr), because not all architectures can assume that the
  53    relocated address is properly aligned, whereas the compiler is
  54    entitled to assume that a pointer to a type is properly aligned for
  55    the type.  Even if we cast the pointer back to some other type with
  56    less strict alignment requirements, the compiler might still
  57    remember that the pointer was originally more aligned, thereby
  58    optimizing away alignment tests or using word instructions for
  59    copying memory, breaking the very code written to handle the
  60    unaligned cases.  */
  61 # if ! ELF_MACHINE_NO_REL
  62 auto inline void __attribute__((always_inline))
  63 elf_machine_rel (struct link_map *map, const ElfW(Rel) *reloc,
  64                  const ElfW(Sym) *sym, const struct r_found_version *version,
  65                  void *const reloc_addr, int skip_ifunc);
  66 auto inline void __attribute__((always_inline))
  67 elf_machine_rel_relative (ElfW(Addr) l_addr, const ElfW(Rel) *reloc,
  68                           void *const reloc_addr);
  69 # endif
  70 # if ! ELF_MACHINE_NO_RELA
  71 auto inline void __attribute__((always_inline))
  72 elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
  73                   const ElfW(Sym) *sym, const struct r_found_version *version,
  74                   void *const reloc_addr, int skip_ifunc);
  75 auto inline void __attribute__((always_inline))
  76 elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
  77                            void *const reloc_addr);
  78 # endif
  79 # if ELF_MACHINE_NO_RELA || defined ELF_MACHINE_PLT_REL
  80 auto inline void __attribute__((always_inline))
  81 elf_machine_lazy_rel (struct link_map *map,
  82                       ElfW(Addr) l_addr, const ElfW(Rel) *reloc,
  83                       int skip_ifunc);
  84 # else
  85 auto inline void __attribute__((always_inline))
  86 elf_machine_lazy_rel (struct link_map *map,
  87                       ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
  88                       int skip_ifunc);
  89 # endif
  90 #endif
  91
  92 #include <dl-machine.h>
  93
  94 #include "get-dynamic-info.h"
  95
  96 #ifdef RESOLVE_MAP
  97
  98 # if defined RTLD_BOOTSTRAP || defined STATIC_PIE_BOOTSTRAP
  99 #  define ELF_DURING_STARTUP (1)
 100 # else
 101 #  define ELF_DURING_STARTUP (0)
 102 # endif
 103
 104 /* Get the definitions of `elf_dynamic_do_rel' and `elf_dynamic_do_rela'.
 105    These functions are almost identical, so we use cpp magic to avoid
 106    duplicating their code.  It cannot be done in a more general function
 107    because we must be able to completely inline.  */
 108
 109 /* On some machines, notably SPARC, DT_REL* includes DT_JMPREL in its
 110    range.  Note that according to the ELF spec, this is completely legal!
 111
 112    We are guarenteed that we have one of three situations.  Either DT_JMPREL
 113    comes immediately after DT_REL*, or there is overlap and DT_JMPREL
 114    consumes precisely the very end of the DT_REL*, or DT_JMPREL and DT_REL*
 115    are completely separate and there is a gap between them.  */
 116
 117 # define _ELF_DYNAMIC_DO_RELOC(RELOC, reloc, map, do_lazy, skip_ifunc, test_rel) \
 118   do {                                                                        \
 119     struct { ElfW(Addr) start, size;                                          \
 120              __typeof (((ElfW(Dyn) *) 0)->d_un.d_val) nrelative; int lazy; }  \
 121       ranges[2] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 } };                         \
 122                                                                               \
 123     if ((map)->l_info[DT_##RELOC])                                            \
 124       {                                                                       \
 125         ranges[0].start = D_PTR ((map), l_info[DT_##RELOC]);                  \
 126         ranges[0].size = (map)->l_info[DT_##RELOC##SZ]->d_un.d_val;           \
 127         if (map->l_info[VERSYMIDX (DT_##RELOC##COUNT)] != NULL)               \
 128           ranges[0].nrelative                                                 \
 129             = map->l_info[VERSYMIDX (DT_##RELOC##COUNT)]->d_un.d_val;         \
 130       }                                                                       \
 131     if ((map)->l_info[DT_PLTREL]                                              \
 132         && (!test_rel || (map)->l_info[DT_PLTREL]->d_un.d_val == DT_##RELOC)) \
 133       {                                                                       \
 134         ElfW(Addr) start = D_PTR ((map), l_info[DT_JMPREL]);                  \
 135         ElfW(Addr) size = (map)->l_info[DT_PLTRELSZ]->d_un.d_val;             \
 136                                                                               \
 137         if (ranges[0].start + ranges[0].size == (start + size))               \
 138           ranges[0].size -= size;                                             \
 139         if (ELF_DURING_STARTUP                                                \
 140             || (!(do_lazy)                                                    \
 141                 && (ranges[0].start + ranges[0].size) == start))              \
 142           {                                                                   \
 143             /* Combine processing the sections.  */                           \
 144             ranges[0].size += size;                                           \
 145           }                                                                   \
 146         else                                                                  \
 147           {                                                                   \
 148             ranges[1].start = start;                                          \
 149             ranges[1].size = size;                                            \
 150             ranges[1].lazy = (do_lazy);                                       \
 151           }                                                                   \
 152       }                                                                       \
 153                                                                               \
 154     if (ELF_DURING_STARTUP)                                                   \
 155       elf_dynamic_do_##reloc ((map), ranges[0].start, ranges[0].size,         \
 156                               ranges[0].nrelative, 0, skip_ifunc);            \
 157     else                                                                      \
 158       {                                                                       \
 159         int ranges_index;                                                     \
 160         for (ranges_index = 0; ranges_index < 2; ++ranges_index)              \
 161           elf_dynamic_do_##reloc ((map),                                      \
 162                                   ranges[ranges_index].start,                 \
 163                                   ranges[ranges_index].size,                  \
 164                                   ranges[ranges_index].nrelative,             \
 165                                   ranges[ranges_index].lazy,                  \
 166                                   skip_ifunc);                                \
 167       }                                                                       \
 168   } while (0)
 169
 170 # if ELF_MACHINE_NO_REL || ELF_MACHINE_NO_RELA
 171 #  define _ELF_CHECK_REL 0
 172 # else
 173 #  define _ELF_CHECK_REL 1
 174 # endif
 175
 176 # if ! ELF_MACHINE_NO_REL
 177 #  include "do-rel.h"
 178 #  define ELF_DYNAMIC_DO_REL(map, lazy, skip_ifunc) \
 179   _ELF_DYNAMIC_DO_RELOC (REL, Rel, map, lazy, skip_ifunc, _ELF_CHECK_REL)
 180 # else
 181 #  define ELF_DYNAMIC_DO_REL(map, lazy, skip_ifunc) /* Nothing to do.  */
 182 # endif
 183
 184 # if ! ELF_MACHINE_NO_RELA
 185 #  define DO_RELA
 186 #  include "do-rel.h"
 187 #  define ELF_DYNAMIC_DO_RELA(map, lazy, skip_ifunc) \
 188   _ELF_DYNAMIC_DO_RELOC (RELA, Rela, map, lazy, skip_ifunc, _ELF_CHECK_REL)
 189 # else
 190 #  define ELF_DYNAMIC_DO_RELA(map, lazy, skip_ifunc) /* Nothing to do.  */
 191 # endif
 192
 193 /* This can't just be an inline function because GCC is too dumb
 194    to inline functions containing inlines themselves.  */
 195 # define ELF_DYNAMIC_RELOCATE(map, lazy, consider_profile, skip_ifunc) \
 196   do {                                                                        \
 197     int edr_lazy = elf_machine_runtime_setup ((map), (lazy),                  \
 198                                               (consider_profile));            \
 199     ELF_DYNAMIC_DO_REL ((map), edr_lazy, skip_ifunc);                         \
 200     ELF_DYNAMIC_DO_RELA ((map), edr_lazy, skip_ifunc);                        \
 201   } while (0)
 202
 203 #endif