elf/dynamic-link.h

   1 /* Inline functions for dynamic linking.
   2    Copyright (C) 1995-2023 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 #include <dl-machine.h>
  20 #include <elf.h>
  21
  22 #ifdef RESOLVE_MAP
  23 /* We pass reloc_addr as a pointer to void, as opposed to a pointer to
  24    ElfW(Addr), because not all architectures can assume that the
  25    relocated address is properly aligned, whereas the compiler is
  26    entitled to assume that a pointer to a type is properly aligned for
  27    the type.  Even if we cast the pointer back to some other type with
  28    less strict alignment requirements, the compiler might still
  29    remember that the pointer was originally more aligned, thereby
  30    optimizing away alignment tests or using word instructions for
  31    copying memory, breaking the very code written to handle the
  32    unaligned cases.  */
  33 # if ! ELF_MACHINE_NO_REL
  34 static inline void __attribute__((always_inline))
  35 elf_machine_rel (struct link_map *map, struct r_scope_elem *scope[],
  36                  const ElfW(Rel) *reloc, const ElfW(Sym) *sym,
  37                  const struct r_found_version *version,
  38                  void *const reloc_addr, int skip_ifunc);
  39 static inline void __attribute__((always_inline))
  40 elf_machine_rel_relative (ElfW(Addr) l_addr, const ElfW(Rel) *reloc,
  41                           void *const reloc_addr);
  42 # endif
  43 # if ! ELF_MACHINE_NO_RELA
  44 static inline void __attribute__((always_inline))
  45 elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
  46                   const ElfW(Rela) *reloc, const ElfW(Sym) *sym,
  47                   const struct r_found_version *version, void *const reloc_addr,
  48                   int skip_ifunc);
  49 static inline void __attribute__((always_inline))
  50 elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
  51                            void *const reloc_addr);
  52 # endif
  53 # if ELF_MACHINE_NO_RELA || defined ELF_MACHINE_PLT_REL
  54 static inline void __attribute__((always_inline))
  55 elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
  56                       ElfW(Addr) l_addr, const ElfW(Rel) *reloc,
  57                       int skip_ifunc);
  58 # else
  59 static inline void __attribute__((always_inline))
  60 elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
  61                       ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
  62                       int skip_ifunc);
  63 # endif
  64 #endif
  65
  66 #ifdef RESOLVE_MAP
  67
  68 /* Get the definitions of `elf_dynamic_do_rel' and `elf_dynamic_do_rela'.
  69    These functions are almost identical, so we use cpp magic to avoid
  70    duplicating their code.  It cannot be done in a more general function
  71    because we must be able to completely inline.  */
  72
  73 /* On some machines, notably SPARC, DT_REL* includes DT_JMPREL in its
  74    range.  Note that according to the ELF spec, this is completely legal!
  75
  76    We are guaranteed that we have one of three situations.  Either DT_JMPREL
  77    comes immediately after DT_REL*, or there is overlap and DT_JMPREL
  78    consumes precisely the very end of the DT_REL*, or DT_JMPREL and DT_REL*
  79    are completely separate and there is a gap between them.  */
  80
  81 # define _ELF_DYNAMIC_DO_RELOC(RELOC, reloc, map, scope, do_lazy, skip_ifunc, test_rel) \
  82   do {                                                                        \
  83     struct { ElfW(Addr) start, size;                                          \
  84              __typeof (((ElfW(Dyn) *) 0)->d_un.d_val) nrelative; int lazy; }  \
  85       ranges[2] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 } };                         \
  86                                                                               \
  87     /* With DT_RELR, DT_RELA/DT_REL can have zero value.  */                  \
  88     if ((map)->l_info[DT_##RELOC] != NULL                                     \
  89         && (map)->l_info[DT_##RELOC]->d_un.d_ptr != 0)                        \
  90       {                                                                       \
  91         ranges[0].start = D_PTR ((map), l_info[DT_##RELOC]);                  \
  92         ranges[0].size = (map)->l_info[DT_##RELOC##SZ]->d_un.d_val;           \
  93         if (map->l_info[VERSYMIDX (DT_##RELOC##COUNT)] != NULL)               \
  94           ranges[0].nrelative                                                 \
  95             = map->l_info[VERSYMIDX (DT_##RELOC##COUNT)]->d_un.d_val;         \
  96       }                                                                       \
  97     if ((map)->l_info[DT_PLTREL]                                              \
  98         && (!test_rel || (map)->l_info[DT_PLTREL]->d_un.d_val == DT_##RELOC)) \
  99       {                                                                       \
 100         ElfW(Addr) start = D_PTR ((map), l_info[DT_JMPREL]);                  \
 101         ElfW(Addr) size = (map)->l_info[DT_PLTRELSZ]->d_un.d_val;             \
 102                                                                               \
 103         if (ranges[0].start == 0)                                             \
 104           ranges[0].start = start;                                            \
 105         if (ranges[0].start + ranges[0].size == (start + size))               \
 106           ranges[0].size -= size;                                             \
 107         if (!(do_lazy)                                                        \
 108             && (ranges[0].start + ranges[0].size) == start)                   \
 109           {                                                                   \
 110             /* Combine processing the sections.  */                           \
 111             ranges[0].size += size;                                           \
 112           }                                                                   \
 113         else                                                                  \
 114           {                                                                   \
 115             ranges[1].start = start;                                          \
 116             ranges[1].size = size;                                            \
 117             ranges[1].lazy = (do_lazy);                                       \
 118           }                                                                   \
 119       }                                                                       \
 120                                                                               \
 121       for (int ranges_index = 0; ranges_index < 2; ++ranges_index)            \
 122         elf_dynamic_do_##reloc ((map), scope,                                 \
 123                                 ranges[ranges_index].start,                   \
 124                                 ranges[ranges_index].size,                    \
 125                                 ranges[ranges_index].nrelative,               \
 126                                 ranges[ranges_index].lazy,                    \
 127                                 skip_ifunc);                                  \
 128   } while (0)
 129
 130 # if ELF_MACHINE_NO_REL || ELF_MACHINE_NO_RELA
 131 #  define _ELF_CHECK_REL 0
 132 # else
 133 #  define _ELF_CHECK_REL 1
 134 # endif
 135
 136 # if ! ELF_MACHINE_NO_REL
 137 #  include "do-rel.h"
 138 #  define ELF_DYNAMIC_DO_REL(map, scope, lazy, skip_ifunc)            \
 139   _ELF_DYNAMIC_DO_RELOC (REL, Rel, map, scope, lazy, skip_ifunc, _ELF_CHECK_REL)
 140 # else
 141 #  define ELF_DYNAMIC_DO_REL(map, scope, lazy, skip_ifunc) /* Nothing to do.  */
 142 # endif
 143
 144 # if ! ELF_MACHINE_NO_RELA
 145 #  define DO_RELA
 146 #  include "do-rel.h"
 147 #  define ELF_DYNAMIC_DO_RELA(map, scope, lazy, skip_ifunc)           \
 148   _ELF_DYNAMIC_DO_RELOC (RELA, Rela, map, scope, lazy, skip_ifunc, _ELF_CHECK_REL)
 149 # else
 150 #  define ELF_DYNAMIC_DO_RELA(map, scope, lazy, skip_ifunc) /* Nothing to do.  */
 151 # endif
 152
 153 # define ELF_DYNAMIC_DO_RELR(map)                                             \
 154   do {                                                                        \
 155     ElfW(Addr) l_addr = (map)->l_addr, *where = 0;                            \
 156     const ElfW(Relr) *r, *end;                                                \
 157     if ((map)->l_info[DT_RELR] == NULL)                                       \
 158       break;                                                                  \
 159     r = (const ElfW(Relr) *)D_PTR((map), l_info[DT_RELR]);                    \
 160     end = (const ElfW(Relr) *)((const char *)r +                              \
 161                                (map)->l_info[DT_RELRSZ]->d_un.d_val);         \
 162     for (; r < end; r++)                                                      \
 163       {                                                                       \
 164         ElfW(Relr) entry = *r;                                                \
 165         if ((entry & 1) == 0)                                                 \
 166           {                                                                   \
 167             where = (ElfW(Addr) *)(l_addr + entry);                           \
 168             *where++ += l_addr;                                               \
 169           }                                                                   \
 170         else                                                                  \
 171           {                                                                   \
 172             for (long int i = 0; (entry >>= 1) != 0; i++)                     \
 173               if ((entry & 1) != 0)                                           \
 174                 where[i] += l_addr;                                           \
 175             where += CHAR_BIT * sizeof(ElfW(Relr)) - 1;                       \
 176           }                                                                   \
 177       }                                                                       \
 178   } while (0);
 179
 180 /* This can't just be an inline function because GCC is too dumb
 181    to inline functions containing inlines themselves.  */
 182 # ifdef RTLD_BOOTSTRAP
 183 #  define DO_RTLD_BOOTSTRAP 1
 184 # else
 185 #  define DO_RTLD_BOOTSTRAP 0
 186 # endif
 187 # define ELF_DYNAMIC_RELOCATE(map, scope, lazy, consider_profile, skip_ifunc) \
 188   do {                                                                        \
 189     int edr_lazy = elf_machine_runtime_setup ((map), (scope), (lazy),         \
 190                                               (consider_profile));            \
 191     if (((map) != &GL(dl_rtld_map) || DO_RTLD_BOOTSTRAP))                     \
 192       ELF_DYNAMIC_DO_RELR (map);                                              \
 193     ELF_DYNAMIC_DO_REL ((map), (scope), edr_lazy, skip_ifunc);                \
 194     ELF_DYNAMIC_DO_RELA ((map), (scope), edr_lazy, skip_ifunc);               \
 195   } while (0)
 196
 197 #endif