elf/get-dynamic-info.h

   1 /* Read the dynamic section at DYN and fill in INFO with indices DT_*.
   2    Copyright (C) 2012-2023 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 /* Populate dynamic tags in l_info.  */
  20
  21 #ifndef _GET_DYNAMIC_INFO_H
  22 #define _GET_DYNAMIC_INFO_H
  23
  24 #include <assert.h>
  25 #include <dl-machine-rel.h>
  26 #include <libc-diag.h>
  27
  28 static inline void __attribute__ ((unused, always_inline))
  29 elf_get_dynamic_info (struct link_map *l, bool bootstrap,
  30                       bool static_pie_bootstrap)
  31 {
  32 #if __ELF_NATIVE_CLASS == 32
  33   typedef Elf32_Word d_tag_utype;
  34 #elif __ELF_NATIVE_CLASS == 64
  35   typedef Elf64_Xword d_tag_utype;
  36 #endif
  37
  38 #ifndef STATIC_PIE_BOOTSTRAP
  39   if (!bootstrap && l->l_ld == NULL)
  40     return;
  41 #endif
  42
  43   ElfW(Dyn) **info = l->l_info;
  44
  45   for (ElfW(Dyn) *dyn = l->l_ld; dyn->d_tag != DT_NULL; dyn++)
  46     {
  47       d_tag_utype i;
  48
  49       if ((d_tag_utype) dyn->d_tag < DT_NUM)
  50         i = dyn->d_tag;
  51       else if (dyn->d_tag >= DT_LOPROC
  52                && dyn->d_tag < DT_LOPROC + DT_THISPROCNUM)
  53         i = dyn->d_tag - DT_LOPROC + DT_NUM;
  54       else if ((d_tag_utype) DT_VERSIONTAGIDX (dyn->d_tag) < DT_VERSIONTAGNUM)
  55         i = VERSYMIDX (dyn->d_tag);
  56       else if ((d_tag_utype) DT_EXTRATAGIDX (dyn->d_tag) < DT_EXTRANUM)
  57         i = DT_EXTRATAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
  58             + DT_VERSIONTAGNUM;
  59       else if ((d_tag_utype) DT_VALTAGIDX (dyn->d_tag) < DT_VALNUM)
  60         i = DT_VALTAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
  61             + DT_VERSIONTAGNUM + DT_EXTRANUM;
  62       else if ((d_tag_utype) DT_ADDRTAGIDX (dyn->d_tag) < DT_ADDRNUM)
  63         i = DT_ADDRTAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
  64             + DT_VERSIONTAGNUM + DT_EXTRANUM + DT_VALNUM;
  65       else
  66         continue;
  67
  68       info[i] = dyn;
  69     }
  70
  71   /* Don't adjust .dynamic unnecessarily.  */
  72   if (l->l_addr != 0 && dl_relocate_ld (l))
  73     {
  74       ElfW(Addr) l_addr = l->l_addr;
  75
  76 # define ADJUST_DYN_INFO(tag) \
  77       do                                                                      \
  78         {                                                                     \
  79           if (info[tag] != NULL)                                              \
  80           info[tag]->d_un.d_ptr += l_addr;                                    \
  81         }                                                                     \
  82       while (0)
  83
  84       ADJUST_DYN_INFO (DT_HASH);
  85       ADJUST_DYN_INFO (DT_PLTGOT);
  86       ADJUST_DYN_INFO (DT_STRTAB);
  87       ADJUST_DYN_INFO (DT_SYMTAB);
  88       ADJUST_DYN_INFO (DT_RELR);
  89       ADJUST_DYN_INFO (DT_JMPREL);
  90       ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
  91       ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
  92 # undef ADJUST_DYN_INFO
  93
  94       /* DT_RELA/DT_REL are mandatory.  But they may have zero value if
  95          there is DT_RELR.  Don't relocate them if they are zero.  */
  96 # define ADJUST_DYN_INFO(tag) \
  97       do                                                                      \
  98         if (info[tag] != NULL && info[tag]->d_un.d_ptr != 0)                  \
  99          info[tag]->d_un.d_ptr += l_addr;                                     \
 100       while (0)
 101
 102 # if ! ELF_MACHINE_NO_RELA
 103       ADJUST_DYN_INFO (DT_RELA);
 104 # endif
 105 # if ! ELF_MACHINE_NO_REL
 106       ADJUST_DYN_INFO (DT_REL);
 107 # endif
 108 # undef ADJUST_DYN_INFO
 109     }
 110   if (info[DT_PLTREL] != NULL)
 111     {
 112 #if ELF_MACHINE_NO_RELA
 113       assert (info[DT_PLTREL]->d_un.d_val == DT_REL);
 114 #elif ELF_MACHINE_NO_REL
 115       assert (info[DT_PLTREL]->d_un.d_val == DT_RELA);
 116 #else
 117       assert (info[DT_PLTREL]->d_un.d_val == DT_REL
 118               || info[DT_PLTREL]->d_un.d_val == DT_RELA);
 119 #endif
 120     }
 121 #if ! ELF_MACHINE_NO_RELA
 122   if (info[DT_RELA] != NULL)
 123     assert (info[DT_RELAENT]->d_un.d_val == sizeof (ElfW(Rela)));
 124 # endif
 125 # if ! ELF_MACHINE_NO_REL
 126   if (info[DT_REL] != NULL)
 127     assert (info[DT_RELENT]->d_un.d_val == sizeof (ElfW(Rel)));
 128 #endif
 129   if (info[DT_RELR] != NULL)
 130     assert (info[DT_RELRENT]->d_un.d_val == sizeof (ElfW(Relr)));
 131   if (bootstrap || static_pie_bootstrap)
 132     {
 133       assert (info[DT_RUNPATH] == NULL);
 134       assert (info[DT_RPATH] == NULL);
 135     }
 136   if (bootstrap)
 137     {
 138       /* Only the bind now flags are allowed.  */
 139       assert (info[VERSYMIDX (DT_FLAGS_1)] == NULL
 140               || (info[VERSYMIDX (DT_FLAGS_1)]->d_un.d_val & ~DF_1_NOW) == 0);
 141       /* Flags must not be set for ld.so.  */
 142       assert (info[DT_FLAGS] == NULL
 143               || (info[DT_FLAGS]->d_un.d_val & ~DF_BIND_NOW) == 0);
 144     }
 145   else
 146     {
 147       if (info[DT_FLAGS] != NULL)
 148         {
 149           /* Flags are used.  Translate to the old form where available.
 150              Since these l_info entries are only tested for NULL pointers it
 151              is ok if they point to the DT_FLAGS entry.  */
 152           l->l_flags = info[DT_FLAGS]->d_un.d_val;
 153
 154           if (l->l_flags & DF_SYMBOLIC)
 155             info[DT_SYMBOLIC] = info[DT_FLAGS];
 156           if (l->l_flags & DF_TEXTREL)
 157             info[DT_TEXTREL] = info[DT_FLAGS];
 158           if (l->l_flags & DF_BIND_NOW)
 159             info[DT_BIND_NOW] = info[DT_FLAGS];
 160         }
 161
 162       if (info[VERSYMIDX (DT_FLAGS_1)] != NULL)
 163         {
 164           l->l_flags_1 = info[VERSYMIDX (DT_FLAGS_1)]->d_un.d_val;
 165           if (l->l_flags_1 & DF_1_NODELETE)
 166             l->l_nodelete_pending = true;
 167
 168           /* Only DT_1_SUPPORTED_MASK bits are supported, and we would like
 169              to assert this, but we can't. Users have been setting
 170              unsupported DF_1_* flags for a long time and glibc has ignored
 171              them. Therefore to avoid breaking existing applications the
 172              best we can do is add a warning during debugging with the
 173              intent of notifying the user of the problem.  */
 174           if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_FILES, 0)
 175               && l->l_flags_1 & ~DT_1_SUPPORTED_MASK)
 176             _dl_debug_printf ("\nWARNING: Unsupported flag value(s) of 0x%x "
 177                               "in DT_FLAGS_1.\n",
 178                              l->l_flags_1 & ~DT_1_SUPPORTED_MASK);
 179
 180          if (l->l_flags_1 & DF_1_NOW)
 181            info[DT_BIND_NOW] = info[VERSYMIDX (DT_FLAGS_1)];
 182        }
 183
 184     if (info[DT_RUNPATH] != NULL)
 185       /* If both RUNPATH and RPATH are given, the latter is ignored.  */
 186       info[DT_RPATH] = NULL;
 187    }
 188 }
 189
 190 #endif