| 1 | /* ELF linking support for BFD. |
| 2 | Copyright 1993, 1995 Free Software Foundation, Inc. |
| 3 | |
| 4 | This file is part of BFD, the Binary File Descriptor library. |
| 5 | |
| 6 | This program is free software; you can redistribute it and/or modify |
| 7 | it under the terms of the GNU General Public License as published by |
| 8 | the Free Software Foundation; either version 2 of the License, or |
| 9 | (at your option) any later version. |
| 10 | |
| 11 | This program is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | GNU General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU General Public License |
| 17 | along with this program; if not, write to the Free Software |
| 18 | Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ |
| 19 | |
| 20 | #include "bfd.h" |
| 21 | #include "sysdep.h" |
| 22 | #include "bfdlink.h" |
| 23 | #include "libbfd.h" |
| 24 | #define ARCH_SIZE 0 |
| 25 | #include "libelf.h" |
| 26 | |
| 27 | boolean |
| 28 | _bfd_elf_create_got_section (abfd, info) |
| 29 | bfd *abfd; |
| 30 | struct bfd_link_info *info; |
| 31 | { |
| 32 | flagword flags; |
| 33 | register asection *s; |
| 34 | struct elf_link_hash_entry *h; |
| 35 | struct elf_backend_data *bed = get_elf_backend_data (abfd); |
| 36 | |
| 37 | /* This function may be called more than once. */ |
| 38 | if (bfd_get_section_by_name (abfd, ".got") != NULL) |
| 39 | return true; |
| 40 | |
| 41 | flags = SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY; |
| 42 | |
| 43 | s = bfd_make_section (abfd, ".got"); |
| 44 | if (s == NULL |
| 45 | || !bfd_set_section_flags (abfd, s, flags) |
| 46 | || !bfd_set_section_alignment (abfd, s, 2)) |
| 47 | return false; |
| 48 | |
| 49 | if (bed->want_got_plt) |
| 50 | { |
| 51 | s = bfd_make_section (abfd, ".got.plt"); |
| 52 | if (s == NULL |
| 53 | || !bfd_set_section_flags (abfd, s, flags) |
| 54 | || !bfd_set_section_alignment (abfd, s, 2)) |
| 55 | return false; |
| 56 | } |
| 57 | |
| 58 | /* Define the symbol _GLOBAL_OFFSET_TABLE_ at the start of the .got |
| 59 | (or .got.plt) section. We don't do this in the linker script |
| 60 | because we don't want to define the symbol if we are not creating |
| 61 | a global offset table. */ |
| 62 | h = NULL; |
| 63 | if (!(_bfd_generic_link_add_one_symbol |
| 64 | (info, abfd, "_GLOBAL_OFFSET_TABLE_", BSF_GLOBAL, s, (bfd_vma) 0, |
| 65 | (const char *) NULL, false, get_elf_backend_data (abfd)->collect, |
| 66 | (struct bfd_link_hash_entry **) &h))) |
| 67 | return false; |
| 68 | h->elf_link_hash_flags |= ELF_LINK_HASH_DEF_REGULAR; |
| 69 | h->type = STT_OBJECT; |
| 70 | |
| 71 | if (info->shared |
| 72 | && ! _bfd_elf_link_record_dynamic_symbol (info, h)) |
| 73 | return false; |
| 74 | |
| 75 | /* The first three global offset table entries are reserved. */ |
| 76 | s->_raw_size += 3 * 4; |
| 77 | |
| 78 | return true; |
| 79 | } |
| 80 | |
| 81 | /* Create dynamic sections when linking against a dynamic object. */ |
| 82 | |
| 83 | boolean |
| 84 | _bfd_elf_create_dynamic_sections (abfd, info) |
| 85 | bfd *abfd; |
| 86 | struct bfd_link_info *info; |
| 87 | { |
| 88 | flagword flags; |
| 89 | register asection *s; |
| 90 | struct elf_backend_data *bed = get_elf_backend_data (abfd); |
| 91 | |
| 92 | /* We need to create .plt, .rel[a].plt, .got, .got.plt, .dynbss, and |
| 93 | .rel[a].bss sections. */ |
| 94 | |
| 95 | flags = SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY; |
| 96 | |
| 97 | s = bfd_make_section (abfd, ".plt"); |
| 98 | if (s == NULL |
| 99 | || ! bfd_set_section_flags (abfd, s, |
| 100 | (flags | SEC_CODE |
| 101 | | (bed->plt_readonly ? SEC_READONLY : 0))) |
| 102 | || ! bfd_set_section_alignment (abfd, s, 2)) |
| 103 | return false; |
| 104 | |
| 105 | if (bed->want_plt_sym) |
| 106 | { |
| 107 | /* Define the symbol _PROCEDURE_LINKAGE_TABLE_ at the start of the |
| 108 | .plt section. */ |
| 109 | struct elf_link_hash_entry *h = NULL; |
| 110 | if (! (_bfd_generic_link_add_one_symbol |
| 111 | (info, abfd, "_PROCEDURE_LINKAGE_TABLE_", BSF_GLOBAL, s, |
| 112 | (bfd_vma) 0, (const char *) NULL, false, |
| 113 | get_elf_backend_data (abfd)->collect, |
| 114 | (struct bfd_link_hash_entry **) &h))) |
| 115 | return false; |
| 116 | h->elf_link_hash_flags |= ELF_LINK_HASH_DEF_REGULAR; |
| 117 | h->type = STT_OBJECT; |
| 118 | |
| 119 | if (info->shared |
| 120 | && ! _bfd_elf_link_record_dynamic_symbol (info, h)) |
| 121 | return false; |
| 122 | } |
| 123 | |
| 124 | s = bfd_make_section (abfd, bed->use_rela_p ? ".rela.plt" : ".rel.plt"); |
| 125 | if (s == NULL |
| 126 | || ! bfd_set_section_flags (abfd, s, flags | SEC_READONLY) |
| 127 | || ! bfd_set_section_alignment (abfd, s, 2)) |
| 128 | return false; |
| 129 | |
| 130 | if (! _bfd_elf_create_got_section (abfd, info)) |
| 131 | return false; |
| 132 | |
| 133 | /* The .dynbss section is a place to put symbols which are defined |
| 134 | by dynamic objects, are referenced by regular objects, and are |
| 135 | not functions. We must allocate space for them in the process |
| 136 | image and use a R_*_COPY reloc to tell the dynamic linker to |
| 137 | initialize them at run time. The linker script puts the .dynbss |
| 138 | section into the .bss section of the final image. */ |
| 139 | s = bfd_make_section (abfd, ".dynbss"); |
| 140 | if (s == NULL |
| 141 | || ! bfd_set_section_flags (abfd, s, SEC_ALLOC)) |
| 142 | return false; |
| 143 | |
| 144 | /* The .rel[a].bss section holds copy relocs. This section is not |
| 145 | normally needed. We need to create it here, though, so that the |
| 146 | linker will map it to an output section. We can't just create it |
| 147 | only if we need it, because we will not know whether we need it |
| 148 | until we have seen all the input files, and the first time the |
| 149 | main linker code calls BFD after examining all the input files |
| 150 | (size_dynamic_sections) the input sections have already been |
| 151 | mapped to the output sections. If the section turns out not to |
| 152 | be needed, we can discard it later. We will never need this |
| 153 | section when generating a shared object, since they do not use |
| 154 | copy relocs. */ |
| 155 | if (! info->shared) |
| 156 | { |
| 157 | s = bfd_make_section (abfd, bed->use_rela_p ? ".rela.bss" : ".rel.bss"); |
| 158 | if (s == NULL |
| 159 | || ! bfd_set_section_flags (abfd, s, flags | SEC_READONLY) |
| 160 | || ! bfd_set_section_alignment (abfd, s, 2)) |
| 161 | return false; |
| 162 | } |
| 163 | |
| 164 | return true; |
| 165 | } |
| 166 | |
| 167 | /* Record a new dynamic symbol. We record the dynamic symbols as we |
| 168 | read the input files, since we need to have a list of all of them |
| 169 | before we can determine the final sizes of the output sections. |
| 170 | Note that we may actually call this function even though we are not |
| 171 | going to output any dynamic symbols; in some cases we know that a |
| 172 | symbol should be in the dynamic symbol table, but only if there is |
| 173 | one. */ |
| 174 | |
| 175 | boolean |
| 176 | _bfd_elf_link_record_dynamic_symbol (info, h) |
| 177 | struct bfd_link_info *info; |
| 178 | struct elf_link_hash_entry *h; |
| 179 | { |
| 180 | if (h->dynindx == -1) |
| 181 | { |
| 182 | struct bfd_strtab_hash *dynstr; |
| 183 | |
| 184 | h->dynindx = elf_hash_table (info)->dynsymcount; |
| 185 | ++elf_hash_table (info)->dynsymcount; |
| 186 | |
| 187 | dynstr = elf_hash_table (info)->dynstr; |
| 188 | if (dynstr == NULL) |
| 189 | { |
| 190 | /* Create a strtab to hold the dynamic symbol names. */ |
| 191 | elf_hash_table (info)->dynstr = dynstr = _bfd_elf_stringtab_init (); |
| 192 | if (dynstr == NULL) |
| 193 | return false; |
| 194 | } |
| 195 | |
| 196 | h->dynstr_index = ((unsigned long) |
| 197 | _bfd_stringtab_add (dynstr, h->root.root.string, |
| 198 | true, false)); |
| 199 | if (h->dynstr_index == (unsigned long) -1) |
| 200 | return false; |
| 201 | } |
| 202 | |
| 203 | return true; |
| 204 | } |