| 1 | /* ELF linking support for BFD. |
| 2 | Copyright 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 "elf-bfd.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 | | SEC_LINKER_CREATED); |
| 43 | |
| 44 | s = bfd_make_section (abfd, ".got"); |
| 45 | if (s == NULL |
| 46 | || !bfd_set_section_flags (abfd, s, flags) |
| 47 | || !bfd_set_section_alignment (abfd, s, 2)) |
| 48 | return false; |
| 49 | |
| 50 | if (bed->want_got_plt) |
| 51 | { |
| 52 | s = bfd_make_section (abfd, ".got.plt"); |
| 53 | if (s == NULL |
| 54 | || !bfd_set_section_flags (abfd, s, flags) |
| 55 | || !bfd_set_section_alignment (abfd, s, 2)) |
| 56 | return false; |
| 57 | } |
| 58 | |
| 59 | /* Define the symbol _GLOBAL_OFFSET_TABLE_ at the start of the .got |
| 60 | (or .got.plt) section. We don't do this in the linker script |
| 61 | because we don't want to define the symbol if we are not creating |
| 62 | a global offset table. */ |
| 63 | h = NULL; |
| 64 | if (!(_bfd_generic_link_add_one_symbol |
| 65 | (info, abfd, "_GLOBAL_OFFSET_TABLE_", BSF_GLOBAL, s, (bfd_vma) 0, |
| 66 | (const char *) NULL, false, get_elf_backend_data (abfd)->collect, |
| 67 | (struct bfd_link_hash_entry **) &h))) |
| 68 | return false; |
| 69 | h->elf_link_hash_flags |= ELF_LINK_HASH_DEF_REGULAR; |
| 70 | h->type = STT_OBJECT; |
| 71 | |
| 72 | if (info->shared |
| 73 | && ! _bfd_elf_link_record_dynamic_symbol (info, h)) |
| 74 | return false; |
| 75 | |
| 76 | elf_hash_table (info)->hgot = h; |
| 77 | |
| 78 | /* The first three global offset table entries are reserved. */ |
| 79 | s->_raw_size += 3 * 4; |
| 80 | |
| 81 | return true; |
| 82 | } |
| 83 | \f |
| 84 | |
| 85 | /* Create dynamic sections when linking against a dynamic object. */ |
| 86 | |
| 87 | boolean |
| 88 | _bfd_elf_create_dynamic_sections (abfd, info) |
| 89 | bfd *abfd; |
| 90 | struct bfd_link_info *info; |
| 91 | { |
| 92 | flagword flags; |
| 93 | register asection *s; |
| 94 | struct elf_backend_data *bed = get_elf_backend_data (abfd); |
| 95 | |
| 96 | /* We need to create .plt, .rel[a].plt, .got, .got.plt, .dynbss, and |
| 97 | .rel[a].bss sections. */ |
| 98 | |
| 99 | flags = (SEC_ALLOC | SEC_LOAD | SEC_HAS_CONTENTS | SEC_IN_MEMORY |
| 100 | | SEC_LINKER_CREATED); |
| 101 | |
| 102 | s = bfd_make_section (abfd, ".plt"); |
| 103 | if (s == NULL |
| 104 | || ! bfd_set_section_flags (abfd, s, |
| 105 | (flags | SEC_CODE |
| 106 | | (bed->plt_readonly ? SEC_READONLY : 0))) |
| 107 | || ! bfd_set_section_alignment (abfd, s, 2)) |
| 108 | return false; |
| 109 | |
| 110 | if (bed->want_plt_sym) |
| 111 | { |
| 112 | /* Define the symbol _PROCEDURE_LINKAGE_TABLE_ at the start of the |
| 113 | .plt section. */ |
| 114 | struct elf_link_hash_entry *h = NULL; |
| 115 | if (! (_bfd_generic_link_add_one_symbol |
| 116 | (info, abfd, "_PROCEDURE_LINKAGE_TABLE_", BSF_GLOBAL, s, |
| 117 | (bfd_vma) 0, (const char *) NULL, false, |
| 118 | get_elf_backend_data (abfd)->collect, |
| 119 | (struct bfd_link_hash_entry **) &h))) |
| 120 | return false; |
| 121 | h->elf_link_hash_flags |= ELF_LINK_HASH_DEF_REGULAR; |
| 122 | h->type = STT_OBJECT; |
| 123 | |
| 124 | if (info->shared |
| 125 | && ! _bfd_elf_link_record_dynamic_symbol (info, h)) |
| 126 | return false; |
| 127 | } |
| 128 | |
| 129 | s = bfd_make_section (abfd, bed->use_rela_p ? ".rela.plt" : ".rel.plt"); |
| 130 | if (s == NULL |
| 131 | || ! bfd_set_section_flags (abfd, s, flags | SEC_READONLY) |
| 132 | || ! bfd_set_section_alignment (abfd, s, 2)) |
| 133 | return false; |
| 134 | |
| 135 | if (! _bfd_elf_create_got_section (abfd, info)) |
| 136 | return false; |
| 137 | |
| 138 | /* The .dynbss section is a place to put symbols which are defined |
| 139 | by dynamic objects, are referenced by regular objects, and are |
| 140 | not functions. We must allocate space for them in the process |
| 141 | image and use a R_*_COPY reloc to tell the dynamic linker to |
| 142 | initialize them at run time. The linker script puts the .dynbss |
| 143 | section into the .bss section of the final image. */ |
| 144 | s = bfd_make_section (abfd, ".dynbss"); |
| 145 | if (s == NULL |
| 146 | || ! bfd_set_section_flags (abfd, s, SEC_ALLOC)) |
| 147 | return false; |
| 148 | |
| 149 | /* The .rel[a].bss section holds copy relocs. This section is not |
| 150 | normally needed. We need to create it here, though, so that the |
| 151 | linker will map it to an output section. We can't just create it |
| 152 | only if we need it, because we will not know whether we need it |
| 153 | until we have seen all the input files, and the first time the |
| 154 | main linker code calls BFD after examining all the input files |
| 155 | (size_dynamic_sections) the input sections have already been |
| 156 | mapped to the output sections. If the section turns out not to |
| 157 | be needed, we can discard it later. We will never need this |
| 158 | section when generating a shared object, since they do not use |
| 159 | copy relocs. */ |
| 160 | if (! info->shared) |
| 161 | { |
| 162 | s = bfd_make_section (abfd, bed->use_rela_p ? ".rela.bss" : ".rel.bss"); |
| 163 | if (s == NULL |
| 164 | || ! bfd_set_section_flags (abfd, s, flags | SEC_READONLY) |
| 165 | || ! bfd_set_section_alignment (abfd, s, 2)) |
| 166 | return false; |
| 167 | } |
| 168 | |
| 169 | return true; |
| 170 | } |
| 171 | \f |
| 172 | |
| 173 | /* Record a new dynamic symbol. We record the dynamic symbols as we |
| 174 | read the input files, since we need to have a list of all of them |
| 175 | before we can determine the final sizes of the output sections. |
| 176 | Note that we may actually call this function even though we are not |
| 177 | going to output any dynamic symbols; in some cases we know that a |
| 178 | symbol should be in the dynamic symbol table, but only if there is |
| 179 | one. */ |
| 180 | |
| 181 | boolean |
| 182 | _bfd_elf_link_record_dynamic_symbol (info, h) |
| 183 | struct bfd_link_info *info; |
| 184 | struct elf_link_hash_entry *h; |
| 185 | { |
| 186 | if (h->dynindx == -1) |
| 187 | { |
| 188 | struct bfd_strtab_hash *dynstr; |
| 189 | |
| 190 | h->dynindx = elf_hash_table (info)->dynsymcount; |
| 191 | ++elf_hash_table (info)->dynsymcount; |
| 192 | |
| 193 | dynstr = elf_hash_table (info)->dynstr; |
| 194 | if (dynstr == NULL) |
| 195 | { |
| 196 | /* Create a strtab to hold the dynamic symbol names. */ |
| 197 | elf_hash_table (info)->dynstr = dynstr = _bfd_elf_stringtab_init (); |
| 198 | if (dynstr == NULL) |
| 199 | return false; |
| 200 | } |
| 201 | |
| 202 | h->dynstr_index = ((unsigned long) |
| 203 | _bfd_stringtab_add (dynstr, h->root.root.string, |
| 204 | true, false)); |
| 205 | if (h->dynstr_index == (unsigned long) -1) |
| 206 | return false; |
| 207 | } |
| 208 | |
| 209 | return true; |
| 210 | } |
| 211 | \f |
| 212 | /* Create a special linker section, or return a pointer to a linker section already created */ |
| 213 | |
| 214 | elf_linker_section_t * |
| 215 | _bfd_elf_create_linker_section (abfd, info, which, defaults) |
| 216 | bfd *abfd; |
| 217 | struct bfd_link_info *info; |
| 218 | enum elf_linker_section_enum which; |
| 219 | elf_linker_section_t *defaults; |
| 220 | { |
| 221 | bfd *dynobj = elf_hash_table (info)->dynobj; |
| 222 | elf_linker_section_t *lsect; |
| 223 | |
| 224 | /* Record the first bfd section that needs the special section */ |
| 225 | if (!dynobj) |
| 226 | dynobj = elf_hash_table (info)->dynobj = abfd; |
| 227 | |
| 228 | /* If this is the first time, create the section */ |
| 229 | lsect = elf_linker_section (dynobj, which); |
| 230 | if (!lsect) |
| 231 | { |
| 232 | asection *s; |
| 233 | |
| 234 | lsect = (elf_linker_section_t *) |
| 235 | bfd_alloc (dynobj, sizeof (elf_linker_section_t)); |
| 236 | |
| 237 | *lsect = *defaults; |
| 238 | elf_linker_section (dynobj, which) = lsect; |
| 239 | lsect->which = which; |
| 240 | lsect->hole_written_p = false; |
| 241 | |
| 242 | /* See if the sections already exist */ |
| 243 | lsect->section = s = bfd_get_section_by_name (dynobj, lsect->name); |
| 244 | if (!s || (s->flags & defaults->flags) != defaults->flags) |
| 245 | { |
| 246 | lsect->section = s = bfd_make_section_anyway (dynobj, lsect->name); |
| 247 | |
| 248 | if (s == NULL) |
| 249 | return (elf_linker_section_t *)0; |
| 250 | |
| 251 | bfd_set_section_flags (dynobj, s, defaults->flags); |
| 252 | bfd_set_section_alignment (dynobj, s, lsect->alignment); |
| 253 | } |
| 254 | else if (bfd_get_section_alignment (dynobj, s) < lsect->alignment) |
| 255 | bfd_set_section_alignment (dynobj, s, lsect->alignment); |
| 256 | |
| 257 | s->_raw_size = align_power (s->_raw_size, lsect->alignment); |
| 258 | |
| 259 | /* Is there a hole we have to provide? If so check whether the segment is |
| 260 | too big already */ |
| 261 | if (lsect->hole_size) |
| 262 | { |
| 263 | lsect->hole_offset = s->_raw_size; |
| 264 | s->_raw_size += lsect->hole_size; |
| 265 | if (lsect->hole_offset > lsect->max_hole_offset) |
| 266 | { |
| 267 | (*_bfd_error_handler) ("%s: Section %s is already to large to put hole of %ld bytes in", |
| 268 | bfd_get_filename (abfd), |
| 269 | lsect->name, |
| 270 | (long)lsect->hole_size); |
| 271 | |
| 272 | bfd_set_error (bfd_error_bad_value); |
| 273 | return (elf_linker_section_t *)0; |
| 274 | } |
| 275 | } |
| 276 | |
| 277 | #ifdef DEBUG |
| 278 | fprintf (stderr, "Creating section %s, current size = %ld\n", |
| 279 | lsect->name, (long)s->_raw_size); |
| 280 | #endif |
| 281 | |
| 282 | if (lsect->sym_name) |
| 283 | { |
| 284 | struct elf_link_hash_entry *h = NULL; |
| 285 | #ifdef DEBUG |
| 286 | fprintf (stderr, "Adding %s to section %s\n", |
| 287 | lsect->sym_name, |
| 288 | lsect->name); |
| 289 | #endif |
| 290 | h = (struct elf_link_hash_entry *) |
| 291 | bfd_link_hash_lookup (info->hash, lsect->sym_name, false, false, false); |
| 292 | |
| 293 | if ((h == NULL || h->root.type == bfd_link_hash_undefined) |
| 294 | && !(_bfd_generic_link_add_one_symbol (info, |
| 295 | abfd, |
| 296 | lsect->sym_name, |
| 297 | BSF_GLOBAL, |
| 298 | s, |
| 299 | ((lsect->hole_size) |
| 300 | ? s->_raw_size - lsect->hole_size + lsect->sym_offset |
| 301 | : lsect->sym_offset), |
| 302 | (const char *) NULL, |
| 303 | false, |
| 304 | get_elf_backend_data (abfd)->collect, |
| 305 | (struct bfd_link_hash_entry **) &h))) |
| 306 | return (elf_linker_section_t *)0; |
| 307 | |
| 308 | if ((defaults->which != LINKER_SECTION_SDATA) |
| 309 | && (defaults->which != LINKER_SECTION_SDATA2)) |
| 310 | h->elf_link_hash_flags |= ELF_LINK_HASH_DEF_DYNAMIC; |
| 311 | |
| 312 | h->type = STT_OBJECT; |
| 313 | lsect->sym_hash = h; |
| 314 | |
| 315 | if (info->shared |
| 316 | && ! _bfd_elf_link_record_dynamic_symbol (info, h)) |
| 317 | return (elf_linker_section_t *)0; |
| 318 | } |
| 319 | } |
| 320 | |
| 321 | /* Find the related sections if they have been created */ |
| 322 | if (lsect->bss_name && !lsect->bss_section) |
| 323 | lsect->bss_section = bfd_get_section_by_name (dynobj, lsect->bss_name); |
| 324 | |
| 325 | if (lsect->rel_name && !lsect->rel_section) |
| 326 | lsect->rel_section = bfd_get_section_by_name (dynobj, lsect->rel_name); |
| 327 | |
| 328 | return lsect; |
| 329 | } |
| 330 | |
| 331 | \f |
| 332 | /* Find a linker generated pointer with a given addend and type. */ |
| 333 | |
| 334 | elf_linker_section_pointers_t * |
| 335 | _bfd_elf_find_pointer_linker_section (linker_pointers, addend, which) |
| 336 | elf_linker_section_pointers_t *linker_pointers; |
| 337 | bfd_signed_vma addend; |
| 338 | elf_linker_section_enum_t which; |
| 339 | { |
| 340 | for ( ; linker_pointers != NULL; linker_pointers = linker_pointers->next) |
| 341 | { |
| 342 | if (which == linker_pointers->which && addend == linker_pointers->addend) |
| 343 | return linker_pointers; |
| 344 | } |
| 345 | |
| 346 | return (elf_linker_section_pointers_t *)0; |
| 347 | } |
| 348 | |
| 349 | \f |
| 350 | /* Make the .rela section corresponding to the generated linker section. */ |
| 351 | |
| 352 | boolean |
| 353 | _bfd_elf_make_linker_section_rela (dynobj, lsect, alignment) |
| 354 | bfd *dynobj; |
| 355 | elf_linker_section_t *lsect; |
| 356 | int alignment; |
| 357 | { |
| 358 | if (lsect->rel_section) |
| 359 | return true; |
| 360 | |
| 361 | lsect->rel_section = bfd_get_section_by_name (dynobj, lsect->rel_name); |
| 362 | if (lsect->rel_section == NULL) |
| 363 | { |
| 364 | lsect->rel_section = bfd_make_section (dynobj, lsect->rel_name); |
| 365 | if (lsect->rel_section == NULL |
| 366 | || ! bfd_set_section_flags (dynobj, |
| 367 | lsect->rel_section, |
| 368 | (SEC_ALLOC |
| 369 | | SEC_LOAD |
| 370 | | SEC_HAS_CONTENTS |
| 371 | | SEC_IN_MEMORY |
| 372 | | SEC_LINKER_CREATED |
| 373 | | SEC_READONLY)) |
| 374 | || ! bfd_set_section_alignment (dynobj, lsect->rel_section, alignment)) |
| 375 | return false; |
| 376 | } |
| 377 | |
| 378 | return true; |
| 379 | } |