| 1 | /* x86 specific support for ELF |
| 2 | Copyright (C) 2017 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 3 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., 51 Franklin Street - Fifth Floor, Boston, |
| 19 | MA 02110-1301, USA. */ |
| 20 | |
| 21 | #include "sysdep.h" |
| 22 | #include "bfd.h" |
| 23 | #include "bfdlink.h" |
| 24 | #include "libbfd.h" |
| 25 | #include "elf-bfd.h" |
| 26 | #include "bfd_stdint.h" |
| 27 | #include "hashtab.h" |
| 28 | |
| 29 | #define ABI_64_P(abfd) \ |
| 30 | (get_elf_backend_data (abfd)->s->elfclass == ELFCLASS64) |
| 31 | |
| 32 | /* If ELIMINATE_COPY_RELOCS is non-zero, the linker will try to avoid |
| 33 | copying dynamic variables from a shared lib into an app's dynbss |
| 34 | section, and instead use a dynamic relocation to point into the |
| 35 | shared lib. */ |
| 36 | #define ELIMINATE_COPY_RELOCS 1 |
| 37 | |
| 38 | #define elf_x86_hash_table(p, id) \ |
| 39 | (elf_hash_table_id ((struct elf_link_hash_table *) ((p)->hash)) == (id) \ |
| 40 | ? ((struct elf_x86_link_hash_table *) ((p)->hash)) : NULL) |
| 41 | |
| 42 | /* Is a undefined weak symbol which is resolved to 0. Reference to an |
| 43 | undefined weak symbol is resolved to 0 when building executable if |
| 44 | it isn't dynamic and |
| 45 | 1. Has non-GOT/non-PLT relocations in text section. Or |
| 46 | 2. Has no GOT/PLT relocation. |
| 47 | Local undefined weak symbol is always resolved to 0. |
| 48 | */ |
| 49 | #define UNDEFINED_WEAK_RESOLVED_TO_ZERO(INFO, ID, GOT_RELOC, EH) \ |
| 50 | ((EH)->elf.root.type == bfd_link_hash_undefweak \ |
| 51 | && ((EH)->elf.forced_local \ |
| 52 | || (bfd_link_executable (INFO) \ |
| 53 | && (elf_x86_hash_table ((INFO), (ID))->interp == NULL \ |
| 54 | || !(GOT_RELOC) \ |
| 55 | || (EH)->has_non_got_reloc \ |
| 56 | || !(INFO)->dynamic_undefined_weak)))) |
| 57 | |
| 58 | /* Should copy relocation be generated for a symbol. Don't generate |
| 59 | copy relocation against a protected symbol defined in a shared |
| 60 | object with GNU_PROPERTY_NO_COPY_ON_PROTECTED. */ |
| 61 | #define SYMBOL_NO_COPYRELOC(INFO, EH) \ |
| 62 | ((EH)->def_protected \ |
| 63 | && ((EH)->elf.root.type == bfd_link_hash_defined \ |
| 64 | || (EH)->elf.root.type == bfd_link_hash_defweak) \ |
| 65 | && elf_has_no_copy_on_protected ((EH)->elf.root.u.def.section->owner) \ |
| 66 | && ((EH)->elf.root.u.def.section->owner->flags & DYNAMIC) != 0 \ |
| 67 | && ((EH)->elf.root.u.def.section->flags & SEC_CODE) == 0) |
| 68 | |
| 69 | /* x86 ELF linker hash entry. */ |
| 70 | |
| 71 | struct elf_x86_link_hash_entry |
| 72 | { |
| 73 | struct elf_link_hash_entry elf; |
| 74 | |
| 75 | /* Track dynamic relocs copied for this symbol. */ |
| 76 | struct elf_dyn_relocs *dyn_relocs; |
| 77 | |
| 78 | unsigned char tls_type; |
| 79 | |
| 80 | /* TRUE if symbol has GOT or PLT relocations. */ |
| 81 | unsigned int has_got_reloc : 1; |
| 82 | |
| 83 | /* TRUE if symbol has non-GOT/non-PLT relocations in text sections. */ |
| 84 | unsigned int has_non_got_reloc : 1; |
| 85 | |
| 86 | /* Don't call finish_dynamic_symbol on this symbol. */ |
| 87 | unsigned int no_finish_dynamic_symbol : 1; |
| 88 | |
| 89 | /* TRUE if symbol is __tls_get_addr. */ |
| 90 | unsigned int tls_get_addr : 1; |
| 91 | |
| 92 | /* TRUE if symbol is defined as a protected symbol. */ |
| 93 | unsigned int def_protected : 1; |
| 94 | |
| 95 | /* Symbol is referenced by R_386_GOTOFF relocation. This is only used |
| 96 | by i386. */ |
| 97 | unsigned int gotoff_ref : 1; |
| 98 | |
| 99 | /* TRUE if a weak symbol with a real definition needs a copy reloc. |
| 100 | When there is a weak symbol with a real definition, the processor |
| 101 | independent code will have arranged for us to see the real |
| 102 | definition first. We need to copy the needs_copy bit from the |
| 103 | real definition and check it when allowing copy reloc in PIE. This |
| 104 | is only used by x86-64. */ |
| 105 | unsigned int needs_copy : 1; |
| 106 | |
| 107 | /* Reference count of C/C++ function pointer relocations in read-write |
| 108 | section which can be resolved at run-time. */ |
| 109 | bfd_signed_vma func_pointer_refcount; |
| 110 | |
| 111 | /* Information about the GOT PLT entry. Filled when there are both |
| 112 | GOT and PLT relocations against the same function. */ |
| 113 | union gotplt_union plt_got; |
| 114 | |
| 115 | /* Information about the second PLT entry. */ |
| 116 | union gotplt_union plt_second; |
| 117 | |
| 118 | /* Offset of the GOTPLT entry reserved for the TLS descriptor, |
| 119 | starting at the end of the jump table. */ |
| 120 | bfd_vma tlsdesc_got; |
| 121 | }; |
| 122 | |
| 123 | struct elf_x86_lazy_plt_layout |
| 124 | { |
| 125 | /* The first entry in an absolute lazy procedure linkage table looks |
| 126 | like this. */ |
| 127 | const bfd_byte *plt0_entry; |
| 128 | unsigned int plt0_entry_size; /* Size of PLT0 entry. */ |
| 129 | |
| 130 | /* Later entries in an absolute lazy procedure linkage table look |
| 131 | like this. */ |
| 132 | const bfd_byte *plt_entry; |
| 133 | unsigned int plt_entry_size; /* Size of each PLT entry. */ |
| 134 | |
| 135 | /* Offsets into plt0_entry that are to be replaced with GOT[1] and |
| 136 | GOT[2]. */ |
| 137 | unsigned int plt0_got1_offset; |
| 138 | unsigned int plt0_got2_offset; |
| 139 | |
| 140 | /* Offset of the end of the PC-relative instruction containing |
| 141 | plt0_got2_offset. This is for x86-64 only. */ |
| 142 | unsigned int plt0_got2_insn_end; |
| 143 | |
| 144 | /* Offsets into plt_entry that are to be replaced with... */ |
| 145 | unsigned int plt_got_offset; /* ... address of this symbol in .got. */ |
| 146 | unsigned int plt_reloc_offset; /* ... offset into relocation table. */ |
| 147 | unsigned int plt_plt_offset; /* ... offset to start of .plt. */ |
| 148 | |
| 149 | /* Length of the PC-relative instruction containing plt_got_offset. |
| 150 | This is used for x86-64 only. */ |
| 151 | unsigned int plt_got_insn_size; |
| 152 | |
| 153 | /* Offset of the end of the PC-relative jump to plt0_entry. This is |
| 154 | used for x86-64 only. */ |
| 155 | unsigned int plt_plt_insn_end; |
| 156 | |
| 157 | /* Offset into plt_entry where the initial value of the GOT entry |
| 158 | points. */ |
| 159 | unsigned int plt_lazy_offset; |
| 160 | |
| 161 | /* The first entry in a PIC lazy procedure linkage table looks like |
| 162 | this. This is used for i386 only. */ |
| 163 | const bfd_byte *pic_plt0_entry; |
| 164 | |
| 165 | /* Subsequent entries in a PIC lazy procedure linkage table look |
| 166 | like this. This is used for i386 only. */ |
| 167 | const bfd_byte *pic_plt_entry; |
| 168 | |
| 169 | /* .eh_frame covering the lazy .plt section. */ |
| 170 | const bfd_byte *eh_frame_plt; |
| 171 | unsigned int eh_frame_plt_size; |
| 172 | }; |
| 173 | |
| 174 | struct elf_x86_non_lazy_plt_layout |
| 175 | { |
| 176 | /* Entries in an absolute non-lazy procedure linkage table look like |
| 177 | this. */ |
| 178 | const bfd_byte *plt_entry; |
| 179 | /* Entries in a PIC non-lazy procedure linkage table look like this. |
| 180 | This is used for i386 only. */ |
| 181 | const bfd_byte *pic_plt_entry; |
| 182 | |
| 183 | unsigned int plt_entry_size; /* Size of each PLT entry. */ |
| 184 | |
| 185 | /* Offsets into plt_entry that are to be replaced with... */ |
| 186 | unsigned int plt_got_offset; /* ... address of this symbol in .got. */ |
| 187 | |
| 188 | /* Length of the PC-relative instruction containing plt_got_offset. |
| 189 | This is used for x86-64 only. */ |
| 190 | unsigned int plt_got_insn_size; |
| 191 | |
| 192 | /* .eh_frame covering the non-lazy .plt section. */ |
| 193 | const bfd_byte *eh_frame_plt; |
| 194 | unsigned int eh_frame_plt_size; |
| 195 | }; |
| 196 | |
| 197 | struct elf_x86_plt_layout |
| 198 | { |
| 199 | /* The first entry in a lazy procedure linkage table looks like this. |
| 200 | This is only used for i386 where absolute PLT0 and PIC PLT0 are |
| 201 | different. */ |
| 202 | const bfd_byte *plt0_entry; |
| 203 | /* Entries in a procedure linkage table look like this. */ |
| 204 | const bfd_byte *plt_entry; |
| 205 | unsigned int plt_entry_size; /* Size of each PLT entry. */ |
| 206 | |
| 207 | /* 1 has PLT0. */ |
| 208 | unsigned int has_plt0; |
| 209 | |
| 210 | /* Offsets into plt_entry that are to be replaced with... */ |
| 211 | unsigned int plt_got_offset; /* ... address of this symbol in .got. */ |
| 212 | |
| 213 | /* Length of the PC-relative instruction containing plt_got_offset. |
| 214 | This is only used for x86-64. */ |
| 215 | unsigned int plt_got_insn_size; |
| 216 | |
| 217 | /* .eh_frame covering the .plt section. */ |
| 218 | const bfd_byte *eh_frame_plt; |
| 219 | unsigned int eh_frame_plt_size; |
| 220 | }; |
| 221 | |
| 222 | /* The first 3 values in tls_type of x86 ELF linker hash entry. */ |
| 223 | #define GOT_UNKNOWN 0 |
| 224 | #define GOT_NORMAL 1 |
| 225 | #define GOT_TLS_GD 2 |
| 226 | |
| 227 | #define elf_x86_hash_entry(ent) \ |
| 228 | ((struct elf_x86_link_hash_entry *)(ent)) |
| 229 | |
| 230 | /* x86 ELF linker hash table. */ |
| 231 | |
| 232 | struct elf_x86_link_hash_table |
| 233 | { |
| 234 | struct elf_link_hash_table elf; |
| 235 | |
| 236 | /* Short-cuts to get to dynamic linker sections. */ |
| 237 | asection *interp; |
| 238 | asection *plt_eh_frame; |
| 239 | asection *plt_second; |
| 240 | asection *plt_second_eh_frame; |
| 241 | asection *plt_got; |
| 242 | asection *plt_got_eh_frame; |
| 243 | |
| 244 | /* Parameters describing PLT generation, lazy or non-lazy. */ |
| 245 | struct elf_x86_plt_layout plt; |
| 246 | |
| 247 | /* Parameters describing lazy PLT generation. */ |
| 248 | const struct elf_x86_lazy_plt_layout *lazy_plt; |
| 249 | |
| 250 | /* Parameters describing non-lazy PLT generation. */ |
| 251 | const struct elf_x86_non_lazy_plt_layout *non_lazy_plt; |
| 252 | |
| 253 | union |
| 254 | { |
| 255 | bfd_signed_vma refcount; |
| 256 | bfd_vma offset; |
| 257 | } tls_ld_or_ldm_got; |
| 258 | |
| 259 | /* The amount of space used by the jump slots in the GOT. */ |
| 260 | bfd_vma sgotplt_jump_table_size; |
| 261 | |
| 262 | /* Small local sym cache. */ |
| 263 | struct sym_cache sym_cache; |
| 264 | |
| 265 | /* _TLS_MODULE_BASE_ symbol. */ |
| 266 | struct bfd_link_hash_entry *tls_module_base; |
| 267 | |
| 268 | /* Used by local STT_GNU_IFUNC symbols. */ |
| 269 | htab_t loc_hash_table; |
| 270 | void * loc_hash_memory; |
| 271 | |
| 272 | /* The offset into splt of the PLT entry for the TLS descriptor |
| 273 | resolver. Special values are 0, if not necessary (or not found |
| 274 | to be necessary yet), and -1 if needed but not determined |
| 275 | yet. */ |
| 276 | bfd_vma tlsdesc_plt; |
| 277 | |
| 278 | /* The offset into sgot of the GOT entry used by the PLT entry |
| 279 | above. */ |
| 280 | bfd_vma tlsdesc_got; |
| 281 | |
| 282 | /* The index of the next R_X86_64_JUMP_SLOT entry in .rela.plt. */ |
| 283 | bfd_vma next_jump_slot_index; |
| 284 | /* The index of the next R_X86_64_IRELATIVE entry in .rela.plt. */ |
| 285 | bfd_vma next_irelative_index; |
| 286 | |
| 287 | /* TRUE if there are dynamic relocs against IFUNC symbols that apply |
| 288 | to read-only sections. */ |
| 289 | bfd_boolean readonly_dynrelocs_against_ifunc; |
| 290 | |
| 291 | /* The (unloaded but important) .rel.plt.unloaded section on VxWorks. |
| 292 | This is used for i386 only. */ |
| 293 | asection *srelplt2; |
| 294 | |
| 295 | /* The index of the next unused R_386_TLS_DESC slot in .rel.plt. This |
| 296 | is used for i386 only. */ |
| 297 | bfd_vma next_tls_desc_index; |
| 298 | |
| 299 | bfd_vma (*r_info) (bfd_vma, bfd_vma); |
| 300 | bfd_vma (*r_sym) (bfd_vma); |
| 301 | unsigned int pointer_r_type; |
| 302 | int dynamic_interpreter_size; |
| 303 | const char *dynamic_interpreter; |
| 304 | const char *tls_get_addr; |
| 305 | }; |
| 306 | |
| 307 | struct elf_x86_obj_tdata |
| 308 | { |
| 309 | struct elf_obj_tdata root; |
| 310 | |
| 311 | /* tls_type for each local got entry. */ |
| 312 | char *local_got_tls_type; |
| 313 | |
| 314 | /* GOTPLT entries for TLS descriptors. */ |
| 315 | bfd_vma *local_tlsdesc_gotent; |
| 316 | }; |
| 317 | |
| 318 | enum elf_x86_plt_type |
| 319 | { |
| 320 | plt_non_lazy = 0, |
| 321 | plt_lazy = 1 << 0, |
| 322 | plt_pic = 1 << 1, |
| 323 | plt_second = 1 << 2, |
| 324 | plt_unknown = -1 |
| 325 | }; |
| 326 | |
| 327 | struct elf_x86_plt |
| 328 | { |
| 329 | const char *name; |
| 330 | asection *sec; |
| 331 | bfd_byte *contents; |
| 332 | enum elf_x86_plt_type type; |
| 333 | unsigned int plt_got_offset; |
| 334 | unsigned int plt_entry_size; |
| 335 | unsigned int plt_got_insn_size; /* Only used for x86-64. */ |
| 336 | long count; |
| 337 | }; |
| 338 | |
| 339 | #define elf_x86_tdata(abfd) \ |
| 340 | ((struct elf_x86_obj_tdata *) (abfd)->tdata.any) |
| 341 | |
| 342 | #define elf_x86_local_got_tls_type(abfd) \ |
| 343 | (elf_x86_tdata (abfd)->local_got_tls_type) |
| 344 | |
| 345 | #define elf_x86_local_tlsdesc_gotent(abfd) \ |
| 346 | (elf_x86_tdata (abfd)->local_tlsdesc_gotent) |
| 347 | |
| 348 | extern void _bfd_x86_elf_set_tls_module_base |
| 349 | (struct bfd_link_info *); |
| 350 | |
| 351 | extern bfd_vma _bfd_x86_elf_dtpoff_base |
| 352 | (struct bfd_link_info *); |
| 353 | |
| 354 | extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs |
| 355 | (struct elf_link_hash_entry *, void *); |
| 356 | |
| 357 | extern struct elf_link_hash_entry * _bfd_elf_x86_get_local_sym_hash |
| 358 | (struct elf_x86_link_hash_table *, bfd *, const Elf_Internal_Rela *, |
| 359 | bfd_boolean); |
| 360 | |
| 361 | extern hashval_t _bfd_x86_elf_local_htab_hash |
| 362 | (const void *); |
| 363 | |
| 364 | extern int _bfd_x86_elf_local_htab_eq |
| 365 | (const void *, const void *); |
| 366 | |
| 367 | extern struct bfd_hash_entry * _bfd_x86_elf_link_hash_newfunc |
| 368 | (struct bfd_hash_entry *, struct bfd_hash_table *, const char *); |
| 369 | |
| 370 | extern struct bfd_link_hash_table * _bfd_x86_elf_link_hash_table_create |
| 371 | (bfd *); |
| 372 | |
| 373 | extern int _bfd_x86_elf_compare_relocs |
| 374 | (const void *, const void *); |
| 375 | |
| 376 | extern bfd_boolean _bfd_x86_elf_link_check_relocs |
| 377 | (bfd *, struct bfd_link_info *); |
| 378 | |
| 379 | extern bfd_boolean _bfd_x86_elf_always_size_sections |
| 380 | (bfd *, struct bfd_link_info *); |
| 381 | |
| 382 | extern void _bfd_x86_elf_merge_symbol_attribute |
| 383 | (struct elf_link_hash_entry *, const Elf_Internal_Sym *, |
| 384 | bfd_boolean, bfd_boolean); |
| 385 | |
| 386 | extern void _bfd_x86_elf_copy_indirect_symbol |
| 387 | (struct bfd_link_info *, struct elf_link_hash_entry *, |
| 388 | struct elf_link_hash_entry *); |
| 389 | |
| 390 | extern bfd_boolean _bfd_x86_elf_fixup_symbol |
| 391 | (struct bfd_link_info *, struct elf_link_hash_entry *); |
| 392 | |
| 393 | extern bfd_boolean _bfd_x86_elf_hash_symbol |
| 394 | (struct elf_link_hash_entry *); |
| 395 | |
| 396 | extern long _bfd_x86_elf_get_synthetic_symtab |
| 397 | (bfd *, long, long, bfd_vma, struct elf_x86_plt [], asymbol **, |
| 398 | asymbol **); |
| 399 | |
| 400 | extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties |
| 401 | (bfd *, unsigned int, bfd_byte *, unsigned int); |
| 402 | |
| 403 | extern bfd_boolean _bfd_x86_elf_merge_gnu_properties |
| 404 | (struct bfd_link_info *, bfd *, elf_property *, elf_property *); |
| 405 | |
| 406 | #define bfd_elf64_bfd_link_hash_table_create \ |
| 407 | _bfd_x86_elf_link_hash_table_create |
| 408 | #define bfd_elf32_bfd_link_hash_table_create \ |
| 409 | _bfd_x86_elf_link_hash_table_create |
| 410 | #define bfd_elf64_bfd_link_check_relocs \ |
| 411 | _bfd_x86_elf_link_check_relocs |
| 412 | #define bfd_elf32_bfd_link_check_relocs \ |
| 413 | _bfd_x86_elf_link_check_relocs |
| 414 | |
| 415 | #define elf_backend_always_size_sections \ |
| 416 | _bfd_x86_elf_always_size_sections |
| 417 | #define elf_backend_merge_symbol_attribute \ |
| 418 | _bfd_x86_elf_merge_symbol_attribute |
| 419 | #define elf_backend_copy_indirect_symbol \ |
| 420 | _bfd_x86_elf_copy_indirect_symbol |
| 421 | #define elf_backend_fixup_symbol \ |
| 422 | _bfd_x86_elf_fixup_symbol |
| 423 | #define elf_backend_hash_symbol \ |
| 424 | _bfd_x86_elf_hash_symbol |
| 425 | #define elf_backend_omit_section_dynsym \ |
| 426 | ((bfd_boolean (*) (bfd *, struct bfd_link_info *, asection *)) bfd_true) |
| 427 | #define elf_backend_parse_gnu_properties \ |
| 428 | _bfd_x86_elf_parse_gnu_properties |
| 429 | #define elf_backend_merge_gnu_properties \ |
| 430 | _bfd_x86_elf_merge_gnu_properties |