1 /* x86 specific support for ELF
2 Copyright (C) 2017 Free Software Foundation, Inc.
4 This file is part of BFD, the Binary File Descriptor library.
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.
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.
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. */
26 #include "bfd_stdint.h"
29 #define PLT_CIE_LENGTH 20
30 #define PLT_FDE_LENGTH 36
31 #define PLT_FDE_START_OFFSET 4 + PLT_CIE_LENGTH + 8
32 #define PLT_FDE_LEN_OFFSET 4 + PLT_CIE_LENGTH + 12
34 #define ABI_64_P(abfd) \
35 (get_elf_backend_data (abfd)->s->elfclass == ELFCLASS64)
37 /* If ELIMINATE_COPY_RELOCS is non-zero, the linker will try to avoid
38 copying dynamic variables from a shared lib into an app's dynbss
39 section, and instead use a dynamic relocation to point into the
41 #define ELIMINATE_COPY_RELOCS 1
43 #define elf_x86_hash_table(p, id) \
44 (is_elf_hash_table ((p)->hash) \
45 && elf_hash_table_id ((struct elf_link_hash_table *) ((p)->hash)) == (id) \
46 ? ((struct elf_x86_link_hash_table *) ((p)->hash)) : NULL)
48 /* Will references to this symbol always be local in this object? */
49 #define SYMBOL_REFERENCES_LOCAL_P(INFO, H) \
50 _bfd_x86_elf_link_symbol_references_local ((INFO), (H))
52 /* Is a undefined weak symbol which is resolved to 0. Reference to an
53 undefined weak symbol is resolved to 0 when building executable if
55 1. Has non-GOT/non-PLT relocations in text section. Or
56 2. Has no GOT/PLT relocation.
57 Local undefined weak symbol is always resolved to 0.
59 #define UNDEFINED_WEAK_RESOLVED_TO_ZERO(INFO, EH) \
60 ((EH)->elf.root.type == bfd_link_hash_undefweak \
61 && (SYMBOL_REFERENCES_LOCAL_P ((INFO), &(EH)->elf) \
62 || (bfd_link_executable (INFO) \
63 && (!(EH)->has_got_reloc \
64 || (EH)->has_non_got_reloc))))
66 /* Should copy relocation be generated for a symbol. Don't generate
67 copy relocation against a protected symbol defined in a shared
68 object with GNU_PROPERTY_NO_COPY_ON_PROTECTED. */
69 #define SYMBOL_NO_COPYRELOC(INFO, EH) \
70 ((EH)->def_protected \
71 && ((EH)->elf.root.type == bfd_link_hash_defined \
72 || (EH)->elf.root.type == bfd_link_hash_defweak) \
73 && elf_has_no_copy_on_protected ((EH)->elf.root.u.def.section->owner) \
74 && ((EH)->elf.root.u.def.section->owner->flags & DYNAMIC) != 0 \
75 && ((EH)->elf.root.u.def.section->flags & SEC_CODE) == 0)
77 /* x86 ELF linker hash entry. */
79 struct elf_x86_link_hash_entry
81 struct elf_link_hash_entry elf;
83 /* Track dynamic relocs copied for this symbol. */
84 struct elf_dyn_relocs *dyn_relocs;
86 unsigned char tls_type;
88 /* TRUE if symbol has GOT or PLT relocations. */
89 unsigned int has_got_reloc : 1;
91 /* TRUE if symbol has non-GOT/non-PLT relocations in text sections. */
92 unsigned int has_non_got_reloc : 1;
94 /* Don't call finish_dynamic_symbol on this symbol. */
95 unsigned int no_finish_dynamic_symbol : 1;
97 /* TRUE if symbol is __tls_get_addr. */
98 unsigned int tls_get_addr : 1;
100 /* TRUE if symbol is defined as a protected symbol. */
101 unsigned int def_protected : 1;
103 /* 0: Symbol references are unknown.
104 1: Symbol references aren't local.
105 2: Symbol references are local.
107 unsigned int local_ref : 2;
109 /* TRUE if symbol is defined by linker. */
110 unsigned int linker_def : 1;
112 /* Terue if symbol is referenced by R_386_GOTOFF relocation. This is
113 only used by i386. */
114 unsigned int gotoff_ref : 1;
116 /* TRUE if a weak symbol with a real definition needs a copy reloc.
117 When there is a weak symbol with a real definition, the processor
118 independent code will have arranged for us to see the real
119 definition first. We need to copy the needs_copy bit from the
120 real definition and check it when allowing copy reloc in PIE. This
121 is only used by x86-64. */
122 unsigned int needs_copy : 1;
124 /* Reference count of C/C++ function pointer relocations in read-write
125 section which can be resolved at run-time. */
126 bfd_signed_vma func_pointer_refcount;
128 /* Information about the GOT PLT entry. Filled when there are both
129 GOT and PLT relocations against the same function. */
130 union gotplt_union plt_got;
132 /* Information about the second PLT entry. */
133 union gotplt_union plt_second;
135 /* Offset of the GOTPLT entry reserved for the TLS descriptor,
136 starting at the end of the jump table. */
140 struct elf_x86_lazy_plt_layout
142 /* The first entry in an absolute lazy procedure linkage table looks
144 const bfd_byte *plt0_entry;
145 unsigned int plt0_entry_size; /* Size of PLT0 entry. */
147 /* Later entries in an absolute lazy procedure linkage table look
149 const bfd_byte *plt_entry;
150 unsigned int plt_entry_size; /* Size of each PLT entry. */
152 /* Offsets into plt0_entry that are to be replaced with GOT[1] and
154 unsigned int plt0_got1_offset;
155 unsigned int plt0_got2_offset;
157 /* Offset of the end of the PC-relative instruction containing
158 plt0_got2_offset. This is for x86-64 only. */
159 unsigned int plt0_got2_insn_end;
161 /* Offsets into plt_entry that are to be replaced with... */
162 unsigned int plt_got_offset; /* ... address of this symbol in .got. */
163 unsigned int plt_reloc_offset; /* ... offset into relocation table. */
164 unsigned int plt_plt_offset; /* ... offset to start of .plt. */
166 /* Length of the PC-relative instruction containing plt_got_offset.
167 This is used for x86-64 only. */
168 unsigned int plt_got_insn_size;
170 /* Offset of the end of the PC-relative jump to plt0_entry. This is
171 used for x86-64 only. */
172 unsigned int plt_plt_insn_end;
174 /* Offset into plt_entry where the initial value of the GOT entry
176 unsigned int plt_lazy_offset;
178 /* The first entry in a PIC lazy procedure linkage table looks like
180 const bfd_byte *pic_plt0_entry;
182 /* Subsequent entries in a PIC lazy procedure linkage table look
184 const bfd_byte *pic_plt_entry;
186 /* .eh_frame covering the lazy .plt section. */
187 const bfd_byte *eh_frame_plt;
188 unsigned int eh_frame_plt_size;
191 struct elf_x86_non_lazy_plt_layout
193 /* Entries in an absolute non-lazy procedure linkage table look like
195 const bfd_byte *plt_entry;
196 /* Entries in a PIC non-lazy procedure linkage table look like this. */
197 const bfd_byte *pic_plt_entry;
199 unsigned int plt_entry_size; /* Size of each PLT entry. */
201 /* Offsets into plt_entry that are to be replaced with... */
202 unsigned int plt_got_offset; /* ... address of this symbol in .got. */
204 /* Length of the PC-relative instruction containing plt_got_offset.
205 This is used for x86-64 only. */
206 unsigned int plt_got_insn_size;
208 /* .eh_frame covering the non-lazy .plt section. */
209 const bfd_byte *eh_frame_plt;
210 unsigned int eh_frame_plt_size;
213 struct elf_x86_plt_layout
215 /* The first entry in a lazy procedure linkage table looks like this.
216 This is only used for i386 where absolute PLT0 and PIC PLT0 are
218 const bfd_byte *plt0_entry;
219 /* Entries in a procedure linkage table look like this. */
220 const bfd_byte *plt_entry;
221 unsigned int plt_entry_size; /* Size of each PLT entry. */
224 unsigned int has_plt0;
226 /* Offsets into plt_entry that are to be replaced with... */
227 unsigned int plt_got_offset; /* ... address of this symbol in .got. */
229 /* Length of the PC-relative instruction containing plt_got_offset.
230 This is only used for x86-64. */
231 unsigned int plt_got_insn_size;
233 /* .eh_frame covering the .plt section. */
234 const bfd_byte *eh_frame_plt;
235 unsigned int eh_frame_plt_size;
238 /* Values in tls_type of x86 ELF linker hash entry. */
239 #define GOT_UNKNOWN 0
243 #define GOT_TLS_IE_POS 5
244 #define GOT_TLS_IE_NEG 6
245 #define GOT_TLS_IE_BOTH 7
246 #define GOT_TLS_GDESC 8
247 #define GOT_TLS_GD_BOTH_P(type) \
248 ((type) == (GOT_TLS_GD | GOT_TLS_GDESC))
249 #define GOT_TLS_GD_P(type) \
250 ((type) == GOT_TLS_GD || GOT_TLS_GD_BOTH_P (type))
251 #define GOT_TLS_GDESC_P(type) \
252 ((type) == GOT_TLS_GDESC || GOT_TLS_GD_BOTH_P (type))
253 #define GOT_TLS_GD_ANY_P(type) \
254 (GOT_TLS_GD_P (type) || GOT_TLS_GDESC_P (type))
256 #define elf_x86_hash_entry(ent) \
257 ((struct elf_x86_link_hash_entry *)(ent))
259 /* x86 ELF linker hash table. */
261 struct elf_x86_link_hash_table
263 struct elf_link_hash_table elf;
265 /* Short-cuts to get to dynamic linker sections. */
267 asection *plt_eh_frame;
268 asection *plt_second;
269 asection *plt_second_eh_frame;
271 asection *plt_got_eh_frame;
273 /* Parameters describing PLT generation, lazy or non-lazy. */
274 struct elf_x86_plt_layout plt;
276 /* Parameters describing lazy PLT generation. */
277 const struct elf_x86_lazy_plt_layout *lazy_plt;
279 /* Parameters describing non-lazy PLT generation. */
280 const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
284 bfd_signed_vma refcount;
288 /* The amount of space used by the jump slots in the GOT. */
289 bfd_vma sgotplt_jump_table_size;
291 /* Small local sym cache. */
292 struct sym_cache sym_cache;
294 /* _TLS_MODULE_BASE_ symbol. */
295 struct bfd_link_hash_entry *tls_module_base;
297 /* Used by local STT_GNU_IFUNC symbols. */
298 htab_t loc_hash_table;
299 void * loc_hash_memory;
301 /* The offset into sgot of the GOT entry used by the PLT entry
305 /* The index of the next R_X86_64_JUMP_SLOT entry in .rela.plt. */
306 bfd_vma next_jump_slot_index;
307 /* The index of the next R_X86_64_IRELATIVE entry in .rela.plt. */
308 bfd_vma next_irelative_index;
310 /* TRUE if there are dynamic relocs against IFUNC symbols that apply
311 to read-only sections. */
312 bfd_boolean readonly_dynrelocs_against_ifunc;
314 /* TRUE if this is a VxWorks x86 target. This is only used for
316 bfd_boolean is_vxworks;
318 /* The (unloaded but important) .rel.plt.unloaded section on VxWorks.
319 This is used for i386 only. */
322 /* The index of the next unused R_386_TLS_DESC slot in .rel.plt. This
323 is only used for i386. */
324 bfd_vma next_tls_desc_index;
326 /* The offset into splt of the PLT entry for the TLS descriptor
327 resolver. Special values are 0, if not necessary (or not found
328 to be necessary yet), and -1 if needed but not determined
329 yet. This is only used for x86-64. */
332 bfd_vma (*r_info) (bfd_vma, bfd_vma);
333 bfd_vma (*r_sym) (bfd_vma);
334 bfd_boolean (*is_reloc_section) (const char *);
335 enum elf_target_id target_id;
336 unsigned int sizeof_reloc;
337 unsigned int dt_reloc;
338 unsigned int dt_reloc_sz;
339 unsigned int dt_reloc_ent;
340 unsigned int got_entry_size;
341 unsigned int pointer_r_type;
342 int dynamic_interpreter_size;
343 const char *dynamic_interpreter;
344 const char *tls_get_addr;
347 struct elf_x86_init_table
349 /* The lazy PLT layout. */
350 const struct elf_x86_lazy_plt_layout *lazy_plt;
352 /* The non-lazy PLT layout. */
353 const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
355 /* The lazy PLT layout for IBT. */
356 const struct elf_x86_lazy_plt_layout *lazy_ibt_plt;
358 /* The non-lazy PLT layout for IBT. */
359 const struct elf_x86_non_lazy_plt_layout *non_lazy_ibt_plt;
361 /* TRUE if this is a normal x86 target. */
362 bfd_boolean normal_target;
364 /* TRUE if this is a VxWorks x86 target. */
365 bfd_boolean is_vxworks;
367 bfd_vma (*r_info) (bfd_vma, bfd_vma);
368 bfd_vma (*r_sym) (bfd_vma);
371 struct elf_x86_obj_tdata
373 struct elf_obj_tdata root;
375 /* tls_type for each local got entry. */
376 char *local_got_tls_type;
378 /* GOTPLT entries for TLS descriptors. */
379 bfd_vma *local_tlsdesc_gotent;
382 enum elf_x86_plt_type
396 enum elf_x86_plt_type type;
397 unsigned int plt_got_offset;
398 unsigned int plt_entry_size;
399 unsigned int plt_got_insn_size; /* Only used for x86-64. */
403 #define elf_x86_tdata(abfd) \
404 ((struct elf_x86_obj_tdata *) (abfd)->tdata.any)
406 #define elf_x86_local_got_tls_type(abfd) \
407 (elf_x86_tdata (abfd)->local_got_tls_type)
409 #define elf_x86_local_tlsdesc_gotent(abfd) \
410 (elf_x86_tdata (abfd)->local_tlsdesc_gotent)
412 #define elf_x86_compute_jump_table_size(htab) \
413 ((htab)->elf.srelplt->reloc_count * (htab)->got_entry_size)
415 #define is_x86_elf(bfd, htab) \
416 (bfd_get_flavour (bfd) == bfd_target_elf_flavour \
417 && elf_tdata (bfd) != NULL \
418 && elf_object_id (bfd) == (htab)->target_id)
420 extern bfd_boolean _bfd_x86_elf_mkobject
423 extern void _bfd_x86_elf_set_tls_module_base
424 (struct bfd_link_info *);
426 extern bfd_vma _bfd_x86_elf_dtpoff_base
427 (struct bfd_link_info *);
429 extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs
430 (struct elf_link_hash_entry *, void *);
432 extern struct elf_link_hash_entry * _bfd_elf_x86_get_local_sym_hash
433 (struct elf_x86_link_hash_table *, bfd *, const Elf_Internal_Rela *,
436 extern hashval_t _bfd_x86_elf_local_htab_hash
439 extern int _bfd_x86_elf_local_htab_eq
440 (const void *, const void *);
442 extern struct bfd_hash_entry * _bfd_x86_elf_link_hash_newfunc
443 (struct bfd_hash_entry *, struct bfd_hash_table *, const char *);
445 extern struct bfd_link_hash_table * _bfd_x86_elf_link_hash_table_create
448 extern int _bfd_x86_elf_compare_relocs
449 (const void *, const void *);
451 extern bfd_boolean _bfd_x86_elf_link_check_relocs
452 (bfd *, struct bfd_link_info *);
454 extern bfd_boolean _bfd_x86_elf_size_dynamic_sections
455 (bfd *, struct bfd_link_info *);
457 extern bfd_boolean _bfd_x86_elf_always_size_sections
458 (bfd *, struct bfd_link_info *);
460 extern void _bfd_x86_elf_merge_symbol_attribute
461 (struct elf_link_hash_entry *, const Elf_Internal_Sym *,
462 bfd_boolean, bfd_boolean);
464 extern void _bfd_x86_elf_copy_indirect_symbol
465 (struct bfd_link_info *, struct elf_link_hash_entry *,
466 struct elf_link_hash_entry *);
468 extern bfd_boolean _bfd_x86_elf_fixup_symbol
469 (struct bfd_link_info *, struct elf_link_hash_entry *);
471 extern bfd_boolean _bfd_x86_elf_hash_symbol
472 (struct elf_link_hash_entry *);
474 extern bfd_boolean _bfd_x86_elf_adjust_dynamic_symbol
475 (struct bfd_link_info *, struct elf_link_hash_entry *);
477 extern bfd_boolean _bfd_x86_elf_link_symbol_references_local
478 (struct bfd_link_info *, struct elf_link_hash_entry *);
480 extern asection * _bfd_x86_elf_gc_mark_hook
481 (asection *, struct bfd_link_info *, Elf_Internal_Rela *,
482 struct elf_link_hash_entry *, Elf_Internal_Sym *);
484 extern long _bfd_x86_elf_get_synthetic_symtab
485 (bfd *, long, long, bfd_vma, struct elf_x86_plt [], asymbol **,
488 extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties
489 (bfd *, unsigned int, bfd_byte *, unsigned int);
491 extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
492 (struct bfd_link_info *, bfd *, elf_property *, elf_property *);
494 extern bfd * _bfd_x86_elf_link_setup_gnu_properties
495 (struct bfd_link_info *, struct elf_x86_init_table *);
497 #define bfd_elf64_mkobject \
498 _bfd_x86_elf_mkobject
499 #define bfd_elf32_mkobject \
500 _bfd_x86_elf_mkobject
501 #define bfd_elf64_bfd_link_hash_table_create \
502 _bfd_x86_elf_link_hash_table_create
503 #define bfd_elf32_bfd_link_hash_table_create \
504 _bfd_x86_elf_link_hash_table_create
505 #define bfd_elf64_bfd_link_check_relocs \
506 _bfd_x86_elf_link_check_relocs
507 #define bfd_elf32_bfd_link_check_relocs \
508 _bfd_x86_elf_link_check_relocs
510 #define elf_backend_size_dynamic_sections \
511 _bfd_x86_elf_size_dynamic_sections
512 #define elf_backend_always_size_sections \
513 _bfd_x86_elf_always_size_sections
514 #define elf_backend_merge_symbol_attribute \
515 _bfd_x86_elf_merge_symbol_attribute
516 #define elf_backend_copy_indirect_symbol \
517 _bfd_x86_elf_copy_indirect_symbol
518 #define elf_backend_fixup_symbol \
519 _bfd_x86_elf_fixup_symbol
520 #define elf_backend_hash_symbol \
521 _bfd_x86_elf_hash_symbol
522 #define elf_backend_adjust_dynamic_symbol \
523 _bfd_x86_elf_adjust_dynamic_symbol
524 #define elf_backend_gc_mark_hook \
525 _bfd_x86_elf_gc_mark_hook
526 #define elf_backend_omit_section_dynsym \
527 ((bfd_boolean (*) (bfd *, struct bfd_link_info *, asection *)) bfd_true)
528 #define elf_backend_parse_gnu_properties \
529 _bfd_x86_elf_parse_gnu_properties
530 #define elf_backend_merge_gnu_properties \
531 _bfd_x86_elf_merge_gnu_properties