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 (elf_hash_table_id ((struct elf_link_hash_table *) ((p)->hash)) == (id) \
45 ? ((struct elf_x86_link_hash_table *) ((p)->hash)) : NULL)
47 /* Is a undefined weak symbol which is resolved to 0. Reference to an
48 undefined weak symbol is resolved to 0 when building executable if
50 1. Has non-GOT/non-PLT relocations in text section. Or
51 2. Has no GOT/PLT relocation.
52 Local undefined weak symbol is always resolved to 0.
54 #define UNDEFINED_WEAK_RESOLVED_TO_ZERO(INFO, ID, GOT_RELOC, EH) \
55 ((EH)->elf.root.type == bfd_link_hash_undefweak \
56 && ((EH)->elf.forced_local \
57 || (bfd_link_executable (INFO) \
58 && (elf_x86_hash_table ((INFO), (ID))->interp == NULL \
60 || (EH)->has_non_got_reloc \
61 || !(INFO)->dynamic_undefined_weak))))
63 /* Should copy relocation be generated for a symbol. Don't generate
64 copy relocation against a protected symbol defined in a shared
65 object with GNU_PROPERTY_NO_COPY_ON_PROTECTED. */
66 #define SYMBOL_NO_COPYRELOC(INFO, EH) \
67 ((EH)->def_protected \
68 && ((EH)->elf.root.type == bfd_link_hash_defined \
69 || (EH)->elf.root.type == bfd_link_hash_defweak) \
70 && elf_has_no_copy_on_protected ((EH)->elf.root.u.def.section->owner) \
71 && ((EH)->elf.root.u.def.section->owner->flags & DYNAMIC) != 0 \
72 && ((EH)->elf.root.u.def.section->flags & SEC_CODE) == 0)
74 /* x86 ELF linker hash entry. */
76 struct elf_x86_link_hash_entry
78 struct elf_link_hash_entry elf
;
80 /* Track dynamic relocs copied for this symbol. */
81 struct elf_dyn_relocs
*dyn_relocs
;
83 unsigned char tls_type
;
85 /* TRUE if symbol has GOT or PLT relocations. */
86 unsigned int has_got_reloc
: 1;
88 /* TRUE if symbol has non-GOT/non-PLT relocations in text sections. */
89 unsigned int has_non_got_reloc
: 1;
91 /* Don't call finish_dynamic_symbol on this symbol. */
92 unsigned int no_finish_dynamic_symbol
: 1;
94 /* TRUE if symbol is __tls_get_addr. */
95 unsigned int tls_get_addr
: 1;
97 /* TRUE if symbol is defined as a protected symbol. */
98 unsigned int def_protected
: 1;
100 /* Symbol is referenced by R_386_GOTOFF relocation. This is only used
102 unsigned int gotoff_ref
: 1;
104 /* TRUE if a weak symbol with a real definition needs a copy reloc.
105 When there is a weak symbol with a real definition, the processor
106 independent code will have arranged for us to see the real
107 definition first. We need to copy the needs_copy bit from the
108 real definition and check it when allowing copy reloc in PIE. This
109 is only used by x86-64. */
110 unsigned int needs_copy
: 1;
112 /* Reference count of C/C++ function pointer relocations in read-write
113 section which can be resolved at run-time. */
114 bfd_signed_vma func_pointer_refcount
;
116 /* Information about the GOT PLT entry. Filled when there are both
117 GOT and PLT relocations against the same function. */
118 union gotplt_union plt_got
;
120 /* Information about the second PLT entry. */
121 union gotplt_union plt_second
;
123 /* Offset of the GOTPLT entry reserved for the TLS descriptor,
124 starting at the end of the jump table. */
128 struct elf_x86_lazy_plt_layout
130 /* The first entry in an absolute lazy procedure linkage table looks
132 const bfd_byte
*plt0_entry
;
133 unsigned int plt0_entry_size
; /* Size of PLT0 entry. */
135 /* Later entries in an absolute lazy procedure linkage table look
137 const bfd_byte
*plt_entry
;
138 unsigned int plt_entry_size
; /* Size of each PLT entry. */
140 /* Offsets into plt0_entry that are to be replaced with GOT[1] and
142 unsigned int plt0_got1_offset
;
143 unsigned int plt0_got2_offset
;
145 /* Offset of the end of the PC-relative instruction containing
146 plt0_got2_offset. This is for x86-64 only. */
147 unsigned int plt0_got2_insn_end
;
149 /* Offsets into plt_entry that are to be replaced with... */
150 unsigned int plt_got_offset
; /* ... address of this symbol in .got. */
151 unsigned int plt_reloc_offset
; /* ... offset into relocation table. */
152 unsigned int plt_plt_offset
; /* ... offset to start of .plt. */
154 /* Length of the PC-relative instruction containing plt_got_offset.
155 This is used for x86-64 only. */
156 unsigned int plt_got_insn_size
;
158 /* Offset of the end of the PC-relative jump to plt0_entry. This is
159 used for x86-64 only. */
160 unsigned int plt_plt_insn_end
;
162 /* Offset into plt_entry where the initial value of the GOT entry
164 unsigned int plt_lazy_offset
;
166 /* The first entry in a PIC lazy procedure linkage table looks like
168 const bfd_byte
*pic_plt0_entry
;
170 /* Subsequent entries in a PIC lazy procedure linkage table look
172 const bfd_byte
*pic_plt_entry
;
174 /* .eh_frame covering the lazy .plt section. */
175 const bfd_byte
*eh_frame_plt
;
176 unsigned int eh_frame_plt_size
;
179 struct elf_x86_non_lazy_plt_layout
181 /* Entries in an absolute non-lazy procedure linkage table look like
183 const bfd_byte
*plt_entry
;
184 /* Entries in a PIC non-lazy procedure linkage table look like this. */
185 const bfd_byte
*pic_plt_entry
;
187 unsigned int plt_entry_size
; /* Size of each PLT entry. */
189 /* Offsets into plt_entry that are to be replaced with... */
190 unsigned int plt_got_offset
; /* ... address of this symbol in .got. */
192 /* Length of the PC-relative instruction containing plt_got_offset.
193 This is used for x86-64 only. */
194 unsigned int plt_got_insn_size
;
196 /* .eh_frame covering the non-lazy .plt section. */
197 const bfd_byte
*eh_frame_plt
;
198 unsigned int eh_frame_plt_size
;
201 struct elf_x86_plt_layout
203 /* The first entry in a lazy procedure linkage table looks like this.
204 This is only used for i386 where absolute PLT0 and PIC PLT0 are
206 const bfd_byte
*plt0_entry
;
207 /* Entries in a procedure linkage table look like this. */
208 const bfd_byte
*plt_entry
;
209 unsigned int plt_entry_size
; /* Size of each PLT entry. */
212 unsigned int has_plt0
;
214 /* Offsets into plt_entry that are to be replaced with... */
215 unsigned int plt_got_offset
; /* ... address of this symbol in .got. */
217 /* Length of the PC-relative instruction containing plt_got_offset.
218 This is only used for x86-64. */
219 unsigned int plt_got_insn_size
;
221 /* .eh_frame covering the .plt section. */
222 const bfd_byte
*eh_frame_plt
;
223 unsigned int eh_frame_plt_size
;
226 /* Values in tls_type of x86 ELF linker hash entry. */
227 #define GOT_UNKNOWN 0
231 #define GOT_TLS_IE_POS 5
232 #define GOT_TLS_IE_NEG 6
233 #define GOT_TLS_IE_BOTH 7
234 #define GOT_TLS_GDESC 8
235 #define GOT_TLS_GD_BOTH_P(type) \
236 ((type) == (GOT_TLS_GD | GOT_TLS_GDESC))
237 #define GOT_TLS_GD_P(type) \
238 ((type) == GOT_TLS_GD || GOT_TLS_GD_BOTH_P (type))
239 #define GOT_TLS_GDESC_P(type) \
240 ((type) == GOT_TLS_GDESC || GOT_TLS_GD_BOTH_P (type))
241 #define GOT_TLS_GD_ANY_P(type) \
242 (GOT_TLS_GD_P (type) || GOT_TLS_GDESC_P (type))
244 #define elf_x86_hash_entry(ent) \
245 ((struct elf_x86_link_hash_entry *)(ent))
247 /* x86 ELF linker hash table. */
249 struct elf_x86_link_hash_table
251 struct elf_link_hash_table elf
;
253 /* Short-cuts to get to dynamic linker sections. */
255 asection
*plt_eh_frame
;
256 asection
*plt_second
;
257 asection
*plt_second_eh_frame
;
259 asection
*plt_got_eh_frame
;
261 /* Parameters describing PLT generation, lazy or non-lazy. */
262 struct elf_x86_plt_layout plt
;
264 /* Parameters describing lazy PLT generation. */
265 const struct elf_x86_lazy_plt_layout
*lazy_plt
;
267 /* Parameters describing non-lazy PLT generation. */
268 const struct elf_x86_non_lazy_plt_layout
*non_lazy_plt
;
272 bfd_signed_vma refcount
;
276 /* The amount of space used by the jump slots in the GOT. */
277 bfd_vma sgotplt_jump_table_size
;
279 /* Small local sym cache. */
280 struct sym_cache sym_cache
;
282 /* _TLS_MODULE_BASE_ symbol. */
283 struct bfd_link_hash_entry
*tls_module_base
;
285 /* Used by local STT_GNU_IFUNC symbols. */
286 htab_t loc_hash_table
;
287 void * loc_hash_memory
;
289 /* The offset into splt of the PLT entry for the TLS descriptor
290 resolver. Special values are 0, if not necessary (or not found
291 to be necessary yet), and -1 if needed but not determined
295 /* The offset into sgot of the GOT entry used by the PLT entry
299 /* The index of the next R_X86_64_JUMP_SLOT entry in .rela.plt. */
300 bfd_vma next_jump_slot_index
;
301 /* The index of the next R_X86_64_IRELATIVE entry in .rela.plt. */
302 bfd_vma next_irelative_index
;
304 /* TRUE if there are dynamic relocs against IFUNC symbols that apply
305 to read-only sections. */
306 bfd_boolean readonly_dynrelocs_against_ifunc
;
308 /* TRUE if this is a VxWorks x86 target. */
309 bfd_boolean is_vxworks
;
311 /* The (unloaded but important) .rel.plt.unloaded section on VxWorks.
312 This is used for i386 only. */
315 /* The index of the next unused R_386_TLS_DESC slot in .rel.plt. This
316 is used for i386 only. */
317 bfd_vma next_tls_desc_index
;
319 bfd_vma (*r_info
) (bfd_vma
, bfd_vma
);
320 bfd_vma (*r_sym
) (bfd_vma
);
321 enum elf_target_id target_id
;
322 unsigned int sizeof_reloc
;
323 unsigned int got_entry_size
;
324 unsigned int pointer_r_type
;
325 int dynamic_interpreter_size
;
326 const char *dynamic_interpreter
;
327 const char *tls_get_addr
;
330 struct elf_x86_plt_layout_table
332 /* The lazy PLT layout. */
333 const struct elf_x86_lazy_plt_layout
*lazy_plt
;
335 /* The non-lazy PLT layout. */
336 const struct elf_x86_non_lazy_plt_layout
*non_lazy_plt
;
338 /* The lazy PLT layout for IBT. */
339 const struct elf_x86_lazy_plt_layout
*lazy_ibt_plt
;
341 /* The non-lazy PLT layout for IBT. */
342 const struct elf_x86_non_lazy_plt_layout
*non_lazy_ibt_plt
;
344 /* TRUE if this is a normal x86 target. */
345 bfd_boolean normal_target
;
347 /* TRUE if this is a VxWorks x86 target. */
348 bfd_boolean is_vxworks
;
351 struct elf_x86_obj_tdata
353 struct elf_obj_tdata root
;
355 /* tls_type for each local got entry. */
356 char *local_got_tls_type
;
358 /* GOTPLT entries for TLS descriptors. */
359 bfd_vma
*local_tlsdesc_gotent
;
362 enum elf_x86_plt_type
376 enum elf_x86_plt_type type
;
377 unsigned int plt_got_offset
;
378 unsigned int plt_entry_size
;
379 unsigned int plt_got_insn_size
; /* Only used for x86-64. */
383 #define elf_x86_tdata(abfd) \
384 ((struct elf_x86_obj_tdata *) (abfd)->tdata.any)
386 #define elf_x86_local_got_tls_type(abfd) \
387 (elf_x86_tdata (abfd)->local_got_tls_type)
389 #define elf_x86_local_tlsdesc_gotent(abfd) \
390 (elf_x86_tdata (abfd)->local_tlsdesc_gotent)
392 #define elf_x86_compute_jump_table_size(htab) \
393 ((htab)->elf.srelplt->reloc_count * (htab)->got_entry_size)
395 #define is_x86_elf(bfd, htab) \
396 (bfd_get_flavour (bfd) == bfd_target_elf_flavour \
397 && elf_tdata (bfd) != NULL \
398 && elf_object_id (bfd) == (htab)->target_id)
400 extern bfd_boolean _bfd_x86_elf_mkobject
403 extern void _bfd_x86_elf_set_tls_module_base
404 (struct bfd_link_info
*);
406 extern bfd_vma _bfd_x86_elf_dtpoff_base
407 (struct bfd_link_info
*);
409 extern bfd_boolean _bfd_x86_elf_allocate_dynrelocs
410 (struct elf_link_hash_entry
*, void *);
412 extern bfd_boolean _bfd_x86_elf_allocate_local_dynrelocs
415 extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs
416 (struct elf_link_hash_entry
*, void *);
418 extern struct elf_link_hash_entry
* _bfd_elf_x86_get_local_sym_hash
419 (struct elf_x86_link_hash_table
*, bfd
*, const Elf_Internal_Rela
*,
422 extern hashval_t _bfd_x86_elf_local_htab_hash
425 extern int _bfd_x86_elf_local_htab_eq
426 (const void *, const void *);
428 extern struct bfd_hash_entry
* _bfd_x86_elf_link_hash_newfunc
429 (struct bfd_hash_entry
*, struct bfd_hash_table
*, const char *);
431 extern struct bfd_link_hash_table
* _bfd_x86_elf_link_hash_table_create
434 extern int _bfd_x86_elf_compare_relocs
435 (const void *, const void *);
437 extern bfd_boolean _bfd_x86_elf_link_check_relocs
438 (bfd
*, struct bfd_link_info
*);
440 extern bfd_boolean _bfd_x86_elf_always_size_sections
441 (bfd
*, struct bfd_link_info
*);
443 extern void _bfd_x86_elf_merge_symbol_attribute
444 (struct elf_link_hash_entry
*, const Elf_Internal_Sym
*,
445 bfd_boolean
, bfd_boolean
);
447 extern void _bfd_x86_elf_copy_indirect_symbol
448 (struct bfd_link_info
*, struct elf_link_hash_entry
*,
449 struct elf_link_hash_entry
*);
451 extern bfd_boolean _bfd_x86_elf_fixup_symbol
452 (struct bfd_link_info
*, struct elf_link_hash_entry
*);
454 extern bfd_boolean _bfd_x86_elf_hash_symbol
455 (struct elf_link_hash_entry
*);
457 extern bfd_boolean _bfd_x86_elf_adjust_dynamic_symbol
458 (struct bfd_link_info
*, struct elf_link_hash_entry
*);
460 extern asection
* _bfd_x86_elf_gc_mark_hook
461 (asection
*, struct bfd_link_info
*, Elf_Internal_Rela
*,
462 struct elf_link_hash_entry
*, Elf_Internal_Sym
*);
464 extern long _bfd_x86_elf_get_synthetic_symtab
465 (bfd
*, long, long, bfd_vma
, struct elf_x86_plt
[], asymbol
**,
468 extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties
469 (bfd
*, unsigned int, bfd_byte
*, unsigned int);
471 extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
472 (struct bfd_link_info
*, bfd
*, elf_property
*, elf_property
*);
474 extern bfd
* _bfd_x86_elf_link_setup_gnu_properties
475 (struct bfd_link_info
*, struct elf_x86_plt_layout_table
*);
477 #define bfd_elf64_mkobject \
478 _bfd_x86_elf_mkobject
479 #define bfd_elf32_mkobject \
480 _bfd_x86_elf_mkobject
481 #define bfd_elf64_bfd_link_hash_table_create \
482 _bfd_x86_elf_link_hash_table_create
483 #define bfd_elf32_bfd_link_hash_table_create \
484 _bfd_x86_elf_link_hash_table_create
485 #define bfd_elf64_bfd_link_check_relocs \
486 _bfd_x86_elf_link_check_relocs
487 #define bfd_elf32_bfd_link_check_relocs \
488 _bfd_x86_elf_link_check_relocs
490 #define elf_backend_always_size_sections \
491 _bfd_x86_elf_always_size_sections
492 #define elf_backend_merge_symbol_attribute \
493 _bfd_x86_elf_merge_symbol_attribute
494 #define elf_backend_copy_indirect_symbol \
495 _bfd_x86_elf_copy_indirect_symbol
496 #define elf_backend_fixup_symbol \
497 _bfd_x86_elf_fixup_symbol
498 #define elf_backend_hash_symbol \
499 _bfd_x86_elf_hash_symbol
500 #define elf_backend_adjust_dynamic_symbol \
501 _bfd_x86_elf_adjust_dynamic_symbol
502 #define elf_backend_gc_mark_hook \
503 _bfd_x86_elf_gc_mark_hook
504 #define elf_backend_omit_section_dynsym \
505 ((bfd_boolean (*) (bfd *, struct bfd_link_info *, asection *)) bfd_true)
506 #define elf_backend_parse_gnu_properties \
507 _bfd_x86_elf_parse_gnu_properties
508 #define elf_backend_merge_gnu_properties \
509 _bfd_x86_elf_merge_gnu_properties