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 /* TRUE if dynamic relocation is needed. If we are creating a shared
78 library, and this is a reloc against a global symbol, or a non PC
79 relative reloc against a local symbol, then we need to copy the reloc
80 into the shared library. However, if we are linking with -Bsymbolic,
81 we do not need to copy a reloc against a global symbol which is
82 defined in an object we are including in the link (i.e., DEF_REGULAR
83 is set). At this point we have not seen all the input files, so it
84 is possible that DEF_REGULAR is not set now but will be set later (it
85 is never cleared). In case of a weak definition, DEF_REGULAR may be
86 cleared later by a strong definition in a shared library. We account
87 for that possibility below by storing information in the relocs_copied
88 field of the hash table entry. A similar situation occurs when
89 creating shared libraries and symbol visibility changes render the
92 If on the other hand, we are creating an executable, we may need to
93 keep relocations for symbols satisfied by a dynamic library if we
94 manage to avoid copy relocs for the symbol.
96 We also need to generate dynamic pointer relocation against
97 STT_GNU_IFUNC symbol in the non-code section. */
98 #define NEED_DYNAMIC_RELOCATION_P(INFO, H, SEC, R_TYPE, POINTER_TYPE) \
99 ((bfd_link_pic (INFO) \
100 && (! X86_PCREL_TYPE_P (R_TYPE) \
102 && (! (bfd_link_pie (INFO) \
103 || SYMBOLIC_BIND ((INFO), (H))) \
104 || (H)->root.type == bfd_link_hash_defweak \
105 || !(H)->def_regular)))) \
107 && (H)->type == STT_GNU_IFUNC \
108 && (R_TYPE) == POINTER_TYPE \
109 && ((SEC)->flags & SEC_CODE) == 0) \
110 || (ELIMINATE_COPY_RELOCS \
111 && !bfd_link_pic (INFO) \
113 && ((H)->root.type == bfd_link_hash_defweak \
114 || !(H)->def_regular)))
116 /* TRUE if this is actually a static link, or it is a -Bsymbolic link
117 and the symbol is defined locally, or the symbol was forced to be
118 local because of a version file. */
119 #define RESOLVED_LOCALLY_P(INFO, H, HTAB) \
120 (!WILL_CALL_FINISH_DYNAMIC_SYMBOL ((HTAB)->elf.dynamic_sections_created, \
121 bfd_link_pic (INFO), (H)) \
122 || (bfd_link_pic (INFO) \
123 && SYMBOL_REFERENCES_LOCAL_P ((INFO), (H))) \
124 || (ELF_ST_VISIBILITY ((H)->other) \
125 && (H)->root.type == bfd_link_hash_undefweak))
127 /* TRUE if relative relocation should be generated. GOT reference to
128 global symbol in PIC will lead to dynamic symbol. It becomes a
129 problem when "time" or "times" is defined as a variable in an
130 executable, clashing with functions of the same name in libc. If a
131 symbol isn't undefined weak symbol, don't make it dynamic in PIC and
132 generate relative relocation. */
133 #define GENERATE_RELATIVE_RELOC_P(INFO, H) \
134 ((H)->dynindx == -1 \
135 && !(H)->forced_local \
136 && (H)->root.type != bfd_link_hash_undefweak \
137 && bfd_link_pic (INFO))
139 /* TRUE if TLS IE->LE transition is OK. */
140 #define TLS_TRANSITION_IE_TO_LE_P(INFO, H, TLS_TYPE) \
141 (bfd_link_executable (INFO) \
143 && (H)->dynindx == -1 \
144 && (TLS_TYPE & GOT_TLS_IE))
146 /* x86 ELF linker hash entry. */
148 struct elf_x86_link_hash_entry
150 struct elf_link_hash_entry elf
;
152 /* Track dynamic relocs copied for this symbol. */
153 struct elf_dyn_relocs
*dyn_relocs
;
155 unsigned char tls_type
;
157 /* TRUE if symbol has GOT or PLT relocations. */
158 unsigned int has_got_reloc
: 1;
160 /* TRUE if symbol has non-GOT/non-PLT relocations in text sections. */
161 unsigned int has_non_got_reloc
: 1;
163 /* Don't call finish_dynamic_symbol on this symbol. */
164 unsigned int no_finish_dynamic_symbol
: 1;
166 /* TRUE if symbol is __tls_get_addr. */
167 unsigned int tls_get_addr
: 1;
169 /* TRUE if symbol is defined as a protected symbol. */
170 unsigned int def_protected
: 1;
172 /* 0: Symbol references are unknown.
173 1: Symbol references aren't local.
174 2: Symbol references are local.
176 unsigned int local_ref
: 2;
178 /* TRUE if symbol is defined by linker. */
179 unsigned int linker_def
: 1;
181 /* TRUE if symbol is referenced by R_386_GOTOFF relocation. This is
182 only used by i386. */
183 unsigned int gotoff_ref
: 1;
185 /* TRUE if a weak symbol with a real definition needs a copy reloc.
186 When there is a weak symbol with a real definition, the processor
187 independent code will have arranged for us to see the real
188 definition first. We need to copy the needs_copy bit from the
189 real definition and check it when allowing copy reloc in PIE. This
190 is only used by x86-64. */
191 unsigned int needs_copy
: 1;
193 /* Reference count of C/C++ function pointer relocations in read-write
194 section which can be resolved at run-time. */
195 bfd_signed_vma func_pointer_refcount
;
197 /* Information about the GOT PLT entry. Filled when there are both
198 GOT and PLT relocations against the same function. */
199 union gotplt_union plt_got
;
201 /* Information about the second PLT entry. */
202 union gotplt_union plt_second
;
204 /* Offset of the GOTPLT entry reserved for the TLS descriptor,
205 starting at the end of the jump table. */
209 struct elf_x86_lazy_plt_layout
211 /* The first entry in an absolute lazy procedure linkage table looks
213 const bfd_byte
*plt0_entry
;
214 unsigned int plt0_entry_size
; /* Size of PLT0 entry. */
216 /* Later entries in an absolute lazy procedure linkage table look
218 const bfd_byte
*plt_entry
;
219 unsigned int plt_entry_size
; /* Size of each PLT entry. */
221 /* Offsets into plt0_entry that are to be replaced with GOT[1] and
223 unsigned int plt0_got1_offset
;
224 unsigned int plt0_got2_offset
;
226 /* Offset of the end of the PC-relative instruction containing
227 plt0_got2_offset. This is for x86-64 only. */
228 unsigned int plt0_got2_insn_end
;
230 /* Offsets into plt_entry that are to be replaced with... */
231 unsigned int plt_got_offset
; /* ... address of this symbol in .got. */
232 unsigned int plt_reloc_offset
; /* ... offset into relocation table. */
233 unsigned int plt_plt_offset
; /* ... offset to start of .plt. */
235 /* Length of the PC-relative instruction containing plt_got_offset.
236 This is used for x86-64 only. */
237 unsigned int plt_got_insn_size
;
239 /* Offset of the end of the PC-relative jump to plt0_entry. This is
240 used for x86-64 only. */
241 unsigned int plt_plt_insn_end
;
243 /* Offset into plt_entry where the initial value of the GOT entry
245 unsigned int plt_lazy_offset
;
247 /* The first entry in a PIC lazy procedure linkage table looks like
249 const bfd_byte
*pic_plt0_entry
;
251 /* Subsequent entries in a PIC lazy procedure linkage table look
253 const bfd_byte
*pic_plt_entry
;
255 /* .eh_frame covering the lazy .plt section. */
256 const bfd_byte
*eh_frame_plt
;
257 unsigned int eh_frame_plt_size
;
260 struct elf_x86_non_lazy_plt_layout
262 /* Entries in an absolute non-lazy procedure linkage table look like
264 const bfd_byte
*plt_entry
;
265 /* Entries in a PIC non-lazy procedure linkage table look like this. */
266 const bfd_byte
*pic_plt_entry
;
268 unsigned int plt_entry_size
; /* Size of each PLT entry. */
270 /* Offsets into plt_entry that are to be replaced with... */
271 unsigned int plt_got_offset
; /* ... address of this symbol in .got. */
273 /* Length of the PC-relative instruction containing plt_got_offset.
274 This is used for x86-64 only. */
275 unsigned int plt_got_insn_size
;
277 /* .eh_frame covering the non-lazy .plt section. */
278 const bfd_byte
*eh_frame_plt
;
279 unsigned int eh_frame_plt_size
;
282 struct elf_x86_plt_layout
284 /* The first entry in a lazy procedure linkage table looks like this.
285 This is only used for i386 where absolute PLT0 and PIC PLT0 are
287 const bfd_byte
*plt0_entry
;
288 /* Entries in a procedure linkage table look like this. */
289 const bfd_byte
*plt_entry
;
290 unsigned int plt_entry_size
; /* Size of each PLT entry. */
293 unsigned int has_plt0
;
295 /* Offsets into plt_entry that are to be replaced with... */
296 unsigned int plt_got_offset
; /* ... address of this symbol in .got. */
298 /* Length of the PC-relative instruction containing plt_got_offset.
299 This is only used for x86-64. */
300 unsigned int plt_got_insn_size
;
302 /* .eh_frame covering the .plt section. */
303 const bfd_byte
*eh_frame_plt
;
304 unsigned int eh_frame_plt_size
;
307 /* Values in tls_type of x86 ELF linker hash entry. */
308 #define GOT_UNKNOWN 0
312 #define GOT_TLS_IE_POS 5
313 #define GOT_TLS_IE_NEG 6
314 #define GOT_TLS_IE_BOTH 7
315 #define GOT_TLS_GDESC 8
316 #define GOT_TLS_GD_BOTH_P(type) \
317 ((type) == (GOT_TLS_GD | GOT_TLS_GDESC))
318 #define GOT_TLS_GD_P(type) \
319 ((type) == GOT_TLS_GD || GOT_TLS_GD_BOTH_P (type))
320 #define GOT_TLS_GDESC_P(type) \
321 ((type) == GOT_TLS_GDESC || GOT_TLS_GD_BOTH_P (type))
322 #define GOT_TLS_GD_ANY_P(type) \
323 (GOT_TLS_GD_P (type) || GOT_TLS_GDESC_P (type))
325 #define elf_x86_hash_entry(ent) \
326 ((struct elf_x86_link_hash_entry *)(ent))
328 /* x86 ELF linker hash table. */
330 struct elf_x86_link_hash_table
332 struct elf_link_hash_table elf
;
334 /* Short-cuts to get to dynamic linker sections. */
336 asection
*plt_eh_frame
;
337 asection
*plt_second
;
338 asection
*plt_second_eh_frame
;
340 asection
*plt_got_eh_frame
;
342 /* Parameters describing PLT generation, lazy or non-lazy. */
343 struct elf_x86_plt_layout plt
;
345 /* Parameters describing lazy PLT generation. */
346 const struct elf_x86_lazy_plt_layout
*lazy_plt
;
348 /* Parameters describing non-lazy PLT generation. */
349 const struct elf_x86_non_lazy_plt_layout
*non_lazy_plt
;
353 bfd_signed_vma refcount
;
357 /* The amount of space used by the jump slots in the GOT. */
358 bfd_vma sgotplt_jump_table_size
;
360 /* Small local sym cache. */
361 struct sym_cache sym_cache
;
363 /* _TLS_MODULE_BASE_ symbol. */
364 struct bfd_link_hash_entry
*tls_module_base
;
366 /* Used by local STT_GNU_IFUNC symbols. */
367 htab_t loc_hash_table
;
368 void * loc_hash_memory
;
370 /* The offset into sgot of the GOT entry used by the PLT entry
374 /* The index of the next R_X86_64_JUMP_SLOT entry in .rela.plt. */
375 bfd_vma next_jump_slot_index
;
376 /* The index of the next R_X86_64_IRELATIVE entry in .rela.plt. */
377 bfd_vma next_irelative_index
;
379 /* TRUE if there are dynamic relocs against IFUNC symbols that apply
380 to read-only sections. */
381 bfd_boolean readonly_dynrelocs_against_ifunc
;
383 /* TRUE if this is a VxWorks x86 target. This is only used for
385 bfd_boolean is_vxworks
;
387 /* The (unloaded but important) .rel.plt.unloaded section on VxWorks.
388 This is used for i386 only. */
391 /* The index of the next unused R_386_TLS_DESC slot in .rel.plt. This
392 is only used for i386. */
393 bfd_vma next_tls_desc_index
;
395 /* The offset into splt of the PLT entry for the TLS descriptor
396 resolver. Special values are 0, if not necessary (or not found
397 to be necessary yet), and -1 if needed but not determined
398 yet. This is only used for x86-64. */
401 bfd_vma (*r_info
) (bfd_vma
, bfd_vma
);
402 bfd_vma (*r_sym
) (bfd_vma
);
403 bfd_boolean (*is_reloc_section
) (const char *);
404 enum elf_target_id target_id
;
405 unsigned int sizeof_reloc
;
406 unsigned int dt_reloc
;
407 unsigned int dt_reloc_sz
;
408 unsigned int dt_reloc_ent
;
409 unsigned int got_entry_size
;
410 unsigned int pointer_r_type
;
411 int dynamic_interpreter_size
;
412 const char *dynamic_interpreter
;
413 const char *tls_get_addr
;
416 struct elf_x86_init_table
418 /* The lazy PLT layout. */
419 const struct elf_x86_lazy_plt_layout
*lazy_plt
;
421 /* The non-lazy PLT layout. */
422 const struct elf_x86_non_lazy_plt_layout
*non_lazy_plt
;
424 /* The lazy PLT layout for IBT. */
425 const struct elf_x86_lazy_plt_layout
*lazy_ibt_plt
;
427 /* The non-lazy PLT layout for IBT. */
428 const struct elf_x86_non_lazy_plt_layout
*non_lazy_ibt_plt
;
430 /* TRUE if this is a normal x86 target. */
431 bfd_boolean normal_target
;
433 /* TRUE if this is a VxWorks x86 target. */
434 bfd_boolean is_vxworks
;
436 bfd_vma (*r_info
) (bfd_vma
, bfd_vma
);
437 bfd_vma (*r_sym
) (bfd_vma
);
440 struct elf_x86_obj_tdata
442 struct elf_obj_tdata root
;
444 /* tls_type for each local got entry. */
445 char *local_got_tls_type
;
447 /* GOTPLT entries for TLS descriptors. */
448 bfd_vma
*local_tlsdesc_gotent
;
451 enum elf_x86_plt_type
465 enum elf_x86_plt_type type
;
466 unsigned int plt_got_offset
;
467 unsigned int plt_entry_size
;
468 unsigned int plt_got_insn_size
; /* Only used for x86-64. */
472 #define elf_x86_tdata(abfd) \
473 ((struct elf_x86_obj_tdata *) (abfd)->tdata.any)
475 #define elf_x86_local_got_tls_type(abfd) \
476 (elf_x86_tdata (abfd)->local_got_tls_type)
478 #define elf_x86_local_tlsdesc_gotent(abfd) \
479 (elf_x86_tdata (abfd)->local_tlsdesc_gotent)
481 #define elf_x86_compute_jump_table_size(htab) \
482 ((htab)->elf.srelplt->reloc_count * (htab)->got_entry_size)
484 #define is_x86_elf(bfd, htab) \
485 (bfd_get_flavour (bfd) == bfd_target_elf_flavour \
486 && elf_tdata (bfd) != NULL \
487 && elf_object_id (bfd) == (htab)->target_id)
489 extern bfd_boolean _bfd_x86_elf_mkobject
492 extern void _bfd_x86_elf_set_tls_module_base
493 (struct bfd_link_info
*);
495 extern bfd_vma _bfd_x86_elf_dtpoff_base
496 (struct bfd_link_info
*);
498 extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs
499 (struct elf_link_hash_entry
*, void *);
501 extern struct elf_link_hash_entry
* _bfd_elf_x86_get_local_sym_hash
502 (struct elf_x86_link_hash_table
*, bfd
*, const Elf_Internal_Rela
*,
505 extern hashval_t _bfd_x86_elf_local_htab_hash
508 extern int _bfd_x86_elf_local_htab_eq
509 (const void *, const void *);
511 extern struct bfd_hash_entry
* _bfd_x86_elf_link_hash_newfunc
512 (struct bfd_hash_entry
*, struct bfd_hash_table
*, const char *);
514 extern struct bfd_link_hash_table
* _bfd_x86_elf_link_hash_table_create
517 extern int _bfd_x86_elf_compare_relocs
518 (const void *, const void *);
520 extern bfd_boolean _bfd_x86_elf_link_check_relocs
521 (bfd
*, struct bfd_link_info
*);
523 extern bfd_boolean _bfd_x86_elf_size_dynamic_sections
524 (bfd
*, struct bfd_link_info
*);
526 extern bfd_boolean _bfd_x86_elf_always_size_sections
527 (bfd
*, struct bfd_link_info
*);
529 extern void _bfd_x86_elf_merge_symbol_attribute
530 (struct elf_link_hash_entry
*, const Elf_Internal_Sym
*,
531 bfd_boolean
, bfd_boolean
);
533 extern void _bfd_x86_elf_copy_indirect_symbol
534 (struct bfd_link_info
*, struct elf_link_hash_entry
*,
535 struct elf_link_hash_entry
*);
537 extern bfd_boolean _bfd_x86_elf_fixup_symbol
538 (struct bfd_link_info
*, struct elf_link_hash_entry
*);
540 extern bfd_boolean _bfd_x86_elf_hash_symbol
541 (struct elf_link_hash_entry
*);
543 extern bfd_boolean _bfd_x86_elf_adjust_dynamic_symbol
544 (struct bfd_link_info
*, struct elf_link_hash_entry
*);
546 extern bfd_boolean _bfd_x86_elf_link_symbol_references_local
547 (struct bfd_link_info
*, struct elf_link_hash_entry
*);
549 extern asection
* _bfd_x86_elf_gc_mark_hook
550 (asection
*, struct bfd_link_info
*, Elf_Internal_Rela
*,
551 struct elf_link_hash_entry
*, Elf_Internal_Sym
*);
553 extern long _bfd_x86_elf_get_synthetic_symtab
554 (bfd
*, long, long, bfd_vma
, struct elf_x86_plt
[], asymbol
**,
557 extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties
558 (bfd
*, unsigned int, bfd_byte
*, unsigned int);
560 extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
561 (struct bfd_link_info
*, bfd
*, elf_property
*, elf_property
*);
563 extern bfd
* _bfd_x86_elf_link_setup_gnu_properties
564 (struct bfd_link_info
*, struct elf_x86_init_table
*);
566 #define bfd_elf64_mkobject \
567 _bfd_x86_elf_mkobject
568 #define bfd_elf32_mkobject \
569 _bfd_x86_elf_mkobject
570 #define bfd_elf64_bfd_link_hash_table_create \
571 _bfd_x86_elf_link_hash_table_create
572 #define bfd_elf32_bfd_link_hash_table_create \
573 _bfd_x86_elf_link_hash_table_create
574 #define bfd_elf64_bfd_link_check_relocs \
575 _bfd_x86_elf_link_check_relocs
576 #define bfd_elf32_bfd_link_check_relocs \
577 _bfd_x86_elf_link_check_relocs
579 #define elf_backend_size_dynamic_sections \
580 _bfd_x86_elf_size_dynamic_sections
581 #define elf_backend_always_size_sections \
582 _bfd_x86_elf_always_size_sections
583 #define elf_backend_merge_symbol_attribute \
584 _bfd_x86_elf_merge_symbol_attribute
585 #define elf_backend_copy_indirect_symbol \
586 _bfd_x86_elf_copy_indirect_symbol
587 #define elf_backend_fixup_symbol \
588 _bfd_x86_elf_fixup_symbol
589 #define elf_backend_hash_symbol \
590 _bfd_x86_elf_hash_symbol
591 #define elf_backend_adjust_dynamic_symbol \
592 _bfd_x86_elf_adjust_dynamic_symbol
593 #define elf_backend_gc_mark_hook \
594 _bfd_x86_elf_gc_mark_hook
595 #define elf_backend_omit_section_dynsym \
596 ((bfd_boolean (*) (bfd *, struct bfd_link_info *, asection *)) bfd_true)
597 #define elf_backend_parse_gnu_properties \
598 _bfd_x86_elf_parse_gnu_properties
599 #define elf_backend_merge_gnu_properties \
600 _bfd_x86_elf_merge_gnu_properties