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, ID, GOT_RELOC, EH) \
60 ((EH)->elf.root.type == bfd_link_hash_undefweak \
61 && (SYMBOL_REFERENCES_LOCAL_P ((INFO), &(EH)->elf) \
62 || (bfd_link_executable (INFO) \
63 && (elf_x86_hash_table ((INFO), (ID))->interp == NULL \
65 || (EH)->has_non_got_reloc \
66 || !(INFO)->dynamic_undefined_weak))))
68 /* Should copy relocation be generated for a symbol. Don't generate
69 copy relocation against a protected symbol defined in a shared
70 object with GNU_PROPERTY_NO_COPY_ON_PROTECTED. */
71 #define SYMBOL_NO_COPYRELOC(INFO, EH) \
72 ((EH)->def_protected \
73 && ((EH)->elf.root.type == bfd_link_hash_defined \
74 || (EH)->elf.root.type == bfd_link_hash_defweak) \
75 && elf_has_no_copy_on_protected ((EH)->elf.root.u.def.section->owner) \
76 && ((EH)->elf.root.u.def.section->owner->flags & DYNAMIC) != 0 \
77 && ((EH)->elf.root.u.def.section->flags & SEC_CODE) == 0)
79 /* x86 ELF linker hash entry. */
81 struct elf_x86_link_hash_entry
83 struct elf_link_hash_entry elf
;
85 /* Track dynamic relocs copied for this symbol. */
86 struct elf_dyn_relocs
*dyn_relocs
;
88 unsigned char tls_type
;
90 /* TRUE if symbol has GOT or PLT relocations. */
91 unsigned int has_got_reloc
: 1;
93 /* TRUE if symbol has non-GOT/non-PLT relocations in text sections. */
94 unsigned int has_non_got_reloc
: 1;
96 /* Don't call finish_dynamic_symbol on this symbol. */
97 unsigned int no_finish_dynamic_symbol
: 1;
99 /* TRUE if symbol is __tls_get_addr. */
100 unsigned int tls_get_addr
: 1;
102 /* TRUE if symbol is defined as a protected symbol. */
103 unsigned int def_protected
: 1;
105 /* 0: Symbol references are unknown.
106 1: Symbol references aren't local.
107 2: Symbol references are local.
109 unsigned int local_ref
: 2;
111 /* TRUE if symbol is defined by linker. */
112 unsigned int linker_def
: 1;
114 /* Terue if symbol is referenced by R_386_GOTOFF relocation. This is
115 only used by i386. */
116 unsigned int gotoff_ref
: 1;
118 /* TRUE if a weak symbol with a real definition needs a copy reloc.
119 When there is a weak symbol with a real definition, the processor
120 independent code will have arranged for us to see the real
121 definition first. We need to copy the needs_copy bit from the
122 real definition and check it when allowing copy reloc in PIE. This
123 is only used by x86-64. */
124 unsigned int needs_copy
: 1;
126 /* Reference count of C/C++ function pointer relocations in read-write
127 section which can be resolved at run-time. */
128 bfd_signed_vma func_pointer_refcount
;
130 /* Information about the GOT PLT entry. Filled when there are both
131 GOT and PLT relocations against the same function. */
132 union gotplt_union plt_got
;
134 /* Information about the second PLT entry. */
135 union gotplt_union plt_second
;
137 /* Offset of the GOTPLT entry reserved for the TLS descriptor,
138 starting at the end of the jump table. */
142 struct elf_x86_lazy_plt_layout
144 /* The first entry in an absolute lazy procedure linkage table looks
146 const bfd_byte
*plt0_entry
;
147 unsigned int plt0_entry_size
; /* Size of PLT0 entry. */
149 /* Later entries in an absolute lazy procedure linkage table look
151 const bfd_byte
*plt_entry
;
152 unsigned int plt_entry_size
; /* Size of each PLT entry. */
154 /* Offsets into plt0_entry that are to be replaced with GOT[1] and
156 unsigned int plt0_got1_offset
;
157 unsigned int plt0_got2_offset
;
159 /* Offset of the end of the PC-relative instruction containing
160 plt0_got2_offset. This is for x86-64 only. */
161 unsigned int plt0_got2_insn_end
;
163 /* Offsets into plt_entry that are to be replaced with... */
164 unsigned int plt_got_offset
; /* ... address of this symbol in .got. */
165 unsigned int plt_reloc_offset
; /* ... offset into relocation table. */
166 unsigned int plt_plt_offset
; /* ... offset to start of .plt. */
168 /* Length of the PC-relative instruction containing plt_got_offset.
169 This is used for x86-64 only. */
170 unsigned int plt_got_insn_size
;
172 /* Offset of the end of the PC-relative jump to plt0_entry. This is
173 used for x86-64 only. */
174 unsigned int plt_plt_insn_end
;
176 /* Offset into plt_entry where the initial value of the GOT entry
178 unsigned int plt_lazy_offset
;
180 /* The first entry in a PIC lazy procedure linkage table looks like
182 const bfd_byte
*pic_plt0_entry
;
184 /* Subsequent entries in a PIC lazy procedure linkage table look
186 const bfd_byte
*pic_plt_entry
;
188 /* .eh_frame covering the lazy .plt section. */
189 const bfd_byte
*eh_frame_plt
;
190 unsigned int eh_frame_plt_size
;
193 struct elf_x86_non_lazy_plt_layout
195 /* Entries in an absolute non-lazy procedure linkage table look like
197 const bfd_byte
*plt_entry
;
198 /* Entries in a PIC non-lazy procedure linkage table look like this. */
199 const bfd_byte
*pic_plt_entry
;
201 unsigned int plt_entry_size
; /* Size of each PLT entry. */
203 /* Offsets into plt_entry that are to be replaced with... */
204 unsigned int plt_got_offset
; /* ... address of this symbol in .got. */
206 /* Length of the PC-relative instruction containing plt_got_offset.
207 This is used for x86-64 only. */
208 unsigned int plt_got_insn_size
;
210 /* .eh_frame covering the non-lazy .plt section. */
211 const bfd_byte
*eh_frame_plt
;
212 unsigned int eh_frame_plt_size
;
215 struct elf_x86_plt_layout
217 /* The first entry in a lazy procedure linkage table looks like this.
218 This is only used for i386 where absolute PLT0 and PIC PLT0 are
220 const bfd_byte
*plt0_entry
;
221 /* Entries in a procedure linkage table look like this. */
222 const bfd_byte
*plt_entry
;
223 unsigned int plt_entry_size
; /* Size of each PLT entry. */
226 unsigned int has_plt0
;
228 /* Offsets into plt_entry that are to be replaced with... */
229 unsigned int plt_got_offset
; /* ... address of this symbol in .got. */
231 /* Length of the PC-relative instruction containing plt_got_offset.
232 This is only used for x86-64. */
233 unsigned int plt_got_insn_size
;
235 /* .eh_frame covering the .plt section. */
236 const bfd_byte
*eh_frame_plt
;
237 unsigned int eh_frame_plt_size
;
240 /* Values in tls_type of x86 ELF linker hash entry. */
241 #define GOT_UNKNOWN 0
245 #define GOT_TLS_IE_POS 5
246 #define GOT_TLS_IE_NEG 6
247 #define GOT_TLS_IE_BOTH 7
248 #define GOT_TLS_GDESC 8
249 #define GOT_TLS_GD_BOTH_P(type) \
250 ((type) == (GOT_TLS_GD | GOT_TLS_GDESC))
251 #define GOT_TLS_GD_P(type) \
252 ((type) == GOT_TLS_GD || GOT_TLS_GD_BOTH_P (type))
253 #define GOT_TLS_GDESC_P(type) \
254 ((type) == GOT_TLS_GDESC || GOT_TLS_GD_BOTH_P (type))
255 #define GOT_TLS_GD_ANY_P(type) \
256 (GOT_TLS_GD_P (type) || GOT_TLS_GDESC_P (type))
258 #define elf_x86_hash_entry(ent) \
259 ((struct elf_x86_link_hash_entry *)(ent))
261 /* x86 ELF linker hash table. */
263 struct elf_x86_link_hash_table
265 struct elf_link_hash_table elf
;
267 /* Short-cuts to get to dynamic linker sections. */
269 asection
*plt_eh_frame
;
270 asection
*plt_second
;
271 asection
*plt_second_eh_frame
;
273 asection
*plt_got_eh_frame
;
275 /* Parameters describing PLT generation, lazy or non-lazy. */
276 struct elf_x86_plt_layout plt
;
278 /* Parameters describing lazy PLT generation. */
279 const struct elf_x86_lazy_plt_layout
*lazy_plt
;
281 /* Parameters describing non-lazy PLT generation. */
282 const struct elf_x86_non_lazy_plt_layout
*non_lazy_plt
;
286 bfd_signed_vma refcount
;
290 /* The amount of space used by the jump slots in the GOT. */
291 bfd_vma sgotplt_jump_table_size
;
293 /* Small local sym cache. */
294 struct sym_cache sym_cache
;
296 /* _TLS_MODULE_BASE_ symbol. */
297 struct bfd_link_hash_entry
*tls_module_base
;
299 /* Used by local STT_GNU_IFUNC symbols. */
300 htab_t loc_hash_table
;
301 void * loc_hash_memory
;
303 /* The offset into sgot of the GOT entry used by the PLT entry
307 /* The index of the next R_X86_64_JUMP_SLOT entry in .rela.plt. */
308 bfd_vma next_jump_slot_index
;
309 /* The index of the next R_X86_64_IRELATIVE entry in .rela.plt. */
310 bfd_vma next_irelative_index
;
312 /* TRUE if there are dynamic relocs against IFUNC symbols that apply
313 to read-only sections. */
314 bfd_boolean readonly_dynrelocs_against_ifunc
;
316 /* TRUE if this is a VxWorks x86 target. This is only used for
318 bfd_boolean is_vxworks
;
320 /* The (unloaded but important) .rel.plt.unloaded section on VxWorks.
321 This is used for i386 only. */
324 /* The index of the next unused R_386_TLS_DESC slot in .rel.plt. This
325 is only used for i386. */
326 bfd_vma next_tls_desc_index
;
328 /* The offset into splt of the PLT entry for the TLS descriptor
329 resolver. Special values are 0, if not necessary (or not found
330 to be necessary yet), and -1 if needed but not determined
331 yet. This is only used for x86-64. */
334 bfd_vma (*r_info
) (bfd_vma
, bfd_vma
);
335 bfd_vma (*r_sym
) (bfd_vma
);
336 bfd_boolean (*is_reloc_section
) (const char *);
337 enum elf_target_id target_id
;
338 unsigned int sizeof_reloc
;
339 unsigned int dt_reloc
;
340 unsigned int dt_reloc_sz
;
341 unsigned int dt_reloc_ent
;
342 unsigned int got_entry_size
;
343 unsigned int pointer_r_type
;
344 int dynamic_interpreter_size
;
345 const char *dynamic_interpreter
;
346 const char *tls_get_addr
;
349 struct elf_x86_init_table
351 /* The lazy PLT layout. */
352 const struct elf_x86_lazy_plt_layout
*lazy_plt
;
354 /* The non-lazy PLT layout. */
355 const struct elf_x86_non_lazy_plt_layout
*non_lazy_plt
;
357 /* The lazy PLT layout for IBT. */
358 const struct elf_x86_lazy_plt_layout
*lazy_ibt_plt
;
360 /* The non-lazy PLT layout for IBT. */
361 const struct elf_x86_non_lazy_plt_layout
*non_lazy_ibt_plt
;
363 /* TRUE if this is a normal x86 target. */
364 bfd_boolean normal_target
;
366 /* TRUE if this is a VxWorks x86 target. */
367 bfd_boolean is_vxworks
;
369 bfd_vma (*r_info
) (bfd_vma
, bfd_vma
);
370 bfd_vma (*r_sym
) (bfd_vma
);
373 struct elf_x86_obj_tdata
375 struct elf_obj_tdata root
;
377 /* tls_type for each local got entry. */
378 char *local_got_tls_type
;
380 /* GOTPLT entries for TLS descriptors. */
381 bfd_vma
*local_tlsdesc_gotent
;
384 enum elf_x86_plt_type
398 enum elf_x86_plt_type type
;
399 unsigned int plt_got_offset
;
400 unsigned int plt_entry_size
;
401 unsigned int plt_got_insn_size
; /* Only used for x86-64. */
405 #define elf_x86_tdata(abfd) \
406 ((struct elf_x86_obj_tdata *) (abfd)->tdata.any)
408 #define elf_x86_local_got_tls_type(abfd) \
409 (elf_x86_tdata (abfd)->local_got_tls_type)
411 #define elf_x86_local_tlsdesc_gotent(abfd) \
412 (elf_x86_tdata (abfd)->local_tlsdesc_gotent)
414 #define elf_x86_compute_jump_table_size(htab) \
415 ((htab)->elf.srelplt->reloc_count * (htab)->got_entry_size)
417 #define is_x86_elf(bfd, htab) \
418 (bfd_get_flavour (bfd) == bfd_target_elf_flavour \
419 && elf_tdata (bfd) != NULL \
420 && elf_object_id (bfd) == (htab)->target_id)
422 extern bfd_boolean _bfd_x86_elf_mkobject
425 extern void _bfd_x86_elf_set_tls_module_base
426 (struct bfd_link_info
*);
428 extern bfd_vma _bfd_x86_elf_dtpoff_base
429 (struct bfd_link_info
*);
431 extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs
432 (struct elf_link_hash_entry
*, void *);
434 extern struct elf_link_hash_entry
* _bfd_elf_x86_get_local_sym_hash
435 (struct elf_x86_link_hash_table
*, bfd
*, const Elf_Internal_Rela
*,
438 extern hashval_t _bfd_x86_elf_local_htab_hash
441 extern int _bfd_x86_elf_local_htab_eq
442 (const void *, const void *);
444 extern struct bfd_hash_entry
* _bfd_x86_elf_link_hash_newfunc
445 (struct bfd_hash_entry
*, struct bfd_hash_table
*, const char *);
447 extern struct bfd_link_hash_table
* _bfd_x86_elf_link_hash_table_create
450 extern int _bfd_x86_elf_compare_relocs
451 (const void *, const void *);
453 extern bfd_boolean _bfd_x86_elf_link_check_relocs
454 (bfd
*, struct bfd_link_info
*);
456 extern bfd_boolean _bfd_x86_elf_size_dynamic_sections
457 (bfd
*, struct bfd_link_info
*);
459 extern bfd_boolean _bfd_x86_elf_always_size_sections
460 (bfd
*, struct bfd_link_info
*);
462 extern void _bfd_x86_elf_merge_symbol_attribute
463 (struct elf_link_hash_entry
*, const Elf_Internal_Sym
*,
464 bfd_boolean
, bfd_boolean
);
466 extern void _bfd_x86_elf_copy_indirect_symbol
467 (struct bfd_link_info
*, struct elf_link_hash_entry
*,
468 struct elf_link_hash_entry
*);
470 extern bfd_boolean _bfd_x86_elf_fixup_symbol
471 (struct bfd_link_info
*, struct elf_link_hash_entry
*);
473 extern bfd_boolean _bfd_x86_elf_hash_symbol
474 (struct elf_link_hash_entry
*);
476 extern bfd_boolean _bfd_x86_elf_adjust_dynamic_symbol
477 (struct bfd_link_info
*, struct elf_link_hash_entry
*);
479 extern bfd_boolean _bfd_x86_elf_link_symbol_references_local
480 (struct bfd_link_info
*, struct elf_link_hash_entry
*);
482 extern asection
* _bfd_x86_elf_gc_mark_hook
483 (asection
*, struct bfd_link_info
*, Elf_Internal_Rela
*,
484 struct elf_link_hash_entry
*, Elf_Internal_Sym
*);
486 extern long _bfd_x86_elf_get_synthetic_symtab
487 (bfd
*, long, long, bfd_vma
, struct elf_x86_plt
[], asymbol
**,
490 extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties
491 (bfd
*, unsigned int, bfd_byte
*, unsigned int);
493 extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
494 (struct bfd_link_info
*, bfd
*, elf_property
*, elf_property
*);
496 extern bfd
* _bfd_x86_elf_link_setup_gnu_properties
497 (struct bfd_link_info
*, struct elf_x86_init_table
*);
499 #define bfd_elf64_mkobject \
500 _bfd_x86_elf_mkobject
501 #define bfd_elf32_mkobject \
502 _bfd_x86_elf_mkobject
503 #define bfd_elf64_bfd_link_hash_table_create \
504 _bfd_x86_elf_link_hash_table_create
505 #define bfd_elf32_bfd_link_hash_table_create \
506 _bfd_x86_elf_link_hash_table_create
507 #define bfd_elf64_bfd_link_check_relocs \
508 _bfd_x86_elf_link_check_relocs
509 #define bfd_elf32_bfd_link_check_relocs \
510 _bfd_x86_elf_link_check_relocs
512 #define elf_backend_size_dynamic_sections \
513 _bfd_x86_elf_size_dynamic_sections
514 #define elf_backend_always_size_sections \
515 _bfd_x86_elf_always_size_sections
516 #define elf_backend_merge_symbol_attribute \
517 _bfd_x86_elf_merge_symbol_attribute
518 #define elf_backend_copy_indirect_symbol \
519 _bfd_x86_elf_copy_indirect_symbol
520 #define elf_backend_fixup_symbol \
521 _bfd_x86_elf_fixup_symbol
522 #define elf_backend_hash_symbol \
523 _bfd_x86_elf_hash_symbol
524 #define elf_backend_adjust_dynamic_symbol \
525 _bfd_x86_elf_adjust_dynamic_symbol
526 #define elf_backend_gc_mark_hook \
527 _bfd_x86_elf_gc_mark_hook
528 #define elf_backend_omit_section_dynsym \
529 ((bfd_boolean (*) (bfd *, struct bfd_link_info *, asection *)) bfd_true)
530 #define elf_backend_parse_gnu_properties \
531 _bfd_x86_elf_parse_gnu_properties
532 #define elf_backend_merge_gnu_properties \
533 _bfd_x86_elf_merge_gnu_properties