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 TLS IE->LE transition is OK. */
78 #define TLS_TRANSITION_IE_TO_LE_P(INFO, H, TLS_TYPE) \
79 (bfd_link_executable (INFO) \
81 && (H)->dynindx == -1 \
82 && (TLS_TYPE & GOT_TLS_IE))
84 /* x86 ELF linker hash entry. */
86 struct elf_x86_link_hash_entry
88 struct elf_link_hash_entry elf;
90 /* Track dynamic relocs copied for this symbol. */
91 struct elf_dyn_relocs *dyn_relocs;
93 unsigned char tls_type;
95 /* TRUE if symbol has GOT or PLT relocations. */
96 unsigned int has_got_reloc : 1;
98 /* TRUE if symbol has non-GOT/non-PLT relocations in text sections. */
99 unsigned int has_non_got_reloc : 1;
101 /* Don't call finish_dynamic_symbol on this symbol. */
102 unsigned int no_finish_dynamic_symbol : 1;
104 /* TRUE if symbol is __tls_get_addr. */
105 unsigned int tls_get_addr : 1;
107 /* TRUE if symbol is defined as a protected symbol. */
108 unsigned int def_protected : 1;
110 /* 0: Symbol references are unknown.
111 1: Symbol references aren't local.
112 2: Symbol references are local.
114 unsigned int local_ref : 2;
116 /* TRUE if symbol is defined by linker. */
117 unsigned int linker_def : 1;
119 /* TRUE if symbol is referenced by R_386_GOTOFF relocation. This is
120 only used by i386. */
121 unsigned int gotoff_ref : 1;
123 /* TRUE if a weak symbol with a real definition needs a copy reloc.
124 When there is a weak symbol with a real definition, the processor
125 independent code will have arranged for us to see the real
126 definition first. We need to copy the needs_copy bit from the
127 real definition and check it when allowing copy reloc in PIE. This
128 is only used by x86-64. */
129 unsigned int needs_copy : 1;
131 /* Reference count of C/C++ function pointer relocations in read-write
132 section which can be resolved at run-time. */
133 bfd_signed_vma func_pointer_refcount;
135 /* Information about the GOT PLT entry. Filled when there are both
136 GOT and PLT relocations against the same function. */
137 union gotplt_union plt_got;
139 /* Information about the second PLT entry. */
140 union gotplt_union plt_second;
142 /* Offset of the GOTPLT entry reserved for the TLS descriptor,
143 starting at the end of the jump table. */
147 struct elf_x86_lazy_plt_layout
149 /* The first entry in an absolute lazy procedure linkage table looks
151 const bfd_byte *plt0_entry;
152 unsigned int plt0_entry_size; /* Size of PLT0 entry. */
154 /* Later entries in an absolute lazy procedure linkage table look
156 const bfd_byte *plt_entry;
157 unsigned int plt_entry_size; /* Size of each PLT entry. */
159 /* Offsets into plt0_entry that are to be replaced with GOT[1] and
161 unsigned int plt0_got1_offset;
162 unsigned int plt0_got2_offset;
164 /* Offset of the end of the PC-relative instruction containing
165 plt0_got2_offset. This is for x86-64 only. */
166 unsigned int plt0_got2_insn_end;
168 /* Offsets into plt_entry that are to be replaced with... */
169 unsigned int plt_got_offset; /* ... address of this symbol in .got. */
170 unsigned int plt_reloc_offset; /* ... offset into relocation table. */
171 unsigned int plt_plt_offset; /* ... offset to start of .plt. */
173 /* Length of the PC-relative instruction containing plt_got_offset.
174 This is used for x86-64 only. */
175 unsigned int plt_got_insn_size;
177 /* Offset of the end of the PC-relative jump to plt0_entry. This is
178 used for x86-64 only. */
179 unsigned int plt_plt_insn_end;
181 /* Offset into plt_entry where the initial value of the GOT entry
183 unsigned int plt_lazy_offset;
185 /* The first entry in a PIC lazy procedure linkage table looks like
187 const bfd_byte *pic_plt0_entry;
189 /* Subsequent entries in a PIC lazy procedure linkage table look
191 const bfd_byte *pic_plt_entry;
193 /* .eh_frame covering the lazy .plt section. */
194 const bfd_byte *eh_frame_plt;
195 unsigned int eh_frame_plt_size;
198 struct elf_x86_non_lazy_plt_layout
200 /* Entries in an absolute non-lazy procedure linkage table look like
202 const bfd_byte *plt_entry;
203 /* Entries in a PIC non-lazy procedure linkage table look like this. */
204 const bfd_byte *pic_plt_entry;
206 unsigned int plt_entry_size; /* Size of each PLT entry. */
208 /* Offsets into plt_entry that are to be replaced with... */
209 unsigned int plt_got_offset; /* ... address of this symbol in .got. */
211 /* Length of the PC-relative instruction containing plt_got_offset.
212 This is used for x86-64 only. */
213 unsigned int plt_got_insn_size;
215 /* .eh_frame covering the non-lazy .plt section. */
216 const bfd_byte *eh_frame_plt;
217 unsigned int eh_frame_plt_size;
220 struct elf_x86_plt_layout
222 /* The first entry in a lazy procedure linkage table looks like this.
223 This is only used for i386 where absolute PLT0 and PIC PLT0 are
225 const bfd_byte *plt0_entry;
226 /* Entries in a procedure linkage table look like this. */
227 const bfd_byte *plt_entry;
228 unsigned int plt_entry_size; /* Size of each PLT entry. */
231 unsigned int has_plt0;
233 /* Offsets into plt_entry that are to be replaced with... */
234 unsigned int plt_got_offset; /* ... address of this symbol in .got. */
236 /* Length of the PC-relative instruction containing plt_got_offset.
237 This is only used for x86-64. */
238 unsigned int plt_got_insn_size;
240 /* .eh_frame covering the .plt section. */
241 const bfd_byte *eh_frame_plt;
242 unsigned int eh_frame_plt_size;
245 /* Values in tls_type of x86 ELF linker hash entry. */
246 #define GOT_UNKNOWN 0
250 #define GOT_TLS_IE_POS 5
251 #define GOT_TLS_IE_NEG 6
252 #define GOT_TLS_IE_BOTH 7
253 #define GOT_TLS_GDESC 8
254 #define GOT_TLS_GD_BOTH_P(type) \
255 ((type) == (GOT_TLS_GD | GOT_TLS_GDESC))
256 #define GOT_TLS_GD_P(type) \
257 ((type) == GOT_TLS_GD || GOT_TLS_GD_BOTH_P (type))
258 #define GOT_TLS_GDESC_P(type) \
259 ((type) == GOT_TLS_GDESC || GOT_TLS_GD_BOTH_P (type))
260 #define GOT_TLS_GD_ANY_P(type) \
261 (GOT_TLS_GD_P (type) || GOT_TLS_GDESC_P (type))
263 #define elf_x86_hash_entry(ent) \
264 ((struct elf_x86_link_hash_entry *)(ent))
266 /* x86 ELF linker hash table. */
268 struct elf_x86_link_hash_table
270 struct elf_link_hash_table elf;
272 /* Short-cuts to get to dynamic linker sections. */
274 asection *plt_eh_frame;
275 asection *plt_second;
276 asection *plt_second_eh_frame;
278 asection *plt_got_eh_frame;
280 /* Parameters describing PLT generation, lazy or non-lazy. */
281 struct elf_x86_plt_layout plt;
283 /* Parameters describing lazy PLT generation. */
284 const struct elf_x86_lazy_plt_layout *lazy_plt;
286 /* Parameters describing non-lazy PLT generation. */
287 const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
291 bfd_signed_vma refcount;
295 /* The amount of space used by the jump slots in the GOT. */
296 bfd_vma sgotplt_jump_table_size;
298 /* Small local sym cache. */
299 struct sym_cache sym_cache;
301 /* _TLS_MODULE_BASE_ symbol. */
302 struct bfd_link_hash_entry *tls_module_base;
304 /* Used by local STT_GNU_IFUNC symbols. */
305 htab_t loc_hash_table;
306 void * loc_hash_memory;
308 /* The offset into sgot of the GOT entry used by the PLT entry
312 /* The index of the next R_X86_64_JUMP_SLOT entry in .rela.plt. */
313 bfd_vma next_jump_slot_index;
314 /* The index of the next R_X86_64_IRELATIVE entry in .rela.plt. */
315 bfd_vma next_irelative_index;
317 /* TRUE if there are dynamic relocs against IFUNC symbols that apply
318 to read-only sections. */
319 bfd_boolean readonly_dynrelocs_against_ifunc;
321 /* TRUE if this is a VxWorks x86 target. This is only used for
323 bfd_boolean is_vxworks;
325 /* The (unloaded but important) .rel.plt.unloaded section on VxWorks.
326 This is used for i386 only. */
329 /* The index of the next unused R_386_TLS_DESC slot in .rel.plt. This
330 is only used for i386. */
331 bfd_vma next_tls_desc_index;
333 /* The offset into splt of the PLT entry for the TLS descriptor
334 resolver. Special values are 0, if not necessary (or not found
335 to be necessary yet), and -1 if needed but not determined
336 yet. This is only used for x86-64. */
339 bfd_vma (*r_info) (bfd_vma, bfd_vma);
340 bfd_vma (*r_sym) (bfd_vma);
341 bfd_boolean (*is_reloc_section) (const char *);
342 enum elf_target_id target_id;
343 unsigned int sizeof_reloc;
344 unsigned int dt_reloc;
345 unsigned int dt_reloc_sz;
346 unsigned int dt_reloc_ent;
347 unsigned int got_entry_size;
348 unsigned int pointer_r_type;
349 int dynamic_interpreter_size;
350 const char *dynamic_interpreter;
351 const char *tls_get_addr;
354 struct elf_x86_init_table
356 /* The lazy PLT layout. */
357 const struct elf_x86_lazy_plt_layout *lazy_plt;
359 /* The non-lazy PLT layout. */
360 const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
362 /* The lazy PLT layout for IBT. */
363 const struct elf_x86_lazy_plt_layout *lazy_ibt_plt;
365 /* The non-lazy PLT layout for IBT. */
366 const struct elf_x86_non_lazy_plt_layout *non_lazy_ibt_plt;
368 /* TRUE if this is a normal x86 target. */
369 bfd_boolean normal_target;
371 /* TRUE if this is a VxWorks x86 target. */
372 bfd_boolean is_vxworks;
374 bfd_vma (*r_info) (bfd_vma, bfd_vma);
375 bfd_vma (*r_sym) (bfd_vma);
378 struct elf_x86_obj_tdata
380 struct elf_obj_tdata root;
382 /* tls_type for each local got entry. */
383 char *local_got_tls_type;
385 /* GOTPLT entries for TLS descriptors. */
386 bfd_vma *local_tlsdesc_gotent;
389 enum elf_x86_plt_type
403 enum elf_x86_plt_type type;
404 unsigned int plt_got_offset;
405 unsigned int plt_entry_size;
406 unsigned int plt_got_insn_size; /* Only used for x86-64. */
410 #define elf_x86_tdata(abfd) \
411 ((struct elf_x86_obj_tdata *) (abfd)->tdata.any)
413 #define elf_x86_local_got_tls_type(abfd) \
414 (elf_x86_tdata (abfd)->local_got_tls_type)
416 #define elf_x86_local_tlsdesc_gotent(abfd) \
417 (elf_x86_tdata (abfd)->local_tlsdesc_gotent)
419 #define elf_x86_compute_jump_table_size(htab) \
420 ((htab)->elf.srelplt->reloc_count * (htab)->got_entry_size)
422 #define is_x86_elf(bfd, htab) \
423 (bfd_get_flavour (bfd) == bfd_target_elf_flavour \
424 && elf_tdata (bfd) != NULL \
425 && elf_object_id (bfd) == (htab)->target_id)
427 extern bfd_boolean _bfd_x86_elf_mkobject
430 extern void _bfd_x86_elf_set_tls_module_base
431 (struct bfd_link_info *);
433 extern bfd_vma _bfd_x86_elf_dtpoff_base
434 (struct bfd_link_info *);
436 extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs
437 (struct elf_link_hash_entry *, void *);
439 extern struct elf_link_hash_entry * _bfd_elf_x86_get_local_sym_hash
440 (struct elf_x86_link_hash_table *, bfd *, const Elf_Internal_Rela *,
443 extern hashval_t _bfd_x86_elf_local_htab_hash
446 extern int _bfd_x86_elf_local_htab_eq
447 (const void *, const void *);
449 extern struct bfd_hash_entry * _bfd_x86_elf_link_hash_newfunc
450 (struct bfd_hash_entry *, struct bfd_hash_table *, const char *);
452 extern struct bfd_link_hash_table * _bfd_x86_elf_link_hash_table_create
455 extern int _bfd_x86_elf_compare_relocs
456 (const void *, const void *);
458 extern bfd_boolean _bfd_x86_elf_link_check_relocs
459 (bfd *, struct bfd_link_info *);
461 extern bfd_boolean _bfd_x86_elf_size_dynamic_sections
462 (bfd *, struct bfd_link_info *);
464 extern bfd_boolean _bfd_x86_elf_always_size_sections
465 (bfd *, struct bfd_link_info *);
467 extern void _bfd_x86_elf_merge_symbol_attribute
468 (struct elf_link_hash_entry *, const Elf_Internal_Sym *,
469 bfd_boolean, bfd_boolean);
471 extern void _bfd_x86_elf_copy_indirect_symbol
472 (struct bfd_link_info *, struct elf_link_hash_entry *,
473 struct elf_link_hash_entry *);
475 extern bfd_boolean _bfd_x86_elf_fixup_symbol
476 (struct bfd_link_info *, struct elf_link_hash_entry *);
478 extern bfd_boolean _bfd_x86_elf_hash_symbol
479 (struct elf_link_hash_entry *);
481 extern bfd_boolean _bfd_x86_elf_adjust_dynamic_symbol
482 (struct bfd_link_info *, struct elf_link_hash_entry *);
484 extern bfd_boolean _bfd_x86_elf_link_symbol_references_local
485 (struct bfd_link_info *, struct elf_link_hash_entry *);
487 extern asection * _bfd_x86_elf_gc_mark_hook
488 (asection *, struct bfd_link_info *, Elf_Internal_Rela *,
489 struct elf_link_hash_entry *, Elf_Internal_Sym *);
491 extern long _bfd_x86_elf_get_synthetic_symtab
492 (bfd *, long, long, bfd_vma, struct elf_x86_plt [], asymbol **,
495 extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties
496 (bfd *, unsigned int, bfd_byte *, unsigned int);
498 extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
499 (struct bfd_link_info *, bfd *, elf_property *, elf_property *);
501 extern bfd * _bfd_x86_elf_link_setup_gnu_properties
502 (struct bfd_link_info *, struct elf_x86_init_table *);
504 #define bfd_elf64_mkobject \
505 _bfd_x86_elf_mkobject
506 #define bfd_elf32_mkobject \
507 _bfd_x86_elf_mkobject
508 #define bfd_elf64_bfd_link_hash_table_create \
509 _bfd_x86_elf_link_hash_table_create
510 #define bfd_elf32_bfd_link_hash_table_create \
511 _bfd_x86_elf_link_hash_table_create
512 #define bfd_elf64_bfd_link_check_relocs \
513 _bfd_x86_elf_link_check_relocs
514 #define bfd_elf32_bfd_link_check_relocs \
515 _bfd_x86_elf_link_check_relocs
517 #define elf_backend_size_dynamic_sections \
518 _bfd_x86_elf_size_dynamic_sections
519 #define elf_backend_always_size_sections \
520 _bfd_x86_elf_always_size_sections
521 #define elf_backend_merge_symbol_attribute \
522 _bfd_x86_elf_merge_symbol_attribute
523 #define elf_backend_copy_indirect_symbol \
524 _bfd_x86_elf_copy_indirect_symbol
525 #define elf_backend_fixup_symbol \
526 _bfd_x86_elf_fixup_symbol
527 #define elf_backend_hash_symbol \
528 _bfd_x86_elf_hash_symbol
529 #define elf_backend_adjust_dynamic_symbol \
530 _bfd_x86_elf_adjust_dynamic_symbol
531 #define elf_backend_gc_mark_hook \
532 _bfd_x86_elf_gc_mark_hook
533 #define elf_backend_omit_section_dynsym \
534 ((bfd_boolean (*) (bfd *, struct bfd_link_info *, asection *)) bfd_true)
535 #define elf_backend_parse_gnu_properties \
536 _bfd_x86_elf_parse_gnu_properties
537 #define elf_backend_merge_gnu_properties \
538 _bfd_x86_elf_merge_gnu_properties