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 ABI_64_P(abfd) \
30 (get_elf_backend_data (abfd)->s->elfclass == ELFCLASS64)
32 /* If ELIMINATE_COPY_RELOCS is non-zero, the linker will try to avoid
33 copying dynamic variables from a shared lib into an app's dynbss
34 section, and instead use a dynamic relocation to point into the
36 #define ELIMINATE_COPY_RELOCS 1
38 #define elf_x86_hash_table(p, id) \
39 (elf_hash_table_id ((struct elf_link_hash_table *) ((p)->hash)) == (id) \
40 ? ((struct elf_x86_link_hash_table *) ((p)->hash)) : NULL)
42 /* Is a undefined weak symbol which is resolved to 0. Reference to an
43 undefined weak symbol is resolved to 0 when building executable if
45 1. Has non-GOT/non-PLT relocations in text section. Or
46 2. Has no GOT/PLT relocation.
47 Local undefined weak symbol is always resolved to 0.
49 #define UNDEFINED_WEAK_RESOLVED_TO_ZERO(INFO, ID, GOT_RELOC, EH) \
50 ((EH)->elf.root.type == bfd_link_hash_undefweak \
51 && ((EH)->elf.forced_local \
52 || (bfd_link_executable (INFO) \
53 && (elf_x86_hash_table ((INFO), (ID))->interp == NULL \
55 || (EH)->has_non_got_reloc \
56 || !(INFO)->dynamic_undefined_weak))))
58 /* Should copy relocation be generated for a symbol. Don't generate
59 copy relocation against a protected symbol defined in a shared
60 object with GNU_PROPERTY_NO_COPY_ON_PROTECTED. */
61 #define SYMBOL_NO_COPYRELOC(INFO, EH) \
62 ((EH)->def_protected \
63 && ((EH)->elf.root.type == bfd_link_hash_defined \
64 || (EH)->elf.root.type == bfd_link_hash_defweak) \
65 && elf_has_no_copy_on_protected ((EH)->elf.root.u.def.section->owner) \
66 && ((EH)->elf.root.u.def.section->owner->flags & DYNAMIC) != 0 \
67 && ((EH)->elf.root.u.def.section->flags & SEC_CODE) == 0)
69 /* x86 ELF linker hash entry. */
71 struct elf_x86_link_hash_entry
73 struct elf_link_hash_entry elf;
75 /* Track dynamic relocs copied for this symbol. */
76 struct elf_dyn_relocs *dyn_relocs;
78 unsigned char tls_type;
80 /* TRUE if symbol has GOT or PLT relocations. */
81 unsigned int has_got_reloc : 1;
83 /* TRUE if symbol has non-GOT/non-PLT relocations in text sections. */
84 unsigned int has_non_got_reloc : 1;
86 /* Don't call finish_dynamic_symbol on this symbol. */
87 unsigned int no_finish_dynamic_symbol : 1;
89 /* TRUE if symbol is __tls_get_addr. */
90 unsigned int tls_get_addr : 1;
92 /* TRUE if symbol is defined as a protected symbol. */
93 unsigned int def_protected : 1;
95 /* Symbol is referenced by R_386_GOTOFF relocation. This is only used
97 unsigned int gotoff_ref : 1;
99 /* TRUE if a weak symbol with a real definition needs a copy reloc.
100 When there is a weak symbol with a real definition, the processor
101 independent code will have arranged for us to see the real
102 definition first. We need to copy the needs_copy bit from the
103 real definition and check it when allowing copy reloc in PIE. This
104 is only used by x86-64. */
105 unsigned int needs_copy : 1;
107 /* Reference count of C/C++ function pointer relocations in read-write
108 section which can be resolved at run-time. */
109 bfd_signed_vma func_pointer_refcount;
111 /* Information about the GOT PLT entry. Filled when there are both
112 GOT and PLT relocations against the same function. */
113 union gotplt_union plt_got;
115 /* Information about the second PLT entry. */
116 union gotplt_union plt_second;
118 /* Offset of the GOTPLT entry reserved for the TLS descriptor,
119 starting at the end of the jump table. */
123 struct elf_x86_lazy_plt_layout
125 /* The first entry in an absolute lazy procedure linkage table looks
127 const bfd_byte *plt0_entry;
128 unsigned int plt0_entry_size; /* Size of PLT0 entry. */
130 /* Later entries in an absolute lazy procedure linkage table look
132 const bfd_byte *plt_entry;
133 unsigned int plt_entry_size; /* Size of each PLT entry. */
135 /* Offsets into plt0_entry that are to be replaced with GOT[1] and
137 unsigned int plt0_got1_offset;
138 unsigned int plt0_got2_offset;
140 /* Offset of the end of the PC-relative instruction containing
141 plt0_got2_offset. This is for x86-64 only. */
142 unsigned int plt0_got2_insn_end;
144 /* Offsets into plt_entry that are to be replaced with... */
145 unsigned int plt_got_offset; /* ... address of this symbol in .got. */
146 unsigned int plt_reloc_offset; /* ... offset into relocation table. */
147 unsigned int plt_plt_offset; /* ... offset to start of .plt. */
149 /* Length of the PC-relative instruction containing plt_got_offset.
150 This is used for x86-64 only. */
151 unsigned int plt_got_insn_size;
153 /* Offset of the end of the PC-relative jump to plt0_entry. This is
154 used for x86-64 only. */
155 unsigned int plt_plt_insn_end;
157 /* Offset into plt_entry where the initial value of the GOT entry
159 unsigned int plt_lazy_offset;
161 /* The first entry in a PIC lazy procedure linkage table looks like
163 const bfd_byte *pic_plt0_entry;
165 /* Subsequent entries in a PIC lazy procedure linkage table look
167 const bfd_byte *pic_plt_entry;
169 /* .eh_frame covering the lazy .plt section. */
170 const bfd_byte *eh_frame_plt;
171 unsigned int eh_frame_plt_size;
174 struct elf_x86_non_lazy_plt_layout
176 /* Entries in an absolute non-lazy procedure linkage table look like
178 const bfd_byte *plt_entry;
179 /* Entries in a PIC non-lazy procedure linkage table look like this. */
180 const bfd_byte *pic_plt_entry;
182 unsigned int plt_entry_size; /* Size of each PLT entry. */
184 /* Offsets into plt_entry that are to be replaced with... */
185 unsigned int plt_got_offset; /* ... address of this symbol in .got. */
187 /* Length of the PC-relative instruction containing plt_got_offset.
188 This is used for x86-64 only. */
189 unsigned int plt_got_insn_size;
191 /* .eh_frame covering the non-lazy .plt section. */
192 const bfd_byte *eh_frame_plt;
193 unsigned int eh_frame_plt_size;
196 struct elf_x86_plt_layout
198 /* The first entry in a lazy procedure linkage table looks like this.
199 This is only used for i386 where absolute PLT0 and PIC PLT0 are
201 const bfd_byte *plt0_entry;
202 /* Entries in a procedure linkage table look like this. */
203 const bfd_byte *plt_entry;
204 unsigned int plt_entry_size; /* Size of each PLT entry. */
207 unsigned int has_plt0;
209 /* Offsets into plt_entry that are to be replaced with... */
210 unsigned int plt_got_offset; /* ... address of this symbol in .got. */
212 /* Length of the PC-relative instruction containing plt_got_offset.
213 This is only used for x86-64. */
214 unsigned int plt_got_insn_size;
216 /* .eh_frame covering the .plt section. */
217 const bfd_byte *eh_frame_plt;
218 unsigned int eh_frame_plt_size;
221 /* The first 3 values in tls_type of x86 ELF linker hash entry. */
222 #define GOT_UNKNOWN 0
226 #define elf_x86_hash_entry(ent) \
227 ((struct elf_x86_link_hash_entry *)(ent))
229 /* x86 ELF linker hash table. */
231 struct elf_x86_link_hash_table
233 struct elf_link_hash_table elf;
235 /* Short-cuts to get to dynamic linker sections. */
237 asection *plt_eh_frame;
238 asection *plt_second;
239 asection *plt_second_eh_frame;
241 asection *plt_got_eh_frame;
243 /* Parameters describing PLT generation, lazy or non-lazy. */
244 struct elf_x86_plt_layout plt;
246 /* Parameters describing lazy PLT generation. */
247 const struct elf_x86_lazy_plt_layout *lazy_plt;
249 /* Parameters describing non-lazy PLT generation. */
250 const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
254 bfd_signed_vma refcount;
258 /* The amount of space used by the jump slots in the GOT. */
259 bfd_vma sgotplt_jump_table_size;
261 /* Small local sym cache. */
262 struct sym_cache sym_cache;
264 /* _TLS_MODULE_BASE_ symbol. */
265 struct bfd_link_hash_entry *tls_module_base;
267 /* Used by local STT_GNU_IFUNC symbols. */
268 htab_t loc_hash_table;
269 void * loc_hash_memory;
271 /* The offset into splt of the PLT entry for the TLS descriptor
272 resolver. Special values are 0, if not necessary (or not found
273 to be necessary yet), and -1 if needed but not determined
277 /* The offset into sgot of the GOT entry used by the PLT entry
281 /* The index of the next R_X86_64_JUMP_SLOT entry in .rela.plt. */
282 bfd_vma next_jump_slot_index;
283 /* The index of the next R_X86_64_IRELATIVE entry in .rela.plt. */
284 bfd_vma next_irelative_index;
286 /* TRUE if there are dynamic relocs against IFUNC symbols that apply
287 to read-only sections. */
288 bfd_boolean readonly_dynrelocs_against_ifunc;
290 /* TRUE if this is a VxWorks x86 target. */
291 bfd_boolean is_vxworks;
293 /* The (unloaded but important) .rel.plt.unloaded section on VxWorks.
294 This is used for i386 only. */
297 /* The index of the next unused R_386_TLS_DESC slot in .rel.plt. This
298 is used for i386 only. */
299 bfd_vma next_tls_desc_index;
301 bfd_vma (*r_info) (bfd_vma, bfd_vma);
302 bfd_vma (*r_sym) (bfd_vma);
303 unsigned int pointer_r_type;
304 int dynamic_interpreter_size;
305 const char *dynamic_interpreter;
306 const char *tls_get_addr;
309 struct elf_x86_plt_layout_table
311 /* The lazy PLT layout. */
312 const struct elf_x86_lazy_plt_layout *lazy_plt;
314 /* The non-lazy PLT layout. */
315 const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
317 /* The lazy PLT layout for IBT. */
318 const struct elf_x86_lazy_plt_layout *lazy_ibt_plt;
320 /* The non-lazy PLT layout for IBT. */
321 const struct elf_x86_non_lazy_plt_layout *non_lazy_ibt_plt;
323 /* TRUE if this is a normal x86 target. */
324 bfd_boolean normal_target;
326 /* TRUE if this is a VxWorks x86 target. */
327 bfd_boolean is_vxworks;
330 struct elf_x86_obj_tdata
332 struct elf_obj_tdata root;
334 /* tls_type for each local got entry. */
335 char *local_got_tls_type;
337 /* GOTPLT entries for TLS descriptors. */
338 bfd_vma *local_tlsdesc_gotent;
341 enum elf_x86_plt_type
355 enum elf_x86_plt_type type;
356 unsigned int plt_got_offset;
357 unsigned int plt_entry_size;
358 unsigned int plt_got_insn_size; /* Only used for x86-64. */
362 #define elf_x86_tdata(abfd) \
363 ((struct elf_x86_obj_tdata *) (abfd)->tdata.any)
365 #define elf_x86_local_got_tls_type(abfd) \
366 (elf_x86_tdata (abfd)->local_got_tls_type)
368 #define elf_x86_local_tlsdesc_gotent(abfd) \
369 (elf_x86_tdata (abfd)->local_tlsdesc_gotent)
371 extern bfd_boolean _bfd_x86_elf_mkobject
374 extern void _bfd_x86_elf_set_tls_module_base
375 (struct bfd_link_info *);
377 extern bfd_vma _bfd_x86_elf_dtpoff_base
378 (struct bfd_link_info *);
380 extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs
381 (struct elf_link_hash_entry *, void *);
383 extern struct elf_link_hash_entry * _bfd_elf_x86_get_local_sym_hash
384 (struct elf_x86_link_hash_table *, bfd *, const Elf_Internal_Rela *,
387 extern hashval_t _bfd_x86_elf_local_htab_hash
390 extern int _bfd_x86_elf_local_htab_eq
391 (const void *, const void *);
393 extern struct bfd_hash_entry * _bfd_x86_elf_link_hash_newfunc
394 (struct bfd_hash_entry *, struct bfd_hash_table *, const char *);
396 extern struct bfd_link_hash_table * _bfd_x86_elf_link_hash_table_create
399 extern int _bfd_x86_elf_compare_relocs
400 (const void *, const void *);
402 extern bfd_boolean _bfd_x86_elf_link_check_relocs
403 (bfd *, struct bfd_link_info *);
405 extern bfd_boolean _bfd_x86_elf_always_size_sections
406 (bfd *, struct bfd_link_info *);
408 extern void _bfd_x86_elf_merge_symbol_attribute
409 (struct elf_link_hash_entry *, const Elf_Internal_Sym *,
410 bfd_boolean, bfd_boolean);
412 extern void _bfd_x86_elf_copy_indirect_symbol
413 (struct bfd_link_info *, struct elf_link_hash_entry *,
414 struct elf_link_hash_entry *);
416 extern bfd_boolean _bfd_x86_elf_fixup_symbol
417 (struct bfd_link_info *, struct elf_link_hash_entry *);
419 extern bfd_boolean _bfd_x86_elf_hash_symbol
420 (struct elf_link_hash_entry *);
422 extern bfd_boolean _bfd_x86_elf_adjust_dynamic_symbol
423 (struct bfd_link_info *, struct elf_link_hash_entry *);
425 extern long _bfd_x86_elf_get_synthetic_symtab
426 (bfd *, long, long, bfd_vma, struct elf_x86_plt [], asymbol **,
429 extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties
430 (bfd *, unsigned int, bfd_byte *, unsigned int);
432 extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
433 (struct bfd_link_info *, bfd *, elf_property *, elf_property *);
435 extern bfd * _bfd_x86_elf_link_setup_gnu_properties
436 (struct bfd_link_info *, struct elf_x86_plt_layout_table *);
438 #define bfd_elf64_mkobject \
439 _bfd_x86_elf_mkobject
440 #define bfd_elf32_mkobject \
441 _bfd_x86_elf_mkobject
442 #define bfd_elf64_bfd_link_hash_table_create \
443 _bfd_x86_elf_link_hash_table_create
444 #define bfd_elf32_bfd_link_hash_table_create \
445 _bfd_x86_elf_link_hash_table_create
446 #define bfd_elf64_bfd_link_check_relocs \
447 _bfd_x86_elf_link_check_relocs
448 #define bfd_elf32_bfd_link_check_relocs \
449 _bfd_x86_elf_link_check_relocs
451 #define elf_backend_always_size_sections \
452 _bfd_x86_elf_always_size_sections
453 #define elf_backend_merge_symbol_attribute \
454 _bfd_x86_elf_merge_symbol_attribute
455 #define elf_backend_copy_indirect_symbol \
456 _bfd_x86_elf_copy_indirect_symbol
457 #define elf_backend_fixup_symbol \
458 _bfd_x86_elf_fixup_symbol
459 #define elf_backend_hash_symbol \
460 _bfd_x86_elf_hash_symbol
461 #define elf_backend_adjust_dynamic_symbol \
462 _bfd_x86_elf_adjust_dynamic_symbol
463 #define elf_backend_omit_section_dynsym \
464 ((bfd_boolean (*) (bfd *, struct bfd_link_info *, asection *)) bfd_true)
465 #define elf_backend_parse_gnu_properties \
466 _bfd_x86_elf_parse_gnu_properties
467 #define elf_backend_merge_gnu_properties \
468 _bfd_x86_elf_merge_gnu_properties