bfd/elfxx-x86.h

   1 /* x86 specific support for ELF
   2    Copyright (C) 2017 Free Software Foundation, Inc.
   3
   4    This file is part of BFD, the Binary File Descriptor library.
   5
   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.
  10
  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.
  15
  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.  */
  20
  21 #include "sysdep.h"
  22 #include "bfd.h"
  23 #include "bfdlink.h"
  24 #include "libbfd.h"
  25 #include "elf-bfd.h"
  26 #include "bfd_stdint.h"
  27 #include "hashtab.h"
  28
  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
  33
  34 #define ABI_64_P(abfd) \
  35   (get_elf_backend_data (abfd)->s->elfclass == ELFCLASS64)
  36
  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
  40    shared lib.  */
  41 #define ELIMINATE_COPY_RELOCS 1
  42
  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)
  47
  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))
  51
  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
  54    it isn't dynamic and
  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.
  58  */
  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))))
  65
  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)
  76
  77 /* x86 ELF linker hash entry.  */
  78
  79 struct elf_x86_link_hash_entry
  80 {
  81   struct elf_link_hash_entry elf;
  82
  83   /* Track dynamic relocs copied for this symbol.  */
  84   struct elf_dyn_relocs *dyn_relocs;
  85
  86   unsigned char tls_type;
  87
  88   /* TRUE if symbol has GOT or PLT relocations.  */
  89   unsigned int has_got_reloc : 1;
  90
  91   /* TRUE if symbol has non-GOT/non-PLT relocations in text sections.  */
  92   unsigned int has_non_got_reloc : 1;
  93
  94   /* Don't call finish_dynamic_symbol on this symbol.  */
  95   unsigned int no_finish_dynamic_symbol : 1;
  96
  97   /* TRUE if symbol is __tls_get_addr.  */
  98   unsigned int tls_get_addr : 1;
  99
 100   /* TRUE if symbol is defined as a protected symbol.  */
 101   unsigned int def_protected : 1;
 102
 103   /* 0: Symbol references are unknown.
 104      1: Symbol references aren't local.
 105      2: Symbol references are local.
 106    */
 107   unsigned int local_ref : 2;
 108
 109   /* TRUE if symbol is defined by linker.  */
 110   unsigned int linker_def : 1;
 111
 112   /* TRUE if symbol is referenced by R_386_GOTOFF relocation.  This is
 113      only used by i386.  */
 114   unsigned int gotoff_ref : 1;
 115
 116   /* TRUE if a weak symbol with a real definition needs a copy reloc.
 117      When there is a weak symbol with a real definition, the processor
 118      independent code will have arranged for us to see the real
 119      definition first.  We need to copy the needs_copy bit from the
 120      real definition and check it when allowing copy reloc in PIE.  This
 121      is only used by x86-64.  */
 122   unsigned int needs_copy : 1;
 123
 124   /* Reference count of C/C++ function pointer relocations in read-write
 125      section which can be resolved at run-time.  */
 126   bfd_signed_vma func_pointer_refcount;
 127
 128   /* Information about the GOT PLT entry. Filled when there are both
 129      GOT and PLT relocations against the same function.  */
 130   union gotplt_union plt_got;
 131
 132   /* Information about the second PLT entry.   */
 133   union gotplt_union plt_second;
 134
 135   /* Offset of the GOTPLT entry reserved for the TLS descriptor,
 136      starting at the end of the jump table.  */
 137   bfd_vma tlsdesc_got;
 138 };
 139
 140 struct elf_x86_lazy_plt_layout
 141 {
 142   /* The first entry in an absolute lazy procedure linkage table looks
 143      like this.  */
 144   const bfd_byte *plt0_entry;
 145   unsigned int plt0_entry_size;          /* Size of PLT0 entry.  */
 146
 147   /* Later entries in an absolute lazy procedure linkage table look
 148      like this.  */
 149   const bfd_byte *plt_entry;
 150   unsigned int plt_entry_size;          /* Size of each PLT entry.  */
 151
 152   /* Offsets into plt0_entry that are to be replaced with GOT[1] and
 153      GOT[2].  */
 154   unsigned int plt0_got1_offset;
 155   unsigned int plt0_got2_offset;
 156
 157   /* Offset of the end of the PC-relative instruction containing
 158      plt0_got2_offset.  This is for x86-64 only.  */
 159   unsigned int plt0_got2_insn_end;
 160
 161   /* Offsets into plt_entry that are to be replaced with...  */
 162   unsigned int plt_got_offset;    /* ... address of this symbol in .got. */
 163   unsigned int plt_reloc_offset;  /* ... offset into relocation table. */
 164   unsigned int plt_plt_offset;    /* ... offset to start of .plt. */
 165
 166   /* Length of the PC-relative instruction containing plt_got_offset.
 167      This is used for x86-64 only.  */
 168   unsigned int plt_got_insn_size;
 169
 170   /* Offset of the end of the PC-relative jump to plt0_entry.  This is
 171      used for x86-64 only.  */
 172   unsigned int plt_plt_insn_end;
 173
 174   /* Offset into plt_entry where the initial value of the GOT entry
 175      points.  */
 176   unsigned int plt_lazy_offset;
 177
 178   /* The first entry in a PIC lazy procedure linkage table looks like
 179      this.  */
 180   const bfd_byte *pic_plt0_entry;
 181
 182   /* Subsequent entries in a PIC lazy procedure linkage table look
 183      like this.  */
 184   const bfd_byte *pic_plt_entry;
 185
 186   /* .eh_frame covering the lazy .plt section.  */
 187   const bfd_byte *eh_frame_plt;
 188   unsigned int eh_frame_plt_size;
 189 };
 190
 191 struct elf_x86_non_lazy_plt_layout
 192 {
 193   /* Entries in an absolute non-lazy procedure linkage table look like
 194      this.  */
 195   const bfd_byte *plt_entry;
 196   /* Entries in a PIC non-lazy procedure linkage table look like this.  */
 197   const bfd_byte *pic_plt_entry;
 198
 199   unsigned int plt_entry_size;          /* Size of each PLT entry.  */
 200
 201   /* Offsets into plt_entry that are to be replaced with...  */
 202   unsigned int plt_got_offset;    /* ... address of this symbol in .got. */
 203
 204   /* Length of the PC-relative instruction containing plt_got_offset.
 205      This is used for x86-64 only.  */
 206   unsigned int plt_got_insn_size;
 207
 208   /* .eh_frame covering the non-lazy .plt section.  */
 209   const bfd_byte *eh_frame_plt;
 210   unsigned int eh_frame_plt_size;
 211 };
 212
 213 struct elf_x86_plt_layout
 214 {
 215   /* The first entry in a lazy procedure linkage table looks like this.
 216      This is only used for i386 where absolute PLT0 and PIC PLT0 are
 217      different.  */
 218   const bfd_byte *plt0_entry;
 219   /* Entries in a procedure linkage table look like this.  */
 220   const bfd_byte *plt_entry;
 221   unsigned int plt_entry_size;          /* Size of each PLT entry.  */
 222
 223   /* 1 has PLT0.  */
 224   unsigned int has_plt0;
 225
 226   /* Offsets into plt_entry that are to be replaced with...  */
 227   unsigned int plt_got_offset;    /* ... address of this symbol in .got. */
 228
 229   /* Length of the PC-relative instruction containing plt_got_offset.
 230      This is only used for x86-64.  */
 231   unsigned int plt_got_insn_size;
 232
 233   /* .eh_frame covering the .plt section.  */
 234   const bfd_byte *eh_frame_plt;
 235   unsigned int eh_frame_plt_size;
 236 };
 237
 238 /* Values in tls_type of x86 ELF linker hash entry.  */
 239 #define GOT_UNKNOWN     0
 240 #define GOT_NORMAL      1
 241 #define GOT_TLS_GD      2
 242 #define GOT_TLS_IE      4
 243 #define GOT_TLS_IE_POS  5
 244 #define GOT_TLS_IE_NEG  6
 245 #define GOT_TLS_IE_BOTH 7
 246 #define GOT_TLS_GDESC   8
 247 #define GOT_TLS_GD_BOTH_P(type) \
 248   ((type) == (GOT_TLS_GD | GOT_TLS_GDESC))
 249 #define GOT_TLS_GD_P(type) \
 250   ((type) == GOT_TLS_GD || GOT_TLS_GD_BOTH_P (type))
 251 #define GOT_TLS_GDESC_P(type) \
 252   ((type) == GOT_TLS_GDESC || GOT_TLS_GD_BOTH_P (type))
 253 #define GOT_TLS_GD_ANY_P(type) \
 254   (GOT_TLS_GD_P (type) || GOT_TLS_GDESC_P (type))
 255
 256 #define elf_x86_hash_entry(ent) \
 257   ((struct elf_x86_link_hash_entry *)(ent))
 258
 259 /* x86 ELF linker hash table.  */
 260
 261 struct elf_x86_link_hash_table
 262 {
 263   struct elf_link_hash_table elf;
 264
 265   /* Short-cuts to get to dynamic linker sections.  */
 266   asection *interp;
 267   asection *plt_eh_frame;
 268   asection *plt_second;
 269   asection *plt_second_eh_frame;
 270   asection *plt_got;
 271   asection *plt_got_eh_frame;
 272
 273   /* Parameters describing PLT generation, lazy or non-lazy.  */
 274   struct elf_x86_plt_layout plt;
 275
 276   /* Parameters describing lazy PLT generation.  */
 277   const struct elf_x86_lazy_plt_layout *lazy_plt;
 278
 279   /* Parameters describing non-lazy PLT generation.  */
 280   const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
 281
 282   union
 283   {
 284     bfd_signed_vma refcount;
 285     bfd_vma offset;
 286   } tls_ld_or_ldm_got;
 287
 288   /* The amount of space used by the jump slots in the GOT.  */
 289   bfd_vma sgotplt_jump_table_size;
 290
 291   /* Small local sym cache.  */
 292   struct sym_cache sym_cache;
 293
 294   /* _TLS_MODULE_BASE_ symbol.  */
 295   struct bfd_link_hash_entry *tls_module_base;
 296
 297   /* Used by local STT_GNU_IFUNC symbols.  */
 298   htab_t loc_hash_table;
 299   void * loc_hash_memory;
 300
 301   /* The offset into sgot of the GOT entry used by the PLT entry
 302      above.  */
 303   bfd_vma tlsdesc_got;
 304
 305   /* The index of the next R_X86_64_JUMP_SLOT entry in .rela.plt.  */
 306   bfd_vma next_jump_slot_index;
 307   /* The index of the next R_X86_64_IRELATIVE entry in .rela.plt.  */
 308   bfd_vma next_irelative_index;
 309
 310   /* TRUE if there are dynamic relocs against IFUNC symbols that apply
 311      to read-only sections.  */
 312   bfd_boolean readonly_dynrelocs_against_ifunc;
 313
 314   /* TRUE if this is a VxWorks x86 target.  This is only used for
 315      i386.  */
 316   bfd_boolean is_vxworks;
 317
 318   /* The (unloaded but important) .rel.plt.unloaded section on VxWorks.
 319      This is used for i386 only.  */
 320   asection *srelplt2;
 321
 322   /* The index of the next unused R_386_TLS_DESC slot in .rel.plt.  This
 323      is only used for i386.  */
 324   bfd_vma next_tls_desc_index;
 325
 326   /* The offset into splt of the PLT entry for the TLS descriptor
 327      resolver.  Special values are 0, if not necessary (or not found
 328      to be necessary yet), and -1 if needed but not determined
 329      yet.  This is only used for x86-64.  */
 330   bfd_vma tlsdesc_plt;
 331
 332   bfd_vma (*r_info) (bfd_vma, bfd_vma);
 333   bfd_vma (*r_sym) (bfd_vma);
 334   bfd_boolean (*is_reloc_section) (const char *);
 335   enum elf_target_id target_id;
 336   unsigned int sizeof_reloc;
 337   unsigned int dt_reloc;
 338   unsigned int dt_reloc_sz;
 339   unsigned int dt_reloc_ent;
 340   unsigned int got_entry_size;
 341   unsigned int pointer_r_type;
 342   int dynamic_interpreter_size;
 343   const char *dynamic_interpreter;
 344   const char *tls_get_addr;
 345 };
 346
 347 struct elf_x86_init_table
 348 {
 349   /* The lazy PLT layout.  */
 350   const struct elf_x86_lazy_plt_layout *lazy_plt;
 351
 352   /* The non-lazy PLT layout.  */
 353   const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
 354
 355   /* The lazy PLT layout for IBT.  */
 356   const struct elf_x86_lazy_plt_layout *lazy_ibt_plt;
 357
 358   /* The non-lazy PLT layout for IBT.  */
 359   const struct elf_x86_non_lazy_plt_layout *non_lazy_ibt_plt;
 360
 361   /* TRUE if this is a normal x86 target.  */
 362   bfd_boolean normal_target;
 363
 364   /* TRUE if this is a VxWorks x86 target.  */
 365   bfd_boolean is_vxworks;
 366
 367   bfd_vma (*r_info) (bfd_vma, bfd_vma);
 368   bfd_vma (*r_sym) (bfd_vma);
 369 };
 370
 371 struct elf_x86_obj_tdata
 372 {
 373   struct elf_obj_tdata root;
 374
 375   /* tls_type for each local got entry.  */
 376   char *local_got_tls_type;
 377
 378   /* GOTPLT entries for TLS descriptors.  */
 379   bfd_vma *local_tlsdesc_gotent;
 380 };
 381
 382 enum elf_x86_plt_type
 383 {
 384   plt_non_lazy = 0,
 385   plt_lazy = 1 << 0,
 386   plt_pic = 1 << 1,
 387   plt_second = 1 << 2,
 388   plt_unknown = -1
 389 };
 390
 391 struct elf_x86_plt
 392 {
 393   const char *name;
 394   asection *sec;
 395   bfd_byte *contents;
 396   enum elf_x86_plt_type type;
 397   unsigned int plt_got_offset;
 398   unsigned int plt_entry_size;
 399   unsigned int plt_got_insn_size;       /* Only used for x86-64.  */
 400   long count;
 401 };
 402
 403 #define elf_x86_tdata(abfd) \
 404   ((struct elf_x86_obj_tdata *) (abfd)->tdata.any)
 405
 406 #define elf_x86_local_got_tls_type(abfd) \
 407   (elf_x86_tdata (abfd)->local_got_tls_type)
 408
 409 #define elf_x86_local_tlsdesc_gotent(abfd) \
 410   (elf_x86_tdata (abfd)->local_tlsdesc_gotent)
 411
 412 #define elf_x86_compute_jump_table_size(htab) \
 413   ((htab)->elf.srelplt->reloc_count * (htab)->got_entry_size)
 414
 415 #define is_x86_elf(bfd, htab)                           \
 416   (bfd_get_flavour (bfd) == bfd_target_elf_flavour      \
 417    && elf_tdata (bfd) != NULL                           \
 418    && elf_object_id (bfd) == (htab)->target_id)
 419
 420 extern bfd_boolean _bfd_x86_elf_mkobject
 421   (bfd *);
 422
 423 extern void _bfd_x86_elf_set_tls_module_base
 424   (struct bfd_link_info *);
 425
 426 extern bfd_vma _bfd_x86_elf_dtpoff_base
 427   (struct bfd_link_info *);
 428
 429 extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs
 430   (struct elf_link_hash_entry *, void *);
 431
 432 extern struct elf_link_hash_entry * _bfd_elf_x86_get_local_sym_hash
 433   (struct elf_x86_link_hash_table *, bfd *, const Elf_Internal_Rela *,
 434    bfd_boolean);
 435
 436 extern hashval_t _bfd_x86_elf_local_htab_hash
 437   (const void *);
 438
 439 extern int _bfd_x86_elf_local_htab_eq
 440   (const void *, const void *);
 441
 442 extern struct bfd_hash_entry * _bfd_x86_elf_link_hash_newfunc
 443   (struct bfd_hash_entry *, struct bfd_hash_table *, const char *);
 444
 445 extern struct bfd_link_hash_table * _bfd_x86_elf_link_hash_table_create
 446   (bfd *);
 447
 448 extern int _bfd_x86_elf_compare_relocs
 449   (const void *, const void *);
 450
 451 extern bfd_boolean _bfd_x86_elf_link_check_relocs
 452   (bfd *, struct bfd_link_info *);
 453
 454 extern bfd_boolean _bfd_x86_elf_size_dynamic_sections
 455   (bfd *, struct bfd_link_info *);
 456
 457 extern bfd_boolean _bfd_x86_elf_always_size_sections
 458   (bfd *, struct bfd_link_info *);
 459
 460 extern void _bfd_x86_elf_merge_symbol_attribute
 461   (struct elf_link_hash_entry *, const Elf_Internal_Sym *,
 462    bfd_boolean, bfd_boolean);
 463
 464 extern void _bfd_x86_elf_copy_indirect_symbol
 465   (struct bfd_link_info *, struct elf_link_hash_entry *,
 466    struct elf_link_hash_entry *);
 467
 468 extern bfd_boolean _bfd_x86_elf_fixup_symbol
 469   (struct bfd_link_info *, struct elf_link_hash_entry *);
 470
 471 extern bfd_boolean _bfd_x86_elf_hash_symbol
 472   (struct elf_link_hash_entry *);
 473
 474 extern bfd_boolean _bfd_x86_elf_adjust_dynamic_symbol
 475   (struct bfd_link_info *, struct elf_link_hash_entry *);
 476
 477 extern bfd_boolean _bfd_x86_elf_link_symbol_references_local
 478   (struct bfd_link_info *, struct elf_link_hash_entry *);
 479
 480 extern asection * _bfd_x86_elf_gc_mark_hook
 481   (asection *, struct bfd_link_info *, Elf_Internal_Rela *,
 482    struct elf_link_hash_entry *, Elf_Internal_Sym *);
 483
 484 extern long _bfd_x86_elf_get_synthetic_symtab
 485   (bfd *, long, long, bfd_vma, struct elf_x86_plt [], asymbol **,
 486    asymbol **);
 487
 488 extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties
 489   (bfd *, unsigned int, bfd_byte *, unsigned int);
 490
 491 extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
 492   (struct bfd_link_info *, bfd *, elf_property *, elf_property *);
 493
 494 extern bfd * _bfd_x86_elf_link_setup_gnu_properties
 495   (struct bfd_link_info *, struct elf_x86_init_table *);
 496
 497 #define bfd_elf64_mkobject \
 498   _bfd_x86_elf_mkobject
 499 #define bfd_elf32_mkobject \
 500   _bfd_x86_elf_mkobject
 501 #define bfd_elf64_bfd_link_hash_table_create \
 502   _bfd_x86_elf_link_hash_table_create
 503 #define bfd_elf32_bfd_link_hash_table_create \
 504   _bfd_x86_elf_link_hash_table_create
 505 #define bfd_elf64_bfd_link_check_relocs \
 506   _bfd_x86_elf_link_check_relocs
 507 #define bfd_elf32_bfd_link_check_relocs \
 508   _bfd_x86_elf_link_check_relocs
 509
 510 #define elf_backend_size_dynamic_sections \
 511   _bfd_x86_elf_size_dynamic_sections
 512 #define elf_backend_always_size_sections \
 513   _bfd_x86_elf_always_size_sections
 514 #define elf_backend_merge_symbol_attribute \
 515   _bfd_x86_elf_merge_symbol_attribute
 516 #define elf_backend_copy_indirect_symbol \
 517   _bfd_x86_elf_copy_indirect_symbol
 518 #define elf_backend_fixup_symbol \
 519   _bfd_x86_elf_fixup_symbol
 520 #define elf_backend_hash_symbol \
 521   _bfd_x86_elf_hash_symbol
 522 #define elf_backend_adjust_dynamic_symbol \
 523   _bfd_x86_elf_adjust_dynamic_symbol
 524 #define elf_backend_gc_mark_hook \
 525   _bfd_x86_elf_gc_mark_hook
 526 #define elf_backend_omit_section_dynsym \
 527   ((bfd_boolean (*) (bfd *, struct bfd_link_info *, asection *)) bfd_true)
 528 #define elf_backend_parse_gnu_properties \
 529   _bfd_x86_elf_parse_gnu_properties
 530 #define elf_backend_merge_gnu_properties \
 531   _bfd_x86_elf_merge_gnu_properties