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, 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 \
  64                || !(GOT_RELOC)                                   \
  65                || (EH)->has_non_got_reloc                        \
  66                || !(INFO)->dynamic_undefined_weak))))
  67
  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)
  78
  79 /* x86 ELF linker hash entry.  */
  80
  81 struct elf_x86_link_hash_entry
  82 {
  83   struct elf_link_hash_entry elf;
  84
  85   /* Track dynamic relocs copied for this symbol.  */
  86   struct elf_dyn_relocs *dyn_relocs;
  87
  88   unsigned char tls_type;
  89
  90   /* TRUE if symbol has GOT or PLT relocations.  */
  91   unsigned int has_got_reloc : 1;
  92
  93   /* TRUE if symbol has non-GOT/non-PLT relocations in text sections.  */
  94   unsigned int has_non_got_reloc : 1;
  95
  96   /* Don't call finish_dynamic_symbol on this symbol.  */
  97   unsigned int no_finish_dynamic_symbol : 1;
  98
  99   /* TRUE if symbol is __tls_get_addr.  */
 100   unsigned int tls_get_addr : 1;
 101
 102   /* TRUE if symbol is defined as a protected symbol.  */
 103   unsigned int def_protected : 1;
 104
 105   /* 0: Symbol references are unknown.
 106      1: Symbol references aren't local.
 107      2: Symbol references are local.
 108    */
 109   unsigned int local_ref : 2;
 110
 111   /* TRUE if symbol is defined by linker.  */
 112   unsigned int linker_def : 1;
 113
 114   /* Terue if symbol is referenced by R_386_GOTOFF relocation.  This is
 115      only used by i386.  */
 116   unsigned int gotoff_ref : 1;
 117
 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;
 125
 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;
 129
 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;
 133
 134   /* Information about the second PLT entry.   */
 135   union gotplt_union plt_second;
 136
 137   /* Offset of the GOTPLT entry reserved for the TLS descriptor,
 138      starting at the end of the jump table.  */
 139   bfd_vma tlsdesc_got;
 140 };
 141
 142 struct elf_x86_lazy_plt_layout
 143 {
 144   /* The first entry in an absolute lazy procedure linkage table looks
 145      like this.  */
 146   const bfd_byte *plt0_entry;
 147   unsigned int plt0_entry_size;          /* Size of PLT0 entry.  */
 148
 149   /* Later entries in an absolute lazy procedure linkage table look
 150      like this.  */
 151   const bfd_byte *plt_entry;
 152   unsigned int plt_entry_size;          /* Size of each PLT entry.  */
 153
 154   /* Offsets into plt0_entry that are to be replaced with GOT[1] and
 155      GOT[2].  */
 156   unsigned int plt0_got1_offset;
 157   unsigned int plt0_got2_offset;
 158
 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;
 162
 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. */
 167
 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;
 171
 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;
 175
 176   /* Offset into plt_entry where the initial value of the GOT entry
 177      points.  */
 178   unsigned int plt_lazy_offset;
 179
 180   /* The first entry in a PIC lazy procedure linkage table looks like
 181      this.  */
 182   const bfd_byte *pic_plt0_entry;
 183
 184   /* Subsequent entries in a PIC lazy procedure linkage table look
 185      like this.  */
 186   const bfd_byte *pic_plt_entry;
 187
 188   /* .eh_frame covering the lazy .plt section.  */
 189   const bfd_byte *eh_frame_plt;
 190   unsigned int eh_frame_plt_size;
 191 };
 192
 193 struct elf_x86_non_lazy_plt_layout
 194 {
 195   /* Entries in an absolute non-lazy procedure linkage table look like
 196      this.  */
 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;
 200
 201   unsigned int plt_entry_size;          /* Size of each PLT entry.  */
 202
 203   /* Offsets into plt_entry that are to be replaced with...  */
 204   unsigned int plt_got_offset;    /* ... address of this symbol in .got. */
 205
 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;
 209
 210   /* .eh_frame covering the non-lazy .plt section.  */
 211   const bfd_byte *eh_frame_plt;
 212   unsigned int eh_frame_plt_size;
 213 };
 214
 215 struct elf_x86_plt_layout
 216 {
 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
 219      different.  */
 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.  */
 224
 225   /* 1 has PLT0.  */
 226   unsigned int has_plt0;
 227
 228   /* Offsets into plt_entry that are to be replaced with...  */
 229   unsigned int plt_got_offset;    /* ... address of this symbol in .got. */
 230
 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;
 234
 235   /* .eh_frame covering the .plt section.  */
 236   const bfd_byte *eh_frame_plt;
 237   unsigned int eh_frame_plt_size;
 238 };
 239
 240 /* Values in tls_type of x86 ELF linker hash entry.  */
 241 #define GOT_UNKNOWN     0
 242 #define GOT_NORMAL      1
 243 #define GOT_TLS_GD      2
 244 #define GOT_TLS_IE      4
 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))
 257
 258 #define elf_x86_hash_entry(ent) \
 259   ((struct elf_x86_link_hash_entry *)(ent))
 260
 261 /* x86 ELF linker hash table.  */
 262
 263 struct elf_x86_link_hash_table
 264 {
 265   struct elf_link_hash_table elf;
 266
 267   /* Short-cuts to get to dynamic linker sections.  */
 268   asection *interp;
 269   asection *plt_eh_frame;
 270   asection *plt_second;
 271   asection *plt_second_eh_frame;
 272   asection *plt_got;
 273   asection *plt_got_eh_frame;
 274
 275   /* Parameters describing PLT generation, lazy or non-lazy.  */
 276   struct elf_x86_plt_layout plt;
 277
 278   /* Parameters describing lazy PLT generation.  */
 279   const struct elf_x86_lazy_plt_layout *lazy_plt;
 280
 281   /* Parameters describing non-lazy PLT generation.  */
 282   const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
 283
 284   union
 285   {
 286     bfd_signed_vma refcount;
 287     bfd_vma offset;
 288   } tls_ld_or_ldm_got;
 289
 290   /* The amount of space used by the jump slots in the GOT.  */
 291   bfd_vma sgotplt_jump_table_size;
 292
 293   /* Small local sym cache.  */
 294   struct sym_cache sym_cache;
 295
 296   /* _TLS_MODULE_BASE_ symbol.  */
 297   struct bfd_link_hash_entry *tls_module_base;
 298
 299   /* Used by local STT_GNU_IFUNC symbols.  */
 300   htab_t loc_hash_table;
 301   void * loc_hash_memory;
 302
 303   /* The offset into sgot of the GOT entry used by the PLT entry
 304      above.  */
 305   bfd_vma tlsdesc_got;
 306
 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;
 311
 312   /* TRUE if there are dynamic relocs against IFUNC symbols that apply
 313      to read-only sections.  */
 314   bfd_boolean readonly_dynrelocs_against_ifunc;
 315
 316   /* TRUE if this is a VxWorks x86 target.  This is only used for
 317      i386.  */
 318   bfd_boolean is_vxworks;
 319
 320   /* The (unloaded but important) .rel.plt.unloaded section on VxWorks.
 321      This is used for i386 only.  */
 322   asection *srelplt2;
 323
 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;
 327
 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.  */
 332   bfd_vma tlsdesc_plt;
 333
 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;
 347 };
 348
 349 struct elf_x86_init_table
 350 {
 351   /* The lazy PLT layout.  */
 352   const struct elf_x86_lazy_plt_layout *lazy_plt;
 353
 354   /* The non-lazy PLT layout.  */
 355   const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
 356
 357   /* The lazy PLT layout for IBT.  */
 358   const struct elf_x86_lazy_plt_layout *lazy_ibt_plt;
 359
 360   /* The non-lazy PLT layout for IBT.  */
 361   const struct elf_x86_non_lazy_plt_layout *non_lazy_ibt_plt;
 362
 363   /* TRUE if this is a normal x86 target.  */
 364   bfd_boolean normal_target;
 365
 366   /* TRUE if this is a VxWorks x86 target.  */
 367   bfd_boolean is_vxworks;
 368
 369   bfd_vma (*r_info) (bfd_vma, bfd_vma);
 370   bfd_vma (*r_sym) (bfd_vma);
 371 };
 372
 373 struct elf_x86_obj_tdata
 374 {
 375   struct elf_obj_tdata root;
 376
 377   /* tls_type for each local got entry.  */
 378   char *local_got_tls_type;
 379
 380   /* GOTPLT entries for TLS descriptors.  */
 381   bfd_vma *local_tlsdesc_gotent;
 382 };
 383
 384 enum elf_x86_plt_type
 385 {
 386   plt_non_lazy = 0,
 387   plt_lazy = 1 << 0,
 388   plt_pic = 1 << 1,
 389   plt_second = 1 << 2,
 390   plt_unknown = -1
 391 };
 392
 393 struct elf_x86_plt
 394 {
 395   const char *name;
 396   asection *sec;
 397   bfd_byte *contents;
 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.  */
 402   long count;
 403 };
 404
 405 #define elf_x86_tdata(abfd) \
 406   ((struct elf_x86_obj_tdata *) (abfd)->tdata.any)
 407
 408 #define elf_x86_local_got_tls_type(abfd) \
 409   (elf_x86_tdata (abfd)->local_got_tls_type)
 410
 411 #define elf_x86_local_tlsdesc_gotent(abfd) \
 412   (elf_x86_tdata (abfd)->local_tlsdesc_gotent)
 413
 414 #define elf_x86_compute_jump_table_size(htab) \
 415   ((htab)->elf.srelplt->reloc_count * (htab)->got_entry_size)
 416
 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)
 421
 422 extern bfd_boolean _bfd_x86_elf_mkobject
 423   (bfd *);
 424
 425 extern void _bfd_x86_elf_set_tls_module_base
 426   (struct bfd_link_info *);
 427
 428 extern bfd_vma _bfd_x86_elf_dtpoff_base
 429   (struct bfd_link_info *);
 430
 431 extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs
 432   (struct elf_link_hash_entry *, void *);
 433
 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 *,
 436    bfd_boolean);
 437
 438 extern hashval_t _bfd_x86_elf_local_htab_hash
 439   (const void *);
 440
 441 extern int _bfd_x86_elf_local_htab_eq
 442   (const void *, const void *);
 443
 444 extern struct bfd_hash_entry * _bfd_x86_elf_link_hash_newfunc
 445   (struct bfd_hash_entry *, struct bfd_hash_table *, const char *);
 446
 447 extern struct bfd_link_hash_table * _bfd_x86_elf_link_hash_table_create
 448   (bfd *);
 449
 450 extern int _bfd_x86_elf_compare_relocs
 451   (const void *, const void *);
 452
 453 extern bfd_boolean _bfd_x86_elf_link_check_relocs
 454   (bfd *, struct bfd_link_info *);
 455
 456 extern bfd_boolean _bfd_x86_elf_size_dynamic_sections
 457   (bfd *, struct bfd_link_info *);
 458
 459 extern bfd_boolean _bfd_x86_elf_always_size_sections
 460   (bfd *, struct bfd_link_info *);
 461
 462 extern void _bfd_x86_elf_merge_symbol_attribute
 463   (struct elf_link_hash_entry *, const Elf_Internal_Sym *,
 464    bfd_boolean, bfd_boolean);
 465
 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 *);
 469
 470 extern bfd_boolean _bfd_x86_elf_fixup_symbol
 471   (struct bfd_link_info *, struct elf_link_hash_entry *);
 472
 473 extern bfd_boolean _bfd_x86_elf_hash_symbol
 474   (struct elf_link_hash_entry *);
 475
 476 extern bfd_boolean _bfd_x86_elf_adjust_dynamic_symbol
 477   (struct bfd_link_info *, struct elf_link_hash_entry *);
 478
 479 extern bfd_boolean _bfd_x86_elf_link_symbol_references_local
 480   (struct bfd_link_info *, struct elf_link_hash_entry *);
 481
 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 *);
 485
 486 extern long _bfd_x86_elf_get_synthetic_symtab
 487   (bfd *, long, long, bfd_vma, struct elf_x86_plt [], asymbol **,
 488    asymbol **);
 489
 490 extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties
 491   (bfd *, unsigned int, bfd_byte *, unsigned int);
 492
 493 extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
 494   (struct bfd_link_info *, bfd *, elf_property *, elf_property *);
 495
 496 extern bfd * _bfd_x86_elf_link_setup_gnu_properties
 497   (struct bfd_link_info *, struct elf_x86_init_table *);
 498
 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
 511
 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