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 ABI_64_P(abfd) \
  30   (get_elf_backend_data (abfd)->s->elfclass == ELFCLASS64)
  31
  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
  35    shared lib.  */
  36 #define ELIMINATE_COPY_RELOCS 1
  37
  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)
  41
  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
  44    it isn't dynamic and
  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.
  48  */
  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 \
  54                || !(GOT_RELOC)                                   \
  55                || (EH)->has_non_got_reloc                        \
  56                || !(INFO)->dynamic_undefined_weak))))
  57
  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)
  68
  69 /* x86 ELF linker hash entry.  */
  70
  71 struct elf_x86_link_hash_entry
  72 {
  73   struct elf_link_hash_entry elf;
  74
  75   /* Track dynamic relocs copied for this symbol.  */
  76   struct elf_dyn_relocs *dyn_relocs;
  77
  78   unsigned char tls_type;
  79
  80   /* TRUE if symbol has GOT or PLT relocations.  */
  81   unsigned int has_got_reloc : 1;
  82
  83   /* TRUE if symbol has non-GOT/non-PLT relocations in text sections.  */
  84   unsigned int has_non_got_reloc : 1;
  85
  86   /* Don't call finish_dynamic_symbol on this symbol.  */
  87   unsigned int no_finish_dynamic_symbol : 1;
  88
  89   /* TRUE if symbol is __tls_get_addr.  */
  90   unsigned int tls_get_addr : 1;
  91
  92   /* TRUE if symbol is defined as a protected symbol.  */
  93   unsigned int def_protected : 1;
  94
  95   /* Symbol is referenced by R_386_GOTOFF relocation.  This is only used
  96      by i386.  */
  97   unsigned int gotoff_ref : 1;
  98
  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;
 106
 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;
 110
 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;
 114
 115   /* Information about the second PLT entry.   */
 116   union gotplt_union plt_second;
 117
 118   /* Offset of the GOTPLT entry reserved for the TLS descriptor,
 119      starting at the end of the jump table.  */
 120   bfd_vma tlsdesc_got;
 121 };
 122
 123 struct elf_x86_lazy_plt_layout
 124 {
 125   /* The first entry in an absolute lazy procedure linkage table looks
 126      like this.  */
 127   const bfd_byte *plt0_entry;
 128   unsigned int plt0_entry_size;          /* Size of PLT0 entry.  */
 129
 130   /* Later entries in an absolute lazy procedure linkage table look
 131      like this.  */
 132   const bfd_byte *plt_entry;
 133   unsigned int plt_entry_size;          /* Size of each PLT entry.  */
 134
 135   /* Offsets into plt0_entry that are to be replaced with GOT[1] and
 136      GOT[2].  */
 137   unsigned int plt0_got1_offset;
 138   unsigned int plt0_got2_offset;
 139
 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;
 143
 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. */
 148
 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;
 152
 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;
 156
 157   /* Offset into plt_entry where the initial value of the GOT entry
 158      points.  */
 159   unsigned int plt_lazy_offset;
 160
 161   /* The first entry in a PIC lazy procedure linkage table looks like
 162      this.  */
 163   const bfd_byte *pic_plt0_entry;
 164
 165   /* Subsequent entries in a PIC lazy procedure linkage table look
 166      like this.  */
 167   const bfd_byte *pic_plt_entry;
 168
 169   /* .eh_frame covering the lazy .plt section.  */
 170   const bfd_byte *eh_frame_plt;
 171   unsigned int eh_frame_plt_size;
 172 };
 173
 174 struct elf_x86_non_lazy_plt_layout
 175 {
 176   /* Entries in an absolute non-lazy procedure linkage table look like
 177      this.  */
 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;
 181
 182   unsigned int plt_entry_size;          /* Size of each PLT entry.  */
 183
 184   /* Offsets into plt_entry that are to be replaced with...  */
 185   unsigned int plt_got_offset;    /* ... address of this symbol in .got. */
 186
 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;
 190
 191   /* .eh_frame covering the non-lazy .plt section.  */
 192   const bfd_byte *eh_frame_plt;
 193   unsigned int eh_frame_plt_size;
 194 };
 195
 196 struct elf_x86_plt_layout
 197 {
 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
 200      different.  */
 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.  */
 205
 206   /* 1 has PLT0.  */
 207   unsigned int has_plt0;
 208
 209   /* Offsets into plt_entry that are to be replaced with...  */
 210   unsigned int plt_got_offset;    /* ... address of this symbol in .got. */
 211
 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;
 215
 216   /* .eh_frame covering the .plt section.  */
 217   const bfd_byte *eh_frame_plt;
 218   unsigned int eh_frame_plt_size;
 219 };
 220
 221 /* Values in tls_type of x86 ELF linker hash entry.  */
 222 #define GOT_UNKNOWN     0
 223 #define GOT_NORMAL      1
 224 #define GOT_TLS_GD      2
 225 #define GOT_TLS_IE      4
 226 #define GOT_TLS_IE_POS  5
 227 #define GOT_TLS_IE_NEG  6
 228 #define GOT_TLS_IE_BOTH 7
 229 #define GOT_TLS_GDESC   8
 230 #define GOT_TLS_GD_BOTH_P(type) \
 231   ((type) == (GOT_TLS_GD | GOT_TLS_GDESC))
 232 #define GOT_TLS_GD_P(type) \
 233   ((type) == GOT_TLS_GD || GOT_TLS_GD_BOTH_P (type))
 234 #define GOT_TLS_GDESC_P(type) \
 235   ((type) == GOT_TLS_GDESC || GOT_TLS_GD_BOTH_P (type))
 236 #define GOT_TLS_GD_ANY_P(type) \
 237   (GOT_TLS_GD_P (type) || GOT_TLS_GDESC_P (type))
 238
 239 #define elf_x86_hash_entry(ent) \
 240   ((struct elf_x86_link_hash_entry *)(ent))
 241
 242 /* x86 ELF linker hash table.  */
 243
 244 struct elf_x86_link_hash_table
 245 {
 246   struct elf_link_hash_table elf;
 247
 248   /* Short-cuts to get to dynamic linker sections.  */
 249   asection *interp;
 250   asection *plt_eh_frame;
 251   asection *plt_second;
 252   asection *plt_second_eh_frame;
 253   asection *plt_got;
 254   asection *plt_got_eh_frame;
 255
 256   /* Parameters describing PLT generation, lazy or non-lazy.  */
 257   struct elf_x86_plt_layout plt;
 258
 259   /* Parameters describing lazy PLT generation.  */
 260   const struct elf_x86_lazy_plt_layout *lazy_plt;
 261
 262   /* Parameters describing non-lazy PLT generation.  */
 263   const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
 264
 265   union
 266   {
 267     bfd_signed_vma refcount;
 268     bfd_vma offset;
 269   } tls_ld_or_ldm_got;
 270
 271   /* The amount of space used by the jump slots in the GOT.  */
 272   bfd_vma sgotplt_jump_table_size;
 273
 274   /* Small local sym cache.  */
 275   struct sym_cache sym_cache;
 276
 277   /* _TLS_MODULE_BASE_ symbol.  */
 278   struct bfd_link_hash_entry *tls_module_base;
 279
 280   /* Used by local STT_GNU_IFUNC symbols.  */
 281   htab_t loc_hash_table;
 282   void * loc_hash_memory;
 283
 284   /* The offset into splt of the PLT entry for the TLS descriptor
 285      resolver.  Special values are 0, if not necessary (or not found
 286      to be necessary yet), and -1 if needed but not determined
 287      yet.  */
 288   bfd_vma tlsdesc_plt;
 289
 290   /* The offset into sgot of the GOT entry used by the PLT entry
 291      above.  */
 292   bfd_vma tlsdesc_got;
 293
 294   /* The index of the next R_X86_64_JUMP_SLOT entry in .rela.plt.  */
 295   bfd_vma next_jump_slot_index;
 296   /* The index of the next R_X86_64_IRELATIVE entry in .rela.plt.  */
 297   bfd_vma next_irelative_index;
 298
 299   /* TRUE if there are dynamic relocs against IFUNC symbols that apply
 300      to read-only sections.  */
 301   bfd_boolean readonly_dynrelocs_against_ifunc;
 302
 303   /* TRUE if this is a VxWorks x86 target.  */
 304   bfd_boolean is_vxworks;
 305
 306   /* The (unloaded but important) .rel.plt.unloaded section on VxWorks.
 307      This is used for i386 only.  */
 308   asection *srelplt2;
 309
 310   /* The index of the next unused R_386_TLS_DESC slot in .rel.plt.  This
 311      is used for i386 only.  */
 312   bfd_vma next_tls_desc_index;
 313
 314   bfd_vma (*r_info) (bfd_vma, bfd_vma);
 315   bfd_vma (*r_sym) (bfd_vma);
 316   unsigned int sizeof_reloc;
 317   unsigned int pointer_r_type;
 318   int dynamic_interpreter_size;
 319   const char *dynamic_interpreter;
 320   const char *tls_get_addr;
 321 };
 322
 323 struct elf_x86_plt_layout_table
 324 {
 325   /* The lazy PLT layout.  */
 326   const struct elf_x86_lazy_plt_layout *lazy_plt;
 327
 328   /* The non-lazy PLT layout.  */
 329   const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
 330
 331   /* The lazy PLT layout for IBT.  */
 332   const struct elf_x86_lazy_plt_layout *lazy_ibt_plt;
 333
 334   /* The non-lazy PLT layout for IBT.  */
 335   const struct elf_x86_non_lazy_plt_layout *non_lazy_ibt_plt;
 336
 337   /* TRUE if this is a normal x86 target.  */
 338   bfd_boolean normal_target;
 339
 340   /* TRUE if this is a VxWorks x86 target.  */
 341   bfd_boolean is_vxworks;
 342 };
 343
 344 struct elf_x86_obj_tdata
 345 {
 346   struct elf_obj_tdata root;
 347
 348   /* tls_type for each local got entry.  */
 349   char *local_got_tls_type;
 350
 351   /* GOTPLT entries for TLS descriptors.  */
 352   bfd_vma *local_tlsdesc_gotent;
 353 };
 354
 355 enum elf_x86_plt_type
 356 {
 357   plt_non_lazy = 0,
 358   plt_lazy = 1 << 0,
 359   plt_pic = 1 << 1,
 360   plt_second = 1 << 2,
 361   plt_unknown = -1
 362 };
 363
 364 struct elf_x86_plt
 365 {
 366   const char *name;
 367   asection *sec;
 368   bfd_byte *contents;
 369   enum elf_x86_plt_type type;
 370   unsigned int plt_got_offset;
 371   unsigned int plt_entry_size;
 372   unsigned int plt_got_insn_size;       /* Only used for x86-64.  */
 373   long count;
 374 };
 375
 376 #define elf_x86_tdata(abfd) \
 377   ((struct elf_x86_obj_tdata *) (abfd)->tdata.any)
 378
 379 #define elf_x86_local_got_tls_type(abfd) \
 380   (elf_x86_tdata (abfd)->local_got_tls_type)
 381
 382 #define elf_x86_local_tlsdesc_gotent(abfd) \
 383   (elf_x86_tdata (abfd)->local_tlsdesc_gotent)
 384
 385 extern bfd_boolean _bfd_x86_elf_mkobject
 386   (bfd *);
 387
 388 extern void _bfd_x86_elf_set_tls_module_base
 389   (struct bfd_link_info *);
 390
 391 extern bfd_vma _bfd_x86_elf_dtpoff_base
 392   (struct bfd_link_info *);
 393
 394 extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs
 395   (struct elf_link_hash_entry *, void *);
 396
 397 extern struct elf_link_hash_entry * _bfd_elf_x86_get_local_sym_hash
 398   (struct elf_x86_link_hash_table *, bfd *, const Elf_Internal_Rela *,
 399    bfd_boolean);
 400
 401 extern hashval_t _bfd_x86_elf_local_htab_hash
 402   (const void *);
 403
 404 extern int _bfd_x86_elf_local_htab_eq
 405   (const void *, const void *);
 406
 407 extern struct bfd_hash_entry * _bfd_x86_elf_link_hash_newfunc
 408   (struct bfd_hash_entry *, struct bfd_hash_table *, const char *);
 409
 410 extern struct bfd_link_hash_table * _bfd_x86_elf_link_hash_table_create
 411   (bfd *);
 412
 413 extern int _bfd_x86_elf_compare_relocs
 414   (const void *, const void *);
 415
 416 extern bfd_boolean _bfd_x86_elf_link_check_relocs
 417   (bfd *, struct bfd_link_info *);
 418
 419 extern bfd_boolean _bfd_x86_elf_always_size_sections
 420   (bfd *, struct bfd_link_info *);
 421
 422 extern void _bfd_x86_elf_merge_symbol_attribute
 423   (struct elf_link_hash_entry *, const Elf_Internal_Sym *,
 424    bfd_boolean, bfd_boolean);
 425
 426 extern void _bfd_x86_elf_copy_indirect_symbol
 427   (struct bfd_link_info *, struct elf_link_hash_entry *,
 428    struct elf_link_hash_entry *);
 429
 430 extern bfd_boolean _bfd_x86_elf_fixup_symbol
 431   (struct bfd_link_info *, struct elf_link_hash_entry *);
 432
 433 extern bfd_boolean _bfd_x86_elf_hash_symbol
 434   (struct elf_link_hash_entry *);
 435
 436 extern bfd_boolean _bfd_x86_elf_adjust_dynamic_symbol
 437   (struct bfd_link_info *, struct elf_link_hash_entry *);
 438
 439 extern asection * _bfd_x86_elf_gc_mark_hook
 440   (asection *, struct bfd_link_info *, Elf_Internal_Rela *,
 441    struct elf_link_hash_entry *, Elf_Internal_Sym *);
 442
 443 extern long _bfd_x86_elf_get_synthetic_symtab
 444   (bfd *, long, long, bfd_vma, struct elf_x86_plt [], asymbol **,
 445    asymbol **);
 446
 447 extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties
 448   (bfd *, unsigned int, bfd_byte *, unsigned int);
 449
 450 extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
 451   (struct bfd_link_info *, bfd *, elf_property *, elf_property *);
 452
 453 extern bfd * _bfd_x86_elf_link_setup_gnu_properties
 454   (struct bfd_link_info *, struct elf_x86_plt_layout_table *);
 455
 456 #define bfd_elf64_mkobject \
 457   _bfd_x86_elf_mkobject
 458 #define bfd_elf32_mkobject \
 459   _bfd_x86_elf_mkobject
 460 #define bfd_elf64_bfd_link_hash_table_create \
 461   _bfd_x86_elf_link_hash_table_create
 462 #define bfd_elf32_bfd_link_hash_table_create \
 463   _bfd_x86_elf_link_hash_table_create
 464 #define bfd_elf64_bfd_link_check_relocs \
 465   _bfd_x86_elf_link_check_relocs
 466 #define bfd_elf32_bfd_link_check_relocs \
 467   _bfd_x86_elf_link_check_relocs
 468
 469 #define elf_backend_always_size_sections \
 470   _bfd_x86_elf_always_size_sections
 471 #define elf_backend_merge_symbol_attribute \
 472   _bfd_x86_elf_merge_symbol_attribute
 473 #define elf_backend_copy_indirect_symbol \
 474   _bfd_x86_elf_copy_indirect_symbol
 475 #define elf_backend_fixup_symbol \
 476   _bfd_x86_elf_fixup_symbol
 477 #define elf_backend_hash_symbol \
 478   _bfd_x86_elf_hash_symbol
 479 #define elf_backend_adjust_dynamic_symbol \
 480   _bfd_x86_elf_adjust_dynamic_symbol
 481 #define elf_backend_gc_mark_hook \
 482   _bfd_x86_elf_gc_mark_hook
 483 #define elf_backend_omit_section_dynsym \
 484   ((bfd_boolean (*) (bfd *, struct bfd_link_info *, asection *)) bfd_true)
 485 #define elf_backend_parse_gnu_properties \
 486   _bfd_x86_elf_parse_gnu_properties
 487 #define elf_backend_merge_gnu_properties \
 488   _bfd_x86_elf_merge_gnu_properties