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   (elf_hash_table_id ((struct elf_link_hash_table *) ((p)->hash)) == (id) \
  45     ? ((struct elf_x86_link_hash_table *) ((p)->hash)) : NULL)
  46
  47 /* Is a undefined weak symbol which is resolved to 0.  Reference to an
  48    undefined weak symbol is resolved to 0 when building executable if
  49    it isn't dynamic and
  50    1. Has non-GOT/non-PLT relocations in text section.  Or
  51    2. Has no GOT/PLT relocation.
  52    Local undefined weak symbol is always resolved to 0.
  53  */
  54 #define UNDEFINED_WEAK_RESOLVED_TO_ZERO(INFO, ID, GOT_RELOC, EH) \
  55   ((EH)->elf.root.type == bfd_link_hash_undefweak                \
  56    && ((EH)->elf.forced_local                                    \
  57        || (bfd_link_executable (INFO)                            \
  58            && (elf_x86_hash_table ((INFO), (ID))->interp == NULL \
  59                || !(GOT_RELOC)                                   \
  60                || (EH)->has_non_got_reloc                        \
  61                || !(INFO)->dynamic_undefined_weak))))
  62
  63 /* Should copy relocation be generated for a symbol.  Don't generate
  64    copy relocation against a protected symbol defined in a shared
  65    object with GNU_PROPERTY_NO_COPY_ON_PROTECTED.  */
  66 #define SYMBOL_NO_COPYRELOC(INFO, EH) \
  67   ((EH)->def_protected \
  68    && ((EH)->elf.root.type == bfd_link_hash_defined \
  69        || (EH)->elf.root.type == bfd_link_hash_defweak) \
  70    && elf_has_no_copy_on_protected ((EH)->elf.root.u.def.section->owner) \
  71    && ((EH)->elf.root.u.def.section->owner->flags & DYNAMIC) != 0 \
  72    && ((EH)->elf.root.u.def.section->flags & SEC_CODE) == 0)
  73
  74 /* x86 ELF linker hash entry.  */
  75
  76 struct elf_x86_link_hash_entry
  77 {
  78   struct elf_link_hash_entry elf;
  79
  80   /* Track dynamic relocs copied for this symbol.  */
  81   struct elf_dyn_relocs *dyn_relocs;
  82
  83   unsigned char tls_type;
  84
  85   /* TRUE if symbol has GOT or PLT relocations.  */
  86   unsigned int has_got_reloc : 1;
  87
  88   /* TRUE if symbol has non-GOT/non-PLT relocations in text sections.  */
  89   unsigned int has_non_got_reloc : 1;
  90
  91   /* Don't call finish_dynamic_symbol on this symbol.  */
  92   unsigned int no_finish_dynamic_symbol : 1;
  93
  94   /* TRUE if symbol is __tls_get_addr.  */
  95   unsigned int tls_get_addr : 1;
  96
  97   /* TRUE if symbol is defined as a protected symbol.  */
  98   unsigned int def_protected : 1;
  99
 100   /* Symbol is referenced by R_386_GOTOFF relocation.  This is only used
 101      by i386.  */
 102   unsigned int gotoff_ref : 1;
 103
 104   /* TRUE if a weak symbol with a real definition needs a copy reloc.
 105      When there is a weak symbol with a real definition, the processor
 106      independent code will have arranged for us to see the real
 107      definition first.  We need to copy the needs_copy bit from the
 108      real definition and check it when allowing copy reloc in PIE.  This
 109      is only used by x86-64.  */
 110   unsigned int needs_copy : 1;
 111
 112   /* Reference count of C/C++ function pointer relocations in read-write
 113      section which can be resolved at run-time.  */
 114   bfd_signed_vma func_pointer_refcount;
 115
 116   /* Information about the GOT PLT entry. Filled when there are both
 117      GOT and PLT relocations against the same function.  */
 118   union gotplt_union plt_got;
 119
 120   /* Information about the second PLT entry.   */
 121   union gotplt_union plt_second;
 122
 123   /* Offset of the GOTPLT entry reserved for the TLS descriptor,
 124      starting at the end of the jump table.  */
 125   bfd_vma tlsdesc_got;
 126 };
 127
 128 struct elf_x86_lazy_plt_layout
 129 {
 130   /* The first entry in an absolute lazy procedure linkage table looks
 131      like this.  */
 132   const bfd_byte *plt0_entry;
 133   unsigned int plt0_entry_size;          /* Size of PLT0 entry.  */
 134
 135   /* Later entries in an absolute lazy procedure linkage table look
 136      like this.  */
 137   const bfd_byte *plt_entry;
 138   unsigned int plt_entry_size;          /* Size of each PLT entry.  */
 139
 140   /* Offsets into plt0_entry that are to be replaced with GOT[1] and
 141      GOT[2].  */
 142   unsigned int plt0_got1_offset;
 143   unsigned int plt0_got2_offset;
 144
 145   /* Offset of the end of the PC-relative instruction containing
 146      plt0_got2_offset.  This is for x86-64 only.  */
 147   unsigned int plt0_got2_insn_end;
 148
 149   /* Offsets into plt_entry that are to be replaced with...  */
 150   unsigned int plt_got_offset;    /* ... address of this symbol in .got. */
 151   unsigned int plt_reloc_offset;  /* ... offset into relocation table. */
 152   unsigned int plt_plt_offset;    /* ... offset to start of .plt. */
 153
 154   /* Length of the PC-relative instruction containing plt_got_offset.
 155      This is used for x86-64 only.  */
 156   unsigned int plt_got_insn_size;
 157
 158   /* Offset of the end of the PC-relative jump to plt0_entry.  This is
 159      used for x86-64 only.  */
 160   unsigned int plt_plt_insn_end;
 161
 162   /* Offset into plt_entry where the initial value of the GOT entry
 163      points.  */
 164   unsigned int plt_lazy_offset;
 165
 166   /* The first entry in a PIC lazy procedure linkage table looks like
 167      this.  */
 168   const bfd_byte *pic_plt0_entry;
 169
 170   /* Subsequent entries in a PIC lazy procedure linkage table look
 171      like this.  */
 172   const bfd_byte *pic_plt_entry;
 173
 174   /* .eh_frame covering the lazy .plt section.  */
 175   const bfd_byte *eh_frame_plt;
 176   unsigned int eh_frame_plt_size;
 177 };
 178
 179 struct elf_x86_non_lazy_plt_layout
 180 {
 181   /* Entries in an absolute non-lazy procedure linkage table look like
 182      this.  */
 183   const bfd_byte *plt_entry;
 184   /* Entries in a PIC non-lazy procedure linkage table look like this.  */
 185   const bfd_byte *pic_plt_entry;
 186
 187   unsigned int plt_entry_size;          /* Size of each PLT entry.  */
 188
 189   /* Offsets into plt_entry that are to be replaced with...  */
 190   unsigned int plt_got_offset;    /* ... address of this symbol in .got. */
 191
 192   /* Length of the PC-relative instruction containing plt_got_offset.
 193      This is used for x86-64 only.  */
 194   unsigned int plt_got_insn_size;
 195
 196   /* .eh_frame covering the non-lazy .plt section.  */
 197   const bfd_byte *eh_frame_plt;
 198   unsigned int eh_frame_plt_size;
 199 };
 200
 201 struct elf_x86_plt_layout
 202 {
 203   /* The first entry in a lazy procedure linkage table looks like this.
 204      This is only used for i386 where absolute PLT0 and PIC PLT0 are
 205      different.  */
 206   const bfd_byte *plt0_entry;
 207   /* Entries in a procedure linkage table look like this.  */
 208   const bfd_byte *plt_entry;
 209   unsigned int plt_entry_size;          /* Size of each PLT entry.  */
 210
 211   /* 1 has PLT0.  */
 212   unsigned int has_plt0;
 213
 214   /* Offsets into plt_entry that are to be replaced with...  */
 215   unsigned int plt_got_offset;    /* ... address of this symbol in .got. */
 216
 217   /* Length of the PC-relative instruction containing plt_got_offset.
 218      This is only used for x86-64.  */
 219   unsigned int plt_got_insn_size;
 220
 221   /* .eh_frame covering the .plt section.  */
 222   const bfd_byte *eh_frame_plt;
 223   unsigned int eh_frame_plt_size;
 224 };
 225
 226 /* Values in tls_type of x86 ELF linker hash entry.  */
 227 #define GOT_UNKNOWN     0
 228 #define GOT_NORMAL      1
 229 #define GOT_TLS_GD      2
 230 #define GOT_TLS_IE      4
 231 #define GOT_TLS_IE_POS  5
 232 #define GOT_TLS_IE_NEG  6
 233 #define GOT_TLS_IE_BOTH 7
 234 #define GOT_TLS_GDESC   8
 235 #define GOT_TLS_GD_BOTH_P(type) \
 236   ((type) == (GOT_TLS_GD | GOT_TLS_GDESC))
 237 #define GOT_TLS_GD_P(type) \
 238   ((type) == GOT_TLS_GD || GOT_TLS_GD_BOTH_P (type))
 239 #define GOT_TLS_GDESC_P(type) \
 240   ((type) == GOT_TLS_GDESC || GOT_TLS_GD_BOTH_P (type))
 241 #define GOT_TLS_GD_ANY_P(type) \
 242   (GOT_TLS_GD_P (type) || GOT_TLS_GDESC_P (type))
 243
 244 #define elf_x86_hash_entry(ent) \
 245   ((struct elf_x86_link_hash_entry *)(ent))
 246
 247 /* x86 ELF linker hash table.  */
 248
 249 struct elf_x86_link_hash_table
 250 {
 251   struct elf_link_hash_table elf;
 252
 253   /* Short-cuts to get to dynamic linker sections.  */
 254   asection *interp;
 255   asection *plt_eh_frame;
 256   asection *plt_second;
 257   asection *plt_second_eh_frame;
 258   asection *plt_got;
 259   asection *plt_got_eh_frame;
 260
 261   /* Parameters describing PLT generation, lazy or non-lazy.  */
 262   struct elf_x86_plt_layout plt;
 263
 264   /* Parameters describing lazy PLT generation.  */
 265   const struct elf_x86_lazy_plt_layout *lazy_plt;
 266
 267   /* Parameters describing non-lazy PLT generation.  */
 268   const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
 269
 270   union
 271   {
 272     bfd_signed_vma refcount;
 273     bfd_vma offset;
 274   } tls_ld_or_ldm_got;
 275
 276   /* The amount of space used by the jump slots in the GOT.  */
 277   bfd_vma sgotplt_jump_table_size;
 278
 279   /* Small local sym cache.  */
 280   struct sym_cache sym_cache;
 281
 282   /* _TLS_MODULE_BASE_ symbol.  */
 283   struct bfd_link_hash_entry *tls_module_base;
 284
 285   /* Used by local STT_GNU_IFUNC symbols.  */
 286   htab_t loc_hash_table;
 287   void * loc_hash_memory;
 288
 289   /* The offset into sgot of the GOT entry used by the PLT entry
 290      above.  */
 291   bfd_vma tlsdesc_got;
 292
 293   /* The index of the next R_X86_64_JUMP_SLOT entry in .rela.plt.  */
 294   bfd_vma next_jump_slot_index;
 295   /* The index of the next R_X86_64_IRELATIVE entry in .rela.plt.  */
 296   bfd_vma next_irelative_index;
 297
 298   /* TRUE if there are dynamic relocs against IFUNC symbols that apply
 299      to read-only sections.  */
 300   bfd_boolean readonly_dynrelocs_against_ifunc;
 301
 302   /* TRUE if this is a VxWorks x86 target.  This is only used for
 303      i386.  */
 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 only used for i386.  */
 312   bfd_vma next_tls_desc_index;
 313
 314   /* The offset into splt of the PLT entry for the TLS descriptor
 315      resolver.  Special values are 0, if not necessary (or not found
 316      to be necessary yet), and -1 if needed but not determined
 317      yet.  This is only used for x86-64.  */
 318   bfd_vma tlsdesc_plt;
 319
 320   bfd_vma (*r_info) (bfd_vma, bfd_vma);
 321   bfd_vma (*r_sym) (bfd_vma);
 322   enum elf_target_id target_id;
 323   unsigned int sizeof_reloc;
 324   unsigned int got_entry_size;
 325   unsigned int pointer_r_type;
 326   int dynamic_interpreter_size;
 327   const char *dynamic_interpreter;
 328   const char *tls_get_addr;
 329 };
 330
 331 struct elf_x86_plt_layout_table
 332 {
 333   /* The lazy PLT layout.  */
 334   const struct elf_x86_lazy_plt_layout *lazy_plt;
 335
 336   /* The non-lazy PLT layout.  */
 337   const struct elf_x86_non_lazy_plt_layout *non_lazy_plt;
 338
 339   /* The lazy PLT layout for IBT.  */
 340   const struct elf_x86_lazy_plt_layout *lazy_ibt_plt;
 341
 342   /* The non-lazy PLT layout for IBT.  */
 343   const struct elf_x86_non_lazy_plt_layout *non_lazy_ibt_plt;
 344
 345   /* TRUE if this is a normal x86 target.  */
 346   bfd_boolean normal_target;
 347
 348   /* TRUE if this is a VxWorks x86 target.  */
 349   bfd_boolean is_vxworks;
 350 };
 351
 352 struct elf_x86_obj_tdata
 353 {
 354   struct elf_obj_tdata root;
 355
 356   /* tls_type for each local got entry.  */
 357   char *local_got_tls_type;
 358
 359   /* GOTPLT entries for TLS descriptors.  */
 360   bfd_vma *local_tlsdesc_gotent;
 361 };
 362
 363 enum elf_x86_plt_type
 364 {
 365   plt_non_lazy = 0,
 366   plt_lazy = 1 << 0,
 367   plt_pic = 1 << 1,
 368   plt_second = 1 << 2,
 369   plt_unknown = -1
 370 };
 371
 372 struct elf_x86_plt
 373 {
 374   const char *name;
 375   asection *sec;
 376   bfd_byte *contents;
 377   enum elf_x86_plt_type type;
 378   unsigned int plt_got_offset;
 379   unsigned int plt_entry_size;
 380   unsigned int plt_got_insn_size;       /* Only used for x86-64.  */
 381   long count;
 382 };
 383
 384 #define elf_x86_tdata(abfd) \
 385   ((struct elf_x86_obj_tdata *) (abfd)->tdata.any)
 386
 387 #define elf_x86_local_got_tls_type(abfd) \
 388   (elf_x86_tdata (abfd)->local_got_tls_type)
 389
 390 #define elf_x86_local_tlsdesc_gotent(abfd) \
 391   (elf_x86_tdata (abfd)->local_tlsdesc_gotent)
 392
 393 #define elf_x86_compute_jump_table_size(htab) \
 394   ((htab)->elf.srelplt->reloc_count * (htab)->got_entry_size)
 395
 396 #define is_x86_elf(bfd, htab)                           \
 397   (bfd_get_flavour (bfd) == bfd_target_elf_flavour      \
 398    && elf_tdata (bfd) != NULL                           \
 399    && elf_object_id (bfd) == (htab)->target_id)
 400
 401 extern bfd_boolean _bfd_x86_elf_mkobject
 402   (bfd *);
 403
 404 extern void _bfd_x86_elf_set_tls_module_base
 405   (struct bfd_link_info *);
 406
 407 extern bfd_vma _bfd_x86_elf_dtpoff_base
 408   (struct bfd_link_info *);
 409
 410 extern bfd_boolean _bfd_x86_elf_allocate_dynrelocs
 411   (struct elf_link_hash_entry *, void *);
 412
 413 extern bfd_boolean _bfd_x86_elf_allocate_local_dynrelocs
 414   (void **, void *);
 415
 416 extern bfd_boolean _bfd_x86_elf_readonly_dynrelocs
 417   (struct elf_link_hash_entry *, void *);
 418
 419 extern struct elf_link_hash_entry * _bfd_elf_x86_get_local_sym_hash
 420   (struct elf_x86_link_hash_table *, bfd *, const Elf_Internal_Rela *,
 421    bfd_boolean);
 422
 423 extern hashval_t _bfd_x86_elf_local_htab_hash
 424   (const void *);
 425
 426 extern int _bfd_x86_elf_local_htab_eq
 427   (const void *, const void *);
 428
 429 extern struct bfd_hash_entry * _bfd_x86_elf_link_hash_newfunc
 430   (struct bfd_hash_entry *, struct bfd_hash_table *, const char *);
 431
 432 extern struct bfd_link_hash_table * _bfd_x86_elf_link_hash_table_create
 433   (bfd *);
 434
 435 extern int _bfd_x86_elf_compare_relocs
 436   (const void *, const void *);
 437
 438 extern bfd_boolean _bfd_x86_elf_link_check_relocs
 439   (bfd *, struct bfd_link_info *);
 440
 441 extern bfd_boolean _bfd_x86_elf_always_size_sections
 442   (bfd *, struct bfd_link_info *);
 443
 444 extern void _bfd_x86_elf_merge_symbol_attribute
 445   (struct elf_link_hash_entry *, const Elf_Internal_Sym *,
 446    bfd_boolean, bfd_boolean);
 447
 448 extern void _bfd_x86_elf_copy_indirect_symbol
 449   (struct bfd_link_info *, struct elf_link_hash_entry *,
 450    struct elf_link_hash_entry *);
 451
 452 extern bfd_boolean _bfd_x86_elf_fixup_symbol
 453   (struct bfd_link_info *, struct elf_link_hash_entry *);
 454
 455 extern bfd_boolean _bfd_x86_elf_hash_symbol
 456   (struct elf_link_hash_entry *);
 457
 458 extern bfd_boolean _bfd_x86_elf_adjust_dynamic_symbol
 459   (struct bfd_link_info *, struct elf_link_hash_entry *);
 460
 461 extern asection * _bfd_x86_elf_gc_mark_hook
 462   (asection *, struct bfd_link_info *, Elf_Internal_Rela *,
 463    struct elf_link_hash_entry *, Elf_Internal_Sym *);
 464
 465 extern long _bfd_x86_elf_get_synthetic_symtab
 466   (bfd *, long, long, bfd_vma, struct elf_x86_plt [], asymbol **,
 467    asymbol **);
 468
 469 extern enum elf_property_kind _bfd_x86_elf_parse_gnu_properties
 470   (bfd *, unsigned int, bfd_byte *, unsigned int);
 471
 472 extern bfd_boolean _bfd_x86_elf_merge_gnu_properties
 473   (struct bfd_link_info *, bfd *, elf_property *, elf_property *);
 474
 475 extern bfd * _bfd_x86_elf_link_setup_gnu_properties
 476   (struct bfd_link_info *, struct elf_x86_plt_layout_table *);
 477
 478 #define bfd_elf64_mkobject \
 479   _bfd_x86_elf_mkobject
 480 #define bfd_elf32_mkobject \
 481   _bfd_x86_elf_mkobject
 482 #define bfd_elf64_bfd_link_hash_table_create \
 483   _bfd_x86_elf_link_hash_table_create
 484 #define bfd_elf32_bfd_link_hash_table_create \
 485   _bfd_x86_elf_link_hash_table_create
 486 #define bfd_elf64_bfd_link_check_relocs \
 487   _bfd_x86_elf_link_check_relocs
 488 #define bfd_elf32_bfd_link_check_relocs \
 489   _bfd_x86_elf_link_check_relocs
 490
 491 #define elf_backend_always_size_sections \
 492   _bfd_x86_elf_always_size_sections
 493 #define elf_backend_merge_symbol_attribute \
 494   _bfd_x86_elf_merge_symbol_attribute
 495 #define elf_backend_copy_indirect_symbol \
 496   _bfd_x86_elf_copy_indirect_symbol
 497 #define elf_backend_fixup_symbol \
 498   _bfd_x86_elf_fixup_symbol
 499 #define elf_backend_hash_symbol \
 500   _bfd_x86_elf_hash_symbol
 501 #define elf_backend_adjust_dynamic_symbol \
 502   _bfd_x86_elf_adjust_dynamic_symbol
 503 #define elf_backend_gc_mark_hook \
 504   _bfd_x86_elf_gc_mark_hook
 505 #define elf_backend_omit_section_dynsym \
 506   ((bfd_boolean (*) (bfd *, struct bfd_link_info *, asection *)) bfd_true)
 507 #define elf_backend_parse_gnu_properties \
 508   _bfd_x86_elf_parse_gnu_properties
 509 #define elf_backend_merge_gnu_properties \
 510   _bfd_x86_elf_merge_gnu_properties