EXTERNAL_HEADERS/mach-o/x86_64/reloc.h

   1 /*
   2  * Copyright (c) 2006 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23 /*
  24  * Relocations for x86_64 are a bit different than for other architectures in
  25  * Mach-O: Scattered relocations are not used.  Almost all relocations produced
  26  * by the compiler are external relocations.  An external relocation has the
  27  * r_extern bit set to 1 and the r_symbolnum field contains the symbol table
  28  * index of the target label.
  29  *
  30  * When the assembler is generating relocations, if the target label is a local
  31  * label (begins with 'L'), then the previous non-local label in the same
  32  * section is used as the target of the external relocation.  An addend is used
  33  * with the distance from that non-local label to the target label.  Only when
  34  * there is no previous non-local label in the section is an internal
  35  * relocation used.
  36  *
  37  * The addend (i.e. the 4 in _foo+4) is encoded in the instruction (Mach-O does
  38  * not have RELA relocations).  For PC-relative relocations, the addend is
  39  * stored directly in the instruction.  This is different from other Mach-O
  40  * architectures, which encode the addend minus the current section offset.
  41  *
  42  * The relocation types are:
  43  *
  44  *      X86_64_RELOC_UNSIGNED   // for absolute addresses
  45  *      X86_64_RELOC_SIGNED             // for signed 32-bit displacement
  46  *      X86_64_RELOC_BRANCH             // a CALL/JMP instruction with 32-bit displacement
  47  *      X86_64_RELOC_GOT_LOAD   // a MOVQ load of a GOT entry
  48  *      X86_64_RELOC_GOT                // other GOT references
  49  *      X86_64_RELOC_SUBTRACTOR // must be followed by a X86_64_RELOC_UNSIGNED
  50  *
  51  * The following are sample assembly instructions, followed by the relocation
  52  * and section content they generate in an object file:
  53  *
  54  *      call _foo
  55  *              r_type=X86_64_RELOC_BRANCH, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo
  56  *              E8 00 00 00 00
  57  *
  58  *      call _foo+4
  59  *              r_type=X86_64_RELOC_BRANCH, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo
  60  *              E8 04 00 00 00
  61  *
  62  *      movq _foo@GOTPCREL(%rip), %rax
  63  *              r_type=X86_64_RELOC_GOT_LOAD, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo
  64  *              48 8B 05 00 00 00 00
  65  *
  66  *      pushq _foo@GOTPCREL(%rip)
  67  *              r_type=X86_64_RELOC_GOT, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo
  68  *              FF 35 00 00 00 00
  69  *
  70  *      movl _foo(%rip), %eax
  71  *              r_type=X86_64_RELOC_SIGNED, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo
  72  *              8B 05 00 00 00 00
  73  *
  74  *      movl _foo+4(%rip), %eax
  75  *              r_type=X86_64_RELOC_SIGNED, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo
  76  *              8B 05 04 00 00 00
  77  *
  78  *      movb  $0x12, _foo(%rip)
  79  *              r_type=X86_64_RELOC_SIGNED, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo
  80  *              C6 05 FF FF FF FF 12
  81  *
  82  *      movl  $0x12345678, _foo(%rip)
  83  *              r_type=X86_64_RELOC_SIGNED, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo
  84  *              C7 05 FC FF FF FF 78 56 34 12
  85  *
  86  *      .quad _foo
  87  *              r_type=X86_64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo
  88  *              00 00 00 00 00 00 00 00
  89  *
  90  *      .quad _foo+4
  91  *              r_type=X86_64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo
  92  *              04 00 00 00 00 00 00 00
  93  *
  94  *      .quad _foo - _bar
  95  *              r_type=X86_64_RELOC_SUBTRACTOR, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_bar
  96  *              r_type=X86_64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo
  97  *              00 00 00 00 00 00 00 00
  98  *
  99  *      .quad _foo - _bar + 4
 100  *              r_type=X86_64_RELOC_SUBTRACTOR, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_bar
 101  *              r_type=X86_64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo
 102  *              04 00 00 00 00 00 00 00
 103  *
 104  *      .long _foo - _bar
 105  *              r_type=X86_64_RELOC_SUBTRACTOR, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_bar
 106  *              r_type=X86_64_RELOC_UNSIGNED, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo
 107  *              00 00 00 00
 108  *
 109  *      lea L1(%rip), %rax
 110  *              r_type=X86_64_RELOC_SIGNED, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_prev
 111  *              48 8d 05 12 00 00 00
 112  *              // assumes _prev is the first non-local label 0x12 bytes before L1
 113  *
 114  *      lea L0(%rip), %rax
 115  *              r_type=X86_64_RELOC_SIGNED, r_length=2, r_extern=0, r_pcrel=1, r_symbolnum=3
 116  *              48 8d 05 56 00 00 00
 117  *              // assumes L0 is in third section and there is no previous non-local label.
 118  *              // The rip-relative-offset of 0x00000056 is L0-address_of_next_instruction.
 119  *              // address_of_next_instruction is the address of the relocation + 4.
 120  *
 121  *     add     $6,L0(%rip)
 122  *             r_type=X86_64_RELOC_SIGNED_1, r_length=2, r_extern=0, r_pcrel=1, r_symbolnum=3
 123  *              83 05 18 00 00 00 06
 124  *              // assumes L0 is in third section and there is no previous non-local label.
 125  *              // The rip-relative-offset of 0x00000018 is L0-address_of_next_instruction.
 126  *              // address_of_next_instruction is the address of the relocation + 4 + 1.
 127  *              // The +1 comes from SIGNED_1.  This is used because the relocation is not
 128  *              // at the end of the instruction.
 129  *
 130  *      .quad L1
 131  *              r_type=X86_64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_prev
 132  *              12 00 00 00 00 00 00 00
 133  *              // assumes _prev is the first non-local label 0x12 bytes before L1
 134  *
 135  *      .quad L0
 136  *              r_type=X86_64_RELOC_UNSIGNED, r_length=3, r_extern=0, r_pcrel=0, r_symbolnum=3
 137  *              56 00 00 00 00 00 00 00
 138  *              // assumes L0 is in third section, has an address of 0x00000056 in .o
 139  *              // file, and there is no previous non-local label
 140  *
 141  *      .quad _foo - .
 142  *              r_type=X86_64_RELOC_SUBTRACTOR, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_prev
 143  *              r_type=X86_64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo
 144  *              EE FF FF FF FF FF FF FF
 145  *              // assumes _prev is the first non-local label 0x12 bytes before this
 146  *              // .quad
 147  *
 148  *      .quad _foo - L1
 149  *              r_type=X86_64_RELOC_SUBTRACTOR, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_prev
 150  *              r_type=X86_64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo
 151  *              EE FF FF FF FF FF FF FF
 152  *              // assumes _prev is the first non-local label 0x12 bytes before L1
 153  *
 154  *      .quad L1 - _prev
 155  *              // No relocations.  This is an assembly time constant.
 156  *              12 00 00 00 00 00 00 00
 157  *              // assumes _prev is the first non-local label 0x12 bytes before L1
 158  *
 159  *
 160  *
 161  * In final linked images, there are only two valid relocation kinds:
 162  *
 163  *     r_type=X86_64_RELOC_UNSIGNED, r_length=3, r_pcrel=0, r_extern=1, r_symbolnum=sym_index
 164  *      This tells dyld to add the address of a symbol to a pointer sized (8-byte)
 165  *  piece of data (i.e on disk the 8-byte piece of data contains the addend). The
 166  *  r_symbolnum contains the index into the symbol table of the target symbol.
 167  *
 168  *     r_type=X86_64_RELOC_UNSIGNED, r_length=3, r_pcrel=0, r_extern=0, r_symbolnum=0
 169  * This tells dyld to adjust the pointer sized (8-byte) piece of data by the amount
 170  * the containing image was loaded from its base address (e.g. slide).
 171  *
 172  */
 173 enum reloc_type_x86_64
 174 {
 175         X86_64_RELOC_UNSIGNED,          // for absolute addresses
 176         X86_64_RELOC_SIGNED,            // for signed 32-bit displacement
 177         X86_64_RELOC_BRANCH,            // a CALL/JMP instruction with 32-bit displacement
 178         X86_64_RELOC_GOT_LOAD,          // a MOVQ load of a GOT entry
 179         X86_64_RELOC_GOT,                       // other GOT references
 180         X86_64_RELOC_SUBTRACTOR,        // must be followed by a X86_64_RELOC_UNSIGNED
 181         X86_64_RELOC_SIGNED_1,          // for signed 32-bit displacement with a -1 addend
 182         X86_64_RELOC_SIGNED_2,          // for signed 32-bit displacement with a -2 addend
 183         X86_64_RELOC_SIGNED_4,          // for signed 32-bit displacement with a -4 addend
 184         X86_64_RELOC_TLV,               // for thread local variables
 185 };