| 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 | };␊ |
| 186 | |
