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 */
173enum 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