1 | /* |
2 | * Copyright (c) 1999 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 | /* $NetBSD: exec.h,v 1.6 1994/10/27 04:16:05 cgd Exp $ */ |
24 | |
25 | /* |
26 | * Copyright (c) 1993 Christopher G. Demetriou |
27 | * All rights reserved. |
28 | * |
29 | * Redistribution and use in source and binary forms, with or without |
30 | * modification, are permitted provided that the following conditions |
31 | * are met: |
32 | * 1. Redistributions of source code must retain the above copyright |
33 | * notice, this list of conditions and the following disclaimer. |
34 | * 2. Redistributions in binary form must reproduce the above copyright |
35 | * notice, this list of conditions and the following disclaimer in the |
36 | * documentation and/or other materials provided with the distribution. |
37 | * 3. The name of the author may not be used to endorse or promote products |
38 | * derived from this software without specific prior written permission |
39 | * |
40 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
41 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
42 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
43 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
44 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
45 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
46 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
47 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
48 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
49 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
50 | */ |
51 | |
52 | #ifndef _MACHO_RELOC_H_ |
53 | #define _MACHO_RELOC_H_ |
54 | #include <stdint.h> |
55 | |
56 | /* |
57 | * Format of a relocation entry of a Mach-O file. Modified from the 4.3BSD |
58 | * format. The modifications from the original format were changing the value |
59 | * of the r_symbolnum field for "local" (r_extern == 0) relocation entries. |
60 | * This modification is required to support symbols in an arbitrary number of |
61 | * sections not just the three sections (text, data and bss) in a 4.3BSD file. |
62 | * Also the last 4 bits have had the r_type tag added to them. |
63 | */ |
64 | struct relocation_info { |
65 | int32_t r_address; /* offset in the section to what is being |
66 | relocated */ |
67 | uint32_t r_symbolnum:24, /* symbol index if r_extern == 1 or section |
68 | ordinal if r_extern == 0 */ |
69 | r_pcrel:1, /* was relocated pc relative already */ |
70 | r_length:2, /* 0=byte, 1=word, 2=long, 3=quad */ |
71 | r_extern:1, /* does not include value of sym referenced */ |
72 | r_type:4; /* if not 0, machine specific relocation type */ |
73 | }; |
74 | #define R_ABS 0 /* absolute relocation type for Mach-O files */ |
75 | |
76 | /* |
77 | * The r_address is not really the address as it's name indicates but an offset. |
78 | * In 4.3BSD a.out objects this offset is from the start of the "segment" for |
79 | * which relocation entry is for (text or data). For Mach-O object files it is |
80 | * also an offset but from the start of the "section" for which the relocation |
81 | * entry is for. See comments in <mach-o/loader.h> about the r_address feild |
82 | * in images for used with the dynamic linker. |
83 | * |
84 | * In 4.3BSD a.out objects if r_extern is zero then r_symbolnum is an ordinal |
85 | * for the segment the symbol being relocated is in. These ordinals are the |
86 | * symbol types N_TEXT, N_DATA, N_BSS or N_ABS. In Mach-O object files these |
87 | * ordinals refer to the sections in the object file in the order their section |
88 | * structures appear in the headers of the object file they are in. The first |
89 | * section has the ordinal 1, the second 2, and so on. This means that the |
90 | * same ordinal in two different object files could refer to two different |
91 | * sections. And further could have still different ordinals when combined |
92 | * by the link-editor. The value R_ABS is used for relocation entries for |
93 | * absolute symbols which need no further relocation. |
94 | */ |
95 | |
96 | /* |
97 | * For RISC machines some of the references are split across two instructions |
98 | * and the instruction does not contain the complete value of the reference. |
99 | * In these cases a second, or paired relocation entry, follows each of these |
100 | * relocation entries, using a PAIR r_type, which contains the other part of the |
101 | * reference not contained in the instruction. This other part is stored in the |
102 | * pair's r_address field. The exact number of bits of the other part of the |
103 | * reference store in the r_address field is dependent on the particular |
104 | * relocation type for the particular architecture. |
105 | */ |
106 | |
107 | /* |
108 | * To make scattered loading by the link editor work correctly "local" |
109 | * relocation entries can't be used when the item to be relocated is the value |
110 | * of a symbol plus an offset (where the resulting expresion is outside the |
111 | * block the link editor is moving, a blocks are divided at symbol addresses). |
112 | * In this case. where the item is a symbol value plus offset, the link editor |
113 | * needs to know more than just the section the symbol was defined. What is |
114 | * needed is the actual value of the symbol without the offset so it can do the |
115 | * relocation correctly based on where the value of the symbol got relocated to |
116 | * not the value of the expression (with the offset added to the symbol value). |
117 | * So for the NeXT 2.0 release no "local" relocation entries are ever used when |
118 | * there is a non-zero offset added to a symbol. The "external" and "local" |
119 | * relocation entries remain unchanged. |
120 | * |
121 | * The implemention is quite messy given the compatibility with the existing |
122 | * relocation entry format. The ASSUMPTION is that a section will never be |
123 | * bigger than 2**24 - 1 (0x00ffffff or 16,777,215) bytes. This assumption |
124 | * allows the r_address (which is really an offset) to fit in 24 bits and high |
125 | * bit of the r_address field in the relocation_info structure to indicate |
126 | * it is really a scattered_relocation_info structure. Since these are only |
127 | * used in places where "local" relocation entries are used and not where |
128 | * "external" relocation entries are used the r_extern field has been removed. |
129 | * |
130 | * For scattered loading to work on a RISC machine where some of the references |
131 | * are split across two instructions the link editor needs to be assured that |
132 | * each reference has a unique 32 bit reference (that more than one reference is |
133 | * NOT sharing the same high 16 bits for example) so it move each referenced |
134 | * item independent of each other. Some compilers guarantees this but the |
135 | * compilers don't so scattered loading can be done on those that do guarantee |
136 | * this. |
137 | */ |
138 | #if defined(__BIG_ENDIAN__) || defined(__LITTLE_ENDIAN__) |
139 | /* |
140 | * The reason for the ifdef's of __BIG_ENDIAN__ and __LITTLE_ENDIAN__ are that |
141 | * when stattered relocation entries were added the mistake of using a mask |
142 | * against a structure that is made up of bit fields was used. To make this |
143 | * design work this structure must be laid out in memory the same way so the |
144 | * mask can be applied can check the same bit each time (r_scattered). |
145 | */ |
146 | #endif /* defined(__BIG_ENDIAN__) || defined(__LITTLE_ENDIAN__) */ |
147 | #define R_SCATTERED 0x80000000 /* mask to be applied to the r_address field |
148 | of a relocation_info structure to tell that |
149 | is is really a scattered_relocation_info |
150 | stucture */ |
151 | struct scattered_relocation_info { |
152 | #ifdef __BIG_ENDIAN__ |
153 | uint32_t r_scattered:1, /* 1=scattered, 0=non-scattered (see above) */ |
154 | r_pcrel:1, /* was relocated pc relative already */ |
155 | r_length:2, /* 0=byte, 1=word, 2=long, 3=quad */ |
156 | r_type:4, /* if not 0, machine specific relocation type */ |
157 | r_address:24; /* offset in the section to what is being |
158 | relocated */ |
159 | int32_t r_value; /* the value the item to be relocated is |
160 | refering to (without any offset added) */ |
161 | #endif /* __BIG_ENDIAN__ */ |
162 | #ifdef __LITTLE_ENDIAN__ |
163 | uint32_t |
164 | r_address:24, /* offset in the section to what is being |
165 | relocated */ |
166 | r_type:4, /* if not 0, machine specific relocation type */ |
167 | r_length:2, /* 0=byte, 1=word, 2=long, 3=quad */ |
168 | r_pcrel:1, /* was relocated pc relative already */ |
169 | r_scattered:1; /* 1=scattered, 0=non-scattered (see above) */ |
170 | int32_t r_value; /* the value the item to be relocated is |
171 | refering to (without any offset added) */ |
172 | #endif /* __LITTLE_ENDIAN__ */ |
173 | }; |
174 | |
175 | /* |
176 | * Relocation types used in a generic implementation. Relocation entries for |
177 | * normal things use the generic relocation as discribed above and their r_type |
178 | * is GENERIC_RELOC_VANILLA (a value of zero). |
179 | * |
180 | * Another type of generic relocation, GENERIC_RELOC_SECTDIFF, is to support |
181 | * the difference of two symbols defined in different sections. That is the |
182 | * expression "symbol1 - symbol2 + constant" is a relocatable expression when |
183 | * both symbols are defined in some section. For this type of relocation the |
184 | * both relocations entries are scattered relocation entries. The value of |
185 | * symbol1 is stored in the first relocation entry's r_value field and the |
186 | * value of symbol2 is stored in the pair's r_value field. |
187 | * |
188 | * A special case for a prebound lazy pointer is needed to beable to set the |
189 | * value of the lazy pointer back to its non-prebound state. This is done |
190 | * using the GENERIC_RELOC_PB_LA_PTR r_type. This is a scattered relocation |
191 | * entry where the r_value feild is the value of the lazy pointer not prebound. |
192 | */ |
193 | enum reloc_type_generic |
194 | { |
195 | GENERIC_RELOC_VANILLA, /* generic relocation as discribed above */ |
196 | GENERIC_RELOC_PAIR, /* Only follows a GENERIC_RELOC_SECTDIFF */ |
197 | GENERIC_RELOC_SECTDIFF, |
198 | GENERIC_RELOC_PB_LA_PTR, /* prebound lazy pointer */ |
199 | GENERIC_RELOC_LOCAL_SECTDIFF, |
200 | GENERIC_RELOC_TLV /* thread local variables */ |
201 | }; |
202 | |
203 | #endif /* _MACHO_RELOC_H_ */ |
204 | |