| | 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_ */ |
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