| /* |
| * Copyright (c) 1999 Apple Computer, Inc. All rights reserved. |
| * |
| * @APPLE_LICENSE_HEADER_START@ |
| * |
| * This file contains Original Code and/or Modifications of Original Code |
| * as defined in and that are subject to the Apple Public Source License |
| * Version 2.0 (the 'License'). You may not use this file except in |
| * compliance with the License. Please obtain a copy of the License at |
| * http://www.opensource.apple.com/apsl/ and read it before using this |
| * file. |
| * |
| * The Original Code and all software distributed under the License are |
| * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER |
| * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, |
| * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, |
| * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. |
| * Please see the License for the specific language governing rights and |
| * limitations under the License. |
| * |
| * @APPLE_LICENSE_HEADER_END@ |
| */ |
| /* $NetBSD: exec.h,v 1.6 1994/10/27 04:16:05 cgd Exp $ */ |
| |
| /* |
| * Copyright (c) 1993 Christopher G. Demetriou |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #ifndef _MACHO_RELOC_H_ |
| #define _MACHO_RELOC_H_ |
| #include <stdint.h> |
| |
| /* |
| * Format of a relocation entry of a Mach-O file. Modified from the 4.3BSD |
| * format. The modifications from the original format were changing the value |
| * of the r_symbolnum field for "local" (r_extern == 0) relocation entries. |
| * This modification is required to support symbols in an arbitrary number of |
| * sections not just the three sections (text, data and bss) in a 4.3BSD file. |
| * Also the last 4 bits have had the r_type tag added to them. |
| */ |
| struct relocation_info { |
| int32_t r_address; /* offset in the section to what is being |
| relocated */ |
| uint32_t r_symbolnum:24, /* symbol index if r_extern == 1 or section |
| ordinal if r_extern == 0 */ |
| r_pcrel:1, /* was relocated pc relative already */ |
| r_length:2, /* 0=byte, 1=word, 2=long, 3=quad */ |
| r_extern:1, /* does not include value of sym referenced */ |
| r_type:4; /* if not 0, machine specific relocation type */ |
| }; |
| #define R_ABS 0 /* absolute relocation type for Mach-O files */ |
| |
| /* |
| * The r_address is not really the address as it's name indicates but an offset. |
| * In 4.3BSD a.out objects this offset is from the start of the "segment" for |
| * which relocation entry is for (text or data). For Mach-O object files it is |
| * also an offset but from the start of the "section" for which the relocation |
| * entry is for. See comments in <mach-o/loader.h> about the r_address feild |
| * in images for used with the dynamic linker. |
| * |
| * In 4.3BSD a.out objects if r_extern is zero then r_symbolnum is an ordinal |
| * for the segment the symbol being relocated is in. These ordinals are the |
| * symbol types N_TEXT, N_DATA, N_BSS or N_ABS. In Mach-O object files these |
| * ordinals refer to the sections in the object file in the order their section |
| * structures appear in the headers of the object file they are in. The first |
| * section has the ordinal 1, the second 2, and so on. This means that the |
| * same ordinal in two different object files could refer to two different |
| * sections. And further could have still different ordinals when combined |
| * by the link-editor. The value R_ABS is used for relocation entries for |
| * absolute symbols which need no further relocation. |
| */ |
| |
| /* |
| * For RISC machines some of the references are split across two instructions |
| * and the instruction does not contain the complete value of the reference. |
| * In these cases a second, or paired relocation entry, follows each of these |
| * relocation entries, using a PAIR r_type, which contains the other part of the |
| * reference not contained in the instruction. This other part is stored in the |
| * pair's r_address field. The exact number of bits of the other part of the |
| * reference store in the r_address field is dependent on the particular |
| * relocation type for the particular architecture. |
| */ |
| |
| /* |
| * To make scattered loading by the link editor work correctly "local" |
| * relocation entries can't be used when the item to be relocated is the value |
| * of a symbol plus an offset (where the resulting expresion is outside the |
| * block the link editor is moving, a blocks are divided at symbol addresses). |
| * In this case. where the item is a symbol value plus offset, the link editor |
| * needs to know more than just the section the symbol was defined. What is |
| * needed is the actual value of the symbol without the offset so it can do the |
| * relocation correctly based on where the value of the symbol got relocated to |
| * not the value of the expression (with the offset added to the symbol value). |
| * So for the NeXT 2.0 release no "local" relocation entries are ever used when |
| * there is a non-zero offset added to a symbol. The "external" and "local" |
| * relocation entries remain unchanged. |
| * |
| * The implemention is quite messy given the compatibility with the existing |
| * relocation entry format. The ASSUMPTION is that a section will never be |
| * bigger than 2**24 - 1 (0x00ffffff or 16,777,215) bytes. This assumption |
| * allows the r_address (which is really an offset) to fit in 24 bits and high |
| * bit of the r_address field in the relocation_info structure to indicate |
| * it is really a scattered_relocation_info structure. Since these are only |
| * used in places where "local" relocation entries are used and not where |
| * "external" relocation entries are used the r_extern field has been removed. |
| * |
| * For scattered loading to work on a RISC machine where some of the references |
| * are split across two instructions the link editor needs to be assured that |
| * each reference has a unique 32 bit reference (that more than one reference is |
| * NOT sharing the same high 16 bits for example) so it move each referenced |
| * item independent of each other. Some compilers guarantees this but the |
| * compilers don't so scattered loading can be done on those that do guarantee |
| * this. |
| */ |
| #if defined(__BIG_ENDIAN__) || defined(__LITTLE_ENDIAN__) |
| /* |
| * The reason for the ifdef's of __BIG_ENDIAN__ and __LITTLE_ENDIAN__ are that |
| * when stattered relocation entries were added the mistake of using a mask |
| * against a structure that is made up of bit fields was used. To make this |
| * design work this structure must be laid out in memory the same way so the |
| * mask can be applied can check the same bit each time (r_scattered). |
| */ |
| #endif /* defined(__BIG_ENDIAN__) || defined(__LITTLE_ENDIAN__) */ |
| #define R_SCATTERED 0x80000000 /* mask to be applied to the r_address field |
| of a relocation_info structure to tell that |
| is is really a scattered_relocation_info |
| stucture */ |
| struct scattered_relocation_info { |
| #ifdef __BIG_ENDIAN__ |
| uint32_t r_scattered:1, /* 1=scattered, 0=non-scattered (see above) */ |
| r_pcrel:1, /* was relocated pc relative already */ |
| r_length:2, /* 0=byte, 1=word, 2=long, 3=quad */ |
| r_type:4, /* if not 0, machine specific relocation type */ |
| r_address:24; /* offset in the section to what is being |
| relocated */ |
| int32_t r_value; /* the value the item to be relocated is |
| refering to (without any offset added) */ |
| #endif /* __BIG_ENDIAN__ */ |
| #ifdef __LITTLE_ENDIAN__ |
| uint32_t |
| r_address:24, /* offset in the section to what is being |
| relocated */ |
| r_type:4, /* if not 0, machine specific relocation type */ |
| r_length:2, /* 0=byte, 1=word, 2=long, 3=quad */ |
| r_pcrel:1, /* was relocated pc relative already */ |
| r_scattered:1; /* 1=scattered, 0=non-scattered (see above) */ |
| int32_t r_value; /* the value the item to be relocated is |
| refering to (without any offset added) */ |
| #endif /* __LITTLE_ENDIAN__ */ |
| }; |
| |
| /* |
| * Relocation types used in a generic implementation. Relocation entries for |
| * normal things use the generic relocation as discribed above and their r_type |
| * is GENERIC_RELOC_VANILLA (a value of zero). |
| * |
| * Another type of generic relocation, GENERIC_RELOC_SECTDIFF, is to support |
| * the difference of two symbols defined in different sections. That is the |
| * expression "symbol1 - symbol2 + constant" is a relocatable expression when |
| * both symbols are defined in some section. For this type of relocation the |
| * both relocations entries are scattered relocation entries. The value of |
| * symbol1 is stored in the first relocation entry's r_value field and the |
| * value of symbol2 is stored in the pair's r_value field. |
| * |
| * A special case for a prebound lazy pointer is needed to beable to set the |
| * value of the lazy pointer back to its non-prebound state. This is done |
| * using the GENERIC_RELOC_PB_LA_PTR r_type. This is a scattered relocation |
| * entry where the r_value feild is the value of the lazy pointer not prebound. |
| */ |
| enum reloc_type_generic |
| { |
| GENERIC_RELOC_VANILLA, /* generic relocation as discribed above */ |
| GENERIC_RELOC_PAIR, /* Only follows a GENERIC_RELOC_SECTDIFF */ |
| GENERIC_RELOC_SECTDIFF, |
| GENERIC_RELOC_PB_LA_PTR, /* prebound lazy pointer */ |
| GENERIC_RELOC_LOCAL_SECTDIFF, |
| GENERIC_RELOC_TLV /* thread local variables */ |
| }; |
| |
| #endif /* _MACHO_RELOC_H_ */ |
