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Annotation of XNU/EXTERNAL_HEADERS/mach-o/nlist.h, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: #ifndef _MACHO_NLIST_H_
        !            25: #define _MACHO_NLIST_H_
        !            26: /*     $NetBSD: nlist.h,v 1.5 1994/10/26 00:56:11 cgd Exp $    */
        !            27: 
        !            28: /*-
        !            29:  * Copyright (c) 1991, 1993
        !            30:  *     The Regents of the University of California.  All rights reserved.
        !            31:  * (c) UNIX System Laboratories, Inc.
        !            32:  * All or some portions of this file are derived from material licensed
        !            33:  * to the University of California by American Telephone and Telegraph
        !            34:  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
        !            35:  * the permission of UNIX System Laboratories, Inc.
        !            36:  *
        !            37:  * Redistribution and use in source and binary forms, with or without
        !            38:  * modification, are permitted provided that the following conditions
        !            39:  * are met:
        !            40:  * 1. Redistributions of source code must retain the above copyright
        !            41:  *    notice, this list of conditions and the following disclaimer.
        !            42:  * 2. Redistributions in binary form must reproduce the above copyright
        !            43:  *    notice, this list of conditions and the following disclaimer in the
        !            44:  *    documentation and/or other materials provided with the distribution.
        !            45:  * 3. All advertising materials mentioning features or use of this software
        !            46:  *    must display the following acknowledgement:
        !            47:  *     This product includes software developed by the University of
        !            48:  *     California, Berkeley and its contributors.
        !            49:  * 4. Neither the name of the University nor the names of its contributors
        !            50:  *    may be used to endorse or promote products derived from this software
        !            51:  *    without specific prior written permission.
        !            52:  *
        !            53:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            54:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            55:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            56:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            57:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            58:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            59:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            60:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            61:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            62:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            63:  * SUCH DAMAGE.
        !            64:  *
        !            65:  *     @(#)nlist.h     8.2 (Berkeley) 1/21/94
        !            66:  */
        !            67: 
        !            68: /*
        !            69:  * Format of a symbol table entry of a Mach-O file.  Modified from the BSD
        !            70:  * format.  The modifications from the original format were changing n_other
        !            71:  * (an unused field) to n_sect and the addition of the N_SECT type.  These
        !            72:  * modifications are required to support symbols in an arbitrary number of
        !            73:  * sections not just the three sections (text, data and bss) in a BSD file.
        !            74:  */
        !            75: struct nlist {
        !            76:        union {
        !            77:                char *n_name;   /* for use when in-core */
        !            78:                long  n_strx;   /* index into the string table */
        !            79:        } n_un;
        !            80:        unsigned char n_type;   /* type flag, see below */
        !            81:        unsigned char n_sect;   /* section number or NO_SECT */
        !            82:        short         n_desc;   /* see <mach-o/stab.h> */
        !            83:        unsigned long n_value;  /* value of this symbol (or stab offset) */
        !            84: };
        !            85: 
        !            86: /*
        !            87:  * Symbols with a index into the string table of zero (n_un.n_strx == 0) are
        !            88:  * defined to have a null, "", name.  Therefore all string indexes to non null
        !            89:  * names must not have a zero string index.  This is bit historical information
        !            90:  * that has never been well documented.
        !            91:  */
        !            92: 
        !            93: /*
        !            94:  * The n_type field really contains three fields:
        !            95:  *     unsigned char N_STAB:3,
        !            96:  *                   N_PEXT:1,
        !            97:  *                   N_TYPE:3,
        !            98:  *                   N_EXT:1;
        !            99:  * which are used via the following masks.
        !           100:  */
        !           101: #define        N_STAB  0xe0  /* if any of these bits set, a symbolic debugging entry */
        !           102: #define        N_PEXT  0x10  /* private external symbol bit */
        !           103: #define        N_TYPE  0x0e  /* mask for the type bits */
        !           104: #define        N_EXT   0x01  /* external symbol bit, set for external symbols */
        !           105: 
        !           106: /*
        !           107:  * Only symbolic debugging entries have some of the N_STAB bits set and if any
        !           108:  * of these bits are set then it is a symbolic debugging entry (a stab).  In
        !           109:  * which case then the values of the n_type field (the entire field) are given
        !           110:  * in <mach-o/stab.h>
        !           111:  */
        !           112: 
        !           113: /*
        !           114:  * Values for N_TYPE bits of the n_type field.
        !           115:  */
        !           116: #define        N_UNDF  0x0             /* undefined, n_sect == NO_SECT */
        !           117: #define        N_ABS   0x2             /* absolute, n_sect == NO_SECT */
        !           118: #define        N_SECT  0xe             /* defined in section number n_sect */
        !           119: #define        N_PBUD  0xc             /* prebound undefined (defined in a dylib) */
        !           120: #define N_INDR 0xa             /* indirect */
        !           121: 
        !           122: /* 
        !           123:  * If the type is N_INDR then the symbol is defined to be the same as another
        !           124:  * symbol.  In this case the n_value field is an index into the string table
        !           125:  * of the other symbol's name.  When the other symbol is defined then they both
        !           126:  * take on the defined type and value.
        !           127:  */
        !           128: 
        !           129: /*
        !           130:  * If the type is N_SECT then the n_sect field contains an ordinal of the
        !           131:  * section the symbol is defined in.  The sections are numbered from 1 and 
        !           132:  * refer to sections in order they appear in the load commands for the file
        !           133:  * they are in.  This means the same ordinal may very well refer to different
        !           134:  * sections in different files.
        !           135:  *
        !           136:  * The n_value field for all symbol table entries (including N_STAB's) gets
        !           137:  * updated by the link editor based on the value of it's n_sect field and where
        !           138:  * the section n_sect references gets relocated.  If the value of the n_sect 
        !           139:  * field is NO_SECT then it's n_value field is not changed by the link editor.
        !           140:  */
        !           141: #define        NO_SECT         0       /* symbol is not in any section */
        !           142: #define MAX_SECT       255     /* 1 thru 255 inclusive */
        !           143: 
        !           144: /*
        !           145:  * Common symbols are represented by undefined (N_UNDF) external (N_EXT) types
        !           146:  * who's values (n_value) are non-zero.  In which case the value of the n_value
        !           147:  * field is the size (in bytes) of the common symbol.  The n_sect field is set
        !           148:  * to NO_SECT.
        !           149:  */
        !           150: 
        !           151: /*
        !           152:  * To support the lazy binding of undefined symbols in the dynamic link-editor,
        !           153:  * the undefined symbols in the symbol table (the nlist structures) are marked
        !           154:  * with the indication if the undefined reference is a lazy reference or
        !           155:  * non-lazy reference.  If both a non-lazy reference and a lazy reference is
        !           156:  * made to the same symbol the non-lazy reference takes precedence.  A reference
        !           157:  * is lazy only when all references to that symbol are made through a symbol
        !           158:  * pointer in a lazy symbol pointer section.
        !           159:  *
        !           160:  * The implementation of marking nlist structures in the symbol table for
        !           161:  * undefined symbols will be to use some of the bits of the n_desc field as a
        !           162:  * reference type.  The mask REFERENCE_TYPE will be applied to the n_desc field
        !           163:  * of an nlist structure for an undefined symbol to determine the type of
        !           164:  * undefined reference (lazy or non-lazy).
        !           165:  *
        !           166:  * The constants for the REFERENCE FLAGS are propagated to the reference table
        !           167:  * in a shared library file.  In that case the constant for a defined symbol,
        !           168:  * REFERENCE_FLAG_DEFINED, is also used.
        !           169:  */
        !           170: /* Reference type bits of the n_desc field of undefined symbols */
        !           171: #define REFERENCE_TYPE                         0xf
        !           172: /* types of references */
        !           173: #define REFERENCE_FLAG_UNDEFINED_NON_LAZY              0
        !           174: #define REFERENCE_FLAG_UNDEFINED_LAZY                  1
        !           175: #define REFERENCE_FLAG_DEFINED                         2
        !           176: #define REFERENCE_FLAG_PRIVATE_DEFINED                 3
        !           177: #define REFERENCE_FLAG_PRIVATE_UNDEFINED_NON_LAZY      4
        !           178: #define REFERENCE_FLAG_PRIVATE_UNDEFINED_LAZY          5
        !           179: 
        !           180: /*
        !           181:  * To simplify stripping of objects that use are used with the dynamic link
        !           182:  * editor, the static link editor marks the symbols defined an object that are
        !           183:  * referenced by a dynamicly bound object (dynamic shared libraries, bundles).
        !           184:  * With this marking strip knows not to strip these symbols.
        !           185:  */
        !           186: #define REFERENCED_DYNAMICALLY 0x0010
        !           187: 
        !           188: /*
        !           189:  * The non-reference type bits of the n_desc field for global symbols are
        !           190:  * reserved for the dynamic link editor.  All of these bits must start out
        !           191:  * zero in the object file.
        !           192:  */
        !           193: #define N_DESC_DISCARDED 0x8000        /* symbol is discarded */
        !           194: 
        !           195: #endif

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