EXTERNAL_HEADERS/mach-o/nlist.h

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