EXTERNAL_HEADERS/mach-o/nlist.h

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_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. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 #ifndef _MACHO_NLIST_H_
  29 #define _MACHO_NLIST_H_
  30 /*      $NetBSD: nlist.h,v 1.5 1994/10/26 00:56:11 cgd Exp $    */
  31
  32 /*-
  33  * Copyright (c) 1991, 1993
  34  *      The Regents of the University of California.  All rights reserved.
  35  * (c) UNIX System Laboratories, Inc.
  36  * All or some portions of this file are derived from material licensed
  37  * to the University of California by American Telephone and Telegraph
  38  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
  39  * the permission of UNIX System Laboratories, Inc.
  40  *
  41  * Redistribution and use in source and binary forms, with or without
  42  * modification, are permitted provided that the following conditions
  43  * are met:
  44  * 1. Redistributions of source code must retain the above copyright
  45  *    notice, this list of conditions and the following disclaimer.
  46  * 2. Redistributions in binary form must reproduce the above copyright
  47  *    notice, this list of conditions and the following disclaimer in the
  48  *    documentation and/or other materials provided with the distribution.
  49  * 3. All advertising materials mentioning features or use of this software
  50  *    must display the following acknowledgement:
  51  *      This product includes software developed by the University of
  52  *      California, Berkeley and its contributors.
  53  * 4. Neither the name of the University nor the names of its contributors
  54  *    may be used to endorse or promote products derived from this software
  55  *    without specific prior written permission.
  56  *
  57  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  58  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  59  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  60  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  61  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  62  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  63  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  64  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  65  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  66  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  67  * SUCH DAMAGE.
  68  *
  69  *      @(#)nlist.h     8.2 (Berkeley) 1/21/94
  70  */
  71
  72 /*
  73  * Format of a symbol table entry of a Mach-O file.  Modified from the BSD
  74  * format.  The modifications from the original format were changing n_other
  75  * (an unused field) to n_sect and the addition of the N_SECT type.  These
  76  * modifications are required to support symbols in an arbitrary number of
  77  * sections not just the three sections (text, data and bss) in a BSD file.
  78  */
  79 struct nlist {
  80         union {
  81                 char *n_name;   /* for use when in-core */
  82                 long  n_strx;   /* index into the string table */
  83         } n_un;
  84         unsigned char n_type;   /* type flag, see below */
  85         unsigned char n_sect;   /* section number or NO_SECT */
  86         short         n_desc;   /* see <mach-o/stab.h> */
  87         unsigned long n_value;  /* value of this symbol (or stab offset) */
  88 };
  89
  90 /*
  91  * This is the symbol table entry structure for 64-bit architectures.
  92  */
  93 struct nlist_64 {
  94         union {
  95                 uint32_t n_strx;        /* index into the string table */
  96         } n_un;
  97         uint8_t n_type;         /* type flag, see below */
  98         uint8_t n_sect;         /* section number or NO_SECT */
  99         uint16_t n_desc;        /* see <mach-o/stab.h> */
 100         uint64_t n_value;       /* value of this symbol (or stab offset) */
 101 };
 102
 103
 104 /*
 105  * Symbols with a index into the string table of zero (n_un.n_strx == 0) are
 106  * defined to have a null, "", name.  Therefore all string indexes to non null
 107  * names must not have a zero string index.  This is bit historical information
 108  * that has never been well documented.
 109  */
 110
 111 /*
 112  * The n_type field really contains three fields:
 113  *      unsigned char N_STAB:3,
 114  *                    N_PEXT:1,
 115  *                    N_TYPE:3,
 116  *                    N_EXT:1;
 117  * which are used via the following masks.
 118  */
 119 #define N_STAB  0xe0  /* if any of these bits set, a symbolic debugging entry */
 120 #define N_PEXT  0x10  /* private external symbol bit */
 121 #define N_TYPE  0x0e  /* mask for the type bits */
 122 #define N_EXT   0x01  /* external symbol bit, set for external symbols */
 123
 124 /*
 125  * Only symbolic debugging entries have some of the N_STAB bits set and if any
 126  * of these bits are set then it is a symbolic debugging entry (a stab).  In
 127  * which case then the values of the n_type field (the entire field) are given
 128  * in <mach-o/stab.h>
 129  */
 130
 131 /*
 132  * Values for N_TYPE bits of the n_type field.
 133  */
 134 #define N_UNDF  0x0             /* undefined, n_sect == NO_SECT */
 135 #define N_ABS   0x2             /* absolute, n_sect == NO_SECT */
 136 #define N_SECT  0xe             /* defined in section number n_sect */
 137 #define N_PBUD  0xc             /* prebound undefined (defined in a dylib) */
 138 #define N_INDR  0xa             /* indirect */
 139
 140 /*
 141  * If the type is N_INDR then the symbol is defined to be the same as another
 142  * symbol.  In this case the n_value field is an index into the string table
 143  * of the other symbol's name.  When the other symbol is defined then they both
 144  * take on the defined type and value.
 145  */
 146
 147 /*
 148  * If the type is N_SECT then the n_sect field contains an ordinal of the
 149  * section the symbol is defined in.  The sections are numbered from 1 and
 150  * refer to sections in order they appear in the load commands for the file
 151  * they are in.  This means the same ordinal may very well refer to different
 152  * sections in different files.
 153  *
 154  * The n_value field for all symbol table entries (including N_STAB's) gets
 155  * updated by the link editor based on the value of it's n_sect field and where
 156  * the section n_sect references gets relocated.  If the value of the n_sect
 157  * field is NO_SECT then it's n_value field is not changed by the link editor.
 158  */
 159 #define NO_SECT         0       /* symbol is not in any section */
 160 #define MAX_SECT        255     /* 1 thru 255 inclusive */
 161
 162 /*
 163  * Common symbols are represented by undefined (N_UNDF) external (N_EXT) types
 164  * who's values (n_value) are non-zero.  In which case the value of the n_value
 165  * field is the size (in bytes) of the common symbol.  The n_sect field is set
 166  * to NO_SECT.
 167  */
 168
 169 /*
 170  * To support the lazy binding of undefined symbols in the dynamic link-editor,
 171  * the undefined symbols in the symbol table (the nlist structures) are marked
 172  * with the indication if the undefined reference is a lazy reference or
 173  * non-lazy reference.  If both a non-lazy reference and a lazy reference is
 174  * made to the same symbol the non-lazy reference takes precedence.  A reference
 175  * is lazy only when all references to that symbol are made through a symbol
 176  * pointer in a lazy symbol pointer section.
 177  *
 178  * The implementation of marking nlist structures in the symbol table for
 179  * undefined symbols will be to use some of the bits of the n_desc field as a
 180  * reference type.  The mask REFERENCE_TYPE will be applied to the n_desc field
 181  * of an nlist structure for an undefined symbol to determine the type of
 182  * undefined reference (lazy or non-lazy).
 183  *
 184  * The constants for the REFERENCE FLAGS are propagated to the reference table
 185  * in a shared library file.  In that case the constant for a defined symbol,
 186  * REFERENCE_FLAG_DEFINED, is also used.
 187  */
 188 /* Reference type bits of the n_desc field of undefined symbols */
 189 #define REFERENCE_TYPE                          0xf
 190 /* types of references */
 191 #define REFERENCE_FLAG_UNDEFINED_NON_LAZY               0
 192 #define REFERENCE_FLAG_UNDEFINED_LAZY                   1
 193 #define REFERENCE_FLAG_DEFINED                          2
 194 #define REFERENCE_FLAG_PRIVATE_DEFINED                  3
 195 #define REFERENCE_FLAG_PRIVATE_UNDEFINED_NON_LAZY       4
 196 #define REFERENCE_FLAG_PRIVATE_UNDEFINED_LAZY           5
 197
 198 /*
 199  * To simplify stripping of objects that use are used with the dynamic link
 200  * editor, the static link editor marks the symbols defined an object that are
 201  * referenced by a dynamicly bound object (dynamic shared libraries, bundles).
 202  * With this marking strip knows not to strip these symbols.
 203  */
 204 #define REFERENCED_DYNAMICALLY  0x0010
 205
 206 /*
 207  * The non-reference type bits of the n_desc field for global symbols are
 208  * reserved for the dynamic link editor.  All of these bits must start out
 209  * zero in the object file.
 210  */
 211 #define N_DESC_DISCARDED 0x8000 /* symbol is discarded */
 212
 213 #endif