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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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