nlist.h
1 /* 2 * Copyright (c) 1999-2003 Apple Computer, Inc. All Rights Reserved. 3 * 4 * @APPLE_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. Please obtain a copy of the License at 10 * http://www.opensource.apple.com/apsl/ and read it before using this 11 * file. 12 * 13 * The Original Code and all software distributed under the License are 14 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 15 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 16 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 17 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 18 * Please see the License for the specific language governing rights and 19 * limitations under the License. 20 * 21 * @APPLE_LICENSE_HEADER_END@ 22 */ 23 #ifndef _MACHO_NLIST_H_ 24 #define _MACHO_NLIST_H_ 25 /* $NetBSD: nlist.h,v 1.5 1994/10/26 00:56:11 cgd Exp $ */ 26 27 /*- 28 * Copyright (c) 1991, 1993 29 * The Regents of the University of California. All rights reserved. 30 * (c) UNIX System Laboratories, Inc. 31 * All or some portions of this file are derived from material licensed 32 * to the University of California by American Telephone and Telegraph 33 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 34 * the permission of UNIX System Laboratories, Inc. 35 * 36 * Redistribution and use in source and binary forms, with or without 37 * modification, are permitted provided that the following conditions 38 * are met: 39 * 1. Redistributions of source code must retain the above copyright 40 * notice, this list of conditions and the following disclaimer. 41 * 2. Redistributions in binary form must reproduce the above copyright 42 * notice, this list of conditions and the following disclaimer in the 43 * documentation and/or other materials provided with the distribution. 44 * 3. All advertising materials mentioning features or use of this software 45 * must display the following acknowledgement: 46 * This product includes software developed by the University of 47 * California, Berkeley and its contributors. 48 * 4. Neither the name of the University nor the names of its contributors 49 * may be used to endorse or promote products derived from this software 50 * without specific prior written permission. 51 * 52 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 53 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 54 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 55 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 56 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 57 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 58 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 59 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 60 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 61 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 62 * SUCH DAMAGE. 63 * 64 * @(#)nlist.h 8.2 (Berkeley) 1/21/94 65 */ 66 #include <stdint.h> 67 68 /* 69 * Format of a symbol table entry of a Mach-O file for 32-bit architectures. 70 * Modified from the BSD format. The modifications from the original format 71 * were changing n_other (an unused field) to n_sect and the addition of the 72 * N_SECT type. These modifications are required to support symbols in a larger 73 * number of sections not just the three sections (text, data and bss) in a BSD 74 * file. 75 */ 76 struct nlist { 77 union { 78 #ifndef __LP64__ 79 char *n_name; /* for use when in-core */ 80 #endif 81 uint32_t n_strx; /* index into the string table */ 82 } n_un; 83 uint8_t n_type; /* type flag, see below */ 84 uint8_t n_sect; /* section number or NO_SECT */ 85 int16_t n_desc; /* see <mach-o/stab.h> */ 86 uint32_t n_value; /* value of this symbol (or stab offset) */ 87 }; 88 89 /* 90 * This is the symbol table entry structure for 64-bit architectures. 91 */ 92 struct nlist_64 { 93 union { 94 uint32_t n_strx; /* index into the string table */ 95 } n_un; 96 uint8_t n_type; /* type flag, see below */ 97 uint8_t n_sect; /* section number or NO_SECT */ 98 uint16_t n_desc; /* see <mach-o/stab.h> */ 99 uint64_t n_value; /* value of this symbol (or stab offset) */ 100 }; 101 102 /* 103 * Symbols with a index into the string table of zero (n_un.n_strx == 0) are 104 * defined to have a null, "", name. Therefore all string indexes to non null 105 * names must not have a zero string index. This is bit historical information 106 * that has never been well documented. 107 */ 108 109 /* 110 * The n_type field really contains four fields: 111 * unsigned char N_STAB:3, 112 * N_PEXT:1, 113 * N_TYPE:3, 114 * N_EXT:1; 115 * which are used via the following masks. 116 */ 117 #define N_STAB 0xe0 /* if any of these bits set, a symbolic debugging entry */ 118 #define N_PEXT 0x10 /* private external symbol bit */ 119 #define N_TYPE 0x0e /* mask for the type bits */ 120 #define N_EXT 0x01 /* external symbol bit, set for external symbols */ 121 122 /* 123 * Only symbolic debugging entries have some of the N_STAB bits set and if any 124 * of these bits are set then it is a symbolic debugging entry (a stab). In 125 * which case then the values of the n_type field (the entire field) are given 126 * in <mach-o/stab.h> 127 */ 128 129 /* 130 * Values for N_TYPE bits of the n_type field. 131 */ 132 #define N_UNDF 0x0 /* undefined, n_sect == NO_SECT */ 133 #define N_ABS 0x2 /* absolute, n_sect == NO_SECT */ 134 #define N_SECT 0xe /* defined in section number n_sect */ 135 #define N_PBUD 0xc /* prebound undefined (defined in a dylib) */ 136 #define N_INDR 0xa /* indirect */ 137 138 /* 139 * If the type is N_INDR then the symbol is defined to be the same as another 140 * symbol. In this case the n_value field is an index into the string table 141 * of the other symbol's name. When the other symbol is defined then they both 142 * take on the defined type and value. 143 */ 144 145 /* 146 * If the type is N_SECT then the n_sect field contains an ordinal of the 147 * section the symbol is defined in. The sections are numbered from 1 and 148 * refer to sections in order they appear in the load commands for the file 149 * they are in. This means the same ordinal may very well refer to different 150 * sections in different files. 151 * 152 * The n_value field for all symbol table entries (including N_STAB's) gets 153 * updated by the link editor based on the value of it's n_sect field and where 154 * the section n_sect references gets relocated. If the value of the n_sect 155 * field is NO_SECT then it's n_value field is not changed by the link editor. 156 */ 157 #define NO_SECT 0 /* symbol is not in any section */ 158 #define MAX_SECT 255 /* 1 thru 255 inclusive */ 159 160 /* 161 * Common symbols are represented by undefined (N_UNDF) external (N_EXT) types 162 * who's values (n_value) are non-zero. In which case the value of the n_value 163 * field is the size (in bytes) of the common symbol. The n_sect field is set 164 * to NO_SECT. The alignment of a common symbol may be set as a power of 2 165 * between 2^1 and 2^15 as part of the n_desc field using the macros below. If 166 * the alignment is not set (a value of zero) then natural alignment based on 167 * the size is used. 168 */ 169 #define GET_COMM_ALIGN(n_desc) (((n_desc) >> 8) & 0x0f) 170 #define SET_COMM_ALIGN(n_desc,align) \ 171 (n_desc) = (((n_desc) & 0xf0ff) | (((align) & 0x0f) << 8)) 172 173 /* 174 * To support the lazy binding of undefined symbols in the dynamic link-editor, 175 * the undefined symbols in the symbol table (the nlist structures) are marked 176 * with the indication if the undefined reference is a lazy reference or 177 * non-lazy reference. If both a non-lazy reference and a lazy reference is 178 * made to the same symbol the non-lazy reference takes precedence. A reference 179 * is lazy only when all references to that symbol are made through a symbol 180 * pointer in a lazy symbol pointer section. 181 * 182 * The implementation of marking nlist structures in the symbol table for 183 * undefined symbols will be to use some of the bits of the n_desc field as a 184 * reference type. The mask REFERENCE_TYPE will be applied to the n_desc field 185 * of an nlist structure for an undefined symbol to determine the type of 186 * undefined reference (lazy or non-lazy). 187 * 188 * The constants for the REFERENCE FLAGS are propagated to the reference table 189 * in a shared library file. In that case the constant for a defined symbol, 190 * REFERENCE_FLAG_DEFINED, is also used. 191 */ 192 /* Reference type bits of the n_desc field of undefined symbols */ 193 #define REFERENCE_TYPE 0x7 194 /* types of references */ 195 #define REFERENCE_FLAG_UNDEFINED_NON_LAZY 0 196 #define REFERENCE_FLAG_UNDEFINED_LAZY 1 197 #define REFERENCE_FLAG_DEFINED 2 198 #define REFERENCE_FLAG_PRIVATE_DEFINED 3 199 #define REFERENCE_FLAG_PRIVATE_UNDEFINED_NON_LAZY 4 200 #define REFERENCE_FLAG_PRIVATE_UNDEFINED_LAZY 5 201 202 /* 203 * To simplify stripping of objects that use are used with the dynamic link 204 * editor, the static link editor marks the symbols defined an object that are 205 * referenced by a dynamicly bound object (dynamic shared libraries, bundles). 206 * With this marking strip knows not to strip these symbols. 207 */ 208 #define REFERENCED_DYNAMICALLY 0x0010 209 210 /* 211 * For images created by the static link editor with the -twolevel_namespace 212 * option in effect the flags field of the mach header is marked with 213 * MH_TWOLEVEL. And the binding of the undefined references of the image are 214 * determined by the static link editor. Which library an undefined symbol is 215 * bound to is recorded by the static linker in the high 8 bits of the n_desc 216 * field using the SET_LIBRARY_ORDINAL macro below. The ordinal recorded 217 * references the libraries listed in the Mach-O's LC_LOAD_DYLIB, 218 * LC_LOAD_WEAK_DYLIB, LC_REEXPORT_DYLIB, LC_LOAD_UPWARD_DYLIB, and 219 * LC_LAZY_LOAD_DYLIB, etc. load commands in the order they appear in the 220 * headers. The library ordinals start from 1. 221 * For a dynamic library that is built as a two-level namespace image the 222 * undefined references from module defined in another use the same nlist struct 223 * an in that case SELF_LIBRARY_ORDINAL is used as the library ordinal. For 224 * defined symbols in all images they also must have the library ordinal set to 225 * SELF_LIBRARY_ORDINAL. The EXECUTABLE_ORDINAL refers to the executable 226 * image for references from plugins that refer to the executable that loads 227 * them. 228 * 229 * The DYNAMIC_LOOKUP_ORDINAL is for undefined symbols in a two-level namespace 230 * image that are looked up by the dynamic linker with flat namespace semantics. 231 * This ordinal was added as a feature in Mac OS X 10.3 by reducing the 232 * value of MAX_LIBRARY_ORDINAL by one. So it is legal for existing binaries 233 * or binaries built with older tools to have 0xfe (254) dynamic libraries. In 234 * this case the ordinal value 0xfe (254) must be treated as a library ordinal 235 * for compatibility. 236 */ 237 #define GET_LIBRARY_ORDINAL(n_desc) (((n_desc) >> 8) & 0xff) 238 #define SET_LIBRARY_ORDINAL(n_desc,ordinal) \ 239 (n_desc) = (((n_desc) & 0x00ff) | (((ordinal) & 0xff) << 8)) 240 #define SELF_LIBRARY_ORDINAL 0x0 241 #define MAX_LIBRARY_ORDINAL 0xfd 242 #define DYNAMIC_LOOKUP_ORDINAL 0xfe 243 #define EXECUTABLE_ORDINAL 0xff 244 245 /* 246 * The bit 0x0020 of the n_desc field is used for two non-overlapping purposes 247 * and has two different symbolic names, N_NO_DEAD_STRIP and N_DESC_DISCARDED. 248 */ 249 250 /* 251 * The N_NO_DEAD_STRIP bit of the n_desc field only ever appears in a 252 * relocatable .o file (MH_OBJECT filetype). And is used to indicate to the 253 * static link editor it is never to dead strip the symbol. 254 */ 255 #define N_NO_DEAD_STRIP 0x0020 /* symbol is not to be dead stripped */ 256 257 /* 258 * The N_DESC_DISCARDED bit of the n_desc field never appears in linked image. 259 * But is used in very rare cases by the dynamic link editor to mark an in 260 * memory symbol as discared and longer used for linking. 261 */ 262 #define N_DESC_DISCARDED 0x0020 /* symbol is discarded */ 263 264 /* 265 * The N_WEAK_REF bit of the n_desc field indicates to the dynamic linker that 266 * the undefined symbol is allowed to be missing and is to have the address of 267 * zero when missing. 268 */ 269 #define N_WEAK_REF 0x0040 /* symbol is weak referenced */ 270 271 /* 272 * The N_WEAK_DEF bit of the n_desc field indicates to the static and dynamic 273 * linkers that the symbol definition is weak, allowing a non-weak symbol to 274 * also be used which causes the weak definition to be discared. Currently this 275 * is only supported for symbols in coalesed sections. 276 */ 277 #define N_WEAK_DEF 0x0080 /* coalesed symbol is a weak definition */ 278 279 /* 280 * The N_REF_TO_WEAK bit of the n_desc field indicates to the dynamic linker 281 * that the undefined symbol should be resolved using flat namespace searching. 282 */ 283 #define N_REF_TO_WEAK 0x0080 /* reference to a weak symbol */ 284 285 /* 286 * The N_ARM_THUMB_DEF bit of the n_desc field indicates that the symbol is 287 * a defintion of a Thumb function. 288 */ 289 #define N_ARM_THUMB_DEF 0x0008 /* symbol is a Thumb function (ARM) */ 290 291 /* 292 * The N_SYMBOL_RESOLVER bit of the n_desc field indicates that the 293 * that the function is actually a resolver function and should 294 * be called to get the address of the real function to use. 295 * This bit is only available in .o files (MH_OBJECT filetype) 296 */ 297 #define N_SYMBOL_RESOLVER 0x0100 298 299 /* 300 * The N_ALT_ENTRY bit of the n_desc field indicates that the 301 * symbol is pinned to the previous content. 302 */ 303 #define N_ALT_ENTRY 0x0200 304 305 #ifndef __STRICT_BSD__ 306 #ifdef __cplusplus 307 extern "C" { 308 #endif /* __cplusplus */ 309 /* 310 * The function nlist(3) from the C library. 311 */ 312 extern int nlist (const char *filename, struct nlist *list); 313 #ifdef __cplusplus 314 } 315 #endif /* __cplusplus */ 316 #endif /* __STRICT_BSD__ */ 317 318 #endif /* _MACHO_LIST_H_ */