EXTERNAL_HEADERS/mach-o/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_ */