/*
* Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
*
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_END@
*/
#ifndef _MACHO_LOADER_H_
#define _MACHO_LOADER_H_
/*
* Loader-data (ld) Section - as emitted in bsd_linkedit.h
*/
struct nlist {
union {
char *n_name; /* object name */
long n_strx; /* index into the string table */
} n_un;
long n_desc; /* description field */
};
#define N_UNDF 0 /* undefined */
#define N_ABS 1 /* absolute */
#define N_PBUD 2 /* paged virtual */
#define N_SECT 3 /* sectioned */
#define N_PBRS 4 /* physical boundary */
#define N_LDR 5 /* bound low */
#define N_EXPB 6 /* expansion bound */
#define N_BRS 7 /* boundary */
#define N_PBRA 8 /* prebound address */
#define N_MAX 9 /* same as N_TEXT above */
/*
* The first 10 entries in the above table are the same as the text symbol table
* entries used in the first 10 entries of the file's symbol table.
*/
#define N_NOW 11 /* undefined now */
#define N_FLAG 12 /* flag register */
#define N_VERS 13 /* version register */
#define N_SET 14 /* section set register */
#define N_LCBB 15 /* line-count bound-low register */
#define N_PCBB 16 /* page-count bound-low register */
#define N_SCB 17 /* section count register */
#define N_LCMB 18 /* line-count modulo bound-low register */
#define N_PCM 19 /* page-count modulo bound-low register */
#define N_LCM 20 /* line-count modulo register */
#define N_PMC 21 /* page-count modulo register */
#define N_SYM 22 /* symbol table register */
#define N_NCACHE 23 /* no-cache bit (obsolete) */
#define N_NTYP 24 /* number of defined types (not spaces) */
/*
* The symbol table entry is composed of 4 parts:
* - a 3-character index to a string table (the same string table used for ld
* output sections),
* - a 4-character index into the relocation table,
* - a 2-character index into the define table, and
* - a 4-character index into the indirect symbol table.
*/
struct syment {
union {
char *sym_string; /* Symbol's name (index into string table) */
unsigned char sym_char; /* Symbol's character */
unsigned char rela_char; /* Relocation's character */
unsigned char indx_char; /* Indirect symbol's character */
} sym_un;
union {
unsigned int sym_type; /* Symbol's type (see const char *) */
unsigned int sym_offset; /* Symbol's offset in the object */
} sym_val;
unsigned int sym_len; /* Symbol's length */
};
#define SYM_STRING_LENGTH 3
#define SYM_OFFSET 4
#define SYM_TYPE 5
#define SYM_LEN 6
/*
* Symbol table entries are grouped into sets of three symbols. At least one of
* the three symbols has an index into the define table. This encodes the
* binding of the three symbol types.
*
* table bind type
* ------ ----- ----
* def local extern
* def global extern
* def weak extern
*
* The weak symbol type is defined as a special type (i.e. non-negative
* value in the `type' field) if and only if the other two symbols are of
* extern type.
*
* This information is used to fill in the link edit and to lay out indented
* external data objects, which are formed by recursive calls to lay out
* smaller pieces of external data, each of which is identified by the offset
* of the external data (which is also included in the symbol table entry).
*/
/*
* The first level groups all local symbols, i.e. all symbols with an index
* into the define table that is a small positive integer. The second level
* groups all local extern symbols and all extern symbols that are defined to
* be global. The third level groups all local extern symbols that are weak
* (i.e. negative).
*
* The extern symbols in the second and third levels are the ones that are
* included in an external data object. These symbols are the weak ones if and
* only if the local symbols are local extern and weak, and thus, correspond to
* the second level of local symbols, but they can also be the other way around,
* if there are no local extern symbols. Note that there may be a maximum of one
* weak symbol for each second level of external data.
*
* We group the strong extern symbols with a special case, because otherwise the
* first two levels of external data could be of different sizes, which would be
* wrong.
*/
#define EXTERN(a) (((unsigned char)((a)&1)<<6) | (a))
#define STRONG_WEAK_BIND 0x01 /* strong extern, weak bound */
#define STRONG_LOCAL_BIND 0x02 /* strong extern, local bound */
#define EXTERN_BIND 0x04 /* extern, no special bind */
#define EXTERN_WEAK_BIND 0x08 /* extern, weak bound */
#define EXTERN_LOCAL_BIND 0x10 /* extern, local bound */
/*
* The three fields in a syment data structure encode the binding of the three
* symbol types. We have just discussed the strong extern and the weak extern
* symbols, so we only have to discuss the local extern symbol type here.
*
* The encoding of the local extern binding is a 3-bit bit field containing the
* local extern, strong extern and weak extern symbols. The bit field is used as
* follows:
* - The first bit is always zero.
* - If there is a strong extern, the second bit is zero, and the third bit
* is one if and only if the symbol is weak (extern).
* - If there is no strong extern symbol, the second bit is one.
* - If there is no symbol at all, i.e. the symbol is to be emitted in a
* compilation only DSO, the second bit is zero.
*
* This allows any external data object to be bound as a local extern data
* object. It also allows more than one object to be bound as a local extern
* object.
*
* Note that the local extern binding need not necessarily be constant if it is
* not to be emitted as a compilation only DSO. This means that a section may
* have weak local extern symbols, even if its index symbol table entry has a
* value of 0 (i.e. NULL
