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1.1 root 1: #ifndef _MACHO_NLIST_H_
2: #define _MACHO_NLIST_H_
3: /*
4: * Copyright (c) 1980 Regents of the University of California.
5: * All rights reserved. The Berkeley software License Agreement
6: * specifies the terms and conditions for redistribution.
7: *
8: * @(#)nlist.h 5.1 (Berkeley) 5/30/85
9: */
10:
11: /*
12: * Format of a symbol table entry of a Mach-O file. Modified from the 4.3BSD
13: * format. The modifications from the original format were changing n_other
14: * (an unused field) to n_sect and the addition of the N_SECT type. These
15: * modifications are required to support symbols in an arbitrary number of
16: * sections not just the three sections (text, data and bss) in a 4.3BSD file.
17: */
18: struct nlist {
19: union {
20: char *n_name; /* for use when in-core */
21: long n_strx; /* index into the string table */
22: } n_un;
23: unsigned char n_type; /* type flag, see below */
24: unsigned char n_sect; /* section number or NO_SECT */
25: short n_desc; /* see <mach-o/stab.h> */
26: unsigned long n_value; /* value of this symbol (or stab offset) */
27: };
28:
29: /*
30: * Symbols with a index into the string table of zero (n_un.n_strx == 0) are
31: * defined to have a null, "", name. Therefore all string indexes to non null
32: * names must not have a zero string index. This is bit historical information
33: * that has never been well documented.
34: */
35:
36: /*
37: * The n_type field really contains three fields:
38: * unsigned char N_STAB:3,
39: * N_PEXT:1,
40: * N_TYPE:3,
41: * N_EXT:1;
42: * which are used via the following masks.
43: */
44: #define N_STAB 0xe0 /* if any of these bits set, a symbolic debugging entry */
45: #define N_PEXT 0x10 /* private external symbol bit */
46: #define N_TYPE 0x0e /* mask for the type bits */
47: #define N_EXT 0x01 /* external symbol bit, set for external symbols */
48:
49: /*
50: * Only symbolic debugging entries have some of the N_STAB bits set and if any
51: * of these bits are set then it is a symbolic debugging entry (a stab). In
52: * which case then the values of the n_type field (the entire field) are given
53: * in <mach-o/stab.h>
54: */
55:
56: /*
57: * Values for N_TYPE bits of the n_type field.
58: */
59: #define N_UNDF 0x0 /* undefined, n_sect == NO_SECT */
60: #define N_ABS 0x2 /* absolute, n_sect == NO_SECT */
61: #define N_SECT 0xe /* defined in section number n_sect */
62: #define N_INDR 0xa /* indirect */
63:
64: /*
65: * If the type is N_INDR then the symbol is defined to be the same as another
66: * symbol. In this case the n_value field is an index into the string table
67: * of the other symbol's name. When the other symbol is defined then they both
68: * take on the defined type and value.
69: */
70:
71: /*
72: * If the type is N_SECT then the n_sect field contains an ordinal of the
73: * section the symbol is defined in. The sections are numbered from 1 and
74: * refer to sections in order they appear in the load commands for the file
75: * they are in. This means the same ordinal may very well refer to different
76: * sections in different files.
77: *
78: * The n_value field for all symbol table entries (including N_STAB's) gets
79: * updated by the link editor based on the value of it's n_sect field and where
80: * the section n_sect references gets relocated. If the value of the n_sect
81: * field is NO_SECT then it's n_value field is not changed by the link editor.
82: */
83: #define NO_SECT 0 /* symbol is not in any section */
84: #define MAX_SECT 255 /* 1 thru 255 inclusive */
85:
86: /*
87: * Common symbols are represented by undefined (N_UNDF) external (N_EXT) types
88: * who's values (n_value) are non-zero. In which case the value of the n_value
89: * field is the size (in bytes) of the common symbol. The n_sect field is set
90: * to NO_SECT.
91: */
92:
93: /*
94: * To support the lazy binding of undefined symbols in the dynamic link-editor,
95: * the undefined symbols in the symbol table (the nlist structures) are marked
96: * with the indication if the undefined reference is a lazy reference or
97: * non-lazy reference. If both a non-lazy reference and a lazy reference is
98: * made to the same symbol the non-lazy reference takes precedence. A reference
99: * is lazy only when all references to that symbol are made through a symbol
100: * pointer in a lazy symbol pointer section.
101: *
102: * The implementation of marking nlist structures in the symbol table for
103: * undefined symbols will be to use some of the bits of the n_desc field as a
104: * reference type. The mask REFERENCE_TYPE will be applied to the n_desc field
105: * of an nlist structure for an undefined symbol to determine the type of
106: * undefined reference (lazy or non-lazy).
107: *
108: * The constants for the REFERENCE FLAGS are propagated to the reference table
109: * in a shared library file. In that case the constant for a defined symbol,
110: * REFERENCE_FLAG_DEFINED, is also used.
111: */
112: /* Reference type bits of the n_desc field of undefined symbols */
113: #define REFERENCE_TYPE 0xff
114: /* types of references */
115: #define REFERENCE_FLAG_UNDEFINED_NON_LAZY 0
116: #define REFERENCE_FLAG_UNDEFINED_LAZY 1
117: #define REFERENCE_FLAG_DEFINED 2
118: #define REFERENCE_FLAG_PRIVATE_DEFINED 3
119: #define REFERENCE_FLAG_PRIVATE_UNDEFINED_NON_LAZY 4
120: #define REFERENCE_FLAG_PRIVATE_UNDEFINED_LAZY 5
121:
122: #ifndef __STRICT_BSD__
123: /*
124: * The function nlist(3) from the C library.
125: */
126: extern int nlist (const char *filename, struct nlist *list);
127: #endif __STRICT_BSD__
128:
129: #endif _MACHO_LIST_H_
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