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1.1 root 1: /*
2: * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
3: *
4: * @APPLE_LICENSE_HEADER_START@
5: *
6: * The contents of this file constitute Original Code as defined in and
7: * are subject to the Apple Public Source License Version 1.1 (the
8: * "License"). You may not use this file except in compliance with the
9: * License. Please obtain a copy of the License at
10: * http://www.apple.com/publicsource and read it before using this file.
11: *
12: * This Original Code and all software distributed under the License are
13: * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
14: * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
15: * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
16: * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
17: * License for the specific language governing rights and limitations
18: * under the License.
19: *
20: * @APPLE_LICENSE_HEADER_END@
21: */
22: #ifndef _MACHO_LOADER_H_
23: #define _MACHO_LOADER_H_
24:
25: /*
26: * This file describes the format of mach object files.
27: */
28:
29: /*
30: * <mach/machine.h> is needed here for the cpu_type_t and cpu_subtype_t types
31: * and contains the constants for the possible values of these types.
32: */
33: #include <mach/machine.h>
34:
35: /*
36: * <mach/vm_prot.h> is needed here for the vm_prot_t type and contains the
37: * constants that are or'ed together for the possible values of this type.
38: */
39: #include <mach/vm_prot.h>
40:
41: /*
42: * <machine/thread_status.h> is expected to define the flavors of the thread
43: * states and the structures of those flavors for each machine.
44: */
45: #include <mach/machine/thread_status.h>
46:
47: /*
48: * The mach header appears at the very beginning of the object file.
49: */
50: struct mach_header {
51: unsigned long magic; /* mach magic number identifier */
52: cpu_type_t cputype; /* cpu specifier */
53: cpu_subtype_t cpusubtype; /* machine specifier */
54: unsigned long filetype; /* type of file */
55: unsigned long ncmds; /* number of load commands */
56: unsigned long sizeofcmds; /* the size of all the load commands */
57: unsigned long flags; /* flags */
58: };
59:
60: /* Constant for the magic field of the mach_header */
61: #define MH_MAGIC 0xfeedface /* the mach magic number */
62: #define MH_CIGAM NXSwapInt(MH_MAGIC)
63:
64: /*
65: * The layout of the file depends on the filetype. For all but the MH_OBJECT
66: * file type the segments are padded out and aligned on a segment alignment
67: * boundary for efficient demand pageing. The MH_EXECUTE, MH_FVMLIB, MH_DYLIB,
68: * MH_DYLINKER and MH_BUNDLE file types also have the headers included as part
69: * of their first segment.
70: *
71: * The file type MH_OBJECT is a compact format intended as output of the
72: * assembler and input (and possibly output) of the link editor (the .o
73: * format). All sections are in one unnamed segment with no segment padding.
74: * This format is used as an executable format when the file is so small the
75: * segment padding greatly increases it's size.
76: *
77: * The file type MH_PRELOAD is an executable format intended for things that
78: * not executed under the kernel (proms, stand alones, kernels, etc). The
79: * format can be executed under the kernel but may demand paged it and not
80: * preload it before execution.
81: *
82: * A core file is in MH_CORE format and can be any in an arbritray legal
83: * Mach-O file.
84: *
85: * Constants for the filetype field of the mach_header
86: */
87: #define MH_OBJECT 0x1 /* relocatable object file */
88: #define MH_EXECUTE 0x2 /* demand paged executable file */
89: #define MH_FVMLIB 0x3 /* fixed VM shared library file */
90: #define MH_CORE 0x4 /* core file */
91: #define MH_PRELOAD 0x5 /* preloaded executable file */
92: #define MH_DYLIB 0x6 /* dynamicly bound shared library file*/
93: #define MH_DYLINKER 0x7 /* dynamic link editor */
94: #define MH_BUNDLE 0x8 /* dynamicly bound bundle file */
95:
96: /* Constants for the flags field of the mach_header */
97: #define MH_NOUNDEFS 0x1 /* the object file has no undefined
98: references, can be executed */
99: #define MH_INCRLINK 0x2 /* the object file is the output of an
100: incremental link against a base file
101: and can't be link edited again */
102: #define MH_DYLDLINK 0x4 /* the object file is input for the
103: dynamic linker and can't be staticly
104: link edited again */
105: #define MH_BINDATLOAD 0x8 /* the object file's undefined
106: references are bound by the dynamic
107: linker when loaded. */
108: #define MH_PREBOUND 0x10 /* the file has it's dynamic undefined
109: references prebound. */
110:
111: /*
112: * The load commands directly follow the mach_header. The total size of all
113: * of the commands is given by the sizeofcmds field in the mach_header. All
114: * load commands must have as their first two fields cmd and cmdsize. The cmd
115: * field is filled in with a constant for that command type. Each command type
116: * has a structure specifically for it. The cmdsize field is the size in bytes
117: * of the particular load command structure plus anything that follows it that
118: * is a part of the load command (i.e. section structures, strings, etc.). To
119: * advance to the next load command the cmdsize can be added to the offset or
120: * pointer of the current load command. The cmdsize MUST be a multiple of
121: * sizeof(long) (this is forever the maximum alignment of any load commands).
122: * The padded bytes must be zero. All tables in the object file must also
123: * follow these rules so the file can be memory mapped. Otherwise the pointers
124: * to these tables will not work well or at all on some machines. With all
125: * padding zeroed like objects will compare byte for byte.
126: */
127: struct load_command {
128: unsigned long cmd; /* type of load command */
129: unsigned long cmdsize; /* total size of command in bytes */
130: };
131:
132: /* Constants for the cmd field of all load commands, the type */
133: #define LC_SEGMENT 0x1 /* segment of this file to be mapped */
134: #define LC_SYMTAB 0x2 /* link-edit stab symbol table info */
135: #define LC_SYMSEG 0x3 /* link-edit gdb symbol table info (obsolete) */
136: #define LC_THREAD 0x4 /* thread */
137: #define LC_UNIXTHREAD 0x5 /* unix thread (includes a stack) */
138: #define LC_LOADFVMLIB 0x6 /* load a specified fixed VM shared library */
139: #define LC_IDFVMLIB 0x7 /* fixed VM shared library identification */
140: #define LC_IDENT 0x8 /* object identification info (obsolete) */
141: #define LC_FVMFILE 0x9 /* fixed VM file inclusion (internal use) */
142: #define LC_PREPAGE 0xa /* prepage command (internal use) */
143: #define LC_DYSYMTAB 0xb /* dynamic link-edit symbol table info */
144: #define LC_LOAD_DYLIB 0xc /* load a dynamicly linked shared library */
145: #define LC_ID_DYLIB 0xd /* dynamicly linked shared lib identification */
146: #define LC_LOAD_DYLINKER 0xe /* load a dynamic linker */
147: #define LC_ID_DYLINKER 0xf /* dynamic linker identification */
148: #define LC_PREBOUND_DYLIB 0x10 /* modules prebound for a dynamicly */
149: /* linked shared library */
150:
151: /*
152: * A variable length string in a load command is represented by an lc_str
153: * union. The strings are stored just after the load command structure and
154: * the offset is from the start of the load command structure. The size
155: * of the string is reflected in the cmdsize field of the load command.
156: * Once again any padded bytes to bring the cmdsize field to a multiple
157: * of sizeof(long) must be zero.
158: */
159: union lc_str {
160: unsigned long offset; /* offset to the string */
161: char *ptr; /* pointer to the string */
162: };
163:
164: /*
165: * The segment load command indicates that a part of this file is to be
166: * mapped into the task's address space. The size of this segment in memory,
167: * vmsize, maybe equal to or larger than the amount to map from this file,
168: * filesize. The file is mapped starting at fileoff to the beginning of
169: * the segment in memory, vmaddr. The rest of the memory of the segment,
170: * if any, is allocated zero fill on demand. The segment's maximum virtual
171: * memory protection and initial virtual memory protection are specified
172: * by the maxprot and initprot fields. If the segment has sections then the
173: * section structures directly follow the segment command and their size is
174: * reflected in cmdsize.
175: */
176: struct segment_command {
177: unsigned long cmd; /* LC_SEGMENT */
178: unsigned long cmdsize; /* includes sizeof section structs */
179: char segname[16]; /* segment name */
180: unsigned long vmaddr; /* memory address of this segment */
181: unsigned long vmsize; /* memory size of this segment */
182: unsigned long fileoff; /* file offset of this segment */
183: unsigned long filesize; /* amount to map from the file */
184: vm_prot_t maxprot; /* maximum VM protection */
185: vm_prot_t initprot; /* initial VM protection */
186: unsigned long nsects; /* number of sections in segment */
187: unsigned long flags; /* flags */
188: };
189:
190: /* Constants for the flags field of the segment_command */
191: #define SG_HIGHVM 0x1 /* the file contents for this segment is for
192: the high part of the VM space, the low part
193: is zero filled (for stacks in core files) */
194: #define SG_FVMLIB 0x2 /* this segment is the VM that is allocated by
195: a fixed VM library, for overlap checking in
196: the link editor */
197: #define SG_NORELOC 0x4 /* this segment has nothing that was relocated
198: in it and nothing relocated to it, that is
199: it maybe safely replaced without relocation*/
200:
201: /*
202: * A segment is made up of zero or more sections. Non-MH_OBJECT files have
203: * all of their segments with the proper sections in each, and padded to the
204: * specified segment alignment when produced by the link editor. The first
205: * segment of a MH_EXECUTE and MH_FVMLIB format file contains the mach_header
206: * and load commands of the object file before it's first section. The zero
207: * fill sections are always last in their segment (in all formats). This
208: * allows the zeroed segment padding to be mapped into memory where zero fill
209: * sections might be.
210: *
211: * The MH_OBJECT format has all of it's sections in one segment for
212: * compactness. There is no padding to a specified segment boundary and the
213: * mach_header and load commands are not part of the segment.
214: *
215: * Sections with the same section name, sectname, going into the same segment,
216: * segname, are combined by the link editor. The resulting section is aligned
217: * to the maximum alignment of the combined sections and is the new section's
218: * alignment. The combined sections are aligned to their original alignment in
219: * the combined section. Any padded bytes to get the specified alignment are
220: * zeroed.
221: *
222: * The format of the relocation entries referenced by the reloff and nreloc
223: * fields of the section structure for mach object files is described in the
224: * header file <reloc.h>.
225: */
226: struct section {
227: char sectname[16]; /* name of this section */
228: char segname[16]; /* segment this section goes in */
229: unsigned long addr; /* memory address of this section */
230: unsigned long size; /* size in bytes of this section */
231: unsigned long offset; /* file offset of this section */
232: unsigned long align; /* section alignment (power of 2) */
233: unsigned long reloff; /* file offset of relocation entries */
234: unsigned long nreloc; /* number of relocation entries */
235: unsigned long flags; /* flags (section type and attributes)*/
236: unsigned long reserved1; /* reserved */
237: unsigned long reserved2; /* reserved */
238: };
239:
240: /*
241: * The flags field of a section structure is separated into two parts a section
242: * type and section attributes. The section types are mutually exclusive (it
243: * can only have one type) but the section attributes are not (it may have more
244: * than one attribute).
245: */
246: #define SECTION_TYPE 0x000000ff /* 256 section types */
247: #define SECTION_ATTRIBUTES 0xffffff00 /* 24 section attributes */
248:
249: /* Constants for the type of a section */
250: #define S_REGULAR 0x0 /* regular section */
251: #define S_ZEROFILL 0x1 /* zero fill on demand section */
252: #define S_CSTRING_LITERALS 0x2 /* section with only literal C strings*/
253: #define S_4BYTE_LITERALS 0x3 /* section with only 4 byte literals */
254: #define S_8BYTE_LITERALS 0x4 /* section with only 8 byte literals */
255: #define S_LITERAL_POINTERS 0x5 /* section with only pointers to */
256: /* literals */
257: /*
258: * For the two types of symbol pointers sections and the symbol stubs section
259: * they have indirect symbol table entries. For each of the entries in the
260: * section the indirect symbol table entries, in corresponding order in the
261: * indirect symbol table, start at the index stored in the reserved1 field
262: * of the section structure. Since the indirect symbol table entries
263: * correspond to the entries in the section the number of indirect symbol table
264: * entries is inferred from the size of the section divided by the size of the
265: * entries in the section. For symbol pointers sections the size of the entries
266: * in the section is 4 bytes and for symbol stubs sections the byte size of the
267: * stubs is stored in the reserved2 field of the section structure.
268: */
269: #define S_NON_LAZY_SYMBOL_POINTERS 0x6 /* section with only non-lazy
270: symbol pointers */
271: #define S_LAZY_SYMBOL_POINTERS 0x7 /* section with only lazy symbol
272: pointers */
273: #define S_SYMBOL_STUBS 0x8 /* section with only symbol
274: stubs, byte size of stub in
275: the reserved2 field */
276: #define S_MOD_INIT_FUNC_POINTERS 0x9 /* section with only function
277: pointers for initialization*/
278: /*
279: * Constants for the section attributes part of the flags field of a section
280: * structure.
281: */
282: #define SECTION_ATTRIBUTES_USR 0xff000000 /* User setable attributes */
283: #define S_ATTR_PURE_INSTRUCTIONS 0x80000000 /* section contains only true
284: machine instructions */
285: #define SECTION_ATTRIBUTES_SYS 0x00ffff00 /* system setable attributes */
286: #define S_ATTR_SOME_INSTRUCTIONS 0x00000400 /* section contains some
287: machine instructions */
288: #define S_ATTR_EXT_RELOC 0x00000200 /* section has external
289: relocation entries */
290: #define S_ATTR_LOC_RELOC 0x00000100 /* section has local
291: relocation entries */
292:
293:
294: /*
295: * The names of segments and sections in them are mostly meaningless to the
296: * link-editor. But there are few things to support traditional UNIX
297: * executables that require the link-editor and assembler to use some names
298: * agreed upon by convention.
299: *
300: * The initial protection of the "__TEXT" segment has write protection turned
301: * off (not writeable).
302: *
303: * The link-editor will allocate common symbols at the end of the "__common"
304: * section in the "__DATA" segment. It will create the section and segment
305: * if needed.
306: */
307:
308: /* The currently known segment names and the section names in those segments */
309:
310: #define SEG_PAGEZERO "__PAGEZERO" /* the pagezero segment which has no */
311: /* protections and catches NULL */
312: /* references for MH_EXECUTE files */
313:
314:
315: #define SEG_TEXT "__TEXT" /* the tradition UNIX text segment */
316: #define SECT_TEXT "__text" /* the real text part of the text */
317: /* section no headers, and no padding */
318: #define SECT_FVMLIB_INIT0 "__fvmlib_init0" /* the fvmlib initialization */
319: /* section */
320: #define SECT_FVMLIB_INIT1 "__fvmlib_init1" /* the section following the */
321: /* fvmlib initialization */
322: /* section */
323:
324: #define SEG_DATA "__DATA" /* the tradition UNIX data segment */
325: #define SECT_DATA "__data" /* the real initialized data section */
326: /* no padding, no bss overlap */
327: #define SECT_BSS "__bss" /* the real uninitialized data section*/
328: /* no padding */
329: #define SECT_COMMON "__common" /* the section common symbols are */
330: /* allocated in by the link editor */
331:
332: #define SEG_OBJC "__OBJC" /* objective-C runtime segment */
333: #define SECT_OBJC_SYMBOLS "__symbol_table" /* symbol table */
334: #define SECT_OBJC_MODULES "__module_info" /* module information */
335: #define SECT_OBJC_STRINGS "__selector_strs" /* string table */
336: #define SECT_OBJC_REFS "__selector_refs" /* string table */
337:
338: #define SEG_ICON "__ICON" /* the NeXT icon segment */
339: #define SECT_ICON_HEADER "__header" /* the icon headers */
340: #define SECT_ICON_TIFF "__tiff" /* the icons in tiff format */
341:
342: #define SEG_LINKEDIT "__LINKEDIT" /* the segment containing all structs */
343: /* created and maintained by the link */
344: /* editor. Created with -seglinkedit */
345: /* option to ld(1) for MH_EXECUTE and */
346: /* FVMLIB file types only */
347:
348: #define SEG_UNIXSTACK "__UNIXSTACK" /* the unix stack segment */
349:
350: /*
351: * Fixed virtual memory shared libraries are identified by two things. The
352: * target pathname (the name of the library as found for execution), and the
353: * minor version number. The address of where the headers are loaded is in
354: * header_addr.
355: */
356: struct fvmlib {
357: union lc_str name; /* library's target pathname */
358: unsigned long minor_version; /* library's minor version number */
359: unsigned long header_addr; /* library's header address */
360: };
361:
362: /*
363: * A fixed virtual shared library (filetype == MH_FVMLIB in the mach header)
364: * contains a fvmlib_command (cmd == LC_IDFVMLIB) to identify the library.
365: * An object that uses a fixed virtual shared library also contains a
366: * fvmlib_command (cmd == LC_LOADFVMLIB) for each library it uses.
367: */
368: struct fvmlib_command {
369: unsigned long cmd; /* LC_IDFVMLIB or LC_LOADFVMLIB */
370: unsigned long cmdsize; /* includes pathname string */
371: struct fvmlib fvmlib; /* the library identification */
372: };
373:
374: /*
375: * Dynamicly linked shared libraries are identified by two things. The
376: * pathname (the name of the library as found for execution), and the
377: * compatibility version number. The pathname must match and the compatibility
378: * number in the user of the library must be greater than or equal to the
379: * library being used. The time stamp is used to record the time a library was
380: * built and copied into user so it can be use to determined if the library used
381: * at runtime is exactly the same as used to built the program.
382: */
383: struct dylib {
384: union lc_str name; /* library's path name */
385: unsigned long timestamp; /* library's build time stamp */
386: unsigned long current_version; /* library's current version number */
387: unsigned long compatibility_version;/* library's compatibility vers number*/
388: };
389:
390: /*
391: * A dynamicly linked shared library (filetype == MH_DYLIB in the mach header)
392: * contains a dylib_command (cmd == LC_ID_DYLIB) to identify the library.
393: * An object that uses a dynamicly linked shared library also contains a
394: * dylib_command (cmd == LC_LOAD_DYLIB) for each library it uses.
395: */
396: struct dylib_command {
397: unsigned long cmd; /* LC_ID_DYLIB or LC_LOAD_DYLIB */
398: unsigned long cmdsize; /* includes pathname string */
399: struct dylib dylib; /* the library identification */
400: };
401:
402: /*
403: * A program (filetype == MH_EXECUTE) or bundle (filetype == MH_BUNDLE) that is
404: * prebound to it's dynamic libraries has one of these for each library that
405: * the static linker used in prebinding. It contains a bit vector for the
406: * modules in the library. The bits indicate which modules are bound (1) and
407: * which are not (0) from the library. The bit for module 0 is the low bit
408: * of the first byte. So the bit for the Nth module is:
409: * (linked_modules[N/8] >> N%8) & 1
410: */
411: struct prebound_dylib_command {
412: unsigned long cmd; /* LC_PREBOUND_DYLIB */
413: unsigned long cmdsize; /* includes strings */
414: union lc_str name; /* library's path name */
415: unsigned long nmodules; /* number of modules in library */
416: union lc_str linked_modules; /* bit vector of linked modules */
417: };
418:
419: /*
420: * A program that uses a dynamic linker contains a dylinker_command to identify
421: * the name of the dynamic linker (LC_LOAD_DYLINKER). And a dynamic linker
422: * contains a dylinker_command to identify the dynamic linker (LC_ID_DYLINKER).
423: * A file can have at most one of these.
424: */
425: struct dylinker_command {
426: unsigned long cmd; /* LC_ID_DYLINKER or LC_LOAD_DYLINKER */
427: unsigned long cmdsize; /* includes pathname string */
428: union lc_str name; /* dynamic linker's path name */
429: };
430:
431: /*
432: * Thread commands contain machine-specific data structures suitable for
433: * use in the thread state primitives. The machine specific data structures
434: * follow the struct thread_command as follows.
435: * Each flavor of machine specific data structure is preceded by an unsigned
436: * long constant for the flavor of that data structure, an unsigned long
437: * that is the count of longs of the size of the state data structure and then
438: * the state data structure follows. This triple may be repeated for many
439: * flavors. The constants for the flavors, counts and state data structure
440: * definitions are expected to be in the header file <machine/thread_status.h>.
441: * These machine specific data structures sizes must be multiples of
442: * sizeof(long). The cmdsize reflects the total size of the thread_command
443: * and all of the sizes of the constants for the flavors, counts and state
444: * data structures.
445: *
446: * For executable objects that are unix processes there will be one
447: * thread_command (cmd == LC_UNIXTHREAD) created for it by the link-editor.
448: * This is the same as a LC_THREAD, except that a stack is automatically
449: * created (based on the shell's limit for the stack size). Command arguments
450: * and environment variables are copied onto that stack.
451: */
452: struct thread_command {
453: unsigned long cmd; /* LC_THREAD or LC_UNIXTHREAD */
454: unsigned long cmdsize; /* total size of this command */
455: /* unsigned long flavor flavor of thread state */
456: /* unsigned long count count of longs in thread state */
457: /* struct XXX_thread_state state thread state for this flavor */
458: /* ... */
459: };
460:
461: /*
462: * The symtab_command contains the offsets and sizes of the link-edit 4.3BSD
463: * "stab" style symbol table information as described in the header files
464: * <nlist.h> and <stab.h>.
465: */
466: struct symtab_command {
467: unsigned long cmd; /* LC_SYMTAB */
468: unsigned long cmdsize; /* sizeof(struct symtab_command) */
469: unsigned long symoff; /* symbol table offset */
470: unsigned long nsyms; /* number of symbol table entries */
471: unsigned long stroff; /* string table offset */
472: unsigned long strsize; /* string table size in bytes */
473: };
474:
475: /*
476: * This is the second set of the symbolic information which is used to support
477: * the data structures for the dynamicly link editor.
478: *
479: * The original set of symbolic information in the symtab_command which contains
480: * the symbol and string tables must also be present when this load command is
481: * present. When this load command is present the symbol table is organized
482: * into three groups of symbols:
483: * local symbols (static and debugging symbols) - grouped by module
484: * defined external symbols - grouped by module (sorted by name if not lib)
485: * undefined external symbols (sorted by name)
486: * In this load command there are offsets and counts to each of the three groups
487: * of symbols.
488: *
489: * This load command contains a the offsets and sizes of the following new
490: * symbolic information tables:
491: * table of contents
492: * module table
493: * reference symbol table
494: * indirect symbol table
495: * The first three tables above (the table of contents, module table and
496: * reference symbol table) are only present if the file is a dynamicly linked
497: * shared library. For executable and object modules, which are files
498: * containing only one module, the information that would be in these three
499: * tables is determined as follows:
500: * table of contents - the defined external symbols are sorted by name
501: * module table - the file contains only one module so everything in the
502: * file is part of the module.
503: * reference symbol table - is the defined and undefined external symbols
504: *
505: * For dynamicly linked shared library files this load command also contains
506: * offsets and sizes to the pool of relocation entries for all sections
507: * separated into two groups:
508: * external relocation entries
509: * local relocation entries
510: * For executable and object modules the relocation entries continue to hang
511: * off the section structures.
512: */
513: struct dysymtab_command {
514: unsigned long cmd; /* LC_DYSYMTAB */
515: unsigned long cmdsize; /* sizeof(struct dysymtab_command) */
516:
517: /*
518: * The symbols indicated by symoff and nsyms of the LC_SYMTAB load command
519: * are grouped into the following three groups:
520: * local symbols (further grouped by the module they are from)
521: * defined external symbols (further grouped by the module they are from)
522: * undefined symbols
523: *
524: * The local symbols are used only for debugging. The dynamic binding
525: * process may have to use them to indicate to the debugger the local
526: * symbols for a module that is being bound.
527: *
528: * The last two groups are used by the dynamic binding process to do the
529: * binding (indirectly through the module table and the reference symbol
530: * table when this is a dynamicly linked shared library file).
531: */
532: unsigned long ilocalsym; /* index to local symbols */
533: unsigned long nlocalsym; /* number of local symbols */
534:
535: unsigned long iextdefsym; /* index to externally defined symbols */
536: unsigned long nextdefsym; /* number of externally defined symbols */
537:
538: unsigned long iundefsym; /* index to undefined symbols */
539: unsigned long nundefsym; /* number of undefined symbols */
540:
541: /*
542: * For the for the dynamic binding process to find which module a symbol
543: * is defined in the table of contents is used (analogous to the ranlib
544: * structure in an archive) which maps defined external symbols to modules
545: * they are defined in. This exists only in a dynamicly linked shared
546: * library file. For executable and object modules the defined external
547: * symbols are sorted by name and is use as the table of contents.
548: */
549: unsigned long tocoff; /* file offset to table of contents */
550: unsigned long ntoc; /* number of entries in table of contents */
551:
552: /*
553: * To support dynamic binding of "modules" (whole object files) the symbol
554: * table must reflect the modules that the file was created from. This is
555: * done by having a module table that has indexes and counts into the merged
556: * tables for each module. The module structure that these two entries
557: * refer to is described below. This exists only in a dynamicly linked
558: * shared library file. For executable and object modules the file only
559: * contains one module so everything in the file belongs to the module.
560: */
561: unsigned long modtaboff; /* file offset to module table */
562: unsigned long nmodtab; /* number of module table entries */
563:
564: /*
565: * To support dynamic module binding the module structure for each module
566: * indicates the external references (defined and undefined) each module
567: * makes. For each module there is an offset and a count into the
568: * reference symbol table for the symbols that the module references.
569: * This exists only in a dynamicly linked shared library file. For
570: * executable and object modules the defined external symbols and the
571: * undefined external symbols indicates the external references.
572: */
573: unsigned long extrefsymoff; /* offset to referenced symbol table */
574: unsigned long nextrefsyms; /* number of referenced symbol table entries */
575:
576: /*
577: * The sections that contain "symbol pointers" and "routine stubs" have
578: * indexes and (implied counts based on the size of the section and fixed
579: * size of the entry) into the "indirect symbol" table for each pointer
580: * and stub. For every section of these two types the index into the
581: * indirect symbol table is stored in the section header in the field
582: * reserved1. An indirect symbol table entry is simply a 32bit index into
583: * the symbol table to the symbol that the pointer or stub is referring to.
584: * The indirect symbol table is ordered to match the entries in the section.
585: */
586: unsigned long indirectsymoff; /* file offset to the indirect symbol table */
587: unsigned long nindirectsyms; /* number of indirect symbol table entries */
588:
589: /*
590: * To support relocating an individual module in a library file quickly the
591: * external relocation entries for each module in the library need to be
592: * accessed efficiently. Since the relocation entries can't be accessed
593: * through the section headers for a library file they are separated into
594: * groups of local and external entries further grouped by module. In this
595: * case the presents of this load command who's extreloff, nextrel,
596: * locreloff and nlocrel fields are non-zero indicates that the relocation
597: * entries of non-merged sections are not referenced through the section
598: * structures (and the reloff and nreloc fields in the section headers are
599: * set to zero).
600: *
601: * Since the relocation entries are not accessed through the section headers
602: * this requires the r_address field to be something other than a section
603: * offset to identify the item to be relocated. In this case r_address is
604: * set to the offset from the vmaddr of the first LC_SEGMENT command.
605: *
606: * The relocation entries are grouped by module and the module table
607: * entries have indexes and counts into them for the group of external
608: * relocation entries for that the module.
609: *
610: * For sections that are merged across modules there must not be any
611: * remaining external relocation entries for them (for merged sections
612: * remaining relocation entries must be local).
613: */
614: unsigned long extreloff; /* offset to external relocation entries */
615: unsigned long nextrel; /* number of external relocation entries */
616:
617: /*
618: * All the local relocation entries are grouped together (they are not
619: * grouped by their module since they are only used if the object is moved
620: * from it staticly link edited address).
621: */
622: unsigned long locreloff; /* offset to local relocation entries */
623: unsigned long nlocrel; /* number of local relocation entries */
624:
625: };
626:
627: /*
628: * An indirect symbol table entry is simply a 32bit index into the symbol table
629: * to the symbol that the pointer or stub is refering to. Unless it is for a
630: * non-lazy symbol pointer section for a defined symbol which strip(1) as
631: * removed. In which case it has the value INDIRECT_SYMBOL_LOCAL. If the
632: * symbol was also absolute INDIRECT_SYMBOL_ABS is or'ed with that.
633: */
634: #define INDIRECT_SYMBOL_LOCAL 0x80000000
635: #define INDIRECT_SYMBOL_ABS 0x40000000
636:
637:
638: /* a table of contents entry */
639: struct dylib_table_of_contents {
640: unsigned long symbol_index; /* the defined external symbol
641: (index into the symbol table) */
642: unsigned long module_index; /* index into the module table this symbol
643: is defined in */
644: };
645:
646: /* a module table entry */
647: struct dylib_module {
648: unsigned long module_name; /* the module name (index into string table) */
649:
650: unsigned long iextdefsym; /* index into externally defined symbols */
651: unsigned long nextdefsym; /* number of externally defined symbols */
652: unsigned long irefsym; /* index into reference symbol table */
653: unsigned long nrefsym; /* number of reference symbol table entries */
654: unsigned long ilocalsym; /* index into symbols for local symbols */
655: unsigned long nlocalsym; /* number of local symbols */
656:
657: unsigned long iextrel; /* index into external relocation entries */
658: unsigned long nextrel; /* number of external relocation entries */
659:
660: unsigned long iinit; /* index into the init section */
661: unsigned long ninit; /* number of init section entries */
662:
663: unsigned long /* for this module address of the start of */
664: objc_module_info_addr; /* the (__OBJC,__module_info) section */
665: unsigned long /* for this module size of */
666: objc_module_info_size; /* the (__OBJC,__module_info) section */
667: };
668:
669: /*
670: * The entries in the reference symbol table are used when loading the module
671: * (both by the static and dynamic link editors) and if the module is unloaded
672: * or replaced. Therefore all external symbols (defined and undefined) are
673: * listed in the module's reference table. The flags describe the type of
674: * reference that is being made. The constants for the flags are defined in
675: * <mach-o/nlist.h> as they are also used for symbol table entries.
676: */
677: struct dylib_reference {
678: unsigned long isym:24, /* index into the symbol table */
679: flags:8; /* flags to indicate the type of reference */
680: };
681:
682: /*
683: * The symseg_command contains the offset and size of the GNU style
684: * symbol table information as described in the header file <symseg.h>.
685: * The symbol roots of the symbol segments must also be aligned properly
686: * in the file. So the requirement of keeping the offsets aligned to a
687: * multiple of a sizeof(long) translates to the length field of the symbol
688: * roots also being a multiple of a long. Also the padding must again be
689: * zeroed. (THIS IS OBSOLETE and no longer supported).
690: */
691: struct symseg_command {
692: unsigned long cmd; /* LC_SYMSEG */
693: unsigned long cmdsize; /* sizeof(struct symseg_command) */
694: unsigned long offset; /* symbol segment offset */
695: unsigned long size; /* symbol segment size in bytes */
696: };
697:
698: /*
699: * The ident_command contains a free format string table following the
700: * ident_command structure. The strings are null terminated and the size of
701: * the command is padded out with zero bytes to a multiple of sizeof(long).
702: * (THIS IS OBSOLETE and no longer supported).
703: */
704: struct ident_command {
705: unsigned long cmd; /* LC_IDENT */
706: unsigned long cmdsize; /* strings that follow this command */
707: };
708:
709: /*
710: * The fvmfile_command contains a reference to a file to be loaded at the
711: * specified virtual address. (Presently, this command is reserved for NeXT
712: * internal use. The kernel ignores this command when loading a program into
713: * memory).
714: */
715: struct fvmfile_command {
716: unsigned long cmd; /* LC_FVMFILE */
717: unsigned long cmdsize; /* includes pathname string */
718: union lc_str name; /* files pathname */
719: unsigned long header_addr; /* files virtual address */
720: };
721:
722: #endif /*_MACHO_LOADER_H_*/
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