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