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C/C++ Source or Header | 2001-09-14 | 41.3 KB | 895 lines

/* * Copyright (c) 1999 Apple Computer, Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * Portions Copyright (c) 1999 Apple Computer, Inc. All Rights * Reserved. 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 1.1 (the "License"). You may not use this file * except in compliance with the License. Please obtain a copy of the * License at http://www.apple.com/publicsource 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 OR NON- INFRINGEMENT. Please see the * License for the specific language governing rights and limitations * under the License. * * @APPLE_LICENSE_HEADER_END@ */ #ifndef _MACHO_LOADER_H_ #define _MACHO_LOADER_H_ /* * This file describes the format of mach object files. */ /* * <mach/machine.h> is needed here for the cpu_type_t and cpu_subtype_t types * and contains the constants for the possible values of these types. */ #import <mach/machine.h> /* * <mach/vm_prot.h> is needed here for the vm_prot_t type and contains the * constants that are or'ed together for the possible values of this type. */ #import <mach/vm_prot.h> /* * <machine/thread_status.h> is expected to define the flavors of the thread * states and the structures of those flavors for each machine. */ #import <mach/machine/thread_status.h> #import <architecture/byte_order.h> /* * The mach header appears at the very beginning of the object file. */ struct mach_header { unsigned long magic; /* mach magic number identifier */ cpu_type_t cputype; /* cpu specifier */ cpu_subtype_t cpusubtype; /* machine specifier */ unsigned long filetype; /* type of file */ unsigned long ncmds; /* number of load commands */ unsigned long sizeofcmds; /* the size of all the load commands */ unsigned long flags; /* flags */ }; /* Constant for the magic field of the mach_header */ #define MH_MAGIC 0xfeedface /* the mach magic number */ #define MH_CIGAM NXSwapInt(MH_MAGIC) /* * The layout of the file depends on the filetype. For all but the MH_OBJECT * file type the segments are padded out and aligned on a segment alignment * boundary for efficient demand pageing. The MH_EXECUTE, MH_FVMLIB, MH_DYLIB, * MH_DYLINKER and MH_BUNDLE file types also have the headers included as part * of their first segment. * * The file type MH_OBJECT is a compact format intended as output of the * assembler and input (and possibly output) of the link editor (the .o * format). All sections are in one unnamed segment with no segment padding. * This format is used as an executable format when the file is so small the * segment padding greatly increases its size. * * The file type MH_PRELOAD is an executable format intended for things that * are not executed under the kernel (proms, stand alones, kernels, etc). The * format can be executed under the kernel but may demand paged it and not * preload it before execution. * * A core file is in MH_CORE format and can be any in an arbritray legal * Mach-O file. * * Constants for the filetype field of the mach_header */ #define MH_OBJECT 0x1 /* relocatable object file */ #define MH_EXECUTE 0x2 /* demand paged executable file */ #define MH_FVMLIB 0x3 /* fixed VM shared library file */ #define MH_CORE 0x4 /* core file */ #define MH_PRELOAD 0x5 /* preloaded executable file */ #define MH_DYLIB 0x6 /* dynamicly bound shared library file*/ #define MH_DYLINKER 0x7 /* dynamic link editor */ #define MH_BUNDLE 0x8 /* dynamicly bound bundle file */ /* Constants for the flags field of the mach_header */ #define MH_NOUNDEFS 0x1 /* the object file has no undefined references, can be executed */ #define MH_INCRLINK 0x2 /* the object file is the output of an incremental link against a base file and can't be link edited again */ #define MH_DYLDLINK 0x4 /* the object file is input for the dynamic linker and can't be staticly link edited again */ #define MH_BINDATLOAD 0x8 /* the object file's undefined references are bound by the dynamic linker when loaded. */ #define MH_PREBOUND 0x10 /* the file has its dynamic undefined references prebound. */ #define MH_SPLIT_SEGS 0x20 /* the file has its read-only and read-write segments split */ #define MH_LAZY_INIT 0x40 /* the shared library init routine is to be run lazily via catching memory faults to its writeable segments */ #define MH_TWOLEVEL 0x80 /* the image is using two-level name space bindings */ #define MH_FORCE_FLAT 0x100 /* the executable is forcing all images to use flat name space bindings */ #define MH_NOMULTIDEFS 0x200 /* this umbrella guarantees no multiple defintions of symbols in its sub-images so the two-level namespace hints can alwasys be used. */ /* * The load commands directly follow the mach_header. The total size of all * of the commands is given by the sizeofcmds field in the mach_header. All * load commands must have as their first two fields cmd and cmdsize. The cmd * field is filled in with a constant for that command type. Each command type * has a structure specifically for it. The cmdsize field is the size in bytes * of the particular load command structure plus anything that follows it that * is a part of the load command (i.e. section structures, strings, etc.). To * advance to the next load command the cmdsize can be added to the offset or * pointer of the current load command. The cmdsize MUST be a multiple of * sizeof(long) (this is forever the maximum alignment of any load commands). * The padded bytes must be zero. All tables in the object file must also * follow these rules so the file can be memory mapped. Otherwise the pointers * to these tables will not work well or at all on some machines. With all * padding zeroed like objects will compare byte for byte. */ struct load_command { unsigned long cmd; /* type of load command */ unsigned long cmdsize; /* total size of command in bytes */ }; /* * After MacOS X 10.1 when a new load command is added that is required to be * understood by the dynamic linker for the image to execute properly the * LC_REQ_DYLD bit will be or'ed into the load command constant. If the dynamic * linker sees such a load command it it does not understand will issue a * "unknown load command required for execution" error and refuse to use the * image. Other load commands without this bit that are not understood will * simply be ignored. */ #define LC_REQ_DYLD 0x80000000 /* Constants for the cmd field of all load commands, the type */ #define LC_SEGMENT 0x1 /* segment of this file to be mapped */ #define LC_SYMTAB 0x2 /* link-edit stab symbol table info */ #define LC_SYMSEG 0x3 /* link-edit gdb symbol table info (obsolete) */ #define LC_THREAD 0x4 /* thread */ #define LC_UNIXTHREAD 0x5 /* unix thread (includes a stack) */ #define LC_LOADFVMLIB 0x6 /* load a specified fixed VM shared library */ #define LC_IDFVMLIB 0x7 /* fixed VM shared library identification */ #define LC_IDENT 0x8 /* object identification info (obsolete) */ #define LC_FVMFILE 0x9 /* fixed VM file inclusion (internal use) */ #define LC_PREPAGE 0xa /* prepage command (internal use) */ #define LC_DYSYMTAB 0xb /* dynamic link-edit symbol table info */ #define LC_LOAD_DYLIB 0xc /* load a dynamicly linked shared library */ #define LC_ID_DYLIB 0xd /* dynamicly linked shared lib identification */ #define LC_LOAD_DYLINKER 0xe /* load a dynamic linker */ #define LC_ID_DYLINKER 0xf /* dynamic linker identification */ #define LC_PREBOUND_DYLIB 0x10 /* modules prebound for a dynamicly */ /* linked shared library */ #define LC_ROUTINES 0x11 /* image routines */ #define LC_SUB_FRAMEWORK 0x12 /* sub framework */ #define LC_SUB_UMBRELLA 0x13 /* sub umbrella */ #define LC_SUB_CLIENT 0x14 /* sub client */ #define LC_SUB_LIBRARY 0x15 /* sub library */ #define LC_TWOLEVEL_HINTS 0x16 /* two-level namespace lookup hints */ /* * A variable length string in a load command is represented by an lc_str * union. The strings are stored just after the load command structure and * the offset is from the start of the load command structure. The size * of the string is reflected in the cmdsize field of the load command. * Once again any padded bytes to bring the cmdsize field to a multiple * of sizeof(long) must be zero. */ union lc_str { unsigned long offset; /* offset to the string */ char *ptr; /* pointer to the string */ }; /* * The segment load command indicates that a part of this file is to be * mapped into the task's address space. The size of this segment in memory, * vmsize, maybe equal to or larger than the amount to map from this file, * filesize. The file is mapped starting at fileoff to the beginning of * the segment in memory, vmaddr. The rest of the memory of the segment, * if any, is allocated zero fill on demand. The segment's maximum virtual * memory protection and initial virtual memory protection are specified * by the maxprot and initprot fields. If the segment has sections then the * section structures directly follow the segment command and their size is * reflected in cmdsize. */ struct segment_command { unsigned long cmd; /* LC_SEGMENT */ unsigned long cmdsize; /* includes sizeof section structs */ char segname[16]; /* segment name */ unsigned long vmaddr; /* memory address of this segment */ unsigned long vmsize; /* memory size of this segment */ unsigned long fileoff; /* file offset of this segment */ unsigned long filesize; /* amount to map from the file */ vm_prot_t maxprot; /* maximum VM protection */ vm_prot_t initprot; /* initial VM protection */ unsigned long nsects; /* number of sections in segment */ unsigned long flags; /* flags */ }; /* Constants for the flags field of the segment_command */ #define SG_HIGHVM 0x1 /* the file contents for this segment is for the high part of the VM space, the low part is zero filled (for stacks in core files) */ #define SG_FVMLIB 0x2 /* this segment is the VM that is allocated by a fixed VM library, for overlap checking in the link editor */ #define SG_NORELOC 0x4 /* this segment has nothing that was relocated in it and nothing relocated to it, that is it maybe safely replaced without relocation*/ /* * A segment is made up of zero or more sections. Non-MH_OBJECT files have * all of their segments with the proper sections in each, and padded to the * specified segment alignment when produced by the link editor. The first * segment of a MH_EXECUTE and MH_FVMLIB format file contains the mach_header * and load commands of the object file before its first section. The zero * fill sections are always last in their segment (in all formats). This * allows the zeroed segment padding to be mapped into memory where zero fill * sections might be. * * The MH_OBJECT format has all of its sections in one segment for * compactness. There is no padding to a specified segment boundary and the * mach_header and load commands are not part of the segment. * * Sections with the same section name, sectname, going into the same segment, * segname, are combined by the link editor. The resulting section is aligned * to the maximum alignment of the combined sections and is the new section's * alignment. The combined sections are aligned to their original alignment in * the combined section. Any padded bytes to get the specified alignment are * zeroed. * * The format of the relocation entries referenced by the reloff and nreloc * fields of the section structure for mach object files is described in the * header file <reloc.h>. */ struct section { char sectname[16]; /* name of this section */ char segname[16]; /* segment this section goes in */ unsigned long addr; /* memory address of this section */ unsigned long size; /* size in bytes of this section */ unsigned long offset; /* file offset of this section */ unsigned long align; /* section alignment (power of 2) */ unsigned long reloff; /* file offset of relocation entries */ unsigned long nreloc; /* number of relocation entries */ unsigned long flags; /* flags (section type and attributes)*/ unsigned long reserved1; /* reserved */ unsigned long reserved2; /* reserved */ }; /* * The flags field of a section structure is separated into two parts a section * type and section attributes. The section types are mutually exclusive (it * can only have one type) but the section attributes are not (it may have more * than one attribute). */ #define SECTION_TYPE 0x000000ff /* 256 section types */ #define SECTION_ATTRIBUTES 0xffffff00 /* 24 section attributes */ /* Constants for the type of a section */ #define S_REGULAR 0x0 /* regular section */ #define S_ZEROFILL 0x1 /* zero fill on demand section */ #define S_CSTRING_LITERALS 0x2 /* section with only literal C strings*/ #define S_4BYTE_LITERALS 0x3 /* section with only 4 byte literals */ #define S_8BYTE_LITERALS 0x4 /* section with only 8 byte literals */ #define S_LITERAL_POINTERS 0x5 /* section with only pointers to */ /* literals */ /* * For the two types of symbol pointers sections and the symbol stubs section * they have indirect symbol table entries. For each of the entries in the * section the indirect symbol table entries, in corresponding order in the * indirect symbol table, start at the index stored in the reserved1 field * of the section structure. Since the indirect symbol table entries * correspond to the entries in the section the number of indirect symbol table * entries is inferred from the size of the section divided by the size of the * entries in the section. For symbol pointers sections the size of the entries * in the section is 4 bytes and for symbol stubs sections the byte size of the * stubs is stored in the reserved2 field of the section structure. */ #define S_NON_LAZY_SYMBOL_POINTERS 0x6 /* section with only non-lazy symbol pointers */ #define S_LAZY_SYMBOL_POINTERS 0x7 /* section with only lazy symbol pointers */ #define S_SYMBOL_STUBS 0x8 /* section with only symbol stubs, byte size of stub in the reserved2 field */ #define S_MOD_INIT_FUNC_POINTERS 0x9 /* section with only function pointers for initialization*/ #define S_MOD_TERM_FUNC_POINTERS 0xa /* section with only function pointers for termination */ #define S_COALESCED 0xb /* section contains symbols that are to be coalesced */ /* * Constants for the section attributes part of the flags field of a section * structure. */ #define SECTION_ATTRIBUTES_USR 0xff000000 /* User setable attributes */ #define S_ATTR_PURE_INSTRUCTIONS 0x80000000 /* section contains only true machine instructions */ #define S_ATTR_NO_TOC 0x40000000 /* section contains coalesced symbols that are not to be in a ranlib table of contents */ #define SECTION_ATTRIBUTES_SYS 0x00ffff00 /* system setable attributes */ #define S_ATTR_SOME_INSTRUCTIONS 0x00000400 /* section contains some machine instructions */ #define S_ATTR_EXT_RELOC 0x00000200 /* section has external relocation entries */ #define S_ATTR_LOC_RELOC 0x00000100 /* section has local relocation entries */ /* * The names of segments and sections in them are mostly meaningless to the * link-editor. But there are few things to support traditional UNIX * executables that require the link-editor and assembler to use some names * agreed upon by convention. * * The initial protection of the "__TEXT" segment has write protection turned * off (not writeable). * * The link-editor will allocate common symbols at the end of the "__common" * section in the "__DATA" segment. It will create the section and segment * if needed. */ /* The currently known segment names and the section names in those segments */ #define SEG_PAGEZERO "__PAGEZERO" /* the pagezero segment which has no */ /* protections and catches NULL */ /* references for MH_EXECUTE files */ #define SEG_TEXT "__TEXT" /* the tradition UNIX text segment */ #define SECT_TEXT "__text" /* the real text part of the text */ /* section no headers, and no padding */ #define SECT_FVMLIB_INIT0 "__fvmlib_init0" /* the fvmlib initialization */ /* section */ #define SECT_FVMLIB_INIT1 "__fvmlib_init1" /* the section following the */ /* fvmlib initialization */ /* section */ #define SEG_DATA "__DATA" /* the tradition UNIX data segment */ #define SECT_DATA "__data" /* the real initialized data section */ /* no padding, no bss overlap */ #define SECT_BSS "__bss" /* the real uninitialized data section*/ /* no padding */ #define SECT_COMMON "__common" /* the section common symbols are */ /* allocated in by the link editor */ #define SEG_OBJC "__OBJC" /* objective-C runtime segment */ #define SECT_OBJC_SYMBOLS "__symbol_table" /* symbol table */ #define SECT_OBJC_MODULES "__module_info" /* module information */ #define SECT_OBJC_STRINGS "__selector_strs" /* string table */ #define SECT_OBJC_REFS "__selector_refs" /* string table */ #define SEG_ICON "__ICON" /* the icon segment */ #define SECT_ICON_HEADER "__header" /* the icon headers */ #define SECT_ICON_TIFF "__tiff" /* the icons in tiff format */ #define SEG_LINKEDIT "__LINKEDIT" /* the segment containing all structs */ /* created and maintained by the link */ /* editor. Created with -seglinkedit */ /* option to ld(1) for MH_EXECUTE and */ /* FVMLIB file types only */ #define SEG_UNIXSTACK "__UNIXSTACK" /* the unix stack segment */ /* * Fixed virtual memory shared libraries are identified by two things. The * target pathname (the name of the library as found for execution), and the * minor version number. The address of where the headers are loaded is in * header_addr. */ struct fvmlib { union lc_str name; /* library's target pathname */ unsigned long minor_version; /* library's minor version number */ unsigned long header_addr; /* library's header address */ }; /* * A fixed virtual shared library (filetype == MH_FVMLIB in the mach header) * contains a fvmlib_command (cmd == LC_IDFVMLIB) to identify the library. * An object that uses a fixed virtual shared library also contains a * fvmlib_command (cmd == LC_LOADFVMLIB) for each library it uses. */ struct fvmlib_command { unsigned long cmd; /* LC_IDFVMLIB or LC_LOADFVMLIB */ unsigned long cmdsize; /* includes pathname string */ struct fvmlib fvmlib; /* the library identification */ }; /* * Dynamicly linked shared libraries are identified by two things. The * pathname (the name of the library as found for execution), and the * compatibility version number. The pathname must match and the compatibility * number in the user of the library must be greater than or equal to the * library being used. The time stamp is used to record the time a library was * built and copied into user so it can be use to determined if the library used * at runtime is exactly the same as used to built the program. */ struct dylib { union lc_str name; /* library's path name */ unsigned long timestamp; /* library's build time stamp */ unsigned long current_version; /* library's current version number */ unsigned long compatibility_version;/* library's compatibility vers number*/ }; /* * A dynamicly linked shared library (filetype == MH_DYLIB in the mach header) * contains a dylib_command (cmd == LC_ID_DYLIB) to identify the library. * An object that uses a dynamicly linked shared library also contains a * dylib_command (cmd == LC_LOAD_DYLIB) for each library it uses. */ struct dylib_command { unsigned long cmd; /* LC_ID_DYLIB or LC_LOAD_DYLIB */ unsigned long cmdsize; /* includes pathname string */ struct dylib dylib; /* the library identification */ }; /* * A dynamically linked shared library may be a subframework of an umbrella * framework. If so it will be linked with "-umbrella umbrella_name" where * Where "umbrella_name" is the name of the umbrella framework. A subframework * can only be linked against by its umbrella framework or other subframeworks * that are part of the same umbrella framework. Otherwise the static link * editor produces an error and states to link against the umbrella framework. * The name of the umbrella framework for subframeworks is recorded in the * following structure. */ struct sub_framework_command { unsigned long cmd; /* LC_SUB_FRAMEWORK */ unsigned long cmdsize; /* includes umbrella string */ union lc_str umbrella; /* the umbrella framework name */ }; /* * For dynamically linked shared libraries that are subframework of an umbrella * framework they can allow clients other than the umbrella framework or other * subframeworks in the same umbrella framework. To do this the subframework * is built with "-allowable_client client_name" and an LC_SUB_CLIENT load * command is created for each -allowable_client flag. The client_name is * usually a framework name. It can also be a name used for bundles clients * where the bundle is built with "-client_name client_name". */ struct sub_client_command { unsigned long cmd; /* LC_SUB_CLIENT */ unsigned long cmdsize; /* includes client string */ union lc_str client; /* the client name */ }; /* * A dynamically linked shared library may be a sub_umbrella of an umbrella * framework. If so it will be linked with "-sub_umbrella umbrella_name" where * Where "umbrella_name" is the name of the sub_umbrella framework. When * staticly linking when -twolevel_namespace is in effect a twolevel namespace * umbrella framework will only cause its subframeworks and those frameworks * listed as sub_umbrella frameworks to be implicited linked in. Any other * dependent dynamic libraries will not be linked it when -twolevel_namespace * is in effect. The primary library recorded by the static linker when * resolving a symbol in these libraries will be the umbrella framework. * Zero or more sub_umbrella frameworks may be use by an umbrella framework. * The name of a sub_umbrella framework is recorded in the following structure. */ struct sub_umbrella_command { unsigned long cmd; /* LC_SUB_UMBRELLA */ unsigned long cmdsize; /* includes sub_umbrella string */ union lc_str sub_umbrella; /* the sub_umbrella framework name */ }; /* * A dynamically linked shared library may be a sub_library of another shared * library. If so it will be linked with "-sub_library library_name" where * Where "library_name" is the name of the sub_library shared library. When * staticly linking when -twolevel_namespace is in effect a twolevel namespace * shared library will only cause its subframeworks and those frameworks * listed as sub_umbrella frameworks and libraries listed as sub_libraries to * be implicited linked in. Any other dependent dynamic libraries will not be * linked it when -twolevel_namespace is in effect. The primary library * recorded by the static linker when resolving a symbol in these libraries * will be the umbrella framework (or dynamic library). Zero or more sub_library * shared libraries may be use by an umbrella framework or (or dynamic library). * The name of a sub_library framework is recorded in the following structure. * For example /usr/lib/libobjc_profile.A.dylib would be recorded as "libobjc". */ struct sub_library_command { unsigned long cmd; /* LC_SUB_LIBRARY */ unsigned long cmdsize; /* includes sub_library string */ union lc_str sub_library; /* the sub_library name */ }; /* * A program (filetype == MH_EXECUTE) or bundle (filetype == MH_BUNDLE) that is * prebound to its dynamic libraries has one of these for each library that * the static linker used in prebinding. It contains a bit vector for the * modules in the library. The bits indicate which modules are bound (1) and * which are not (0) from the library. The bit for module 0 is the low bit * of the first byte. So the bit for the Nth module is: * (linked_modules[N/8] >> N%8) & 1 */ struct prebound_dylib_command { unsigned long cmd; /* LC_PREBOUND_DYLIB */ unsigned long cmdsize; /* includes strings */ union lc_str name; /* library's path name */ unsigned long nmodules; /* number of modules in library */ union lc_str linked_modules; /* bit vector of linked modules */ }; /* * A program that uses a dynamic linker contains a dylinker_command to identify * the name of the dynamic linker (LC_LOAD_DYLINKER). And a dynamic linker * contains a dylinker_command to identify the dynamic linker (LC_ID_DYLINKER). * A file can have at most one of these. */ struct dylinker_command { unsigned long cmd; /* LC_ID_DYLINKER or LC_LOAD_DYLINKER */ unsigned long cmdsize; /* includes pathname string */ union lc_str name; /* dynamic linker's path name */ }; /* * Thread commands contain machine-specific data structures suitable for * use in the thread state primitives. The machine specific data structures * follow the struct thread_command as follows. * Each flavor of machine specific data structure is preceded by an unsigned * long constant for the flavor of that data structure, an unsigned long * that is the count of longs of the size of the state data structure and then * the state data structure follows. This triple may be repeated for many * flavors. The constants for the flavors, counts and state data structure * definitions are expected to be in the header file <machine/thread_status.h>. * These machine specific data structures sizes must be multiples of * sizeof(long). The cmdsize reflects the total size of the thread_command * and all of the sizes of the constants for the flavors, counts and state * data structures. * * For executable objects that are unix processes there will be one * thread_command (cmd == LC_UNIXTHREAD) created for it by the link-editor. * This is the same as a LC_THREAD, except that a stack is automatically * created (based on the shell's limit for the stack size). Command arguments * and environment variables are copied onto that stack. */ struct thread_command { unsigned long cmd; /* LC_THREAD or LC_UNIXTHREAD */ unsigned long cmdsize; /* total size of this command */ /* unsigned long flavor flavor of thread state */ /* unsigned long count count of longs in thread state */ /* struct XXX_thread_state state thread state for this flavor */ /* ... */ }; /* * The routines command contains the address of the dynamic shared library * initialization routine and an index into the module table for the module * that defines the routine. Before any modules are used from the library the * dynamic linker fully binds the module that defines the initialization routine * and then calls it. This gets called before any module initialization * routines (used for C++ static constructors) in the library. */ struct routines_command { unsigned long cmd; /* LC_ROUTINES */ unsigned long cmdsize; /* total size of this command */ unsigned long init_address; /* address of initialization routine */ unsigned long init_module; /* index into the module table that */ /* the init routine is defined in */ unsigned long reserved1; unsigned long reserved2; unsigned long reserved3; unsigned long reserved4; unsigned long reserved5; unsigned long reserved6; }; /* * The symtab_command contains the offsets and sizes of the link-edit 4.3BSD * "stab" style symbol table information as described in the header files * <nlist.h> and <stab.h>. */ struct symtab_command { unsigned long cmd; /* LC_SYMTAB */ unsigned long cmdsize; /* sizeof(struct symtab_command) */ unsigned long symoff; /* symbol table offset */ unsigned long nsyms; /* number of symbol table entries */ unsigned long stroff; /* string table offset */ unsigned long strsize; /* string table size in bytes */ }; /* * This is the second set of the symbolic information which is used to support * the data structures for the dynamicly link editor. * * The original set of symbolic information in the symtab_command which contains * the symbol and string tables must also be present when this load command is * present. When this load command is present the symbol table is organized * into three groups of symbols: * local symbols (static and debugging symbols) - grouped by module * defined external symbols - grouped by module (sorted by name if not lib) * undefined external symbols (sorted by name if MH_BINDATLOAD is not set) * In this load command there are offsets and counts to each of the three groups * of symbols. * * This load command contains a the offsets and sizes of the following new * symbolic information tables: * table of contents * module table * reference symbol table * indirect symbol table * The first three tables above (the table of contents, module table and * reference symbol table) are only present if the file is a dynamicly linked * shared library. For executable and object modules, which are files * containing only one module, the information that would be in these three * tables is determined as follows: * table of contents - the defined external symbols are sorted by name * module table - the file contains only one module so everything in the * file is part of the module. * reference symbol table - is the defined and undefined external symbols * * For dynamicly linked shared library files this load command also contains * offsets and sizes to the pool of relocation entries for all sections * separated into two groups: * external relocation entries * local relocation entries * For executable and object modules the relocation entries continue to hang * off the section structures. */ struct dysymtab_command { unsigned long cmd; /* LC_DYSYMTAB */ unsigned long cmdsize; /* sizeof(struct dysymtab_command) */ /* * The symbols indicated by symoff and nsyms of the LC_SYMTAB load command * are grouped into the following three groups: * local symbols (further grouped by the module they are from) * defined external symbols (further grouped by the module they are from) * undefined symbols * * The local symbols are used only for debugging. The dynamic binding * process may have to use them to indicate to the debugger the local * symbols for a module that is being bound. * * The last two groups are used by the dynamic binding process to do the * binding (indirectly through the module table and the reference symbol * table when this is a dynamicly linked shared library file). */ unsigned long ilocalsym; /* index to local symbols */ unsigned long nlocalsym; /* number of local symbols */ unsigned long iextdefsym; /* index to externally defined symbols */ unsigned long nextdefsym; /* number of externally defined symbols */ unsigned long iundefsym; /* index to undefined symbols */ unsigned long nundefsym; /* number of undefined symbols */ /* * For the for the dynamic binding process to find which module a symbol * is defined in the table of contents is used (analogous to the ranlib * structure in an archive) which maps defined external symbols to modules * they are defined in. This exists only in a dynamicly linked shared * library file. For executable and object modules the defined external * symbols are sorted by name and is use as the table of contents. */ unsigned long tocoff; /* file offset to table of contents */ unsigned long ntoc; /* number of entries in table of contents */ /* * To support dynamic binding of "modules" (whole object files) the symbol * table must reflect the modules that the file was created from. This is * done by having a module table that has indexes and counts into the merged * tables for each module. The module structure that these two entries * refer to is described below. This exists only in a dynamicly linked * shared library file. For executable and object modules the file only * contains one module so everything in the file belongs to the module. */ unsigned long modtaboff; /* file offset to module table */ unsigned long nmodtab; /* number of module table entries */ /* * To support dynamic module binding the module structure for each module * indicates the external references (defined and undefined) each module * makes. For each module there is an offset and a count into the * reference symbol table for the symbols that the module references. * This exists only in a dynamicly linked shared library file. For * executable and object modules the defined external symbols and the * undefined external symbols indicates the external references. */ unsigned long extrefsymoff; /* offset to referenced symbol table */ unsigned long nextrefsyms; /* number of referenced symbol table entries */ /* * The sections that contain "symbol pointers" and "routine stubs" have * indexes and (implied counts based on the size of the section and fixed * size of the entry) into the "indirect symbol" table for each pointer * and stub. For every section of these two types the index into the * indirect symbol table is stored in the section header in the field * reserved1. An indirect symbol table entry is simply a 32bit index into * the symbol table to the symbol that the pointer or stub is referring to. * The indirect symbol table is ordered to match the entries in the section. */ unsigned long indirectsymoff; /* file offset to the indirect symbol table */ unsigned long nindirectsyms; /* number of indirect symbol table entries */ /* * To support relocating an individual module in a library file quickly the * external relocation entries for each module in the library need to be * accessed efficiently. Since the relocation entries can't be accessed * through the section headers for a library file they are separated into * groups of local and external entries further grouped by module. In this * case the presents of this load command who's extreloff, nextrel, * locreloff and nlocrel fields are non-zero indicates that the relocation * entries of non-merged sections are not referenced through the section * structures (and the reloff and nreloc fields in the section headers are * set to zero). * * Since the relocation entries are not accessed through the section headers * this requires the r_address field to be something other than a section * offset to identify the item to be relocated. In this case r_address is * set to the offset from the vmaddr of the first LC_SEGMENT command. * For MH_SPLIT_SEGS images r_address is set to the the offset from the * vmaddr of the first read-write LC_SEGMENT command. * * The relocation entries are grouped by module and the module table * entries have indexes and counts into them for the group of external * relocation entries for that the module. * * For sections that are merged across modules there must not be any * remaining external relocation entries for them (for merged sections * remaining relocation entries must be local). */ unsigned long extreloff; /* offset to external relocation entries */ unsigned long nextrel; /* number of external relocation entries */ /* * All the local relocation entries are grouped together (they are not * grouped by their module since they are only used if the object is moved * from it staticly link edited address). */ unsigned long locreloff; /* offset to local relocation entries */ unsigned long nlocrel; /* number of local relocation entries */ }; /* * An indirect symbol table entry is simply a 32bit index into the symbol table * to the symbol that the pointer or stub is refering to. Unless it is for a * non-lazy symbol pointer section for a defined symbol which strip(1) as * removed. In which case it has the value INDIRECT_SYMBOL_LOCAL. If the * symbol was also absolute INDIRECT_SYMBOL_ABS is or'ed with that. */ #define INDIRECT_SYMBOL_LOCAL 0x80000000 #define INDIRECT_SYMBOL_ABS 0x40000000 /* a table of contents entry */ struct dylib_table_of_contents { unsigned long symbol_index; /* the defined external symbol (index into the symbol table) */ unsigned long module_index; /* index into the module table this symbol is defined in */ }; /* a module table entry */ struct dylib_module { unsigned long module_name; /* the module name (index into string table) */ unsigned long iextdefsym; /* index into externally defined symbols */ unsigned long nextdefsym; /* number of externally defined symbols */ unsigned long irefsym; /* index into reference symbol table */ unsigned long nrefsym; /* number of reference symbol table entries */ unsigned long ilocalsym; /* index into symbols for local symbols */ unsigned long nlocalsym; /* number of local symbols */ unsigned long iextrel; /* index into external relocation entries */ unsigned long nextrel; /* number of external relocation entries */ unsigned long iinit_iterm; /* low 16 bits are the index into the init section, high 16 bits are the index into the term section */ unsigned long ninit_nterm; /* low 16 bits are the number of init section entries, high 16 bits are the number of term section entries */ unsigned long /* for this module address of the start of */ objc_module_info_addr; /* the (__OBJC,__module_info) section */ unsigned long /* for this module size of */ objc_module_info_size; /* the (__OBJC,__module_info) section */ }; /* * The entries in the reference symbol table are used when loading the module * (both by the static and dynamic link editors) and if the module is unloaded * or replaced. Therefore all external symbols (defined and undefined) are * listed in the module's reference table. The flags describe the type of * reference that is being made. The constants for the flags are defined in * <mach-o/nlist.h> as they are also used for symbol table entries. */ struct dylib_reference { unsigned long isym:24, /* index into the symbol table */ flags:8; /* flags to indicate the type of reference */ }; /* * The twolevel_hints_command contains the offset and number of hints in the * two-level namespace lookup hints table. */ struct twolevel_hints_command { unsigned long cmd; /* LC_TWOLEVEL_HINTS */ unsigned long cmdsize; /* sizeof(struct twolevel_hints_command) */ unsigned long offset; /* offset to the hint table */ unsigned long nhints; /* number of hints in the hint table */ }; /* * The entries in the two-level namespace lookup hints table are twolevel_hint * structs. These provide hints to the dynamic link editor where to start * looking for an undefined symbol in a two-level namespace image. The * isub_image field is an index into the sub-images (sub-frameworks and * sub-umbrellas list) that made up the two-level image that the undefined * symbol was found in when it was built by the static link editor. If * isub-image is 0 the the symbol is expected to be defined in library and not * in the sub-images. If isub-image is non-zero it is an index into the array * of sub-images for the umbrella with the first index in the sub-images being * 1. The array of sub-images is the ordered list of sub-images of the umbrella * that would be searched for a symbol that has the umbrella recorded as its * primary library. The table of contents index is an index into the * library's table of contents. This is used as the starting point of the * binary search or a directed linear search. */ struct twolevel_hint { unsigned long isub_image:8, /* index into the sub images */ itoc:24; /* index into the table of contents */ }; /* * The symseg_command contains the offset and size of the GNU style * symbol table information as described in the header file <symseg.h>. * The symbol roots of the symbol segments must also be aligned properly * in the file. So the requirement of keeping the offsets aligned to a * multiple of a sizeof(long) translates to the length field of the symbol * roots also being a multiple of a long. Also the padding must again be * zeroed. (THIS IS OBSOLETE and no longer supported). */ struct symseg_command { unsigned long cmd; /* LC_SYMSEG */ unsigned long cmdsize; /* sizeof(struct symseg_command) */ unsigned long offset; /* symbol segment offset */ unsigned long size; /* symbol segment size in bytes */ }; /* * The ident_command contains a free format string table following the * ident_command structure. The strings are null terminated and the size of * the command is padded out with zero bytes to a multiple of sizeof(long). * (THIS IS OBSOLETE and no longer supported). */ struct ident_command { unsigned long cmd; /* LC_IDENT */ unsigned long cmdsize; /* strings that follow this command */ }; /* * The fvmfile_command contains a reference to a file to be loaded at the * specified virtual address. (Presently, this command is reserved for * internal use. The kernel ignores this command when loading a program into * memory). */ struct fvmfile_command { unsigned long cmd; /* LC_FVMFILE */ unsigned long cmdsize; /* includes pathname string */ union lc_str name; /* files pathname */ unsigned long header_addr; /* files virtual address */ }; #endif _MACHO_LOADER_H_