+/*
+ * The twolevel_hints_command contains the offset and number of hints in the
+ * two-level namespace lookup hints table.
+ */
+struct twolevel_hints_command {
+ uint32_t cmd; /* LC_TWOLEVEL_HINTS */
+ uint32_t cmdsize; /* sizeof(struct twolevel_hints_command) */
+ uint32_t offset; /* offset to the hint table */
+ uint32_t 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 {
+ uint32_t
+ isub_image:8, /* index into the sub images */
+ itoc:24; /* index into the table of contents */
+};
+
+/*
+ * The prebind_cksum_command contains the value of the original check sum for
+ * prebound files or zero. When a prebound file is first created or modified
+ * for other than updating its prebinding information the value of the check sum
+ * is set to zero. When the file has it prebinding re-done and if the value of
+ * the check sum is zero the original check sum is calculated and stored in
+ * cksum field of this load command in the output file. If when the prebinding
+ * is re-done and the cksum field is non-zero it is left unchanged from the
+ * input file.
+ */
+struct prebind_cksum_command {
+ uint32_t cmd; /* LC_PREBIND_CKSUM */
+ uint32_t cmdsize; /* sizeof(struct prebind_cksum_command) */
+ uint32_t cksum; /* the check sum or zero */
+};
+
+/*
+ * The uuid load command contains a single 128-bit unique random number that
+ * identifies an object produced by the static link editor.
+ */
+struct uuid_command {
+ uint32_t cmd; /* LC_UUID */
+ uint32_t cmdsize; /* sizeof(struct uuid_command) */
+ uint8_t uuid[16]; /* the 128-bit uuid */
+};
+
+/*
+ * The rpath_command contains a path which at runtime should be added to
+ * the current run path used to find @rpath prefixed dylibs.
+ */
+struct rpath_command {
+ uint32_t cmd; /* LC_RPATH */
+ uint32_t cmdsize; /* includes string */
+ union lc_str path; /* path to add to run path */
+};
+
+/*
+ * The linkedit_data_command contains the offsets and sizes of a blob
+ * of data in the __LINKEDIT segment.
+ */
+struct linkedit_data_command {
+ uint32_t cmd; /* LC_CODE_SIGNATURE, LC_SEGMENT_SPLIT_INFO,
+ LC_FUNCTION_STARTS, LC_DATA_IN_CODE,
+ or LC_DYLIB_CODE_SIGN_DRS */
+ uint32_t cmdsize; /* sizeof(struct linkedit_data_command) */
+ uint32_t dataoff; /* file offset of data in __LINKEDIT segment */
+ uint32_t datasize; /* file size of data in __LINKEDIT segment */
+};
+
+/*
+ * The encryption_info_command contains the file offset and size of an
+ * of an encrypted segment.
+ */
+struct encryption_info_command {
+ uint32_t cmd; /* LC_ENCRYPTION_INFO */
+ uint32_t cmdsize; /* sizeof(struct encryption_info_command) */
+ uint32_t cryptoff; /* file offset of encrypted range */
+ uint32_t cryptsize; /* file size of encrypted range */
+ uint32_t cryptid; /* which enryption system,
+ 0 means not-encrypted yet */
+};
+
+/*
+ * The encryption_info_command_64 contains the file offset and size of an
+ * of an encrypted segment (for use in 64-bit targets).
+ */
+struct encryption_info_command_64 {
+ uint32_t cmd; /* LC_ENCRYPTION_INFO_64 */
+ uint32_t cmdsize; /* sizeof(struct encryption_info_command_64) */
+ uint32_t cryptoff; /* file offset of encrypted range */
+ uint32_t cryptsize; /* file size of encrypted range */
+ uint32_t cryptid; /* which enryption system,
+ 0 means not-encrypted yet */
+ uint32_t pad; /* padding to make this struct's size a multiple
+ of 8 bytes */
+};
+
+/*
+ * The version_min_command contains the min OS version on which this
+ * binary was built to run.
+ */
+struct version_min_command {
+ uint32_t cmd; /* LC_VERSION_MIN_MACOSX or
+ LC_VERSION_MIN_IPHONEOS */
+ uint32_t cmdsize; /* sizeof(struct min_version_command) */
+ uint32_t version; /* X.Y.Z is encoded in nibbles xxxx.yy.zz */
+ uint32_t sdk; /* X.Y.Z is encoded in nibbles xxxx.yy.zz */
+};
+
+/*
+ * The dyld_info_command contains the file offsets and sizes of
+ * the new compressed form of the information dyld needs to
+ * load the image. This information is used by dyld on Mac OS X
+ * 10.6 and later. All information pointed to by this command
+ * is encoded using byte streams, so no endian swapping is needed
+ * to interpret it.
+ */
+struct dyld_info_command {
+ uint32_t cmd; /* LC_DYLD_INFO or LC_DYLD_INFO_ONLY */
+ uint32_t cmdsize; /* sizeof(struct dyld_info_command) */
+
+ /*
+ * Dyld rebases an image whenever dyld loads it at an address different
+ * from its preferred address. The rebase information is a stream
+ * of byte sized opcodes whose symbolic names start with REBASE_OPCODE_.
+ * Conceptually the rebase information is a table of tuples:
+ * <seg-index, seg-offset, type>
+ * The opcodes are a compressed way to encode the table by only
+ * encoding when a column changes. In addition simple patterns
+ * like "every n'th offset for m times" can be encoded in a few
+ * bytes.
+ */
+ uint32_t rebase_off; /* file offset to rebase info */
+ uint32_t rebase_size; /* size of rebase info */
+
+ /*
+ * Dyld binds an image during the loading process, if the image
+ * requires any pointers to be initialized to symbols in other images.
+ * The bind information is a stream of byte sized
+ * opcodes whose symbolic names start with BIND_OPCODE_.
+ * Conceptually the bind information is a table of tuples:
+ * <seg-index, seg-offset, type, symbol-library-ordinal, symbol-name, addend>
+ * The opcodes are a compressed way to encode the table by only
+ * encoding when a column changes. In addition simple patterns
+ * like for runs of pointers initialzed to the same value can be
+ * encoded in a few bytes.
+ */
+ uint32_t bind_off; /* file offset to binding info */
+ uint32_t bind_size; /* size of binding info */
+
+ /*
+ * Some C++ programs require dyld to unique symbols so that all
+ * images in the process use the same copy of some code/data.
+ * This step is done after binding. The content of the weak_bind
+ * info is an opcode stream like the bind_info. But it is sorted
+ * alphabetically by symbol name. This enable dyld to walk
+ * all images with weak binding information in order and look
+ * for collisions. If there are no collisions, dyld does
+ * no updating. That means that some fixups are also encoded
+ * in the bind_info. For instance, all calls to "operator new"
+ * are first bound to libstdc++.dylib using the information
+ * in bind_info. Then if some image overrides operator new
+ * that is detected when the weak_bind information is processed
+ * and the call to operator new is then rebound.
+ */
+ uint32_t weak_bind_off; /* file offset to weak binding info */
+ uint32_t weak_bind_size; /* size of weak binding info */
+
+ /*
+ * Some uses of external symbols do not need to be bound immediately.
+ * Instead they can be lazily bound on first use. The lazy_bind
+ * are contains a stream of BIND opcodes to bind all lazy symbols.
+ * Normal use is that dyld ignores the lazy_bind section when
+ * loading an image. Instead the static linker arranged for the
+ * lazy pointer to initially point to a helper function which
+ * pushes the offset into the lazy_bind area for the symbol
+ * needing to be bound, then jumps to dyld which simply adds
+ * the offset to lazy_bind_off to get the information on what
+ * to bind.
+ */
+ uint32_t lazy_bind_off; /* file offset to lazy binding info */
+ uint32_t lazy_bind_size; /* size of lazy binding infs */
+
+ /*
+ * The symbols exported by a dylib are encoded in a trie. This
+ * is a compact representation that factors out common prefixes.
+ * It also reduces LINKEDIT pages in RAM because it encodes all
+ * information (name, address, flags) in one small, contiguous range.
+ * The export area is a stream of nodes. The first node sequentially
+ * is the start node for the trie.
+ *
+ * Nodes for a symbol start with a uleb128 that is the length of
+ * the exported symbol information for the string so far.
+ * If there is no exported symbol, the node starts with a zero byte.
+ * If there is exported info, it follows the length.
+ *
+ * First is a uleb128 containing flags. Normally, it is followed by
+ * a uleb128 encoded offset which is location of the content named
+ * by the symbol from the mach_header for the image. If the flags
+ * is EXPORT_SYMBOL_FLAGS_REEXPORT, then following the flags is
+ * a uleb128 encoded library ordinal, then a zero terminated
+ * UTF8 string. If the string is zero length, then the symbol
+ * is re-export from the specified dylib with the same name.
+ * If the flags is EXPORT_SYMBOL_FLAGS_STUB_AND_RESOLVER, then following
+ * the flags is two uleb128s: the stub offset and the resolver offset.
+ * The stub is used by non-lazy pointers. The resolver is used
+ * by lazy pointers and must be called to get the actual address to use.
+ *
+ * After the optional exported symbol information is a byte of
+ * how many edges (0-255) that this node has leaving it,
+ * followed by each edge.
+ * Each edge is a zero terminated UTF8 of the addition chars
+ * in the symbol, followed by a uleb128 offset for the node that
+ * edge points to.
+ *
+ */
+ uint32_t export_off; /* file offset to lazy binding info */
+ uint32_t export_size; /* size of lazy binding infs */
+};
+
+/*
+ * The following are used to encode rebasing information
+ */
+#define REBASE_TYPE_POINTER 1
+#define REBASE_TYPE_TEXT_ABSOLUTE32 2
+#define REBASE_TYPE_TEXT_PCREL32 3
+
+#define REBASE_OPCODE_MASK 0xF0
+#define REBASE_IMMEDIATE_MASK 0x0F
+#define REBASE_OPCODE_DONE 0x00
+#define REBASE_OPCODE_SET_TYPE_IMM 0x10
+#define REBASE_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB 0x20
+#define REBASE_OPCODE_ADD_ADDR_ULEB 0x30
+#define REBASE_OPCODE_ADD_ADDR_IMM_SCALED 0x40
+#define REBASE_OPCODE_DO_REBASE_IMM_TIMES 0x50
+#define REBASE_OPCODE_DO_REBASE_ULEB_TIMES 0x60
+#define REBASE_OPCODE_DO_REBASE_ADD_ADDR_ULEB 0x70
+#define REBASE_OPCODE_DO_REBASE_ULEB_TIMES_SKIPPING_ULEB 0x80
+
+
+/*
+ * The following are used to encode binding information
+ */
+#define BIND_TYPE_POINTER 1
+#define BIND_TYPE_TEXT_ABSOLUTE32 2
+#define BIND_TYPE_TEXT_PCREL32 3
+
+#define BIND_SPECIAL_DYLIB_SELF 0
+#define BIND_SPECIAL_DYLIB_MAIN_EXECUTABLE -1
+#define BIND_SPECIAL_DYLIB_FLAT_LOOKUP -2
+
+#define BIND_SYMBOL_FLAGS_WEAK_IMPORT 0x1
+#define BIND_SYMBOL_FLAGS_NON_WEAK_DEFINITION 0x8
+
+#define BIND_OPCODE_MASK 0xF0
+#define BIND_IMMEDIATE_MASK 0x0F
+#define BIND_OPCODE_DONE 0x00
+#define BIND_OPCODE_SET_DYLIB_ORDINAL_IMM 0x10
+#define BIND_OPCODE_SET_DYLIB_ORDINAL_ULEB 0x20
+#define BIND_OPCODE_SET_DYLIB_SPECIAL_IMM 0x30
+#define BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM 0x40
+#define BIND_OPCODE_SET_TYPE_IMM 0x50
+#define BIND_OPCODE_SET_ADDEND_SLEB 0x60
+#define BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB 0x70
+#define BIND_OPCODE_ADD_ADDR_ULEB 0x80
+#define BIND_OPCODE_DO_BIND 0x90
+#define BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB 0xA0
+#define BIND_OPCODE_DO_BIND_ADD_ADDR_IMM_SCALED 0xB0
+#define BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB 0xC0
+
+
+/*
+ * The following are used on the flags byte of a terminal node
+ * in the export information.
+ */
+#define EXPORT_SYMBOL_FLAGS_KIND_MASK 0x03
+#define EXPORT_SYMBOL_FLAGS_KIND_REGULAR 0x00
+#define EXPORT_SYMBOL_FLAGS_KIND_THREAD_LOCAL 0x01
+#define EXPORT_SYMBOL_FLAGS_WEAK_DEFINITION 0x04
+#define EXPORT_SYMBOL_FLAGS_REEXPORT 0x08
+#define EXPORT_SYMBOL_FLAGS_STUB_AND_RESOLVER 0x10
+
projects / apple / xnu.git / blobdiff