#include <mach-o/fixup-chains.h>
Mach-O › File format

mach-o/fixup-chains.h

#define LC_DYLD_EXPORTS_TRIE 0x80000033 // used with linkedit_data_command
includes: stdint.h
24 structs · 4 enums

structdyld_chained_fixups_header

header of the LC_DYLD_CHAINED_FIXUPS payload
size 28, align 4
uint32_tfixups_version0
uint32_tstarts_offsetoffset of dyld_chained_starts_in_image in chain_data
uint32_timports_offsetoffset of imports table in chain_data
uint32_tsymbols_offsetoffset of symbol strings in chain_data
uint32_timports_countnumber of imported symbol names
uint32_timports_formatDYLD_CHAINED_IMPORT*
uint32_tsymbols_format0 => uncompressed, 1 => zlib compressed

structdyld_chained_starts_in_image

This struct is embedded in LC_DYLD_CHAINED_FIXUPS payload
size 8, align 4
uint32_tseg_count
uint32_t[1]seg_info_offseteach entry is offset into this struct for that segment

structdyld_chained_starts_in_segment

This struct is embedded in dyld_chain_starts_in_image and passed down to the kernel for page-in linking
size 24, align 8
uint32_tsizesize of this (amount kernel needs to copy)
uint16_tpage_size0x1000 or 0x4000
uint16_tpointer_formatDYLD_CHAINED_PTR_*
uint64_tsegment_offsetoffset in memory to start of segment
uint32_tmax_valid_pointerfor 32-bit OS, any value beyond this is not a pointer
uint16_tpage_counthow many pages are in array
uint16_t[1]page_starteach entry is offset in each page of first element in chain

enum(anonymous)

underlying type unsigned int
DYLD_CHAINED_PTR_START_NONE65535used in page_start[] to denote a page with no fixups
DYLD_CHAINED_PTR_START_MULTI32768used in page_start[] to denote a page which has multiple starts
DYLD_CHAINED_PTR_START_LAST32768used in chain_starts[] to denote last start in list for page

enum(anonymous)

these values are set in the reserved1 field of the __chain_starts section
underlying type unsigned int
DYLD_CHAINED_STARTS_USE_FILE_OFFSET1denotes chain starts linked with -fixup_chains_section
DYLD_CHAINED_STARTS_USE_VM_OFFSET2denotes chain starts linked with -fixup_chains_section_vm

structdyld_chained_starts_offsets

This struct is embedded in __TEXT,__chain_starts section in firmware
size 12, align 4
uint32_tpointer_formatDYLD_CHAINED_PTR_32_FIRMWARE or DYLD_CHAINED_PTR_ARM64E_KERNEL
uint32_tstarts_countnumber of starts in array
uint32_t[1]chain_startsarray chain start offsets

enum(anonymous)

values for dyld_chained_starts_in_segment.pointer_format
underlying type unsigned int
DYLD_CHAINED_PTR_ARM64E1stride 8, unauth target is vmaddr
DYLD_CHAINED_PTR_642target is vmaddr
DYLD_CHAINED_PTR_323target is vmaddr
DYLD_CHAINED_PTR_32_CACHE4
DYLD_CHAINED_PTR_32_FIRMWARE5
DYLD_CHAINED_PTR_64_OFFSET6target is vm offset
DYLD_CHAINED_PTR_ARM64E_OFFSET7old name
DYLD_CHAINED_PTR_ARM64E_KERNEL7stride 4, unauth target is vm offset
DYLD_CHAINED_PTR_64_KERNEL_CACHE8
DYLD_CHAINED_PTR_ARM64E_USERLAND9stride 8, unauth target is vm offset
DYLD_CHAINED_PTR_ARM64E_FIRMWARE10stride 4, unauth target is vmaddr
DYLD_CHAINED_PTR_X86_64_KERNEL_CACHE11stride 1, x86_64 kernel caches
DYLD_CHAINED_PTR_ARM64E_USERLAND2412stride 8, unauth target is vm offset, 24-bit bind
DYLD_CHAINED_PTR_ARM64E_SHARED_CACHE13stride 8, regular/auth targets both vm offsets. Only A keys supported
DYLD_CHAINED_PTR_ARM64E_SEGMENTED14stride 4, rebase offsets use segIndex and segOffset

structdyld_chained_ptr_arm64e_rebase

DYLD_CHAINED_PTR_ARM64E
size 8, align 8
uint64_t:43target
uint64_t:8high8
uint64_t:11next4 or 8-byte stide
uint64_t:1bind== 0
uint64_t:1auth== 0

structdyld_chained_ptr_arm64e_bind

DYLD_CHAINED_PTR_ARM64E
size 8, align 8
uint64_t:16ordinal
uint64_t:16zero
uint64_t:19addend+/-256K
uint64_t:11next4 or 8-byte stide
uint64_t:1bind== 1
uint64_t:1auth== 0

structdyld_chained_ptr_arm64e_auth_rebase

DYLD_CHAINED_PTR_ARM64E
size 8, align 8
uint64_t:32targetruntimeOffset
uint64_t:16diversity
uint64_t:1addrDiv
uint64_t:2key
uint64_t:11next4 or 8-byte stide
uint64_t:1bind== 0
uint64_t:1auth== 1

structdyld_chained_ptr_arm64e_auth_bind

DYLD_CHAINED_PTR_ARM64E
size 8, align 8
uint64_t:16ordinal
uint64_t:16zero
uint64_t:16diversity
uint64_t:1addrDiv
uint64_t:2key
uint64_t:11next4 or 8-byte stide
uint64_t:1bind== 1
uint64_t:1auth== 1

structdyld_chained_ptr_64_rebase

DYLD_CHAINED_PTR_64/DYLD_CHAINED_PTR_64_OFFSET
size 8, align 8
uint64_t:36target64GB max image size (DYLD_CHAINED_PTR_64 => vmAddr, DYLD_CHAINED_PTR_64_OFFSET => runtimeOffset)
uint64_t:8high8top 8 bits set to this (DYLD_CHAINED_PTR_64 => after slide added, DYLD_CHAINED_PTR_64_OFFSET => before slide added)
uint64_t:7reservedall zeros
uint64_t:12next4-byte stride
uint64_t:1bind== 0

structdyld_chained_ptr_arm64e_bind24

DYLD_CHAINED_PTR_ARM64E_USERLAND24
size 8, align 8
uint64_t:24ordinal
uint64_t:8zero
uint64_t:19addend+/-256K
uint64_t:11next8-byte stide
uint64_t:1bind== 1
uint64_t:1auth== 0

structdyld_chained_ptr_arm64e_auth_bind24

DYLD_CHAINED_PTR_ARM64E_USERLAND24
size 8, align 8
uint64_t:24ordinal
uint64_t:8zero
uint64_t:16diversity
uint64_t:1addrDiv
uint64_t:2key
uint64_t:11next8-byte stide
uint64_t:1bind== 1
uint64_t:1auth== 1

structdyld_chained_ptr_arm64e_segmented_rebase

DYLD_CHAINED_PTR_ARM64E_SEGMENTED
size 8, align 4
uint32_t:28targetSegOffsetoffset in segment
uint32_t:4targetSegIndexindex into segment address table
uint32_t:19padding
uint32_t:12next4-byte stide
uint32_t:1auth== 0

structdyld_chained_ptr_arm64e_auth_segmented_rebase

DYLD_CHAINED_PTR_ARM64E_SEGMENTED
size 8, align 4
uint32_t:28targetSegOffsetoffset in segment
uint32_t:4targetSegIndexindex into segment address table
uint32_t:16diversity
uint32_t:1addrDiv
uint32_t:2key
uint32_t:12next4-byte stide
uint32_t:1auth== 1

structdyld_chained_ptr_64_bind

DYLD_CHAINED_PTR_64
size 8, align 8
uint64_t:24ordinal
uint64_t:8addend0 thru 255
uint64_t:19reservedall zeros
uint64_t:12next4-byte stride
uint64_t:1bind== 1

structdyld_chained_ptr_64_kernel_cache_rebase

DYLD_CHAINED_PTR_64_KERNEL_CACHE, DYLD_CHAINED_PTR_X86_64_KERNEL_CACHE
size 8, align 8
uint64_t:30targetbasePointers[cacheLevel] + target
uint64_t:2cacheLevelwhat level of cache to bind to (indexes a mach_header array)
uint64_t:16diversity
uint64_t:1addrDiv
uint64_t:2key
uint64_t:12next1 or 4-byte stide
uint64_t:1isAuth0 -> not authenticated. 1 -> authenticated

structdyld_chained_ptr_32_rebase

DYLD_CHAINED_PTR_32 Note: for DYLD_CHAINED_PTR_32 some non-pointer values are co-opted into the chain as out of range rebases. If an entry in the chain is > max_valid_pointer, then it is not a pointer. To restore the value, subtract off the bias, which is (64MB+max_valid_pointer)/2.
size 4, align 4
uint32_t:26targetvmaddr, 64MB max image size
uint32_t:5next4-byte stride
uint32_t:1bind== 0

structdyld_chained_ptr_32_bind

DYLD_CHAINED_PTR_32
size 4, align 4
uint32_t:20ordinal
uint32_t:6addend0 thru 63
uint32_t:5next4-byte stride
uint32_t:1bind== 1

structdyld_chained_ptr_32_cache_rebase

DYLD_CHAINED_PTR_32_CACHE
size 4, align 4
uint32_t:30target1GB max dyld cache TEXT and DATA
uint32_t:2next4-byte stride

structdyld_chained_ptr_32_firmware_rebase

DYLD_CHAINED_PTR_32_FIRMWARE
size 4, align 4
uint32_t:26target64MB max firmware TEXT and DATA
uint32_t:6next4-byte stride

structdyld_chained_ptr_arm64e_shared_cache_rebase

DYLD_CHAINED_PTR_ARM64E_SHARED_CACHE
size 8, align 8
uint64_t:34runtimeOffsetoffset from the start of the shared cache
uint64_t:8high8
uint64_t:10unused
uint64_t:11next8-byte stide
uint64_t:1auth== 0

structdyld_chained_ptr_arm64e_shared_cache_auth_rebase

DYLD_CHAINED_PTR_ARM64E_SHARED_CACHE
size 8, align 8
uint64_t:34runtimeOffsetoffset from the start of the shared cache
uint64_t:16diversity
uint64_t:1addrDiv
uint64_t:1keyIsDataimplicitly always the 'A' key. 0 -> IA. 1 -> DA
uint64_t:11next8-byte stide
uint64_t:1auth== 1

enum(anonymous)

values for dyld_chained_fixups_header.imports_format
underlying type unsigned int
DYLD_CHAINED_IMPORT1
DYLD_CHAINED_IMPORT_ADDEND2
DYLD_CHAINED_IMPORT_ADDEND643

structdyld_chained_import

DYLD_CHAINED_IMPORT
size 4, align 4
uint32_t:8lib_ordinal-15 .. 240 (0xF1 .. 0xF0)
uint32_t:1weak_import
uint32_t:23name_offset

structdyld_chained_import_addend

DYLD_CHAINED_IMPORT_ADDEND
size 8, align 4
uint32_t:8lib_ordinal-15 .. 240 (0xF1 .. 0xF0)
uint32_t:1weak_import
uint32_t:23name_offset
int32_taddend

structdyld_chained_import_addend64

DYLD_CHAINED_IMPORT_ADDEND64
size 16, align 8
uint64_t:16lib_ordinal-15 .. 65520 (0xFFF1 .. 0xFFF0)
uint64_t:1weak_import
uint64_t:15reserved
uint64_t:32name_offset
uint64_taddend