mach-o/arm64/reloc.h

Relocations for arm64 are a bit different than for other architectures in Mach-O: Scattered relocations are not used. Almost all relocations produced by the compiler are external relocations. An external relocation has the r_extern bit set to 1 and the r_symbolnum field contains the symbol table index of the target label. When the assembler is generating relocations, if the target label is a local label (begins with 'L'), then the previous non-local label in the same section is used as the target of the external relocation. An addend is used with the distance from that non-local label to the target label. Only when there is no previous non-local label in the section is an internal relocation used. The addend (i.e. the 4 in _foo+4) is encoded either in the instruction or in the r_symbolnum of ARM64_RELOC_ADDEND. For ARM64_RELOC_UNSIGNED and ARM64_RELOC_AUTHENTICATED_POINTER, the addend is stored in the instruction. ARM64_RELOC_PAGE21, ARM64_RELOC_PAGEOFF12 and ARM64_RELOC_BRANCH26 must be preceded by an ARM64_RELOC_ADDEND if they need an addend. No other relocations support addends. The relocation types are: ARM64_RELOC_UNSIGNED // For pointer sized fixups ARM64_RELOC_SUBTRACTOR // must be followed by a ARM64_RELOC_UNSIGNED ARM64_RELOC_BRANCH26 // a BL instruction with pc-relative +-128MB displacement ARM64_RELOC_PAGE21 // pc-rel distance to page of target ARM64_RELOC_PAGEOFF12 // offset within page, scaled by r_length ARM64_RELOC_GOT_LOAD_PAGE21 // load with a pc-rel distance to page of a GOT entry ARM64_RELOC_GOT_LOAD_PAGEOFF12 // load with an offset within page, scaled by r_length, of GOT entry ARM64_RELOC_POINTER_TO_GOT // 32-bit pc-rel (or 64-bit absolute) offset to a GOT entry ARM64_RELOC_TLVP_LOAD_PAGE21 // tlv load with a pc-rel distance to page of a GOT entry ARM64_RELOC_TLVP_LOAD_PAGEOFF12 // tlv load with an offset within page, scaled by r_length, of GOT entry ARM64_RELOC_ADDEND // must be followed by ARM64_RELOC_BRANCH26/ARM64_RELOC_PAGE21/ARM64_RELOC_PAGEOFF12 ARM64_RELOC_AUTHENTICATED_POINTER // 64-bit pointer with authentication The following are sample assembly instructions, followed by the relocation and section content they generate in an object file: (arm64_32 only) .long _foo r_type=ARM64_RELOC_UNSIGNED, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo 00 00 00 00 (arm64_32 only) .long _foo + 4 r_type=ARM64_RELOC_UNSIGNED, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo 04 00 00 00 .quad _foo r_type=ARM64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo 00 00 00 00 00 00 00 00 .quad _foo + 16 r_type=ARM64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo 10 00 00 00 00 00 00 00 .quad L1 r_type=ARM64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_prev 10 00 00 00 00 00 00 00 // assumes _prev is the first non-local label 0x10 bytes before L1 10 00 00 00 00 00 00 00 (arm64_32 only) .long _foo - _bar r_type=ARM64_RELOC_SUBTRACTOR, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_bar r_type=ARM64_RELOC_UNSIGNED, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo 00 00 00 00 (arm64_32 only) .long _foo - _bar + 4 r_type=ARM64_RELOC_SUBTRACTOR, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_bar r_type=ARM64_RELOC_UNSIGNED, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo 04 00 00 00 .quad _foo - _bar r_type=ARM64_RELOC_SUBTRACTOR, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_bar r_type=ARM64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo 00 00 00 00 00 00 00 00 .quad _foo - _bar + 4 r_type=ARM64_RELOC_SUBTRACTOR, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_bar r_type=ARM64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo 04 00 00 00 00 00 00 00 .long _foo - . r_type=ARM64_RELOC_SUBTRACTOR, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_prev r_type=ARM64_RELOC_UNSIGNED, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo f8 ff ff ff // assumes _prev is the first non-local label 0x8 bytes before this // .quad .long _foo - L1 r_type=ARM64_RELOC_SUBTRACTOR, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_prev r_type=ARM64_RELOC_UNSIGNED, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo f8 ff ff ff // assumes _prev is the first non-local label 0x8 bytes before L1 .quad _foo - . r_type=ARM64_RELOC_SUBTRACTOR, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_prev r_type=ARM64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo f8 ff ff ff ff ff ff ff // assumes _prev is the first non-local label 0x8 bytes before this // .quad .quad _foo - L1 r_type=ARM64_RELOC_SUBTRACTOR, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_prev r_type=ARM64_RELOC_UNSIGNED, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo f8 ff ff ff ff ff ff ff // assumes _prev is the first non-local label 0x8 bytes before L1 .long L1 - _prev // No relocations. This is an assembly time constant. 12 00 00 00 00 00 00 00 // assumes _prev is the first non-local label 0x12 bytes before L1 .quad L1 - _prev // No relocations. This is an assembly time constant. 12 00 00 00 00 00 00 00 // assumes _prev is the first non-local label 0x12 bytes before L1 bl _foo r_type=ARM64_RELOC_BRANCH26, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo 0x14000000 bl _foo + 4 r_type=ARM64_RELOC_ADDEND, r_length=2, r_extern=0, r_pcrel=0, r_symbolnum=0x000004 r_type=ARM64_RELOC_BRANCH26, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo 0x14000000 adrp x0, _foo@PAGE r_type=ARM64_RELOC_PAGE21, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo 0x90000000 ldr x0, [x0, _foo@PAGEOFF] r_type=ARM64_RELOC_PAGEOFF12, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo 0xf9400000 adrp x0, _foo@PAGE + 0x24 r_type=ARM64_RELOC_ADDEND, r_length=2, r_extern=0, r_pcrel=0, r_symbolnum=0x000024 r_type=ARM64_RELOC_PAGE21, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo 0x90000000 ldr x0, [x0, _foo@PAGEOFF + 0x24] r_type=ARM64_RELOC_ADDEND, r_length=2, r_extern=0, r_pcrel=0, r_symbolnum=0x000024 r_type=ARM64_RELOC_PAGEOFF12, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo 0xf9400000 adrp x0, _foo@GOTPAGE r_type=ARM64_RELOC_GOT_LOAD_PAGE21, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo 0x90000000 ldr x0, [x0, _foo@GOTPAGEOFF] r_type=ARM64_RELOC_GOT_LOAD_PAGEOFF12, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo 0xf9400000 adrp x0, _foo@TLVPPAGE r_type=ARM64_RELOC_TLVP_LOAD_PAGE21, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo 0x90000000 ldr x0, [x0, _foo@TLVPPAGEOFF] r_type=ARM64_RELOC_TLVP_LOAD_PAGEOFF12, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo 0xf9400000 .long _foo@GOT - . r_type=ARM64_RELOC_POINTER_TO_GOT, r_length=2, r_extern=1, r_pcrel=1, r_symbolnum=_foo 00 00 00 00 (arm64_32 only) .long _foo@GOT r_type=ARM64_RELOC_POINTER_TO_GOT, r_length=2, r_extern=1, r_pcrel=0, r_symbolnum=_foo 00 00 00 00 .quad _foo@GOT r_type=ARM64_RELOC_POINTER_TO_GOT, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo 00 00 00 00 00 00 00 00 (arm64e only) .quad _foo@AUTH(da,5,addr) r_type=ARM64_RELOC_AUTHENTICATED_POINTER, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo 00 00 00 00 05 00 05 80 (arm64e only) .quad (_foo + 0x10)@AUTH(da,5,addr) r_type=ARM64_RELOC_AUTHENTICATED_POINTER, r_length=3, r_extern=1, r_pcrel=0, r_symbolnum=_foo 10 00 00 00 05 00 05 80