[all-commits] [llvm/llvm-project] ab4e06: [X86][MC] Add R_X86_64_CODE_6_GOTTPOFF (#117277)

[Feng Zou via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ab4e06667dbd777f32061ac3fff69328dc787fce
      https://github.com/llvm/llvm-project/commit/ab4e06667dbd777f32061ac3fff69328dc787fce
  Author: Feng Zou <feng.zou at intel.com>
  Date:   2024-11-26 (Tue, 26 Nov 2024)

  Changed paths:
    M llvm/include/llvm/BinaryFormat/ELFRelocs/x86_64.def
    M llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
    M llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
    M llvm/lib/Target/X86/MCTargetDesc/X86FixupKinds.h
    M llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
    M llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
    M llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFObjectWriter.cpp
    M llvm/test/MC/ELF/relocation.s

  Log Message:
  -----------
  [X86][MC] Add R_X86_64_CODE_6_GOTTPOFF (#117277)

For

    add %reg1, name at GOTTPOFF(%rip), %reg2
    add name at GOTTPOFF(%rip), %reg1, %reg2
    {nf} add %reg1, name at GOTTPOFF(%rip), %reg2
    {nf} add name at GOTTPOFF(%rip), %reg1, %reg2
    {nf} add name at GOTTPOFF(%rip), %reg

add

  `R_X86_64_CODE_6_GOTTPOFF` = 50

if the instruction starts at 6 bytes before the relocation offset. It's
similar to R_X86_64_GOTTPOFF.

Linker can treat `R_X86_64_CODE_6_GOTTPOFF` as `R_X86_64_GOTTPOFF` or
convert the instructions above to

    add $name at tpoff, %reg1, %reg2
    add $name at tpoff, %reg1, %reg2
    {nf} add $name at tpoff, %reg1, %reg2
    {nf} add $name at tpoff, %reg1, %reg2
    {nf} add $name at tpoff, %reg

if the first byte of the instruction at the relocation `offset - 6` is
`0xd5` (namely, encoded w/REX2 prefix) when possible.


Binutils patch:
https://github.com/bminor/binutils-gdb/commit/5bc71c2a6b8efb27089baa1fecded82be4f550a7
Binutils mailthread:
https://sourceware.org/pipermail/binutils/2024-February/132351.html
ABI discussion:
https://groups.google.com/g/x86-64-abi/c/FhEZjCtDLFw/m/VHDjN4orAgAJ
Blog: https://kanrobert.github.io/rfc/All-about-APX-relocation



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications