[all-commits] [llvm/llvm-project] 216788: [ARM, MC] Support FDPIC relocations

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2167881f5154823dc3183845700add7df15fc856
      https://github.com/llvm/llvm-project/commit/2167881f5154823dc3183845700add7df15fc856
  Author: Fangrui Song <i at maskray.me>
  Date:   2024-02-21 (Wed, 21 Feb 2024)

  Changed paths:
    M llvm/include/llvm/BinaryFormat/ELF.h
    M llvm/include/llvm/BinaryFormat/ELFRelocs/ARM.def
    M llvm/include/llvm/MC/MCExpr.h
    M llvm/include/llvm/MC/MCParser/MCTargetAsmParser.h
    M llvm/include/llvm/MC/MCTargetOptions.h
    M llvm/include/llvm/MC/MCTargetOptionsCommandFlags.h
    M llvm/lib/MC/MCExpr.cpp
    M llvm/lib/MC/MCParser/AsmParser.cpp
    M llvm/lib/MC/MCTargetOptions.cpp
    M llvm/lib/MC/MCTargetOptionsCommandFlags.cpp
    M llvm/lib/ObjectYAML/ELFYAML.cpp
    M llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
    M llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
    M llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
    M llvm/lib/Target/ARM/MCTargetDesc/CMakeLists.txt
    A llvm/test/MC/ARM/fdpic.s
    M llvm/test/tools/llvm-readobj/ELF/file-header-os-abi.test
    M llvm/test/tools/llvm-readobj/ELF/reloc-types-arm.test
    M llvm/tools/llvm-readobj/ELFDumper.cpp

  Log Message:
  -----------
  [ARM,MC] Support FDPIC relocations

Linux kernel fs/binfmt_elf_fdpic.c supports FDPIC for MMU-less systems.
GCC/binutils/qemu support FDPIC ABI for ARM
(https://github.com/mickael-guene/fdpic_doc).
_ARM FDPIC Toolchain and ABI_ provides a summary.

This patch implements FDPIC relocations to the integrated assembler.
There are 6 static relocations and 2 dynamic relocations, with
R_ARM_FUNCDESC as both static and dynamic.

gas requires `--fdpic` to assemble data relocations like `.word f(FUNCDESC)`.
This patch adds `MCTargetOptions::FDPIC` and reports an error if FDPIC
is not set.

Pull Request: https://github.com/llvm/llvm-project/pull/82187



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