[all-commits] [llvm/llvm-project] 1aa29d: [lld-macho] Support subtractor relocations that re...

[Jez Ng via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1aa29dffceff63c7f2bdecc03ec9c0922a100082
      https://github.com/llvm/llvm-project/commit/1aa29dffceff63c7f2bdecc03ec9c0922a100082
  Author: Jez Ng <jezng at fb.com>
  Date:   2021-04-20 (Tue, 20 Apr 2021)

  Changed paths:
    M lld/MachO/Arch/ARM64.cpp
    M lld/MachO/Arch/ARM64Common.cpp
    M lld/MachO/Arch/ARM64_32.cpp
    M lld/MachO/Arch/X86_64.cpp
    M lld/MachO/InputFiles.cpp
    M lld/MachO/InputSection.cpp
    M lld/MachO/Writer.cpp
    M lld/test/MachO/reloc-subtractor.s

  Log Message:
  -----------
  [lld-macho] Support subtractor relocations that reference sections

The minuend (but not the subtrahend) can reference a section.

Note that we do not yet properly validate that the subtrahend isn't
referencing a section; I've filed PR50034 to track that.

I've also extended the reloc-subtractor.s test to reorder symbols, to
make sure that the addends are being associated with the minuend (and not
the subtrahend) relocation.

Fixes PR49999.

Reviewed By: #lld-macho, thakis

Differential Revision: https://reviews.llvm.org/D100804


  Commit: bb62ef9943008281a2223c942c71e67b3902a07e
      https://github.com/llvm/llvm-project/commit/bb62ef9943008281a2223c942c71e67b3902a07e
  Author: Jez Ng <jezng at fb.com>
  Date:   2021-04-20 (Tue, 20 Apr 2021)

  Changed paths:
    M lld/MachO/OutputSegment.h
    M lld/MachO/Writer.cpp
    M lld/test/MachO/bitcode-bundle.ll
    M lld/test/MachO/bss.s
    M lld/test/MachO/linkedit-contiguity.s
    M lld/test/MachO/section-headers.s
    M lld/test/MachO/segments.s

  Log Message:
  -----------
  [lld-macho] Ensure segments are laid out contiguously

codesign/libstuff checks that the `__LLVM` segment is directly
before `__LINKEDIT` by checking that `fileOff + fileSize == next segment
fileOff`. Previously, there would be gaps between the segments due to
the fact that their fileOffs are page-aligned but their fileSizes
aren't. In order to satisfy codesign, we page-align fileOff *before*
calculating fileSize. (I don't think codesign checks for the relative
ordering of other segments, so in theory we could do this just for
`__LLVM`, but ld64 seems to do it for all segments.)

Note that we *don't* round up the fileSize of the `__LINKEDIT` segment.
Since it's the last segment, it doesn't need to worry about contiguity;
in addition, codesign checks that the last (hidden) section in
`__LINKEDIT` covers the last byte of the segment, so if we rounded up
`__LINKEDIT`'s size we would have to do the same for its last section,
which is a bother.

While at it, I also addressed a FIXME in the linkedit-contiguity.s test
to cover more `__LINKEDIT` sections.

Reviewed By: #lld-macho, thakis, alexshap

Differential Revision: https://reviews.llvm.org/D100848


Compare: https://github.com/llvm/llvm-project/compare/673e2f1b70dd...bb62ef994300