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[ELF] -r: allow SHT_X86_64_UNWIND to be merged into SHT_PROGBITS
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Authored by MaskRay on Aug 12 2020, 8:14 PM.

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Description

[ELF] -r: allow SHT_X86_64_UNWIND to be merged into SHT_PROGBITS

  • For .cfi_*, GCC/GNU as emits SHT_PROGBITS type .eh_frame sections.
  • Since rL252300, clang emits SHT_X86_64_UNWIND type .eh_frame sections (originated from Solaris, documented in the x86-64 psABI).
  • Some assembly use .section .eh_frame,"a",@unwind to generate SHT_X86_64_UNWIND .eh_frame sections.

In a non-relocatable link, input .eh_frame are combined and there is
only one SyntheticSection .eh_frame in the output section, so the
"section type mismatch" diagnostic does not fire.

In a relocatable link, there is no SyntheticSection .eh_frame. .eh_frame of
mixed types can trigger the diagnostic. This patch fixes it by adding another
special case 0x70000001 (= SHT_X86_64_UNWIND) to canMergeToProgbits().

ld.lld -r gcc.o clang.o => error: section type mismatch for .eh_frame

There was a discussion "RFC: Usefulness of SHT_X86_64_UNWIND" on the x86-64-abi
mailing list. Folks are not wild about making the psABI value 0x70000001 into
gABI, but a few think defining 0x70000001 for .eh_frame may be a good idea for a
new architecture.

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D85785

(cherry picked from commit 88498f44dfe7d9b886f2622335cdeae4dbf2b02a)

Details

Committed
hansAug 26 2020, 8:01 AM
Parents
rG46f3aed198a5: Bump -len_control value in fuzzer-custommutator.test (PR47286)
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