[lld] [lld] Add support for eh_frame_hdr sdata8 (PR #174486)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> @MaskRay is this ok independently of the other work? this shouldn't need any x86-64 ABI proposals

Yes, this is ok independent of the other work.

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The title should mention `.eh_frame_hdr` instead of `eh_frame_hdr`.

> Broader motivation: I am working to support large binaries with mcmodel=medium and I ran into this reported issue (+ others).

Can the first sentence be changed to something clearer? A description about what kind of programs run into this issue and you need `DW_EH_PE_sdata8` (please use the formal `DW_EH_PE_sdata8` instead of `sdata8`).

> The eh_frame_hdr supports variable encodings ([refspecs.linuxfoundation.org/LSB_1.3.0/gLSB/gLSB/ehframehdr.html](https://refspecs.linuxfoundation.org/LSB_1.3.0/gLSB/gLSB/ehframehdr.html)).

Should use a LSB 5.0.0 link: https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html#AEN1442


https://github.com/llvm/llvm-project/pull/174486