[lld] [lld][AArch64][ELF][PAC] Support AUTH relocations and AUTH ELF marking (PR #72714)

[Daniil Kovalev via llvm-commits]

kovdan01 wrote:

> Do we really need to support .note.AARCH64-PAUTH-ABI-tag `NT_ARM_TYPE_PAUTH_ABI_TAG`?

@MaskRay The spec has it defined, and I suppose there is a reason for this. We do not control the input object files we get, and a we might have to process ones with .note.AARCH64-PAUTH-ABI-tag - someone can possibly generate such files since its explicitly allowed by the spec. If we do not process this section properly, we'll just silently concatenate corresponding input sections and emit this in the output - this is definitely not what we want. As for me, support is not that complicated and does not add too much complexity to lld - so, is there a strong reason not to have it? We benefit a lot from supporting the spec fully w/o any gaps and pay for this with a bit of extra code.

P.S. I'm going to push a couple of small changes to this PR and leave comments regarding the latest feedback before re-requesting the review.

https://github.com/llvm/llvm-project/pull/72714