[lld] [llvm] [lld][AArch64][Build Attributes] Add support for converting AArch64 Build Attributes to GNU Properties (PR #131990)

[via llvm-commits]

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@@ -207,6 +212,166 @@ static void updateSupportedARMFeatures(Ctx &ctx,
   ctx.arg.armHasThumb2ISA |= thumb && *thumb >= ARMBuildAttrs::AllowThumb32;
 }
 
+// Sanitize pauth values
+static void sanitizePauthSubSection(
+    Ctx &ctx, std::optional<llvm::BuildAttributeSubSection> &pauthSubSection,
+    InputSection isec) {
+  /*
+    Incomplete data: ignore
+  */
+  if (!pauthSubSection)
+    return;
+  // Currently there are 2 known tags defined for the pauth subsection,
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sivan-shani wrote:

The specification indeed specify:

> When processing a public subsection a tool may encounter a public tag
that it does not recognize. If the subsection is *optional* then the
unrecognized public tag can be safely skipped. If the subsection is
*not optional* then the tool should issue a diagnostic.

Current implementation on the compiler side allows for unknown tags inside pauth, which is a non-optional subsection, as can be seen for example in this [test-file](https://github.com/llvm/llvm-project/blob/main/llvm/test/MC/AArch64/build-attributes-asm-aeabi-numerical-tags.s)

Will change the behavior here to err on unknown tags inside an non-optional subsection. I have note to myself to go back later and change this behavior in the compiler as well. 

https://github.com/llvm/llvm-project/pull/131990