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

[Peter Smith 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,
+  // however, user is allowed to add other, unknown tag. If such tags exists,
+  // remove them. (no need to check for duplicates, they should not be possible)
+  pauthSubSection->Content.erase(
+      std::remove_if(pauthSubSection->Content.begin(),
+                     pauthSubSection->Content.end(),
+                     [](const BuildAttributeItem &item) {
+                       return item.Tag != 1 && item.Tag != 2;
+                     }),
+      pauthSubSection->Content.end());
+
+  if (pauthSubSection->Content.size() < 2) {
+    if (0 == pauthSubSection->Content.size())
+      Warn(ctx) << &isec
+                << ": AArch64 Build Attributes: empty 'aeabi_pauthabi' "
+                   "subsection detected; ignoring subsection";
+    if (1 == pauthSubSection->Content.size()) {
+      if (1 == pauthSubSection->Content[0].Tag)
----------------
smithp35 wrote:

Is 1 supposed to be Tag_PAuth_Platform?

If so please can we use named constants rather than magic numbers? For example the 1 == looks similar to the size.

llvm/include/Support/AArch64BuildAttributes.h looks to have enums that define these tags.

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