[lld] [llvm] [lld][AArch64][Build Attributes] Add support for AArch64 Build Attributes (PR #147970)

[Peter Smith via llvm-commits]

================
@@ -537,6 +538,44 @@ uint32_t ObjFile<ELFT>::getSectionIndex(const Elf_Sym &sym) const {
       this);
 }
 
+template <class ELFT>
+static void
+handleAArch64BAAndGnuProperties(ObjFile<ELFT> *file, Ctx &ctx,
+                                const AArch64BuildAttrSubsections &baInfo) {
+  if (file->aarch64PauthAbiCoreInfo) {
+    // Check for data mismatch
+    if (file->aarch64PauthAbiCoreInfo) {
+      if (baInfo.Pauth.TagPlatform != file->aarch64PauthAbiCoreInfo->platform ||
+          baInfo.Pauth.TagSchema != file->aarch64PauthAbiCoreInfo->version)
+        Err(ctx) << file
+                 << " GNU properties and build attributes have conflicting "
+                    "AArch64 PAuth data";
+    }
+    if (baInfo.AndFeatures != file->andFeatures)
+      Err(ctx) << file
+               << " GNU properties and build attributes have conflicting "
+                  "AArch64 PAuth data";
+  } else {
+    // When BuildAttributes are missing, PauthABI value defaults to (TagPlatform
+    // = 0, TagSchema = 0). GNU properties do not write PAuthAbiCoreInfo if GNU
+    // property is not present. To match this behaviour, we only write
+    // PAuthAbiCoreInfo when there is at least one non-zero value. The
+    // specification reserves TagPlatform = 0, TagSchema = 1 values to match the
+    // 'Invalid' GNU property section with platform = 0, version = 0.
+    if (baInfo.Pauth.TagPlatform || baInfo.Pauth.TagSchema) {
+      if (baInfo.Pauth.TagPlatform == 0 && baInfo.Pauth.TagSchema == 1)
+        file->aarch64PauthAbiCoreInfo = {0, 0};
+      else
+        file->aarch64PauthAbiCoreInfo = {baInfo.Pauth.TagPlatform,
+                                         baInfo.Pauth.TagSchema};
+    }
+    file->andFeatures = baInfo.AndFeatures;
+  }
+}
+
+template <typename ELFT>
----------------
smithp35 wrote:

This forward declaration isn't needed anymore.

https://github.com/llvm/llvm-project/pull/147970