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

[Jack Styles via llvm-commits]

================
@@ -539,6 +541,156 @@ uint32_t ObjFile<ELFT>::getSectionIndex(const Elf_Sym &sym) const {
       this);
 }
 
+template <typename ELFT>
+static void parseGnuPropertyNote(Ctx &ctx, ELFFileBase &f,
+                                 uint32_t featureAndType,
+                                 ArrayRef<uint8_t> &desc, const uint8_t *base,
+                                 ArrayRef<uint8_t> *data = nullptr) {
+  auto err = [&](const uint8_t *place) -> ELFSyncStream {
+    auto diag = Err(ctx);
+    diag << &f << ":(" << ".note.gnu.property+0x"
+         << Twine::utohexstr(place - base) << "): ";
+    return diag;
+  };
+
+  while (!desc.empty()) {
+    const uint8_t *place = desc.data();
+    if (desc.size() < 8)
+      return void(err(place) << "program property is too short");
+    uint32_t type = read32<ELFT::Endianness>(desc.data());
+    uint32_t size = read32<ELFT::Endianness>(desc.data() + 4);
+    desc = desc.slice(8);
+    if (desc.size() < size)
+      return void(err(place) << "program property is too short");
+
+    if (type == featureAndType) {
+      // We found a FEATURE_1_AND field. There may be more than one of these
+      // in a .note.gnu.property section, for a relocatable object we
+      // accumulate the bits set.
+      if (size < 4)
+        return void(err(place) << "FEATURE_1_AND entry is too short");
+      f.andFeatures |= read32<ELFT::Endianness>(desc.data());
+    } else if (ctx.arg.emachine == EM_AARCH64 &&
+               type == GNU_PROPERTY_AARCH64_FEATURE_PAUTH) {
+      ArrayRef<uint8_t> contents = data ? *data : desc;
+      if (!f.aarch64PauthAbiCoreInfo.empty()) {
+        return void(
+            err(contents.data())
+            << "multiple GNU_PROPERTY_AARCH64_FEATURE_PAUTH entries are "
+               "not supported");
+      } else if (size != 16) {
+        return void(err(contents.data())
+                    << "GNU_PROPERTY_AARCH64_FEATURE_PAUTH entry "
+                       "is invalid: expected 16 bytes, but got "
+                    << size);
+      }
+      f.aarch64PauthAbiCoreInfo = desc;
+    }
+
+    // Padding is present in the note descriptor, if necessary.
+    desc = desc.slice(alignTo<(ELFT::Is64Bits ? 8 : 4)>(size));
+  }
+}
+// Read the following info from the .note.gnu.property section and write it to
----------------
Stylie777 wrote:

nit: Add a line of whitespace here to separate the previous function and the next. 

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