1 files changed, 65 insertions, 7 deletions

diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index 71e72e7..37e4c8a 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -21,6 +21,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/LTO/LTO.h"
 #include "llvm/Object/IRObjectFile.h"
+#include "llvm/Support/AArch64AttributeParser.h"
 #include "llvm/Support/ARMAttributeParser.h"
 #include "llvm/Support/ARMBuildAttributes.h"
 #include "llvm/Support/Endian.h"
@@ -537,6 +538,41 @@ 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 <class ELFT> void ObjFile<ELFT>::parse(bool ignoreComdats) {
   object::ELFFile<ELFT> obj = this->getObj();
   // Read a section table. justSymbols is usually false.
@@ -554,6 +590,7 @@ template <class ELFT> void ObjFile<ELFT>::parse(bool ignoreComdats) {
   sections.resize(size);
   for (size_t i = 0; i != size; ++i) {
     const Elf_Shdr &sec = objSections[i];
+
     if (LLVM_LIKELY(sec.sh_type == SHT_PROGBITS))
       continue;
     if (LLVM_LIKELY(sec.sh_type == SHT_GROUP)) {
@@ -637,13 +674,6 @@ template <class ELFT> void ObjFile<ELFT>::parse(bool ignoreComdats) {
       }
       break;
     case EM_AARCH64:
-      // FIXME: BuildAttributes have been implemented in llvm, but not yet in
-      // lld. Remove the section so that it does not accumulate in the output
-      // file. When support is implemented we expect not to output a build
-      // attributes section in files of type ET_EXEC or ET_SHARED, but ld -r
-      // ouptut will need a single merged attributes section.
-      if (sec.sh_type == SHT_AARCH64_ATTRIBUTES)
-        sections[i] = &InputSection::discarded;
       // Producing a static binary with MTE globals is not currently supported,
       // remove all SHT_AARCH64_MEMTAG_GLOBALS_STATIC sections as they're unused
       // medatada, and we don't want them to end up in the output file for
@@ -744,6 +774,8 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats,
   StringRef shstrtab = CHECK2(obj.getSectionStringTable(objSections), this);
   uint64_t size = objSections.size();
   SmallVector<ArrayRef<Elf_Word>, 0> selectedGroups;
+  AArch64BuildAttrSubsections aarch64BAsubSections;
+  bool hasAArch64BuildAttributes = false;
   for (size_t i = 0; i != size; ++i) {
     if (this->sections[i] == &InputSection::discarded)
       continue;
@@ -775,6 +807,26 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats,
       continue;
     }
 
+    // Processor-specific types that do not use the following switch statement.
+    //
+    // Extract Build Attributes section contents into aarch64BAsubSections.
+    // Input objects may contain both build Build Attributes and GNU
+    // properties. We delay processing Build Attributes until we have finished
+    // reading all sections so that we can check that these are consistent.
+    if (type == SHT_AARCH64_ATTRIBUTES && ctx.arg.emachine == EM_AARCH64) {
+      ArrayRef<uint8_t> contents = check(obj.getSectionContents(sec));
+      AArch64AttributeParser attributes;
+      if (Error e = attributes.parse(contents, ELFT::Endianness)) {
+        StringRef name = check(obj.getSectionName(sec, shstrtab));
+        InputSection isec(*this, sec, name);
+        Warn(ctx) << &isec << ": " << std::move(e);
+      } else {
+        aarch64BAsubSections = extractBuildAttributesSubsections(attributes);
+        hasAArch64BuildAttributes = true;
+      }
+      this->sections[i] = &InputSection::discarded;
+      continue;
+    }
     switch (type) {
     case SHT_GROUP: {
       if (!ctx.arg.relocatable)
@@ -912,6 +964,12 @@ void ObjFile<ELFT>::initializeSections(bool ignoreComdats,
           << linkSec;
   }
 
+  // Handle AArch64 Build Attributes and GNU properties:
+  // - Err on mismatched values.
+  // - Store missing values as GNU properties.
+  if (hasAArch64BuildAttributes)
+    handleAArch64BAAndGnuProperties<ELFT>(this, ctx, aarch64BAsubSections);
+
   for (ArrayRef<Elf_Word> entries : selectedGroups)
     handleSectionGroup<ELFT>(this->sections, entries);
 }