[AArch64][PAC][lldb][Dwarf] Support [[clang::ptrauth_struct(...)]] attribute

kovdan01 · kovdan01 · commit 3a04a18d72b9 · 2024-02-16T20:26:57.000+03:00
Use IR metadata annotations for storing `ptrauth_struct_key` and
`ptrauth_struct_disc` values. Corresponding `DW_TAG_LLVM_annotation`
tags are used in Dwarf.
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -2304,6 +2304,50 @@ llvm::DINodeArray CGDebugInfo::CollectBTFDeclTagAnnotations(const Decl *D) {
   return DBuilder.getOrCreateArray(Annotations);
 }
 
+llvm::DINodeArray
+CGDebugInfo::CollectPtrAuthStructAnnotations(const RecordDecl *RD) {
+  if (!RD->hasAttr<PointerAuthStructAttr>())
+    return nullptr;
+
+  llvm::LLVMContext &Context = CGM.getLLVMContext();
+
+  auto [IsKeyValIndependent, Key] =
+      CGM.getContext().getPointerAuthStructKey(RD);
+  auto [IsDiscValIndependent, Disc] =
+      CGM.getContext().getPointerAuthStructDisc(RD);
+
+  // TODO: handle value-dependent keys and discriminators. What does this even
+  // mean? Using template integer parameters as key/disc or expressions like
+  // `__builtin_ptrauth_struct_key(...)` result in specific constants, and does
+  // not make key/disc value dependent.
+  if (!IsKeyValIndependent || !IsDiscValIndependent)
+    return nullptr;
+
+  // TODO: 2-bit key and 16-bit disc results in negative values of i2 and i16
+  // types in IR for unsigned integers using all the given bit-width (for ex.,
+  // key 3 is i8 -1, disc 65534 is i16 -2). Do we want to use wider types to
+  // prevent negation?
+  auto *KeyMD = llvm::ConstantAsMetadata::get(
+      llvm::ConstantInt::get(Context, llvm::APInt(2, Key, false)));
+  auto *DiscMD = llvm::ConstantAsMetadata::get(
+      llvm::ConstantInt::get(Context, llvm::APInt(16, Disc, false)));
+
+  llvm::Metadata *Annotations[2];
+  llvm::Metadata *OpsKey[2] = {
+      llvm::MDString::get(Context, StringRef("ptrauth_struct_key")), KeyMD};
+  Annotations[0] = llvm::MDNode::get(CGM.getLLVMContext(), OpsKey);
+  llvm::Metadata *OpsDisc[2] = {
+      llvm::MDString::get(Context, StringRef("ptrauth_struct_disc")), DiscMD};
+  Annotations[1] = llvm::MDNode::get(CGM.getLLVMContext(), OpsDisc);
+
+  // TODO: is it OK to return DINodeArray instead of MDNodeArray from
+  // CollectPtrAuthStructAnnotations and CollectBTFDeclTagAnnotations? The
+  // elements are not actually DINodes, and trying to iterate over the returned
+  // DINodeArray results in an assertion failure. This does not seem to happen
+  // though - it looks like that there are no places where such loops are used.
+  return DBuilder.getOrCreateArray(Annotations);
+}
+
 llvm::DIType *CGDebugInfo::getOrCreateVTablePtrType(llvm::DIFile *Unit) {
   if (VTablePtrType)
     return VTablePtrType;
@@ -3790,7 +3834,21 @@ llvm::DICompositeType *CGDebugInfo::CreateLimitedType(const RecordType *Ty) {
                            dyn_cast<CXXRecordDecl>(CXXRD->getDeclContext()));
   }
 
-  llvm::DINodeArray Annotations = CollectBTFDeclTagAnnotations(D);
+  llvm::DINodeArray AnnotationsBTFTag = CollectBTFDeclTagAnnotations(D);
+  llvm::DINodeArray AnnotationsPAuthStruct = CollectPtrAuthStructAnnotations(D);
+
+  llvm::SmallVector<llvm::Metadata *, 4> AnnotationsVec;
+  if (AnnotationsBTFTag.get() != nullptr)
+    for (const llvm::MDOperand &Op : AnnotationsBTFTag.get()->operands())
+        AnnotationsVec.push_back(Op.get());
+  if (AnnotationsPAuthStruct.get() != nullptr)
+    for (const llvm::MDOperand &Op : AnnotationsPAuthStruct.get()->operands())
+        AnnotationsVec.push_back(Op.get());
+
+  llvm::DINodeArray Annotations =
+      AnnotationsVec.empty() ? nullptr
+                             : DBuilder.getOrCreateArray(AnnotationsVec);
+
   llvm::DICompositeType *RealDecl = DBuilder.createReplaceableCompositeType(
       getTagForRecord(RD), RDName, RDContext, DefUnit, Line, 0, Size, Align,
       Flags, Identifier, Annotations);
diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h
@@ -316,6 +316,9 @@ class CGDebugInfo {
   /// A helper function to collect debug info for btf_decl_tag annotations.
   llvm::DINodeArray CollectBTFDeclTagAnnotations(const Decl *D);
 
+  /// A helper function to collect debug info for ptrauth_struct attribute.
+  llvm::DINodeArray CollectPtrAuthStructAnnotations(const RecordDecl *RD);
+
   llvm::DIType *createFieldType(StringRef name, QualType type,
                                 SourceLocation loc, AccessSpecifier AS,
                                 uint64_t offsetInBits, uint32_t AlignInBits,
diff --git a/clang/test/CodeGenCXX/ptrauth-struct-attr-annotations.cpp b/clang/test/CodeGenCXX/ptrauth-struct-attr-annotations.cpp
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -triple aarch64 -emit-llvm -debug-info-kind=limited -o - %s | FileCheck %s
+
+#include <ptrauth.h>
+
+struct __attribute__((ptrauth_struct(1, 42))) S0 {};
+
+template <int k>
+class [[clang::ptrauth_struct(k, 65534)]] S1 {};
+
+union __attribute__((ptrauth_struct(__builtin_ptrauth_struct_key(S0) + 1, __builtin_ptrauth_struct_disc(S0) + 1))) S2 {};
+
+S0 s0;
+S1<3> s1;
+S2 s2;
+
+// CHECK:      !DICompositeType(tag: DW_TAG_class_type, name: "S1<3>",
+// CHECK-SAME: annotations: ![[A1:.*]])
+// CHECK:      ![[A1]] = !{![[A1K:.*]], ![[A1D:.*]]}
+// CHECK:      ![[A1K]] = !{!"ptrauth_struct_key", i2 -1}
+// CHECK:      ![[A1D]] = !{!"ptrauth_struct_disc", i16 -2}
+
+// CHECK:      !DICompositeType(tag: DW_TAG_union_type, name: "S2",
+// CHECK-SAME: annotations: ![[A2:.*]])
+// CHECK:      ![[A2]] = !{![[A2K:.*]], ![[A2D:.*]]}
+// CHECK:      ![[A2K]] = !{!"ptrauth_struct_key", i2 -2}
+// CHECK:      ![[A2D]] = !{!"ptrauth_struct_disc", i16 43}
+
+// CHECK:      !DICompositeType(tag: DW_TAG_structure_type, name: "S0",
+// CHECK-SAME: annotations: ![[A0:.*]])
+// CHECK:      ![[A0]] = !{![[A0K:.*]], ![[A0D:.*]]}
+// CHECK:      ![[A0K]] = !{!"ptrauth_struct_key", i2 1}
+// CHECK:      ![[A0D]] = !{!"ptrauth_struct_disc", i16 42}
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -1884,6 +1884,39 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
                 discriminator));
       }
     }
+
+    // TODO: check that each annotation does not appear more than once
+    std::optional<uint64_t> pauth_key, pauth_disc;
+    for (DWARFDIE die_child = die.GetFirstChild(); die_child;
+         die_child = die_child.GetSibling()) {
+      if (die_child.Tag() != DW_TAG_LLVM_annotation)
+        continue;
+      if (die_child.GetAttributeValueAsString(DW_AT_name, nullptr) ==
+          llvm::StringRef("ptrauth_struct_key"))
+        pauth_key =
+            die_child.GetAttributeValueAsOptionalUnsigned(DW_AT_const_value);
+      else if (die_child.GetAttributeValueAsString(DW_AT_name, nullptr) ==
+               llvm::StringRef("ptrauth_struct_disc"))
+        pauth_disc =
+            die_child.GetAttributeValueAsOptionalUnsigned(DW_AT_const_value);
+    }
+
+    // TODO: do we need some handling for one std::nullopt out of two?
+    if (pauth_key != std::nullopt && pauth_disc != std::nullopt) {
+      clang::ASTContext &ctx = m_ast.getASTContext();
+      llvm::APInt key_int = llvm::APInt(ctx.getTypeSize(ctx.UnsignedIntTy),
+                                        pauth_key.value(), false);
+      auto *key = clang::IntegerLiteral::Create(ctx, key_int, ctx.UnsignedIntTy,
+                                                clang::SourceLocation());
+      llvm::APInt disc_int = llvm::APInt(ctx.getTypeSize(ctx.UnsignedIntTy),
+                                         pauth_disc.value(), false);
+      auto *disc = clang::IntegerLiteral::Create(
+          ctx, disc_int, ctx.UnsignedIntTy, clang::SourceLocation());
+
+      clang::RecordDecl *record_decl = m_ast.GetAsRecordDecl(clang_type);
+      record_decl->addAttr(
+          clang::PointerAuthStructAttr::CreateImplicit(ctx, key, disc));
+    }
   }
 
   // Store a forward declaration to this class type in case any
diff --git a/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp b/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp
@@ -695,6 +695,143 @@ TEST_F(DWARFASTParserClangTests, TestVTablePtrAuthParsing) {
   ASSERT_EQ(attr->getCustomDiscriminationValue(), 42);
 }
 
+TEST_F(DWARFASTParserClangTests, TestPtrAuthStructAttr) {
+  // Tests parsing types with ptrauth_struct attribute
+  // authentication
+
+  // This is Dwarf for the following C code:
+  // ```
+  // struct [[clang::ptrauth_struct(2, 42)]] A {};
+  // struct A a;
+  // ```
+
+  const char *yamldata = R"(
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_AARCH64
+DWARF:
+  debug_str:
+    - a
+    - A
+    - ptrauth_struct_key
+    - ptrauth_struct_disc
+  debug_abbrev:
+    - ID:              0
+      Table:
+        - Code:            0x1
+          Tag:             DW_TAG_compile_unit
+          Children:        DW_CHILDREN_yes
+          Attributes:
+            - Attribute:       DW_AT_language
+              Form:            DW_FORM_data2
+        - Code:            0x2
+          Tag:             DW_TAG_variable
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+            - Attribute:       DW_AT_type
+              Form:            DW_FORM_ref4
+            - Attribute:       DW_AT_external
+              Form:            DW_FORM_flag_present
+        - Code:            0x3
+          Tag:             DW_TAG_structure_type
+          Children:        DW_CHILDREN_yes
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+        - Code:            0x4
+          Tag:             DW_TAG_LLVM_annotation
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+            - Attribute:       DW_AT_const_value
+              Form:            DW_FORM_udata
+
+  debug_info:
+    - Version:         5
+      UnitType:        DW_UT_compile
+      AddrSize:        8
+      Entries:
+# 0x0c: DW_TAG_compile_unit
+#         DW_AT_language [DW_FORM_data2]    (DW_LANG_C99)
+        - AbbrCode:        0x1
+          Values:
+            - Value:           0x0c
+
+# 0x0f:   DW_TAG_variable
+#           DW_AT_name [DW_FORM_strp]       (\"a\")
+#           DW_AT_type [DW_FORM_ref4]       (0x00000018 \"A\")
+#           DW_AT_external [DW_FORM_flag_present]   (true)
+        - AbbrCode:        0x2
+          Values:
+            - Value:           0x00
+            - Value:           0x18
+
+# 0x18:   DW_TAG_structure_type
+#           DW_AT_name [DW_FORM_strp]       (\"A\")
+        - AbbrCode:        0x3
+          Values:
+            - Value:           0x02
+
+# 0x1d:     DW_TAG_LLVM_annotation
+#             DW_AT_name [DW_FORM_strp]     (\"ptrauth_struct_key\")
+#             DW_AT_const_value [DW_FORM_udata]  (2)
+        - AbbrCode:        0x4
+          Values:
+            - Value:           0x04
+            - Value:           0x02
+
+# 0x23:     DW_TAG_LLVM_annotation
+#             DW_AT_name [DW_FORM_strp]     (\"ptrauth_struct_disc\")
+#             DW_AT_const_value [DW_FORM_udata]  (42)
+        - AbbrCode:        0x4
+          Values:
+            - Value:           0x17
+            - Value:           0x2a
+
+        - AbbrCode:        0x0 # end of child tags of 0x18
+        - AbbrCode:        0x0 # end of child tags of 0x0c
+...
+)";
+  YAMLModuleTester t(yamldata);
+
+  DWARFUnit *unit = t.GetDwarfUnit();
+  ASSERT_NE(unit, nullptr);
+  const DWARFDebugInfoEntry *cu_entry = unit->DIE().GetDIE();
+  ASSERT_EQ(cu_entry->Tag(), DW_TAG_compile_unit);
+  DWARFDIE cu_die(unit, cu_entry);
+
+  auto holder = std::make_unique<clang_utils::TypeSystemClangHolder>("ast");
+  auto &ast_ctx = *holder->GetAST();
+  DWARFASTParserClangStub ast_parser(ast_ctx);
+
+  DWARFDIE struct_object = cu_die.GetFirstChild();
+  ASSERT_EQ(struct_object.Tag(), DW_TAG_variable);
+  DWARFDIE structure_type =
+      struct_object.GetAttributeValueAsReferenceDIE(DW_AT_type);
+  ASSERT_EQ(structure_type.Tag(), DW_TAG_structure_type);
+
+  SymbolContext sc;
+  bool new_type = false;
+  lldb::TypeSP type =
+      ast_parser.ParseTypeFromDWARF(sc, structure_type, &new_type);
+  clang::RecordDecl *record_decl =
+      TypeSystemClang::GetAsRecordDecl(type->GetForwardCompilerType());
+  auto [is_key_val_independent, key] =
+      ast_ctx.getASTContext().getPointerAuthStructKey(record_decl);
+  auto [is_disc_val_independent, disc] =
+      ast_ctx.getASTContext().getPointerAuthStructDisc(record_decl);
+  ASSERT_TRUE(is_key_val_independent);
+  ASSERT_TRUE(is_disc_val_independent);
+  ASSERT_EQ(key, 2);
+  ASSERT_EQ(disc, 42);
+}
+
 struct ExtractIntFromFormValueTest : public testing::Test {
   SubsystemRAII<FileSystem, HostInfo> subsystems;
   clang_utils::TypeSystemClangHolder holder;
