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

kovdan01 · kovdan01 · commit 08567dbd3d0d · 2024-02-12T15:38:12.000+03:00
- Encode the attribute in Dwarf as a `DW_TAG_LLVM_ptrauth_type` entry
  corresponding to vtable pointer. The attribute supports "default"
  values for address and extra discrimination, but in Dwarf we emit
  actual values due to `DW_AT_LLVM_ptrauth_*` attributes limitations. See
  lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp for details.

- When parsing dynamic class and structure types from Dwarf, check the
  vtable pointer type against `DW_TAG_LLVM_ptrauth_type`. If true, apply
  the `clang::ptrauth_vtable_pointer` attribute with corresponding
  parameters to the class record decl. "Default" address and extra
  discrimination values are not restored, the actual ones are, but the
  result is effectively the same since the signing schema must be
  preserved unchanged.
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -2432,6 +2432,47 @@ void CGDebugInfo::CollectVTableInfo(const CXXRecordDecl *RD, llvm::DIFile *Unit,
   if (!VPtrTy)
     VPtrTy = getOrCreateVTablePtrType(Unit);
 
+  if (auto *VptrAuthAttr = RD->getAttr<VTablePointerAuthenticationAttr>()) {
+    unsigned TypedDiscriminator =
+        CGM.getContext().getPointerAuthVTablePointerDiscriminator(RD);
+    auto &LangOpts = CGM.getContext().getLangOpts();
+
+    unsigned Key = VptrAuthAttr->getKey();
+
+    bool HasAddressDiscrimination =
+        LangOpts.PointerAuthVTPtrAddressDiscrimination;
+    if (VptrAuthAttr->getAddressDiscrimination() !=
+        VTablePointerAuthenticationAttr::DefaultAddressDiscrimination) {
+      HasAddressDiscrimination =
+          (VptrAuthAttr->getAddressDiscrimination() ==
+           VTablePointerAuthenticationAttr::AddressDiscrimination);
+    }
+
+    unsigned ExtraDiscriminator = 0;
+
+    switch (VptrAuthAttr->getExtraDiscrimination()) {
+    case VTablePointerAuthenticationAttr::DefaultExtraDiscrimination:
+      if (LangOpts.PointerAuthVTPtrTypeDiscrimination)
+        ExtraDiscriminator = TypedDiscriminator;
+      break;
+    case VTablePointerAuthenticationAttr::TypeDiscrimination:
+      ExtraDiscriminator = TypedDiscriminator;
+      break;
+    case VTablePointerAuthenticationAttr::CustomDiscrimination:
+      ExtraDiscriminator = VptrAuthAttr->getCustomDiscriminationValue();
+      break;
+    case VTablePointerAuthenticationAttr::NoExtraDiscrimination:
+      break;
+    }
+
+    // See CodeGenModule::computeVTPointerAuthentication:
+    // isIsaPointer and authenticatesNullValues are always false.
+    VPtrTy = DBuilder.createPtrAuthQualifiedType(
+        VPtrTy, Key, HasAddressDiscrimination, ExtraDiscriminator,
+        /* isIsaPointer */ false,
+        /* authenticatesNullValues */ false);
+  }
+
   unsigned Size = CGM.getContext().getTypeSize(CGM.getContext().VoidPtrTy);
   llvm::DIType *VPtrMember =
       DBuilder.createMemberType(Unit, getVTableName(RD), Unit, 0, Size, 0, 0,
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -1842,6 +1842,48 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
           attrs.name.GetCString(), tag_decl_kind, attrs.class_language,
           &metadata, attrs.exports_symbols);
     }
+
+    if (metadata.GetIsDynamicCXXType()) {
+      clang::RecordDecl *record_decl = m_ast.GetAsRecordDecl(clang_type);
+      DWARFDIE vptr_type_die =
+          die.GetFirstChild().GetAttributeValueAsReferenceDIE(DW_AT_type);
+      if (vptr_type_die.Tag() == DW_TAG_LLVM_ptrauth_type) {
+        unsigned key = vptr_type_die.GetAttributeValueAsUnsigned(
+            DW_AT_LLVM_ptrauth_key, -1);
+        unsigned discriminator = vptr_type_die.GetAttributeValueAsUnsigned(
+            DW_AT_LLVM_ptrauth_extra_discriminator, -1);
+        unsigned has_addr_discr = vptr_type_die.GetAttributeValueAsUnsigned(
+            DW_AT_LLVM_ptrauth_address_discriminated, -1);
+
+        auto error_missing = [&vptr_type_die](const dw_attr_t attr) {
+          vptr_type_die.GetDWARF()->GetObjectFile()->GetModule()->ReportError(
+              "[{0:x16}]: missing attribute {1:x4} ({2}) required for signed "
+              "vtable pointer",
+              vptr_type_die.GetOffset(), attr, DW_AT_value_to_name(attr));
+        };
+
+        if (key == unsigned(-1))
+          error_missing(DW_AT_LLVM_ptrauth_key);
+        if (discriminator == unsigned(-1))
+          error_missing(DW_AT_LLVM_ptrauth_extra_discriminator);
+        if (has_addr_discr == unsigned(-1))
+          error_missing(DW_AT_LLVM_ptrauth_extra_discriminator);
+
+        record_decl->addAttr(
+            clang::VTablePointerAuthenticationAttr::CreateImplicit(
+                m_ast.getASTContext(),
+                key == 2
+                    ? clang::VTablePointerAuthenticationAttr::ProcessDependent
+                    : clang::VTablePointerAuthenticationAttr::
+                          ProcessIndependent,
+                has_addr_discr ? clang::VTablePointerAuthenticationAttr::
+                                     AddressDiscrimination
+                               : clang::VTablePointerAuthenticationAttr::
+                                     NoAddressDiscrimination,
+                clang::VTablePointerAuthenticationAttr::CustomDiscrimination,
+                discriminator));
+      }
+    }
   }
 
   // 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
@@ -420,6 +420,281 @@ TEST_F(DWARFASTParserClangTests, TestPtrAuthParsing) {
   ASSERT_EQ(type_as_string, "void (*__ptrauth(0,0,42))(...)");
 }
 
+TEST_F(DWARFASTParserClangTests, TestVTablePtrAuthParsing) {
+  // Tests parsing dynamic structure types with explicit vtable pointer
+  // authentication
+
+  // This is Dwarf for the following C++ code:
+  // ```
+  // struct [[clang::ptrauth_vtable_pointer(process_dependent,
+  //                                        address_discrimination,
+  //                                        custom_discrimination, 42)]] A {
+  //   virtual void foo() {}
+  // };
+  // A a;
+  // ```
+
+  const char *yamldata = R"(
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_AARCH64
+DWARF:
+  debug_str:
+    - a
+    - A
+    - _vptr$A
+    - foo
+    - __vtbl_ptr_type
+    - int
+  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_containing_type
+              Form:            DW_FORM_ref4
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+        - Code:            0x4
+          Tag:             DW_TAG_member
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+            - Attribute:       DW_AT_type
+              Form:            DW_FORM_ref4
+            - Attribute:       DW_AT_artificial
+              Form:            DW_FORM_flag_present
+        - Code:            0x5
+          Tag:             DW_TAG_subprogram
+          Children:        DW_CHILDREN_yes
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+            - Attribute:       DW_AT_virtuality
+              Form:            DW_FORM_data1
+            - Attribute:       DW_AT_containing_type
+              Form:            DW_FORM_ref4
+        - Code:            0x6
+          Tag:             DW_TAG_formal_parameter
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_type
+              Form:            DW_FORM_ref4
+            - Attribute:       DW_AT_artificial
+              Form:            DW_FORM_flag_present
+        - Code:            0x7
+          Tag:             DW_TAG_LLVM_ptrauth_type
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_type
+              Form:            DW_FORM_ref4
+            - Attribute:       DW_AT_LLVM_ptrauth_key
+              Form:            DW_FORM_data1
+            - Attribute:       DW_AT_LLVM_ptrauth_extra_discriminator
+              Form:            DW_FORM_data2
+            - Attribute:       DW_AT_LLVM_ptrauth_address_discriminated
+              Form:            DW_FORM_flag_present
+        - Code:            0x8
+          Tag:             DW_TAG_pointer_type
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_type
+              Form:            DW_FORM_ref4
+        - Code:            0x9
+          Tag:             DW_TAG_pointer_type
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_type
+              Form:            DW_FORM_ref4
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+        - Code:            0xA
+          Tag:             DW_TAG_subroutine_type
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_type
+              Form:            DW_FORM_ref4
+        - Code:            0xB
+          Tag:             DW_TAG_base_type
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+            - Attribute:       DW_AT_encoding
+              Form:            DW_FORM_data1
+            - Attribute:       DW_AT_byte_size
+              Form:            DW_FORM_data1
+        - Code:            0xC
+          Tag:             DW_TAG_pointer_type
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_type
+              Form:            DW_FORM_ref4
+
+  debug_info:
+    - Version:         5
+      UnitType:        DW_UT_compile
+      AddrSize:        8
+      Entries:
+# 0x0c: DW_TAG_compile_unit
+#         DW_AT_language [DW_FORM_data2]    (DW_LANG_C_plus_plus_11)
+        - AbbrCode:        0x1
+          Values:
+            - Value:           0x1A
+
+# 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_containing_type [DW_FORM_ref4]    (0x00000018 \"A\")
+#           DW_AT_name [DW_FORM_strp]       (\"A\")
+        - AbbrCode:        0x3
+          Values:
+            - Value:           0x18
+            - Value:           0x02
+
+# 0x21:     DW_TAG_member
+#             DW_AT_name [DW_FORM_strp]     (\"_vptr$A\")
+#             DW_AT_type [DW_FORM_ref4]     (0x0000002f)
+#             DW_AT_artificial [DW_FORM_flag_present]       (true)
+        - AbbrCode:        0x4
+          Values:
+            - Value:           0x04
+            - Value:           0x3B
+
+# 0x2a:     DW_TAG_subprogram
+#             DW_AT_name [DW_FORM_strp]     (\"foo\")
+#             DW_AT_virtuality [DW_FORM_data1]      (DW_VIRTUALITY_virtual)
+#             DW_AT_containing_type [DW_FORM_ref4]  (0x00000018 \"A\")
+        - AbbrCode:        0x5
+          Values:
+            - Value:           0x0C
+            - Value:           0x01
+            - Value:           0x18
+
+# 0x34:       DW_TAG_formal_parameter
+#               DW_AT_type [DW_FORM_ref4]   (0x0000005d \"A *\")
+#               DW_AT_artificial [DW_FORM_flag_present]     (true)
+        - AbbrCode:        0x6
+          Values:
+            - Value:           0x5D
+
+        - AbbrCode:        0x0 # end of child tags of 0x2a
+        - AbbrCode:        0x0 # end of child tags of 0x18
+
+# 0x3b:   DW_TAG_LLVM_ptrauth_type
+#           DW_AT_type [DW_FORM_ref4]       (0x00000043 \"int (**)()\")
+#           DW_AT_LLVM_ptrauth_key [DW_FORM_data1]  (0x02)
+#           DW_AT_LLVM_ptrauth_extra_discriminator [DW_FORM_data2]  (0x002a)
+#           DW_AT_LLVM_ptrauth_address_discriminated [DW_FORM_flag_present] (true)
+        - AbbrCode:        0x7
+          Values:
+            - Value:           0x43
+            - Value:           0x02
+            - Value:           0x2A
+
+# 0x43:   DW_TAG_pointer_type
+#           DW_AT_type [DW_FORM_ref4]       (0x00000048 \"int (*)()\")
+        - AbbrCode:        0x8
+          Values:
+            - Value:           0x48
+
+# 0x48:   DW_TAG_pointer_type
+#           DW_AT_type [DW_FORM_ref4]       (0x00000051 \"int ()\")
+#           DW_AT_name [DW_FORM_strp]       (\"__vtbl_ptr_type\")
+        - AbbrCode:        0x9
+          Values:
+            - Value:           0x51
+            - Value:           0x10
+
+# 0x51:   DW_TAG_subroutine_type
+#           DW_AT_type [DW_FORM_ref4]       (0x00000056 \"int\")
+        - AbbrCode:        0xA
+          Values:
+            - Value:           0x56
+
+# 0x56:   DW_TAG_base_type
+#           DW_AT_name [DW_FORM_strp]       (\"int\")
+#           DW_AT_encoding [DW_FORM_data1]  (DW_ATE_signed)
+#           DW_AT_byte_size [DW_FORM_data1] (0x04)
+        - AbbrCode:        0xB
+          Values:
+            - Value:           0x20
+            - Value:           0x05
+            - Value:           0x04
+
+# 0x5d:   DW_TAG_pointer_type
+#           DW_AT_type [DW_FORM_ref4]       (0x00000018 \"A\")
+        - AbbrCode:        0xC
+          Values:
+            - Value:           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 *attr = record_decl->getAttr<clang::VTablePointerAuthenticationAttr>();
+  ASSERT_NE(attr, nullptr);
+  ASSERT_EQ(attr->getKey(),
+            clang::VTablePointerAuthenticationAttr::ProcessDependent);
+  ASSERT_EQ(attr->getAddressDiscrimination(),
+            clang::VTablePointerAuthenticationAttr::AddressDiscrimination);
+  ASSERT_EQ(attr->getExtraDiscrimination(),
+            clang::VTablePointerAuthenticationAttr::CustomDiscrimination);
+  ASSERT_EQ(attr->getCustomDiscriminationValue(), 42);
+}
+
 struct ExtractIntFromFormValueTest : public testing::Test {
   SubsystemRAII<FileSystem, HostInfo> subsystems;
   clang_utils::TypeSystemClangHolder holder;
