CHERIoT-Platform · xdoardo · Jun 5, 2025
diff --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
@@ -4648,6 +4648,12 @@ def CheriConditionalSeal : Builtin {
   let Prototype = "void* __capability(void const* __capability,void const* __capability)";
 }
 
+def CHERIoTEmitSealingType : Builtin {
+  let Spellings = ["__builtin_cheriot_sealing_type"];
+  let Attributes = [NoThrow, Const, CustomTypeChecking, Constexpr];
+  let Prototype = "void*(...)";
+}
+
 // Safestack builtins.
 def GetUnsafeStackStart : Builtin {
   let Spellings = ["__builtin___get_unsafe_stack_start"];

diff --git a/clang/include/clang/Basic/TokenKinds.def b/clang/include/clang/Basic/TokenKinds.def
@@ -356,6 +356,7 @@ KEYWORD(__cheri_input               , KEYALL)
 
 // CHERIoT Predefine Expr
 KEYWORD(__cheriot_minimum_stack__   , KEYALL)
+KEYWORD(__builtin_cheriot_sealing_type 	, KEYALL)
 
 // Cheriot Qualifiers
 KEYWORD(__sealed_capability         , KEYALL)

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -6155,6 +6155,51 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     return RValue::get(Builder.CreateIntrinsic(
         llvm::Intrinsic::cheri_cap_perms_check, {SizeTy}, {Cap, Perms}));
   }
+  case Builtin::BI__builtin_cheriot_sealing_type: {
+    const Expr *Callee = E->getCallee();
+    Callee = Callee->IgnoreImplicit();
+
+    const auto *DeclRef = dyn_cast<DeclRefExpr>(Callee);
+    assert(DeclRef && "DeclRef to built-in callee can't be null!");
+    assert(DeclRef->getTemplateArgs() &&
+           "template type in built-in callee can't be null!");
+
+    const auto SealingType =
+        DeclRef->getTemplateArgs()->getArgument().getAsType();
+    auto CompartmentName = getLangOpts().CheriCompartmentName;
+
+    clang::PrintingPolicy policy(getLangOpts());
+    policy.SuppressTagKeyword = true;
+    policy.SuppressElaboration = true;
+    policy.SuppressCapabilityQualifier = true;
+
+    std::string SealingTypeName = SealingType.getAsString(policy);
+    SealingTypeName.erase(
+        std::remove_if(SealingTypeName.begin(), SealingTypeName.end(), isspace),
+        SealingTypeName.end());
+
+    auto PrefixedImportName =
+        CHERIoTSealingKeyTypeAttr::getSealingTypeSymbolName(CompartmentName,
+                                                            SealingTypeName);
+    auto *Mod = &CGM.getModule();
+    auto MangledImportName = "__import." + PrefixedImportName;
+    auto *GV = Mod->getGlobalVariable(MangledImportName);
+
+    if (!GV) {
+      // llvm::StructType* opaqueType =
+      // llvm::StructType::create(CGM.getModule().getContext(), "");
+      auto *opaquePtrType =
+          llvm::PointerType::getUnqual(CGM.getModule().getContext());
+      GV = new GlobalVariable(CGM.getModule(), opaquePtrType, true,
+                              GlobalValue::ExternalLinkage, nullptr,
+                              MangledImportName);
+      GV->addAttribute(CHERIoTSealingKeyTypeAttr::getAttrName(),
+                       PrefixedImportName);
+      GV->addAttribute("cheri-compartment", CompartmentName);
+    }
+
+    return RValue::get(GV);
+  }
   // Round to capability precision:
   // TODO: should we handle targets that don't have any precision constraints
   // here or in the backend?

diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
@@ -1201,6 +1201,67 @@ ExprResult Parser::ParseCastExpression(CastParseKind ParseKind,
     return ParseCastExpression(ParseKind, isAddressOfOperand, isTypeCast,
                                isVectorLiteral, NotPrimaryExpression);
 
+  case tok::kw___builtin_cheriot_sealing_type: {
+    // We expect: `__builtin_cheriot_sealing_type<TYPENAME>()`.
+    auto KWLoc = Tok.getLocation();
+    ConsumeToken();
+    auto LAngleLoc = Tok.getLocation();
+    if (ExpectAndConsume(tok::less)) {
+      SkipUntil(tok::r_paren, StopAtSemi);
+      return ExprError();
+    }
+
+    auto TyArgLoc = Tok.getLocation();
+    TypeResult TyArg = ParseTypeName();
+    if (TyArg.isInvalid())
+      return ExprError();
+
+    TypeSourceInfo *SealingTypeInfo = nullptr;
+    QualType SealingType =
+        Actions.GetTypeFromParser(TyArg.get(), &SealingTypeInfo);
+
+    auto RAngleLoc = Tok.getLocation();
+    if (ExpectAndConsume(tok::greater)) {
+      SkipUntil(tok::r_paren, StopAtSemi);
+      return ExprError();
+    }
+
+    if (ExpectAndConsume(tok::l_paren)) {
+      SkipUntil(tok::r_paren, StopAtSemi);
+      return ExprError();
+    }
+
+    SourceLocation RParenLoc = Tok.getLocation();
+    if (ExpectAndConsume(tok::r_paren)) {
+      SkipUntil(tok::semi, StopAtSemi);
+      return ExprError();
+    }
+
+    auto *Ctxt = &Actions.getASTContext();
+    auto BuiltinID = clang::Builtin::BI__builtin_cheriot_sealing_type;
+
+    auto BuiltinName = Ctxt->BuiltinInfo.getName(BuiltinID);
+    IdentifierInfo *II = &Ctxt->Idents.get(BuiltinName);
+    LookupResult R(Actions, II, SourceLocation(), Sema::LookupOrdinaryName);
+    if (!Actions.LookupBuiltin(R)) {
+      return ExprError();
+    }
+
+    FunctionDecl *BuiltinDecl = dyn_cast<FunctionDecl>(R.getFoundDecl());
+    TemplateArgument Arg(SealingType);
+    TemplateArgumentListInfo TArgs(LAngleLoc, RAngleLoc);
+
+    TArgs.addArgument(TemplateArgumentLoc(
+        Arg, Ctxt->getTrivialTypeSourceInfo(SealingType, TyArgLoc)));
+
+    DeclRefExpr *FnRef = DeclRefExpr::Create(
+        *Ctxt, NestedNameSpecifierLoc(), SourceLocation(), BuiltinDecl, false,
+        KWLoc, BuiltinDecl->getType(), VK_LValue, R.getFoundDecl(), &TArgs);
+
+    return CallExpr::Create(*Ctxt, FnRef, {}, BuiltinDecl->getReturnType(),
+                            clang::ExprValueKind::VK_PRValue, RParenLoc,
+                            FPOptionsOverride());
+  }
   case tok::identifier:
   ParseIdentifier: {    // primary-expression: identifier
                         // unqualified-id: identifier

diff --git a/clang/test/CodeGen/cheri/riscv/cheriot-emit-sealed-builtin.c b/clang/test/CodeGen/cheri/riscv/cheriot-emit-sealed-builtin.c
@@ -0,0 +1,56 @@
+// RUN: %clang_cc1 %s -o - "-triple" "riscv32cheriot-unknown-unknown-cheriotrtos" "-emit-llvm" "-cheri-compartment=static_sealing_test" "-mframe-pointer=none" "-mcmodel=small" "-target-abi" "cheriot" "-O0" "-Werror" -std=c2x | FileCheck %s
+
+
+struct StructSealingKey { };
+enum EnumSealingKey { SEALING_KEY_KIND1, SEALING_KEY_KIND2 };
+typedef enum EnumSealingKey TypeDefSealingKey;
+
+// CHECK: @__import.sealing_type.static_sealing_test.StructSealingKey = external addrspace(200) constant ptr #0
+// CHECK: @__import.sealing_type.static_sealing_test.EnumSealingKey = external addrspace(200) constant ptr #1
+// CHECK: @__import.sealing_type.static_sealing_test.TypeDefSealingKey = external addrspace(200) constant ptr #2
+// CHECK: @__import.sealing_type.static_sealing_test.int = external addrspace(200) constant ptr #3
+// CHECK: @"__import.sealing_type.static_sealing_test.int*" = external addrspace(200) constant ptr #4
+
+// CHECK: define dso_local void @func() addrspace(200) #5 {
+void func() {
+
+// CHECK: entry:
+// CHECK:  %SealingKey1 = alloca ptr addrspace(200), align 8, addrspace(200)
+// CHECK:  %SealingKey2 = alloca ptr addrspace(200), align 8, addrspace(200)
+// CHECK:  %SealingKey3 = alloca ptr addrspace(200), align 8, addrspace(200)
+// CHECK:  %SealingKey4 = alloca ptr addrspace(200), align 8, addrspace(200)
+// CHECK:  %SealingKey5 = alloca ptr addrspace(200), align 8, addrspace(200)
+// CHECK:  %SealingKey6 = alloca ptr addrspace(200), align 8, addrspace(200)
+// CHECK:  %SealingKey7 = alloca ptr addrspace(200), align 8, addrspace(200)
+// CHECK:  %SealingKey8 = alloca ptr addrspace(200), align 8, addrspace(200)
+
+// CHECK:  store ptr addrspace(200) @__import.sealing_type.static_sealing_test.StructSealingKey, ptr addrspace(200) %SealingKey1, align 8
+  struct StructSealingKey *SealingKey1 = __builtin_cheriot_sealing_type<struct StructSealingKey>();
+
+// CHECK:  store ptr addrspace(200) @__import.sealing_type.static_sealing_test.EnumSealingKey, ptr addrspace(200) %SealingKey2, align 8
+  enum EnumSealingKey *SealingKey2 = __builtin_cheriot_sealing_type<enum EnumSealingKey>();
+
+// CHECK:  store ptr addrspace(200) @__import.sealing_type.static_sealing_test.TypeDefSealingKey, ptr addrspace(200) %SealingKey3, align 8
+  TypeDefSealingKey *SealingKey3 = __builtin_cheriot_sealing_type<TypeDefSealingKey>();
+
+// CHECK:  store ptr addrspace(200) @__import.sealing_type.static_sealing_test.int, ptr addrspace(200) %SealingKey4, align 8
+  int *SealingKey4 = __builtin_cheriot_sealing_type<int>();
+
+// CHECK:  store ptr addrspace(200) @"__import.sealing_type.static_sealing_test.int*", ptr addrspace(200) %SealingKey5, align 8
+  int **SealingKey5 = __builtin_cheriot_sealing_type<int*>();
+
+// CHECK:  store ptr addrspace(200) @__import.sealing_type.static_sealing_test.int, ptr addrspace(200) %SealingKey6, align 8
+  int *SealingKey6 = __builtin_cheriot_sealing_type<int>();
+// CHECK:  store ptr addrspace(200) @__import.sealing_type.static_sealing_test.int, ptr addrspace(200) %SealingKey7, align 8
+  int *SealingKey7 = __builtin_cheriot_sealing_type<int>();
+// CHECK:  store ptr addrspace(200) @__import.sealing_type.static_sealing_test.int, ptr addrspace(200) %SealingKey8, align 8
+  int *SealingKey8 = __builtin_cheriot_sealing_type<int>();
+
+// CHECK: ret void
+}
+
+// CHECK: attributes #0 = { "cheri-compartment"="static_sealing_test" "cheriot_sealing_key"="sealing_type.static_sealing_test.StructSealingKey" }
+// CHECK: attributes #1 = { "cheri-compartment"="static_sealing_test" "cheriot_sealing_key"="sealing_type.static_sealing_test.EnumSealingKey" }
+// CHECK: attributes #2 = { "cheri-compartment"="static_sealing_test" "cheriot_sealing_key"="sealing_type.static_sealing_test.TypeDefSealingKey" }
+// CHECK: attributes #3 = { "cheri-compartment"="static_sealing_test" "cheriot_sealing_key"="sealing_type.static_sealing_test.int" }
+// CHECK: attributes #4 = { "cheri-compartment"="static_sealing_test" "cheriot_sealing_key"="sealing_type.static_sealing_test.int*" }
diff --git a/llvm/include/llvm/IR/Attributes.h b/llvm/include/llvm/IR/Attributes.h
@@ -1612,6 +1612,23 @@ class CHERIoTSealedValueAttr {
   /// Get the name of the attribute.
   static const std::string getAttrName() { return "cheriot_sealed_value"; }
 };
+
+/// Represents the LLVM-level attribute that is used to signal
+/// that a global (variable) represents a sealing key type.
+class CHERIoTSealingKeyTypeAttr {
+public:
+  /// Get the name of the attribute.
+  static const std::string getAttrName() { return "cheriot_sealing_key"; }
+
+  /// Get the mangled name of the symbol representing the sealing key.
+  static const std::string
+  getSealingTypeSymbolName(StringRef CompartmentName,
+                           StringRef SealingKeyTypeName) {
+    return "sealing_type." + CompartmentName.str() + "." +
+           SealingKeyTypeName.str();
+  }
+};
+
 } // end namespace llvm
 
 #endif // LLVM_IR_ATTRIBUTES_H