IRGen: Sign function pointers passed to swift_(store/get)EnumTagSinglePayloadGeneric calls

rdar://100129824

Author: aschwaighofer

include/swift/ABI/MetadataValues.h

@@ -1436,6 +1436,12 @@ namespace SpecialPointerAuthDiscriminators {
 
   /// Functions accessible at runtime (i.e. distributed method accessors).
   const uint16_t AccessibleFunctionRecord = 0x438c; // = 17292
+
+  /// C type GetExtraInhabitantTag function descriminator
+  const uint16_t GetExtraInhabitantTagFunction = 0x392e; // = 14638
+
+  /// C type StoreExtraInhabitantTag function descriminator
+  const uint16_t StoreExtraInhabitantTagFunction = 0x9bf6; // = 39926
 }
 
 /// The number of arguments that will be passed directly to a generic

include/swift/AST/IRGenOptions.h

@@ -198,6 +198,12 @@ struct PointerAuthOptions : clang::PointerAuthOptions {
 
   /// Non-unique extended existential type shapes in flight.
   PointerAuthSchema NonUniqueExtendedExistentialTypeShape;
+
+  /// C type GetExtraInhabitantTag function descriminator.
+  PointerAuthSchema GetExtraInhabitantTagFunction;
+
+  /// C type StoreExtraInhabitantTag function descriminator.
+  PointerAuthSchema StoreExtraInhabitantTagFunction;
 };
 
 enum class JITDebugArtifact : unsigned {

lib/IRGen/GenOpaque.cpp

@@ -1269,8 +1269,13 @@ irgen::emitGetEnumTagSinglePayloadGenericCall(IRGenFunction &IGF,
   auto getExtraInhabitantTagFn =
     getOrCreateGetExtraInhabitantTagFunction(IGF.IGM, payloadType,
                                              payloadTI, emitter);
-  getExtraInhabitantTagFn =
-    IGF.IGM.getConstantSignedCFunctionPointer(getExtraInhabitantTagFn);      
+  // Sign the getExtraInhabitantTag function with the C function pointer schema.
+  if (auto schema = IGF.IGM.getOptions().PointerAuth.FunctionPointers) {
+    if (schema.hasOtherDiscrimination())
+      schema = IGF.IGM.getOptions().PointerAuth.GetExtraInhabitantTagFunction;
+    getExtraInhabitantTagFn = IGF.IGM.getConstantSignedPointer(
+        getExtraInhabitantTagFn, schema, PointerAuthEntity(), nullptr);
+  }
 
   // We assume this is never a reabstracted type.
   auto type = payloadType.getASTType();
@@ -1344,8 +1349,14 @@ irgen::emitStoreEnumTagSinglePayloadGenericCall(IRGenFunction &IGF,
   auto storeExtraInhabitantTagFn =
     getOrCreateStoreExtraInhabitantTagFunction(IGF.IGM, payloadType,
                                                payloadTI, emitter);
-  storeExtraInhabitantTagFn =
-    IGF.IGM.getConstantSignedCFunctionPointer(storeExtraInhabitantTagFn);      
+
+  // Sign the getExtraInhabitantTag function with the C function pointer schema.
+  if (auto schema = IGF.IGM.getOptions().PointerAuth.FunctionPointers) {
+    if (schema.hasOtherDiscrimination())
+      schema = IGF.IGM.getOptions().PointerAuth.StoreExtraInhabitantTagFunction;
+    storeExtraInhabitantTagFn = IGF.IGM.getConstantSignedPointer(
+        storeExtraInhabitantTagFn, schema, PointerAuthEntity(), nullptr);
+  }
 
   // We assume this is never a reabstracted type.
   auto type = payloadType.getASTType();

lib/IRGen/IRGen.cpp

@@ -998,6 +998,14 @@ static void setPointerAuthOptions(PointerAuthOptions &opts,
   opts.ClangTypeTaskContinuationFunction = PointerAuthSchema(
       codeKey, /*address*/ false, Discrimination::Constant,
       SpecialPointerAuthDiscriminators::ClangTypeTaskContinuationFunction);
+
+  opts.GetExtraInhabitantTagFunction = PointerAuthSchema(
+      codeKey, /*address*/ false, Discrimination::Constant,
+      SpecialPointerAuthDiscriminators::GetExtraInhabitantTagFunction);
+
+  opts.StoreExtraInhabitantTagFunction = PointerAuthSchema(
+      codeKey, /*address*/ false, Discrimination::Constant,
+      SpecialPointerAuthDiscriminators::StoreExtraInhabitantTagFunction);
 }
 
 std::unique_ptr<llvm::TargetMachine>