Disable resilience for modules imported by the MemoryBuffer loader.

The MemoryBuffer loader is used by LLDB during debugging to import binary Swift
modules from .swift_ast sections. Modules imported from .swift_ast sections are
never produced from textual interfaces. By disabling resilience the expression
evaluator in the debugger can directly access private members.

rdar://79462915

Author: adrian-prantl

include/swift/AST/Module.h

@@ -257,6 +257,9 @@ class ModuleDecl
 
   AccessNotesFile accessNotes;
 
+  /// Used by the debugger to bypass resilient access to fields.
+  bool BypassResilience = false;
+
   ModuleDecl(Identifier name, ASTContext &ctx, ImplicitImportInfo importInfo);
 
 public:
@@ -290,6 +293,12 @@ class ModuleDecl
   AccessNotesFile &getAccessNotes() { return accessNotes; }
   const AccessNotesFile &getAccessNotes() const { return accessNotes; }
 
+  /// Return whether the module was imported with resilience disabled. The
+  /// debugger does this to access private fields.
+  bool getBypassResilience() const { return BypassResilience; }
+  /// Only to be called by MemoryBufferSerializedModuleLoader.
+  void setBypassResilience() { BypassResilience = true; }
+
   ArrayRef<FileUnit *> getFiles() {
     assert(!Files.empty() || failedToLoad());
     return Files;

include/swift/Serialization/SerializedModuleLoader.h

@@ -261,9 +261,11 @@ class MemoryBufferSerializedModuleLoader : public SerializedModuleLoaderBase {
   MemoryBufferSerializedModuleLoader(ASTContext &ctx,
                                      DependencyTracker *tracker,
                                      ModuleLoadingMode loadMode,
-                                     bool IgnoreSwiftSourceInfo)
+                                     bool IgnoreSwiftSourceInfo,
+                                     bool BypassResilience)
       : SerializedModuleLoaderBase(ctx, tracker, loadMode,
-                                   IgnoreSwiftSourceInfo) {}
+                                   IgnoreSwiftSourceInfo),
+        BypassResilience(BypassResilience) {}
 
   std::error_code findModuleFilesInDirectory(
       ImportPath::Element ModuleID,
@@ -279,6 +281,7 @@ class MemoryBufferSerializedModuleLoader : public SerializedModuleLoaderBase {
       StringRef moduleName,
       const SerializedModuleBaseName &BaseName) override;
 
+  bool BypassResilience;
 public:
   virtual ~MemoryBufferSerializedModuleLoader();
 
@@ -308,10 +311,10 @@ class MemoryBufferSerializedModuleLoader : public SerializedModuleLoaderBase {
   static std::unique_ptr<MemoryBufferSerializedModuleLoader>
   create(ASTContext &ctx, DependencyTracker *tracker = nullptr,
          ModuleLoadingMode loadMode = ModuleLoadingMode::PreferSerialized,
-         bool IgnoreSwiftSourceInfo = false) {
+         bool IgnoreSwiftSourceInfo = false, bool BypassResilience = false) {
     return std::unique_ptr<MemoryBufferSerializedModuleLoader>{
-        new MemoryBufferSerializedModuleLoader(ctx, tracker, loadMode,
-                                               IgnoreSwiftSourceInfo)};
+        new MemoryBufferSerializedModuleLoader(
+            ctx, tracker, loadMode, IgnoreSwiftSourceInfo, BypassResilience)};
   }
 };
 

lib/AST/Decl.cpp

@@ -1879,7 +1879,7 @@ static bool isDirectToStorageAccess(const DeclContext *UseDC,
   // If the storage is resilient, we cannot access it directly at all.
   if (var->isResilient(UseDC->getParentModule(),
                        UseDC->getResilienceExpansion()))
-    return false;
+    return var->getModuleContext()->getBypassResilience();
 
   if (isa<ConstructorDecl>(AFD) || isa<DestructorDecl>(AFD)) {
     // The access must also be a member access on 'self' in all language modes.

lib/IRGen/GenDecl.cpp

@@ -4968,7 +4968,10 @@ llvm::Constant *IRGenModule::getAddrOfGlobalUTF16String(StringRef utf8) {
 /// - For enums, new cases can be added
 /// - For classes, the superclass might change the size or number
 ///   of stored properties
-bool IRGenModule::isResilient(NominalTypeDecl *D, ResilienceExpansion expansion) {
+bool IRGenModule::isResilient(NominalTypeDecl *D,
+                              ResilienceExpansion expansion) {
+  if (D->getModuleContext()->getBypassResilience())
+    return false;
   if (expansion == ResilienceExpansion::Maximal &&
       Types.getLoweringMode() == TypeConverter::Mode::CompletelyFragile) {
     return false;

lib/SIL/Verifier/SILVerifier.cpp

@@ -104,6 +104,15 @@ static bool isArchetypeValidInFunction(ArchetypeType *A, const SILFunction *F) {
 
 namespace {
 
+/// When resilience is bypassed, direct access is legal, but the decls are still
+/// resilient.
+template <typename DeclType>
+bool checkResilience(DeclType *D, ModuleDecl *M,
+                     ResilienceExpansion expansion) {
+  return !D->getModuleContext()->getBypassResilience() &&
+         D->isResilient(M, expansion);
+}
+
 /// Metaprogramming-friendly base class.
 template <class Impl>
 class SILVerifierBase : public SILInstructionVisitor<Impl> {
@@ -234,7 +243,7 @@ void verifyKeyPathComponent(SILModule &M,
             "property decl should be a member of the base with the same type "
             "as the component");
     require(property->hasStorage(), "property must be stored");
-    require(!property->isResilient(M.getSwiftModule(), expansion),
+    require(!checkResilience(property, M.getSwiftModule(), expansion),
             "cannot access storage of resilient property");
     auto propertyTy =
         loweredBaseTy.getFieldType(property, M, typeExpansionContext);
@@ -1970,7 +1979,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
   void checkAllocGlobalInst(AllocGlobalInst *AGI) {
     SILGlobalVariable *RefG = AGI->getReferencedGlobal();
     if (auto *VD = RefG->getDecl()) {
-      require(!VD->isResilient(F.getModule().getSwiftModule(),
+      require(!checkResilience(VD, F.getModule().getSwiftModule(),
                                F.getResilienceExpansion()),
               "cannot access storage of resilient global");
     }
@@ -1989,7 +1998,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
         RefG->getLoweredTypeInContext(F.getTypeExpansionContext()),
         "global_addr/value must be the type of the variable it references");
     if (auto *VD = RefG->getDecl()) {
-      require(!VD->isResilient(F.getModule().getSwiftModule(),
+      require(!checkResilience(VD, F.getModule().getSwiftModule(),
                                F.getResilienceExpansion()),
               "cannot access storage of resilient global");
     }
@@ -2677,8 +2686,8 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     require(!structDecl->hasUnreferenceableStorage(),
             "Cannot build a struct with unreferenceable storage from elements "
             "using StructInst");
-    require(!structDecl->isResilient(F.getModule().getSwiftModule(),
-                                     F.getResilienceExpansion()),
+    require(!checkResilience(structDecl, F.getModule().getSwiftModule(),
+                             F.getResilienceExpansion()),
             "cannot access storage of resilient struct");
     require(SI->getType().isObject(),
             "StructInst must produce an object");
@@ -2879,8 +2888,8 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     require(cd, "Operand of dealloc_ref must be of class type");
 
     if (!DI->canAllocOnStack()) {
-      require(!cd->isResilient(F.getModule().getSwiftModule(),
-                              F.getResilienceExpansion()),
+      require(!checkResilience(cd, F.getModule().getSwiftModule(),
+                               F.getResilienceExpansion()),
               "cannot directly deallocate resilient class");
     }
   }
@@ -2996,7 +3005,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
             "result of struct_extract cannot be address");
     StructDecl *sd = operandTy.getStructOrBoundGenericStruct();
     require(sd, "must struct_extract from struct");
-    require(!sd->isResilient(F.getModule().getSwiftModule(),
+    require(!checkResilience(sd, F.getModule().getSwiftModule(),
                              F.getResilienceExpansion()),
             "cannot access storage of resilient struct");
     require(!EI->getField()->isStatic(),
@@ -3045,7 +3054,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
             "must derive struct_element_addr from address");
     StructDecl *sd = operandTy.getStructOrBoundGenericStruct();
     require(sd, "struct_element_addr operand must be struct address");
-    require(!sd->isResilient(F.getModule().getSwiftModule(),
+    require(!checkResilience(sd, F.getModule().getSwiftModule(),
                              F.getResilienceExpansion()),
             "cannot access storage of resilient struct");
     require(EI->getType().isAddress(),
@@ -3078,7 +3087,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     SILType operandTy = EI->getOperand()->getType();
     ClassDecl *cd = operandTy.getClassOrBoundGenericClass();
     require(cd, "ref_element_addr operand must be a class instance");
-    require(!cd->isResilient(F.getModule().getSwiftModule(),
+    require(!checkResilience(cd, F.getModule().getSwiftModule(),
                              F.getResilienceExpansion()),
             "cannot access storage of resilient class");
 
@@ -3102,7 +3111,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     SILType operandTy = RTAI->getOperand()->getType();
     ClassDecl *cd = operandTy.getClassOrBoundGenericClass();
     require(cd, "ref_tail_addr operand must be a class instance");
-    require(!cd->isResilient(F.getModule().getSwiftModule(),
+    require(!checkResilience(cd, F.getModule().getSwiftModule(),
                              F.getResilienceExpansion()),
             "cannot access storage of resilient class");
     require(cd, "ref_tail_addr operand must be a class instance");
@@ -3112,7 +3121,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     SILType operandTy = DSI->getOperand()->getType();
     StructDecl *sd = operandTy.getStructOrBoundGenericStruct();
     require(sd, "must struct_extract from struct");
-    require(!sd->isResilient(F.getModule().getSwiftModule(),
+    require(!checkResilience(sd, F.getModule().getSwiftModule(),
                              F.getResilienceExpansion()),
             "cannot access storage of resilient struct");
     if (F.hasOwnership()) {

lib/Serialization/SerializedModuleLoader.cpp

@@ -1205,6 +1205,11 @@ MemoryBufferSerializedModuleLoader::loadModule(SourceLoc importLoc,
   if (!file)
     return nullptr;
 
+  // The MemoryBuffer loader is used by LLDB during debugging. Modules imported
+  // from .swift_ast sections are never produced from textual interfaces. By
+  // disabling resilience the debugger can directly access private members.
+  if (BypassResilience)
+    M->setBypassResilience();
   M->addFile(*file);
   Ctx.addLoadedModule(M);
   return M;