Index: lldb/include/lldb/API/SBDebugger.h
===================================================================
--- lldb/include/lldb/API/SBDebugger.h
+++ lldb/include/lldb/API/SBDebugger.h
@@ -14,6 +14,10 @@
 #include "lldb/API/SBDefines.h"
 #include "lldb/API/SBPlatform.h"
 
+namespace lldb_private {
+struct SystemInitializerOptions;
+}
+
 namespace lldb {
 
 class LLDB_API SBInputReader {
@@ -31,6 +35,18 @@
   bool IsActive() const;
 };
 
+class LLDB_API SBInitializationOptions {
+public:
+  SBInitializationOptions();
+  ~SBInitializationOptions();
+
+  void SetVFSOverlay(const char *overlay);
+
+private:
+  friend class lldb::SBDebugger;
+  std::unique_ptr<lldb_private::SystemInitializerOptions> m_opaque_up;
+};
+
 class LLDB_API SBDebugger {
 public:
   FLAGS_ANONYMOUS_ENUM(){eBroadcastBitProgress = (1 << 0)};
@@ -84,6 +100,8 @@
   static void Initialize();
 
   static lldb::SBError InitializeWithErrorHandling();
+  static lldb::SBError
+  InitializeWithErrorHandling(const SBInitializationOptions &options);
 
   static void Terminate();
 
Index: lldb/include/lldb/API/SBDefines.h
===================================================================
--- lldb/include/lldb/API/SBDefines.h
+++ lldb/include/lldb/API/SBDefines.h
@@ -48,6 +48,7 @@
 class LLDB_API SBFrame;
 class LLDB_API SBFunction;
 class LLDB_API SBHostOS;
+class LLDB_API SBInitializationOptions;
 class LLDB_API SBInstruction;
 class LLDB_API SBInstructionList;
 class LLDB_API SBLanguageRuntime;
Index: lldb/include/lldb/Initialization/SystemInitializerCommon.h
===================================================================
--- lldb/include/lldb/Initialization/SystemInitializerCommon.h
+++ lldb/include/lldb/Initialization/SystemInitializerCommon.h
@@ -13,6 +13,12 @@
 #include "lldb/Host/HostInfo.h"
 
 namespace lldb_private {
+struct SystemInitializerOptions {
+  /// Overlay the virtual filesystem described by file over the real file
+  /// system.
+  FileSpec vfs_overlay;
+};
+
 /// Initializes common lldb functionality.
 ///
 /// This class is responsible for initializing a subset of lldb
@@ -23,7 +29,8 @@
 /// the constructor.
 class SystemInitializerCommon : public SystemInitializer {
 public:
-  SystemInitializerCommon(HostInfo::SharedLibraryDirectoryHelper *helper);
+  SystemInitializerCommon(HostInfo::SharedLibraryDirectoryHelper *helper,
+                          SystemInitializerOptions = {});
   ~SystemInitializerCommon() override;
 
   llvm::Error Initialize() override;
@@ -31,6 +38,7 @@
 
 private:
   HostInfo::SharedLibraryDirectoryHelper *m_shlib_dir_helper;
+  SystemInitializerOptions m_options;
 };
 
 } // namespace lldb_private
Index: lldb/source/API/SBDebugger.cpp
===================================================================
--- lldb/source/API/SBDebugger.cpp
+++ lldb/source/API/SBDebugger.cpp
@@ -127,6 +127,22 @@
   return false;
 }
 
+SBInitializationOptions::SBInitializationOptions()
+    : m_opaque_up(std::make_unique<SystemInitializerOptions>()) {
+  LLDB_RECORD_CONSTRUCTOR_NO_ARGS(SBInitializationOptions);
+}
+
+SBInitializationOptions::~SBInitializationOptions() {}
+
+// We can't use an SBFileSpec as the argument, because that will try to use
+// the FileSystem before it's initialized.
+void SBInitializationOptions::SetVFSOverlay(const char *overlay) {
+  LLDB_RECORD_METHOD(void, SBInitializationOptions, SetVFSOverlay,
+                     (const char *), overlay);
+
+  m_opaque_up->vfs_overlay = FileSpec(overlay);
+}
+
 SBDebugger::SBDebugger() { LLDB_RECORD_CONSTRUCTOR_NO_ARGS(SBDebugger); }
 
 SBDebugger::SBDebugger(const lldb::DebuggerSP &debugger_sp)
@@ -202,6 +218,21 @@
   return LLDB_RECORD_RESULT(error);
 }
 
+lldb::SBError SBDebugger::InitializeWithErrorHandling(
+    const SBInitializationOptions &options) {
+  LLDB_RECORD_STATIC_METHOD(lldb::SBError, SBDebugger,
+                            InitializeWithErrorHandling,
+                            (const lldb::SBInitializationOptions &), options);
+
+  SBError error;
+  if (auto e = g_debugger_lifetime->Initialize(
+          std::make_unique<SystemInitializerFull>(*options.m_opaque_up),
+          LoadPlugin)) {
+    error.SetError(Status(std::move(e)));
+  }
+  return LLDB_RECORD_RESULT(error);
+}
+
 void SBDebugger::Terminate() {
   LLDB_RECORD_STATIC_METHOD_NO_ARGS(void, SBDebugger, Terminate);
 
@@ -844,16 +875,18 @@
       // The version of CreateTarget that takes an ArchSpec won't accept an
       // empty ArchSpec, so when the arch hasn't been specified, we need to
       // call the target triple version.
-      error = m_opaque_sp->GetTargetList().CreateTarget(*m_opaque_sp, filename, 
-          arch_cstr, eLoadDependentsYes, nullptr, target_sp);
+      error = m_opaque_sp->GetTargetList().CreateTarget(
+          *m_opaque_sp, filename, arch_cstr, eLoadDependentsYes, nullptr,
+          target_sp);
     } else {
       PlatformSP platform_sp = m_opaque_sp->GetPlatformList()
           .GetSelectedPlatform();
-      ArchSpec arch = Platform::GetAugmentedArchSpec(platform_sp.get(), 
-          arch_cstr);
+      ArchSpec arch =
+          Platform::GetAugmentedArchSpec(platform_sp.get(), arch_cstr);
       if (arch.IsValid())
-        error = m_opaque_sp->GetTargetList().CreateTarget(*m_opaque_sp, filename, 
-            arch, eLoadDependentsYes, platform_sp, target_sp);
+        error = m_opaque_sp->GetTargetList().CreateTarget(
+            *m_opaque_sp, filename, arch, eLoadDependentsYes, platform_sp,
+            target_sp);
       else
         error.SetErrorStringWithFormat("invalid arch_cstr: %s", arch_cstr);
     }
@@ -1892,6 +1925,12 @@
   LLDB_REGISTER_METHOD(lldb::SBCommandInterpreterRunResult, SBDebugger,
                        RunCommandInterpreter,
                        (const lldb::SBCommandInterpreterRunOptions &));
+  LLDB_REGISTER_CONSTRUCTOR(SBInitializationOptions, ());
+  LLDB_REGISTER_METHOD(void, SBInitializationOptions, SetVFSOverlay,
+                       (const char *));
+  LLDB_REGISTER_STATIC_METHOD(lldb::SBError, SBDebugger,
+                              InitializeWithErrorHandling,
+                              (const lldb::SBInitializationOptions &));
 }
 
 } // namespace repro
Index: lldb/source/API/SystemInitializerFull.h
===================================================================
--- lldb/source/API/SystemInitializerFull.h
+++ lldb/source/API/SystemInitializerFull.h
@@ -20,7 +20,7 @@
 /// internally by SBDebugger to initialize the system.
 class SystemInitializerFull : public SystemInitializerCommon {
 public:
-  SystemInitializerFull();
+  SystemInitializerFull(SystemInitializerOptions options = {});
   ~SystemInitializerFull() override;
 
   llvm::Error Initialize() override;
Index: lldb/source/API/SystemInitializerFull.cpp
===================================================================
--- lldb/source/API/SystemInitializerFull.cpp
+++ lldb/source/API/SystemInitializerFull.cpp
@@ -44,8 +44,8 @@
 
 using namespace lldb_private;
 
-SystemInitializerFull::SystemInitializerFull()
-    : SystemInitializerCommon(g_shlib_dir_helper) {}
+SystemInitializerFull::SystemInitializerFull(SystemInitializerOptions options)
+    : SystemInitializerCommon(g_shlib_dir_helper, std::move(options)) {}
 SystemInitializerFull::~SystemInitializerFull() = default;
 
 llvm::Error SystemInitializerFull::Initialize() {
Index: lldb/source/Initialization/SystemInitializerCommon.cpp
===================================================================
--- lldb/source/Initialization/SystemInitializerCommon.cpp
+++ lldb/source/Initialization/SystemInitializerCommon.cpp
@@ -35,13 +35,14 @@
 using namespace lldb_private::repro;
 
 SystemInitializerCommon::SystemInitializerCommon(
-    HostInfo::SharedLibraryDirectoryHelper *helper)
-    : m_shlib_dir_helper(helper) {}
+    HostInfo::SharedLibraryDirectoryHelper *helper,
+    SystemInitializerOptions options)
+    : m_shlib_dir_helper(helper), m_options(std::move(options)) {}
 
 SystemInitializerCommon::~SystemInitializerCommon() = default;
 
 /// Initialize the FileSystem based on the current reproducer mode.
-static llvm::Error InitializeFileSystem() {
+static llvm::Error InitializeFileSystem(FileSpec vfs_overlay) {
   auto &r = repro::Reproducer::Instance();
   if (repro::Loader *loader = r.GetLoader()) {
     FileSpec vfs_mapping = loader->GetFile<FileProvider::Info>();
@@ -88,6 +89,12 @@
     return llvm::Error::success();
   }
 
+  if (vfs_overlay) {
+    if (llvm::Error e = FileSystem::Initialize(vfs_overlay))
+      return e;
+    return llvm::Error::success();
+  }
+
   FileSystem::Initialize();
   return llvm::Error::success();
 }
@@ -122,7 +129,7 @@
       return e;
   }
 
-  if (auto e = InitializeFileSystem())
+  if (auto e = InitializeFileSystem(m_options.vfs_overlay))
     return e;
 
   Log::Initialize();
Index: lldb/test/Shell/Driver/Inputs/create_overlay.py
===================================================================
--- /dev/null
+++ lldb/test/Shell/Driver/Inputs/create_overlay.py
@@ -0,0 +1,20 @@
+import sys
+
+_, virtual_path, real_path, overlay_path = sys.argv
+
+string = '''{
+  "use-external-names": false,
+  "version": 0,
+  "roots": [
+    {
+      "type": "file",
+      "name": "%s",
+      "external-contents": "%s"
+    }
+  ]
+}''' % (virtual_path, real_path)
+
+
+with open(overlay_path, 'w') as f:
+  f.write(string)
+  print(string)
Index: lldb/test/Shell/Driver/TestOverlay.test
===================================================================
--- /dev/null
+++ lldb/test/Shell/Driver/TestOverlay.test
@@ -0,0 +1,12 @@
+# REQUIRES: python
+
+# RUN: mkdir -p %t/foo
+# RUN: %clang_host %p/Inputs/hello.c -g -o %t/foo/a.out
+
+# RUN: %python %p/Inputs/create_overlay.py %t/bar/a.out %t/foo/a.out %t.overlay
+
+# RUN: %lldb -vfs-overlay %t.overlay %t/bar/a.out 2>&1 | FileCheck %s
+# CHECK-NOT: error:
+
+# RUN: %lldb %t/bar/a.out 2>&1 | FileCheck %s --check-prefix FAILURE
+# FAILURE: unable to find executable
Index: lldb/tools/driver/Driver.cpp
===================================================================
--- lldb/tools/driver/Driver.cpp
+++ lldb/tools/driver/Driver.cpp
@@ -912,7 +912,10 @@
     return *exit_code;
   }
 
-  SBError error = SBDebugger::InitializeWithErrorHandling();
+  SBInitializationOptions options;
+  if (auto *arg = input_args.getLastArg(OPT_vfs_overlay))
+    options.SetVFSOverlay(arg->getValue());
+  SBError error = SBDebugger::InitializeWithErrorHandling(options);
   if (error.Fail()) {
     WithColor::error() << "initialization failed: " << error.GetCString()
                        << '\n';
Index: lldb/tools/driver/Options.td
===================================================================
--- lldb/tools/driver/Options.td
+++ lldb/tools/driver/Options.td
@@ -243,4 +243,8 @@
 def generate_on_exit: F<"reproducer-generate-on-exit">,
   HelpText<"Generate reproducer on exit.">;
 
+def vfs_overlay: Separate<["--", "-"], "vfs-overlay">,
+  MetaVarName<"<file>">,
+  HelpText<"Overlay the virtual filesystem described by file over the real file system">;
+
 def REM : R<["--"], "">;