Wasm debugging with LLDB: access Wasm engine state

This changelist makes the GDB-stub actually execute GDB-remote commands, by
accessing the Wasm engine state. More precisely:
- class GdbServer registers DebugDelegates that receive debug notifications when
  a new Wasm module is loaded, when execution suspends at a breakpoint or for an
  unhandled exception.
- Since the GDB-remote commands arrive on a separate thread, all
  queries from the debugger are transformed into Task objects, that are posted
  into a TaskRunner that runs in the Isolate thread.
- class WasmModuleDebug contains the logic to retrieve the value of globals, locals, memory ranges from the
  Wasm engine and to add/remove breakpoints.

Build with: v8_enable_wasm_gdb_remote_debugging = true
Run with: --wasm-gdb-remote
Test with: python tools\run-tests.py --outdir=out\debug_x64 debugging -j 1

Bug: chromium:1010467
Change-Id: I9703894620a027d3c920926db92e2ff809d84ab8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1941139Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Paolo Severini <paolosev@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#67412}

BUILD.gn

@@ -3150,6 +3150,8 @@ v8_source_set("v8_base_without_compiler") {
       "src/debug/wasm/gdb-server/target.h",
       "src/debug/wasm/gdb-server/transport.cc",
       "src/debug/wasm/gdb-server/transport.h",
+      "src/debug/wasm/gdb-server/wasm-module-debug.cc",
+      "src/debug/wasm/gdb-server/wasm-module-debug.h",
     ]
   }
 

src/debug/wasm/gdb-server/gdb-remote-util.cc

@@ -73,7 +73,7 @@ std::vector<std::string> StringSplit(const string& instr, const char* delim) {
     // If we still have something to process
     if (*in) {
       const char* start = in;
-      int len = 0;
+      size_t len = 0;
       // Keep moving forward for all valid chars
       while (*in && (strchr(delim, *in) == nullptr)) {
         len++;

src/debug/wasm/gdb-server/gdb-remote-util.h

@@ -31,21 +31,20 @@ bool HexToUInt8(const char chars[2], uint8_t* byte);
 // input char is unexpected.
 bool NibbleToUInt8(char ch, uint8_t* byte);
 
+std::vector<std::string> V8_EXPORT_PRIVATE StringSplit(const std::string& instr,
+                                                       const char* delim);
+
 // Convert the memory pointed to by {mem} into a hex string in GDB-remote
 // format.
 std::string Mem2Hex(const uint8_t* mem, size_t count);
 std::string Mem2Hex(const std::string& str);
 
-std::vector<std::string> V8_EXPORT_PRIVATE StringSplit(const std::string& instr,
-                                                       const char* delim);
-
 // For LLDB debugging, an address in a Wasm module code space is represented
 // with 64 bits, where the first 32 bits identify the module id:
-//
-// 63             32               0
-// +---------------+---------------+
-// |   module_id   |     offset    |
-// +---------------+---------------+
+// +--------------------+--------------------+
+// |     module_id      |       offset       |
+// +--------------------+--------------------+
+//  <----- 32 bit -----> <----- 32 bit ----->
 class wasm_addr_t {
  public:
   wasm_addr_t(uint32_t module_id, uint32_t offset)

src/debug/wasm/gdb-server/gdb-server-thread.h

@@ -34,6 +34,8 @@ class GdbServerThread : public v8::base::Thread {
   // closes any active debugging session.
   void Stop();
 
+  Target& GetTarget() { return *target_; }
+
  private:
   void CleanupThread();
 

src/debug/wasm/gdb-server/gdb-server.h

@@ -5,14 +5,18 @@
 #ifndef V8_DEBUG_WASM_GDB_SERVER_GDB_SERVER_H_
 #define V8_DEBUG_WASM_GDB_SERVER_GDB_SERVER_H_
 
+#include <map>
 #include <memory>
 #include "src/debug/wasm/gdb-server/gdb-server-thread.h"
+#include "src/debug/wasm/gdb-server/wasm-module-debug.h"
 
 namespace v8 {
 namespace internal {
 namespace wasm {
 namespace gdb_server {
 
+class TaskRunner;
+
 // class GdbServer acts as a manager for the GDB-remote stub. It is instantiated
 // as soon as the first Wasm module is loaded in the Wasm engine and spawns a
 // separate thread to accept connections and exchange messages with a debugger.
@@ -37,26 +41,35 @@ class GdbServer {
     uint32_t module_id;
     std::string module_name;
   };
-  std::vector<WasmModuleInfo> GetLoadedModules() const;
+  std::vector<WasmModuleInfo> GetLoadedModules();
 
   // Queries the value of the {index} global value in the Wasm module identified
-  // by {wasm_module_id}.
-  bool GetWasmGlobal(uint32_t wasm_module_id, uint32_t index, uint64_t* value);
+  // by {frame_index}.
+  //
+  bool GetWasmGlobal(uint32_t frame_index, uint32_t index, uint8_t* buffer,
+                     uint32_t buffer_size, uint32_t* size);
 
   // Queries the value of the {index} local value in the {frame_index}th stack
-  // frame in the Wasm module identified by {wasm_module_id}.
-  bool GetWasmLocal(uint32_t wasm_module_id, uint32_t frame_index,
-                    uint32_t index, uint64_t* value);
+  // frame in the Wasm module identified by {frame_index}.
+  //
+  bool GetWasmLocal(uint32_t frame_index, uint32_t index, uint8_t* buffer,
+                    uint32_t buffer_size, uint32_t* size);
+
+  // Queries the value of the {index} value in the operand stack.
+  //
+  bool GetWasmStackValue(uint32_t frame_index, uint32_t index, uint8_t* buffer,
+                         uint32_t buffer_size, uint32_t* size);
 
   // Reads {size} bytes, starting from {offset}, from the Memory instance
-  // associated to the Wasm module identified by {wasm_module_id}.
+  // associated to the Wasm module identified by {frame_index}.
   // Returns the number of bytes copied to {buffer}, or 0 is case of error.
   // Note: only one Memory for Module is currently supported.
-  uint32_t GetWasmMemory(uint32_t wasm_module_id, uint32_t offset,
-                         uint8_t* buffer, uint32_t size);
+  //
+  uint32_t GetWasmMemory(uint32_t frame_index, uint32_t offset, uint8_t* buffer,
+                         uint32_t size);
 
-  // Reads {size} bytes, starting from {address}, from the Code space of the
-  // Wasm module identified by {wasm_module_id}.
+  // Reads {size} bytes, starting from the low dword of {address}, from the Code
+  // space of th Wasm module identified by high dword of {address}.
   // Returns the number of bytes copied to {buffer}, or 0 is case of error.
   uint32_t GetWasmModuleBytes(wasm_addr_t address, uint8_t* buffer,
                               uint32_t size);
@@ -64,21 +77,119 @@ class GdbServer {
   // Inserts a breakpoint at the offset {offset} of the Wasm module identified
   // by {wasm_module_id}.
   // Returns true if the breakpoint was successfully added.
-  bool AddBreakpoint(uint32_t module_id, uint32_t offset);
+  bool AddBreakpoint(uint32_t wasm_module_id, uint32_t offset);
 
   // Removes a breakpoint at the offset {offset} of the Wasm module identified
   // by {wasm_module_id}.
   // Returns true if the breakpoint was successfully removed.
-  bool RemoveBreakpoint(uint32_t module_id, uint32_t offset);
+  bool RemoveBreakpoint(uint32_t wasm_module_id, uint32_t offset);
 
   // Returns the current call stack as a vector of program counters.
   std::vector<wasm_addr_t> GetWasmCallStack() const;
 
+  // Manage the set of Isolates for this GdbServer.
+  void AddIsolate(Isolate* isolate);
+  void RemoveIsolate(Isolate* isolate);
+
+  // Requests that the thread suspend execution at the next Wasm instruction.
+  void Suspend();
+
+  // Handle stepping in wasm functions via the wasm interpreter.
+  void PrepareStep();
+
+  // Called when the target debuggee can resume execution (for example after
+  // having been suspended on a breakpoint). Terminates the task runner leaving
+  // all pending tasks in the queue.
+  void QuitMessageLoopOnPause();
+
  private:
-  GdbServer() {}
+  GdbServer();
+
+  // When the target debuggee is suspended for a breakpoint or exception, blocks
+  // the main (isolate) thread and enters in a message loop. Here it waits on a
+  // queue of Task objects that are posted by the GDB-stub thread and that
+  // represent queries received from the debugger via the GDB-remote protocol.
+  void RunMessageLoopOnPause();
+
+  // Post a task to run a callback in the isolate thread.
+  template <typename Callback>
+  auto RunSyncTask(Callback&& callback) const;
+
+  void AddWasmModule(uint32_t module_id, Local<debug::WasmScript> wasm_script);
+
+  // Given a Wasm module id, retrieves the corresponding debugging WasmScript
+  // object.
+  bool GetModuleDebugHandler(uint32_t module_id,
+                             WasmModuleDebug** wasm_module_debug);
+
+  // Returns the debugging target.
+  Target& GetTarget() const;
+
+  // Class DebugDelegate implements the debug::DebugDelegate interface to
+  // receive notifications when debug events happen in a given isolate, like a
+  // script being loaded, a breakpoint being hit, an exception being thrown.
+  class DebugDelegate : public debug::DebugDelegate {
+   public:
+    DebugDelegate(Isolate* isolate, GdbServer* gdb_server);
+    ~DebugDelegate();
+
+    // debug::DebugDelegate
+    void ScriptCompiled(Local<debug::Script> script, bool is_live_edited,
+                        bool has_compile_error) override;
+    void BreakProgramRequested(Local<v8::Context> paused_context,
+                               const std::vector<debug::BreakpointId>&
+                                   inspector_break_points_hit) override;
+    void ExceptionThrown(Local<v8::Context> paused_context,
+                         Local<Value> exception, Local<Value> promise,
+                         bool is_uncaught,
+                         debug::ExceptionType exception_type) override;
+    bool IsFunctionBlackboxed(Local<debug::Script> script,
+                              const debug::Location& start,
+                              const debug::Location& end) override;
+
+   private:
+    // Calculates module_id as:
+    // +--------------------+------------------- +
+    // | DebugDelegate::id_ |    Script::Id()    |
+    // +--------------------+------------------- +
+    //  <----- 16 bit -----> <----- 16 bit ----->
+    uint32_t GetModuleId(uint32_t script_id) const {
+      DCHECK_LT(script_id, 0x10000);
+      DCHECK_LT(id_, 0x10000);
+      return id_ << 16 | script_id;
+    }
+
+    Isolate* isolate_;
+    uint32_t id_;
+    GdbServer* gdb_server_;
+
+    static std::atomic<uint32_t> id_s;
+  };
 
+  // The GDB-stub thread where all the communication with the debugger happens.
   std::unique_ptr<GdbServerThread> thread_;
 
+  // Used to transform the queries that arrive in the GDB-stub thread into
+  // tasks executed in the main (isolate) thread.
+  std::unique_ptr<TaskRunner> task_runner_;
+
+  //////////////////////////////////////////////////////////////////////////////
+  // Always accessed in the isolate thread.
+
+  // Set of breakpoints currently defines in Wasm code.
+  typedef std::map<uint64_t, int> BreakpointsMap;
+  BreakpointsMap breakpoints_;
+
+  typedef std::map<uint32_t, WasmModuleDebug> ScriptsMap;
+  ScriptsMap scripts_;
+
+  typedef std::map<Isolate*, std::unique_ptr<DebugDelegate>>
+      IsolateDebugDelegateMap;
+  IsolateDebugDelegateMap isolate_delegates_;
+
+  // End of fields always accessed in the isolate thread.
+  //////////////////////////////////////////////////////////////////////////////
+
   DISALLOW_COPY_AND_ASSIGN(GdbServer);
 };
 

src/debug/wasm/gdb-server/session.cc

@@ -36,18 +36,20 @@ bool Session::GetChar(char* ch) {
   return true;
 }
 
-bool Session::SendPacket(Packet* pkt) {
+bool Session::SendPacket(Packet* pkt, bool expect_ack) {
   char ch;
   do {
     std::string data = pkt->GetPacketData();
 
-    TRACE_GDB_REMOTE("TX %s\n", data.c_str());
+    TRACE_GDB_REMOTE("TX %s\n", data.size() < 160
+                                    ? data.c_str()
+                                    : (data.substr(0, 160) + "...").c_str());
     if (!io_->Write(data.data(), static_cast<int32_t>(data.length()))) {
       return false;
     }
 
     // If ACKs are off, we are done.
-    if (!ack_enabled_) {
+    if (!expect_ack || !ack_enabled_) {
       break;
     }
 

src/debug/wasm/gdb-server/session.h

@@ -21,7 +21,7 @@ class V8_EXPORT_PRIVATE Session {
   explicit Session(TransportBase* transport);
 
   // Attempt to send a packet and optionally wait for an ACK from the receiver.
-  bool SendPacket(Packet* packet);
+  bool SendPacket(Packet* packet, bool expect_ack = true);
 
   // Attempt to receive a packet.
   bool GetPacket(Packet* packet);

src/debug/wasm/gdb-server/target.h

@@ -33,7 +33,23 @@ class Target {
   void Terminate();
   bool IsTerminated() const { return status_ == Status::Terminated; }
 
+  // Notifies that the debuggee thread suspended at a breakpoint.
+  void OnProgramBreak(Isolate* isolate,
+                      const std::vector<wasm_addr_t>& call_frames);
+  // Notifies that the debuggee thread suspended because of an unhandled
+  // exception.
+  void OnException(Isolate* isolate,
+                   const std::vector<wasm_addr_t>& call_frames);
+
+  // Returns the state at the moment of the thread suspension.
+  const std::vector<wasm_addr_t> GetCallStack() const;
+  wasm_addr_t GetCurrentPc() const;
+  Isolate* GetCurrentIsolate() const { return current_isolate_; }
+
  private:
+  void OnSuspended(Isolate* isolate, int signal,
+                   const std::vector<wasm_addr_t>& call_frames);
+
   // Initializes a map used to make fast lookups when handling query packets
   // that have a constant response.
   void InitQueryPropertyMap();
@@ -43,11 +59,15 @@ class Target {
   //   closed;
   // - The debuggee suspends execution because of a trap or breakpoint.
   void WaitForDebugEvent();
+  void ProcessDebugEvent();
 
   // Processes GDB-remote packets that arrive from the debugger.
   // This method should be called when the debuggee has suspended its execution.
   void ProcessCommands();
 
+  // Requests that the thread suspends execution at the next Wasm instruction.
+  void Suspend();
+
   enum class ErrorCode { None = 0, BadFormat = 1, BadArgs = 2, Failed = 3 };
 
   enum class ProcessPacketResult {
@@ -69,22 +89,46 @@ class Target {
   // (continue), 's' (step) and '?' (query halt reason) commands.
   void SetStopReply(Packet* pkt_out) const;
 
-  wasm_addr_t GetCurrentPc() const;
+  enum class Status { Running, WaitingForSuspension, Suspended, Terminated };
+
+  void SetStatus(Status status, int8_t signal = 0,
+                 std::vector<wasm_addr_t> call_frames_ = {},
+                 Isolate* isolate = nullptr);
 
   GdbServer* gdb_server_;
 
-  enum class Status { Running, Terminated };
   std::atomic<Status> status_;
 
   // Signal being processed.
-  int8_t cur_signal_;
+  std::atomic<int8_t> cur_signal_;
 
-  Session* session_;  // Session object not owned by the Target.
+  // Session object not owned by the Target.
+  Session* session_;
 
   // Map used to make fast lookups when handling query packets.
   typedef std::map<std::string, std::string> QueryPropertyMap;
   QueryPropertyMap query_properties_;
 
+  bool debugger_initial_suspension_;
+
+  // Used to block waiting for suspension
+  v8::base::Semaphore semaphore_;
+
+  mutable v8::base::Mutex mutex_;
+  //////////////////////////////////////////////////////////////////////////////
+  // Protected by {mutex_}:
+
+  // Current isolate. This is not null only when the target is in a Suspended
+  // state and it is the isolate associated to the current call stack and used
+  // for all debugging activities.
+  Isolate* current_isolate_;
+
+  // Call stack when the execution is suspended.
+  std::vector<wasm_addr_t> call_frames_;
+
+  // End of fields protected by {mutex_}.
+  //////////////////////////////////////////////////////////////////////////////
+
   DISALLOW_COPY_AND_ASSIGN(Target);
 };
 

src/debug/wasm/gdb-server/wasm-module-debug.h

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_DEBUG_WASM_GDB_SERVER_WASM_MODULE_DEBUG_H_
+#define V8_DEBUG_WASM_GDB_SERVER_WASM_MODULE_DEBUG_H_
+
+#include "src/debug/debug.h"
+#include "src/debug/wasm/gdb-server/gdb-remote-util.h"
+#include "src/execution/frames.h"
+
+namespace v8 {
+namespace internal {
+namespace wasm {
+
+class WasmValue;
+
+namespace gdb_server {
+
+// Represents the interface to access the Wasm engine state for a given module.
+// For the moment it only works with interpreted functions, in the future it
+// could be extended to also support Liftoff.
+class WasmModuleDebug {
+ public:
+  WasmModuleDebug(v8::Isolate* isolate, Local<debug::WasmScript> script);
+
+  std::string GetModuleName() const;
+  i::Isolate* GetIsolate() const {
+    return reinterpret_cast<i::Isolate*>(isolate_);
+  }
+
+  // Gets the value of the {index}th global value.
+  static bool GetWasmGlobal(Isolate* isolate, uint32_t frame_index,
+                            uint32_t index, uint8_t* buffer,
+                            uint32_t buffer_size, uint32_t* size);
+
+  // Gets the value of the {index}th local value in the {frame_index}th stack
+  // frame.
+  static bool GetWasmLocal(Isolate* isolate, uint32_t frame_index,
+                           uint32_t index, uint8_t* buffer,
+                           uint32_t buffer_size, uint32_t* size);
+
+  // Gets the value of the {index}th value in the operand stack.
+  static bool GetWasmStackValue(Isolate* isolate, uint32_t frame_index,
+                                uint32_t index, uint8_t* buffer,
+                                uint32_t buffer_size, uint32_t* size);
+
+  // Reads {size} bytes, starting from {offset}, from the Memory instance
+  // associated to this module.
+  // Returns the number of byte copied to {buffer}, or 0 is case of error.
+  // Note: only one Memory for Module is currently supported.
+  static uint32_t GetWasmMemory(Isolate* isolate, uint32_t frame_index,
+                                uint32_t offset, uint8_t* buffer,
+                                uint32_t size);
+
+  // Gets {size} bytes, starting from {offset}, from the Code space of this
+  // module.
+  // Returns the number of byte copied to {buffer}, or 0 is case of error.
+  uint32_t GetWasmModuleBytes(wasm_addr_t wasm_addr, uint8_t* buffer,
+                              uint32_t size);
+
+  // Inserts a breakpoint at the offset {offset} of this module.
+  // Returns {true} if the breakpoint was successfully added.
+  bool AddBreakpoint(uint32_t offset, int* breakpoint_id);
+
+  // Removes a breakpoint at the offset {offset} of the this module.
+  void RemoveBreakpoint(uint32_t offset, int breakpoint_id);
+
+  // Handle stepping in wasm functions via the wasm interpreter.
+  void PrepareStep();
+
+  // Returns the current stack trace as a vector of instruction pointers.
+  static std::vector<wasm_addr_t> GetCallStack(uint32_t debug_context_id,
+                                               Isolate* isolate);
+
+ private:
+  // Returns the module WasmInstance associated to the {frame_index}th frame
+  // in the call stack.
+  static Handle<WasmInstanceObject> GetWasmInstance(Isolate* isolate,
+                                                    uint32_t frame_index);
+
+  // Returns its first WasmInstance for this Wasm module.
+  Handle<WasmInstanceObject> GetFirstWasmInstance();
+
+  // Iterates on current stack frames and return frame information for the
+  // {frame_index} specified.
+  // Returns an empty array if the frame specified does not correspond to a Wasm
+  // stack frame.
+  static std::vector<FrameSummary> FindWasmFrame(
+      StackTraceFrameIterator* frame_it, uint32_t* frame_index);
+
+  // Converts a WasmValue into an array of bytes.
+  static bool GetWasmValue(const wasm::WasmValue& wasm_value, uint8_t* buffer,
+                           uint32_t buffer_size, uint32_t* size);
+
+  v8::Isolate* isolate_;
+  Global<debug::WasmScript> wasm_script_;
+};
+
+}  // namespace gdb_server
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_DEBUG_WASM_GDB_SERVER_WASM_MODULE_DEBUG_H_

src/flags/flag-definitions.h

@@ -1435,6 +1435,7 @@ DEFINE_BOOL(multi_mapped_mock_allocator, false,
 #define DEFAULT_WASM_GDB_REMOTE_PORT 8765
 DEFINE_BOOL(wasm_gdb_remote, false,
             "enable GDB-remote for WebAssembly debugging")
+DEFINE_NEG_IMPLICATION(wasm_gdb_remote, wasm_tier_up)
 DEFINE_INT(wasm_gdb_remote_port, DEFAULT_WASM_GDB_REMOTE_PORT,
            "default port for WebAssembly debugging with LLDB.")
 DEFINE_BOOL(wasm_pause_waiting_for_debugger, false,

src/wasm/wasm-engine.cc

@@ -868,9 +868,20 @@ void WasmEngine::AddIsolate(Isolate* isolate) {
   };
   isolate->heap()->AddGCEpilogueCallback(callback, v8::kGCTypeMarkSweepCompact,
                                          nullptr);
+#ifdef V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
+  if (gdb_server_) {
+    gdb_server_->AddIsolate(isolate);
+  }
+#endif  // V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
 }
 
 void WasmEngine::RemoveIsolate(Isolate* isolate) {
+#ifdef V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
+  if (gdb_server_) {
+    gdb_server_->RemoveIsolate(isolate);
+  }
+#endif  // V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
+
   base::MutexGuard guard(&mutex_);
   auto it = isolates_.find(isolate);
   DCHECK_NE(isolates_.end(), it);
@@ -956,6 +967,7 @@ std::shared_ptr<NativeModule> WasmEngine::NewNativeModule(
 #ifdef V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
   if (FLAG_wasm_gdb_remote && !gdb_server_) {
     gdb_server_ = gdb_server::GdbServer::Create();
+    gdb_server_->AddIsolate(isolate);
   }
 #endif  // V8_ENABLE_WASM_GDB_REMOTE_DEBUGGING
 

test/debugging/testcfg.py

@@ -79,7 +79,8 @@ class PYTestLoader(testsuite.GenericTestLoader):
 
   @property
   def excluded_files(self):
-    return {'gdb_rsp.py', 'testcfg.py', '__init__.py'}
+    return {'gdb_rsp.py', 'testcfg.py', '__init__.py', 'test_basic.py',
+            'test_float.py', 'test_memory.py', 'test_trap.py'}
 
   @property
   def extensions(self):

test/debugging/wasm/gdb-server/OWNERS

+paolosev@microsoft.com
+
+# COMPONENT: Blink>JavaScript>WebAssembly
\ No newline at end of file

test/debugging/wasm/gdb-server/breakpoints.py

+# Copyright 2020 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Flags: -expose-wasm --wasm-gdb-remote --wasm-pause-waiting-for-debugger test/debugging/wasm/gdb-server/test_files/test_basic.js
+
+import sys
+import unittest
+
+import gdb_rsp
+import test_files.test_basic as test_basic
+
+class Tests(unittest.TestCase):
+  def test_initial_breakpoint(self):
+    # Testing that the debuggee suspends when the debugger attaches.
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      reply = connection.RspRequest('?')
+      gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGTRAP)
+
+  def test_setting_removing_breakpoint(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+      func_addr = module_load_addr + test_basic.BREAK_ADDRESS_1
+
+      # Set a breakpoint.
+      reply = connection.RspRequest('Z0,%x,1' % func_addr)
+      self.assertEqual(reply, 'OK')
+
+      # When we run the program, we should hit the breakpoint.
+      reply = connection.RspRequest('c')
+      gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGTRAP)
+      gdb_rsp.CheckInstructionPtr(connection, func_addr)
+
+      # Check that we can remove the breakpoint.
+      reply = connection.RspRequest('z0,%x,0' % func_addr)
+      self.assertEqual(reply, 'OK')
+      # Requesting removing a breakpoint on an address that does not
+      # have one should return an error.
+      reply = connection.RspRequest('z0,%x,0' % func_addr)
+      self.assertEqual(reply, 'E03')
+
+  def test_setting_breakpoint_on_invalid_address(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      # Requesting a breakpoint on an invalid address should give an error.
+      reply = connection.RspRequest('Z0,%x,1' % (1 << 32))
+      self.assertEqual(reply, 'E03')
+
+
+def Main():
+  index = sys.argv.index('--')
+  args = sys.argv[index + 1:]
+  # The remaining arguments go to unittest.main().
+  global COMMAND
+  COMMAND = args
+  unittest.main(argv=sys.argv[:index])
+
+if __name__ == '__main__':
+  Main()

test/debugging/wasm/gdb-server/connect.py

-# Copyright 2019 the V8 project authors. All rights reserved.
+# Copyright 2020 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-# Flags: -expose-wasm --wasm_gdb_remote --wasm-pause-waiting-for-debugger --wasm-interpret-all test/debugging/wasm/gdb-server/test_files/test.js
+# Flags: -expose-wasm --wasm-gdb-remote --wasm-pause-waiting-for-debugger test/debugging/wasm/gdb-server/test_files/test_basic.js
 
+from ctypes import *
 import os
 import subprocess
 import unittest
 import sys
+
 import gdb_rsp
+import test_files.test_basic as test_basic
 
 # These are set up by Main().
 COMMAND = None
 
-
 class Tests(unittest.TestCase):
+
   def test_disconnect(self):
     process = gdb_rsp.PopenDebugStub(COMMAND)
     try:
-      # Connect and record the instruction pointer.
+      # Connect.
       connection = gdb_rsp.GdbRspConnection()
       connection.Close()
       # Reconnect 3 times.
@@ -28,6 +31,29 @@ class Tests(unittest.TestCase):
     finally:
       gdb_rsp.KillProcess(process)
 
+  def test_kill(self):
+    process = gdb_rsp.PopenDebugStub(COMMAND)
+    try:
+      connection = gdb_rsp.GdbRspConnection()
+      # Request killing the target.
+      reply = connection.RspRequest('k')
+      self.assertEqual(reply, 'OK')
+      signal = c_byte(process.wait()).value
+      self.assertEqual(signal, gdb_rsp.RETURNCODE_KILL)
+    finally:
+      gdb_rsp.KillProcess(process)
+
+  def test_detach(self):
+    process = gdb_rsp.PopenDebugStub(COMMAND)
+    try:
+      connection = gdb_rsp.GdbRspConnection()
+      # Request detaching from the target.
+      # This resumes execution, so we get the normal exit() status.
+      reply = connection.RspRequest('D')
+      self.assertEqual(reply, 'OK')
+    finally:
+      gdb_rsp.KillProcess(process)
+
 
 def Main():
   index = sys.argv.index('--')

test/debugging/wasm/gdb-server/float.py

+# Copyright 2020 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Flags: -expose-wasm --wasm-gdb-remote --wasm-pause-waiting-for-debugger test/debugging/wasm/gdb-server/test_files/test_float.js
+
+import os
+import re
+import struct
+import subprocess
+import sys
+import unittest
+
+import gdb_rsp
+import test_files.test_float as test_float
+
+# These are set up by Main().
+COMMAND = None
+
+class Tests(unittest.TestCase):
+
+  def RunToWasm(self, connection):
+    module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+    breakpoint_addr = module_load_addr + test_float.FUNC_START_ADDR
+
+    # Set a breakpoint.
+    reply = connection.RspRequest('Z0,%x,1' % breakpoint_addr)
+    self.assertEqual(reply, 'OK')
+
+    # When we run the program, we should hit the breakpoint.
+    reply = connection.RspRequest('c')
+    gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGTRAP)
+
+    # Remove the breakpoint.
+    reply = connection.RspRequest('z0,%x,1' % breakpoint_addr)
+    self.assertEqual(reply, 'OK')
+
+  def test_loaded_modules(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      modules = gdb_rsp.GetLoadedModules(connection)
+      connection.Close()
+      assert(len(modules) > 0)
+
+  def test_wasm_local_float(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      self.RunToWasm(connection)
+      module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+
+      reply = connection.RspRequest('qWasmLocal:0;0')
+      value = struct.unpack('f', gdb_rsp.DecodeHex(reply))[0]
+      self.assertEqual(test_float.ARG_0, value)
+
+      reply = connection.RspRequest('qWasmLocal:0;1')
+      value = struct.unpack('f', gdb_rsp.DecodeHex(reply))[0]
+      self.assertEqual(test_float.ARG_1, value)
+
+      # invalid local
+      reply = connection.RspRequest('qWasmLocal:0;9')
+      self.assertEqual("E03", reply)
+
+
+def Main():
+  index = sys.argv.index('--')
+  args = sys.argv[index + 1:]
+  # The remaining arguments go to unittest.main().
+  global COMMAND
+  COMMAND = args
+  unittest.main(argv=sys.argv[:index])
+
+if __name__ == '__main__':
+  Main()

test/debugging/wasm/gdb-server/gdb_rsp.py

-# Copyright 2019 the V8 project authors. All rights reserved.
+# Copyright 2020 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import re
 import socket
+import struct
 import subprocess
 import time
+import xml.etree.ElementTree
 
 SOCKET_ADDR = ('localhost', 8765)
 
+SIGTRAP = 5
+SIGSEGV = 11
+RETURNCODE_KILL = -9
+
+ARCH = 'wasm32'
+REG_DEFS = {
+    ARCH: [('pc', 'Q'), ],
+}
+
 
 def EnsurePortIsAvailable(addr=SOCKET_ADDR):
   # As a sanity check, check that the TCP port is available by binding to it
@@ -21,6 +33,11 @@ def EnsurePortIsAvailable(addr=SOCKET_ADDR):
   sock.bind(addr)
   sock.close()
 
+def RspChecksum(data):
+  checksum = 0
+  for char in data:
+    checksum = (checksum + ord(char)) & 0xff
+  return checksum
 
 class GdbRspConnection(object):
 
@@ -48,6 +65,40 @@ class GdbRspConnection(object):
     raise Exception('Could not connect to the debug stub in %i seconds'
                     % timeout_in_seconds)
 
+  def _GetReply(self):
+    reply = ''
+    message_finished = re.compile('#[0-9a-fA-F]{2}')
+    while True:
+      data = self._socket.recv(1024)
+      if len(data) == 0:
+        raise AssertionError('EOF on socket reached with '
+                             'incomplete reply message: %r' % reply)
+      reply += data
+      if message_finished.match(reply[-3:]):
+        break
+    match = re.match('\+?\$([^#]*)#([0-9a-fA-F]{2})$', reply)
+    if match is None:
+      raise AssertionError('Unexpected reply message: %r' % reply)
+    reply_body = match.group(1)
+    checksum = match.group(2)
+    expected_checksum = '%02x' % RspChecksum(reply_body)
+    if checksum != expected_checksum:
+      raise AssertionError('Bad RSP checksum: %r != %r' %
+                           (checksum, expected_checksum))
+    # Send acknowledgement.
+    self._socket.send('+')
+    return reply_body
+
+  # Send an rsp message, but don't wait for or expect a reply.
+  def RspSendOnly(self, data):
+    msg = '$%s#%02x' % (data, RspChecksum(data))
+    return self._socket.send(msg)
+
+  def RspRequest(self, data):
+    self.RspSendOnly(data)
+    reply = self._GetReply()
+    return reply
+
   def Close(self):
     self._socket.close()
 
@@ -71,3 +122,87 @@ def KillProcess(process):
     else:
       raise
   process.wait()
+
+
+class LaunchDebugStub(object):
+  def __init__(self, command):
+    self._proc = PopenDebugStub(command)
+
+  def __enter__(self):
+    try:
+      return GdbRspConnection()
+    except:
+      KillProcess(self._proc)
+      raise
+
+  def __exit__(self, exc_type, exc_value, traceback):
+    KillProcess(self._proc)
+
+
+def AssertEquals(x, y):
+  if x != y:
+    raise AssertionError('%r != %r' % (x, y))
+
+def DecodeHex(data):
+  assert len(data) % 2 == 0, data
+  return bytes(bytearray([int(data[index * 2 : (index + 1) * 2], 16) for index in xrange(len(data) // 2)]))
+
+def EncodeHex(data):
+  return ''.join('%02x' % ord(byte) for byte in data)
+
+def DecodeUInt64Array(data):
+  assert len(data) % 16 == 0, data
+  result = []
+  for index in xrange(len(data) // 16):
+    value = 0
+    for digit in xrange(7, -1, -1):
+      value = value * 256 + int(data[index * 16 + digit * 2 : index * 16 + (digit + 1) * 2], 16)
+    result.append(value)
+  return result
+
+def AssertReplySignal(reply, signal):
+  AssertEquals(ParseThreadStopReply(reply)['signal'], signal)
+
+def ParseThreadStopReply(reply):
+  match = re.match('T([0-9a-f]{2})thread-pcs:([0-9a-f]+);thread:([0-9a-f]+);$', reply)
+  if not match:
+    raise AssertionError('Bad thread stop reply: %r' % reply)
+  return {'signal': int(match.group(1), 16),
+          'thread_pc': int(match.group(2), 16),
+          'thread_id': int(match.group(3), 16)}
+
+def CheckInstructionPtr(connection, expected_ip):
+  ip_value = DecodeRegs(connection.RspRequest('g'))['pc']
+  AssertEquals(ip_value, expected_ip)
+
+def DecodeRegs(reply):
+  defs = REG_DEFS[ARCH]
+  names = [reg_name for reg_name, reg_fmt in defs]
+  fmt = ''.join([reg_fmt for reg_name, reg_fmt in defs])
+
+  values = struct.unpack_from(fmt, DecodeHex(reply))
+  return dict(zip(names, values))
+
+def GetLoadedModules(connection):
+  modules = {}
+  reply = connection.RspRequest('qXfer:libraries:read')
+  AssertEquals(reply[0], 'l')
+  library_list = xml.etree.ElementTree.fromstring(reply[1:])
+  AssertEquals(library_list.tag, 'library-list')
+  for library in library_list:
+    AssertEquals(library.tag, 'library')
+    section = library.find('section')
+    address = section.get('address')
+    assert long(address) > 0
+    modules[long(address)] = library.get('name')
+  return modules
+
+def GetLoadedModuleAddress(connection):
+  modules = GetLoadedModules(connection)
+  assert len(modules) > 0
+  return modules.keys()[0]
+
+def ReadCodeMemory(connection, address, size):
+  reply = connection.RspRequest('m%x,%x' % (address, size))
+  assert not reply.startswith('E'), reply
+  return DecodeHex(reply)

test/debugging/wasm/gdb-server/memory.py

+# Copyright 2020 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Flags: -expose-wasm --wasm-gdb-remote --wasm-pause-waiting-for-debugger test/debugging/wasm/gdb-server/test_files/test_memory.js
+
+import struct
+import sys
+import unittest
+
+import gdb_rsp
+import test_files.test_memory as test_memory
+
+# These are set up by Main().
+COMMAND = None
+
+class Tests(unittest.TestCase):
+  # Test that reading from an unreadable address gives a sensible error.
+  def CheckReadMemoryAtInvalidAddr(self, connection):
+    mem_addr = 0xffffffff
+    result = connection.RspRequest('m%x,%x' % (mem_addr, 1))
+    self.assertEquals(result, 'E02')
+
+  def RunToWasm(self, connection, breakpoint_addr):
+    # Set a breakpoint.
+    reply = connection.RspRequest('Z0,%x,1' % breakpoint_addr)
+    self.assertEqual(reply, 'OK')
+
+    # When we run the program, we should hit the breakpoint.
+    reply = connection.RspRequest('c')
+    gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGTRAP)
+
+    # Remove the breakpoint.
+    reply = connection.RspRequest('z0,%x,1' % breakpoint_addr)
+    self.assertEqual(reply, 'OK')
+
+  def test_reading_and_writing_memory(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+      breakpoint_addr = module_load_addr + test_memory.FUNC0_START_ADDR
+      self.RunToWasm(connection, breakpoint_addr)
+
+      self.CheckReadMemoryAtInvalidAddr(connection)
+
+      # Check reading code memory space.
+      expected_data = b'\0asm'
+      result = gdb_rsp.ReadCodeMemory(connection, module_load_addr, len(expected_data))
+      self.assertEqual(result, expected_data)
+
+      # Check reading instance memory at a valid range.
+      reply = connection.RspRequest('qWasmMem:0;%x;%x' % (32, 4))
+      value = struct.unpack('I', gdb_rsp.DecodeHex(reply))[0]
+      self.assertEquals(int(value), 0)
+
+      # Check reading instance memory at an invalid range.
+      reply = connection.RspRequest('qWasmMem:0;%x;%x' % (0xf0000000, 4))
+      self.assertEqual(reply, 'E03')
+
+  def test_wasm_global(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+      breakpoint_addr = module_load_addr + test_memory.FUNC0_START_ADDR
+      self.RunToWasm(connection, breakpoint_addr)
+
+      # Check reading valid global.
+      reply = connection.RspRequest('qWasmGlobal:0;0')
+      value = struct.unpack('I', gdb_rsp.DecodeHex(reply))[0]
+      self.assertEqual(0, value)
+
+      # Check reading invalid global.
+      reply = connection.RspRequest('qWasmGlobal:0;9')
+      self.assertEqual("E03", reply)
+
+  def test_wasm_call_stack(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+      breakpoint_addr = module_load_addr + test_memory.FUNC0_START_ADDR
+      self.RunToWasm(connection, breakpoint_addr)
+
+      reply = connection.RspRequest('qWasmCallStack')
+      stack = gdb_rsp.DecodeUInt64Array(reply)
+      assert(len(stack) > 2) # At least two Wasm frames, plus one or more JS frames.
+      self.assertEqual(stack[0], module_load_addr + test_memory.FUNC0_START_ADDR)
+      self.assertEqual(stack[1], module_load_addr + test_memory.FUNC1_RETURN_ADDR)
+
+
+def Main():
+  index = sys.argv.index('--')
+  args = sys.argv[index + 1:]
+  # The remaining arguments go to unittest.main().
+  global COMMAND
+  COMMAND = args
+  unittest.main(argv=sys.argv[:index])
+
+if __name__ == '__main__':
+  Main()

test/debugging/wasm/gdb-server/status.py

+# Copyright 2020 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Flags: -expose-wasm --wasm-gdb-remote --wasm-pause-waiting-for-debugger test/debugging/wasm/gdb-server/test_files/test_basic.js
+
+import re
+import struct
+import sys
+import unittest
+
+import gdb_rsp
+import test_files.test_basic as test_basic
+
+# These are set up by Main().
+COMMAND = None
+
+class Tests(unittest.TestCase):
+
+  def test_loaded_modules(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      modules = gdb_rsp.GetLoadedModules(connection)
+      connection.Close()
+      assert(len(modules) > 0)
+
+  def test_checking_thread_state(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      # Query wasm thread id
+      reply = connection.RspRequest('qfThreadInfo')
+      match = re.match('m([0-9])$', reply)
+      if match is None:
+        raise AssertionError('Bad active thread list reply: %r' % reply)
+      thread_id = int(match.group(1), 10)
+      # There should not be other threads.
+      reply = connection.RspRequest('qsThreadInfo')
+      self.assertEqual("l", reply)
+      # Test that valid thread should be alive.
+      reply = connection.RspRequest('T%d' % (thread_id))
+      self.assertEqual("OK", reply)
+      # Test invalid thread id.
+      reply = connection.RspRequest('T42')
+      self.assertEqual("E02", reply)
+
+  def test_wasm_local(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+      breakpoint_addr = module_load_addr + test_basic.BREAK_ADDRESS_2
+
+      reply = connection.RspRequest('Z0,%x,1' % breakpoint_addr)
+      self.assertEqual("OK", reply)
+      reply = connection.RspRequest('c')
+      gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGTRAP)
+
+      reply = connection.RspRequest('qWasmLocal:0;0')
+      value = struct.unpack('I', gdb_rsp.DecodeHex(reply))[0]
+      self.assertEqual(test_basic.ARG_0, value)
+
+      reply = connection.RspRequest('qWasmLocal:0;1')
+      value = struct.unpack('I', gdb_rsp.DecodeHex(reply))[0]
+      self.assertEqual(test_basic.ARG_1, value)
+
+      # invalid local
+      reply = connection.RspRequest('qWasmLocal:0;9')
+      self.assertEqual("E03", reply)
+
+  def test_wasm_stack_value(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+      breakpoint_addr = module_load_addr + test_basic.BREAK_ADDRESS_2
+
+      reply = connection.RspRequest('Z0,%x,1' % breakpoint_addr)
+      self.assertEqual("OK", reply)
+      reply = connection.RspRequest('c')
+      gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGTRAP)
+
+      reply = connection.RspRequest('qWasmStackValue:0;0')
+      value = struct.unpack('I', gdb_rsp.DecodeHex(reply))[0]
+      self.assertEqual(test_basic.ARG_0, value)
+
+      reply = connection.RspRequest('qWasmStackValue:0;1')
+      value = struct.unpack('I', gdb_rsp.DecodeHex(reply))[0]
+      self.assertEqual(test_basic.ARG_1, value)
+
+      # invalid index
+      reply = connection.RspRequest('qWasmStackValue:0;2')
+      self.assertEqual("E03", reply)
+
+  def test_modifying_code_is_disallowed(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      # Pick an arbitrary address in the code segment.
+      module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+      breakpoint_addr = module_load_addr + test_basic.BREAK_ADDRESS_1
+      # Writing to the code area should be disallowed.
+      data = '\x00'
+      write_command = 'M%x,%x:%s' % (breakpoint_addr, len(data), gdb_rsp.EncodeHex(data))
+      reply = connection.RspRequest(write_command)
+      self.assertEquals(reply, 'E03')
+
+
+def Main():
+  index = sys.argv.index('--')
+  args = sys.argv[index + 1:]
+  # The remaining arguments go to unittest.main().
+  global COMMAND
+  COMMAND = args
+  unittest.main(argv=sys.argv[:index])
+
+if __name__ == '__main__':
+  Main()

test/debugging/wasm/gdb-server/stepping.py

+# Copyright 2020 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Flags: -expose-wasm --wasm-gdb-remote --wasm-pause-waiting-for-debugger test/debugging/wasm/gdb-server/test_files/test_basic.js
+
+import sys
+import unittest
+
+import gdb_rsp
+import test_files.test_basic as test_basic
+
+# These are set up by Main().
+COMMAND = None
+
+class Tests(unittest.TestCase):
+  def test_single_step(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+      bp_addr = module_load_addr + test_basic.BREAK_ADDRESS_0
+      reply = connection.RspRequest('Z0,%x,1' % bp_addr)
+      self.assertEqual("OK", reply)
+      reply = connection.RspRequest('c')
+      gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGTRAP)
+
+      # We expect 's' to stop at the next instruction.
+      reply = connection.RspRequest('s')
+      gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGTRAP)
+      tid = gdb_rsp.ParseThreadStopReply(reply)['thread_id']
+      self.assertEqual(tid, 1)
+      regs = gdb_rsp.DecodeRegs(connection.RspRequest('g'))
+      self.assertEqual(regs['pc'], module_load_addr + test_basic.BREAK_ADDRESS_1)
+
+      # Again.
+      reply = connection.RspRequest('s')
+      gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGTRAP)
+      tid = gdb_rsp.ParseThreadStopReply(reply)['thread_id']
+      self.assertEqual(tid, 1)
+      regs = gdb_rsp.DecodeRegs(connection.RspRequest('g'))
+      self.assertEqual(regs['pc'], module_load_addr + test_basic.BREAK_ADDRESS_2)
+
+      # Check that we can continue after single-stepping.
+      reply = connection.RspRequest('c')
+      gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGTRAP)
+
+
+def Main():
+  index = sys.argv.index('--')
+  args = sys.argv[index + 1:]
+  # The remaining arguments go to unittest.main().
+  global COMMAND
+  COMMAND = args
+  unittest.main(argv=sys.argv[:index])
+
+if __name__ == '__main__':
+  Main()

test/debugging/wasm/gdb-server/test_files/test.js → test/debugging/wasm/gdb-server/test_files/test_basic.js

-
-// Copyright 2019 the V8 project authors. All rights reserved.
+// Copyright 2020 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-load("test/mjsunit/wasm/wasm-module-builder.js");
+load('test/mjsunit/wasm/wasm-module-builder.js');
 
 var builder = new WasmModuleBuilder();
-builder.addFunction('mul', kSig_i_ii)
-// input is 2 args of type int and output is int
-.addBody([
-  kExprLocalGet, 0, // local.get i0
-  kExprLocalGet, 1, // local.get i1
-  kExprI32Mul]) // i32.sub i0 i1
-.exportFunc();
+builder
+    .addFunction('mul', kSig_i_ii)
+    // input is 2 args of type int and output is int
+    .addBody([
+      kExprLocalGet, 0,  // local.get i0
+      kExprLocalGet, 1,  // local.get i1
+      kExprI32Mul
+    ])  // i32.mul i0 i1
+    .exportFunc();
 
 const instance = builder.instantiate();
 const wasm_f = instance.exports.mul;
@@ -23,11 +24,8 @@ function f() {
 }
 
 try {
-    let val = 0;
-    while (true) {
-        val += f();
-    }
-}
-catch (e) {
-    print('*exception:* ' + e);
+  let val = f();
+  f();
+} catch (e) {
+  print('*exception:* ' + e);
 }

test/debugging/wasm/gdb-server/test_files/test_basic.py

+# Copyright 2020 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# 0x00 (module
+# 0x08   [type]
+#        (type $type0 (func (param i32 i32) (result i32)))
+# 0x11   [function]
+# 0x15   (export "mul" (func $func0))
+# 0x1e   [code]
+# 0x20   (func $func0 (param $var0 i32) (param $var1 i32) (result i32)
+# 0x23     get_local $var0
+# 0x25     get_local $var1
+# 0x27     i32.mul
+#   )
+# )
+# 0x29   [name]
+
+BREAK_ADDRESS_0 = 0x0023
+BREAK_ADDRESS_1 = 0x0025
+BREAK_ADDRESS_2 = 0x0027
+ARG_0 = 21
+ARG_1 = 2

test/debugging/wasm/gdb-server/test_files/test_float.js

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+load('test/mjsunit/wasm/wasm-module-builder.js');
+
+var builder = new WasmModuleBuilder();
+builder
+    .addFunction('mul', kSig_f_ff)
+    // input is 2 args of type float and output is float
+    .addBody([
+      kExprLocalGet, 0,  // local.get f0
+      kExprLocalGet, 1,  // local.get f1
+      kExprF32Mul,       // f32.mul i0 i1
+    ])
+    .exportFunc();
+
+const instance = builder.instantiate();
+const wasm_f = instance.exports.mul;
+
+function f() {
+  var result = wasm_f(12.0, 3.5);
+  return result;
+}
+
+try {
+  let val = f();
+  print('float result: ' + val);
+} catch (e) {
+  print('*exception:* ' + e);
+}

test/debugging/wasm/gdb-server/test_files/test_float.py

+# Copyright 2020 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# 0x00 (module
+# 0x08   [type]
+#        (type $type0 (func (param f32 f32) (result f32)))
+# 0x11   [function]
+# 0x15   (export "mul" (func $func0))
+# 0x1e   [code]
+# 0x20   (func $func0 (param $var0 f32) (param $var1 f32) (result f32)
+# 0x23     get_local $var0
+# 0x25     get_local $var1
+# 0x27     f32.mul
+#   )
+# )
+# 0x29   [name]
+
+ARG_0 = 12.0
+ARG_1 = 3.5
+FUNC_START_ADDR = 0x23

test/debugging/wasm/gdb-server/test_files/test_memory.js

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+load('test/mjsunit/wasm/wasm-module-builder.js');
+
+var builder = new WasmModuleBuilder();
+
+builder.addGlobal(kWasmI32).exportAs('g_n');
+
+builder.addMemory(32, 128).exportMemoryAs('mem')
+
+var func_a_idx =
+    builder.addFunction('wasm_A', kSig_v_i).addBody([kExprNop, kExprNop]).index;
+
+// wasm_B calls wasm_A <param0> times.
+builder.addFunction('wasm_B', kSig_v_i)
+    .addBody([
+      kExprLoop,
+      kWasmStmt,  // while
+      kExprLocalGet,
+      0,  // -
+      kExprIf,
+      kWasmStmt,  // if <param0> != 0
+      kExprLocalGet,
+      0,  // -
+      kExprI32Const,
+      1,            // -
+      kExprI32Sub,  // -
+      kExprLocalSet,
+      0,                      // decrease <param0>
+      ...wasmI32Const(1024),  // some longer i32 const (2 byte imm)
+      kExprCallFunction,
+      func_a_idx,  // -
+      kExprBr,
+      1,         // continue
+      kExprEnd,  // -
+      kExprEnd,  // break
+    ])
+    .exportAs('main');
+
+const instance = builder.instantiate();
+const wasm_main = instance.exports.main;
+
+function f() {
+  wasm_main(42);
+}
+f();

test/debugging/wasm/gdb-server/test_files/test_memory.py

+# Copyright 2020 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# 0x00 (module
+# 0x08   [type]
+# 0x0a   (type $type0 (func (param i32)))
+# 0x0f   (type $type1 (func (param i32)))
+# 0x13   [function]
+# 0x18   [memory]
+#        (memory (;0;) 32 128)
+# 0x1f   [global]
+# 0x27   (global $global0 i32 (i32.const 0))
+# 0x29   (export "g_n" (global $global0))
+# 0x30   (export "mem" (memory 0))
+# 0x36   (export "main" (func $func1))
+# 0x3d   [code]
+# 0x3f   (func $func0 (param $var0 i32)
+# 0x42     nop
+# 0x43     nop
+#   )
+# 0x45   (func $func1 (param $var0 i32)
+# 0x47     loop $label0
+# 0x49       get_local $var0
+# 0x4b       if
+# 0x4d         get_local $var0
+# 0x4f         i32.const 1
+# 0x51         i32.sub
+# 0x52         set_local $var0
+# 0x54         i32.const 1024
+# 0x57         call $func0
+# 0x59         br $label0
+# 0x5b       end
+# 0x5c     end $label0
+#   )
+# )
+# 0x5e   [name]
+
+MEM_MIN = 32
+MEM_MAX = 128
+FUNC0_START_ADDR = 0x42
+FUNC1_RETURN_ADDR = 0x59
+FUNC1_START_ADDR = 0x47

test/debugging/wasm/gdb-server/test_files/test_trap.js

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+load('test/mjsunit/wasm/wasm-module-builder.js');
+
+var builder = new WasmModuleBuilder();
+
+builder.addMemory(32, 128).exportMemoryAs('mem')
+
+var func_a_idx =
+  builder.addFunction('wasm_A', kSig_v_v).addBody([
+    kExprI32Const, 0,  // i32.const 0
+    kExprI32Const, 42, // i32.const 42
+    kExprI32StoreMem, 0, 0xff, 0xff, 0xff, 0xff, 0x0f, // i32.store offset = -1
+  ]).index;
+
+builder.addFunction('main', kSig_i_v).addBody([
+    kExprCallFunction, func_a_idx, // call $wasm_A
+    kExprI32Const, 0 // i32.const 0
+  ])
+  .exportFunc();
+
+const instance = builder.instantiate();
+const main_f = instance.exports.main;
+
+function f() {
+  var result = main_f();
+  return result;
+}
+f();

test/debugging/wasm/gdb-server/test_files/test_trap.py

+# Copyright 2020 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# 0x00 (module
+# 0x08   [type]
+# 0x0a   (type $type0 (func))
+# 0x0e   (type $type1 (func (result i32)))
+# 0x12   [function]
+# 0x17   [memory]
+# 0x19   (memory $memory0 32 128)
+# 0x1e   [export]
+# 0x20   (export "mem" (memory $memory0))
+# 0x27   (export "main" (func $func1))
+# 0x2e   [code]
+# 0x30   (func $func0
+# 0x33     i32.const 0
+# 0x35     i32.const 42
+# 0x37     i32.store offset=-1 align=1
+# 0x3e   )
+# 0x3f   (func $func1 (result i32)
+# 0x41     call $func0
+# 0x43     i32.const 0
+# 0x45   )
+# 0x46   ...
+#      )
+
+TRAP_ADDRESS = 0x0037

test/debugging/wasm/gdb-server/trap.py

+# Copyright 2020 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Flags: -expose-wasm --wasm-gdb-remote --wasm-pause-waiting-for-debugger test/debugging/wasm/gdb-server/test_files/test_trap.js
+
+import sys
+import unittest
+
+import gdb_rsp
+import test_files.test_trap as test_trap
+
+# These are set up by Main().
+COMMAND = None
+
+class Tests(unittest.TestCase):
+  def test_trap(self):
+    with gdb_rsp.LaunchDebugStub(COMMAND) as connection:
+      module_load_addr = gdb_rsp.GetLoadedModuleAddress(connection)
+      reply = connection.RspRequest('c')
+      gdb_rsp.AssertReplySignal(reply, gdb_rsp.SIGSEGV)
+      tid = gdb_rsp.ParseThreadStopReply(reply)['thread_id']
+      self.assertEqual(tid, 1)
+      regs = gdb_rsp.DecodeRegs(connection.RspRequest('g'))
+      self.assertEqual(regs['pc'], module_load_addr + test_trap.TRAP_ADDRESS)
+
+
+def Main():
+  index = sys.argv.index('--')
+  args = sys.argv[index + 1:]
+  # The remaining arguments go to unittest.main().
+  global COMMAND
+  COMMAND = args
+  unittest.main(argv=sys.argv[:index])
+
+if __name__ == '__main__':
+  Main()