[lldb] Implement WebAssembly debugging

lldb/include/lldb/Target/Process.h

@@ -1548,6 +1548,46 @@ class Process : public std::enable_shared_from_this<Process>,
   virtual size_t ReadMemory(lldb::addr_t vm_addr, void *buf, size_t size,
                             Status &error);
 
+  /// Read of memory from a process.
+  ///
+  /// This function will read memory from the current process's address space
+  /// and remove any traps that may have been inserted into the memory.
+  ///
+  /// This overloads accepts an ExecutionContext as additional argument. By
+  /// default, it calls the previous overload without the ExecutionContext
+  /// argument, but it can be overridden by Process subclasses.
+  ///
+  /// \param[in] vm_addr
+  ///     A virtual load address that indicates where to start reading
+  ///     memory from.
+  ///
+  /// \param[out] buf
+  ///     A byte buffer that is at least \a size bytes long that
+  ///     will receive the memory bytes.
+  ///
+  /// \param[in] size
+  ///     The number of bytes to read.
+  ///
+  /// \param[in] exe_ctx
+  ///    The current execution context, if available.
+  ///
+  /// \param[out] error
+  ///     An error that indicates the success or failure of this
+  ///     operation. If error indicates success (error.Success()),
+  ///     then the value returned can be trusted, otherwise zero
+  ///     will be returned.
+  ///
+  /// \return
+  ///     The number of bytes that were actually read into \a buf. If
+  ///     the returned number is greater than zero, yet less than \a
+  ///     size, then this function will get called again with \a
+  ///     vm_addr, \a buf, and \a size updated appropriately. Zero is
+  ///     returned in the case of an error.
+  virtual size_t ReadMemory(lldb::addr_t vm_addr, void *buf, size_t size,
+                            ExecutionContext *exe_ctx, Status &error) {
+    return ReadMemory(vm_addr, buf, size, error);
+  }
+
   /// Read of memory from a process.
   ///
   /// This function has the same semantics of ReadMemory except that it

lldb/source/Core/Value.cpp

@@ -552,7 +552,7 @@ Status Value::GetValueAsData(ExecutionContext *exe_ctx, DataExtractor &data,
 
         if (process) {
           const size_t bytes_read =
-              process->ReadMemory(address, dst, byte_size, error);
+              process->ReadMemory(address, dst, byte_size, exe_ctx, error);
           if (bytes_read != byte_size)
             error.SetErrorStringWithFormat(
                 "read memory from 0x%" PRIx64 " failed (%u of %u bytes read)",

lldb/source/Expression/DWARFExpression.cpp

@@ -346,6 +346,16 @@ static offset_t GetOpcodeDataSize(const DataExtractor &data,
     return (offset - data_offset) + subexpr_len;
   }
 
+  case DW_OP_WASM_location: {
+    uint8_t wasm_op = data.GetU8(&offset);
+    if (wasm_op == 3) {
+      data.GetU32(&offset);
+    } else {
+      data.GetULEB128(&offset);
+    }
+    return offset - data_offset;
+  }
+
   default:
     if (!dwarf_cu) {
       return LLDB_INVALID_OFFSET;
@@ -2595,6 +2605,37 @@ bool DWARFExpression::Evaluate(
       break;
     }
 
+    case DW_OP_WASM_location: {
+      uint8_t wasm_op = opcodes.GetU8(&offset);
+      uint32_t index;
+
+      /* LLDB doesn't have an address space to represents WebAssembly locals,
+       * globals and operand stacks.
+       * We encode these elements into virtual registers:
+       *   | tag: 2 bits | index: 30 bits |
+       *   where tag is:
+       *    0: Not a WebAssembly location
+       *    1: Local
+       *    2: Global
+       *    3: Operand stack value
+       */
+      if (wasm_op == 3) {
+        index = opcodes.GetU32(&offset);
+        wasm_op = 1;
+      } else {
+        index = opcodes.GetULEB128(&offset);
+      }
+
+      reg_num = (((wasm_op + 1) & 0x03) << 30) | (index & 0x3fffffff);
+
+      if (ReadRegisterValueAsScalar(reg_ctx, reg_kind, reg_num, error_ptr, tmp))
+        stack.push_back(tmp);
+      else
+        return false;
+
+      break;
+    }
+
     default:
       if (dwarf_cu) {
         if (dwarf_cu->GetSymbolFileDWARF().ParseVendorDWARFOpcode(

lldb/source/Interpreter/CommandInterpreter.cpp

@@ -794,6 +794,24 @@ void CommandInterpreter::LoadCommandDictionary() {
     }
   }
 
+  std::unique_ptr<CommandObjectRegexCommand> connect_wasm_cmd_up(
+      new CommandObjectRegexCommand(
+          *this, "wasm",
+          "Connect to a WebAssembly process via remote GDB server.  "
+          "If no host is specifed, localhost is assumed.",
+          "wasm [<hostname>:]<portnum>", 0, false));
+  if (connect_wasm_cmd_up) {
+    if (connect_wasm_cmd_up->AddRegexCommand(
+            "^([^:]+|\\[[0-9a-fA-F:]+.*\\]):([0-9]+)$",
+            "process connect --plugin wasm connect://%1:%2") &&
+        connect_wasm_cmd_up->AddRegexCommand(
+            "^([[:digit:]]+)$",
+            "process connect --plugin wasm connect://localhost:%1")) {
+      CommandObjectSP command_sp(connect_wasm_cmd_up.release());
+      m_command_dict[std::string(command_sp->GetCommandName())] = command_sp;
+    }
+  }
+
   std::unique_ptr<CommandObjectRegexCommand> connect_kdp_remote_cmd_up(
       new CommandObjectRegexCommand(
           *this, "kdp-remote",

lldb/source/Plugins/Process/CMakeLists.txt

@@ -19,3 +19,4 @@ add_subdirectory(elf-core)
 add_subdirectory(mach-core)
 add_subdirectory(minidump)
 add_subdirectory(FreeBSDKernel)
+add_subdirectory(wasm)

lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp

@@ -1628,6 +1628,11 @@ void ProcessGDBRemote::ParseExpeditedRegisters(
   }
 }
 
+std::shared_ptr<ThreadGDBRemote>
+ProcessGDBRemote::CreateThread(lldb::tid_t tid) {
+  return std::make_shared<ThreadGDBRemote>(*this, tid);
+}
+
 ThreadSP ProcessGDBRemote::SetThreadStopInfo(
     lldb::tid_t tid, ExpeditedRegisterMap &expedited_register_map,
     uint8_t signo, const std::string &thread_name, const std::string &reason,
@@ -1652,7 +1657,7 @@ ThreadSP ProcessGDBRemote::SetThreadStopInfo(
 
     if (!thread_sp) {
       // Create the thread if we need to
-      thread_sp = std::make_shared<ThreadGDBRemote>(*this, tid);
+      thread_sp = CreateThread(tid);
       m_thread_list_real.AddThread(thread_sp);
     }
   }

lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h

@@ -355,6 +355,8 @@ class ProcessGDBRemote : public Process,
   MonitorDebugserverProcess(std::weak_ptr<ProcessGDBRemote> process_wp,
                             lldb::pid_t pid, int signo, int exit_status);
 
+  virtual std::shared_ptr<ThreadGDBRemote> CreateThread(lldb::tid_t tid);
+
   lldb::StateType SetThreadStopInfo(StringExtractor &stop_packet);
 
   bool

lldb/source/Plugins/Process/wasm/CMakeLists.txt

@@ -0,0 +1,12 @@
+add_lldb_library(lldbPluginProcessWasm PLUGIN
+  ProcessWasm.cpp
+  ThreadWasm.cpp
+  UnwindWasm.cpp
+  wasmRegisterContext.cpp
+
+  LINK_LIBS
+    lldbCore
+    ${LLDB_PLUGINS}
+  LINK_COMPONENTS
+    Support
+  )