[lldb] Implement WebAssembly debugging

lldb/include/lldb/Target/Process.h

@@ -1450,6 +1450,14 @@ class Process : public std::enable_shared_from_this<Process>,
   /// platforms where there is a difference (only Arm Thumb at this time).
   lldb::addr_t FixAnyAddress(lldb::addr_t pc);
 
+  /// Some targets might use bits in a code address to represent additional
+  /// information; for example WebAssembly targets have a different memory space
+  /// per module and have a different address space per memory and code.
+  virtual lldb::addr_t FixMemoryAddress(lldb::addr_t address,
+                                        StackFrame *stack_frame) const {
+    return address;
+  }
+
   /// Get the Modification ID of the process.
   ///
   /// \return
@@ -1926,9 +1934,9 @@ class Process : public std::enable_shared_from_this<Process>,
   ///     the instruction has completed executing.
   bool GetWatchpointReportedAfter();
 
-  lldb::ModuleSP ReadModuleFromMemory(const FileSpec &file_spec,
-                                      lldb::addr_t header_addr,
-                                      size_t size_to_read = 512);
+  virtual lldb::ModuleSP ReadModuleFromMemory(const FileSpec &file_spec,
+                                              lldb::addr_t header_addr,
+                                              size_t size_to_read = 512);
 
   /// Attempt to get the attributes for a region of memory in the process.
   ///

lldb/source/Core/Value.cpp

@@ -551,8 +551,9 @@ Status Value::GetValueAsData(ExecutionContext *exe_ctx, DataExtractor &data,
         Process *process = exe_ctx->GetProcessPtr();
 
         if (process) {
-          const size_t bytes_read =
-              process->ReadMemory(address, dst, byte_size, error);
+          const size_t bytes_read = process->ReadMemory(
+              process->FixMemoryAddress(address, exe_ctx->GetFramePtr()), dst,
+              byte_size, 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 +346,15 @@ 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 +2604,37 @@ 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 = 2; // Global
+      } 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/Expression/Materializer.cpp

@@ -1077,7 +1077,9 @@ class EntityResultVariable : public Materializer::Entity {
     const size_t pvar_byte_size = ret->GetByteSize().value_or(0);
     uint8_t *pvar_data = ret->GetValueBytes();
 
-    map.ReadMemory(pvar_data, address, pvar_byte_size, read_error);
+    map.ReadMemory(pvar_data,
+                   process_sp->FixMemoryAddress(address, frame_sp.get()),
+                   pvar_byte_size, read_error);
 
     if (!read_error.Success()) {
       err.SetErrorString(

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
+  )