[lldb] Inherit DuplicateFileAction(HANDLE, HANDLE) handles on windows (#137978)

This is a follow-up to #126935,
which enables passing handles to a child
process on windows systems. Unlike on unix-like systems, the handles
need to be created with the "inheritable" flag because there's to way to
change the flag value after it has been created. This is why I don't
respect the child_process_inherit flag but rather always set the flag to
true. (My next step is to delete the flag entirely.)

This does mean that pipe may be created as inheritable even if its not
necessary, but I think this is offset by the fact that windows (unlike
unixes, which pass all ~O_CLOEXEC descriptors through execve and *all*
descriptors through fork) has a way to specify the precise set of
handles to pass to a specific child process.

If this turns out to be insufficient, instead of a constructor flag, I'd
rather go with creating a separate api to create an inheritable copy of
a handle (as typically, you only want to inherit one end of the pipe).

Author: labath

lldb/source/Host/windows/PipeWindows.cpp

@@ -88,8 +88,9 @@ Status PipeWindows::CreateNew(llvm::StringRef name,
   std::string pipe_path = g_pipe_name_prefix.str();
   pipe_path.append(name.str());
 
-  SECURITY_ATTRIBUTES sa{sizeof(SECURITY_ATTRIBUTES), 0,
-                         child_process_inherit ? TRUE : FALSE};
+  // We always create inheritable handles, but we won't pass them to a child
+  // process unless explicitly requested (cf. ProcessLauncherWindows.cpp).
+  SECURITY_ATTRIBUTES sa{sizeof(SECURITY_ATTRIBUTES), 0, TRUE};
 
   // Always open for overlapped i/o.  We implement blocking manually in Read
   // and Write.

lldb/source/Host/windows/ProcessLauncherWindows.cpp

@@ -10,6 +10,7 @@
 #include "lldb/Host/HostProcess.h"
 #include "lldb/Host/ProcessLaunchInfo.h"
 
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/ConvertUTF.h"
 #include "llvm/Support/Program.h"
@@ -65,14 +66,23 @@ ProcessLauncherWindows::LaunchProcess(const ProcessLaunchInfo &launch_info,
 
   std::string executable;
   std::vector<char> environment;
-  STARTUPINFO startupinfo = {};
+  STARTUPINFOEX startupinfoex = {};
+  STARTUPINFO &startupinfo = startupinfoex.StartupInfo;
   PROCESS_INFORMATION pi = {};
 
   HANDLE stdin_handle = GetStdioHandle(launch_info, STDIN_FILENO);
   HANDLE stdout_handle = GetStdioHandle(launch_info, STDOUT_FILENO);
   HANDLE stderr_handle = GetStdioHandle(launch_info, STDERR_FILENO);
-
-  startupinfo.cb = sizeof(startupinfo);
+  auto close_handles = llvm::make_scope_exit([&] {
+    if (stdin_handle)
+      ::CloseHandle(stdin_handle);
+    if (stdout_handle)
+      ::CloseHandle(stdout_handle);
+    if (stderr_handle)
+      ::CloseHandle(stderr_handle);
+  });
+
+  startupinfo.cb = sizeof(startupinfoex);
   startupinfo.dwFlags |= STARTF_USESTDHANDLES;
   startupinfo.hStdError =
       stderr_handle ? stderr_handle : ::GetStdHandle(STD_ERROR_HANDLE);
@@ -81,6 +91,48 @@ ProcessLauncherWindows::LaunchProcess(const ProcessLaunchInfo &launch_info,
   startupinfo.hStdOutput =
       stdout_handle ? stdout_handle : ::GetStdHandle(STD_OUTPUT_HANDLE);
 
+  std::vector<HANDLE> inherited_handles;
+  if (startupinfo.hStdError)
+    inherited_handles.push_back(startupinfo.hStdError);
+  if (startupinfo.hStdInput)
+    inherited_handles.push_back(startupinfo.hStdInput);
+  if (startupinfo.hStdOutput)
+    inherited_handles.push_back(startupinfo.hStdOutput);
+
+  size_t attributelist_size = 0;
+  InitializeProcThreadAttributeList(/*lpAttributeList=*/nullptr,
+                                    /*dwAttributeCount=*/1, /*dwFlags=*/0,
+                                    &attributelist_size);
+
+  startupinfoex.lpAttributeList =
+      static_cast<LPPROC_THREAD_ATTRIBUTE_LIST>(malloc(attributelist_size));
+  auto free_attributelist =
+      llvm::make_scope_exit([&] { free(startupinfoex.lpAttributeList); });
+  if (!InitializeProcThreadAttributeList(startupinfoex.lpAttributeList,
+                                         /*dwAttributeCount=*/1, /*dwFlags=*/0,
+                                         &attributelist_size)) {
+    error = Status(::GetLastError(), eErrorTypeWin32);
+    return HostProcess();
+  }
+  auto delete_attributelist = llvm::make_scope_exit(
+      [&] { DeleteProcThreadAttributeList(startupinfoex.lpAttributeList); });
+  for (size_t i = 0; i < launch_info.GetNumFileActions(); ++i) {
+    const FileAction *act = launch_info.GetFileActionAtIndex(i);
+    if (act->GetAction() == FileAction::eFileActionDuplicate &&
+        act->GetFD() == act->GetActionArgument())
+      inherited_handles.push_back(reinterpret_cast<HANDLE>(act->GetFD()));
+  }
+  if (!inherited_handles.empty()) {
+    if (!UpdateProcThreadAttribute(
+            startupinfoex.lpAttributeList, /*dwFlags=*/0,
+            PROC_THREAD_ATTRIBUTE_HANDLE_LIST, inherited_handles.data(),
+            inherited_handles.size() * sizeof(HANDLE),
+            /*lpPreviousValue=*/nullptr, /*lpReturnSize=*/nullptr)) {
+      error = Status(::GetLastError(), eErrorTypeWin32);
+      return HostProcess();
+    }
+  }
+
   const char *hide_console_var =
       getenv("LLDB_LAUNCH_INFERIORS_WITHOUT_CONSOLE");
   if (hide_console_var &&
@@ -89,7 +141,8 @@ ProcessLauncherWindows::LaunchProcess(const ProcessLaunchInfo &launch_info,
     startupinfo.wShowWindow = SW_HIDE;
   }
 
-  DWORD flags = CREATE_NEW_CONSOLE | CREATE_UNICODE_ENVIRONMENT;
+  DWORD flags = CREATE_NEW_CONSOLE | CREATE_UNICODE_ENVIRONMENT |
+                EXTENDED_STARTUPINFO_PRESENT;
   if (launch_info.GetFlags().Test(eLaunchFlagDebug))
     flags |= DEBUG_ONLY_THIS_PROCESS;
 
@@ -114,9 +167,10 @@ ProcessLauncherWindows::LaunchProcess(const ProcessLaunchInfo &launch_info,
   WCHAR *pwcommandLine = wcommandLine.empty() ? nullptr : &wcommandLine[0];
 
   BOOL result = ::CreateProcessW(
-      wexecutable.c_str(), pwcommandLine, NULL, NULL, TRUE, flags, env_block,
+      wexecutable.c_str(), pwcommandLine, NULL, NULL,
+      /*bInheritHandles=*/!inherited_handles.empty(), flags, env_block,
       wworkingDirectory.size() == 0 ? NULL : wworkingDirectory.c_str(),
-      &startupinfo, &pi);
+      reinterpret_cast<STARTUPINFO *>(&startupinfoex), &pi);
 
   if (!result) {
     // Call GetLastError before we make any other system calls.
@@ -131,13 +185,6 @@ ProcessLauncherWindows::LaunchProcess(const ProcessLaunchInfo &launch_info,
     ::CloseHandle(pi.hThread);
   }
 
-  if (stdin_handle)
-    ::CloseHandle(stdin_handle);
-  if (stdout_handle)
-    ::CloseHandle(stdout_handle);
-  if (stderr_handle)
-    ::CloseHandle(stderr_handle);
-
   if (!result)
     return HostProcess();
 

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

@@ -924,9 +924,7 @@ Status GDBRemoteCommunication::StartDebugserverProcess(
     debugserver_args.AppendArgument(fd_arg.GetString());
     // Send "pass_comm_fd" down to the inferior so it can use it to
     // communicate back with this process. Ignored on Windows.
-#ifndef _WIN32
     launch_info.AppendDuplicateFileAction((int)pass_comm_fd, (int)pass_comm_fd);
-#endif
   }
 
   // use native registers, not the GDB registers

lldb/tools/lldb-server/lldb-platform.cpp

@@ -274,10 +274,8 @@ static Status spawn_process(const char *progname, const FileSpec &prog,
   self_args.AppendArgument(llvm::StringRef("platform"));
   self_args.AppendArgument(llvm::StringRef("--child-platform-fd"));
   self_args.AppendArgument(llvm::to_string(shared_socket.GetSendableFD()));
-#ifndef _WIN32
   launch_info.AppendDuplicateFileAction((int)shared_socket.GetSendableFD(),
                                         (int)shared_socket.GetSendableFD());
-#endif
   if (gdb_port) {
     self_args.AppendArgument(llvm::StringRef("--gdbserver-port"));
     self_args.AppendArgument(llvm::to_string(gdb_port));

lldb/unittests/Host/HostTest.cpp

@@ -90,7 +90,6 @@ TEST(Host, LaunchProcessSetsArgv0) {
   ASSERT_THAT(exit_status.get_future().get(), 0);
 }
 
-#ifdef LLVM_ON_UNIX
 TEST(Host, LaunchProcessDuplicatesHandle) {
   static constexpr llvm::StringLiteral test_msg("Hello subprocess!");
 
@@ -126,4 +125,3 @@ TEST(Host, LaunchProcessDuplicatesHandle) {
   ASSERT_THAT_EXPECTED(bytes_read, llvm::Succeeded());
   ASSERT_EQ(llvm::StringRef(msg, *bytes_read), test_msg);
 }
-#endif