Job control: controlling TTYs and foreground process groups.

Adresses a deadlock with the rolled back change:
https://github.com/google/gvisor/commit/b6a5b950d28e0b474fdad160b88bc15314cf9259
Creating a session from an orphaned process group was causing a lock to be
acquired twice by a single goroutine. This behavior is addressed, and a test
(OrphanRegression) has been added to pty.cc.

Implemented the following ioctls:
- TIOCSCTTY - set controlling TTY
- TIOCNOTTY - remove controlling tty, maybe signal some other processes
- TIOCGPGRP - get foreground process group. Also enables tcgetpgrp().
- TIOCSPGRP - set foreground process group. Also enabled tcsetpgrp().

Next steps are to actually turn terminal-generated control characters (e.g. C^c)
into signals to the proper process groups, and to send SIGTTOU and SIGTTIN when
appropriate.

PiperOrigin-RevId: 270088599

1 files changed, 45 insertions, 0 deletions

diff --git a/test/util/pty_util.cc b/test/util/pty_util.cc
new file mode 100644
index 000000000..c0fd9a095
--- /dev/null
+++ b/test/util/pty_util.cc
@@ -0,0 +1,45 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "test/util/pty_util.h"
+
+#include <sys/ioctl.h>
+#include <termios.h>
+
+#include "test/util/file_descriptor.h"
+#include "test/util/posix_error.h"
+
+namespace gvisor {
+namespace testing {
+
+PosixErrorOr<FileDescriptor> OpenSlave(const FileDescriptor& master) {
+  // Get pty index.
+  int n;
+  int ret = ioctl(master.get(), TIOCGPTN, &n);
+  if (ret < 0) {
+    return PosixError(errno, "ioctl(TIOCGPTN) failed");
+  }
+
+  // Unlock pts.
+  int unlock = 0;
+  ret = ioctl(master.get(), TIOCSPTLCK, &unlock);
+  if (ret < 0) {
+    return PosixError(errno, "ioctl(TIOSPTLCK) failed");
+  }
+
+  return Open(absl::StrCat("/dev/pts/", n), O_RDWR | O_NONBLOCK);
+}
+
+}  // namespace testing
+}  // namespace gvisor