Refactor tty codebase to use master-replica terminology.

Updates #2972

PiperOrigin-RevId: 329584905

1 files changed, 186 insertions, 0 deletions

diff --git a/pkg/sentry/fs/tty/replica.go b/pkg/sentry/fs/tty/replica.go
new file mode 100644
index 000000000..cb6cd6864
--- /dev/null
+++ b/pkg/sentry/fs/tty/replica.go
@@ -0,0 +1,186 @@
+// Copyright 2018 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.
+
+package tty
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+	"gvisor.dev/gvisor/pkg/waiter"
+	"gvisor.dev/gvisor/tools/go_marshal/primitive"
+)
+
+// LINT.IfChange
+
+// replicaInodeOperations are the fs.InodeOperations for the replica end of the
+// Terminal (pts file).
+//
+// +stateify savable
+type replicaInodeOperations struct {
+	fsutil.SimpleFileInode
+
+	// d is the containing dir.
+	d *dirInodeOperations
+
+	// t is the connected Terminal.
+	t *Terminal
+}
+
+var _ fs.InodeOperations = (*replicaInodeOperations)(nil)
+
+// newReplicaInode creates an fs.Inode for the replica end of a terminal.
+//
+// newReplicaInode takes ownership of t.
+func newReplicaInode(ctx context.Context, d *dirInodeOperations, t *Terminal, owner fs.FileOwner, p fs.FilePermissions) *fs.Inode {
+	iops := &replicaInodeOperations{
+		SimpleFileInode: *fsutil.NewSimpleFileInode(ctx, owner, p, linux.DEVPTS_SUPER_MAGIC),
+		d:               d,
+		t:               t,
+	}
+
+	return fs.NewInode(ctx, iops, d.msrc, fs.StableAttr{
+		DeviceID: ptsDevice.DeviceID(),
+		// N.B. Linux always uses inode id = tty index + 3. See
+		// fs/devpts/inode.c:devpts_pty_new.
+		//
+		// TODO(b/75267214): Since ptsDevice must be shared between
+		// different mounts, we must not assign fixed numbers.
+		InodeID: ptsDevice.NextIno(),
+		Type:    fs.CharacterDevice,
+		// See fs/devpts/inode.c:devpts_fill_super.
+		BlockSize:       1024,
+		DeviceFileMajor: linux.UNIX98_PTY_REPLICA_MAJOR,
+		DeviceFileMinor: t.n,
+	})
+}
+
+// Release implements fs.InodeOperations.Release.
+func (si *replicaInodeOperations) Release(ctx context.Context) {
+	si.t.DecRef(ctx)
+}
+
+// Truncate implements fs.InodeOperations.Truncate.
+func (*replicaInodeOperations) Truncate(context.Context, *fs.Inode, int64) error {
+	return nil
+}
+
+// GetFile implements fs.InodeOperations.GetFile.
+//
+// This may race with destruction of the terminal. If the terminal is gone, it
+// returns ENOENT.
+func (si *replicaInodeOperations) GetFile(ctx context.Context, d *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	return fs.NewFile(ctx, d, flags, &replicaFileOperations{si: si}), nil
+}
+
+// replicaFileOperations are the fs.FileOperations for the replica end of a
+// terminal.
+//
+// +stateify savable
+type replicaFileOperations struct {
+	fsutil.FilePipeSeek             `state:"nosave"`
+	fsutil.FileNotDirReaddir        `state:"nosave"`
+	fsutil.FileNoFsync              `state:"nosave"`
+	fsutil.FileNoMMap               `state:"nosave"`
+	fsutil.FileNoSplice             `state:"nosave"`
+	fsutil.FileNoopFlush            `state:"nosave"`
+	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
+
+	// si is the inode operations.
+	si *replicaInodeOperations
+}
+
+var _ fs.FileOperations = (*replicaFileOperations)(nil)
+
+// Release implements fs.FileOperations.Release.
+func (sf *replicaFileOperations) Release(context.Context) {
+}
+
+// EventRegister implements waiter.Waitable.EventRegister.
+func (sf *replicaFileOperations) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
+	sf.si.t.ld.replicaWaiter.EventRegister(e, mask)
+}
+
+// EventUnregister implements waiter.Waitable.EventUnregister.
+func (sf *replicaFileOperations) EventUnregister(e *waiter.Entry) {
+	sf.si.t.ld.replicaWaiter.EventUnregister(e)
+}
+
+// Readiness implements waiter.Waitable.Readiness.
+func (sf *replicaFileOperations) Readiness(mask waiter.EventMask) waiter.EventMask {
+	return sf.si.t.ld.replicaReadiness()
+}
+
+// Read implements fs.FileOperations.Read.
+func (sf *replicaFileOperations) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, _ int64) (int64, error) {
+	return sf.si.t.ld.inputQueueRead(ctx, dst)
+}
+
+// Write implements fs.FileOperations.Write.
+func (sf *replicaFileOperations) Write(ctx context.Context, _ *fs.File, src usermem.IOSequence, _ int64) (int64, error) {
+	return sf.si.t.ld.outputQueueWrite(ctx, src)
+}
+
+// Ioctl implements fs.FileOperations.Ioctl.
+func (sf *replicaFileOperations) Ioctl(ctx context.Context, _ *fs.File, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
+	t := kernel.TaskFromContext(ctx)
+	if t == nil {
+		// ioctl(2) may only be called from a task goroutine.
+		return 0, syserror.ENOTTY
+	}
+
+	switch cmd := args[1].Uint(); cmd {
+	case linux.FIONREAD: // linux.FIONREAD == linux.TIOCINQ
+		// Get the number of bytes in the input queue read buffer.
+		return 0, sf.si.t.ld.inputQueueReadSize(t, args)
+	case linux.TCGETS:
+		return sf.si.t.ld.getTermios(t, args)
+	case linux.TCSETS:
+		return sf.si.t.ld.setTermios(t, args)
+	case linux.TCSETSW:
+		// TODO(b/29356795): This should drain the output queue first.
+		return sf.si.t.ld.setTermios(t, args)
+	case linux.TIOCGPTN:
+		nP := primitive.Uint32(sf.si.t.n)
+		_, err := nP.CopyOut(t, args[2].Pointer())
+		return 0, err
+	case linux.TIOCGWINSZ:
+		return 0, sf.si.t.ld.windowSize(t, args)
+	case linux.TIOCSWINSZ:
+		return 0, sf.si.t.ld.setWindowSize(t, args)
+	case linux.TIOCSCTTY:
+		// Make the given terminal the controlling terminal of the
+		// calling process.
+		return 0, sf.si.t.setControllingTTY(ctx, args, false /* isMaster */)
+	case linux.TIOCNOTTY:
+		// Release this process's controlling terminal.
+		return 0, sf.si.t.releaseControllingTTY(ctx, args, false /* isMaster */)
+	case linux.TIOCGPGRP:
+		// Get the foreground process group.
+		return sf.si.t.foregroundProcessGroup(ctx, args, false /* isMaster */)
+	case linux.TIOCSPGRP:
+		// Set the foreground process group.
+		return sf.si.t.setForegroundProcessGroup(ctx, args, false /* isMaster */)
+	default:
+		maybeEmitUnimplementedEvent(ctx, cmd)
+		return 0, syserror.ENOTTY
+	}
+}
+
+// LINT.ThenChange(../../fsimpl/devpts/replica.go)