1 files changed, 144 insertions, 0 deletions
diff --git a/pkg/sentry/fs/timerfd/timerfd.go b/pkg/sentry/fs/timerfd/timerfd.go
new file mode 100644
index 000000000..ae58f6fd7
--- /dev/null
+++ b/pkg/sentry/fs/timerfd/timerfd.go
@@ -0,0 +1,144 @@
+// Copyright 2018 Google Inc.
+//
+// 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 timerfd implements the semantics of Linux timerfd objects as
+// described by timerfd_create(2).
+package timerfd
+
+import (
+	"sync/atomic"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/anon"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
+	ktime "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// TimerOperations implements fs.FileOperations for timerfds.
+type TimerOperations struct {
+	fsutil.ZeroSeek      `state:"nosave"`
+	fsutil.NotDirReaddir `state:"nosave"`
+	fsutil.NoFsync       `state:"nosave"`
+	fsutil.NoopFlush     `state:"nosave"`
+	fsutil.NoMMap        `state:"nosave"`
+	fsutil.NoIoctl       `state:"nosave"`
+
+	events waiter.Queue `state:"nosave"`
+	timer  *ktime.Timer
+
+	// val is the number of timer expirations since the last successful call to
+	// Readv, Preadv, or SetTime. val is accessed using atomic memory
+	// operations.
+	val uint64
+}
+
+// NewFile returns a timerfd File that receives time from c.
+func NewFile(ctx context.Context, c ktime.Clock) *fs.File {
+	dirent := fs.NewDirent(anon.NewInode(ctx), "anon_inode:[timerfd]")
+	tops := &TimerOperations{}
+	tops.timer = ktime.NewTimer(c, tops)
+	// Timerfds reject writes, but the Write flag must be set in order to
+	// ensure that our Writev/Pwritev methods actually get called to return
+	// the correct errors.
+	return fs.NewFile(ctx, dirent, fs.FileFlags{Read: true, Write: true}, tops)
+}
+
+// Release implements fs.FileOperations.Release.
+func (t *TimerOperations) Release() {
+	t.timer.Destroy()
+}
+
+// PauseTimer pauses the associated Timer.
+func (t *TimerOperations) PauseTimer() {
+	t.timer.Pause()
+}
+
+// ResumeTimer resumes the associated Timer.
+func (t *TimerOperations) ResumeTimer() {
+	t.timer.Resume()
+}
+
+// Clock returns the associated Timer's Clock.
+func (t *TimerOperations) Clock() ktime.Clock {
+	return t.timer.Clock()
+}
+
+// GetTime returns the associated Timer's setting and the time at which it was
+// observed.
+func (t *TimerOperations) GetTime() (ktime.Time, ktime.Setting) {
+	return t.timer.Get()
+}
+
+// SetTime atomically changes the associated Timer's setting, resets the number
+// of expirations to 0, and returns the previous setting and the time at which
+// it was observed.
+func (t *TimerOperations) SetTime(s ktime.Setting) (ktime.Time, ktime.Setting) {
+	return t.timer.SwapAnd(s, func() { atomic.StoreUint64(&t.val, 0) })
+}
+
+// Readiness implements waiter.Waitable.Readiness.
+func (t *TimerOperations) Readiness(mask waiter.EventMask) waiter.EventMask {
+	var ready waiter.EventMask
+	if atomic.LoadUint64(&t.val) != 0 {
+		ready |= waiter.EventIn
+	}
+	return ready
+}
+
+// EventRegister implements waiter.Waitable.EventRegister.
+func (t *TimerOperations) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
+	t.events.EventRegister(e, mask)
+}
+
+// EventUnregister implements waiter.Waitable.EventUnregister.
+func (t *TimerOperations) EventUnregister(e *waiter.Entry) {
+	t.events.EventUnregister(e)
+}
+
+// Read implements fs.FileOperations.Read.
+func (t *TimerOperations) Read(ctx context.Context, file *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
+	const sizeofUint64 = 8
+	if dst.NumBytes() < sizeofUint64 {
+		return 0, syserror.EINVAL
+	}
+	if val := atomic.SwapUint64(&t.val, 0); val != 0 {
+		var buf [sizeofUint64]byte
+		usermem.ByteOrder.PutUint64(buf[:], val)
+		if _, err := dst.CopyOut(ctx, buf[:]); err != nil {
+			// Linux does not undo consuming the number of expirations even if
+			// writing to userspace fails.
+			return 0, err
+		}
+		return sizeofUint64, nil
+	}
+	return 0, syserror.ErrWouldBlock
+}
+
+// Write implements fs.FileOperations.Write.
+func (t *TimerOperations) Write(context.Context, *fs.File, usermem.IOSequence, int64) (int64, error) {
+	return 0, syserror.EINVAL
+}
+
+// Notify implements ktime.TimerListener.Notify.
+func (t *TimerOperations) Notify(exp uint64) {
+	atomic.AddUint64(&t.val, exp)
+	t.events.Notify(waiter.EventIn)
+}
+
+// Destroy implements ktime.TimerListener.Destroy.
+func (t *TimerOperations) Destroy() {}