1 files changed, 87 insertions, 0 deletions
diff --git a/pkg/sentry/fs/proc/uptime.go b/pkg/sentry/fs/proc/uptime.go
new file mode 100644
index 000000000..35c3851e1
--- /dev/null
+++ b/pkg/sentry/fs/proc/uptime.go
@@ -0,0 +1,87 @@
+// 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 proc
+
+import (
+	"fmt"
+	"io"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"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"
+)
+
+// uptime is a file containing the system uptime.
+//
+// +stateify savable
+type uptime struct {
+	fsutil.SimpleFileInode
+
+	// The "start time" of the sandbox.
+	startTime ktime.Time
+}
+
+// newUptime returns a new uptime file.
+func newUptime(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+	u := &uptime{
+		SimpleFileInode: *fsutil.NewSimpleFileInode(ctx, fs.RootOwner, fs.FilePermsFromMode(0444), linux.PROC_SUPER_MAGIC),
+		startTime:       ktime.NowFromContext(ctx),
+	}
+	return newProcInode(u, msrc, fs.SpecialFile, nil)
+}
+
+// GetFile implements fs.InodeOperations.GetFile.
+func (u *uptime) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	return fs.NewFile(ctx, dirent, flags, &uptimeFile{startTime: u.startTime}), nil
+}
+
+// +stateify savable
+type uptimeFile struct {
+	fsutil.FileGenericSeek          `state:"nosave"`
+	fsutil.FileNoIoctl              `state:"nosave"`
+	fsutil.FileNoMMap               `state:"nosave"`
+	fsutil.FileNoSplice             `state:"nosave"`
+	fsutil.FileNoWrite              `state:"nosave"`
+	fsutil.FileNoopFlush            `state:"nosave"`
+	fsutil.FileNoopFsync            `state:"nosave"`
+	fsutil.FileNoopRelease          `state:"nosave"`
+	fsutil.FileNotDirReaddir        `state:"nosave"`
+	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
+	waiter.AlwaysReady              `state:"nosave"`
+
+	startTime ktime.Time
+}
+
+// Read implements fs.FileOperations.Read.
+func (f *uptimeFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
+	if offset < 0 {
+		return 0, syserror.EINVAL
+	}
+
+	now := ktime.NowFromContext(ctx)
+	// Pretend that we've spent zero time sleeping (second number).
+	s := []byte(fmt.Sprintf("%.2f 0.00\n", now.Sub(f.startTime).Seconds()))
+	if offset >= int64(len(s)) {
+		return 0, io.EOF
+	}
+
+	n, err := dst.CopyOut(ctx, s[offset:])
+	return int64(n), err
+}