github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/fs/proc/uptime.go (about)

     1  // Copyright 2018 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package proc
    16  
    17  import (
    18  	"fmt"
    19  	"io"
    20  
    21  	"github.com/SagerNet/gvisor/pkg/abi/linux"
    22  	"github.com/SagerNet/gvisor/pkg/context"
    23  	"github.com/SagerNet/gvisor/pkg/errors/linuxerr"
    24  	"github.com/SagerNet/gvisor/pkg/sentry/fs"
    25  	"github.com/SagerNet/gvisor/pkg/sentry/fs/fsutil"
    26  	ktime "github.com/SagerNet/gvisor/pkg/sentry/kernel/time"
    27  	"github.com/SagerNet/gvisor/pkg/usermem"
    28  	"github.com/SagerNet/gvisor/pkg/waiter"
    29  )
    30  
    31  // LINT.IfChange
    32  
    33  // uptime is a file containing the system uptime.
    34  //
    35  // +stateify savable
    36  type uptime struct {
    37  	fsutil.SimpleFileInode
    38  
    39  	// The "start time" of the sandbox.
    40  	startTime ktime.Time
    41  }
    42  
    43  // newUptime returns a new uptime file.
    44  func newUptime(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
    45  	u := &uptime{
    46  		SimpleFileInode: *fsutil.NewSimpleFileInode(ctx, fs.RootOwner, fs.FilePermsFromMode(0444), linux.PROC_SUPER_MAGIC),
    47  		startTime:       ktime.NowFromContext(ctx),
    48  	}
    49  	return newProcInode(ctx, u, msrc, fs.SpecialFile, nil)
    50  }
    51  
    52  // GetFile implements fs.InodeOperations.GetFile.
    53  func (u *uptime) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
    54  	return fs.NewFile(ctx, dirent, flags, &uptimeFile{startTime: u.startTime}), nil
    55  }
    56  
    57  // +stateify savable
    58  type uptimeFile struct {
    59  	fsutil.FileGenericSeek          `state:"nosave"`
    60  	fsutil.FileNoIoctl              `state:"nosave"`
    61  	fsutil.FileNoMMap               `state:"nosave"`
    62  	fsutil.FileNoSplice             `state:"nosave"`
    63  	fsutil.FileNoWrite              `state:"nosave"`
    64  	fsutil.FileNoopFlush            `state:"nosave"`
    65  	fsutil.FileNoopFsync            `state:"nosave"`
    66  	fsutil.FileNoopRelease          `state:"nosave"`
    67  	fsutil.FileNotDirReaddir        `state:"nosave"`
    68  	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
    69  	waiter.AlwaysReady              `state:"nosave"`
    70  
    71  	startTime ktime.Time
    72  }
    73  
    74  // Read implements fs.FileOperations.Read.
    75  func (f *uptimeFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
    76  	if offset < 0 {
    77  		return 0, linuxerr.EINVAL
    78  	}
    79  
    80  	now := ktime.NowFromContext(ctx)
    81  	// Pretend that we've spent zero time sleeping (second number).
    82  	s := []byte(fmt.Sprintf("%.2f 0.00\n", now.Sub(f.startTime).Seconds()))
    83  	if offset >= int64(len(s)) {
    84  		return 0, io.EOF
    85  	}
    86  
    87  	n, err := dst.CopyOut(ctx, s[offset:])
    88  	return int64(n), err
    89  }
    90  
    91  // LINT.ThenChange(../../fsimpl/proc/tasks_files.go)