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// 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 fdpipe
import (
"fmt"
"io/ioutil"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sync"
)
// beforeSave is invoked by stateify.
func (p *pipeOperations) beforeSave() {
if p.flags.Read {
data, err := ioutil.ReadAll(p.file)
if err != nil && !isBlockError(err) {
panic(fmt.Sprintf("failed to read from pipe: %v", err))
}
p.readAheadBuffer = append(p.readAheadBuffer, data...)
} else if p.flags.Write {
file, err := p.opener.NonBlockingOpen(context.Background(), fs.PermMask{Write: true})
if err != nil {
panic(&fs.ErrSaveRejection{
Err: fmt.Errorf("write-only pipe end cannot be re-opened as %#v: %w", p, err),
})
}
file.Close()
}
}
// saveFlags is invoked by stateify.
func (p *pipeOperations) saveFlags() fs.FileFlags {
return p.flags
}
// readPipeOperationsLoading is used to ensure that write-only pipe fds are
// opened after read/write and read-only pipe fds, to avoid ENXIO when
// multiple pipe fds refer to different ends of the same pipe.
var readPipeOperationsLoading sync.WaitGroup
// loadFlags is invoked by stateify.
func (p *pipeOperations) loadFlags(flags fs.FileFlags) {
// This is a hack to ensure that readPipeOperationsLoading includes all
// readable pipe fds before any asynchronous calls to
// readPipeOperationsLoading.Wait().
if flags.Read {
readPipeOperationsLoading.Add(1)
}
p.flags = flags
}
// afterLoad is invoked by stateify.
func (p *pipeOperations) afterLoad() {
load := func() error {
if !p.flags.Read {
readPipeOperationsLoading.Wait()
} else {
defer readPipeOperationsLoading.Done()
}
var err error
p.file, err = p.opener.NonBlockingOpen(context.Background(), fs.PermMask{
Read: p.flags.Read,
Write: p.flags.Write,
})
if err != nil {
return fmt.Errorf("unable to open pipe %v: %v", p, err)
}
if err := p.init(); err != nil {
return fmt.Errorf("unable to initialize pipe %v: %v", p, err)
}
return nil
}
// Do background opening of pipe ends. Note for write-only pipe ends we
// have to do it asynchronously to avoid blocking the restore.
fs.Async(fs.CatchError(load))
}
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