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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 gofer
import (
"io"
"gvisor.dev/gvisor/pkg/fd"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/p9"
"gvisor.dev/gvisor/pkg/refs"
"gvisor.dev/gvisor/pkg/secio"
"gvisor.dev/gvisor/pkg/sentry/context"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/safemem"
)
// handles are the open handles of a gofer file. They are reference counted to
// support open handle sharing between files for read only filesystems.
//
// If Host != nil then it will be used exclusively over File.
type handles struct {
refs.AtomicRefCount
// File is a p9.File handle. Must not be nil.
File contextFile
// Host is an *fd.FD handle. May be nil.
Host *fd.FD
// isHostBorrowed tells whether 'Host' is owned or borrowed. If owned, it's
// closed on destruction, otherwise it's released.
isHostBorrowed bool
}
// DecRef drops a reference on handles.
func (h *handles) DecRef() {
h.DecRefWithDestructor(func() {
if h.Host != nil {
if h.isHostBorrowed {
h.Host.Release()
} else {
if err := h.Host.Close(); err != nil {
log.Warningf("error closing host file: %v", err)
}
}
}
// FIXME(b/38173783): Context is not plumbed here.
if err := h.File.close(context.Background()); err != nil {
log.Warningf("error closing p9 file: %v", err)
}
})
}
func newHandles(ctx context.Context, file contextFile, flags fs.FileFlags) (*handles, error) {
_, newFile, err := file.walk(ctx, nil)
if err != nil {
return nil, err
}
var p9flags p9.OpenFlags
switch {
case flags.Read && flags.Write:
p9flags = p9.ReadWrite
case flags.Read && !flags.Write:
p9flags = p9.ReadOnly
case !flags.Read && flags.Write:
p9flags = p9.WriteOnly
default:
panic("impossible fs.FileFlags")
}
hostFile, _, _, err := newFile.open(ctx, p9flags)
if err != nil {
newFile.close(ctx)
return nil, err
}
h := handles{
File: newFile,
Host: hostFile,
}
h.EnableLeakCheck("gofer.handles")
return &h, nil
}
type handleReadWriter struct {
ctx context.Context
h *handles
off int64
}
func (h *handles) readWriterAt(ctx context.Context, offset int64) *handleReadWriter {
return &handleReadWriter{ctx, h, offset}
}
// ReadToBlocks implements safemem.Reader.ReadToBlocks.
func (rw *handleReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
var r io.Reader
if rw.h.Host != nil {
r = secio.NewOffsetReader(rw.h.Host, rw.off)
} else {
r = &p9.ReadWriterFile{File: rw.h.File.file, Offset: uint64(rw.off)}
}
rw.ctx.UninterruptibleSleepStart(false)
defer rw.ctx.UninterruptibleSleepFinish(false)
n, err := safemem.FromIOReader{r}.ReadToBlocks(dsts)
rw.off += int64(n)
return n, err
}
// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
func (rw *handleReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
var w io.Writer
if rw.h.Host != nil {
w = secio.NewOffsetWriter(rw.h.Host, rw.off)
} else {
w = &p9.ReadWriterFile{File: rw.h.File.file, Offset: uint64(rw.off)}
}
rw.ctx.UninterruptibleSleepStart(false)
defer rw.ctx.UninterruptibleSleepFinish(false)
n, err := safemem.FromIOWriter{w}.WriteFromBlocks(srcs)
rw.off += int64(n)
return n, err
}
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