2019-08-14 00:52:53 +00:00
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// Copyright 2019 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package vfs
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import (
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"bytes"
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"fmt"
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"io"
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"sync/atomic"
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"testing"
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/sentry/context"
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"gvisor.dev/gvisor/pkg/sentry/context/contexttest"
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"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
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"gvisor.dev/gvisor/pkg/sentry/usermem"
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"gvisor.dev/gvisor/pkg/syserror"
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)
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2019-08-16 17:18:58 +00:00
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// fileDescription is the common fd struct which a filesystem implementation
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// embeds in all of its file description implementations as required.
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type fileDescription struct {
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vfsfd FileDescription
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FileDescriptionDefaultImpl
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}
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2019-08-14 00:52:53 +00:00
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// genCountFD is a read-only FileDescriptionImpl representing a regular file
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// that contains the number of times its DynamicBytesSource.Generate()
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// implementation has been called.
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type genCountFD struct {
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2019-08-16 17:18:58 +00:00
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fileDescription
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2019-08-14 00:52:53 +00:00
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DynamicBytesFileDescriptionImpl
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count uint64 // accessed using atomic memory ops
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}
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func newGenCountFD(mnt *Mount, vfsd *Dentry) *FileDescription {
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var fd genCountFD
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fd.vfsfd.Init(&fd, mnt, vfsd)
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fd.DynamicBytesFileDescriptionImpl.SetDataSource(&fd)
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return &fd.vfsfd
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}
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// Release implements FileDescriptionImpl.Release.
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func (fd *genCountFD) Release() {
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}
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// StatusFlags implements FileDescriptionImpl.StatusFlags.
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func (fd *genCountFD) StatusFlags(ctx context.Context) (uint32, error) {
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return 0, nil
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}
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// SetStatusFlags implements FileDescriptionImpl.SetStatusFlags.
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func (fd *genCountFD) SetStatusFlags(ctx context.Context, flags uint32) error {
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return syserror.EPERM
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}
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// Stat implements FileDescriptionImpl.Stat.
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func (fd *genCountFD) Stat(ctx context.Context, opts StatOptions) (linux.Statx, error) {
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// Note that Statx.Mask == 0 in the return value.
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return linux.Statx{}, nil
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}
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// SetStat implements FileDescriptionImpl.SetStat.
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func (fd *genCountFD) SetStat(ctx context.Context, opts SetStatOptions) error {
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return syserror.EPERM
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}
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// Generate implements DynamicBytesSource.Generate.
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func (fd *genCountFD) Generate(ctx context.Context, buf *bytes.Buffer) error {
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fmt.Fprintf(buf, "%d", atomic.AddUint64(&fd.count, 1))
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return nil
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}
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func TestGenCountFD(t *testing.T) {
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ctx := contexttest.Context(t)
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creds := auth.CredentialsFromContext(ctx)
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vfsObj := New() // vfs.New()
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vfsObj.MustRegisterFilesystemType("testfs", FDTestFilesystemType{})
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mntns, err := vfsObj.NewMountNamespace(ctx, creds, "", "testfs", &NewFilesystemOptions{})
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if err != nil {
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t.Fatalf("failed to create testfs root mount: %v", err)
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}
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vd := mntns.Root()
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defer vd.DecRef()
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fd := newGenCountFD(vd.Mount(), vd.Dentry())
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defer fd.DecRef()
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// The first read causes Generate to be called to fill the FD's buffer.
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buf := make([]byte, 2)
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ioseq := usermem.BytesIOSequence(buf)
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n, err := fd.Impl().Read(ctx, ioseq, ReadOptions{})
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if n != 1 || (err != nil && err != io.EOF) {
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t.Fatalf("first Read: got (%d, %v), wanted (1, nil or EOF)", n, err)
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}
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if want := byte('1'); buf[0] != want {
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t.Errorf("first Read: got byte %c, wanted %c", buf[0], want)
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}
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// A second read without seeking is still at EOF.
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n, err = fd.Impl().Read(ctx, ioseq, ReadOptions{})
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if n != 0 || err != io.EOF {
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t.Fatalf("second Read: got (%d, %v), wanted (0, EOF)", n, err)
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}
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// Seeking to the beginning of the file causes it to be regenerated.
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n, err = fd.Impl().Seek(ctx, 0, linux.SEEK_SET)
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if n != 0 || err != nil {
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t.Fatalf("Seek: got (%d, %v), wanted (0, nil)", n, err)
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}
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n, err = fd.Impl().Read(ctx, ioseq, ReadOptions{})
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if n != 1 || (err != nil && err != io.EOF) {
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t.Fatalf("Read after Seek: got (%d, %v), wanted (1, nil or EOF)", n, err)
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}
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if want := byte('2'); buf[0] != want {
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t.Errorf("Read after Seek: got byte %c, wanted %c", buf[0], want)
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}
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// PRead at the beginning of the file also causes it to be regenerated.
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n, err = fd.Impl().PRead(ctx, ioseq, 0, ReadOptions{})
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if n != 1 || (err != nil && err != io.EOF) {
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t.Fatalf("PRead: got (%d, %v), wanted (1, nil or EOF)", n, err)
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}
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if want := byte('3'); buf[0] != want {
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t.Errorf("PRead: got byte %c, wanted %c", buf[0], want)
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}
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}
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