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// Copyright 2020 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 fdimport provides the Import function.
package fdimport
import (
"fmt"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/fd"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/fs/host"
hostvfs2 "gvisor.dev/gvisor/pkg/sentry/fsimpl/host"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/vfs"
)
// Import imports a slice of FDs into the given FDTable. If console is true,
// sets up TTY for the first 3 FDs in the slice representing stdin, stdout,
// stderr. Used FDs are either closed or released. It's safe for the caller to
// close any remaining files upon return.
func Import(ctx context.Context, fdTable *kernel.FDTable, console bool, uid auth.KUID, gid auth.KGID, fds []*fd.FD) (*host.TTYFileOperations, *hostvfs2.TTYFileDescription, error) {
if kernel.VFS2Enabled {
ttyFile, err := importVFS2(ctx, fdTable, console, uid, gid, fds)
return nil, ttyFile, err
}
ttyFile, err := importFS(ctx, fdTable, console, fds)
return ttyFile, nil, err
}
func importFS(ctx context.Context, fdTable *kernel.FDTable, console bool, fds []*fd.FD) (*host.TTYFileOperations, error) {
var ttyFile *fs.File
for appFD, hostFD := range fds {
var appFile *fs.File
if console && appFD < 3 {
// Import the file as a host TTY file.
if ttyFile == nil {
var err error
appFile, err = host.ImportFile(ctx, hostFD.FD(), true /* isTTY */)
if err != nil {
return nil, err
}
defer appFile.DecRef(ctx)
_ = hostFD.Close() // FD is dup'd i ImportFile.
// Remember this in the TTY file, as we will
// use it for the other stdio FDs.
ttyFile = appFile
} else {
// Re-use the existing TTY file, as all three
// stdio FDs must point to the same fs.File in
// order to share TTY state, specifically the
// foreground process group id.
appFile = ttyFile
}
} else {
// Import the file as a regular host file.
var err error
appFile, err = host.ImportFile(ctx, hostFD.FD(), false /* isTTY */)
if err != nil {
return nil, err
}
defer appFile.DecRef(ctx)
_ = hostFD.Close() // FD is dup'd i ImportFile.
}
// Add the file to the FD map.
if err := fdTable.NewFDAt(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
return nil, err
}
}
if ttyFile == nil {
return nil, nil
}
return ttyFile.FileOperations.(*host.TTYFileOperations), nil
}
func importVFS2(ctx context.Context, fdTable *kernel.FDTable, console bool, uid auth.KUID, gid auth.KGID, stdioFDs []*fd.FD) (*hostvfs2.TTYFileDescription, error) {
k := kernel.KernelFromContext(ctx)
if k == nil {
return nil, fmt.Errorf("cannot find kernel from context")
}
var ttyFile *vfs.FileDescription
for appFD, hostFD := range stdioFDs {
var appFile *vfs.FileDescription
if console && appFD < 3 {
// Import the file as a host TTY file.
if ttyFile == nil {
var err error
appFile, err = hostvfs2.NewFD(ctx, k.HostMount(), hostFD.FD(), &hostvfs2.NewFDOptions{
Savable: true,
IsTTY: true,
VirtualOwner: true,
UID: uid,
GID: gid,
})
if err != nil {
return nil, err
}
defer appFile.DecRef(ctx)
hostFD.Release() // FD is transfered to host FD.
// Remember this in the TTY file, as we will use it for the other stdio
// FDs.
ttyFile = appFile
} else {
// Re-use the existing TTY file, as all three stdio FDs must point to
// the same fs.File in order to share TTY state, specifically the
// foreground process group id.
appFile = ttyFile
}
} else {
var err error
appFile, err = hostvfs2.NewFD(ctx, k.HostMount(), hostFD.FD(), &hostvfs2.NewFDOptions{
Savable: true,
VirtualOwner: true,
UID: uid,
GID: gid,
})
if err != nil {
return nil, err
}
defer appFile.DecRef(ctx)
hostFD.Release() // FD is transfered to host FD.
}
if err := fdTable.NewFDAtVFS2(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
return nil, err
}
}
if ttyFile == nil {
return nil, nil
}
return ttyFile.Impl().(*hostvfs2.TTYFileDescription), nil
}
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