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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 host
import (
"context"
"fmt"
"io"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/fdnotifier"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/safemem"
"gvisor.dev/gvisor/pkg/sentry/hostfd"
"gvisor.dev/gvisor/pkg/sentry/vfs"
)
// MakeRestoreID creates a RestoreID for a given application FD. The application
// FD remains the same between restores, e.g. stdout=2 before and after restore,
// but the host FD that is maps to can change between restores. This ID is used
// to map application FDs to their respective FD after a restore happens.
func MakeRestoreID(containerName string, fd int) vfs.RestoreID {
return vfs.RestoreID{
ContainerName: containerName,
Path: fmt.Sprintf("host:%d", fd),
}
}
// beforeSave is invoked by stateify.
func (i *inode) beforeSave() {
if !i.savable {
panic("host.inode is not savable")
}
if i.ftype == unix.S_IFIFO {
// If this pipe FD is readable, drain it so that bytes in the pipe can
// be read after restore. (This is a legacy VFS1 feature.) We don't
// know if the pipe FD is readable, so just try reading and tolerate
// EBADF from the read.
i.bufMu.Lock()
defer i.bufMu.Unlock()
var buf [hostarch.PageSize]byte
for {
n, err := hostfd.Preadv2(int32(i.hostFD), safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf[:])), -1 /* offset */, 0 /* flags */)
if n != 0 {
i.buf = append(i.buf, buf[:n]...)
}
if err != nil {
if err == io.EOF || err == unix.EAGAIN || err == unix.EBADF {
break
}
panic(fmt.Errorf("host.inode.beforeSave: buffering from pipe failed: %v", err))
}
}
if len(i.buf) != 0 {
i.haveBuf.Store(1)
}
}
}
// afterLoad is invoked by stateify.
func (i *inode) afterLoad(ctx context.Context) {
fdmap := vfs.RestoreFilesystemFDMapFromContext(ctx)
fd, ok := fdmap[i.restoreKey]
if !ok {
panic(fmt.Sprintf("no host FD available for %+v, map: %v", i.restoreKey, fdmap))
}
i.hostFD = fd
if i.epollable {
if err := unix.SetNonblock(i.hostFD, true); err != nil {
panic(fmt.Sprintf("host.inode.afterLoad: failed to set host FD %d non-blocking: %v", i.hostFD, err))
}
if err := fdnotifier.AddFD(int32(i.hostFD), &i.queue); err != nil {
panic(fmt.Sprintf("host.inode.afterLoad: fdnotifier.AddFD(%d) failed: %v", i.hostFD, err))
}
}
}
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