github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/fsimpl/host/save_restore.go (about)

     1  // Copyright 2020 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package host
    16  
    17  import (
    18  	"fmt"
    19  	"io"
    20  	"sync/atomic"
    21  
    22  	"golang.org/x/sys/unix"
    23  	"github.com/SagerNet/gvisor/pkg/fdnotifier"
    24  	"github.com/SagerNet/gvisor/pkg/hostarch"
    25  	"github.com/SagerNet/gvisor/pkg/safemem"
    26  	"github.com/SagerNet/gvisor/pkg/sentry/hostfd"
    27  )
    28  
    29  // beforeSave is invoked by stateify.
    30  func (i *inode) beforeSave() {
    31  	if !i.savable {
    32  		panic("host.inode is not savable")
    33  	}
    34  	if i.ftype == unix.S_IFIFO {
    35  		// If this pipe FD is readable, drain it so that bytes in the pipe can
    36  		// be read after restore. (This is a legacy VFS1 feature.) We don't
    37  		// know if the pipe FD is readable, so just try reading and tolerate
    38  		// EBADF from the read.
    39  		i.bufMu.Lock()
    40  		defer i.bufMu.Unlock()
    41  		var buf [hostarch.PageSize]byte
    42  		for {
    43  			n, err := hostfd.Preadv2(int32(i.hostFD), safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf[:])), -1 /* offset */, 0 /* flags */)
    44  			if n != 0 {
    45  				i.buf = append(i.buf, buf[:n]...)
    46  			}
    47  			if err != nil {
    48  				if err == io.EOF || err == unix.EAGAIN || err == unix.EBADF {
    49  					break
    50  				}
    51  				panic(fmt.Errorf("host.inode.beforeSave: buffering from pipe failed: %v", err))
    52  			}
    53  		}
    54  		if len(i.buf) != 0 {
    55  			atomic.StoreUint32(&i.haveBuf, 1)
    56  		}
    57  	}
    58  }
    59  
    60  // afterLoad is invoked by stateify.
    61  func (i *inode) afterLoad() {
    62  	if i.mayBlock {
    63  		if err := unix.SetNonblock(i.hostFD, true); err != nil {
    64  			panic(fmt.Sprintf("host.inode.afterLoad: failed to set host FD %d non-blocking: %v", i.hostFD, err))
    65  		}
    66  		if err := fdnotifier.AddFD(int32(i.hostFD), &i.queue); err != nil {
    67  			panic(fmt.Sprintf("host.inode.afterLoad: fdnotifier.AddFD(%d) failed: %v", i.hostFD, err))
    68  		}
    69  	}
    70  }
    71  
    72  // afterLoad is invoked by stateify.
    73  func (c *ConnectedEndpoint) afterLoad() {
    74  	if err := c.initFromOptions(); err != nil {
    75  		panic(fmt.Sprintf("initFromOptions failed: %v", err))
    76  	}
    77  }