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

     1  // Copyright 2019 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 gofer
    16  
    17  import (
    18  	"github.com/SagerNet/gvisor/pkg/abi/linux"
    19  	"github.com/SagerNet/gvisor/pkg/context"
    20  	"github.com/SagerNet/gvisor/pkg/sentry/vfs"
    21  )
    22  
    23  func (d *dentry) isSymlink() bool {
    24  	return d.fileType() == linux.S_IFLNK
    25  }
    26  
    27  // Precondition: d.isSymlink().
    28  func (d *dentry) readlink(ctx context.Context, mnt *vfs.Mount) (string, error) {
    29  	if d.fs.opts.interop != InteropModeShared {
    30  		d.touchAtime(mnt)
    31  		d.dataMu.Lock()
    32  		if d.haveTarget {
    33  			target := d.target
    34  			d.dataMu.Unlock()
    35  			return target, nil
    36  		}
    37  	}
    38  	target, err := d.file.readlink(ctx)
    39  	if d.fs.opts.interop != InteropModeShared {
    40  		if err == nil {
    41  			d.haveTarget = true
    42  			d.target = target
    43  		}
    44  		d.dataMu.Unlock() // +checklocksforce: guaranteed locked from above.
    45  	}
    46  	return target, err
    47  }