github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/syscalls/linux/sys_lseek.go (about)

     1  // Copyright 2018 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 linux
    16  
    17  import (
    18  	"github.com/SagerNet/gvisor/pkg/errors/linuxerr"
    19  	"github.com/SagerNet/gvisor/pkg/sentry/arch"
    20  	"github.com/SagerNet/gvisor/pkg/sentry/fs"
    21  	"github.com/SagerNet/gvisor/pkg/sentry/kernel"
    22  	"github.com/SagerNet/gvisor/pkg/syserror"
    23  )
    24  
    25  // LINT.IfChange
    26  
    27  // Lseek implements linux syscall lseek(2).
    28  func Lseek(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
    29  	fd := args[0].Int()
    30  	offset := args[1].Int64()
    31  	whence := args[2].Int()
    32  
    33  	file := t.GetFile(fd)
    34  	if file == nil {
    35  		return 0, nil, linuxerr.EBADF
    36  	}
    37  	defer file.DecRef(t)
    38  
    39  	var sw fs.SeekWhence
    40  	switch whence {
    41  	case 0:
    42  		sw = fs.SeekSet
    43  	case 1:
    44  		sw = fs.SeekCurrent
    45  	case 2:
    46  		sw = fs.SeekEnd
    47  	default:
    48  		return 0, nil, linuxerr.EINVAL
    49  	}
    50  
    51  	offset, serr := file.Seek(t, sw, offset)
    52  	err := handleIOError(t, false /* partialResult */, serr, syserror.ERESTARTSYS, "lseek", file)
    53  	if err != nil {
    54  		return 0, nil, err
    55  	}
    56  	return uintptr(offset), nil, err
    57  }
    58  
    59  // LINT.ThenChange(vfs2/read_write.go)