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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 vfs2
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/errors/linuxerr"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/fs/lock"
"gvisor.dev/gvisor/pkg/sentry/kernel"
)
// Flock implements linux syscall flock(2).
func Flock(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
fd := args[0].Int()
operation := args[1].Int()
file := t.GetFileVFS2(fd)
if file == nil {
// flock(2): EBADF fd is not an open file descriptor.
return 0, nil, linuxerr.EBADF
}
defer file.DecRef(t)
nonblocking := operation&linux.LOCK_NB != 0
operation &^= linux.LOCK_NB
var blocker lock.Blocker
if !nonblocking {
blocker = t
}
switch operation {
case linux.LOCK_EX:
if err := file.LockBSD(t, int32(t.TGIDInRoot()), lock.WriteLock, blocker); err != nil {
return 0, nil, err
}
case linux.LOCK_SH:
if err := file.LockBSD(t, int32(t.TGIDInRoot()), lock.ReadLock, blocker); err != nil {
return 0, nil, err
}
case linux.LOCK_UN:
if err := file.UnlockBSD(t); err != nil {
return 0, nil, err
}
default:
// flock(2): EINVAL operation is invalid.
return 0, nil, linuxerr.EINVAL
}
return 0, nil, nil
}
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