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// Copyright 2018 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 (
"syscall"
"unsafe"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sentry/fs"
ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
)
// NulByte is a single NUL byte. It is passed to readlinkat as an empty string.
var NulByte byte = '\x00'
func createLink(fd int, name string, linkName string) error {
namePtr, err := syscall.BytePtrFromString(name)
if err != nil {
return err
}
linkNamePtr, err := syscall.BytePtrFromString(linkName)
if err != nil {
return err
}
_, _, errno := syscall.Syscall(
syscall.SYS_SYMLINKAT,
uintptr(unsafe.Pointer(namePtr)),
uintptr(fd),
uintptr(unsafe.Pointer(linkNamePtr)))
if errno != 0 {
return errno
}
return nil
}
func readLink(fd int) (string, error) {
// Buffer sizing copied from os.Readlink.
for l := 128; ; l *= 2 {
b := make([]byte, l)
n, _, errno := syscall.Syscall6(
syscall.SYS_READLINKAT,
uintptr(fd),
uintptr(unsafe.Pointer(&NulByte)), // ""
uintptr(unsafe.Pointer(&b[0])),
uintptr(l),
0, 0)
if errno != 0 {
return "", errno
}
if n < uintptr(l) {
return string(b[:n]), nil
}
}
}
func unlinkAt(fd int, name string, dir bool) error {
namePtr, err := syscall.BytePtrFromString(name)
if err != nil {
return err
}
var flags uintptr
if dir {
flags = linux.AT_REMOVEDIR
}
_, _, errno := syscall.Syscall(
syscall.SYS_UNLINKAT,
uintptr(fd),
uintptr(unsafe.Pointer(namePtr)),
flags,
)
if errno != 0 {
return errno
}
return nil
}
func timespecFromTimestamp(t ktime.Time, omit, setSysTime bool) syscall.Timespec {
if omit {
return syscall.Timespec{0, linux.UTIME_OMIT}
}
if setSysTime {
return syscall.Timespec{0, linux.UTIME_NOW}
}
return syscall.NsecToTimespec(t.Nanoseconds())
}
func setTimestamps(fd int, ts fs.TimeSpec) error {
if ts.ATimeOmit && ts.MTimeOmit {
return nil
}
var sts [2]syscall.Timespec
sts[0] = timespecFromTimestamp(ts.ATime, ts.ATimeOmit, ts.ATimeSetSystemTime)
sts[1] = timespecFromTimestamp(ts.MTime, ts.MTimeOmit, ts.MTimeSetSystemTime)
_, _, errno := syscall.Syscall6(
syscall.SYS_UTIMENSAT,
uintptr(fd),
0, /* path */
uintptr(unsafe.Pointer(&sts)),
0, /* flags */
0, 0)
if errno != 0 {
return errno
}
return nil
}
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