112 lines
3.2 KiB
Go
112 lines
3.2 KiB
Go
/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package syscallx
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import (
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"syscall"
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"unsafe"
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)
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type reparseDataBuffer struct {
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ReparseTag uint32
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ReparseDataLength uint16
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Reserved uint16
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// GenericReparseBuffer
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reparseBuffer byte
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}
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type mountPointReparseBuffer struct {
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SubstituteNameOffset uint16
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SubstituteNameLength uint16
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PrintNameOffset uint16
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PrintNameLength uint16
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PathBuffer [1]uint16
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}
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type symbolicLinkReparseBuffer struct {
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SubstituteNameOffset uint16
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SubstituteNameLength uint16
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PrintNameOffset uint16
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PrintNameLength uint16
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Flags uint32
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PathBuffer [1]uint16
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}
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const (
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_IO_REPARSE_TAG_MOUNT_POINT = 0xA0000003
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_SYMLINK_FLAG_RELATIVE = 1
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)
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// Readlink returns the destination of the named symbolic link.
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func Readlink(path string, buf []byte) (n int, err error) {
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fd, err := syscall.CreateFile(syscall.StringToUTF16Ptr(path), syscall.GENERIC_READ, 0, nil, syscall.OPEN_EXISTING,
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syscall.FILE_FLAG_OPEN_REPARSE_POINT|syscall.FILE_FLAG_BACKUP_SEMANTICS, 0)
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if err != nil {
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return -1, err
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}
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defer syscall.CloseHandle(fd)
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rdbbuf := make([]byte, syscall.MAXIMUM_REPARSE_DATA_BUFFER_SIZE)
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var bytesReturned uint32
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err = syscall.DeviceIoControl(fd, syscall.FSCTL_GET_REPARSE_POINT, nil, 0, &rdbbuf[0], uint32(len(rdbbuf)), &bytesReturned, nil)
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if err != nil {
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return -1, err
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}
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rdb := (*reparseDataBuffer)(unsafe.Pointer(&rdbbuf[0]))
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var s string
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switch rdb.ReparseTag {
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case syscall.IO_REPARSE_TAG_SYMLINK:
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data := (*symbolicLinkReparseBuffer)(unsafe.Pointer(&rdb.reparseBuffer))
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p := (*[0xffff]uint16)(unsafe.Pointer(&data.PathBuffer[0]))
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s = syscall.UTF16ToString(p[data.SubstituteNameOffset/2 : (data.SubstituteNameOffset+data.SubstituteNameLength)/2])
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if data.Flags&_SYMLINK_FLAG_RELATIVE == 0 {
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if len(s) >= 4 && s[:4] == `\??\` {
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s = s[4:]
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switch {
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case len(s) >= 2 && s[1] == ':': // \??\C:\foo\bar
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// do nothing
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case len(s) >= 4 && s[:4] == `UNC\`: // \??\UNC\foo\bar
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s = `\\` + s[4:]
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default:
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// unexpected; do nothing
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}
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} else {
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// unexpected; do nothing
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}
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}
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case _IO_REPARSE_TAG_MOUNT_POINT:
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data := (*mountPointReparseBuffer)(unsafe.Pointer(&rdb.reparseBuffer))
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p := (*[0xffff]uint16)(unsafe.Pointer(&data.PathBuffer[0]))
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s = syscall.UTF16ToString(p[data.SubstituteNameOffset/2 : (data.SubstituteNameOffset+data.SubstituteNameLength)/2])
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if len(s) >= 4 && s[:4] == `\??\` { // \??\C:\foo\bar
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if len(s) < 48 || s[:11] != `\??\Volume{` {
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s = s[4:]
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}
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} else {
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// unexpected; do nothing
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}
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default:
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// the path is not a symlink or junction but another type of reparse
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// point
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return -1, syscall.ENOENT
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}
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n = copy(buf, []byte(s))
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return n, nil
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}
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