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53 lines
1.4 KiB
Go
53 lines
1.4 KiB
Go
// +build linux
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// Package memfd provides a wrapper to linux memfd
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package memfd
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import (
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"fmt"
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"io"
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"os"
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"golang.org/x/sys/unix"
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)
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const createFlag = unix.MFD_CLOEXEC | unix.MFD_ALLOW_SEALING
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const roSeal = unix.F_SEAL_SEAL | unix.F_SEAL_SHRINK | unix.F_SEAL_GROW | unix.F_SEAL_WRITE
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// New creates a new memfd, caller need to close the file
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func New(name string) (*os.File, error) {
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fd, err := unix.MemfdCreate(name, createFlag)
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if err != nil {
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return nil, fmt.Errorf("memfd: memfd_create failed %v", err)
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}
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file := os.NewFile(uintptr(fd), name)
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if file == nil {
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unix.Close(fd)
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return nil, fmt.Errorf("memfd: MewFile failed")
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}
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return file, nil
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}
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// DupToMemfd reads content from reader to sealed (readonly) memfd for given name
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func DupToMemfd(name string, reader io.Reader) (*os.File, error) {
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file, err := New(name)
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if err != nil {
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return nil, fmt.Errorf("DupToMemfd: new memfd failed %v", err)
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}
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// linux syscall sendfile might be more efficient here if reader is a file
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if _, err = io.Copy(file, reader); err != nil {
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file.Close()
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return nil, fmt.Errorf("DupToMemfd: memfd io copy failed(%v)", err)
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}
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// make memfd readonly
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if _, err = unix.FcntlInt(file.Fd(), unix.F_ADD_SEALS, roSeal); err != nil {
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file.Close()
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return nil, fmt.Errorf("DupToMemfd: memfd seal failed(%v)", err)
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}
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if _, err := file.Seek(0, 0); err != nil {
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file.Close()
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return nil, fmt.Errorf("DupToMemfd: seek failed(%v)", err)
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}
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return file, nil
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}
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