/
initrd.go
111 lines (104 loc) · 3.01 KB
/
initrd.go
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// Copyright 2020 the u-root Authors. All rights reserved
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package boot
import (
"bytes"
"fmt"
"io"
"os"
"strings"
"github.com/u-root/u-root/pkg/cpio"
"github.com/u-root/uio/uio"
)
// CatInitrdsWithFileCache lazily reads up multiple initrds into single tmpfs file
// and return a os.File disguising as a io.ReaderAt.
// It starts processing after first ReadAt call is made.
func CatInitrdsWithFileCache(initrds ...io.Reader) io.ReaderAt {
var names []string
for _, initrd := range initrds {
names = append(names, stringer(initrd))
}
return uio.NewLazyOpenerAt(strings.Join(names, ","), func() (io.ReaderAt, error) {
f, err := os.CreateTemp("", "combined-initrd")
if err != nil {
return nil, err
}
defer f.Close()
for i, ireader := range initrds {
size, err := io.Copy(f, ireader)
if err != nil {
return nil, err
}
// Don't pad the ending or an already aligned file.
if i != len(initrds)-1 && size%512 != 0 {
padding := make([]byte, 512-(size%512))
nr, err := f.Write(padding)
if err != nil {
return nil, err
}
if nr != len(padding) {
return nil, fmt.Errorf("write padding: %v", err)
}
}
}
if err := f.Sync(); err != nil {
return nil, err
}
// Return a read-only copy.
readOnlyF, err := os.Open(f.Name())
if err != nil {
return nil, err
}
return readOnlyF, nil
})
}
// CatInitrds concatenates initrds on first ReadAt call from a list of
// io.ReaderAts, pads them to a 512 byte boundary.
func CatInitrds(initrds ...io.ReaderAt) io.ReaderAt {
var names []string
for _, initrd := range initrds {
names = append(names, stringer(initrd))
}
return uio.NewLazyOpenerAt(strings.Join(names, ","), func() (io.ReaderAt, error) {
buf := new(bytes.Buffer)
for i, ireader := range initrds {
size, err := buf.ReadFrom(uio.Reader(ireader))
if err != nil {
return nil, err
}
// Don't pad the ending or an already aligned file.
if i != len(initrds)-1 && size%512 != 0 {
padding := make([]byte, 512-(size%512))
buf.Write(padding)
}
}
// Buffer doesn't implement ReadAt, so wrap in NewReader
return bytes.NewReader(buf.Bytes()), nil
})
}
// CreateInitrd creates an initrd with the collection of files passed in.
func CreateInitrd(files ...string) (io.ReaderAt, error) {
b := &bytes.Buffer{}
archiver, err := cpio.Format("newc")
if err != nil {
return nil, err
}
w := archiver.Writer(b)
cr := cpio.NewRecorder()
// to deconflict names, we may want to prepend the names with
// kexec_extra/ or something.
for _, n := range files {
rec, err := cr.GetRecord(n)
if err != nil {
return nil, fmt.Errorf("getting record of %q failed: %v", n, err)
}
if err := w.WriteRecord(rec); err != nil {
return nil, fmt.Errorf("writing record %q failed: %v", n, err)
}
}
if err := cpio.WriteTrailer(w); err != nil {
return nil, fmt.Errorf("error writing trailer record: %v", err)
}
return bytes.NewReader(b.Bytes()), nil
}