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linux.go
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linux.go
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// Copyright 2018 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 (
"errors"
"fmt"
"io"
"io/ioutil"
"log"
"os"
"github.com/u-root/u-root/pkg/cpio"
"github.com/u-root/u-root/pkg/kexec"
"github.com/u-root/u-root/pkg/uio"
)
// ErrKernelMissing is returned by LinuxImage.Pack if no kernel is given.
var ErrKernelMissing = errors.New("must have non-nil kernel")
// LinuxImage implements OSImage for a Linux kernel + initramfs.
type LinuxImage struct {
Kernel io.ReaderAt
Initrd io.ReaderAt
Cmdline string
}
var _ OSImage = &LinuxImage{}
// NewLinuxImageFromArchive reads a netboot21 Linux OSImage from a CPIO file
// archive.
func NewLinuxImageFromArchive(a *cpio.Archive) (*LinuxImage, error) {
kernel, ok := a.Files["modules/kernel/content"]
if !ok {
return nil, fmt.Errorf("kernel missing from archive")
}
li := &LinuxImage{}
li.Kernel = kernel
if params, ok := a.Files["modules/kernel/params"]; ok {
b, err := uio.ReadAll(params)
if err != nil {
return nil, err
}
li.Cmdline = string(b)
}
if initrd, ok := a.Files["modules/initrd/content"]; ok {
li.Initrd = initrd
}
return li, nil
}
// Pack implements OSImage.Pack and writes all necessary files to the modules
// directory of `sw`.
func (li *LinuxImage) Pack(sw cpio.RecordWriter) error {
if err := sw.WriteRecord(cpio.Directory("modules", 0700)); err != nil {
return err
}
if err := sw.WriteRecord(cpio.Directory("modules/kernel", 0700)); err != nil {
return err
}
if li.Kernel == nil {
return ErrKernelMissing
}
kernel, err := uio.ReadAll(li.Kernel)
if err != nil {
return err
}
if err := sw.WriteRecord(cpio.StaticFile("modules/kernel/content", string(kernel), 0700)); err != nil {
return err
}
if err := sw.WriteRecord(cpio.StaticFile("modules/kernel/params", li.Cmdline, 0700)); err != nil {
return err
}
if li.Initrd != nil {
if err := sw.WriteRecord(cpio.Directory("modules/initrd", 0700)); err != nil {
return err
}
initrd, err := uio.ReadAll(li.Initrd)
if err != nil {
return err
}
if err := sw.WriteRecord(cpio.StaticFile("modules/initrd/content", string(initrd), 0700)); err != nil {
return err
}
}
return sw.WriteRecord(cpio.StaticFile("package_type", "linux", 0700))
}
func copyToFile(r io.Reader) (*os.File, error) {
f, err := ioutil.TempFile("", "nerf-netboot")
if err != nil {
return nil, err
}
defer f.Close()
if _, err := io.Copy(f, r); err != nil {
return nil, err
}
if err := f.Sync(); err != nil {
return nil, err
}
readOnlyF, err := os.Open(f.Name())
if err != nil {
return nil, err
}
return readOnlyF, nil
}
// ExecutionInfo implements OSImage.ExecutionInfo.
func (li *LinuxImage) ExecutionInfo(l *log.Logger) {
k, err := copyToFile(uio.Reader(li.Kernel))
if err != nil {
l.Printf("Copying kernel to file: %v", err)
}
defer k.Close()
var i *os.File
if li.Initrd != nil {
i, err = copyToFile(uio.Reader(li.Initrd))
if err != nil {
l.Printf("Copying initrd to file: %v", err)
}
defer i.Close()
}
l.Printf("Kernel: %s", k.Name())
if i != nil {
l.Printf("Initrd: %s", i.Name())
}
l.Printf("Command line: %s", li.Cmdline)
}
// Execute implements OSImage.Execute and kexec's the kernel with its initramfs.
func (li *LinuxImage) Execute() error {
k, err := copyToFile(uio.Reader(li.Kernel))
if err != nil {
return err
}
defer k.Close()
var i *os.File
if li.Initrd != nil {
i, err = copyToFile(uio.Reader(li.Initrd))
if err != nil {
return err
}
defer i.Close()
}
if err := kexec.FileLoad(k, i, li.Cmdline); err != nil {
return err
}
return kexec.Reboot()
}