initial commit 🍓

LICENSE

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+BSD 3-Clause License
+
+Copyright (c) 2017 the gokrazy authors
+Copyright (c) 2022, oliverpool
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its
+   contributors may be used to endorse or promote products derived from
+   this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

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+# Kernel for Raspberry Pi 32 bits, for usage in gokrazy

cmd/compile/main.go

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+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"io"
+	"io/fs"
+	"log"
+	"os"
+	"os/user"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+
+	"github.com/magefile/mage/sh"
+)
+
+func main() {
+	if err := run(); err != nil {
+		log.Println(err)
+
+		os.Exit(1)
+	}
+}
+
+func execCmd(env map[string]string, stdout io.Writer, stderr io.Writer, cmd string, args ...string) func(args ...string) error {
+	return func(args2 ...string) error {
+		fmt.Println(cmd, args2)
+		_, err := sh.Exec(env, stdout, stderr, cmd, append(args, args2...)...)
+		return err
+	}
+}
+
+var kernelFolderFlag = flag.String("kernel", "./linux-sources", "folder containing the kernel to compile")
+
+func run() error {
+	flag.Parse()
+
+	// TODO new version check
+
+	kernelFolder, err := filepath.Abs(*kernelFolderFlag)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println("[kernel]", kernelFolder)
+
+	dockerRun := execCmd(nil, os.Stdout, os.Stderr,
+		"docker",
+		"run",
+		"-it",  // to forward interrupt signals
+		"--rm", // cleanup afterwards
+		"-v", kernelFolder+":/root/armhf",
+		"ghcr.io/oliverpool/crossbuild-armhf:impish-20220316",
+	)
+	// change the owner of the files inside docker to the current user
+	chown := func(folder string) error {
+		user, err := user.Current()
+		if err != nil {
+			return err
+		}
+		return dockerRun("chown", "-R", user.Uid+":"+user.Gid, folder)
+	}
+
+	// default raspberry pi config according to https://www.raspberrypi.com/documentation/computers/linux_kernel.html#cross-compiling-the-kernel
+	if err := dockerRun("make", "bcmrpi_defconfig"); err != nil {
+		return err
+	}
+	if err := chown(".config"); err != nil {
+		return err
+	}
+
+	// adjust config to add CONFIG_SQUASHFS
+	configPath := filepath.Join(kernelFolder, ".config")
+	err = adjustTextFile(configPath, func(line string) bool {
+		return strings.HasPrefix(line, "CONFIG_SQUASHFS=")
+	}, []string{
+		"CONFIG_SQUASHFS=y",
+	})
+	if err != nil {
+		return err
+	}
+
+	// compile kernel and dtbs
+	if err := dockerRun("make", "zImage", "dtbs", "-j"+strconv.Itoa(runtime.NumCPU())); err != nil {
+		return err
+	}
+	if err := chown("arch/arm/boot"); err != nil {
+		return err
+	}
+
+	bootFolder := filepath.Join(kernelFolder, "arch", "arm", "boot")
+	dstFolder := filepath.Join(".", "dist")
+	os.RemoveAll(dstFolder) // ignore any error
+	if err = os.MkdirAll(dstFolder, 0755); err != nil {
+		return err
+	}
+
+	// copy and rename kernel
+	if err = sh.Copy(filepath.Join(dstFolder, "vmlinuz"), filepath.Join(bootFolder, "zImage")); err != nil {
+		return err
+	}
+
+	// copy dtb files
+	files, err := filepath.Glob(filepath.Join(bootFolder, "dts", "bcm*-rpi-*.dtb"))
+	if err != nil {
+		return err
+	}
+	// copy config and cmdline files
+	files = append(files, "./gokrazy/cmdline.txt", "./gokrazy/config.txt")
+	for _, file := range files {
+		dtbName := filepath.Base(file)
+		if err = sh.Copy(filepath.Join(dstFolder, dtbName), file); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func adjustTextFile(path string, skipLine func(string) bool, appendLines []string) error {
+	b, stat, err := readFile(path) // read the whole file in memory, since we are going to overwrite it
+	if err != nil {
+		return err
+	}
+
+	dst, err := os.OpenFile(path, os.O_TRUNC|os.O_WRONLY, stat.Mode())
+	if err != nil {
+		return err
+	}
+	defer dst.Close()
+	w := bufio.NewWriter(dst)
+
+	for _, line := range strings.Split(string(b), "\n") {
+		if skipLine(line) {
+			continue
+		}
+		_, err = w.WriteString(line + "\n")
+		if err != nil {
+			return err
+		}
+	}
+	for _, line := range appendLines {
+		_, err = w.WriteString(line + "\n")
+		if err != nil {
+			return err
+		}
+	}
+	err = w.Flush()
+	if err != nil {
+		return err
+	}
+	return dst.Close()
+}
+
+func readFile(path string) ([]byte, fs.FileInfo, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, nil, err
+	}
+	defer f.Close()
+	b, err := io.ReadAll(f)
+	if err != nil {
+		return b, nil, err
+	}
+
+	stats, err := f.Stat()
+	return b, stats, err
+}

go.mod

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+module github.com/oliverpool/kernel-rpi-os-32
+
+go 1.18
+
+require github.com/magefile/mage v1.13.0

go.sum

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+github.com/magefile/mage v1.13.0 h1:XtLJl8bcCM7EFoO8FyH8XK3t7G5hQAeK+i4tq+veT9M=
+github.com/magefile/mage v1.13.0/go.mod h1:z5UZb/iS3GoOSn0JgWuiw7dxlurVYTu+/jHXqQg881A=

gokrazy/cmdline.txt

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+root=/dev/mmcblk0p2 init=/gokrazy/init rootwait panic=10 oops=panic

gokrazy/config.txt

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+# See https://www.raspberrypi.com/documentation/computers/config_txt.html
+
+enable_uart=0
+
+kernel=vmlinuz
+
+disable_splash=1