core/tools/ktestinit/main.go

// Copyright 2020 The Monogon Project Authors.
//
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// ktestinit is an init designed to run inside a lightweight VM for running tests in there.
// It performs basic platform initialization like mounting kernel filesystems and launches the
// test executable at /tester, passes the exit code back out over the control socket to ktest and
// then terminates the VM kernel.
package main

import (
	"errors"
	"fmt"
	"os"
	"os/exec"

	"golang.org/x/sys/unix"
)

func mountInit() error {
	for _, el := range []struct {
		dir   string
		fs    string
		flags uintptr
	}{
		{"/sys", "sysfs", unix.MS_NOEXEC | unix.MS_NOSUID | unix.MS_NODEV},
		{"/proc", "proc", unix.MS_NOEXEC | unix.MS_NOSUID | unix.MS_NODEV},
		{"/dev", "devtmpfs", unix.MS_NOEXEC | unix.MS_NOSUID},
		{"/dev/pts", "devpts", unix.MS_NOEXEC | unix.MS_NOSUID},
	} {
		if err := os.Mkdir(el.dir, 0755); err != nil && !os.IsExist(err) {
			return fmt.Errorf("could not make %s: %w", el.dir, err)
		}
		if err := unix.Mount(el.fs, el.dir, el.fs, el.flags, ""); err != nil {
			return fmt.Errorf("could not mount %s on %s: %w", el.fs, el.dir, err)
		}
	}
	return nil
}

func main() {
	if err := mountInit(); err != nil {
		panic(err)
	}

	// First virtual serial is always stdout, second is control
	ioConn, err := os.OpenFile("/dev/vport1p1", os.O_RDWR, 0)
	if err != nil {
		fmt.Printf("Failed to open communication device: %v\n", err)
		return
	}
	cmd := exec.Command("/tester", "-test.v")
	cmd.Stderr = os.Stderr
	cmd.Stdout = os.Stdout
	cmd.Env = append(cmd.Env, "IN_KTEST=true")
	if err := cmd.Run(); err != nil {
		var exerr *exec.ExitError
		if errors.As(err, &exerr) {
			if _, err := ioConn.Write([]byte{uint8(exerr.ExitCode())}); err != nil {
				panic(err)
			}
		} else if err != nil {
			fmt.Printf("Failed to execute tests (tests didn't run): %v", err)
		}
	}

	unix.Reboot(unix.LINUX_REBOOT_CMD_RESTART)
}