package main

import (
	"log"
	"os"
	"runtime"
	. "syscall"
)

func main() {
	runtime.LockOSThread()
	log.SetFlags(0)
	log.SetPrefix("earlyinit: ")

	if err := Mount(
		"devtmpfs",
		"/dev/",
		"devtmpfs",
		MS_NOSUID|MS_NOEXEC,
		"",
	); err != nil {
		log.Fatalf("cannot mount devtmpfs: %v", err)
	}

	// The kernel might be unable to set up the console. When that happens,
	// printk is called with "Warning: unable to open an initial console."
	// and the init runs with no files. The checkfds runtime function
	// populates 0-2 by opening /dev/null for them.
	//
	// This check replaces 1 and 2 with /dev/kmsg to improve the chance
	// of output being visible to the user.
	if fi, err := os.Stdout.Stat(); err == nil {
		if stat, ok := fi.Sys().(*Stat_t); ok {
			if stat.Rdev == 0x103 {
				var fd int
				if fd, err = Open(
					"/dev/kmsg",
					O_WRONLY|O_CLOEXEC,
					0,
				); err != nil {
					log.Fatalf("cannot open kmsg: %v", err)
				}

				if err = Dup3(fd, Stdout, 0); err != nil {
					log.Fatalf("cannot open stdout: %v", err)
				}
				if err = Dup3(fd, Stderr, 0); err != nil {
					log.Fatalf("cannot open stderr: %v", err)
				}

				if err = Close(fd); err != nil {
					log.Printf("cannot close kmsg: %v", err)
				}
			}
		}
	}

}