/*-
 * Copyright (c) 2022, Netflix, Inc.
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

/*
 * Mini-init(8) so we can run as init/pid 1 in a LinuxBoot environment.
 */

#include "stand.h"
#include "host_syscall.h"
#include "kboot.h"

/*
 * Create a 'standard' early boot environment. Cribbed from the things that
 * sysvinit, u-root, and initramfs-tools do. This is a minimal environment
 * for modern Linux systems, though the /tmp, /run and /var stuff can likely
 * be done inside the initrd image itself (as can creating the mount points
 * for /proc, /dev and /sys).
 *
 * Note: We ignore errors here. There's no stderr to report them to yet. These
 * operations generally can't fail, but if they do, we may not have the ability
 * to report them later.
 */
static void
init_fs_env(void)
{
        /*
         * Create directories for mandatory filesystems and mount them.
         */
        host_mkdir("/proc", 0555);
        host_mount("proc", "/proc", "proc", MS_RELATIME, "");
        host_mkdir("/sys", 0555);
        host_mount("sysfs", "/sys", "sysfs", MS_RELATIME, "");
        host_mkdir("/dev", 0755);
        host_mount("devtmpfs", "/dev", "devtmpfs", MS_RELATIME,
            "mode=0755,nr_inodes=0");

        /*
         * Create compat links: /dev/fd lives in /proc, and needs some help to
         * get setup.
         */
        host_symlink("/proc/self/fd", "/dev/fd");
        host_symlink("fd/0", "/dev/stdin");
        host_symlink("fd/1", "/dev/stdout");
        host_symlink("fd/2", "/dev/stderr");


        /*
         * Unsure if we need this, but create a sane /tmp just in case that's useful.
         * and point /run over to it.
         */
        host_mkdir("/tmp", 01777);
        host_mount("tmpfs", "/tmp", "tmpfs", MS_RELATIME, "size=10%,mode=1777");
        host_symlink("/tmp", "/run");

        /*
         * Unsure the loader needs /var and /var/log, but they are easy to
         * create.
         */
        host_mkdir("/var", 0555);
        host_mkdir("/var/lock", 0555);
        host_symlink("/tmp", "/var/tmp");
}

static void
init_tty(void)
{
        int fd;

        /*
         * sysvinit asks the linux kernel to convert the CTRL-ALT-DEL to a SIGINT,
         * but we skip that.
         */

        /*
         * Setup /dev/console as stdin/out/err
         */
        host_close(0);
        host_close(1);
        host_close(2);
        fd = host_open("/dev/console", HOST_O_RDWR | HOST_O_NOCTTY, 0);
        host_dup(fd);
        host_dup(fd);
#if 0
        /*
         * I think we may need to put it in 'raw' mode, but maybe not. Linux
         * sysvinit sets it into 'sane' mode with several tweaks. Not enabled at
         * the moment since host console initialization seems sufficient.
         */
        struct host_termios tty;

        host_cfmakeraw(&tty);
        host_tcsetattr(fd, HOST_TCANOW, &tty);
        host_tcflush(fd, HOST_TCIOFLUSH)
#endif
}

static void
init_sig(void)
{
        /*
         * since we're running as init, we need to catch some signals
         */

        /*
         * setup signals here
         *
         * sysvinit catches a lot of signals, but the boot loader needn't catch
         * so many since we don't do as much as it does. If we need to, put the
         * signal catching / ignoring code here. If we implement a 'shell'
         * function to spawn a sub-shell, we'll likely need to do a lot more.
         */
}

void
do_init(void)
{
        /*
         * Only pid 1 is init
         */
        if (host_getpid() != 1)
                return;

        init_fs_env();
        init_tty();
        init_sig();
}