/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2022  Free Software Foundation, Inc.
 *
 *  GRUB is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  GRUB is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <grub/loader.h>
#include <grub/dl.h>
#include <grub/command.h>
#include <grub/time.h>

#include <grub/emu/exec.h>
#include <grub/emu/hostfile.h>
#include <grub/emu/misc.h>

GRUB_MOD_LICENSE ("GPLv3+");

static grub_dl_t my_mod;

static char *kernel_path;
static char *initrd_path;
static char *boot_cmdline;

static grub_err_t
grub_linux_boot (void)
{
  grub_err_t rc = GRUB_ERR_NONE;
  char *initrd_param;
  const char *kexec[] = {"kexec", "-la", kernel_path, boot_cmdline, NULL, NULL};
  const char *systemctl[] = {"systemctl", "kexec", NULL};
  int kexecute = grub_util_get_kexecute ();

  if (initrd_path)
    {
      initrd_param = grub_xasprintf ("--initrd=%s", initrd_path);
      kexec[3] = initrd_param;
      kexec[4] = boot_cmdline;
    }
  else
    initrd_param = grub_xasprintf ("%s", "");

  grub_dprintf ("linux", "%serforming 'kexec -la %s %s %s'\n",
                (kexecute) ? "P" : "Not p",
                kernel_path, initrd_param, boot_cmdline);

  if (kexecute)
    rc = grub_util_exec (kexec);

  grub_free (initrd_param);

  if (rc != GRUB_ERR_NONE)
    {
      grub_error (rc, N_("error trying to perform kexec load operation"));
      grub_sleep (3);
      return rc;
    }

  if (kexecute < 1)
    grub_fatal (N_("use '"PACKAGE"-emu --kexec' to force a system restart"));

  grub_dprintf ("linux", "Performing 'systemctl kexec' (%s) ",
		(kexecute==1) ? "do-or-die" : "just-in-case");
  rc = grub_util_exec (systemctl);

  /* `systemctl kexec` is "asynchronous" and will return even on success. */
  if (rc == 0)
    grub_sleep (10);

  if (kexecute == 1)
    grub_fatal (N_("error trying to perform 'systemctl kexec': %d"), rc);

  /*
   * WARNING: forcible reset should only be used in read-only environments.
   * grub-emu cannot check for these - users beware.
   */
  grub_dprintf ("linux", "Performing 'kexec -ex'");
  kexec[1] = "-ex";
  kexec[2] = NULL;
  rc = grub_util_exec (kexec);
  if (rc != GRUB_ERR_NONE)
    grub_fatal (N_("error trying to directly perform 'kexec -ex': %d"), rc);

  return rc;
}

static grub_err_t
grub_linux_unload (void)
{
  /* Unloading: we're no longer in use. */
  grub_dl_unref (my_mod);
  grub_free (boot_cmdline);
  boot_cmdline = NULL;
  return GRUB_ERR_NONE;
}

static grub_err_t
grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)), int argc,
		char *argv[])
{
  int i;
  char *tempstr;

  /* Mark ourselves as in-use. */
  grub_dl_ref (my_mod);

  if (argc == 0)
    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));

  if (!grub_util_is_regular (argv[0]))
    return grub_error (GRUB_ERR_FILE_NOT_FOUND,
		       N_("cannot find kernel file %s"), argv[0]);

  grub_free (kernel_path);
  kernel_path = grub_xasprintf ("%s", argv[0]);

  grub_free (boot_cmdline);
  boot_cmdline = NULL;

  if (argc > 1)
    {
      boot_cmdline = grub_xasprintf ("--command-line=%s", argv[1]);
      for (i = 2; i < argc; i++)
        {
          tempstr = grub_xasprintf ("%s %s", boot_cmdline, argv[i]);
          grub_free (boot_cmdline);
          boot_cmdline = tempstr;
        }
    }

  grub_loader_set (grub_linux_boot, grub_linux_unload, 0);

  return GRUB_ERR_NONE;
}

static grub_err_t
grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)), int argc,
		 char *argv[])
{
  if (argc == 0)
    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));

  if (!grub_util_is_regular (argv[0]))
    return grub_error (GRUB_ERR_FILE_NOT_FOUND,
		       N_("Cannot find initrd file %s"), argv[0]);

  grub_free (initrd_path);
  initrd_path = grub_xasprintf ("%s", argv[0]);

  /* We are done - mark ourselves as on longer in use. */
  grub_dl_unref (my_mod);

  return GRUB_ERR_NONE;
}

static grub_command_t cmd_linux, cmd_initrd;

GRUB_MOD_INIT (linux)
{
  cmd_linux = grub_register_command ("linux", grub_cmd_linux, 0,
				     N_("Load Linux."));
  cmd_initrd = grub_register_command ("initrd", grub_cmd_initrd, 0,
				      N_("Load initrd."));
  my_mod = mod;
}

GRUB_MOD_FINI (linux)
{
  grub_unregister_command (cmd_linux);
  grub_unregister_command (cmd_initrd);
}