/*
   *  linux/kernel/reboot.c
   *
   *  Copyright (C) 2013  Linus Torvalds
   */

  #define pr_fmt(fmt)	"reboot: " fmt

  #include <linux/ctype.h>

  #include <linux/export.h>
  #include <linux/kexec.h>
  #include <linux/kmod.h>
  #include <linux/kmsg_dump.h>
  #include <linux/reboot.h>
  #include <linux/suspend.h>
  #include <linux/syscalls.h>
  #include <linux/syscore_ops.h>
  #include <linux/uaccess.h>
  
  /*
   * this indicates whether you can reboot with ctrl-alt-del: the default is yes
   */
  
  int C_A_D = 1;
  struct pid *cad_pid;
  EXPORT_SYMBOL(cad_pid);

  #if defined(CONFIG_ARM) || defined(CONFIG_UNICORE32)
  #define DEFAULT_REBOOT_MODE		= REBOOT_HARD
  #else
  #define DEFAULT_REBOOT_MODE
  #endif
  enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
  
  int reboot_default;
  int reboot_cpu;
  enum reboot_type reboot_type = BOOT_ACPI;
  int reboot_force;

  /*
   * If set, this is used for preparing the system to power off.
   */
  
  void (*pm_power_off_prepare)(void);
  
  /**
   *	emergency_restart - reboot the system
   *
   *	Without shutting down any hardware or taking any locks
   *	reboot the system.  This is called when we know we are in
   *	trouble so this is our best effort to reboot.  This is
   *	safe to call in interrupt context.
   */
  void emergency_restart(void)
  {
  	kmsg_dump(KMSG_DUMP_EMERG);
  	machine_emergency_restart();
  }
  EXPORT_SYMBOL_GPL(emergency_restart);
  
  void kernel_restart_prepare(char *cmd)
  {
  	blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
  	system_state = SYSTEM_RESTART;
  	usermodehelper_disable();
  	device_shutdown();
  }
  
  /**
   *	register_reboot_notifier - Register function to be called at reboot time
   *	@nb: Info about notifier function to be called
   *
   *	Registers a function with the list of functions
   *	to be called at reboot time.
   *
   *	Currently always returns zero, as blocking_notifier_chain_register()
   *	always returns zero.
   */
  int register_reboot_notifier(struct notifier_block *nb)
  {
  	return blocking_notifier_chain_register(&reboot_notifier_list, nb);
  }
  EXPORT_SYMBOL(register_reboot_notifier);
  
  /**
   *	unregister_reboot_notifier - Unregister previously registered reboot notifier
   *	@nb: Hook to be unregistered
   *
   *	Unregisters a previously registered reboot
   *	notifier function.
   *
   *	Returns zero on success, or %-ENOENT on failure.
   */
  int unregister_reboot_notifier(struct notifier_block *nb)
  {
  	return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
  }
  EXPORT_SYMBOL(unregister_reboot_notifier);
  
  static void migrate_to_reboot_cpu(void)
  {
  	/* The boot cpu is always logical cpu 0 */

  	int cpu = reboot_cpu;

  
  	cpu_hotplug_disable();
  
  	/* Make certain the cpu I'm about to reboot on is online */
  	if (!cpu_online(cpu))
  		cpu = cpumask_first(cpu_online_mask);
  
  	/* Prevent races with other tasks migrating this task */
  	current->flags |= PF_NO_SETAFFINITY;
  
  	/* Make certain I only run on the appropriate processor */
  	set_cpus_allowed_ptr(current, cpumask_of(cpu));
  }
  
  /**
   *	kernel_restart - reboot the system
   *	@cmd: pointer to buffer containing command to execute for restart
   *		or %NULL
   *
   *	Shutdown everything and perform a clean reboot.
   *	This is not safe to call in interrupt context.
   */
  void kernel_restart(char *cmd)
  {
  	kernel_restart_prepare(cmd);
  	migrate_to_reboot_cpu();
  	syscore_shutdown();
  	if (!cmd)

  		pr_emerg("Restarting system
  ");

  	else

  		pr_emerg("Restarting system with command '%s'
  ", cmd);

  	kmsg_dump(KMSG_DUMP_RESTART);
  	machine_restart(cmd);
  }
  EXPORT_SYMBOL_GPL(kernel_restart);
  
  static void kernel_shutdown_prepare(enum system_states state)
  {
  	blocking_notifier_call_chain(&reboot_notifier_list,

  		(state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);

  	system_state = state;
  	usermodehelper_disable();
  	device_shutdown();
  }
  /**
   *	kernel_halt - halt the system
   *
   *	Shutdown everything and perform a clean system halt.
   */
  void kernel_halt(void)
  {
  	kernel_shutdown_prepare(SYSTEM_HALT);
  	migrate_to_reboot_cpu();
  	syscore_shutdown();

  	pr_emerg("System halted
  ");

  	kmsg_dump(KMSG_DUMP_HALT);
  	machine_halt();
  }

  EXPORT_SYMBOL_GPL(kernel_halt);
  
  /**
   *	kernel_power_off - power_off the system
   *
   *	Shutdown everything and perform a clean system power_off.
   */
  void kernel_power_off(void)
  {
  	kernel_shutdown_prepare(SYSTEM_POWER_OFF);
  	if (pm_power_off_prepare)
  		pm_power_off_prepare();
  	migrate_to_reboot_cpu();
  	syscore_shutdown();

  	pr_emerg("Power down
  ");

  	kmsg_dump(KMSG_DUMP_POWEROFF);
  	machine_power_off();
  }
  EXPORT_SYMBOL_GPL(kernel_power_off);
  
  static DEFINE_MUTEX(reboot_mutex);
  
  /*
   * Reboot system call: for obvious reasons only root may call it,
   * and even root needs to set up some magic numbers in the registers
   * so that some mistake won't make this reboot the whole machine.
   * You can also set the meaning of the ctrl-alt-del-key here.
   *
   * reboot doesn't sync: do that yourself before calling this.
   */
  SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
  		void __user *, arg)
  {
  	struct pid_namespace *pid_ns = task_active_pid_ns(current);
  	char buffer[256];
  	int ret = 0;
  
  	/* We only trust the superuser with rebooting the system. */
  	if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
  		return -EPERM;
  
  	/* For safety, we require "magic" arguments. */
  	if (magic1 != LINUX_REBOOT_MAGIC1 ||

  			(magic2 != LINUX_REBOOT_MAGIC2 &&
  			magic2 != LINUX_REBOOT_MAGIC2A &&

  			magic2 != LINUX_REBOOT_MAGIC2B &&

  			magic2 != LINUX_REBOOT_MAGIC2C))

  		return -EINVAL;
  
  	/*
  	 * If pid namespaces are enabled and the current task is in a child
  	 * pid_namespace, the command is handled by reboot_pid_ns() which will
  	 * call do_exit().
  	 */
  	ret = reboot_pid_ns(pid_ns, cmd);
  	if (ret)
  		return ret;
  
  	/* Instead of trying to make the power_off code look like
  	 * halt when pm_power_off is not set do it the easy way.
  	 */
  	if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
  		cmd = LINUX_REBOOT_CMD_HALT;
  
  	mutex_lock(&reboot_mutex);
  	switch (cmd) {
  	case LINUX_REBOOT_CMD_RESTART:
  		kernel_restart(NULL);
  		break;
  
  	case LINUX_REBOOT_CMD_CAD_ON:
  		C_A_D = 1;
  		break;
  
  	case LINUX_REBOOT_CMD_CAD_OFF:
  		C_A_D = 0;
  		break;
  
  	case LINUX_REBOOT_CMD_HALT:
  		kernel_halt();
  		do_exit(0);
  		panic("cannot halt");
  
  	case LINUX_REBOOT_CMD_POWER_OFF:
  		kernel_power_off();
  		do_exit(0);
  		break;
  
  	case LINUX_REBOOT_CMD_RESTART2:

  		ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
  		if (ret < 0) {

  			ret = -EFAULT;
  			break;
  		}
  		buffer[sizeof(buffer) - 1] = '\0';
  
  		kernel_restart(buffer);
  		break;
  
  #ifdef CONFIG_KEXEC
  	case LINUX_REBOOT_CMD_KEXEC:
  		ret = kernel_kexec();
  		break;
  #endif
  
  #ifdef CONFIG_HIBERNATION
  	case LINUX_REBOOT_CMD_SW_SUSPEND:
  		ret = hibernate();
  		break;
  #endif
  
  	default:
  		ret = -EINVAL;
  		break;
  	}
  	mutex_unlock(&reboot_mutex);
  	return ret;
  }
  
  static void deferred_cad(struct work_struct *dummy)
  {
  	kernel_restart(NULL);
  }
  
  /*
   * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
   * As it's called within an interrupt, it may NOT sync: the only choice
   * is whether to reboot at once, or just ignore the ctrl-alt-del.
   */
  void ctrl_alt_del(void)
  {
  	static DECLARE_WORK(cad_work, deferred_cad);
  
  	if (C_A_D)
  		schedule_work(&cad_work);
  	else
  		kill_cad_pid(SIGINT, 1);
  }
  
  char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
  
  static int __orderly_poweroff(bool force)
  {
  	char **argv;
  	static char *envp[] = {
  		"HOME=/",
  		"PATH=/sbin:/bin:/usr/sbin:/usr/bin",
  		NULL
  	};
  	int ret;
  
  	argv = argv_split(GFP_KERNEL, poweroff_cmd, NULL);
  	if (argv) {
  		ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
  		argv_free(argv);
  	} else {

  		ret = -ENOMEM;
  	}
  
  	if (ret && force) {

  		pr_warn("Failed to start orderly shutdown: forcing the issue
  ");

  		/*
  		 * I guess this should try to kick off some daemon to sync and
  		 * poweroff asap.  Or not even bother syncing if we're doing an
  		 * emergency shutdown?
  		 */
  		emergency_sync();
  		kernel_power_off();
  	}
  
  	return ret;
  }
  
  static bool poweroff_force;
  
  static void poweroff_work_func(struct work_struct *work)
  {
  	__orderly_poweroff(poweroff_force);
  }
  
  static DECLARE_WORK(poweroff_work, poweroff_work_func);
  
  /**
   * orderly_poweroff - Trigger an orderly system poweroff
   * @force: force poweroff if command execution fails
   *
   * This may be called from any context to trigger a system shutdown.
   * If the orderly shutdown fails, it will force an immediate shutdown.
   */
  int orderly_poweroff(bool force)
  {
  	if (force) /* do not override the pending "true" */
  		poweroff_force = true;
  	schedule_work(&poweroff_work);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(orderly_poweroff);

  
  static int __init reboot_setup(char *str)
  {
  	for (;;) {
  		/*
  		 * Having anything passed on the command line via
  		 * reboot= will cause us to disable DMI checking
  		 * below.
  		 */
  		reboot_default = 0;
  
  		switch (*str) {
  		case 'w':
  			reboot_mode = REBOOT_WARM;
  			break;
  
  		case 'c':
  			reboot_mode = REBOOT_COLD;
  			break;
  
  		case 'h':
  			reboot_mode = REBOOT_HARD;
  			break;
  
  		case 's':
  			if (isdigit(*(str+1)))
  				reboot_cpu = simple_strtoul(str+1, NULL, 0);
  			else if (str[1] == 'm' && str[2] == 'p' &&
  							isdigit(*(str+3)))
  				reboot_cpu = simple_strtoul(str+3, NULL, 0);
  			else
  				reboot_mode = REBOOT_SOFT;
  			break;
  
  		case 'g':
  			reboot_mode = REBOOT_GPIO;
  			break;
  
  		case 'b':
  		case 'a':
  		case 'k':
  		case 't':
  		case 'e':
  		case 'p':
  			reboot_type = *str;
  			break;
  
  		case 'f':
  			reboot_force = 1;
  			break;
  		}
  
  		str = strchr(str, ',');
  		if (str)
  			str++;
  		else
  			break;
  	}
  	return 1;
  }
  __setup("reboot=", reboot_setup);