[mirror_ubuntu-artful-kernel.git] / kernel / reboot.c

/*
 *  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;

/*
 * This variable is used privately to keep track of whether or not
 * reboot_type is still set to its default value (i.e., reboot= hasn't
 * been set on the command line).  This is needed so that we can
 * suppress DMI scanning for reboot quirks.  Without it, it's
 * impossible to override a faulty reboot quirk without recompiling.
 */
int reboot_default = 1;
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);

/*
 *	Notifier list for kernel code which wants to be called
 *	to restart the system.
 */
static ATOMIC_NOTIFIER_HEAD(restart_handler_list);

/**
 *	register_restart_handler - Register function to be called to reset
 *				   the system
 *	@nb: Info about handler function to be called
 *	@nb->priority:	Handler priority. Handlers should follow the
 *			following guidelines for setting priorities.
 *			0:	Restart handler of last resort,
 *				with limited restart capabilities
 *			128:	Default restart handler; use if no other
 *				restart handler is expected to be available,
 *				and/or if restart functionality is
 *				sufficient to restart the entire system
 *			255:	Highest priority restart handler, will
 *				preempt all other restart handlers
 *
 *	Registers a function with code to be called to restart the
 *	system.
 *
 *	Registered functions will be called from machine_restart as last
 *	step of the restart sequence (if the architecture specific
 *	machine_restart function calls do_kernel_restart - see below
 *	for details).
 *	Registered functions are expected to restart the system immediately.
 *	If more than one function is registered, the restart handler priority
 *	selects which function will be called first.
 *
 *	Restart handlers are expected to be registered from non-architecture
 *	code, typically from drivers. A typical use case would be a system
 *	where restart functionality is provided through a watchdog. Multiple
 *	restart handlers may exist; for example, one restart handler might
 *	restart the entire system, while another only restarts the CPU.
 *	In such cases, the restart handler which only restarts part of the
 *	hardware is expected to register with low priority to ensure that
 *	it only runs if no other means to restart the system is available.
 *
 *	Currently always returns zero, as atomic_notifier_chain_register()
 *	always returns zero.
 */
int register_restart_handler(struct notifier_block *nb)
{
	return atomic_notifier_chain_register(&restart_handler_list, nb);
}
EXPORT_SYMBOL(register_restart_handler);

/**
 *	unregister_restart_handler - Unregister previously registered
 *				     restart handler
 *	@nb: Hook to be unregistered
 *
 *	Unregisters a previously registered restart handler function.
 *
 *	Returns zero on success, or %-ENOENT on failure.
 */
int unregister_restart_handler(struct notifier_block *nb)
{
	return atomic_notifier_chain_unregister(&restart_handler_list, nb);
}
EXPORT_SYMBOL(unregister_restart_handler);

/**
 *	do_kernel_restart - Execute kernel restart handler call chain
 *
 *	Calls functions registered with register_restart_handler.
 *
 *	Expected to be called from machine_restart as last step of the restart
 *	sequence.
 *
 *	Restarts the system immediately if a restart handler function has been
 *	registered. Otherwise does nothing.
 */
void do_kernel_restart(char *cmd)
{
	atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
}

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\n");
	else
		pr_emerg("Restarting system with command '%s'\n", 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\n");
	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\n");
	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_CORE
	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 const char reboot_cmd[] = "/sbin/reboot";

static int run_cmd(const char *cmd)
{
	char **argv;
	static char *envp[] = {
		"HOME=/",
		"PATH=/sbin:/bin:/usr/sbin:/usr/bin",
		NULL
	};
	int ret;
	argv = argv_split(GFP_KERNEL, cmd, NULL);
	if (argv) {
		ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
		argv_free(argv);
	} else {
		ret = -ENOMEM;
	}

	return ret;
}

static int __orderly_reboot(void)
{
	int ret;

	ret = run_cmd(reboot_cmd);

	if (ret) {
		pr_warn("Failed to start orderly reboot: forcing the issue\n");
		emergency_sync();
		kernel_restart(NULL);
	}

	return ret;
}

static int __orderly_poweroff(bool force)
{
	int ret;

	ret = run_cmd(poweroff_cmd);

	if (ret && force) {
		pr_warn("Failed to start orderly shutdown: forcing the issue\n");

		/*
		 * 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.
 */
void orderly_poweroff(bool force)
{
	if (force) /* do not override the pending "true" */
		poweroff_force = true;
	schedule_work(&poweroff_work);
}
EXPORT_SYMBOL_GPL(orderly_poweroff);

static void reboot_work_func(struct work_struct *work)
{
	__orderly_reboot();
}

static DECLARE_WORK(reboot_work, reboot_work_func);

/**
 * orderly_reboot - Trigger an orderly system reboot
 *
 * This may be called from any context to trigger a system reboot.
 * If the orderly reboot fails, it will force an immediate reboot.
 */
void orderly_reboot(void)
{
	schedule_work(&reboot_work);
}
EXPORT_SYMBOL_GPL(orderly_reboot);

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':
		{
			int rc;

			if (isdigit(*(str+1))) {
				rc = kstrtoint(str+1, 0, &reboot_cpu);
				if (rc)
					return rc;
			} else if (str[1] == 'm' && str[2] == 'p' &&
				   isdigit(*(str+3))) {
				rc = kstrtoint(str+3, 0, &reboot_cpu);
				if (rc)
					return rc;
			} 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);
Commit	Line	Data
15d94b82 RH	1	/*
	2	* linux/kernel/reboot.c
	3	*
	4	* Copyright (C) 2013 Linus Torvalds
	5	*/
	6
972ee83d RH	7	#define pr_fmt(fmt) "reboot: " fmt
972ee83d RH	8
1b3a5d02	9	#include <linux/ctype.h>
15d94b82 RH	10	#include <linux/export.h>
	11	#include <linux/kexec.h>
	12	#include <linux/kmod.h>
	13	#include <linux/kmsg_dump.h>
	14	#include <linux/reboot.h>
	15	#include <linux/suspend.h>
	16	#include <linux/syscalls.h>
	17	#include <linux/syscore_ops.h>
	18	#include <linux/uaccess.h>
	19
	20	/*
	21	* this indicates whether you can reboot with ctrl-alt-del: the default is yes
	22	*/
	23
	24	int C_A_D = 1;
	25	struct pid *cad_pid;
	26	EXPORT_SYMBOL(cad_pid);
	27
1b3a5d02 RH	28	#if defined(CONFIG_ARM) \|\| defined(CONFIG_UNICORE32)
	29	#define DEFAULT_REBOOT_MODE = REBOOT_HARD
	30	#else
	31	#define DEFAULT_REBOOT_MODE
	32	#endif
	33	enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
	34
e2f0b88e CL	35	/*
	36	* This variable is used privately to keep track of whether or not
	37	* reboot_type is still set to its default value (i.e., reboot= hasn't
	38	* been set on the command line). This is needed so that we can
	39	* suppress DMI scanning for reboot quirks. Without it, it's
	40	* impossible to override a faulty reboot quirk without recompiling.
	41	*/
	42	int reboot_default = 1;
1b3a5d02 RH	43	int reboot_cpu;
	44	enum reboot_type reboot_type = BOOT_ACPI;
	45	int reboot_force;
	46
15d94b82 RH	47	/*
	48	* If set, this is used for preparing the system to power off.
	49	*/
	50
	51	void (*pm_power_off_prepare)(void);
	52
	53	/**
	54	* emergency_restart - reboot the system
	55	*
	56	* Without shutting down any hardware or taking any locks
	57	* reboot the system. This is called when we know we are in
	58	* trouble so this is our best effort to reboot. This is
	59	* safe to call in interrupt context.
	60	*/
	61	void emergency_restart(void)
	62	{
	63	kmsg_dump(KMSG_DUMP_EMERG);
	64	machine_emergency_restart();
	65	}
	66	EXPORT_SYMBOL_GPL(emergency_restart);
	67
	68	void kernel_restart_prepare(char *cmd)
	69	{
	70	blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
	71	system_state = SYSTEM_RESTART;
	72	usermodehelper_disable();
	73	device_shutdown();
	74	}
	75
	76	/**
	77	* register_reboot_notifier - Register function to be called at reboot time
	78	* @nb: Info about notifier function to be called
	79	*
	80	* Registers a function with the list of functions
	81	* to be called at reboot time.
	82	*
	83	* Currently always returns zero, as blocking_notifier_chain_register()
	84	* always returns zero.
	85	*/
	86	int register_reboot_notifier(struct notifier_block *nb)
	87	{
	88	return blocking_notifier_chain_register(&reboot_notifier_list, nb);
	89	}
	90	EXPORT_SYMBOL(register_reboot_notifier);
	91
	92	/**
	93	* unregister_reboot_notifier - Unregister previously registered reboot notifier
	94	* @nb: Hook to be unregistered
	95	*
	96	* Unregisters a previously registered reboot
	97	* notifier function.
	98	*
	99	* Returns zero on success, or %-ENOENT on failure.
	100	*/
	101	int unregister_reboot_notifier(struct notifier_block *nb)
	102	{
	103	return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
	104	}
	105	EXPORT_SYMBOL(unregister_reboot_notifier);
	106
b63adb97 GR	107	/*
	108	* Notifier list for kernel code which wants to be called
	109	* to restart the system.
	110	*/
	111	static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
	112
	113	/**
	114	* register_restart_handler - Register function to be called to reset
	115	* the system
	116	* @nb: Info about handler function to be called
	117	* @nb->priority: Handler priority. Handlers should follow the
	118	* following guidelines for setting priorities.
	119	* 0: Restart handler of last resort,
	120	* with limited restart capabilities
	121	* 128: Default restart handler; use if no other
	122	* restart handler is expected to be available,
	123	* and/or if restart functionality is
	124	* sufficient to restart the entire system
	125	* 255: Highest priority restart handler, will
	126	* preempt all other restart handlers
	127	*
	128	* Registers a function with code to be called to restart the
	129	* system.
	130	*
	131	* Registered functions will be called from machine_restart as last
	132	* step of the restart sequence (if the architecture specific
	133	* machine_restart function calls do_kernel_restart - see below
	134	* for details).
	135	* Registered functions are expected to restart the system immediately.
	136	* If more than one function is registered, the restart handler priority
	137	* selects which function will be called first.
	138	*
	139	* Restart handlers are expected to be registered from non-architecture
	140	* code, typically from drivers. A typical use case would be a system
	141	* where restart functionality is provided through a watchdog. Multiple
	142	* restart handlers may exist; for example, one restart handler might
	143	* restart the entire system, while another only restarts the CPU.
	144	* In such cases, the restart handler which only restarts part of the
	145	* hardware is expected to register with low priority to ensure that
	146	* it only runs if no other means to restart the system is available.
	147	*
	148	* Currently always returns zero, as atomic_notifier_chain_register()
	149	* always returns zero.
	150	*/
	151	int register_restart_handler(struct notifier_block *nb)
	152	{
	153	return atomic_notifier_chain_register(&restart_handler_list, nb);
	154	}
	155	EXPORT_SYMBOL(register_restart_handler);
	156
	157	/**
	158	* unregister_restart_handler - Unregister previously registered
	159	* restart handler
	160	* @nb: Hook to be unregistered
	161	*
	162	* Unregisters a previously registered restart handler function.
	163	*
	164	* Returns zero on success, or %-ENOENT on failure.
	165	*/
	166	int unregister_restart_handler(struct notifier_block *nb)
	167	{
	168	return atomic_notifier_chain_unregister(&restart_handler_list, nb);
	169	}
	170	EXPORT_SYMBOL(unregister_restart_handler);
171
172	/**
173	* do_kernel_restart - Execute kernel restart handler call chain
174	*
175	* Calls functions registered with register_restart_handler.
176	*
177	* Expected to be called from machine_restart as last step of the restart
178	* sequence.
179	*
180	* Restarts the system immediately if a restart handler function has been
181	* registered. Otherwise does nothing.
182	*/
183	void do_kernel_restart(char *cmd)
184	{
185	atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
186	}
187
c97102ba	188	void migrate_to_reboot_cpu(void)
15d94b82 RH	189	{
15d94b82 RH	190	/* The boot cpu is always logical cpu 0 */
1b3a5d02	191	int cpu = reboot_cpu;
15d94b82 RH	192
	193	cpu_hotplug_disable();
	194
	195	/* Make certain the cpu I'm about to reboot on is online */
	196	if (!cpu_online(cpu))
	197	cpu = cpumask_first(cpu_online_mask);
	198
	199	/* Prevent races with other tasks migrating this task */
	200	current->flags \|= PF_NO_SETAFFINITY;
	201
	202	/* Make certain I only run on the appropriate processor */
	203	set_cpus_allowed_ptr(current, cpumask_of(cpu));
	204	}
	205
	206	/**
	207	* kernel_restart - reboot the system
	208	* @cmd: pointer to buffer containing command to execute for restart
	209	* or %NULL
	210	*
	211	* Shutdown everything and perform a clean reboot.
	212	* This is not safe to call in interrupt context.
	213	*/
	214	void kernel_restart(char *cmd)
	215	{
	216	kernel_restart_prepare(cmd);
	217	migrate_to_reboot_cpu();
	218	syscore_shutdown();
	219	if (!cmd)
972ee83d	220	pr_emerg("Restarting system\n");
15d94b82	221	else
972ee83d	222	pr_emerg("Restarting system with command '%s'\n", cmd);
15d94b82 RH	223	kmsg_dump(KMSG_DUMP_RESTART);
	224	machine_restart(cmd);
	225	}
	226	EXPORT_SYMBOL_GPL(kernel_restart);
	227
	228	static void kernel_shutdown_prepare(enum system_states state)
	229	{
	230	blocking_notifier_call_chain(&reboot_notifier_list,
972ee83d	231	(state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
15d94b82 RH	232	system_state = state;
	233	usermodehelper_disable();
	234	device_shutdown();
	235	}
	236	/**
	237	* kernel_halt - halt the system
	238	*
	239	* Shutdown everything and perform a clean system halt.
	240	*/
	241	void kernel_halt(void)
	242	{
	243	kernel_shutdown_prepare(SYSTEM_HALT);
	244	migrate_to_reboot_cpu();
	245	syscore_shutdown();
972ee83d	246	pr_emerg("System halted\n");
15d94b82 RH	247	kmsg_dump(KMSG_DUMP_HALT);
	248	machine_halt();
	249	}
15d94b82 RH	250	EXPORT_SYMBOL_GPL(kernel_halt);
	251
	252	/**
	253	* kernel_power_off - power_off the system
	254	*
	255	* Shutdown everything and perform a clean system power_off.
	256	*/
	257	void kernel_power_off(void)
	258	{
	259	kernel_shutdown_prepare(SYSTEM_POWER_OFF);
	260	if (pm_power_off_prepare)
	261	pm_power_off_prepare();
	262	migrate_to_reboot_cpu();
	263	syscore_shutdown();
972ee83d	264	pr_emerg("Power down\n");
15d94b82 RH	265	kmsg_dump(KMSG_DUMP_POWEROFF);
	266	machine_power_off();
	267	}
	268	EXPORT_SYMBOL_GPL(kernel_power_off);
	269
	270	static DEFINE_MUTEX(reboot_mutex);
	271
	272	/*
	273	* Reboot system call: for obvious reasons only root may call it,
	274	* and even root needs to set up some magic numbers in the registers
	275	* so that some mistake won't make this reboot the whole machine.
	276	* You can also set the meaning of the ctrl-alt-del-key here.
	277	*
	278	* reboot doesn't sync: do that yourself before calling this.
	279	*/
	280	SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
	281	void __user *, arg)
	282	{
	283	struct pid_namespace *pid_ns = task_active_pid_ns(current);
	284	char buffer[256];
	285	int ret = 0;
	286
	287	/* We only trust the superuser with rebooting the system. */
	288	if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
	289	return -EPERM;
	290
	291	/* For safety, we require "magic" arguments. */
	292	if (magic1 != LINUX_REBOOT_MAGIC1 \|\|
972ee83d RH	293	(magic2 != LINUX_REBOOT_MAGIC2 &&
972ee83d RH	294	magic2 != LINUX_REBOOT_MAGIC2A &&
15d94b82	295	magic2 != LINUX_REBOOT_MAGIC2B &&
972ee83d	296	magic2 != LINUX_REBOOT_MAGIC2C))
15d94b82 RH	297	return -EINVAL;
	298
	299	/*
	300	* If pid namespaces are enabled and the current task is in a child
	301	* pid_namespace, the command is handled by reboot_pid_ns() which will
	302	* call do_exit().
	303	*/
	304	ret = reboot_pid_ns(pid_ns, cmd);
	305	if (ret)
	306	return ret;
	307
	308	/* Instead of trying to make the power_off code look like
	309	* halt when pm_power_off is not set do it the easy way.
	310	*/
	311	if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
	312	cmd = LINUX_REBOOT_CMD_HALT;
	313
	314	mutex_lock(&reboot_mutex);
	315	switch (cmd) {
	316	case LINUX_REBOOT_CMD_RESTART:
	317	kernel_restart(NULL);
	318	break;
	319
	320	case LINUX_REBOOT_CMD_CAD_ON:
	321	C_A_D = 1;
	322	break;
	323
	324	case LINUX_REBOOT_CMD_CAD_OFF:
	325	C_A_D = 0;
	326	break;
	327
	328	case LINUX_REBOOT_CMD_HALT:
	329	kernel_halt();
	330	do_exit(0);
	331	panic("cannot halt");
	332
	333	case LINUX_REBOOT_CMD_POWER_OFF:
	334	kernel_power_off();
	335	do_exit(0);
	336	break;
	337
	338	case LINUX_REBOOT_CMD_RESTART2:
972ee83d RH	339	ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
972ee83d RH	340	if (ret < 0) {
15d94b82 RH	341	ret = -EFAULT;
	342	break;
	343	}
	344	buffer[sizeof(buffer) - 1] = '\0';
	345
	346	kernel_restart(buffer);
	347	break;
	348
2965faa5	349	#ifdef CONFIG_KEXEC_CORE
15d94b82 RH	350	case LINUX_REBOOT_CMD_KEXEC:
	351	ret = kernel_kexec();
	352	break;
	353	#endif
	354
	355	#ifdef CONFIG_HIBERNATION
	356	case LINUX_REBOOT_CMD_SW_SUSPEND:
	357	ret = hibernate();
	358	break;
	359	#endif
	360
	361	default:
	362	ret = -EINVAL;
	363	break;
	364	}
	365	mutex_unlock(&reboot_mutex);
	366	return ret;
	367	}
	368
	369	static void deferred_cad(struct work_struct *dummy)
	370	{
	371	kernel_restart(NULL);
	372	}
	373
	374	/*
	375	* This function gets called by ctrl-alt-del - ie the keyboard interrupt.
	376	* As it's called within an interrupt, it may NOT sync: the only choice
	377	* is whether to reboot at once, or just ignore the ctrl-alt-del.
	378	*/
	379	void ctrl_alt_del(void)
	380	{
	381	static DECLARE_WORK(cad_work, deferred_cad);
	382
	383	if (C_A_D)
	384	schedule_work(&cad_work);
	385	else
	386	kill_cad_pid(SIGINT, 1);
	387	}
	388
	389	char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
7a54f46b	390	static const char reboot_cmd[] = "/sbin/reboot";
15d94b82	391
7a54f46b	392	static int run_cmd(const char *cmd)
15d94b82 RH	393	{
	394	char **argv;
	395	static char *envp[] = {
	396	"HOME=/",
	397	"PATH=/sbin:/bin:/usr/sbin:/usr/bin",
	398	NULL
	399	};
	400	int ret;
7a54f46b	401	argv = argv_split(GFP_KERNEL, cmd, NULL);
15d94b82 RH	402	if (argv) {
	403	ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
	404	argv_free(argv);
	405	} else {
15d94b82 RH	406	ret = -ENOMEM;
	407	}
	408
7a54f46b JS	409	return ret;
	410	}
	411
	412	static int __orderly_reboot(void)
	413	{
	414	int ret;
	415
	416	ret = run_cmd(reboot_cmd);
	417
	418	if (ret) {
	419	pr_warn("Failed to start orderly reboot: forcing the issue\n");
	420	emergency_sync();
	421	kernel_restart(NULL);
	422	}
	423
	424	return ret;
	425	}
	426
	427	static int __orderly_poweroff(bool force)
	428	{
	429	int ret;
	430
	431	ret = run_cmd(poweroff_cmd);
	432
15d94b82	433	if (ret && force) {
972ee83d	434	pr_warn("Failed to start orderly shutdown: forcing the issue\n");
7a54f46b	435
15d94b82 RH	436	/*
	437	* I guess this should try to kick off some daemon to sync and
	438	* poweroff asap. Or not even bother syncing if we're doing an
	439	* emergency shutdown?
	440	*/
	441	emergency_sync();
	442	kernel_power_off();
	443	}
	444
	445	return ret;
	446	}
	447
	448	static bool poweroff_force;
	449
	450	static void poweroff_work_func(struct work_struct *work)
	451	{
	452	__orderly_poweroff(poweroff_force);
	453	}
	454
	455	static DECLARE_WORK(poweroff_work, poweroff_work_func);
	456
	457	/**
	458	* orderly_poweroff - Trigger an orderly system poweroff
	459	* @force: force poweroff if command execution fails
	460	*
	461	* This may be called from any context to trigger a system shutdown.
	462	* If the orderly shutdown fails, it will force an immediate shutdown.
	463	*/
7a54f46b	464	void orderly_poweroff(bool force)
15d94b82 RH	465	{
	466	if (force) /* do not override the pending "true" */
	467	poweroff_force = true;
	468	schedule_work(&poweroff_work);
15d94b82 RH	469	}
15d94b82 RH	470	EXPORT_SYMBOL_GPL(orderly_poweroff);
1b3a5d02	471
7a54f46b JS	472	static void reboot_work_func(struct work_struct *work)
	473	{
	474	__orderly_reboot();
	475	}
	476
	477	static DECLARE_WORK(reboot_work, reboot_work_func);
	478
	479	/**
	480	* orderly_reboot - Trigger an orderly system reboot
	481	*
	482	* This may be called from any context to trigger a system reboot.
	483	* If the orderly reboot fails, it will force an immediate reboot.
	484	*/
	485	void orderly_reboot(void)
	486	{
	487	schedule_work(&reboot_work);
	488	}
	489	EXPORT_SYMBOL_GPL(orderly_reboot);
	490
1b3a5d02 RH	491	static int __init reboot_setup(char *str)
	492	{
	493	for (;;) {
	494	/*
	495	* Having anything passed on the command line via
	496	* reboot= will cause us to disable DMI checking
	497	* below.
	498	*/
	499	reboot_default = 0;
	500
	501	switch (*str) {
	502	case 'w':
	503	reboot_mode = REBOOT_WARM;
	504	break;
	505
	506	case 'c':
	507	reboot_mode = REBOOT_COLD;
	508	break;
	509
	510	case 'h':
	511	reboot_mode = REBOOT_HARD;
	512	break;
	513
	514	case 's':
616feab7 FF	515	{
	516	int rc;
	517
	518	if (isdigit(*(str+1))) {
	519	rc = kstrtoint(str+1, 0, &reboot_cpu);
	520	if (rc)
	521	return rc;
	522	} else if (str[1] == 'm' && str[2] == 'p' &&
	523	isdigit(*(str+3))) {
	524	rc = kstrtoint(str+3, 0, &reboot_cpu);
	525	if (rc)
	526	return rc;
	527	} else
1b3a5d02 RH	528	reboot_mode = REBOOT_SOFT;
1b3a5d02 RH	529	break;
616feab7	530	}
1b3a5d02 RH	531	case 'g':
	532	reboot_mode = REBOOT_GPIO;
	533	break;
	534
	535	case 'b':
	536	case 'a':
	537	case 'k':
	538	case 't':
	539	case 'e':
	540	case 'p':
	541	reboot_type = *str;
	542	break;
	543
	544	case 'f':
	545	reboot_force = 1;
	546	break;
	547	}
	548
	549	str = strchr(str, ',');
	550	if (str)
	551	str++;
	552	else
	553	break;
	554	}
	555	return 1;
	556	}
	557	__setup("reboot=", reboot_setup);