reboot.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  linux/kernel/reboot.c
   4 *
   5 *  Copyright (C) 2013  Linus Torvalds
   6 */
   7
   8#define pr_fmt(fmt)	"reboot: " fmt
   9
  10#include <linux/atomic.h>
  11#include <linux/ctype.h>
  12#include <linux/export.h>
  13#include <linux/kexec.h>
  14#include <linux/kmod.h>
  15#include <linux/kmsg_dump.h>
  16#include <linux/reboot.h>
  17#include <linux/suspend.h>
  18#include <linux/syscalls.h>
  19#include <linux/syscore_ops.h>
  20#include <linux/uaccess.h>
  21
  22/*
  23 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
  24 */
  25
  26static int C_A_D = 1;
  27struct pid *cad_pid;
  28EXPORT_SYMBOL(cad_pid);
  29
  30#if defined(CONFIG_ARM)
  31#define DEFAULT_REBOOT_MODE		= REBOOT_HARD
  32#else
  33#define DEFAULT_REBOOT_MODE
  34#endif
  35enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
  36EXPORT_SYMBOL_GPL(reboot_mode);
  37enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
  38
  39static enum hw_protection_action hw_protection_action = HWPROT_ACT_SHUTDOWN;
  40
  41/*
  42 * This variable is used privately to keep track of whether or not
  43 * reboot_type is still set to its default value (i.e., reboot= hasn't
  44 * been set on the command line).  This is needed so that we can
  45 * suppress DMI scanning for reboot quirks.  Without it, it's
  46 * impossible to override a faulty reboot quirk without recompiling.
  47 */
  48int reboot_default = 1;
  49int reboot_cpu;
  50enum reboot_type reboot_type = BOOT_ACPI;
  51int reboot_force;
  52
  53struct sys_off_handler {
  54	struct notifier_block nb;
  55	int (*sys_off_cb)(struct sys_off_data *data);
  56	void *cb_data;
  57	enum sys_off_mode mode;
  58	bool blocking;
  59	void *list;
  60	struct device *dev;
  61};
  62
  63/*
  64 * This variable is used to indicate if a halt was initiated instead of a
  65 * reboot when the reboot call was invoked with LINUX_REBOOT_CMD_POWER_OFF, but
  66 * the system cannot be powered off. This allowes kernel_halt() to notify users
  67 * of that.
  68 */
  69static bool poweroff_fallback_to_halt;
  70
  71/*
  72 * Temporary stub that prevents linkage failure while we're in process
  73 * of removing all uses of legacy pm_power_off() around the kernel.
  74 */
  75void __weak (*pm_power_off)(void);
  76
  77/*
  78 *	Notifier list for kernel code which wants to be called
  79 *	at shutdown. This is used to stop any idling DMA operations
  80 *	and the like.
  81 */
  82static BLOCKING_NOTIFIER_HEAD(reboot_notifier_list);
  83
  84/**
  85 *	emergency_restart - reboot the system
  86 *
  87 *	Without shutting down any hardware or taking any locks
  88 *	reboot the system.  This is called when we know we are in
  89 *	trouble so this is our best effort to reboot.  This is
  90 *	safe to call in interrupt context.
  91 */
  92void emergency_restart(void)
  93{
  94	kmsg_dump(KMSG_DUMP_EMERG);
  95	system_state = SYSTEM_RESTART;
  96	machine_emergency_restart();
  97}
  98EXPORT_SYMBOL_GPL(emergency_restart);
  99
 100void kernel_restart_prepare(char *cmd)
 101{
 102	blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
 103	system_state = SYSTEM_RESTART;
 104	usermodehelper_disable();
 105	device_shutdown();
 106}
 107
 108/**
 109 *	register_reboot_notifier - Register function to be called at reboot time
 110 *	@nb: Info about notifier function to be called
 111 *
 112 *	Registers a function with the list of functions
 113 *	to be called at reboot time.
 114 *
 115 *	Currently always returns zero, as blocking_notifier_chain_register()
 116 *	always returns zero.
 117 */
 118int register_reboot_notifier(struct notifier_block *nb)
 119{
 120	return blocking_notifier_chain_register(&reboot_notifier_list, nb);
 121}
 122EXPORT_SYMBOL(register_reboot_notifier);
 123
 124/**
 125 *	unregister_reboot_notifier - Unregister previously registered reboot notifier
 126 *	@nb: Hook to be unregistered
 127 *
 128 *	Unregisters a previously registered reboot
 129 *	notifier function.
 130 *
 131 *	Returns zero on success, or %-ENOENT on failure.
 132 */
 133int unregister_reboot_notifier(struct notifier_block *nb)
 134{
 135	return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
 136}
 137EXPORT_SYMBOL(unregister_reboot_notifier);
 138
 139static void devm_unregister_reboot_notifier(struct device *dev, void *res)
 140{
 141	WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
 142}
 143
 144int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
 145{
 146	struct notifier_block **rcnb;
 147	int ret;
 148
 149	rcnb = devres_alloc(devm_unregister_reboot_notifier,
 150			    sizeof(*rcnb), GFP_KERNEL);
 151	if (!rcnb)
 152		return -ENOMEM;
 153
 154	ret = register_reboot_notifier(nb);
 155	if (!ret) {
 156		*rcnb = nb;
 157		devres_add(dev, rcnb);
 158	} else {
 159		devres_free(rcnb);
 160	}
 161
 162	return ret;
 163}
 164EXPORT_SYMBOL(devm_register_reboot_notifier);
 165
 166/*
 167 *	Notifier list for kernel code which wants to be called
 168 *	to restart the system.
 169 */
 170static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
 171
 172/**
 173 *	register_restart_handler - Register function to be called to reset
 174 *				   the system
 175 *	@nb: Info about handler function to be called
 176 *	@nb->priority:	Handler priority. Handlers should follow the
 177 *			following guidelines for setting priorities.
 178 *			0:	Restart handler of last resort,
 179 *				with limited restart capabilities
 180 *			128:	Default restart handler; use if no other
 181 *				restart handler is expected to be available,
 182 *				and/or if restart functionality is
 183 *				sufficient to restart the entire system
 184 *			255:	Highest priority restart handler, will
 185 *				preempt all other restart handlers
 186 *
 187 *	Registers a function with code to be called to restart the
 188 *	system.
 189 *
 190 *	Registered functions will be called from machine_restart as last
 191 *	step of the restart sequence (if the architecture specific
 192 *	machine_restart function calls do_kernel_restart - see below
 193 *	for details).
 194 *	Registered functions are expected to restart the system immediately.
 195 *	If more than one function is registered, the restart handler priority
 196 *	selects which function will be called first.
 197 *
 198 *	Restart handlers are expected to be registered from non-architecture
 199 *	code, typically from drivers. A typical use case would be a system
 200 *	where restart functionality is provided through a watchdog. Multiple
 201 *	restart handlers may exist; for example, one restart handler might
 202 *	restart the entire system, while another only restarts the CPU.
 203 *	In such cases, the restart handler which only restarts part of the
 204 *	hardware is expected to register with low priority to ensure that
 205 *	it only runs if no other means to restart the system is available.
 206 *
 207 *	Currently always returns zero, as atomic_notifier_chain_register()
 208 *	always returns zero.
 209 */
 210int register_restart_handler(struct notifier_block *nb)
 211{
 212	return atomic_notifier_chain_register(&restart_handler_list, nb);
 213}
 214EXPORT_SYMBOL(register_restart_handler);
 215
 216/**
 217 *	unregister_restart_handler - Unregister previously registered
 218 *				     restart handler
 219 *	@nb: Hook to be unregistered
 220 *
 221 *	Unregisters a previously registered restart handler function.
 222 *
 223 *	Returns zero on success, or %-ENOENT on failure.
 224 */
 225int unregister_restart_handler(struct notifier_block *nb)
 226{
 227	return atomic_notifier_chain_unregister(&restart_handler_list, nb);
 228}
 229EXPORT_SYMBOL(unregister_restart_handler);
 230
 231/**
 232 *	do_kernel_restart - Execute kernel restart handler call chain
 233 *
 234 *	@cmd: pointer to buffer containing command to execute for restart
 235 *		or %NULL
 236 *
 237 *	Calls functions registered with register_restart_handler.
 238 *
 239 *	Expected to be called from machine_restart as last step of the restart
 240 *	sequence.
 241 *
 242 *	Restarts the system immediately if a restart handler function has been
 243 *	registered. Otherwise does nothing.
 244 */
 245void do_kernel_restart(char *cmd)
 246{
 247	atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
 248}
 249
 250void migrate_to_reboot_cpu(void)
 251{
 252	/* The boot cpu is always logical cpu 0 */
 253	int cpu = reboot_cpu;
 254
 255	cpu_hotplug_disable();
 256
 257	/* Make certain the cpu I'm about to reboot on is online */
 258	if (!cpu_online(cpu))
 259		cpu = cpumask_first(cpu_online_mask);
 260
 261	/* Prevent races with other tasks migrating this task */
 262	current->flags |= PF_NO_SETAFFINITY;
 263
 264	/* Make certain I only run on the appropriate processor */
 265	set_cpus_allowed_ptr(current, cpumask_of(cpu));
 266}
 267
 268/*
 269 *	Notifier list for kernel code which wants to be called
 270 *	to prepare system for restart.
 271 */
 272static BLOCKING_NOTIFIER_HEAD(restart_prep_handler_list);
 273
 274static void do_kernel_restart_prepare(void)
 275{
 276	blocking_notifier_call_chain(&restart_prep_handler_list, 0, NULL);
 277}
 278
 279/**
 280 *	kernel_restart - reboot the system
 281 *	@cmd: pointer to buffer containing command to execute for restart
 282 *		or %NULL
 283 *
 284 *	Shutdown everything and perform a clean reboot.
 285 *	This is not safe to call in interrupt context.
 286 */
 287void kernel_restart(char *cmd)
 288{
 289	kernel_restart_prepare(cmd);
 290	do_kernel_restart_prepare();
 291	migrate_to_reboot_cpu();
 292	syscore_shutdown();
 293	if (!cmd)
 294		pr_emerg("Restarting system\n");
 295	else
 296		pr_emerg("Restarting system with command '%s'\n", cmd);
 297	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 298	machine_restart(cmd);
 299}
 300EXPORT_SYMBOL_GPL(kernel_restart);
 301
 302static void kernel_shutdown_prepare(enum system_states state)
 303{
 304	blocking_notifier_call_chain(&reboot_notifier_list,
 305		(state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
 306	system_state = state;
 307	usermodehelper_disable();
 308	device_shutdown();
 309}
 310/**
 311 *	kernel_halt - halt the system
 312 *
 313 *	Shutdown everything and perform a clean system halt.
 314 */
 315void kernel_halt(void)
 316{
 317	kernel_shutdown_prepare(SYSTEM_HALT);
 318	migrate_to_reboot_cpu();
 319	syscore_shutdown();
 320	if (poweroff_fallback_to_halt)
 321		pr_emerg("Power off not available: System halted instead\n");
 322	else
 323		pr_emerg("System halted\n");
 324	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 325	machine_halt();
 326}
 327EXPORT_SYMBOL_GPL(kernel_halt);
 328
 329/*
 330 *	Notifier list for kernel code which wants to be called
 331 *	to prepare system for power off.
 332 */
 333static BLOCKING_NOTIFIER_HEAD(power_off_prep_handler_list);
 334
 335/*
 336 *	Notifier list for kernel code which wants to be called
 337 *	to power off system.
 338 */
 339static ATOMIC_NOTIFIER_HEAD(power_off_handler_list);
 340
 341static int sys_off_notify(struct notifier_block *nb,
 342			  unsigned long mode, void *cmd)
 343{
 344	struct sys_off_handler *handler;
 345	struct sys_off_data data = {};
 346
 347	handler = container_of(nb, struct sys_off_handler, nb);
 348	data.cb_data = handler->cb_data;
 349	data.mode = mode;
 350	data.cmd = cmd;
 351	data.dev = handler->dev;
 352
 353	return handler->sys_off_cb(&data);
 354}
 355
 356static struct sys_off_handler platform_sys_off_handler;
 357
 358static struct sys_off_handler *alloc_sys_off_handler(int priority)
 359{
 360	struct sys_off_handler *handler;
 361	gfp_t flags;
 362
 363	/*
 364	 * Platforms like m68k can't allocate sys_off handler dynamically
 365	 * at the early boot time because memory allocator isn't available yet.
 366	 */
 367	if (priority == SYS_OFF_PRIO_PLATFORM) {
 368		handler = &platform_sys_off_handler;
 369		if (handler->cb_data)
 370			return ERR_PTR(-EBUSY);
 371	} else {
 372		if (system_state > SYSTEM_RUNNING)
 373			flags = GFP_ATOMIC;
 374		else
 375			flags = GFP_KERNEL;
 376
 377		handler = kzalloc(sizeof(*handler), flags);
 378		if (!handler)
 379			return ERR_PTR(-ENOMEM);
 380	}
 381
 382	return handler;
 383}
 384
 385static void free_sys_off_handler(struct sys_off_handler *handler)
 386{
 387	if (handler == &platform_sys_off_handler)
 388		memset(handler, 0, sizeof(*handler));
 389	else
 390		kfree(handler);
 391}
 392
 393/**
 394 *	register_sys_off_handler - Register sys-off handler
 395 *	@mode: Sys-off mode
 396 *	@priority: Handler priority
 397 *	@callback: Callback function
 398 *	@cb_data: Callback argument
 399 *
 400 *	Registers system power-off or restart handler that will be invoked
 401 *	at the step corresponding to the given sys-off mode. Handler's callback
 402 *	should return NOTIFY_DONE to permit execution of the next handler in
 403 *	the call chain or NOTIFY_STOP to break the chain (in error case for
 404 *	example).
 405 *
 406 *	Multiple handlers can be registered at the default priority level.
 407 *
 408 *	Only one handler can be registered at the non-default priority level,
 409 *	otherwise ERR_PTR(-EBUSY) is returned.
 410 *
 411 *	Returns a new instance of struct sys_off_handler on success, or
 412 *	an ERR_PTR()-encoded error code otherwise.
 413 */
 414struct sys_off_handler *
 415register_sys_off_handler(enum sys_off_mode mode,
 416			 int priority,
 417			 int (*callback)(struct sys_off_data *data),
 418			 void *cb_data)
 419{
 420	struct sys_off_handler *handler;
 421	int err;
 422
 423	handler = alloc_sys_off_handler(priority);
 424	if (IS_ERR(handler))
 425		return handler;
 426
 427	switch (mode) {
 428	case SYS_OFF_MODE_POWER_OFF_PREPARE:
 429		handler->list = &power_off_prep_handler_list;
 430		handler->blocking = true;
 431		break;
 432
 433	case SYS_OFF_MODE_POWER_OFF:
 434		handler->list = &power_off_handler_list;
 435		break;
 436
 437	case SYS_OFF_MODE_RESTART_PREPARE:
 438		handler->list = &restart_prep_handler_list;
 439		handler->blocking = true;
 440		break;
 441
 442	case SYS_OFF_MODE_RESTART:
 443		handler->list = &restart_handler_list;
 444		break;
 445
 446	default:
 447		free_sys_off_handler(handler);
 448		return ERR_PTR(-EINVAL);
 449	}
 450
 451	handler->nb.notifier_call = sys_off_notify;
 452	handler->nb.priority = priority;
 453	handler->sys_off_cb = callback;
 454	handler->cb_data = cb_data;
 455	handler->mode = mode;
 456
 457	if (handler->blocking) {
 458		if (priority == SYS_OFF_PRIO_DEFAULT)
 459			err = blocking_notifier_chain_register(handler->list,
 460							       &handler->nb);
 461		else
 462			err = blocking_notifier_chain_register_unique_prio(handler->list,
 463									   &handler->nb);
 464	} else {
 465		if (priority == SYS_OFF_PRIO_DEFAULT)
 466			err = atomic_notifier_chain_register(handler->list,
 467							     &handler->nb);
 468		else
 469			err = atomic_notifier_chain_register_unique_prio(handler->list,
 470									 &handler->nb);
 471	}
 472
 473	if (err) {
 474		free_sys_off_handler(handler);
 475		return ERR_PTR(err);
 476	}
 477
 478	return handler;
 479}
 480EXPORT_SYMBOL_GPL(register_sys_off_handler);
 481
 482/**
 483 *	unregister_sys_off_handler - Unregister sys-off handler
 484 *	@handler: Sys-off handler
 485 *
 486 *	Unregisters given sys-off handler.
 487 */
 488void unregister_sys_off_handler(struct sys_off_handler *handler)
 489{
 490	int err;
 491
 492	if (IS_ERR_OR_NULL(handler))
 493		return;
 494
 495	if (handler->blocking)
 496		err = blocking_notifier_chain_unregister(handler->list,
 497							 &handler->nb);
 498	else
 499		err = atomic_notifier_chain_unregister(handler->list,
 500						       &handler->nb);
 501
 502	/* sanity check, shall never happen */
 503	WARN_ON(err);
 504
 505	free_sys_off_handler(handler);
 506}
 507EXPORT_SYMBOL_GPL(unregister_sys_off_handler);
 508
 509static void devm_unregister_sys_off_handler(void *data)
 510{
 511	struct sys_off_handler *handler = data;
 512
 513	unregister_sys_off_handler(handler);
 514}
 515
 516/**
 517 *	devm_register_sys_off_handler - Register sys-off handler
 518 *	@dev: Device that registers handler
 519 *	@mode: Sys-off mode
 520 *	@priority: Handler priority
 521 *	@callback: Callback function
 522 *	@cb_data: Callback argument
 523 *
 524 *	Registers resource-managed sys-off handler.
 525 *
 526 *	Returns zero on success, or error code on failure.
 527 */
 528int devm_register_sys_off_handler(struct device *dev,
 529				  enum sys_off_mode mode,
 530				  int priority,
 531				  int (*callback)(struct sys_off_data *data),
 532				  void *cb_data)
 533{
 534	struct sys_off_handler *handler;
 535
 536	handler = register_sys_off_handler(mode, priority, callback, cb_data);
 537	if (IS_ERR(handler))
 538		return PTR_ERR(handler);
 539	handler->dev = dev;
 540
 541	return devm_add_action_or_reset(dev, devm_unregister_sys_off_handler,
 542					handler);
 543}
 544EXPORT_SYMBOL_GPL(devm_register_sys_off_handler);
 545
 546/**
 547 *	devm_register_power_off_handler - Register power-off handler
 548 *	@dev: Device that registers callback
 549 *	@callback: Callback function
 550 *	@cb_data: Callback's argument
 551 *
 552 *	Registers resource-managed sys-off handler with a default priority
 553 *	and using power-off mode.
 554 *
 555 *	Returns zero on success, or error code on failure.
 556 */
 557int devm_register_power_off_handler(struct device *dev,
 558				    int (*callback)(struct sys_off_data *data),
 559				    void *cb_data)
 560{
 561	return devm_register_sys_off_handler(dev,
 562					     SYS_OFF_MODE_POWER_OFF,
 563					     SYS_OFF_PRIO_DEFAULT,
 564					     callback, cb_data);
 565}
 566EXPORT_SYMBOL_GPL(devm_register_power_off_handler);
 567
 568/**
 569 *	devm_register_restart_handler - Register restart handler
 570 *	@dev: Device that registers callback
 571 *	@callback: Callback function
 572 *	@cb_data: Callback's argument
 573 *
 574 *	Registers resource-managed sys-off handler with a default priority
 575 *	and using restart mode.
 576 *
 577 *	Returns zero on success, or error code on failure.
 578 */
 579int devm_register_restart_handler(struct device *dev,
 580				  int (*callback)(struct sys_off_data *data),
 581				  void *cb_data)
 582{
 583	return devm_register_sys_off_handler(dev,
 584					     SYS_OFF_MODE_RESTART,
 585					     SYS_OFF_PRIO_DEFAULT,
 586					     callback, cb_data);
 587}
 588EXPORT_SYMBOL_GPL(devm_register_restart_handler);
 589
 590static struct sys_off_handler *platform_power_off_handler;
 591
 592static int platform_power_off_notify(struct sys_off_data *data)
 593{
 594	void (*platform_power_power_off_cb)(void) = data->cb_data;
 595
 596	platform_power_power_off_cb();
 597
 598	return NOTIFY_DONE;
 599}
 600
 601/**
 602 *	register_platform_power_off - Register platform-level power-off callback
 603 *	@power_off: Power-off callback
 604 *
 605 *	Registers power-off callback that will be called as last step
 606 *	of the power-off sequence. This callback is expected to be invoked
 607 *	for the last resort. Only one platform power-off callback is allowed
 608 *	to be registered at a time.
 609 *
 610 *	Returns zero on success, or error code on failure.
 611 */
 612int register_platform_power_off(void (*power_off)(void))
 613{
 614	struct sys_off_handler *handler;
 615
 616	handler = register_sys_off_handler(SYS_OFF_MODE_POWER_OFF,
 617					   SYS_OFF_PRIO_PLATFORM,
 618					   platform_power_off_notify,
 619					   power_off);
 620	if (IS_ERR(handler))
 621		return PTR_ERR(handler);
 622
 623	platform_power_off_handler = handler;
 624
 625	return 0;
 626}
 627EXPORT_SYMBOL_GPL(register_platform_power_off);
 628
 629/**
 630 *	unregister_platform_power_off - Unregister platform-level power-off callback
 631 *	@power_off: Power-off callback
 632 *
 633 *	Unregisters previously registered platform power-off callback.
 634 */
 635void unregister_platform_power_off(void (*power_off)(void))
 636{
 637	if (platform_power_off_handler &&
 638	    platform_power_off_handler->cb_data == power_off) {
 639		unregister_sys_off_handler(platform_power_off_handler);
 640		platform_power_off_handler = NULL;
 641	}
 642}
 643EXPORT_SYMBOL_GPL(unregister_platform_power_off);
 644
 645static int legacy_pm_power_off(struct sys_off_data *data)
 646{
 647	if (pm_power_off)
 648		pm_power_off();
 649
 650	return NOTIFY_DONE;
 651}
 652
 653static void do_kernel_power_off_prepare(void)
 654{
 655	blocking_notifier_call_chain(&power_off_prep_handler_list, 0, NULL);
 656}
 657
 658/**
 659 *	do_kernel_power_off - Execute kernel power-off handler call chain
 660 *
 661 *	Expected to be called as last step of the power-off sequence.
 662 *
 663 *	Powers off the system immediately if a power-off handler function has
 664 *	been registered. Otherwise does nothing.
 665 */
 666void do_kernel_power_off(void)
 667{
 668	struct sys_off_handler *sys_off = NULL;
 669
 670	/*
 671	 * Register sys-off handlers for legacy PM callback. This allows
 672	 * legacy PM callbacks temporary co-exist with the new sys-off API.
 673	 *
 674	 * TODO: Remove legacy handlers once all legacy PM users will be
 675	 *       switched to the sys-off based APIs.
 676	 */
 677	if (pm_power_off)
 678		sys_off = register_sys_off_handler(SYS_OFF_MODE_POWER_OFF,
 679						   SYS_OFF_PRIO_DEFAULT,
 680						   legacy_pm_power_off, NULL);
 681
 682	atomic_notifier_call_chain(&power_off_handler_list, 0, NULL);
 683
 684	unregister_sys_off_handler(sys_off);
 685}
 686
 687/**
 688 *	kernel_can_power_off - check whether system can be powered off
 689 *
 690 *	Returns true if power-off handler is registered and system can be
 691 *	powered off, false otherwise.
 692 */
 693bool kernel_can_power_off(void)
 694{
 695	return !atomic_notifier_call_chain_is_empty(&power_off_handler_list) ||
 696		pm_power_off;
 697}
 698EXPORT_SYMBOL_GPL(kernel_can_power_off);
 699
 700/**
 701 *	kernel_power_off - power_off the system
 702 *
 703 *	Shutdown everything and perform a clean system power_off.
 704 */
 705void kernel_power_off(void)
 706{
 707	kernel_shutdown_prepare(SYSTEM_POWER_OFF);
 708	do_kernel_power_off_prepare();
 709	migrate_to_reboot_cpu();
 710	syscore_shutdown();
 711	pr_emerg("Power down\n");
 712	pr_flush(1000, true);
 713	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 714	machine_power_off();
 715}
 716EXPORT_SYMBOL_GPL(kernel_power_off);
 717
 718DEFINE_MUTEX(system_transition_mutex);
 719
 720/*
 721 * Reboot system call: for obvious reasons only root may call it,
 722 * and even root needs to set up some magic numbers in the registers
 723 * so that some mistake won't make this reboot the whole machine.
 724 * You can also set the meaning of the ctrl-alt-del-key here.
 725 *
 726 * reboot doesn't sync: do that yourself before calling this.
 727 */
 728SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 729		void __user *, arg)
 730{
 731	struct pid_namespace *pid_ns = task_active_pid_ns(current);
 732	char buffer[256];
 733	int ret = 0;
 734
 735	/* We only trust the superuser with rebooting the system. */
 736	if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
 737		return -EPERM;
 738
 739	/* For safety, we require "magic" arguments. */
 740	if (magic1 != LINUX_REBOOT_MAGIC1 ||
 741			(magic2 != LINUX_REBOOT_MAGIC2 &&
 742			magic2 != LINUX_REBOOT_MAGIC2A &&
 743			magic2 != LINUX_REBOOT_MAGIC2B &&
 744			magic2 != LINUX_REBOOT_MAGIC2C))
 745		return -EINVAL;
 746
 747	/*
 748	 * If pid namespaces are enabled and the current task is in a child
 749	 * pid_namespace, the command is handled by reboot_pid_ns() which will
 750	 * call do_exit().
 751	 */
 752	ret = reboot_pid_ns(pid_ns, cmd);
 753	if (ret)
 754		return ret;
 755
 756	/* Instead of trying to make the power_off code look like
 757	 * halt when pm_power_off is not set do it the easy way.
 758	 */
 759	if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !kernel_can_power_off()) {
 760		poweroff_fallback_to_halt = true;
 761		cmd = LINUX_REBOOT_CMD_HALT;
 762	}
 763
 764	mutex_lock(&system_transition_mutex);
 765	switch (cmd) {
 766	case LINUX_REBOOT_CMD_RESTART:
 767		kernel_restart(NULL);
 768		break;
 769
 770	case LINUX_REBOOT_CMD_CAD_ON:
 771		C_A_D = 1;
 772		break;
 773
 774	case LINUX_REBOOT_CMD_CAD_OFF:
 775		C_A_D = 0;
 776		break;
 777
 778	case LINUX_REBOOT_CMD_HALT:
 779		kernel_halt();
 780		do_exit(0);
 781
 782	case LINUX_REBOOT_CMD_POWER_OFF:
 783		kernel_power_off();
 784		do_exit(0);
 785		break;
 786
 787	case LINUX_REBOOT_CMD_RESTART2:
 788		ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
 789		if (ret < 0) {
 790			ret = -EFAULT;
 791			break;
 792		}
 793		buffer[sizeof(buffer) - 1] = '\0';
 794
 795		kernel_restart(buffer);
 796		break;
 797
 798#ifdef CONFIG_KEXEC_CORE
 799	case LINUX_REBOOT_CMD_KEXEC:
 800		ret = kernel_kexec();
 801		break;
 802#endif
 803
 804#ifdef CONFIG_HIBERNATION
 805	case LINUX_REBOOT_CMD_SW_SUSPEND:
 806		ret = hibernate();
 807		break;
 808#endif
 809
 810	default:
 811		ret = -EINVAL;
 812		break;
 813	}
 814	mutex_unlock(&system_transition_mutex);
 815	return ret;
 816}
 817
 818static void deferred_cad(struct work_struct *dummy)
 819{
 820	kernel_restart(NULL);
 821}
 822
 823/*
 824 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
 825 * As it's called within an interrupt, it may NOT sync: the only choice
 826 * is whether to reboot at once, or just ignore the ctrl-alt-del.
 827 */
 828void ctrl_alt_del(void)
 829{
 830	static DECLARE_WORK(cad_work, deferred_cad);
 831
 832	if (C_A_D)
 833		schedule_work(&cad_work);
 834	else
 835		kill_cad_pid(SIGINT, 1);
 836}
 837
 838#define POWEROFF_CMD_PATH_LEN  256
 839static char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
 840static const char reboot_cmd[] = "/sbin/reboot";
 841
 842static int run_cmd(const char *cmd)
 843{
 844	char **argv;
 845	static char *envp[] = {
 846		"HOME=/",
 847		"PATH=/sbin:/bin:/usr/sbin:/usr/bin",
 848		NULL
 849	};
 850	int ret;
 851	argv = argv_split(GFP_KERNEL, cmd, NULL);
 852	if (argv) {
 853		ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
 854		argv_free(argv);
 855	} else {
 856		ret = -ENOMEM;
 857	}
 858
 859	return ret;
 860}
 861
 862static int __orderly_reboot(void)
 863{
 864	int ret;
 865
 866	ret = run_cmd(reboot_cmd);
 867
 868	if (ret) {
 869		pr_warn("Failed to start orderly reboot: forcing the issue\n");
 870		emergency_sync();
 871		kernel_restart(NULL);
 872	}
 873
 874	return ret;
 875}
 876
 877static int __orderly_poweroff(bool force)
 878{
 879	int ret;
 880
 881	ret = run_cmd(poweroff_cmd);
 882
 883	if (ret && force) {
 884		pr_warn("Failed to start orderly shutdown: forcing the issue\n");
 885
 886		/*
 887		 * I guess this should try to kick off some daemon to sync and
 888		 * poweroff asap.  Or not even bother syncing if we're doing an
 889		 * emergency shutdown?
 890		 */
 891		emergency_sync();
 892		kernel_power_off();
 893	}
 894
 895	return ret;
 896}
 897
 898static bool poweroff_force;
 899
 900static void poweroff_work_func(struct work_struct *work)
 901{
 902	__orderly_poweroff(poweroff_force);
 903}
 904
 905static DECLARE_WORK(poweroff_work, poweroff_work_func);
 906
 907/**
 908 * orderly_poweroff - Trigger an orderly system poweroff
 909 * @force: force poweroff if command execution fails
 910 *
 911 * This may be called from any context to trigger a system shutdown.
 912 * If the orderly shutdown fails, it will force an immediate shutdown.
 913 */
 914void orderly_poweroff(bool force)
 915{
 916	if (force) /* do not override the pending "true" */
 917		poweroff_force = true;
 918	schedule_work(&poweroff_work);
 919}
 920EXPORT_SYMBOL_GPL(orderly_poweroff);
 921
 922static void reboot_work_func(struct work_struct *work)
 923{
 924	__orderly_reboot();
 925}
 926
 927static DECLARE_WORK(reboot_work, reboot_work_func);
 928
 929/**
 930 * orderly_reboot - Trigger an orderly system reboot
 931 *
 932 * This may be called from any context to trigger a system reboot.
 933 * If the orderly reboot fails, it will force an immediate reboot.
 934 */
 935void orderly_reboot(void)
 936{
 937	schedule_work(&reboot_work);
 938}
 939EXPORT_SYMBOL_GPL(orderly_reboot);
 940
 941static const char *hw_protection_action_str(enum hw_protection_action action)
 942{
 943	switch (action) {
 944	case HWPROT_ACT_SHUTDOWN:
 945		return "shutdown";
 946	case HWPROT_ACT_REBOOT:
 947		return "reboot";
 948	default:
 949		return "undefined";
 950	}
 951}
 952
 953static enum hw_protection_action hw_failure_emergency_action;
 954
 955/**
 956 * hw_failure_emergency_action_func - emergency action work after a known delay
 957 * @work: work_struct associated with the emergency action function
 958 *
 959 * This function is called in very critical situations to force
 960 * a kernel poweroff or reboot after a configurable timeout value.
 961 */
 962static void hw_failure_emergency_action_func(struct work_struct *work)
 963{
 964	const char *action_str = hw_protection_action_str(hw_failure_emergency_action);
 965
 966	pr_emerg("Hardware protection timed-out. Trying forced %s\n",
 967		 action_str);
 968
 969	/*
 970	 * We have reached here after the emergency action waiting period has
 971	 * expired. This means orderly_poweroff/reboot has not been able to
 972	 * shut off the system for some reason.
 973	 *
 974	 * Try to shut off the system immediately if possible
 975	 */
 976
 977	if (hw_failure_emergency_action == HWPROT_ACT_REBOOT)
 978		kernel_restart(NULL);
 979	else
 980		kernel_power_off();
 981
 982	/*
 983	 * Worst of the worst case trigger emergency restart
 984	 */
 985	pr_emerg("Hardware protection %s failed. Trying emergency restart\n",
 986		 action_str);
 987	emergency_restart();
 988}
 989
 990static DECLARE_DELAYED_WORK(hw_failure_emergency_action_work,
 991			    hw_failure_emergency_action_func);
 992
 993/**
 994 * hw_failure_emergency_schedule - Schedule an emergency system shutdown or reboot
 995 *
 996 * @action:		The hardware protection action to be taken
 997 * @action_delay_ms:	Time in milliseconds to elapse before triggering action
 998 *
 999 * This may be called from any critical situation to trigger a system shutdown
1000 * or reboot after a given period of time.
1001 * If time is negative this is not scheduled.
1002 */
1003static void hw_failure_emergency_schedule(enum hw_protection_action action,
1004					  int action_delay_ms)
1005{
1006	if (action_delay_ms <= 0)
1007		return;
1008	hw_failure_emergency_action = action;
1009	schedule_delayed_work(&hw_failure_emergency_action_work,
1010			      msecs_to_jiffies(action_delay_ms));
1011}
1012
1013/**
1014 * __hw_protection_trigger - Trigger an emergency system shutdown or reboot
1015 *
1016 * @reason:		Reason of emergency shutdown or reboot to be printed.
1017 * @ms_until_forced:	Time to wait for orderly shutdown or reboot before
1018 *			triggering it. Negative value disables the forced
1019 *			shutdown or reboot.
1020 * @action:		The hardware protection action to be taken.
1021 *
1022 * Initiate an emergency system shutdown or reboot in order to protect
1023 * hardware from further damage. Usage examples include a thermal protection.
1024 * NOTE: The request is ignored if protection shutdown or reboot is already
1025 * pending even if the previous request has given a large timeout for forced
1026 * shutdown/reboot.
1027 */
1028void __hw_protection_trigger(const char *reason, int ms_until_forced,
1029			     enum hw_protection_action action)
1030{
1031	static atomic_t allow_proceed = ATOMIC_INIT(1);
1032
1033	if (action == HWPROT_ACT_DEFAULT)
1034		action = hw_protection_action;
1035
1036	pr_emerg("HARDWARE PROTECTION %s (%s)\n",
1037		 hw_protection_action_str(action), reason);
1038
1039	/* Shutdown should be initiated only once. */
1040	if (!atomic_dec_and_test(&allow_proceed))
1041		return;
1042
1043	/*
1044	 * Queue a backup emergency shutdown in the event of
1045	 * orderly_poweroff failure
1046	 */
1047	hw_failure_emergency_schedule(action, ms_until_forced);
1048	if (action == HWPROT_ACT_REBOOT)
1049		orderly_reboot();
1050	else
1051		orderly_poweroff(true);
1052}
1053EXPORT_SYMBOL_GPL(__hw_protection_trigger);
1054
1055static bool hw_protection_action_parse(const char *str,
1056				       enum hw_protection_action *action)
1057{
1058	if (sysfs_streq(str, "shutdown"))
1059		*action = HWPROT_ACT_SHUTDOWN;
1060	else if (sysfs_streq(str, "reboot"))
1061		*action = HWPROT_ACT_REBOOT;
1062	else
1063		return false;
1064
1065	return true;
1066}
1067
1068static int __init hw_protection_setup(char *str)
1069{
1070	hw_protection_action_parse(str, &hw_protection_action);
1071	return 1;
1072}
1073__setup("hw_protection=", hw_protection_setup);
1074
1075#ifdef CONFIG_SYSFS
1076static ssize_t hw_protection_show(struct kobject *kobj,
1077				  struct kobj_attribute *attr, char *buf)
1078{
1079	return sysfs_emit(buf, "%s\n",
1080			  hw_protection_action_str(hw_protection_action));
1081}
1082static ssize_t hw_protection_store(struct kobject *kobj,
1083				   struct kobj_attribute *attr, const char *buf,
1084				   size_t count)
1085{
1086	if (!capable(CAP_SYS_ADMIN))
1087		return -EPERM;
1088
1089	if (!hw_protection_action_parse(buf, &hw_protection_action))
1090		return -EINVAL;
1091
1092	return count;
1093}
1094static struct kobj_attribute hw_protection_attr = __ATTR_RW(hw_protection);
1095#endif
1096
1097static int __init reboot_setup(char *str)
1098{
1099	for (;;) {
1100		enum reboot_mode *mode;
1101
1102		/*
1103		 * Having anything passed on the command line via
1104		 * reboot= will cause us to disable DMI checking
1105		 * below.
1106		 */
1107		reboot_default = 0;
1108
1109		if (!strncmp(str, "panic_", 6)) {
1110			mode = &panic_reboot_mode;
1111			str += 6;
1112		} else {
1113			mode = &reboot_mode;
1114		}
1115
1116		switch (*str) {
1117		case 'w':
1118			*mode = REBOOT_WARM;
1119			break;
1120
1121		case 'c':
1122			*mode = REBOOT_COLD;
1123			break;
1124
1125		case 'h':
1126			*mode = REBOOT_HARD;
1127			break;
1128
1129		case 's':
1130			/*
1131			 * reboot_cpu is s[mp]#### with #### being the processor
1132			 * to be used for rebooting. Skip 's' or 'smp' prefix.
1133			 */
1134			str += str[1] == 'm' && str[2] == 'p' ? 3 : 1;
1135
1136			if (isdigit(str[0])) {
1137				int cpu = simple_strtoul(str, NULL, 0);
1138
1139				if (cpu >= num_possible_cpus()) {
1140					pr_err("Ignoring the CPU number in reboot= option. "
1141					"CPU %d exceeds possible cpu number %d\n",
1142					cpu, num_possible_cpus());
1143					break;
1144				}
1145				reboot_cpu = cpu;
1146			} else
1147				*mode = REBOOT_SOFT;
1148			break;
1149
1150		case 'g':
1151			*mode = REBOOT_GPIO;
1152			break;
1153
1154		case 'b':
1155		case 'a':
1156		case 'k':
1157		case 't':
1158		case 'e':
1159		case 'p':
1160			reboot_type = *str;
1161			break;
1162
1163		case 'f':
1164			reboot_force = 1;
1165			break;
1166		}
1167
1168		str = strchr(str, ',');
1169		if (str)
1170			str++;
1171		else
1172			break;
1173	}
1174	return 1;
1175}
1176__setup("reboot=", reboot_setup);
1177
1178#ifdef CONFIG_SYSFS
1179
1180#define REBOOT_COLD_STR		"cold"
1181#define REBOOT_WARM_STR		"warm"
1182#define REBOOT_HARD_STR		"hard"
1183#define REBOOT_SOFT_STR		"soft"
1184#define REBOOT_GPIO_STR		"gpio"
1185#define REBOOT_UNDEFINED_STR	"undefined"
1186
1187#define BOOT_TRIPLE_STR		"triple"
1188#define BOOT_KBD_STR		"kbd"
1189#define BOOT_BIOS_STR		"bios"
1190#define BOOT_ACPI_STR		"acpi"
1191#define BOOT_EFI_STR		"efi"
1192#define BOOT_PCI_STR		"pci"
1193
1194static ssize_t mode_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
1195{
1196	const char *val;
1197
1198	switch (reboot_mode) {
1199	case REBOOT_COLD:
1200		val = REBOOT_COLD_STR;
1201		break;
1202	case REBOOT_WARM:
1203		val = REBOOT_WARM_STR;
1204		break;
1205	case REBOOT_HARD:
1206		val = REBOOT_HARD_STR;
1207		break;
1208	case REBOOT_SOFT:
1209		val = REBOOT_SOFT_STR;
1210		break;
1211	case REBOOT_GPIO:
1212		val = REBOOT_GPIO_STR;
1213		break;
1214	default:
1215		val = REBOOT_UNDEFINED_STR;
1216	}
1217
1218	return sysfs_emit(buf, "%s\n", val);
1219}
1220static ssize_t mode_store(struct kobject *kobj, struct kobj_attribute *attr,
1221			  const char *buf, size_t count)
1222{
1223	if (!capable(CAP_SYS_BOOT))
1224		return -EPERM;
1225
1226	if (!strncmp(buf, REBOOT_COLD_STR, strlen(REBOOT_COLD_STR)))
1227		reboot_mode = REBOOT_COLD;
1228	else if (!strncmp(buf, REBOOT_WARM_STR, strlen(REBOOT_WARM_STR)))
1229		reboot_mode = REBOOT_WARM;
1230	else if (!strncmp(buf, REBOOT_HARD_STR, strlen(REBOOT_HARD_STR)))
1231		reboot_mode = REBOOT_HARD;
1232	else if (!strncmp(buf, REBOOT_SOFT_STR, strlen(REBOOT_SOFT_STR)))
1233		reboot_mode = REBOOT_SOFT;
1234	else if (!strncmp(buf, REBOOT_GPIO_STR, strlen(REBOOT_GPIO_STR)))
1235		reboot_mode = REBOOT_GPIO;
1236	else
1237		return -EINVAL;
1238
1239	reboot_default = 0;
1240
1241	return count;
1242}
1243static struct kobj_attribute reboot_mode_attr = __ATTR_RW(mode);
1244
1245#ifdef CONFIG_X86
1246static ssize_t force_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
1247{
1248	return sysfs_emit(buf, "%d\n", reboot_force);
1249}
1250static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
1251			  const char *buf, size_t count)
1252{
1253	bool res;
1254
1255	if (!capable(CAP_SYS_BOOT))
1256		return -EPERM;
1257
1258	if (kstrtobool(buf, &res))
1259		return -EINVAL;
1260
1261	reboot_default = 0;
1262	reboot_force = res;
1263
1264	return count;
1265}
1266static struct kobj_attribute reboot_force_attr = __ATTR_RW(force);
1267
1268static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
1269{
1270	const char *val;
1271
1272	switch (reboot_type) {
1273	case BOOT_TRIPLE:
1274		val = BOOT_TRIPLE_STR;
1275		break;
1276	case BOOT_KBD:
1277		val = BOOT_KBD_STR;
1278		break;
1279	case BOOT_BIOS:
1280		val = BOOT_BIOS_STR;
1281		break;
1282	case BOOT_ACPI:
1283		val = BOOT_ACPI_STR;
1284		break;
1285	case BOOT_EFI:
1286		val = BOOT_EFI_STR;
1287		break;
1288	case BOOT_CF9_FORCE:
1289		val = BOOT_PCI_STR;
1290		break;
1291	default:
1292		val = REBOOT_UNDEFINED_STR;
1293	}
1294
1295	return sysfs_emit(buf, "%s\n", val);
1296}
1297static ssize_t type_store(struct kobject *kobj, struct kobj_attribute *attr,
1298			  const char *buf, size_t count)
1299{
1300	if (!capable(CAP_SYS_BOOT))
1301		return -EPERM;
1302
1303	if (!strncmp(buf, BOOT_TRIPLE_STR, strlen(BOOT_TRIPLE_STR)))
1304		reboot_type = BOOT_TRIPLE;
1305	else if (!strncmp(buf, BOOT_KBD_STR, strlen(BOOT_KBD_STR)))
1306		reboot_type = BOOT_KBD;
1307	else if (!strncmp(buf, BOOT_BIOS_STR, strlen(BOOT_BIOS_STR)))
1308		reboot_type = BOOT_BIOS;
1309	else if (!strncmp(buf, BOOT_ACPI_STR, strlen(BOOT_ACPI_STR)))
1310		reboot_type = BOOT_ACPI;
1311	else if (!strncmp(buf, BOOT_EFI_STR, strlen(BOOT_EFI_STR)))
1312		reboot_type = BOOT_EFI;
1313	else if (!strncmp(buf, BOOT_PCI_STR, strlen(BOOT_PCI_STR)))
1314		reboot_type = BOOT_CF9_FORCE;
1315	else
1316		return -EINVAL;
1317
1318	reboot_default = 0;
1319
1320	return count;
1321}
1322static struct kobj_attribute reboot_type_attr = __ATTR_RW(type);
1323#endif
1324
1325#ifdef CONFIG_SMP
1326static ssize_t cpu_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
1327{
1328	return sysfs_emit(buf, "%d\n", reboot_cpu);
1329}
1330static ssize_t cpu_store(struct kobject *kobj, struct kobj_attribute *attr,
1331			  const char *buf, size_t count)
1332{
1333	unsigned int cpunum;
1334	int rc;
1335
1336	if (!capable(CAP_SYS_BOOT))
1337		return -EPERM;
1338
1339	rc = kstrtouint(buf, 0, &cpunum);
1340
1341	if (rc)
1342		return rc;
1343
1344	if (cpunum >= num_possible_cpus())
1345		return -ERANGE;
1346
1347	reboot_default = 0;
1348	reboot_cpu = cpunum;
1349
1350	return count;
1351}
1352static struct kobj_attribute reboot_cpu_attr = __ATTR_RW(cpu);
1353#endif
1354
1355static struct attribute *reboot_attrs[] = {
1356	&hw_protection_attr.attr,
1357	&reboot_mode_attr.attr,
1358#ifdef CONFIG_X86
1359	&reboot_force_attr.attr,
1360	&reboot_type_attr.attr,
1361#endif
1362#ifdef CONFIG_SMP
1363	&reboot_cpu_attr.attr,
1364#endif
1365	NULL,
1366};
1367
1368#ifdef CONFIG_SYSCTL
1369static const struct ctl_table kern_reboot_table[] = {
1370	{
1371		.procname       = "poweroff_cmd",
1372		.data           = &poweroff_cmd,
1373		.maxlen         = POWEROFF_CMD_PATH_LEN,
1374		.mode           = 0644,
1375		.proc_handler   = proc_dostring,
1376	},
1377	{
1378		.procname       = "ctrl-alt-del",
1379		.data           = &C_A_D,
1380		.maxlen         = sizeof(int),
1381		.mode           = 0644,
1382		.proc_handler   = proc_dointvec,
1383	},
1384};
1385
1386static void __init kernel_reboot_sysctls_init(void)
1387{
1388	register_sysctl_init("kernel", kern_reboot_table);
1389}
1390#else
1391#define kernel_reboot_sysctls_init() do { } while (0)
1392#endif /* CONFIG_SYSCTL */
1393
1394static const struct attribute_group reboot_attr_group = {
1395	.attrs = reboot_attrs,
1396};
1397
1398static int __init reboot_ksysfs_init(void)
1399{
1400	struct kobject *reboot_kobj;
1401	int ret;
1402
1403	reboot_kobj = kobject_create_and_add("reboot", kernel_kobj);
1404	if (!reboot_kobj)
1405		return -ENOMEM;
1406
1407	ret = sysfs_create_group(reboot_kobj, &reboot_attr_group);
1408	if (ret) {
1409		kobject_put(reboot_kobj);
1410		return ret;
1411	}
1412
1413	kernel_reboot_sysctls_init();
1414
1415	return 0;
1416}
1417late_initcall(reboot_ksysfs_init);
1418
1419#endif