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