1/*
2 *  linux/kernel/reboot.c
3 *
4 *  Copyright (C) 2013  Linus Torvalds
5 */
6
7#define pr_fmt(fmt)	"reboot: " fmt
8
9#include <linux/ctype.h>
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
24int C_A_D = 1;
25struct pid *cad_pid;
26EXPORT_SYMBOL(cad_pid);
27
28#if defined(CONFIG_ARM) || defined(CONFIG_UNICORE32)
29#define DEFAULT_REBOOT_MODE		= REBOOT_HARD
30#else
31#define DEFAULT_REBOOT_MODE
32#endif
33enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
34
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 */
42int reboot_default = 1;
43int reboot_cpu;
44enum reboot_type reboot_type = BOOT_ACPI;
45int reboot_force;
46
47/*
48 * If set, this is used for preparing the system to power off.
49 */
50
51void (*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 */
61void emergency_restart(void)
62{
63	kmsg_dump(KMSG_DUMP_EMERG);
64	machine_emergency_restart();
65}
66EXPORT_SYMBOL_GPL(emergency_restart);
67
68void 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 */
86int register_reboot_notifier(struct notifier_block *nb)
87{
88	return blocking_notifier_chain_register(&reboot_notifier_list, nb);
89}
90EXPORT_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 */
101int unregister_reboot_notifier(struct notifier_block *nb)
102{
103	return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
104}
105EXPORT_SYMBOL(unregister_reboot_notifier);
106
107/*
108 *	Notifier list for kernel code which wants to be called
109 *	to restart the system.
110 */
111static 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 */
151int register_restart_handler(struct notifier_block *nb)
152{
153	return atomic_notifier_chain_register(&restart_handler_list, nb);
154}
155EXPORT_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 */
166int unregister_restart_handler(struct notifier_block *nb)
167{
168	return atomic_notifier_chain_unregister(&restart_handler_list, nb);
169}
170EXPORT_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 */
183void do_kernel_restart(char *cmd)
184{
185	atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
186}
187
188void migrate_to_reboot_cpu(void)
189{
190	/* The boot cpu is always logical cpu 0 */
191	int cpu = reboot_cpu;
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 */
214void kernel_restart(char *cmd)
215{
216	kernel_restart_prepare(cmd);
217	migrate_to_reboot_cpu();
218	syscore_shutdown();
219	if (!cmd)
220		pr_emerg("Restarting system\n");
221	else
222		pr_emerg("Restarting system with command '%s'\n", cmd);
223	kmsg_dump(KMSG_DUMP_RESTART);
224	machine_restart(cmd);
225}
226EXPORT_SYMBOL_GPL(kernel_restart);
227
228static void kernel_shutdown_prepare(enum system_states state)
229{
230	blocking_notifier_call_chain(&reboot_notifier_list,
231		(state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
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 */
241void kernel_halt(void)
242{
243	kernel_shutdown_prepare(SYSTEM_HALT);
244	migrate_to_reboot_cpu();
245	syscore_shutdown();
246	pr_emerg("System halted\n");
247	kmsg_dump(KMSG_DUMP_HALT);
248	machine_halt();
249}
250EXPORT_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 */
257void 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();
264	pr_emerg("Power down\n");
265	kmsg_dump(KMSG_DUMP_POWEROFF);
266	machine_power_off();
267}
268EXPORT_SYMBOL_GPL(kernel_power_off);
269
270static 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 */
280SYSCALL_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 ||
293			(magic2 != LINUX_REBOOT_MAGIC2 &&
294			magic2 != LINUX_REBOOT_MAGIC2A &&
295			magic2 != LINUX_REBOOT_MAGIC2B &&
296			magic2 != LINUX_REBOOT_MAGIC2C))
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:
339		ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
340		if (ret < 0) {
341			ret = -EFAULT;
342			break;
343		}
344		buffer[sizeof(buffer) - 1] = '\0';
345
346		kernel_restart(buffer);
347		break;
348
349#ifdef CONFIG_KEXEC
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
369static 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 */
379void 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
389char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
390static const char reboot_cmd[] = "/sbin/reboot";
391
392static int run_cmd(const char *cmd)
393{
394	char **argv;
395	static char *envp[] = {
396		"HOME=/",
397		"PATH=/sbin:/bin:/usr/sbin:/usr/bin",
398		NULL
399	};
400	int ret;
401	argv = argv_split(GFP_KERNEL, cmd, NULL);
402	if (argv) {
403		ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
404		argv_free(argv);
405	} else {
406		ret = -ENOMEM;
407	}
408
409	return ret;
410}
411
412static 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
427static int __orderly_poweroff(bool force)
428{
429	int ret;
430
431	ret = run_cmd(poweroff_cmd);
432
433	if (ret && force) {
434		pr_warn("Failed to start orderly shutdown: forcing the issue\n");
435
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
448static bool poweroff_force;
449
450static void poweroff_work_func(struct work_struct *work)
451{
452	__orderly_poweroff(poweroff_force);
453}
454
455static 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 */
464void orderly_poweroff(bool force)
465{
466	if (force) /* do not override the pending "true" */
467		poweroff_force = true;
468	schedule_work(&poweroff_work);
469}
470EXPORT_SYMBOL_GPL(orderly_poweroff);
471
472static void reboot_work_func(struct work_struct *work)
473{
474	__orderly_reboot();
475}
476
477static 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 */
485void orderly_reboot(void)
486{
487	schedule_work(&reboot_work);
488}
489EXPORT_SYMBOL_GPL(orderly_reboot);
490
491static 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':
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
528				reboot_mode = REBOOT_SOFT;
529			break;
530		}
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);
558