• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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 
24 int C_A_D = 1;
25 struct pid *cad_pid;
26 EXPORT_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
33 enum 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  */
42 int reboot_default = 1;
43 int reboot_cpu;
44 enum reboot_type reboot_type = BOOT_ACPI;
45 int reboot_force;
46 
47 /*
48  * If set, this is used for preparing the system to power off.
49  */
50 
51 void (*pm_power_off_prepare)(void);
52 
53 /**
54  *	emergency_restart - reboot the system
55  *
56  *	Without shutting down any hardware or taking any locks
57  *	reboot the system.  This is called when we know we are in
58  *	trouble so this is our best effort to reboot.  This is
59  *	safe to call in interrupt context.
60  */
emergency_restart(void)61 void emergency_restart(void)
62 {
63 	kmsg_dump(KMSG_DUMP_EMERG);
64 	machine_emergency_restart();
65 }
66 EXPORT_SYMBOL_GPL(emergency_restart);
67 
kernel_restart_prepare(char * cmd)68 void kernel_restart_prepare(char *cmd)
69 {
70 	blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
71 	system_state = SYSTEM_RESTART;
72 	usermodehelper_disable();
73 	device_shutdown();
74 }
75 
76 /**
77  *	register_reboot_notifier - Register function to be called at reboot time
78  *	@nb: Info about notifier function to be called
79  *
80  *	Registers a function with the list of functions
81  *	to be called at reboot time.
82  *
83  *	Currently always returns zero, as blocking_notifier_chain_register()
84  *	always returns zero.
85  */
register_reboot_notifier(struct notifier_block * nb)86 int register_reboot_notifier(struct notifier_block *nb)
87 {
88 	return blocking_notifier_chain_register(&reboot_notifier_list, nb);
89 }
90 EXPORT_SYMBOL(register_reboot_notifier);
91 
92 /**
93  *	unregister_reboot_notifier - Unregister previously registered reboot notifier
94  *	@nb: Hook to be unregistered
95  *
96  *	Unregisters a previously registered reboot
97  *	notifier function.
98  *
99  *	Returns zero on success, or %-ENOENT on failure.
100  */
unregister_reboot_notifier(struct notifier_block * nb)101 int unregister_reboot_notifier(struct notifier_block *nb)
102 {
103 	return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
104 }
105 EXPORT_SYMBOL(unregister_reboot_notifier);
106 
107 /*
108  *	Notifier list for kernel code which wants to be called
109  *	to restart the system.
110  */
111 static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
112 
113 /**
114  *	register_restart_handler - Register function to be called to reset
115  *				   the system
116  *	@nb: Info about handler function to be called
117  *	@nb->priority:	Handler priority. Handlers should follow the
118  *			following guidelines for setting priorities.
119  *			0:	Restart handler of last resort,
120  *				with limited restart capabilities
121  *			128:	Default restart handler; use if no other
122  *				restart handler is expected to be available,
123  *				and/or if restart functionality is
124  *				sufficient to restart the entire system
125  *			255:	Highest priority restart handler, will
126  *				preempt all other restart handlers
127  *
128  *	Registers a function with code to be called to restart the
129  *	system.
130  *
131  *	Registered functions will be called from machine_restart as last
132  *	step of the restart sequence (if the architecture specific
133  *	machine_restart function calls do_kernel_restart - see below
134  *	for details).
135  *	Registered functions are expected to restart the system immediately.
136  *	If more than one function is registered, the restart handler priority
137  *	selects which function will be called first.
138  *
139  *	Restart handlers are expected to be registered from non-architecture
140  *	code, typically from drivers. A typical use case would be a system
141  *	where restart functionality is provided through a watchdog. Multiple
142  *	restart handlers may exist; for example, one restart handler might
143  *	restart the entire system, while another only restarts the CPU.
144  *	In such cases, the restart handler which only restarts part of the
145  *	hardware is expected to register with low priority to ensure that
146  *	it only runs if no other means to restart the system is available.
147  *
148  *	Currently always returns zero, as atomic_notifier_chain_register()
149  *	always returns zero.
150  */
register_restart_handler(struct notifier_block * nb)151 int register_restart_handler(struct notifier_block *nb)
152 {
153 	return atomic_notifier_chain_register(&restart_handler_list, nb);
154 }
155 EXPORT_SYMBOL(register_restart_handler);
156 
157 /**
158  *	unregister_restart_handler - Unregister previously registered
159  *				     restart handler
160  *	@nb: Hook to be unregistered
161  *
162  *	Unregisters a previously registered restart handler function.
163  *
164  *	Returns zero on success, or %-ENOENT on failure.
165  */
unregister_restart_handler(struct notifier_block * nb)166 int unregister_restart_handler(struct notifier_block *nb)
167 {
168 	return atomic_notifier_chain_unregister(&restart_handler_list, nb);
169 }
170 EXPORT_SYMBOL(unregister_restart_handler);
171 
172 /**
173  *	do_kernel_restart - Execute kernel restart handler call chain
174  *
175  *	Calls functions registered with register_restart_handler.
176  *
177  *	Expected to be called from machine_restart as last step of the restart
178  *	sequence.
179  *
180  *	Restarts the system immediately if a restart handler function has been
181  *	registered. Otherwise does nothing.
182  */
do_kernel_restart(char * cmd)183 void do_kernel_restart(char *cmd)
184 {
185 	atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
186 }
187 
migrate_to_reboot_cpu(void)188 void 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  */
kernel_restart(char * cmd)214 void 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 }
226 EXPORT_SYMBOL_GPL(kernel_restart);
227 
kernel_shutdown_prepare(enum system_states state)228 static 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  */
kernel_halt(void)241 void 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 }
250 EXPORT_SYMBOL_GPL(kernel_halt);
251 
252 /**
253  *	kernel_power_off - power_off the system
254  *
255  *	Shutdown everything and perform a clean system power_off.
256  */
kernel_power_off(void)257 void kernel_power_off(void)
258 {
259 	kernel_shutdown_prepare(SYSTEM_POWER_OFF);
260 	if (pm_power_off_prepare)
261 		pm_power_off_prepare();
262 	migrate_to_reboot_cpu();
263 	syscore_shutdown();
264 	pr_emerg("Power down\n");
265 	kmsg_dump(KMSG_DUMP_POWEROFF);
266 	machine_power_off();
267 }
268 EXPORT_SYMBOL_GPL(kernel_power_off);
269 
270 static DEFINE_MUTEX(reboot_mutex);
271 
272 /*
273  * Reboot system call: for obvious reasons only root may call it,
274  * and even root needs to set up some magic numbers in the registers
275  * so that some mistake won't make this reboot the whole machine.
276  * You can also set the meaning of the ctrl-alt-del-key here.
277  *
278  * reboot doesn't sync: do that yourself before calling this.
279  */
SYSCALL_DEFINE4(reboot,int,magic1,int,magic2,unsigned int,cmd,void __user *,arg)280 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
281 		void __user *, arg)
282 {
283 	struct pid_namespace *pid_ns = task_active_pid_ns(current);
284 	char buffer[256];
285 	int ret = 0;
286 
287 	/* We only trust the superuser with rebooting the system. */
288 	if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
289 		return -EPERM;
290 
291 	/* For safety, we require "magic" arguments. */
292 	if (magic1 != LINUX_REBOOT_MAGIC1 ||
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 
deferred_cad(struct work_struct * dummy)369 static void deferred_cad(struct work_struct *dummy)
370 {
371 	kernel_restart(NULL);
372 }
373 
374 /*
375  * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
376  * As it's called within an interrupt, it may NOT sync: the only choice
377  * is whether to reboot at once, or just ignore the ctrl-alt-del.
378  */
ctrl_alt_del(void)379 void ctrl_alt_del(void)
380 {
381 	static DECLARE_WORK(cad_work, deferred_cad);
382 
383 	if (C_A_D)
384 		schedule_work(&cad_work);
385 	else
386 		kill_cad_pid(SIGINT, 1);
387 }
388 
389 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
390 
__orderly_poweroff(bool force)391 static int __orderly_poweroff(bool force)
392 {
393 	char **argv;
394 	static char *envp[] = {
395 		"HOME=/",
396 		"PATH=/sbin:/bin:/usr/sbin:/usr/bin",
397 		NULL
398 	};
399 	int ret;
400 
401 	argv = argv_split(GFP_KERNEL, poweroff_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 	if (ret && force) {
410 		pr_warn("Failed to start orderly shutdown: forcing the issue\n");
411 		/*
412 		 * I guess this should try to kick off some daemon to sync and
413 		 * poweroff asap.  Or not even bother syncing if we're doing an
414 		 * emergency shutdown?
415 		 */
416 		emergency_sync();
417 		kernel_power_off();
418 	}
419 
420 	return ret;
421 }
422 
423 static bool poweroff_force;
424 
poweroff_work_func(struct work_struct * work)425 static void poweroff_work_func(struct work_struct *work)
426 {
427 	__orderly_poweroff(poweroff_force);
428 }
429 
430 static DECLARE_WORK(poweroff_work, poweroff_work_func);
431 
432 /**
433  * orderly_poweroff - Trigger an orderly system poweroff
434  * @force: force poweroff if command execution fails
435  *
436  * This may be called from any context to trigger a system shutdown.
437  * If the orderly shutdown fails, it will force an immediate shutdown.
438  */
orderly_poweroff(bool force)439 int orderly_poweroff(bool force)
440 {
441 	if (force) /* do not override the pending "true" */
442 		poweroff_force = true;
443 	schedule_work(&poweroff_work);
444 	return 0;
445 }
446 EXPORT_SYMBOL_GPL(orderly_poweroff);
447 
reboot_setup(char * str)448 static int __init reboot_setup(char *str)
449 {
450 	for (;;) {
451 		/*
452 		 * Having anything passed on the command line via
453 		 * reboot= will cause us to disable DMI checking
454 		 * below.
455 		 */
456 		reboot_default = 0;
457 
458 		switch (*str) {
459 		case 'w':
460 			reboot_mode = REBOOT_WARM;
461 			break;
462 
463 		case 'c':
464 			reboot_mode = REBOOT_COLD;
465 			break;
466 
467 		case 'h':
468 			reboot_mode = REBOOT_HARD;
469 			break;
470 
471 		case 's':
472 		{
473 			int rc;
474 
475 			if (isdigit(*(str+1))) {
476 				rc = kstrtoint(str+1, 0, &reboot_cpu);
477 				if (rc)
478 					return rc;
479 			} else if (str[1] == 'm' && str[2] == 'p' &&
480 				   isdigit(*(str+3))) {
481 				rc = kstrtoint(str+3, 0, &reboot_cpu);
482 				if (rc)
483 					return rc;
484 			} else
485 				reboot_mode = REBOOT_SOFT;
486 			break;
487 		}
488 		case 'g':
489 			reboot_mode = REBOOT_GPIO;
490 			break;
491 
492 		case 'b':
493 		case 'a':
494 		case 'k':
495 		case 't':
496 		case 'e':
497 		case 'p':
498 			reboot_type = *str;
499 			break;
500 
501 		case 'f':
502 			reboot_force = 1;
503 			break;
504 		}
505 
506 		str = strchr(str, ',');
507 		if (str)
508 			str++;
509 		else
510 			break;
511 	}
512 	return 1;
513 }
514 __setup("reboot=", reboot_setup);
515