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);
52EXPORT_SYMBOL_GPL(pm_power_off_prepare);
53
54/**
55 * emergency_restart - reboot the system
56 *
57 * Without shutting down any hardware or taking any locks
58 * reboot the system. This is called when we know we are in
59 * trouble so this is our best effort to reboot. This is
60 * safe to call in interrupt context.
61 */
62void emergency_restart(void)
63{
64 kmsg_dump(KMSG_DUMP_EMERG);
65 machine_emergency_restart();
66}
67EXPORT_SYMBOL_GPL(emergency_restart);
68
69void kernel_restart_prepare(char *cmd)
70{
71 blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
72 system_state = SYSTEM_RESTART;
73 usermodehelper_disable();
74 device_shutdown();
75}
76
77/**
78 * register_reboot_notifier - Register function to be called at reboot time
79 * @nb: Info about notifier function to be called
80 *
81 * Registers a function with the list of functions
82 * to be called at reboot time.
83 *
84 * Currently always returns zero, as blocking_notifier_chain_register()
85 * always returns zero.
86 */
87int register_reboot_notifier(struct notifier_block *nb)
88{
89 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
90}
91EXPORT_SYMBOL(register_reboot_notifier);
92
93/**
94 * unregister_reboot_notifier - Unregister previously registered reboot notifier
95 * @nb: Hook to be unregistered
96 *
97 * Unregisters a previously registered reboot
98 * notifier function.
99 *
100 * Returns zero on success, or %-ENOENT on failure.
101 */
102int unregister_reboot_notifier(struct notifier_block *nb)
103{
104 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
105}
106EXPORT_SYMBOL(unregister_reboot_notifier);
107
108static void devm_unregister_reboot_notifier(struct device *dev, void *res)
109{
110 WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
111}
112
113int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
114{
115 struct notifier_block **rcnb;
116 int ret;
117
118 rcnb = devres_alloc(devm_unregister_reboot_notifier,
119 sizeof(*rcnb), GFP_KERNEL);
120 if (!rcnb)
121 return -ENOMEM;
122
123 ret = register_reboot_notifier(nb);
124 if (!ret) {
125 *rcnb = nb;
126 devres_add(dev, rcnb);
127 } else {
128 devres_free(rcnb);
129 }
130
131 return ret;
132}
133EXPORT_SYMBOL(devm_register_reboot_notifier);
134
135/*
136 * Notifier list for kernel code which wants to be called
137 * to restart the system.
138 */
139static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
140
141/**
142 * register_restart_handler - Register function to be called to reset
143 * the system
144 * @nb: Info about handler function to be called
145 * @nb->priority: Handler priority. Handlers should follow the
146 * following guidelines for setting priorities.
147 * 0: Restart handler of last resort,
148 * with limited restart capabilities
149 * 128: Default restart handler; use if no other
150 * restart handler is expected to be available,
151 * and/or if restart functionality is
152 * sufficient to restart the entire system
153 * 255: Highest priority restart handler, will
154 * preempt all other restart handlers
155 *
156 * Registers a function with code to be called to restart the
157 * system.
158 *
159 * Registered functions will be called from machine_restart as last
160 * step of the restart sequence (if the architecture specific
161 * machine_restart function calls do_kernel_restart - see below
162 * for details).
163 * Registered functions are expected to restart the system immediately.
164 * If more than one function is registered, the restart handler priority
165 * selects which function will be called first.
166 *
167 * Restart handlers are expected to be registered from non-architecture
168 * code, typically from drivers. A typical use case would be a system
169 * where restart functionality is provided through a watchdog. Multiple
170 * restart handlers may exist; for example, one restart handler might
171 * restart the entire system, while another only restarts the CPU.
172 * In such cases, the restart handler which only restarts part of the
173 * hardware is expected to register with low priority to ensure that
174 * it only runs if no other means to restart the system is available.
175 *
176 * Currently always returns zero, as atomic_notifier_chain_register()
177 * always returns zero.
178 */
179int register_restart_handler(struct notifier_block *nb)
180{
181 return atomic_notifier_chain_register(&restart_handler_list, nb);
182}
183EXPORT_SYMBOL(register_restart_handler);
184
185/**
186 * unregister_restart_handler - Unregister previously registered
187 * restart handler
188 * @nb: Hook to be unregistered
189 *
190 * Unregisters a previously registered restart handler function.
191 *
192 * Returns zero on success, or %-ENOENT on failure.
193 */
194int unregister_restart_handler(struct notifier_block *nb)
195{
196 return atomic_notifier_chain_unregister(&restart_handler_list, nb);
197}
198EXPORT_SYMBOL(unregister_restart_handler);
199
200/**
201 * do_kernel_restart - Execute kernel restart handler call chain
202 *
203 * Calls functions registered with register_restart_handler.
204 *
205 * Expected to be called from machine_restart as last step of the restart
206 * sequence.
207 *
208 * Restarts the system immediately if a restart handler function has been
209 * registered. Otherwise does nothing.
210 */
211void do_kernel_restart(char *cmd)
212{
213 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
214}
215
216void migrate_to_reboot_cpu(void)
217{
218 /* The boot cpu is always logical cpu 0 */
219 int cpu = reboot_cpu;
220
221 cpu_hotplug_disable();
222
223 /* Make certain the cpu I'm about to reboot on is online */
224 if (!cpu_online(cpu))
225 cpu = cpumask_first(cpu_online_mask);
226
227 /* Prevent races with other tasks migrating this task */
228 current->flags |= PF_NO_SETAFFINITY;
229
230 /* Make certain I only run on the appropriate processor */
231 set_cpus_allowed_ptr(current, cpumask_of(cpu));
232}
233
234/**
235 * kernel_restart - reboot the system
236 * @cmd: pointer to buffer containing command to execute for restart
237 * or %NULL
238 *
239 * Shutdown everything and perform a clean reboot.
240 * This is not safe to call in interrupt context.
241 */
242void kernel_restart(char *cmd)
243{
244 kernel_restart_prepare(cmd);
245 migrate_to_reboot_cpu();
246 syscore_shutdown();
247 if (!cmd)
248 pr_emerg("Restarting system\n");
249 else
250 pr_emerg("Restarting system with command '%s'\n", cmd);
251 kmsg_dump(KMSG_DUMP_RESTART);
252 machine_restart(cmd);
253}
254EXPORT_SYMBOL_GPL(kernel_restart);
255
256static void kernel_shutdown_prepare(enum system_states state)
257{
258 blocking_notifier_call_chain(&reboot_notifier_list,
259 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
260 system_state = state;
261 usermodehelper_disable();
262 device_shutdown();
263}
264/**
265 * kernel_halt - halt the system
266 *
267 * Shutdown everything and perform a clean system halt.
268 */
269void kernel_halt(void)
270{
271 kernel_shutdown_prepare(SYSTEM_HALT);
272 migrate_to_reboot_cpu();
273 syscore_shutdown();
274 pr_emerg("System halted\n");
275 kmsg_dump(KMSG_DUMP_HALT);
276 machine_halt();
277}
278EXPORT_SYMBOL_GPL(kernel_halt);
279
280/**
281 * kernel_power_off - power_off the system
282 *
283 * Shutdown everything and perform a clean system power_off.
284 */
285void kernel_power_off(void)
286{
287 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
288 if (pm_power_off_prepare)
289 pm_power_off_prepare();
290 migrate_to_reboot_cpu();
291 syscore_shutdown();
292 pr_emerg("Power down\n");
293 kmsg_dump(KMSG_DUMP_POWEROFF);
294 machine_power_off();
295}
296EXPORT_SYMBOL_GPL(kernel_power_off);
297
298DEFINE_MUTEX(system_transition_mutex);
299
300/*
301 * Reboot system call: for obvious reasons only root may call it,
302 * and even root needs to set up some magic numbers in the registers
303 * so that some mistake won't make this reboot the whole machine.
304 * You can also set the meaning of the ctrl-alt-del-key here.
305 *
306 * reboot doesn't sync: do that yourself before calling this.
307 */
308SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
309 void __user *, arg)
310{
311 struct pid_namespace *pid_ns = task_active_pid_ns(current);
312 char buffer[256];
313 int ret = 0;
314
315 /* We only trust the superuser with rebooting the system. */
316 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
317 return -EPERM;
318
319 /* For safety, we require "magic" arguments. */
320 if (magic1 != LINUX_REBOOT_MAGIC1 ||
321 (magic2 != LINUX_REBOOT_MAGIC2 &&
322 magic2 != LINUX_REBOOT_MAGIC2A &&
323 magic2 != LINUX_REBOOT_MAGIC2B &&
324 magic2 != LINUX_REBOOT_MAGIC2C))
325 return -EINVAL;
326
327 /*
328 * If pid namespaces are enabled and the current task is in a child
329 * pid_namespace, the command is handled by reboot_pid_ns() which will
330 * call do_exit().
331 */
332 ret = reboot_pid_ns(pid_ns, cmd);
333 if (ret)
334 return ret;
335
336 /* Instead of trying to make the power_off code look like
337 * halt when pm_power_off is not set do it the easy way.
338 */
339 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
340 cmd = LINUX_REBOOT_CMD_HALT;
341
342 mutex_lock(&system_transition_mutex);
343 switch (cmd) {
344 case LINUX_REBOOT_CMD_RESTART:
345 kernel_restart(NULL);
346 break;
347
348 case LINUX_REBOOT_CMD_CAD_ON:
349 C_A_D = 1;
350 break;
351
352 case LINUX_REBOOT_CMD_CAD_OFF:
353 C_A_D = 0;
354 break;
355
356 case LINUX_REBOOT_CMD_HALT:
357 kernel_halt();
358 do_exit(0);
359 panic("cannot halt");
360
361 case LINUX_REBOOT_CMD_POWER_OFF:
362 kernel_power_off();
363 do_exit(0);
364 break;
365
366 case LINUX_REBOOT_CMD_RESTART2:
367 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
368 if (ret < 0) {
369 ret = -EFAULT;
370 break;
371 }
372 buffer[sizeof(buffer) - 1] = '\0';
373
374 kernel_restart(buffer);
375 break;
376
377#ifdef CONFIG_KEXEC_CORE
378 case LINUX_REBOOT_CMD_KEXEC:
379 ret = kernel_kexec();
380 break;
381#endif
382
383#ifdef CONFIG_HIBERNATION
384 case LINUX_REBOOT_CMD_SW_SUSPEND:
385 ret = hibernate();
386 break;
387#endif
388
389 default:
390 ret = -EINVAL;
391 break;
392 }
393 mutex_unlock(&system_transition_mutex);
394 return ret;
395}
396
397static void deferred_cad(struct work_struct *dummy)
398{
399 kernel_restart(NULL);
400}
401
402/*
403 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
404 * As it's called within an interrupt, it may NOT sync: the only choice
405 * is whether to reboot at once, or just ignore the ctrl-alt-del.
406 */
407void ctrl_alt_del(void)
408{
409 static DECLARE_WORK(cad_work, deferred_cad);
410
411 if (C_A_D)
412 schedule_work(&cad_work);
413 else
414 kill_cad_pid(SIGINT, 1);
415}
416
417char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
418static const char reboot_cmd[] = "/sbin/reboot";
419
420static int run_cmd(const char *cmd)
421{
422 char **argv;
423 static char *envp[] = {
424 "HOME=/",
425 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
426 NULL
427 };
428 int ret;
429 argv = argv_split(GFP_KERNEL, cmd, NULL);
430 if (argv) {
431 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
432 argv_free(argv);
433 } else {
434 ret = -ENOMEM;
435 }
436
437 return ret;
438}
439
440static int __orderly_reboot(void)
441{
442 int ret;
443
444 ret = run_cmd(reboot_cmd);
445
446 if (ret) {
447 pr_warn("Failed to start orderly reboot: forcing the issue\n");
448 emergency_sync();
449 kernel_restart(NULL);
450 }
451
452 return ret;
453}
454
455static int __orderly_poweroff(bool force)
456{
457 int ret;
458
459 ret = run_cmd(poweroff_cmd);
460
461 if (ret && force) {
462 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
463
464 /*
465 * I guess this should try to kick off some daemon to sync and
466 * poweroff asap. Or not even bother syncing if we're doing an
467 * emergency shutdown?
468 */
469 emergency_sync();
470 kernel_power_off();
471 }
472
473 return ret;
474}
475
476static bool poweroff_force;
477
478static void poweroff_work_func(struct work_struct *work)
479{
480 __orderly_poweroff(poweroff_force);
481}
482
483static DECLARE_WORK(poweroff_work, poweroff_work_func);
484
485/**
486 * orderly_poweroff - Trigger an orderly system poweroff
487 * @force: force poweroff if command execution fails
488 *
489 * This may be called from any context to trigger a system shutdown.
490 * If the orderly shutdown fails, it will force an immediate shutdown.
491 */
492void orderly_poweroff(bool force)
493{
494 if (force) /* do not override the pending "true" */
495 poweroff_force = true;
496 schedule_work(&poweroff_work);
497}
498EXPORT_SYMBOL_GPL(orderly_poweroff);
499
500static void reboot_work_func(struct work_struct *work)
501{
502 __orderly_reboot();
503}
504
505static DECLARE_WORK(reboot_work, reboot_work_func);
506
507/**
508 * orderly_reboot - Trigger an orderly system reboot
509 *
510 * This may be called from any context to trigger a system reboot.
511 * If the orderly reboot fails, it will force an immediate reboot.
512 */
513void orderly_reboot(void)
514{
515 schedule_work(&reboot_work);
516}
517EXPORT_SYMBOL_GPL(orderly_reboot);
518
519static int __init reboot_setup(char *str)
520{
521 for (;;) {
522 /*
523 * Having anything passed on the command line via
524 * reboot= will cause us to disable DMI checking
525 * below.
526 */
527 reboot_default = 0;
528
529 switch (*str) {
530 case 'w':
531 reboot_mode = REBOOT_WARM;
532 break;
533
534 case 'c':
535 reboot_mode = REBOOT_COLD;
536 break;
537
538 case 'h':
539 reboot_mode = REBOOT_HARD;
540 break;
541
542 case 's':
543 {
544 int rc;
545
546 if (isdigit(*(str+1))) {
547 rc = kstrtoint(str+1, 0, &reboot_cpu);
548 if (rc)
549 return rc;
550 } else if (str[1] == 'm' && str[2] == 'p' &&
551 isdigit(*(str+3))) {
552 rc = kstrtoint(str+3, 0, &reboot_cpu);
553 if (rc)
554 return rc;
555 } else
556 reboot_mode = REBOOT_SOFT;
557 break;
558 }
559 case 'g':
560 reboot_mode = REBOOT_GPIO;
561 break;
562
563 case 'b':
564 case 'a':
565 case 'k':
566 case 't':
567 case 'e':
568 case 'p':
569 reboot_type = *str;
570 break;
571
572 case 'f':
573 reboot_force = 1;
574 break;
575 }
576
577 str = strchr(str, ',');
578 if (str)
579 str++;
580 else
581 break;
582 }
583 return 1;
584}
585__setup("reboot=", reboot_setup);
586