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