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/ctype.h>
11 #include <linux/export.h>
12 #include <linux/kexec.h>
13 #include <linux/kmod.h>
14 #include <linux/kmsg_dump.h>
15 #include <linux/reboot.h>
16 #include <linux/suspend.h>
17 #include <linux/syscalls.h>
18 #include <linux/syscore_ops.h>
19 #include <linux/uaccess.h>
20
21 /*
22 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
23 */
24
25 int C_A_D = 1;
26 struct pid *cad_pid;
27 EXPORT_SYMBOL(cad_pid);
28
29 #if defined(CONFIG_ARM) || defined(CONFIG_UNICORE32)
30 #define DEFAULT_REBOOT_MODE = REBOOT_HARD
31 #else
32 #define DEFAULT_REBOOT_MODE
33 #endif
34 enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
35 EXPORT_SYMBOL_GPL(reboot_mode);
36 enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
37 EXPORT_SYMBOL_GPL(panic_reboot_mode);
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 */
46 int reboot_default = 1;
47 int reboot_cpu;
48 enum reboot_type reboot_type = BOOT_ACPI;
49 int reboot_force;
50
51 /*
52 * If set, this is used for preparing the system to power off.
53 */
54
55 void (*pm_power_off_prepare)(void);
56 EXPORT_SYMBOL_GPL(pm_power_off_prepare);
57
58 /**
59 * emergency_restart - reboot the system
60 *
61 * Without shutting down any hardware or taking any locks
62 * reboot the system. This is called when we know we are in
63 * trouble so this is our best effort to reboot. This is
64 * safe to call in interrupt context.
65 */
emergency_restart(void)66 void emergency_restart(void)
67 {
68 kmsg_dump(KMSG_DUMP_EMERG);
69 machine_emergency_restart();
70 }
71 EXPORT_SYMBOL_GPL(emergency_restart);
72
kernel_restart_prepare(char * cmd)73 void kernel_restart_prepare(char *cmd)
74 {
75 blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
76 system_state = SYSTEM_RESTART;
77 usermodehelper_disable();
78 device_shutdown();
79 }
80
81 /**
82 * register_reboot_notifier - Register function to be called at reboot time
83 * @nb: Info about notifier function to be called
84 *
85 * Registers a function with the list of functions
86 * to be called at reboot time.
87 *
88 * Currently always returns zero, as blocking_notifier_chain_register()
89 * always returns zero.
90 */
register_reboot_notifier(struct notifier_block * nb)91 int register_reboot_notifier(struct notifier_block *nb)
92 {
93 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
94 }
95 EXPORT_SYMBOL(register_reboot_notifier);
96
97 /**
98 * unregister_reboot_notifier - Unregister previously registered reboot notifier
99 * @nb: Hook to be unregistered
100 *
101 * Unregisters a previously registered reboot
102 * notifier function.
103 *
104 * Returns zero on success, or %-ENOENT on failure.
105 */
unregister_reboot_notifier(struct notifier_block * nb)106 int unregister_reboot_notifier(struct notifier_block *nb)
107 {
108 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
109 }
110 EXPORT_SYMBOL(unregister_reboot_notifier);
111
devm_unregister_reboot_notifier(struct device * dev,void * res)112 static void devm_unregister_reboot_notifier(struct device *dev, void *res)
113 {
114 WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
115 }
116
devm_register_reboot_notifier(struct device * dev,struct notifier_block * nb)117 int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
118 {
119 struct notifier_block **rcnb;
120 int ret;
121
122 rcnb = devres_alloc(devm_unregister_reboot_notifier,
123 sizeof(*rcnb), GFP_KERNEL);
124 if (!rcnb)
125 return -ENOMEM;
126
127 ret = register_reboot_notifier(nb);
128 if (!ret) {
129 *rcnb = nb;
130 devres_add(dev, rcnb);
131 } else {
132 devres_free(rcnb);
133 }
134
135 return ret;
136 }
137 EXPORT_SYMBOL(devm_register_reboot_notifier);
138
139 /*
140 * Notifier list for kernel code which wants to be called
141 * to restart the system.
142 */
143 static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
144
145 /**
146 * register_restart_handler - Register function to be called to reset
147 * the system
148 * @nb: Info about handler function to be called
149 * @nb->priority: Handler priority. Handlers should follow the
150 * following guidelines for setting priorities.
151 * 0: Restart handler of last resort,
152 * with limited restart capabilities
153 * 128: Default restart handler; use if no other
154 * restart handler is expected to be available,
155 * and/or if restart functionality is
156 * sufficient to restart the entire system
157 * 255: Highest priority restart handler, will
158 * preempt all other restart handlers
159 *
160 * Registers a function with code to be called to restart the
161 * system.
162 *
163 * Registered functions will be called from machine_restart as last
164 * step of the restart sequence (if the architecture specific
165 * machine_restart function calls do_kernel_restart - see below
166 * for details).
167 * Registered functions are expected to restart the system immediately.
168 * If more than one function is registered, the restart handler priority
169 * selects which function will be called first.
170 *
171 * Restart handlers are expected to be registered from non-architecture
172 * code, typically from drivers. A typical use case would be a system
173 * where restart functionality is provided through a watchdog. Multiple
174 * restart handlers may exist; for example, one restart handler might
175 * restart the entire system, while another only restarts the CPU.
176 * In such cases, the restart handler which only restarts part of the
177 * hardware is expected to register with low priority to ensure that
178 * it only runs if no other means to restart the system is available.
179 *
180 * Currently always returns zero, as atomic_notifier_chain_register()
181 * always returns zero.
182 */
register_restart_handler(struct notifier_block * nb)183 int register_restart_handler(struct notifier_block *nb)
184 {
185 return atomic_notifier_chain_register(&restart_handler_list, nb);
186 }
187 EXPORT_SYMBOL(register_restart_handler);
188
189 /**
190 * unregister_restart_handler - Unregister previously registered
191 * restart handler
192 * @nb: Hook to be unregistered
193 *
194 * Unregisters a previously registered restart handler function.
195 *
196 * Returns zero on success, or %-ENOENT on failure.
197 */
unregister_restart_handler(struct notifier_block * nb)198 int unregister_restart_handler(struct notifier_block *nb)
199 {
200 return atomic_notifier_chain_unregister(&restart_handler_list, nb);
201 }
202 EXPORT_SYMBOL(unregister_restart_handler);
203
204 /**
205 * do_kernel_restart - Execute kernel restart handler call chain
206 *
207 * Calls functions registered with register_restart_handler.
208 *
209 * Expected to be called from machine_restart as last step of the restart
210 * sequence.
211 *
212 * Restarts the system immediately if a restart handler function has been
213 * registered. Otherwise does nothing.
214 */
do_kernel_restart(char * cmd)215 void do_kernel_restart(char *cmd)
216 {
217 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
218 }
219
migrate_to_reboot_cpu(void)220 void migrate_to_reboot_cpu(void)
221 {
222 /* The boot cpu is always logical cpu 0 */
223 int cpu = reboot_cpu;
224
225 cpu_hotplug_disable();
226
227 /* Make certain the cpu I'm about to reboot on is online */
228 if (!cpu_online(cpu))
229 cpu = cpumask_first(cpu_online_mask);
230
231 /* Prevent races with other tasks migrating this task */
232 current->flags |= PF_NO_SETAFFINITY;
233
234 /* Make certain I only run on the appropriate processor */
235 set_cpus_allowed_ptr(current, cpumask_of(cpu));
236 }
237
238 /**
239 * kernel_restart - reboot the system
240 * @cmd: pointer to buffer containing command to execute for restart
241 * or %NULL
242 *
243 * Shutdown everything and perform a clean reboot.
244 * This is not safe to call in interrupt context.
245 */
kernel_restart(char * cmd)246 void kernel_restart(char *cmd)
247 {
248 kernel_restart_prepare(cmd);
249 migrate_to_reboot_cpu();
250 syscore_shutdown();
251 if (!cmd)
252 pr_emerg("Restarting system\n");
253 else
254 pr_emerg("Restarting system with command '%s'\n", cmd);
255 kmsg_dump(KMSG_DUMP_RESTART);
256 machine_restart(cmd);
257 }
258 EXPORT_SYMBOL_GPL(kernel_restart);
259
kernel_shutdown_prepare(enum system_states state)260 static void kernel_shutdown_prepare(enum system_states state)
261 {
262 blocking_notifier_call_chain(&reboot_notifier_list,
263 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
264 system_state = state;
265 usermodehelper_disable();
266 device_shutdown();
267 }
268 /**
269 * kernel_halt - halt the system
270 *
271 * Shutdown everything and perform a clean system halt.
272 */
kernel_halt(void)273 void kernel_halt(void)
274 {
275 kernel_shutdown_prepare(SYSTEM_HALT);
276 migrate_to_reboot_cpu();
277 syscore_shutdown();
278 pr_emerg("System halted\n");
279 kmsg_dump(KMSG_DUMP_HALT);
280 machine_halt();
281 }
282 EXPORT_SYMBOL_GPL(kernel_halt);
283
284 /**
285 * kernel_power_off - power_off the system
286 *
287 * Shutdown everything and perform a clean system power_off.
288 */
kernel_power_off(void)289 void kernel_power_off(void)
290 {
291 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
292 if (pm_power_off_prepare)
293 pm_power_off_prepare();
294 migrate_to_reboot_cpu();
295 syscore_shutdown();
296 pr_emerg("Power down\n");
297 kmsg_dump(KMSG_DUMP_POWEROFF);
298 machine_power_off();
299 }
300 EXPORT_SYMBOL_GPL(kernel_power_off);
301
302 DEFINE_MUTEX(system_transition_mutex);
303
304 /*
305 * Reboot system call: for obvious reasons only root may call it,
306 * and even root needs to set up some magic numbers in the registers
307 * so that some mistake won't make this reboot the whole machine.
308 * You can also set the meaning of the ctrl-alt-del-key here.
309 *
310 * reboot doesn't sync: do that yourself before calling this.
311 */
SYSCALL_DEFINE4(reboot,int,magic1,int,magic2,unsigned int,cmd,void __user *,arg)312 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
313 void __user *, arg)
314 {
315 struct pid_namespace *pid_ns = task_active_pid_ns(current);
316 char buffer[256];
317 int ret = 0;
318
319 /* We only trust the superuser with rebooting the system. */
320 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
321 return -EPERM;
322
323 /* For safety, we require "magic" arguments. */
324 if (magic1 != LINUX_REBOOT_MAGIC1 ||
325 (magic2 != LINUX_REBOOT_MAGIC2 &&
326 magic2 != LINUX_REBOOT_MAGIC2A &&
327 magic2 != LINUX_REBOOT_MAGIC2B &&
328 magic2 != LINUX_REBOOT_MAGIC2C))
329 return -EINVAL;
330
331 /*
332 * If pid namespaces are enabled and the current task is in a child
333 * pid_namespace, the command is handled by reboot_pid_ns() which will
334 * call do_exit().
335 */
336 ret = reboot_pid_ns(pid_ns, cmd);
337 if (ret)
338 return ret;
339
340 /* Instead of trying to make the power_off code look like
341 * halt when pm_power_off is not set do it the easy way.
342 */
343 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
344 cmd = LINUX_REBOOT_CMD_HALT;
345
346 mutex_lock(&system_transition_mutex);
347 switch (cmd) {
348 case LINUX_REBOOT_CMD_RESTART:
349 kernel_restart(NULL);
350 break;
351
352 case LINUX_REBOOT_CMD_CAD_ON:
353 C_A_D = 1;
354 break;
355
356 case LINUX_REBOOT_CMD_CAD_OFF:
357 C_A_D = 0;
358 break;
359
360 case LINUX_REBOOT_CMD_HALT:
361 kernel_halt();
362 do_exit(0);
363 panic("cannot halt");
364
365 case LINUX_REBOOT_CMD_POWER_OFF:
366 kernel_power_off();
367 do_exit(0);
368 break;
369
370 case LINUX_REBOOT_CMD_RESTART2:
371 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
372 if (ret < 0) {
373 ret = -EFAULT;
374 break;
375 }
376 buffer[sizeof(buffer) - 1] = '\0';
377
378 kernel_restart(buffer);
379 break;
380
381 #ifdef CONFIG_KEXEC_CORE
382 case LINUX_REBOOT_CMD_KEXEC:
383 ret = kernel_kexec();
384 break;
385 #endif
386
387 #ifdef CONFIG_HIBERNATION
388 case LINUX_REBOOT_CMD_SW_SUSPEND:
389 ret = hibernate();
390 break;
391 #endif
392
393 default:
394 ret = -EINVAL;
395 break;
396 }
397 mutex_unlock(&system_transition_mutex);
398 return ret;
399 }
400
deferred_cad(struct work_struct * dummy)401 static void deferred_cad(struct work_struct *dummy)
402 {
403 kernel_restart(NULL);
404 }
405
406 /*
407 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
408 * As it's called within an interrupt, it may NOT sync: the only choice
409 * is whether to reboot at once, or just ignore the ctrl-alt-del.
410 */
ctrl_alt_del(void)411 void ctrl_alt_del(void)
412 {
413 static DECLARE_WORK(cad_work, deferred_cad);
414
415 if (C_A_D)
416 schedule_work(&cad_work);
417 else
418 kill_cad_pid(SIGINT, 1);
419 }
420
421 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
422 static const char reboot_cmd[] = "/sbin/reboot";
423
run_cmd(const char * cmd)424 static int run_cmd(const char *cmd)
425 {
426 char **argv;
427 static char *envp[] = {
428 "HOME=/",
429 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
430 NULL
431 };
432 int ret;
433 argv = argv_split(GFP_KERNEL, cmd, NULL);
434 if (argv) {
435 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
436 argv_free(argv);
437 } else {
438 ret = -ENOMEM;
439 }
440
441 return ret;
442 }
443
__orderly_reboot(void)444 static int __orderly_reboot(void)
445 {
446 int ret;
447
448 ret = run_cmd(reboot_cmd);
449
450 if (ret) {
451 pr_warn("Failed to start orderly reboot: forcing the issue\n");
452 emergency_sync();
453 kernel_restart(NULL);
454 }
455
456 return ret;
457 }
458
__orderly_poweroff(bool force)459 static int __orderly_poweroff(bool force)
460 {
461 int ret;
462
463 ret = run_cmd(poweroff_cmd);
464
465 if (ret && force) {
466 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
467
468 /*
469 * I guess this should try to kick off some daemon to sync and
470 * poweroff asap. Or not even bother syncing if we're doing an
471 * emergency shutdown?
472 */
473 emergency_sync();
474 kernel_power_off();
475 }
476
477 return ret;
478 }
479
480 static bool poweroff_force;
481
poweroff_work_func(struct work_struct * work)482 static void poweroff_work_func(struct work_struct *work)
483 {
484 __orderly_poweroff(poweroff_force);
485 }
486
487 static DECLARE_WORK(poweroff_work, poweroff_work_func);
488
489 /**
490 * orderly_poweroff - Trigger an orderly system poweroff
491 * @force: force poweroff if command execution fails
492 *
493 * This may be called from any context to trigger a system shutdown.
494 * If the orderly shutdown fails, it will force an immediate shutdown.
495 */
orderly_poweroff(bool force)496 void orderly_poweroff(bool force)
497 {
498 if (force) /* do not override the pending "true" */
499 poweroff_force = true;
500 schedule_work(&poweroff_work);
501 }
502 EXPORT_SYMBOL_GPL(orderly_poweroff);
503
reboot_work_func(struct work_struct * work)504 static void reboot_work_func(struct work_struct *work)
505 {
506 __orderly_reboot();
507 }
508
509 static DECLARE_WORK(reboot_work, reboot_work_func);
510
511 /**
512 * orderly_reboot - Trigger an orderly system reboot
513 *
514 * This may be called from any context to trigger a system reboot.
515 * If the orderly reboot fails, it will force an immediate reboot.
516 */
orderly_reboot(void)517 void orderly_reboot(void)
518 {
519 schedule_work(&reboot_work);
520 }
521 EXPORT_SYMBOL_GPL(orderly_reboot);
522
reboot_setup(char * str)523 static int __init reboot_setup(char *str)
524 {
525 for (;;) {
526 enum reboot_mode *mode;
527
528 /*
529 * Having anything passed on the command line via
530 * reboot= will cause us to disable DMI checking
531 * below.
532 */
533 reboot_default = 0;
534
535 if (!strncmp(str, "panic_", 6)) {
536 mode = &panic_reboot_mode;
537 str += 6;
538 } else {
539 mode = &reboot_mode;
540 }
541
542 switch (*str) {
543 case 'w':
544 *mode = REBOOT_WARM;
545 break;
546
547 case 'c':
548 *mode = REBOOT_COLD;
549 break;
550
551 case 'h':
552 *mode = REBOOT_HARD;
553 break;
554
555 case 's':
556 {
557 int rc;
558
559 if (isdigit(*(str+1))) {
560 rc = kstrtoint(str+1, 0, &reboot_cpu);
561 if (rc)
562 return rc;
563 } else if (str[1] == 'm' && str[2] == 'p' &&
564 isdigit(*(str+3))) {
565 rc = kstrtoint(str+3, 0, &reboot_cpu);
566 if (rc)
567 return rc;
568 } else
569 *mode = REBOOT_SOFT;
570 break;
571 }
572 case 'g':
573 *mode = REBOOT_GPIO;
574 break;
575
576 case 'b':
577 case 'a':
578 case 'k':
579 case 't':
580 case 'e':
581 case 'p':
582 reboot_type = *str;
583 break;
584
585 case 'f':
586 reboot_force = 1;
587 break;
588 }
589
590 str = strchr(str, ',');
591 if (str)
592 str++;
593 else
594 break;
595 }
596 return 1;
597 }
598 __setup("reboot=", reboot_setup);
599