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)
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
220 #ifdef CONFIG_NO_GKI
221 static ATOMIC_NOTIFIER_HEAD(pre_restart_handler_list);
222
register_pre_restart_handler(struct notifier_block * nb)223 int register_pre_restart_handler(struct notifier_block *nb)
224 {
225 return atomic_notifier_chain_register(&pre_restart_handler_list, nb);
226 }
227 EXPORT_SYMBOL(register_pre_restart_handler);
228
unregister_pre_restart_handler(struct notifier_block * nb)229 int unregister_pre_restart_handler(struct notifier_block *nb)
230 {
231 return atomic_notifier_chain_unregister(&pre_restart_handler_list, nb);
232 }
233 EXPORT_SYMBOL(unregister_pre_restart_handler);
234
do_kernel_pre_restart(char * cmd)235 void do_kernel_pre_restart(char *cmd)
236 {
237 atomic_notifier_call_chain(&pre_restart_handler_list, reboot_mode, cmd);
238 }
239 #endif
240
migrate_to_reboot_cpu(void)241 void migrate_to_reboot_cpu(void)
242 {
243 /* The boot cpu is always logical cpu 0 */
244 int cpu = reboot_cpu;
245
246 cpu_hotplug_disable();
247
248 /* Make certain the cpu I'm about to reboot on is online */
249 if (!cpu_online(cpu))
250 cpu = cpumask_first(cpu_online_mask);
251
252 /* Prevent races with other tasks migrating this task */
253 current->flags |= PF_NO_SETAFFINITY;
254
255 /* Make certain I only run on the appropriate processor */
256 set_cpus_allowed_ptr(current, cpumask_of(cpu));
257 }
258
259 /**
260 * kernel_restart - reboot the system
261 * @cmd: pointer to buffer containing command to execute for restart
262 * or %NULL
263 *
264 * Shutdown everything and perform a clean reboot.
265 * This is not safe to call in interrupt context.
266 */
kernel_restart(char * cmd)267 void kernel_restart(char *cmd)
268 {
269 kernel_restart_prepare(cmd);
270 migrate_to_reboot_cpu();
271 syscore_shutdown();
272 if (!cmd)
273 pr_emerg("Restarting system\n");
274 else
275 pr_emerg("Restarting system with command '%s'\n", cmd);
276 kmsg_dump(KMSG_DUMP_SHUTDOWN);
277 machine_restart(cmd);
278 }
279 EXPORT_SYMBOL_GPL(kernel_restart);
280
kernel_shutdown_prepare(enum system_states state)281 static void kernel_shutdown_prepare(enum system_states state)
282 {
283 blocking_notifier_call_chain(&reboot_notifier_list,
284 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
285 system_state = state;
286 usermodehelper_disable();
287 device_shutdown();
288 }
289 /**
290 * kernel_halt - halt the system
291 *
292 * Shutdown everything and perform a clean system halt.
293 */
kernel_halt(void)294 void kernel_halt(void)
295 {
296 kernel_shutdown_prepare(SYSTEM_HALT);
297 migrate_to_reboot_cpu();
298 syscore_shutdown();
299 pr_emerg("System halted\n");
300 kmsg_dump(KMSG_DUMP_SHUTDOWN);
301 machine_halt();
302 }
303 EXPORT_SYMBOL_GPL(kernel_halt);
304
305 /**
306 * kernel_power_off - power_off the system
307 *
308 * Shutdown everything and perform a clean system power_off.
309 */
kernel_power_off(void)310 void kernel_power_off(void)
311 {
312 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
313 if (pm_power_off_prepare)
314 pm_power_off_prepare();
315 migrate_to_reboot_cpu();
316 syscore_shutdown();
317 pr_emerg("Power down\n");
318 kmsg_dump(KMSG_DUMP_SHUTDOWN);
319 machine_power_off();
320 }
321 EXPORT_SYMBOL_GPL(kernel_power_off);
322
323 DEFINE_MUTEX(system_transition_mutex);
324
325 /*
326 * Reboot system call: for obvious reasons only root may call it,
327 * and even root needs to set up some magic numbers in the registers
328 * so that some mistake won't make this reboot the whole machine.
329 * You can also set the meaning of the ctrl-alt-del-key here.
330 *
331 * reboot doesn't sync: do that yourself before calling this.
332 */
SYSCALL_DEFINE4(reboot,int,magic1,int,magic2,unsigned int,cmd,void __user *,arg)333 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
334 void __user *, arg)
335 {
336 struct pid_namespace *pid_ns = task_active_pid_ns(current);
337 char buffer[256];
338 int ret = 0;
339
340 /* We only trust the superuser with rebooting the system. */
341 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
342 return -EPERM;
343
344 /* For safety, we require "magic" arguments. */
345 if (magic1 != LINUX_REBOOT_MAGIC1 ||
346 (magic2 != LINUX_REBOOT_MAGIC2 &&
347 magic2 != LINUX_REBOOT_MAGIC2A &&
348 magic2 != LINUX_REBOOT_MAGIC2B &&
349 magic2 != LINUX_REBOOT_MAGIC2C))
350 return -EINVAL;
351
352 /*
353 * If pid namespaces are enabled and the current task is in a child
354 * pid_namespace, the command is handled by reboot_pid_ns() which will
355 * call do_exit().
356 */
357 ret = reboot_pid_ns(pid_ns, cmd);
358 if (ret)
359 return ret;
360
361 /* Instead of trying to make the power_off code look like
362 * halt when pm_power_off is not set do it the easy way.
363 */
364 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
365 cmd = LINUX_REBOOT_CMD_HALT;
366
367 mutex_lock(&system_transition_mutex);
368 switch (cmd) {
369 case LINUX_REBOOT_CMD_RESTART:
370 kernel_restart(NULL);
371 break;
372
373 case LINUX_REBOOT_CMD_CAD_ON:
374 C_A_D = 1;
375 break;
376
377 case LINUX_REBOOT_CMD_CAD_OFF:
378 C_A_D = 0;
379 break;
380
381 case LINUX_REBOOT_CMD_HALT:
382 kernel_halt();
383 do_exit(0);
384 panic("cannot halt");
385
386 case LINUX_REBOOT_CMD_POWER_OFF:
387 kernel_power_off();
388 do_exit(0);
389 break;
390
391 case LINUX_REBOOT_CMD_RESTART2:
392 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
393 if (ret < 0) {
394 ret = -EFAULT;
395 break;
396 }
397 buffer[sizeof(buffer) - 1] = '\0';
398
399 kernel_restart(buffer);
400 break;
401
402 #ifdef CONFIG_KEXEC_CORE
403 case LINUX_REBOOT_CMD_KEXEC:
404 ret = kernel_kexec();
405 break;
406 #endif
407
408 #ifdef CONFIG_HIBERNATION
409 case LINUX_REBOOT_CMD_SW_SUSPEND:
410 ret = hibernate();
411 break;
412 #endif
413
414 default:
415 ret = -EINVAL;
416 break;
417 }
418 mutex_unlock(&system_transition_mutex);
419 return ret;
420 }
421
deferred_cad(struct work_struct * dummy)422 static void deferred_cad(struct work_struct *dummy)
423 {
424 kernel_restart(NULL);
425 }
426
427 /*
428 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
429 * As it's called within an interrupt, it may NOT sync: the only choice
430 * is whether to reboot at once, or just ignore the ctrl-alt-del.
431 */
ctrl_alt_del(void)432 void ctrl_alt_del(void)
433 {
434 static DECLARE_WORK(cad_work, deferred_cad);
435
436 if (C_A_D)
437 schedule_work(&cad_work);
438 else
439 kill_cad_pid(SIGINT, 1);
440 }
441
442 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
443 static const char reboot_cmd[] = "/sbin/reboot";
444
run_cmd(const char * cmd)445 static int run_cmd(const char *cmd)
446 {
447 char **argv;
448 static char *envp[] = {
449 "HOME=/",
450 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
451 NULL
452 };
453 int ret;
454 argv = argv_split(GFP_KERNEL, cmd, NULL);
455 if (argv) {
456 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
457 argv_free(argv);
458 } else {
459 ret = -ENOMEM;
460 }
461
462 return ret;
463 }
464
__orderly_reboot(void)465 static int __orderly_reboot(void)
466 {
467 int ret;
468
469 ret = run_cmd(reboot_cmd);
470
471 if (ret) {
472 pr_warn("Failed to start orderly reboot: forcing the issue\n");
473 emergency_sync();
474 kernel_restart(NULL);
475 }
476
477 return ret;
478 }
479
__orderly_poweroff(bool force)480 static int __orderly_poweroff(bool force)
481 {
482 int ret;
483
484 ret = run_cmd(poweroff_cmd);
485
486 if (ret && force) {
487 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
488
489 /*
490 * I guess this should try to kick off some daemon to sync and
491 * poweroff asap. Or not even bother syncing if we're doing an
492 * emergency shutdown?
493 */
494 emergency_sync();
495 kernel_power_off();
496 }
497
498 return ret;
499 }
500
501 static bool poweroff_force;
502
poweroff_work_func(struct work_struct * work)503 static void poweroff_work_func(struct work_struct *work)
504 {
505 __orderly_poweroff(poweroff_force);
506 }
507
508 static DECLARE_WORK(poweroff_work, poweroff_work_func);
509
510 /**
511 * orderly_poweroff - Trigger an orderly system poweroff
512 * @force: force poweroff if command execution fails
513 *
514 * This may be called from any context to trigger a system shutdown.
515 * If the orderly shutdown fails, it will force an immediate shutdown.
516 */
orderly_poweroff(bool force)517 void orderly_poweroff(bool force)
518 {
519 if (force) /* do not override the pending "true" */
520 poweroff_force = true;
521 schedule_work(&poweroff_work);
522 }
523 EXPORT_SYMBOL_GPL(orderly_poweroff);
524
reboot_work_func(struct work_struct * work)525 static void reboot_work_func(struct work_struct *work)
526 {
527 __orderly_reboot();
528 }
529
530 static DECLARE_WORK(reboot_work, reboot_work_func);
531
532 /**
533 * orderly_reboot - Trigger an orderly system reboot
534 *
535 * This may be called from any context to trigger a system reboot.
536 * If the orderly reboot fails, it will force an immediate reboot.
537 */
orderly_reboot(void)538 void orderly_reboot(void)
539 {
540 schedule_work(&reboot_work);
541 }
542 EXPORT_SYMBOL_GPL(orderly_reboot);
543
reboot_setup(char * str)544 static int __init reboot_setup(char *str)
545 {
546 for (;;) {
547 enum reboot_mode *mode;
548
549 /*
550 * Having anything passed on the command line via
551 * reboot= will cause us to disable DMI checking
552 * below.
553 */
554 reboot_default = 0;
555
556 if (!strncmp(str, "panic_", 6)) {
557 mode = &panic_reboot_mode;
558 str += 6;
559 } else {
560 mode = &reboot_mode;
561 }
562
563 switch (*str) {
564 case 'w':
565 *mode = REBOOT_WARM;
566 break;
567
568 case 'c':
569 *mode = REBOOT_COLD;
570 break;
571
572 case 'h':
573 *mode = REBOOT_HARD;
574 break;
575
576 case 's':
577 if (isdigit(*(str+1)))
578 reboot_cpu = simple_strtoul(str+1, NULL, 0);
579 else if (str[1] == 'm' && str[2] == 'p' &&
580 isdigit(*(str+3)))
581 reboot_cpu = simple_strtoul(str+3, NULL, 0);
582 else
583 *mode = REBOOT_SOFT;
584 if (reboot_cpu >= num_possible_cpus()) {
585 pr_err("Ignoring the CPU number in reboot= option. "
586 "CPU %d exceeds possible cpu number %d\n",
587 reboot_cpu, num_possible_cpus());
588 reboot_cpu = 0;
589 break;
590 }
591 break;
592
593 case 'g':
594 *mode = REBOOT_GPIO;
595 break;
596
597 case 'b':
598 case 'a':
599 case 'k':
600 case 't':
601 case 'e':
602 case 'p':
603 reboot_type = *str;
604 break;
605
606 case 'f':
607 reboot_force = 1;
608 break;
609 }
610
611 str = strchr(str, ',');
612 if (str)
613 str++;
614 else
615 break;
616 }
617 return 1;
618 }
619 __setup("reboot=", reboot_setup);
620