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 enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
36
37 /*
38 * This variable is used privately to keep track of whether or not
39 * reboot_type is still set to its default value (i.e., reboot= hasn't
40 * been set on the command line). This is needed so that we can
41 * suppress DMI scanning for reboot quirks. Without it, it's
42 * impossible to override a faulty reboot quirk without recompiling.
43 */
44 int reboot_default = 1;
45 int reboot_cpu;
46 enum reboot_type reboot_type = BOOT_ACPI;
47 int reboot_force;
48
49 /*
50 * If set, this is used for preparing the system to power off.
51 */
52
53 void (*pm_power_off_prepare)(void);
54 EXPORT_SYMBOL_GPL(pm_power_off_prepare);
55
56 /**
57 * emergency_restart - reboot the system
58 *
59 * Without shutting down any hardware or taking any locks
60 * reboot the system. This is called when we know we are in
61 * trouble so this is our best effort to reboot. This is
62 * safe to call in interrupt context.
63 */
emergency_restart(void)64 void emergency_restart(void)
65 {
66 kmsg_dump(KMSG_DUMP_EMERG);
67 machine_emergency_restart();
68 }
69 EXPORT_SYMBOL_GPL(emergency_restart);
70
kernel_restart_prepare(char * cmd)71 void kernel_restart_prepare(char *cmd)
72 {
73 blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
74 system_state = SYSTEM_RESTART;
75 usermodehelper_disable();
76 device_shutdown();
77 }
78
79 /**
80 * register_reboot_notifier - Register function to be called at reboot time
81 * @nb: Info about notifier function to be called
82 *
83 * Registers a function with the list of functions
84 * to be called at reboot time.
85 *
86 * Currently always returns zero, as blocking_notifier_chain_register()
87 * always returns zero.
88 */
register_reboot_notifier(struct notifier_block * nb)89 int register_reboot_notifier(struct notifier_block *nb)
90 {
91 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
92 }
93 EXPORT_SYMBOL(register_reboot_notifier);
94
95 /**
96 * unregister_reboot_notifier - Unregister previously registered reboot notifier
97 * @nb: Hook to be unregistered
98 *
99 * Unregisters a previously registered reboot
100 * notifier function.
101 *
102 * Returns zero on success, or %-ENOENT on failure.
103 */
unregister_reboot_notifier(struct notifier_block * nb)104 int unregister_reboot_notifier(struct notifier_block *nb)
105 {
106 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
107 }
108 EXPORT_SYMBOL(unregister_reboot_notifier);
109
devm_unregister_reboot_notifier(struct device * dev,void * res)110 static void devm_unregister_reboot_notifier(struct device *dev, void *res)
111 {
112 WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
113 }
114
devm_register_reboot_notifier(struct device * dev,struct notifier_block * nb)115 int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
116 {
117 struct notifier_block **rcnb;
118 int ret;
119
120 rcnb = devres_alloc(devm_unregister_reboot_notifier,
121 sizeof(*rcnb), GFP_KERNEL);
122 if (!rcnb)
123 return -ENOMEM;
124
125 ret = register_reboot_notifier(nb);
126 if (!ret) {
127 *rcnb = nb;
128 devres_add(dev, rcnb);
129 } else {
130 devres_free(rcnb);
131 }
132
133 return ret;
134 }
135 EXPORT_SYMBOL(devm_register_reboot_notifier);
136
137 /*
138 * Notifier list for kernel code which wants to be called
139 * to restart the system.
140 */
141 static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
142
143 /**
144 * register_restart_handler - Register function to be called to reset
145 * the system
146 * @nb: Info about handler function to be called
147 * @nb->priority: Handler priority. Handlers should follow the
148 * following guidelines for setting priorities.
149 * 0: Restart handler of last resort,
150 * with limited restart capabilities
151 * 128: Default restart handler; use if no other
152 * restart handler is expected to be available,
153 * and/or if restart functionality is
154 * sufficient to restart the entire system
155 * 255: Highest priority restart handler, will
156 * preempt all other restart handlers
157 *
158 * Registers a function with code to be called to restart the
159 * system.
160 *
161 * Registered functions will be called from machine_restart as last
162 * step of the restart sequence (if the architecture specific
163 * machine_restart function calls do_kernel_restart - see below
164 * for details).
165 * Registered functions are expected to restart the system immediately.
166 * If more than one function is registered, the restart handler priority
167 * selects which function will be called first.
168 *
169 * Restart handlers are expected to be registered from non-architecture
170 * code, typically from drivers. A typical use case would be a system
171 * where restart functionality is provided through a watchdog. Multiple
172 * restart handlers may exist; for example, one restart handler might
173 * restart the entire system, while another only restarts the CPU.
174 * In such cases, the restart handler which only restarts part of the
175 * hardware is expected to register with low priority to ensure that
176 * it only runs if no other means to restart the system is available.
177 *
178 * Currently always returns zero, as atomic_notifier_chain_register()
179 * always returns zero.
180 */
register_restart_handler(struct notifier_block * nb)181 int register_restart_handler(struct notifier_block *nb)
182 {
183 return atomic_notifier_chain_register(&restart_handler_list, nb);
184 }
185 EXPORT_SYMBOL(register_restart_handler);
186
187 /**
188 * unregister_restart_handler - Unregister previously registered
189 * restart handler
190 * @nb: Hook to be unregistered
191 *
192 * Unregisters a previously registered restart handler function.
193 *
194 * Returns zero on success, or %-ENOENT on failure.
195 */
unregister_restart_handler(struct notifier_block * nb)196 int unregister_restart_handler(struct notifier_block *nb)
197 {
198 return atomic_notifier_chain_unregister(&restart_handler_list, nb);
199 }
200 EXPORT_SYMBOL(unregister_restart_handler);
201
202 /**
203 * do_kernel_restart - Execute kernel restart handler call chain
204 *
205 * Calls functions registered with register_restart_handler.
206 *
207 * Expected to be called from machine_restart as last step of the restart
208 * sequence.
209 *
210 * Restarts the system immediately if a restart handler function has been
211 * registered. Otherwise does nothing.
212 */
do_kernel_restart(char * cmd)213 void do_kernel_restart(char *cmd)
214 {
215 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
216 }
217
migrate_to_reboot_cpu(void)218 void migrate_to_reboot_cpu(void)
219 {
220 /* The boot cpu is always logical cpu 0 */
221 int cpu = reboot_cpu;
222
223 cpu_hotplug_disable();
224
225 /* Make certain the cpu I'm about to reboot on is online */
226 if (!cpu_online(cpu))
227 cpu = cpumask_first(cpu_online_mask);
228
229 /* Prevent races with other tasks migrating this task */
230 current->flags |= PF_NO_SETAFFINITY;
231
232 /* Make certain I only run on the appropriate processor */
233 set_cpus_allowed_ptr(current, cpumask_of(cpu));
234 }
235
236 /**
237 * kernel_restart - reboot the system
238 * @cmd: pointer to buffer containing command to execute for restart
239 * or %NULL
240 *
241 * Shutdown everything and perform a clean reboot.
242 * This is not safe to call in interrupt context.
243 */
kernel_restart(char * cmd)244 void kernel_restart(char *cmd)
245 {
246 kernel_restart_prepare(cmd);
247 migrate_to_reboot_cpu();
248 syscore_shutdown();
249 if (!cmd)
250 pr_emerg("Restarting system\n");
251 else
252 pr_emerg("Restarting system with command '%s'\n", cmd);
253 kmsg_dump(KMSG_DUMP_SHUTDOWN);
254 machine_restart(cmd);
255 }
256 EXPORT_SYMBOL_GPL(kernel_restart);
257
kernel_shutdown_prepare(enum system_states state)258 static void kernel_shutdown_prepare(enum system_states state)
259 {
260 blocking_notifier_call_chain(&reboot_notifier_list,
261 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
262 system_state = state;
263 usermodehelper_disable();
264 device_shutdown();
265 }
266 /**
267 * kernel_halt - halt the system
268 *
269 * Shutdown everything and perform a clean system halt.
270 */
kernel_halt(void)271 void kernel_halt(void)
272 {
273 kernel_shutdown_prepare(SYSTEM_HALT);
274 migrate_to_reboot_cpu();
275 syscore_shutdown();
276 pr_emerg("System halted\n");
277 kmsg_dump(KMSG_DUMP_SHUTDOWN);
278 machine_halt();
279 }
280 EXPORT_SYMBOL_GPL(kernel_halt);
281
282 /**
283 * kernel_power_off - power_off the system
284 *
285 * Shutdown everything and perform a clean system power_off.
286 */
kernel_power_off(void)287 void kernel_power_off(void)
288 {
289 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
290 if (pm_power_off_prepare)
291 pm_power_off_prepare();
292 migrate_to_reboot_cpu();
293 syscore_shutdown();
294 pr_emerg("Power down\n");
295 kmsg_dump(KMSG_DUMP_SHUTDOWN);
296 machine_power_off();
297 }
298 EXPORT_SYMBOL_GPL(kernel_power_off);
299
300 DEFINE_MUTEX(system_transition_mutex);
301
302 /*
303 * Reboot system call: for obvious reasons only root may call it,
304 * and even root needs to set up some magic numbers in the registers
305 * so that some mistake won't make this reboot the whole machine.
306 * You can also set the meaning of the ctrl-alt-del-key here.
307 *
308 * reboot doesn't sync: do that yourself before calling this.
309 */
SYSCALL_DEFINE4(reboot,int,magic1,int,magic2,unsigned int,cmd,void __user *,arg)310 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
311 void __user *, arg)
312 {
313 struct pid_namespace *pid_ns = task_active_pid_ns(current);
314 char buffer[256];
315 int ret = 0;
316
317 /* We only trust the superuser with rebooting the system. */
318 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
319 return -EPERM;
320
321 /* For safety, we require "magic" arguments. */
322 if (magic1 != LINUX_REBOOT_MAGIC1 ||
323 (magic2 != LINUX_REBOOT_MAGIC2 &&
324 magic2 != LINUX_REBOOT_MAGIC2A &&
325 magic2 != LINUX_REBOOT_MAGIC2B &&
326 magic2 != LINUX_REBOOT_MAGIC2C))
327 return -EINVAL;
328
329 /*
330 * If pid namespaces are enabled and the current task is in a child
331 * pid_namespace, the command is handled by reboot_pid_ns() which will
332 * call do_exit().
333 */
334 ret = reboot_pid_ns(pid_ns, cmd);
335 if (ret)
336 return ret;
337
338 /* Instead of trying to make the power_off code look like
339 * halt when pm_power_off is not set do it the easy way.
340 */
341 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
342 cmd = LINUX_REBOOT_CMD_HALT;
343
344 mutex_lock(&system_transition_mutex);
345 switch (cmd) {
346 case LINUX_REBOOT_CMD_RESTART:
347 kernel_restart(NULL);
348 break;
349
350 case LINUX_REBOOT_CMD_CAD_ON:
351 C_A_D = 1;
352 break;
353
354 case LINUX_REBOOT_CMD_CAD_OFF:
355 C_A_D = 0;
356 break;
357
358 case LINUX_REBOOT_CMD_HALT:
359 kernel_halt();
360 do_exit(0);
361 panic("cannot halt");
362
363 case LINUX_REBOOT_CMD_POWER_OFF:
364 kernel_power_off();
365 do_exit(0);
366 break;
367
368 case LINUX_REBOOT_CMD_RESTART2:
369 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
370 if (ret < 0) {
371 ret = -EFAULT;
372 break;
373 }
374 buffer[sizeof(buffer) - 1] = '\0';
375
376 kernel_restart(buffer);
377 break;
378
379 #ifdef CONFIG_KEXEC_CORE
380 case LINUX_REBOOT_CMD_KEXEC:
381 ret = kernel_kexec();
382 break;
383 #endif
384
385 #ifdef CONFIG_HIBERNATION
386 case LINUX_REBOOT_CMD_SW_SUSPEND:
387 ret = hibernate();
388 break;
389 #endif
390
391 default:
392 ret = -EINVAL;
393 break;
394 }
395 mutex_unlock(&system_transition_mutex);
396 return ret;
397 }
398
deferred_cad(struct work_struct * dummy)399 static void deferred_cad(struct work_struct *dummy)
400 {
401 kernel_restart(NULL);
402 }
403
404 /*
405 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
406 * As it's called within an interrupt, it may NOT sync: the only choice
407 * is whether to reboot at once, or just ignore the ctrl-alt-del.
408 */
ctrl_alt_del(void)409 void ctrl_alt_del(void)
410 {
411 static DECLARE_WORK(cad_work, deferred_cad);
412
413 if (C_A_D)
414 schedule_work(&cad_work);
415 else
416 kill_cad_pid(SIGINT, 1);
417 }
418
419 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
420 static const char reboot_cmd[] = "/sbin/reboot";
421
run_cmd(const char * cmd)422 static int run_cmd(const char *cmd)
423 {
424 char **argv;
425 static char *envp[] = {
426 "HOME=/",
427 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
428 NULL
429 };
430 int ret;
431 argv = argv_split(GFP_KERNEL, cmd, NULL);
432 if (argv) {
433 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
434 argv_free(argv);
435 } else {
436 ret = -ENOMEM;
437 }
438
439 return ret;
440 }
441
__orderly_reboot(void)442 static int __orderly_reboot(void)
443 {
444 int ret;
445
446 ret = run_cmd(reboot_cmd);
447
448 if (ret) {
449 pr_warn("Failed to start orderly reboot: forcing the issue\n");
450 emergency_sync();
451 kernel_restart(NULL);
452 }
453
454 return ret;
455 }
456
__orderly_poweroff(bool force)457 static int __orderly_poweroff(bool force)
458 {
459 int ret;
460
461 ret = run_cmd(poweroff_cmd);
462
463 if (ret && force) {
464 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
465
466 /*
467 * I guess this should try to kick off some daemon to sync and
468 * poweroff asap. Or not even bother syncing if we're doing an
469 * emergency shutdown?
470 */
471 emergency_sync();
472 kernel_power_off();
473 }
474
475 return ret;
476 }
477
478 static bool poweroff_force;
479
poweroff_work_func(struct work_struct * work)480 static void poweroff_work_func(struct work_struct *work)
481 {
482 __orderly_poweroff(poweroff_force);
483 }
484
485 static DECLARE_WORK(poweroff_work, poweroff_work_func);
486
487 /**
488 * orderly_poweroff - Trigger an orderly system poweroff
489 * @force: force poweroff if command execution fails
490 *
491 * This may be called from any context to trigger a system shutdown.
492 * If the orderly shutdown fails, it will force an immediate shutdown.
493 */
orderly_poweroff(bool force)494 void orderly_poweroff(bool force)
495 {
496 if (force) /* do not override the pending "true" */
497 poweroff_force = true;
498 schedule_work(&poweroff_work);
499 }
500 EXPORT_SYMBOL_GPL(orderly_poweroff);
501
reboot_work_func(struct work_struct * work)502 static void reboot_work_func(struct work_struct *work)
503 {
504 __orderly_reboot();
505 }
506
507 static DECLARE_WORK(reboot_work, reboot_work_func);
508
509 /**
510 * orderly_reboot - Trigger an orderly system reboot
511 *
512 * This may be called from any context to trigger a system reboot.
513 * If the orderly reboot fails, it will force an immediate reboot.
514 */
orderly_reboot(void)515 void orderly_reboot(void)
516 {
517 schedule_work(&reboot_work);
518 }
519 EXPORT_SYMBOL_GPL(orderly_reboot);
520
reboot_setup(char * str)521 static int __init reboot_setup(char *str)
522 {
523 for (;;) {
524 enum reboot_mode *mode;
525
526 /*
527 * Having anything passed on the command line via
528 * reboot= will cause us to disable DMI checking
529 * below.
530 */
531 reboot_default = 0;
532
533 if (!strncmp(str, "panic_", 6)) {
534 mode = &panic_reboot_mode;
535 str += 6;
536 } else {
537 mode = &reboot_mode;
538 }
539
540 switch (*str) {
541 case 'w':
542 *mode = REBOOT_WARM;
543 break;
544
545 case 'c':
546 *mode = REBOOT_COLD;
547 break;
548
549 case 'h':
550 *mode = REBOOT_HARD;
551 break;
552
553 case 's':
554 if (isdigit(*(str+1)))
555 reboot_cpu = simple_strtoul(str+1, NULL, 0);
556 else if (str[1] == 'm' && str[2] == 'p' &&
557 isdigit(*(str+3)))
558 reboot_cpu = simple_strtoul(str+3, NULL, 0);
559 else
560 *mode = REBOOT_SOFT;
561 if (reboot_cpu >= num_possible_cpus()) {
562 pr_err("Ignoring the CPU number in reboot= option. "
563 "CPU %d exceeds possible cpu number %d\n",
564 reboot_cpu, num_possible_cpus());
565 reboot_cpu = 0;
566 break;
567 }
568 break;
569
570 case 'g':
571 *mode = REBOOT_GPIO;
572 break;
573
574 case 'b':
575 case 'a':
576 case 'k':
577 case 't':
578 case 'e':
579 case 'p':
580 reboot_type = *str;
581 break;
582
583 case 'f':
584 reboot_force = 1;
585 break;
586 }
587
588 str = strchr(str, ',');
589 if (str)
590 str++;
591 else
592 break;
593 }
594 return 1;
595 }
596 __setup("reboot=", reboot_setup);
597
