1 // SPDX-License-Identifier: GPL-2.0-only
3 * linux/kernel/reboot.c
5 * Copyright (C) 2013 Linus Torvalds
8 #define pr_fmt(fmt) "reboot: " fmt
10 #include <linux/atomic.h>
11 #include <linux/ctype.h>
12 #include <linux/export.h>
13 #include <linux/kexec.h>
14 #include <linux/kmod.h>
15 #include <linux/kmsg_dump.h>
16 #include <linux/reboot.h>
17 #include <linux/suspend.h>
18 #include <linux/syscalls.h>
19 #include <linux/syscore_ops.h>
20 #include <linux/uaccess.h>
23 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
28 EXPORT_SYMBOL(cad_pid);
30 #if defined(CONFIG_ARM)
31 #define DEFAULT_REBOOT_MODE = REBOOT_HARD
33 #define DEFAULT_REBOOT_MODE
35 enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
36 enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
39 * This variable is used privately to keep track of whether or not
40 * reboot_type is still set to its default value (i.e., reboot= hasn't
41 * been set on the command line). This is needed so that we can
42 * suppress DMI scanning for reboot quirks. Without it, it's
43 * impossible to override a faulty reboot quirk without recompiling.
45 int reboot_default = 1;
47 enum reboot_type reboot_type = BOOT_ACPI;
51 * If set, this is used for preparing the system to power off.
54 void (*pm_power_off_prepare)(void);
55 EXPORT_SYMBOL_GPL(pm_power_off_prepare);
58 * emergency_restart - reboot the system
60 * Without shutting down any hardware or taking any locks
61 * reboot the system. This is called when we know we are in
62 * trouble so this is our best effort to reboot. This is
63 * safe to call in interrupt context.
65 void emergency_restart(void)
67 kmsg_dump(KMSG_DUMP_EMERG);
68 machine_emergency_restart();
70 EXPORT_SYMBOL_GPL(emergency_restart);
72 void kernel_restart_prepare(char *cmd)
74 blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
75 system_state = SYSTEM_RESTART;
76 usermodehelper_disable();
81 * register_reboot_notifier - Register function to be called at reboot time
82 * @nb: Info about notifier function to be called
84 * Registers a function with the list of functions
85 * to be called at reboot time.
87 * Currently always returns zero, as blocking_notifier_chain_register()
88 * always returns zero.
90 int register_reboot_notifier(struct notifier_block *nb)
92 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
94 EXPORT_SYMBOL(register_reboot_notifier);
97 * unregister_reboot_notifier - Unregister previously registered reboot notifier
98 * @nb: Hook to be unregistered
100 * Unregisters a previously registered reboot
103 * Returns zero on success, or %-ENOENT on failure.
105 int unregister_reboot_notifier(struct notifier_block *nb)
107 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
109 EXPORT_SYMBOL(unregister_reboot_notifier);
111 static void devm_unregister_reboot_notifier(struct device *dev, void *res)
113 WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
116 int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
118 struct notifier_block **rcnb;
121 rcnb = devres_alloc(devm_unregister_reboot_notifier,
122 sizeof(*rcnb), GFP_KERNEL);
126 ret = register_reboot_notifier(nb);
129 devres_add(dev, rcnb);
136 EXPORT_SYMBOL(devm_register_reboot_notifier);
139 * Notifier list for kernel code which wants to be called
140 * to restart the system.
142 static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
145 * register_restart_handler - Register function to be called to reset
147 * @nb: Info about handler function to be called
148 * @nb->priority: Handler priority. Handlers should follow the
149 * following guidelines for setting priorities.
150 * 0: Restart handler of last resort,
151 * with limited restart capabilities
152 * 128: Default restart handler; use if no other
153 * restart handler is expected to be available,
154 * and/or if restart functionality is
155 * sufficient to restart the entire system
156 * 255: Highest priority restart handler, will
157 * preempt all other restart handlers
159 * Registers a function with code to be called to restart the
162 * Registered functions will be called from machine_restart as last
163 * step of the restart sequence (if the architecture specific
164 * machine_restart function calls do_kernel_restart - see below
166 * Registered functions are expected to restart the system immediately.
167 * If more than one function is registered, the restart handler priority
168 * selects which function will be called first.
170 * Restart handlers are expected to be registered from non-architecture
171 * code, typically from drivers. A typical use case would be a system
172 * where restart functionality is provided through a watchdog. Multiple
173 * restart handlers may exist; for example, one restart handler might
174 * restart the entire system, while another only restarts the CPU.
175 * In such cases, the restart handler which only restarts part of the
176 * hardware is expected to register with low priority to ensure that
177 * it only runs if no other means to restart the system is available.
179 * Currently always returns zero, as atomic_notifier_chain_register()
180 * always returns zero.
182 int register_restart_handler(struct notifier_block *nb)
184 return atomic_notifier_chain_register(&restart_handler_list, nb);
186 EXPORT_SYMBOL(register_restart_handler);
189 * unregister_restart_handler - Unregister previously registered
191 * @nb: Hook to be unregistered
193 * Unregisters a previously registered restart handler function.
195 * Returns zero on success, or %-ENOENT on failure.
197 int unregister_restart_handler(struct notifier_block *nb)
199 return atomic_notifier_chain_unregister(&restart_handler_list, nb);
201 EXPORT_SYMBOL(unregister_restart_handler);
204 * do_kernel_restart - Execute kernel restart handler call chain
206 * Calls functions registered with register_restart_handler.
208 * Expected to be called from machine_restart as last step of the restart
211 * Restarts the system immediately if a restart handler function has been
212 * registered. Otherwise does nothing.
214 void do_kernel_restart(char *cmd)
216 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
219 void migrate_to_reboot_cpu(void)
221 /* The boot cpu is always logical cpu 0 */
222 int cpu = reboot_cpu;
224 cpu_hotplug_disable();
226 /* Make certain the cpu I'm about to reboot on is online */
227 if (!cpu_online(cpu))
228 cpu = cpumask_first(cpu_online_mask);
230 /* Prevent races with other tasks migrating this task */
231 current->flags |= PF_NO_SETAFFINITY;
233 /* Make certain I only run on the appropriate processor */
234 set_cpus_allowed_ptr(current, cpumask_of(cpu));
238 * kernel_restart - reboot the system
239 * @cmd: pointer to buffer containing command to execute for restart
242 * Shutdown everything and perform a clean reboot.
243 * This is not safe to call in interrupt context.
245 void kernel_restart(char *cmd)
247 kernel_restart_prepare(cmd);
248 migrate_to_reboot_cpu();
251 pr_emerg("Restarting system\n");
253 pr_emerg("Restarting system with command '%s'\n", cmd);
254 kmsg_dump(KMSG_DUMP_SHUTDOWN);
255 machine_restart(cmd);
257 EXPORT_SYMBOL_GPL(kernel_restart);
259 static void kernel_shutdown_prepare(enum system_states state)
261 blocking_notifier_call_chain(&reboot_notifier_list,
262 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
263 system_state = state;
264 usermodehelper_disable();
268 * kernel_halt - halt the system
270 * Shutdown everything and perform a clean system halt.
272 void kernel_halt(void)
274 kernel_shutdown_prepare(SYSTEM_HALT);
275 migrate_to_reboot_cpu();
277 pr_emerg("System halted\n");
278 kmsg_dump(KMSG_DUMP_SHUTDOWN);
281 EXPORT_SYMBOL_GPL(kernel_halt);
284 * kernel_power_off - power_off the system
286 * Shutdown everything and perform a clean system power_off.
288 void kernel_power_off(void)
290 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
291 if (pm_power_off_prepare)
292 pm_power_off_prepare();
293 migrate_to_reboot_cpu();
295 pr_emerg("Power down\n");
296 kmsg_dump(KMSG_DUMP_SHUTDOWN);
299 EXPORT_SYMBOL_GPL(kernel_power_off);
301 DEFINE_MUTEX(system_transition_mutex);
304 * Reboot system call: for obvious reasons only root may call it,
305 * and even root needs to set up some magic numbers in the registers
306 * so that some mistake won't make this reboot the whole machine.
307 * You can also set the meaning of the ctrl-alt-del-key here.
309 * reboot doesn't sync: do that yourself before calling this.
311 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
314 struct pid_namespace *pid_ns = task_active_pid_ns(current);
318 /* We only trust the superuser with rebooting the system. */
319 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
322 /* For safety, we require "magic" arguments. */
323 if (magic1 != LINUX_REBOOT_MAGIC1 ||
324 (magic2 != LINUX_REBOOT_MAGIC2 &&
325 magic2 != LINUX_REBOOT_MAGIC2A &&
326 magic2 != LINUX_REBOOT_MAGIC2B &&
327 magic2 != LINUX_REBOOT_MAGIC2C))
331 * If pid namespaces are enabled and the current task is in a child
332 * pid_namespace, the command is handled by reboot_pid_ns() which will
335 ret = reboot_pid_ns(pid_ns, cmd);
339 /* Instead of trying to make the power_off code look like
340 * halt when pm_power_off is not set do it the easy way.
342 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
343 cmd = LINUX_REBOOT_CMD_HALT;
345 mutex_lock(&system_transition_mutex);
347 case LINUX_REBOOT_CMD_RESTART:
348 kernel_restart(NULL);
351 case LINUX_REBOOT_CMD_CAD_ON:
355 case LINUX_REBOOT_CMD_CAD_OFF:
359 case LINUX_REBOOT_CMD_HALT:
363 case LINUX_REBOOT_CMD_POWER_OFF:
368 case LINUX_REBOOT_CMD_RESTART2:
369 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
374 buffer[sizeof(buffer) - 1] = '\0';
376 kernel_restart(buffer);
379 #ifdef CONFIG_KEXEC_CORE
380 case LINUX_REBOOT_CMD_KEXEC:
381 ret = kernel_kexec();
385 #ifdef CONFIG_HIBERNATION
386 case LINUX_REBOOT_CMD_SW_SUSPEND:
395 mutex_unlock(&system_transition_mutex);
399 static void deferred_cad(struct work_struct *dummy)
401 kernel_restart(NULL);
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.
409 void ctrl_alt_del(void)
411 static DECLARE_WORK(cad_work, deferred_cad);
414 schedule_work(&cad_work);
416 kill_cad_pid(SIGINT, 1);
419 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
420 static const char reboot_cmd[] = "/sbin/reboot";
422 static int run_cmd(const char *cmd)
425 static char *envp[] = {
427 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
431 argv = argv_split(GFP_KERNEL, cmd, NULL);
433 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
442 static int __orderly_reboot(void)
446 ret = run_cmd(reboot_cmd);
449 pr_warn("Failed to start orderly reboot: forcing the issue\n");
451 kernel_restart(NULL);
457 static int __orderly_poweroff(bool force)
461 ret = run_cmd(poweroff_cmd);
464 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
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?
478 static bool poweroff_force;
480 static void poweroff_work_func(struct work_struct *work)
482 __orderly_poweroff(poweroff_force);
485 static DECLARE_WORK(poweroff_work, poweroff_work_func);
488 * orderly_poweroff - Trigger an orderly system poweroff
489 * @force: force poweroff if command execution fails
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.
494 void orderly_poweroff(bool force)
496 if (force) /* do not override the pending "true" */
497 poweroff_force = true;
498 schedule_work(&poweroff_work);
500 EXPORT_SYMBOL_GPL(orderly_poweroff);
502 static void reboot_work_func(struct work_struct *work)
507 static DECLARE_WORK(reboot_work, reboot_work_func);
510 * orderly_reboot - Trigger an orderly system reboot
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.
515 void orderly_reboot(void)
517 schedule_work(&reboot_work);
519 EXPORT_SYMBOL_GPL(orderly_reboot);
522 * hw_failure_emergency_poweroff_func - emergency poweroff work after a known delay
523 * @work: work_struct associated with the emergency poweroff function
525 * This function is called in very critical situations to force
526 * a kernel poweroff after a configurable timeout value.
528 static void hw_failure_emergency_poweroff_func(struct work_struct *work)
531 * We have reached here after the emergency shutdown waiting period has
532 * expired. This means orderly_poweroff has not been able to shut off
533 * the system for some reason.
535 * Try to shut down the system immediately using kernel_power_off
538 pr_emerg("Hardware protection timed-out. Trying forced poweroff\n");
542 * Worst of the worst case trigger emergency restart
544 pr_emerg("Hardware protection shutdown failed. Trying emergency restart\n");
548 static DECLARE_DELAYED_WORK(hw_failure_emergency_poweroff_work,
549 hw_failure_emergency_poweroff_func);
552 * hw_failure_emergency_poweroff - Trigger an emergency system poweroff
554 * This may be called from any critical situation to trigger a system shutdown
555 * after a given period of time. If time is negative this is not scheduled.
557 static void hw_failure_emergency_poweroff(int poweroff_delay_ms)
559 if (poweroff_delay_ms <= 0)
561 schedule_delayed_work(&hw_failure_emergency_poweroff_work,
562 msecs_to_jiffies(poweroff_delay_ms));
566 * hw_protection_shutdown - Trigger an emergency system poweroff
568 * @reason: Reason of emergency shutdown to be printed.
569 * @ms_until_forced: Time to wait for orderly shutdown before tiggering a
570 * forced shudown. Negative value disables the forced
573 * Initiate an emergency system shutdown in order to protect hardware from
574 * further damage. Usage examples include a thermal protection or a voltage or
575 * current regulator failures.
576 * NOTE: The request is ignored if protection shutdown is already pending even
577 * if the previous request has given a large timeout for forced shutdown.
578 * Can be called from any context.
580 void hw_protection_shutdown(const char *reason, int ms_until_forced)
582 static atomic_t allow_proceed = ATOMIC_INIT(1);
584 pr_emerg("HARDWARE PROTECTION shutdown (%s)\n", reason);
586 /* Shutdown should be initiated only once. */
587 if (!atomic_dec_and_test(&allow_proceed))
591 * Queue a backup emergency shutdown in the event of
592 * orderly_poweroff failure
594 hw_failure_emergency_poweroff(ms_until_forced);
595 orderly_poweroff(true);
597 EXPORT_SYMBOL_GPL(hw_protection_shutdown);
599 static int __init reboot_setup(char *str)
602 enum reboot_mode *mode;
605 * Having anything passed on the command line via
606 * reboot= will cause us to disable DMI checking
611 if (!strncmp(str, "panic_", 6)) {
612 mode = &panic_reboot_mode;
633 * reboot_cpu is s[mp]#### with #### being the processor
634 * to be used for rebooting. Skip 's' or 'smp' prefix.
636 str += str[1] == 'm' && str[2] == 'p' ? 3 : 1;
638 if (isdigit(str[0])) {
639 int cpu = simple_strtoul(str, NULL, 0);
641 if (cpu >= num_possible_cpus()) {
642 pr_err("Ignoring the CPU number in reboot= option. "
643 "CPU %d exceeds possible cpu number %d\n",
644 cpu, num_possible_cpus());
670 str = strchr(str, ',');
678 __setup("reboot=", reboot_setup);
682 #define REBOOT_COLD_STR "cold"
683 #define REBOOT_WARM_STR "warm"
684 #define REBOOT_HARD_STR "hard"
685 #define REBOOT_SOFT_STR "soft"
686 #define REBOOT_GPIO_STR "gpio"
687 #define REBOOT_UNDEFINED_STR "undefined"
689 #define BOOT_TRIPLE_STR "triple"
690 #define BOOT_KBD_STR "kbd"
691 #define BOOT_BIOS_STR "bios"
692 #define BOOT_ACPI_STR "acpi"
693 #define BOOT_EFI_STR "efi"
694 #define BOOT_PCI_STR "pci"
696 static ssize_t mode_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
700 switch (reboot_mode) {
702 val = REBOOT_COLD_STR;
705 val = REBOOT_WARM_STR;
708 val = REBOOT_HARD_STR;
711 val = REBOOT_SOFT_STR;
714 val = REBOOT_GPIO_STR;
717 val = REBOOT_UNDEFINED_STR;
720 return sprintf(buf, "%s\n", val);
722 static ssize_t mode_store(struct kobject *kobj, struct kobj_attribute *attr,
723 const char *buf, size_t count)
725 if (!capable(CAP_SYS_BOOT))
728 if (!strncmp(buf, REBOOT_COLD_STR, strlen(REBOOT_COLD_STR)))
729 reboot_mode = REBOOT_COLD;
730 else if (!strncmp(buf, REBOOT_WARM_STR, strlen(REBOOT_WARM_STR)))
731 reboot_mode = REBOOT_WARM;
732 else if (!strncmp(buf, REBOOT_HARD_STR, strlen(REBOOT_HARD_STR)))
733 reboot_mode = REBOOT_HARD;
734 else if (!strncmp(buf, REBOOT_SOFT_STR, strlen(REBOOT_SOFT_STR)))
735 reboot_mode = REBOOT_SOFT;
736 else if (!strncmp(buf, REBOOT_GPIO_STR, strlen(REBOOT_GPIO_STR)))
737 reboot_mode = REBOOT_GPIO;
745 static struct kobj_attribute reboot_mode_attr = __ATTR_RW(mode);
748 static ssize_t force_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
750 return sprintf(buf, "%d\n", reboot_force);
752 static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
753 const char *buf, size_t count)
757 if (!capable(CAP_SYS_BOOT))
760 if (kstrtobool(buf, &res))
768 static struct kobj_attribute reboot_force_attr = __ATTR_RW(force);
770 static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
774 switch (reboot_type) {
776 val = BOOT_TRIPLE_STR;
794 val = REBOOT_UNDEFINED_STR;
797 return sprintf(buf, "%s\n", val);
799 static ssize_t type_store(struct kobject *kobj, struct kobj_attribute *attr,
800 const char *buf, size_t count)
802 if (!capable(CAP_SYS_BOOT))
805 if (!strncmp(buf, BOOT_TRIPLE_STR, strlen(BOOT_TRIPLE_STR)))
806 reboot_type = BOOT_TRIPLE;
807 else if (!strncmp(buf, BOOT_KBD_STR, strlen(BOOT_KBD_STR)))
808 reboot_type = BOOT_KBD;
809 else if (!strncmp(buf, BOOT_BIOS_STR, strlen(BOOT_BIOS_STR)))
810 reboot_type = BOOT_BIOS;
811 else if (!strncmp(buf, BOOT_ACPI_STR, strlen(BOOT_ACPI_STR)))
812 reboot_type = BOOT_ACPI;
813 else if (!strncmp(buf, BOOT_EFI_STR, strlen(BOOT_EFI_STR)))
814 reboot_type = BOOT_EFI;
815 else if (!strncmp(buf, BOOT_PCI_STR, strlen(BOOT_PCI_STR)))
816 reboot_type = BOOT_CF9_FORCE;
824 static struct kobj_attribute reboot_type_attr = __ATTR_RW(type);
828 static ssize_t cpu_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
830 return sprintf(buf, "%d\n", reboot_cpu);
832 static ssize_t cpu_store(struct kobject *kobj, struct kobj_attribute *attr,
833 const char *buf, size_t count)
838 if (!capable(CAP_SYS_BOOT))
841 rc = kstrtouint(buf, 0, &cpunum);
846 if (cpunum >= num_possible_cpus())
854 static struct kobj_attribute reboot_cpu_attr = __ATTR_RW(cpu);
857 static struct attribute *reboot_attrs[] = {
858 &reboot_mode_attr.attr,
860 &reboot_force_attr.attr,
861 &reboot_type_attr.attr,
864 &reboot_cpu_attr.attr,
869 static const struct attribute_group reboot_attr_group = {
870 .attrs = reboot_attrs,
873 static int __init reboot_ksysfs_init(void)
875 struct kobject *reboot_kobj;
878 reboot_kobj = kobject_create_and_add("reboot", kernel_kobj);
882 ret = sysfs_create_group(reboot_kobj, &reboot_attr_group);
884 kobject_put(reboot_kobj);
890 late_initcall(reboot_ksysfs_init);