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 EXPORT_SYMBOL_GPL(reboot_mode);
37 enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
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.
46 int reboot_default = 1;
48 enum reboot_type reboot_type = BOOT_ACPI;
52 * If set, this is used for preparing the system to power off.
55 void (*pm_power_off_prepare)(void);
56 EXPORT_SYMBOL_GPL(pm_power_off_prepare);
59 * emergency_restart - reboot the system
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.
66 void emergency_restart(void)
68 kmsg_dump(KMSG_DUMP_EMERG);
69 machine_emergency_restart();
71 EXPORT_SYMBOL_GPL(emergency_restart);
73 void kernel_restart_prepare(char *cmd)
75 blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
76 system_state = SYSTEM_RESTART;
77 try_block_console_kthreads(10000);
78 usermodehelper_disable();
83 * register_reboot_notifier - Register function to be called at reboot time
84 * @nb: Info about notifier function to be called
86 * Registers a function with the list of functions
87 * to be called at reboot time.
89 * Currently always returns zero, as blocking_notifier_chain_register()
90 * always returns zero.
92 int register_reboot_notifier(struct notifier_block *nb)
94 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
96 EXPORT_SYMBOL(register_reboot_notifier);
99 * unregister_reboot_notifier - Unregister previously registered reboot notifier
100 * @nb: Hook to be unregistered
102 * Unregisters a previously registered reboot
105 * Returns zero on success, or %-ENOENT on failure.
107 int unregister_reboot_notifier(struct notifier_block *nb)
109 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
111 EXPORT_SYMBOL(unregister_reboot_notifier);
113 static void devm_unregister_reboot_notifier(struct device *dev, void *res)
115 WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
118 int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
120 struct notifier_block **rcnb;
123 rcnb = devres_alloc(devm_unregister_reboot_notifier,
124 sizeof(*rcnb), GFP_KERNEL);
128 ret = register_reboot_notifier(nb);
131 devres_add(dev, rcnb);
138 EXPORT_SYMBOL(devm_register_reboot_notifier);
141 * Notifier list for kernel code which wants to be called
142 * to restart the system.
144 static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
147 * register_restart_handler - Register function to be called to reset
149 * @nb: Info about handler function to be called
150 * @nb->priority: Handler priority. Handlers should follow the
151 * following guidelines for setting priorities.
152 * 0: Restart handler of last resort,
153 * with limited restart capabilities
154 * 128: Default restart handler; use if no other
155 * restart handler is expected to be available,
156 * and/or if restart functionality is
157 * sufficient to restart the entire system
158 * 255: Highest priority restart handler, will
159 * preempt all other restart handlers
161 * Registers a function with code to be called to restart the
164 * Registered functions will be called from machine_restart as last
165 * step of the restart sequence (if the architecture specific
166 * machine_restart function calls do_kernel_restart - see below
168 * Registered functions are expected to restart the system immediately.
169 * If more than one function is registered, the restart handler priority
170 * selects which function will be called first.
172 * Restart handlers are expected to be registered from non-architecture
173 * code, typically from drivers. A typical use case would be a system
174 * where restart functionality is provided through a watchdog. Multiple
175 * restart handlers may exist; for example, one restart handler might
176 * restart the entire system, while another only restarts the CPU.
177 * In such cases, the restart handler which only restarts part of the
178 * hardware is expected to register with low priority to ensure that
179 * it only runs if no other means to restart the system is available.
181 * Currently always returns zero, as atomic_notifier_chain_register()
182 * always returns zero.
184 int register_restart_handler(struct notifier_block *nb)
186 return atomic_notifier_chain_register(&restart_handler_list, nb);
188 EXPORT_SYMBOL(register_restart_handler);
191 * unregister_restart_handler - Unregister previously registered
193 * @nb: Hook to be unregistered
195 * Unregisters a previously registered restart handler function.
197 * Returns zero on success, or %-ENOENT on failure.
199 int unregister_restart_handler(struct notifier_block *nb)
201 return atomic_notifier_chain_unregister(&restart_handler_list, nb);
203 EXPORT_SYMBOL(unregister_restart_handler);
206 * do_kernel_restart - Execute kernel restart handler call chain
208 * Calls functions registered with register_restart_handler.
210 * Expected to be called from machine_restart as last step of the restart
213 * Restarts the system immediately if a restart handler function has been
214 * registered. Otherwise does nothing.
216 void do_kernel_restart(char *cmd)
218 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
221 void migrate_to_reboot_cpu(void)
223 /* The boot cpu is always logical cpu 0 */
224 int cpu = reboot_cpu;
226 cpu_hotplug_disable();
228 /* Make certain the cpu I'm about to reboot on is online */
229 if (!cpu_online(cpu))
230 cpu = cpumask_first(cpu_online_mask);
232 /* Prevent races with other tasks migrating this task */
233 current->flags |= PF_NO_SETAFFINITY;
235 /* Make certain I only run on the appropriate processor */
236 set_cpus_allowed_ptr(current, cpumask_of(cpu));
240 * kernel_restart - reboot the system
241 * @cmd: pointer to buffer containing command to execute for restart
244 * Shutdown everything and perform a clean reboot.
245 * This is not safe to call in interrupt context.
247 void kernel_restart(char *cmd)
249 kernel_restart_prepare(cmd);
250 migrate_to_reboot_cpu();
253 pr_emerg("Restarting system\n");
255 pr_emerg("Restarting system with command '%s'\n", cmd);
256 kmsg_dump(KMSG_DUMP_SHUTDOWN);
257 machine_restart(cmd);
259 EXPORT_SYMBOL_GPL(kernel_restart);
261 static void kernel_shutdown_prepare(enum system_states state)
263 blocking_notifier_call_chain(&reboot_notifier_list,
264 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
265 system_state = state;
266 try_block_console_kthreads(10000);
267 usermodehelper_disable();
271 * kernel_halt - halt the system
273 * Shutdown everything and perform a clean system halt.
275 void kernel_halt(void)
277 kernel_shutdown_prepare(SYSTEM_HALT);
278 migrate_to_reboot_cpu();
280 pr_emerg("System halted\n");
281 kmsg_dump(KMSG_DUMP_SHUTDOWN);
284 EXPORT_SYMBOL_GPL(kernel_halt);
287 * kernel_power_off - power_off the system
289 * Shutdown everything and perform a clean system power_off.
291 void kernel_power_off(void)
293 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
294 if (pm_power_off_prepare)
295 pm_power_off_prepare();
296 migrate_to_reboot_cpu();
298 pr_emerg("Power down\n");
299 kmsg_dump(KMSG_DUMP_SHUTDOWN);
302 EXPORT_SYMBOL_GPL(kernel_power_off);
304 DEFINE_MUTEX(system_transition_mutex);
307 * Reboot system call: for obvious reasons only root may call it,
308 * and even root needs to set up some magic numbers in the registers
309 * so that some mistake won't make this reboot the whole machine.
310 * You can also set the meaning of the ctrl-alt-del-key here.
312 * reboot doesn't sync: do that yourself before calling this.
314 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
317 struct pid_namespace *pid_ns = task_active_pid_ns(current);
321 /* We only trust the superuser with rebooting the system. */
322 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
325 /* For safety, we require "magic" arguments. */
326 if (magic1 != LINUX_REBOOT_MAGIC1 ||
327 (magic2 != LINUX_REBOOT_MAGIC2 &&
328 magic2 != LINUX_REBOOT_MAGIC2A &&
329 magic2 != LINUX_REBOOT_MAGIC2B &&
330 magic2 != LINUX_REBOOT_MAGIC2C))
334 * If pid namespaces are enabled and the current task is in a child
335 * pid_namespace, the command is handled by reboot_pid_ns() which will
338 ret = reboot_pid_ns(pid_ns, cmd);
342 /* Instead of trying to make the power_off code look like
343 * halt when pm_power_off is not set do it the easy way.
345 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
346 cmd = LINUX_REBOOT_CMD_HALT;
348 mutex_lock(&system_transition_mutex);
350 case LINUX_REBOOT_CMD_RESTART:
351 kernel_restart(NULL);
354 case LINUX_REBOOT_CMD_CAD_ON:
358 case LINUX_REBOOT_CMD_CAD_OFF:
362 case LINUX_REBOOT_CMD_HALT:
366 case LINUX_REBOOT_CMD_POWER_OFF:
371 case LINUX_REBOOT_CMD_RESTART2:
372 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
377 buffer[sizeof(buffer) - 1] = '\0';
379 kernel_restart(buffer);
382 #ifdef CONFIG_KEXEC_CORE
383 case LINUX_REBOOT_CMD_KEXEC:
384 ret = kernel_kexec();
388 #ifdef CONFIG_HIBERNATION
389 case LINUX_REBOOT_CMD_SW_SUSPEND:
398 mutex_unlock(&system_transition_mutex);
402 static void deferred_cad(struct work_struct *dummy)
404 kernel_restart(NULL);
408 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
409 * As it's called within an interrupt, it may NOT sync: the only choice
410 * is whether to reboot at once, or just ignore the ctrl-alt-del.
412 void ctrl_alt_del(void)
414 static DECLARE_WORK(cad_work, deferred_cad);
417 schedule_work(&cad_work);
419 kill_cad_pid(SIGINT, 1);
422 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
423 static const char reboot_cmd[] = "/sbin/reboot";
425 static int run_cmd(const char *cmd)
428 static char *envp[] = {
430 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
434 argv = argv_split(GFP_KERNEL, cmd, NULL);
436 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
445 static int __orderly_reboot(void)
449 ret = run_cmd(reboot_cmd);
452 printk_prefer_direct_enter();
453 pr_warn("Failed to start orderly reboot: forcing the issue\n");
455 kernel_restart(NULL);
456 printk_prefer_direct_exit();
462 static int __orderly_poweroff(bool force)
466 ret = run_cmd(poweroff_cmd);
469 printk_prefer_direct_enter();
470 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
473 * I guess this should try to kick off some daemon to sync and
474 * poweroff asap. Or not even bother syncing if we're doing an
475 * emergency shutdown?
479 printk_prefer_direct_exit();
485 static bool poweroff_force;
487 static void poweroff_work_func(struct work_struct *work)
489 __orderly_poweroff(poweroff_force);
492 static DECLARE_WORK(poweroff_work, poweroff_work_func);
495 * orderly_poweroff - Trigger an orderly system poweroff
496 * @force: force poweroff if command execution fails
498 * This may be called from any context to trigger a system shutdown.
499 * If the orderly shutdown fails, it will force an immediate shutdown.
501 void orderly_poweroff(bool force)
503 if (force) /* do not override the pending "true" */
504 poweroff_force = true;
505 schedule_work(&poweroff_work);
507 EXPORT_SYMBOL_GPL(orderly_poweroff);
509 static void reboot_work_func(struct work_struct *work)
514 static DECLARE_WORK(reboot_work, reboot_work_func);
517 * orderly_reboot - Trigger an orderly system reboot
519 * This may be called from any context to trigger a system reboot.
520 * If the orderly reboot fails, it will force an immediate reboot.
522 void orderly_reboot(void)
524 schedule_work(&reboot_work);
526 EXPORT_SYMBOL_GPL(orderly_reboot);
529 * hw_failure_emergency_poweroff_func - emergency poweroff work after a known delay
530 * @work: work_struct associated with the emergency poweroff function
532 * This function is called in very critical situations to force
533 * a kernel poweroff after a configurable timeout value.
535 static void hw_failure_emergency_poweroff_func(struct work_struct *work)
537 printk_prefer_direct_enter();
540 * We have reached here after the emergency shutdown waiting period has
541 * expired. This means orderly_poweroff has not been able to shut off
542 * the system for some reason.
544 * Try to shut down the system immediately using kernel_power_off
547 pr_emerg("Hardware protection timed-out. Trying forced poweroff\n");
551 * Worst of the worst case trigger emergency restart
553 pr_emerg("Hardware protection shutdown failed. Trying emergency restart\n");
556 printk_prefer_direct_exit();
559 static DECLARE_DELAYED_WORK(hw_failure_emergency_poweroff_work,
560 hw_failure_emergency_poweroff_func);
563 * hw_failure_emergency_poweroff - Trigger an emergency system poweroff
565 * This may be called from any critical situation to trigger a system shutdown
566 * after a given period of time. If time is negative this is not scheduled.
568 static void hw_failure_emergency_poweroff(int poweroff_delay_ms)
570 if (poweroff_delay_ms <= 0)
572 schedule_delayed_work(&hw_failure_emergency_poweroff_work,
573 msecs_to_jiffies(poweroff_delay_ms));
577 * hw_protection_shutdown - Trigger an emergency system poweroff
579 * @reason: Reason of emergency shutdown to be printed.
580 * @ms_until_forced: Time to wait for orderly shutdown before tiggering a
581 * forced shudown. Negative value disables the forced
584 * Initiate an emergency system shutdown in order to protect hardware from
585 * further damage. Usage examples include a thermal protection or a voltage or
586 * current regulator failures.
587 * NOTE: The request is ignored if protection shutdown is already pending even
588 * if the previous request has given a large timeout for forced shutdown.
589 * Can be called from any context.
591 void hw_protection_shutdown(const char *reason, int ms_until_forced)
593 static atomic_t allow_proceed = ATOMIC_INIT(1);
595 printk_prefer_direct_enter();
597 pr_emerg("HARDWARE PROTECTION shutdown (%s)\n", reason);
599 /* Shutdown should be initiated only once. */
600 if (!atomic_dec_and_test(&allow_proceed))
604 * Queue a backup emergency shutdown in the event of
605 * orderly_poweroff failure
607 hw_failure_emergency_poweroff(ms_until_forced);
608 orderly_poweroff(true);
610 printk_prefer_direct_exit();
612 EXPORT_SYMBOL_GPL(hw_protection_shutdown);
614 static int __init reboot_setup(char *str)
617 enum reboot_mode *mode;
620 * Having anything passed on the command line via
621 * reboot= will cause us to disable DMI checking
626 if (!strncmp(str, "panic_", 6)) {
627 mode = &panic_reboot_mode;
648 * reboot_cpu is s[mp]#### with #### being the processor
649 * to be used for rebooting. Skip 's' or 'smp' prefix.
651 str += str[1] == 'm' && str[2] == 'p' ? 3 : 1;
653 if (isdigit(str[0])) {
654 int cpu = simple_strtoul(str, NULL, 0);
656 if (cpu >= num_possible_cpus()) {
657 pr_err("Ignoring the CPU number in reboot= option. "
658 "CPU %d exceeds possible cpu number %d\n",
659 cpu, num_possible_cpus());
685 str = strchr(str, ',');
693 __setup("reboot=", reboot_setup);
697 #define REBOOT_COLD_STR "cold"
698 #define REBOOT_WARM_STR "warm"
699 #define REBOOT_HARD_STR "hard"
700 #define REBOOT_SOFT_STR "soft"
701 #define REBOOT_GPIO_STR "gpio"
702 #define REBOOT_UNDEFINED_STR "undefined"
704 #define BOOT_TRIPLE_STR "triple"
705 #define BOOT_KBD_STR "kbd"
706 #define BOOT_BIOS_STR "bios"
707 #define BOOT_ACPI_STR "acpi"
708 #define BOOT_EFI_STR "efi"
709 #define BOOT_PCI_STR "pci"
711 static ssize_t mode_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
715 switch (reboot_mode) {
717 val = REBOOT_COLD_STR;
720 val = REBOOT_WARM_STR;
723 val = REBOOT_HARD_STR;
726 val = REBOOT_SOFT_STR;
729 val = REBOOT_GPIO_STR;
732 val = REBOOT_UNDEFINED_STR;
735 return sprintf(buf, "%s\n", val);
737 static ssize_t mode_store(struct kobject *kobj, struct kobj_attribute *attr,
738 const char *buf, size_t count)
740 if (!capable(CAP_SYS_BOOT))
743 if (!strncmp(buf, REBOOT_COLD_STR, strlen(REBOOT_COLD_STR)))
744 reboot_mode = REBOOT_COLD;
745 else if (!strncmp(buf, REBOOT_WARM_STR, strlen(REBOOT_WARM_STR)))
746 reboot_mode = REBOOT_WARM;
747 else if (!strncmp(buf, REBOOT_HARD_STR, strlen(REBOOT_HARD_STR)))
748 reboot_mode = REBOOT_HARD;
749 else if (!strncmp(buf, REBOOT_SOFT_STR, strlen(REBOOT_SOFT_STR)))
750 reboot_mode = REBOOT_SOFT;
751 else if (!strncmp(buf, REBOOT_GPIO_STR, strlen(REBOOT_GPIO_STR)))
752 reboot_mode = REBOOT_GPIO;
760 static struct kobj_attribute reboot_mode_attr = __ATTR_RW(mode);
763 static ssize_t force_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
765 return sprintf(buf, "%d\n", reboot_force);
767 static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
768 const char *buf, size_t count)
772 if (!capable(CAP_SYS_BOOT))
775 if (kstrtobool(buf, &res))
783 static struct kobj_attribute reboot_force_attr = __ATTR_RW(force);
785 static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
789 switch (reboot_type) {
791 val = BOOT_TRIPLE_STR;
809 val = REBOOT_UNDEFINED_STR;
812 return sprintf(buf, "%s\n", val);
814 static ssize_t type_store(struct kobject *kobj, struct kobj_attribute *attr,
815 const char *buf, size_t count)
817 if (!capable(CAP_SYS_BOOT))
820 if (!strncmp(buf, BOOT_TRIPLE_STR, strlen(BOOT_TRIPLE_STR)))
821 reboot_type = BOOT_TRIPLE;
822 else if (!strncmp(buf, BOOT_KBD_STR, strlen(BOOT_KBD_STR)))
823 reboot_type = BOOT_KBD;
824 else if (!strncmp(buf, BOOT_BIOS_STR, strlen(BOOT_BIOS_STR)))
825 reboot_type = BOOT_BIOS;
826 else if (!strncmp(buf, BOOT_ACPI_STR, strlen(BOOT_ACPI_STR)))
827 reboot_type = BOOT_ACPI;
828 else if (!strncmp(buf, BOOT_EFI_STR, strlen(BOOT_EFI_STR)))
829 reboot_type = BOOT_EFI;
830 else if (!strncmp(buf, BOOT_PCI_STR, strlen(BOOT_PCI_STR)))
831 reboot_type = BOOT_CF9_FORCE;
839 static struct kobj_attribute reboot_type_attr = __ATTR_RW(type);
843 static ssize_t cpu_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
845 return sprintf(buf, "%d\n", reboot_cpu);
847 static ssize_t cpu_store(struct kobject *kobj, struct kobj_attribute *attr,
848 const char *buf, size_t count)
853 if (!capable(CAP_SYS_BOOT))
856 rc = kstrtouint(buf, 0, &cpunum);
861 if (cpunum >= num_possible_cpus())
869 static struct kobj_attribute reboot_cpu_attr = __ATTR_RW(cpu);
872 static struct attribute *reboot_attrs[] = {
873 &reboot_mode_attr.attr,
875 &reboot_force_attr.attr,
876 &reboot_type_attr.attr,
879 &reboot_cpu_attr.attr,
884 static const struct attribute_group reboot_attr_group = {
885 .attrs = reboot_attrs,
888 static int __init reboot_ksysfs_init(void)
890 struct kobject *reboot_kobj;
893 reboot_kobj = kobject_create_and_add("reboot", kernel_kobj);
897 ret = sysfs_create_group(reboot_kobj, &reboot_attr_group);
899 kobject_put(reboot_kobj);
905 late_initcall(reboot_ksysfs_init);