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 usermodehelper_disable();
82 * register_reboot_notifier - Register function to be called at reboot time
83 * @nb: Info about notifier function to be called
85 * Registers a function with the list of functions
86 * to be called at reboot time.
88 * Currently always returns zero, as blocking_notifier_chain_register()
89 * always returns zero.
91 int register_reboot_notifier(struct notifier_block *nb)
93 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
95 EXPORT_SYMBOL(register_reboot_notifier);
98 * unregister_reboot_notifier - Unregister previously registered reboot notifier
99 * @nb: Hook to be unregistered
101 * Unregisters a previously registered reboot
104 * Returns zero on success, or %-ENOENT on failure.
106 int unregister_reboot_notifier(struct notifier_block *nb)
108 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
110 EXPORT_SYMBOL(unregister_reboot_notifier);
112 static void devm_unregister_reboot_notifier(struct device *dev, void *res)
114 WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
117 int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
119 struct notifier_block **rcnb;
122 rcnb = devres_alloc(devm_unregister_reboot_notifier,
123 sizeof(*rcnb), GFP_KERNEL);
127 ret = register_reboot_notifier(nb);
130 devres_add(dev, rcnb);
137 EXPORT_SYMBOL(devm_register_reboot_notifier);
140 * Notifier list for kernel code which wants to be called
141 * to restart the system.
143 static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
146 * register_restart_handler - Register function to be called to reset
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
160 * Registers a function with code to be called to restart the
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
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.
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.
180 * Currently always returns zero, as atomic_notifier_chain_register()
181 * always returns zero.
183 int register_restart_handler(struct notifier_block *nb)
185 return atomic_notifier_chain_register(&restart_handler_list, nb);
187 EXPORT_SYMBOL(register_restart_handler);
190 * unregister_restart_handler - Unregister previously registered
192 * @nb: Hook to be unregistered
194 * Unregisters a previously registered restart handler function.
196 * Returns zero on success, or %-ENOENT on failure.
198 int unregister_restart_handler(struct notifier_block *nb)
200 return atomic_notifier_chain_unregister(&restart_handler_list, nb);
202 EXPORT_SYMBOL(unregister_restart_handler);
205 * do_kernel_restart - Execute kernel restart handler call chain
207 * Calls functions registered with register_restart_handler.
209 * Expected to be called from machine_restart as last step of the restart
212 * Restarts the system immediately if a restart handler function has been
213 * registered. Otherwise does nothing.
215 void do_kernel_restart(char *cmd)
217 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
220 void migrate_to_reboot_cpu(void)
222 /* The boot cpu is always logical cpu 0 */
223 int cpu = reboot_cpu;
225 cpu_hotplug_disable();
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);
231 /* Prevent races with other tasks migrating this task */
232 current->flags |= PF_NO_SETAFFINITY;
234 /* Make certain I only run on the appropriate processor */
235 set_cpus_allowed_ptr(current, cpumask_of(cpu));
239 * kernel_restart - reboot the system
240 * @cmd: pointer to buffer containing command to execute for restart
243 * Shutdown everything and perform a clean reboot.
244 * This is not safe to call in interrupt context.
246 void kernel_restart(char *cmd)
248 kernel_restart_prepare(cmd);
249 migrate_to_reboot_cpu();
252 pr_emerg("Restarting system\n");
254 pr_emerg("Restarting system with command '%s'\n", cmd);
255 kmsg_dump(KMSG_DUMP_SHUTDOWN);
256 machine_restart(cmd);
258 EXPORT_SYMBOL_GPL(kernel_restart);
260 static void kernel_shutdown_prepare(enum system_states state)
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();
269 * kernel_halt - halt the system
271 * Shutdown everything and perform a clean system halt.
273 void kernel_halt(void)
275 kernel_shutdown_prepare(SYSTEM_HALT);
276 migrate_to_reboot_cpu();
278 pr_emerg("System halted\n");
279 kmsg_dump(KMSG_DUMP_SHUTDOWN);
282 EXPORT_SYMBOL_GPL(kernel_halt);
285 * kernel_power_off - power_off the system
287 * Shutdown everything and perform a clean system power_off.
289 void kernel_power_off(void)
291 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
292 if (pm_power_off_prepare)
293 pm_power_off_prepare();
294 migrate_to_reboot_cpu();
296 pr_emerg("Power down\n");
297 kmsg_dump(KMSG_DUMP_SHUTDOWN);
300 EXPORT_SYMBOL_GPL(kernel_power_off);
302 DEFINE_MUTEX(system_transition_mutex);
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.
310 * reboot doesn't sync: do that yourself before calling this.
312 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
315 struct pid_namespace *pid_ns = task_active_pid_ns(current);
319 /* We only trust the superuser with rebooting the system. */
320 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
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))
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
336 ret = reboot_pid_ns(pid_ns, cmd);
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.
343 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
344 cmd = LINUX_REBOOT_CMD_HALT;
346 mutex_lock(&system_transition_mutex);
348 case LINUX_REBOOT_CMD_RESTART:
349 kernel_restart(NULL);
352 case LINUX_REBOOT_CMD_CAD_ON:
356 case LINUX_REBOOT_CMD_CAD_OFF:
360 case LINUX_REBOOT_CMD_HALT:
364 case LINUX_REBOOT_CMD_POWER_OFF:
369 case LINUX_REBOOT_CMD_RESTART2:
370 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
375 buffer[sizeof(buffer) - 1] = '\0';
377 kernel_restart(buffer);
380 #ifdef CONFIG_KEXEC_CORE
381 case LINUX_REBOOT_CMD_KEXEC:
382 ret = kernel_kexec();
386 #ifdef CONFIG_HIBERNATION
387 case LINUX_REBOOT_CMD_SW_SUSPEND:
396 mutex_unlock(&system_transition_mutex);
400 static void deferred_cad(struct work_struct *dummy)
402 kernel_restart(NULL);
406 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
407 * As it's called within an interrupt, it may NOT sync: the only choice
408 * is whether to reboot at once, or just ignore the ctrl-alt-del.
410 void ctrl_alt_del(void)
412 static DECLARE_WORK(cad_work, deferred_cad);
415 schedule_work(&cad_work);
417 kill_cad_pid(SIGINT, 1);
420 #define POWEROFF_CMD_PATH_LEN 256
421 static char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
422 static const char reboot_cmd[] = "/sbin/reboot";
424 static int run_cmd(const char *cmd)
427 static char *envp[] = {
429 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
433 argv = argv_split(GFP_KERNEL, cmd, NULL);
435 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
444 static int __orderly_reboot(void)
448 ret = run_cmd(reboot_cmd);
451 printk_prefer_direct_enter();
452 pr_warn("Failed to start orderly reboot: forcing the issue\n");
454 kernel_restart(NULL);
455 printk_prefer_direct_exit();
461 static int __orderly_poweroff(bool force)
465 ret = run_cmd(poweroff_cmd);
468 printk_prefer_direct_enter();
469 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
472 * I guess this should try to kick off some daemon to sync and
473 * poweroff asap. Or not even bother syncing if we're doing an
474 * emergency shutdown?
478 printk_prefer_direct_exit();
484 static bool poweroff_force;
486 static void poweroff_work_func(struct work_struct *work)
488 __orderly_poweroff(poweroff_force);
491 static DECLARE_WORK(poweroff_work, poweroff_work_func);
494 * orderly_poweroff - Trigger an orderly system poweroff
495 * @force: force poweroff if command execution fails
497 * This may be called from any context to trigger a system shutdown.
498 * If the orderly shutdown fails, it will force an immediate shutdown.
500 void orderly_poweroff(bool force)
502 if (force) /* do not override the pending "true" */
503 poweroff_force = true;
504 schedule_work(&poweroff_work);
506 EXPORT_SYMBOL_GPL(orderly_poweroff);
508 static void reboot_work_func(struct work_struct *work)
513 static DECLARE_WORK(reboot_work, reboot_work_func);
516 * orderly_reboot - Trigger an orderly system reboot
518 * This may be called from any context to trigger a system reboot.
519 * If the orderly reboot fails, it will force an immediate reboot.
521 void orderly_reboot(void)
523 schedule_work(&reboot_work);
525 EXPORT_SYMBOL_GPL(orderly_reboot);
528 * hw_failure_emergency_poweroff_func - emergency poweroff work after a known delay
529 * @work: work_struct associated with the emergency poweroff function
531 * This function is called in very critical situations to force
532 * a kernel poweroff after a configurable timeout value.
534 static void hw_failure_emergency_poweroff_func(struct work_struct *work)
536 printk_prefer_direct_enter();
539 * We have reached here after the emergency shutdown waiting period has
540 * expired. This means orderly_poweroff has not been able to shut off
541 * the system for some reason.
543 * Try to shut down the system immediately using kernel_power_off
546 pr_emerg("Hardware protection timed-out. Trying forced poweroff\n");
550 * Worst of the worst case trigger emergency restart
552 pr_emerg("Hardware protection shutdown failed. Trying emergency restart\n");
555 printk_prefer_direct_exit();
558 static DECLARE_DELAYED_WORK(hw_failure_emergency_poweroff_work,
559 hw_failure_emergency_poweroff_func);
562 * hw_failure_emergency_poweroff - Trigger an emergency system poweroff
564 * This may be called from any critical situation to trigger a system shutdown
565 * after a given period of time. If time is negative this is not scheduled.
567 static void hw_failure_emergency_poweroff(int poweroff_delay_ms)
569 if (poweroff_delay_ms <= 0)
571 schedule_delayed_work(&hw_failure_emergency_poweroff_work,
572 msecs_to_jiffies(poweroff_delay_ms));
576 * hw_protection_shutdown - Trigger an emergency system poweroff
578 * @reason: Reason of emergency shutdown to be printed.
579 * @ms_until_forced: Time to wait for orderly shutdown before tiggering a
580 * forced shudown. Negative value disables the forced
583 * Initiate an emergency system shutdown in order to protect hardware from
584 * further damage. Usage examples include a thermal protection or a voltage or
585 * current regulator failures.
586 * NOTE: The request is ignored if protection shutdown is already pending even
587 * if the previous request has given a large timeout for forced shutdown.
588 * Can be called from any context.
590 void hw_protection_shutdown(const char *reason, int ms_until_forced)
592 static atomic_t allow_proceed = ATOMIC_INIT(1);
594 printk_prefer_direct_enter();
596 pr_emerg("HARDWARE PROTECTION shutdown (%s)\n", reason);
598 /* Shutdown should be initiated only once. */
599 if (!atomic_dec_and_test(&allow_proceed))
603 * Queue a backup emergency shutdown in the event of
604 * orderly_poweroff failure
606 hw_failure_emergency_poweroff(ms_until_forced);
607 orderly_poweroff(true);
609 printk_prefer_direct_exit();
611 EXPORT_SYMBOL_GPL(hw_protection_shutdown);
613 static int __init reboot_setup(char *str)
616 enum reboot_mode *mode;
619 * Having anything passed on the command line via
620 * reboot= will cause us to disable DMI checking
625 if (!strncmp(str, "panic_", 6)) {
626 mode = &panic_reboot_mode;
647 * reboot_cpu is s[mp]#### with #### being the processor
648 * to be used for rebooting. Skip 's' or 'smp' prefix.
650 str += str[1] == 'm' && str[2] == 'p' ? 3 : 1;
652 if (isdigit(str[0])) {
653 int cpu = simple_strtoul(str, NULL, 0);
655 if (cpu >= num_possible_cpus()) {
656 pr_err("Ignoring the CPU number in reboot= option. "
657 "CPU %d exceeds possible cpu number %d\n",
658 cpu, num_possible_cpus());
684 str = strchr(str, ',');
692 __setup("reboot=", reboot_setup);
696 #define REBOOT_COLD_STR "cold"
697 #define REBOOT_WARM_STR "warm"
698 #define REBOOT_HARD_STR "hard"
699 #define REBOOT_SOFT_STR "soft"
700 #define REBOOT_GPIO_STR "gpio"
701 #define REBOOT_UNDEFINED_STR "undefined"
703 #define BOOT_TRIPLE_STR "triple"
704 #define BOOT_KBD_STR "kbd"
705 #define BOOT_BIOS_STR "bios"
706 #define BOOT_ACPI_STR "acpi"
707 #define BOOT_EFI_STR "efi"
708 #define BOOT_PCI_STR "pci"
710 static ssize_t mode_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
714 switch (reboot_mode) {
716 val = REBOOT_COLD_STR;
719 val = REBOOT_WARM_STR;
722 val = REBOOT_HARD_STR;
725 val = REBOOT_SOFT_STR;
728 val = REBOOT_GPIO_STR;
731 val = REBOOT_UNDEFINED_STR;
734 return sprintf(buf, "%s\n", val);
736 static ssize_t mode_store(struct kobject *kobj, struct kobj_attribute *attr,
737 const char *buf, size_t count)
739 if (!capable(CAP_SYS_BOOT))
742 if (!strncmp(buf, REBOOT_COLD_STR, strlen(REBOOT_COLD_STR)))
743 reboot_mode = REBOOT_COLD;
744 else if (!strncmp(buf, REBOOT_WARM_STR, strlen(REBOOT_WARM_STR)))
745 reboot_mode = REBOOT_WARM;
746 else if (!strncmp(buf, REBOOT_HARD_STR, strlen(REBOOT_HARD_STR)))
747 reboot_mode = REBOOT_HARD;
748 else if (!strncmp(buf, REBOOT_SOFT_STR, strlen(REBOOT_SOFT_STR)))
749 reboot_mode = REBOOT_SOFT;
750 else if (!strncmp(buf, REBOOT_GPIO_STR, strlen(REBOOT_GPIO_STR)))
751 reboot_mode = REBOOT_GPIO;
759 static struct kobj_attribute reboot_mode_attr = __ATTR_RW(mode);
762 static ssize_t force_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
764 return sprintf(buf, "%d\n", reboot_force);
766 static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
767 const char *buf, size_t count)
771 if (!capable(CAP_SYS_BOOT))
774 if (kstrtobool(buf, &res))
782 static struct kobj_attribute reboot_force_attr = __ATTR_RW(force);
784 static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
788 switch (reboot_type) {
790 val = BOOT_TRIPLE_STR;
808 val = REBOOT_UNDEFINED_STR;
811 return sprintf(buf, "%s\n", val);
813 static ssize_t type_store(struct kobject *kobj, struct kobj_attribute *attr,
814 const char *buf, size_t count)
816 if (!capable(CAP_SYS_BOOT))
819 if (!strncmp(buf, BOOT_TRIPLE_STR, strlen(BOOT_TRIPLE_STR)))
820 reboot_type = BOOT_TRIPLE;
821 else if (!strncmp(buf, BOOT_KBD_STR, strlen(BOOT_KBD_STR)))
822 reboot_type = BOOT_KBD;
823 else if (!strncmp(buf, BOOT_BIOS_STR, strlen(BOOT_BIOS_STR)))
824 reboot_type = BOOT_BIOS;
825 else if (!strncmp(buf, BOOT_ACPI_STR, strlen(BOOT_ACPI_STR)))
826 reboot_type = BOOT_ACPI;
827 else if (!strncmp(buf, BOOT_EFI_STR, strlen(BOOT_EFI_STR)))
828 reboot_type = BOOT_EFI;
829 else if (!strncmp(buf, BOOT_PCI_STR, strlen(BOOT_PCI_STR)))
830 reboot_type = BOOT_CF9_FORCE;
838 static struct kobj_attribute reboot_type_attr = __ATTR_RW(type);
842 static ssize_t cpu_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
844 return sprintf(buf, "%d\n", reboot_cpu);
846 static ssize_t cpu_store(struct kobject *kobj, struct kobj_attribute *attr,
847 const char *buf, size_t count)
852 if (!capable(CAP_SYS_BOOT))
855 rc = kstrtouint(buf, 0, &cpunum);
860 if (cpunum >= num_possible_cpus())
868 static struct kobj_attribute reboot_cpu_attr = __ATTR_RW(cpu);
871 static struct attribute *reboot_attrs[] = {
872 &reboot_mode_attr.attr,
874 &reboot_force_attr.attr,
875 &reboot_type_attr.attr,
878 &reboot_cpu_attr.attr,
884 static struct ctl_table kern_reboot_table[] = {
886 .procname = "poweroff_cmd",
887 .data = &poweroff_cmd,
888 .maxlen = POWEROFF_CMD_PATH_LEN,
890 .proc_handler = proc_dostring,
893 .procname = "ctrl-alt-del",
895 .maxlen = sizeof(int),
897 .proc_handler = proc_dointvec,
902 static void __init kernel_reboot_sysctls_init(void)
904 register_sysctl_init("kernel", kern_reboot_table);
907 #define kernel_reboot_sysctls_init() do { } while (0)
908 #endif /* CONFIG_SYSCTL */
910 static const struct attribute_group reboot_attr_group = {
911 .attrs = reboot_attrs,
914 static int __init reboot_ksysfs_init(void)
916 struct kobject *reboot_kobj;
919 reboot_kobj = kobject_create_and_add("reboot", kernel_kobj);
923 ret = sysfs_create_group(reboot_kobj, &reboot_attr_group);
925 kobject_put(reboot_kobj);
929 kernel_reboot_sysctls_init();
933 late_initcall(reboot_ksysfs_init);