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
:
362 panic("cannot 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 char poweroff_cmd
[POWEROFF_CMD_PATH_LEN
] = "/sbin/poweroff";
421 static const char reboot_cmd
[] = "/sbin/reboot";
423 static int run_cmd(const char *cmd
)
426 static char *envp
[] = {
428 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
432 argv
= argv_split(GFP_KERNEL
, cmd
, NULL
);
434 ret
= call_usermodehelper(argv
[0], argv
, envp
, UMH_WAIT_EXEC
);
443 static int __orderly_reboot(void)
447 ret
= run_cmd(reboot_cmd
);
450 pr_warn("Failed to start orderly reboot: forcing the issue\n");
452 kernel_restart(NULL
);
458 static int __orderly_poweroff(bool force
)
462 ret
= run_cmd(poweroff_cmd
);
465 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
468 * I guess this should try to kick off some daemon to sync and
469 * poweroff asap. Or not even bother syncing if we're doing an
470 * emergency shutdown?
479 static bool poweroff_force
;
481 static void poweroff_work_func(struct work_struct
*work
)
483 __orderly_poweroff(poweroff_force
);
486 static DECLARE_WORK(poweroff_work
, poweroff_work_func
);
489 * orderly_poweroff - Trigger an orderly system poweroff
490 * @force: force poweroff if command execution fails
492 * This may be called from any context to trigger a system shutdown.
493 * If the orderly shutdown fails, it will force an immediate shutdown.
495 void orderly_poweroff(bool force
)
497 if (force
) /* do not override the pending "true" */
498 poweroff_force
= true;
499 schedule_work(&poweroff_work
);
501 EXPORT_SYMBOL_GPL(orderly_poweroff
);
503 static void reboot_work_func(struct work_struct
*work
)
508 static DECLARE_WORK(reboot_work
, reboot_work_func
);
511 * orderly_reboot - Trigger an orderly system reboot
513 * This may be called from any context to trigger a system reboot.
514 * If the orderly reboot fails, it will force an immediate reboot.
516 void orderly_reboot(void)
518 schedule_work(&reboot_work
);
520 EXPORT_SYMBOL_GPL(orderly_reboot
);
523 * hw_failure_emergency_poweroff_func - emergency poweroff work after a known delay
524 * @work: work_struct associated with the emergency poweroff function
526 * This function is called in very critical situations to force
527 * a kernel poweroff after a configurable timeout value.
529 static void hw_failure_emergency_poweroff_func(struct work_struct
*work
)
532 * We have reached here after the emergency shutdown waiting period has
533 * expired. This means orderly_poweroff has not been able to shut off
534 * the system for some reason.
536 * Try to shut down the system immediately using kernel_power_off
539 pr_emerg("Hardware protection timed-out. Trying forced poweroff\n");
543 * Worst of the worst case trigger emergency restart
545 pr_emerg("Hardware protection shutdown failed. Trying emergency restart\n");
549 static DECLARE_DELAYED_WORK(hw_failure_emergency_poweroff_work
,
550 hw_failure_emergency_poweroff_func
);
553 * hw_failure_emergency_poweroff - Trigger an emergency system poweroff
555 * This may be called from any critical situation to trigger a system shutdown
556 * after a given period of time. If time is negative this is not scheduled.
558 static void hw_failure_emergency_poweroff(int poweroff_delay_ms
)
560 if (poweroff_delay_ms
<= 0)
562 schedule_delayed_work(&hw_failure_emergency_poweroff_work
,
563 msecs_to_jiffies(poweroff_delay_ms
));
567 * hw_protection_shutdown - Trigger an emergency system poweroff
569 * @reason: Reason of emergency shutdown to be printed.
570 * @ms_until_forced: Time to wait for orderly shutdown before tiggering a
571 * forced shudown. Negative value disables the forced
574 * Initiate an emergency system shutdown in order to protect hardware from
575 * further damage. Usage examples include a thermal protection or a voltage or
576 * current regulator failures.
577 * NOTE: The request is ignored if protection shutdown is already pending even
578 * if the previous request has given a large timeout for forced shutdown.
579 * Can be called from any context.
581 void hw_protection_shutdown(const char *reason
, int ms_until_forced
)
583 static atomic_t allow_proceed
= ATOMIC_INIT(1);
585 pr_emerg("HARDWARE PROTECTION shutdown (%s)\n", reason
);
587 /* Shutdown should be initiated only once. */
588 if (!atomic_dec_and_test(&allow_proceed
))
592 * Queue a backup emergency shutdown in the event of
593 * orderly_poweroff failure
595 hw_failure_emergency_poweroff(ms_until_forced
);
596 orderly_poweroff(true);
598 EXPORT_SYMBOL_GPL(hw_protection_shutdown
);
600 static int __init
reboot_setup(char *str
)
603 enum reboot_mode
*mode
;
606 * Having anything passed on the command line via
607 * reboot= will cause us to disable DMI checking
612 if (!strncmp(str
, "panic_", 6)) {
613 mode
= &panic_reboot_mode
;
634 * reboot_cpu is s[mp]#### with #### being the processor
635 * to be used for rebooting. Skip 's' or 'smp' prefix.
637 str
+= str
[1] == 'm' && str
[2] == 'p' ? 3 : 1;
639 if (isdigit(str
[0])) {
640 int cpu
= simple_strtoul(str
, NULL
, 0);
642 if (cpu
>= num_possible_cpus()) {
643 pr_err("Ignoring the CPU number in reboot= option. "
644 "CPU %d exceeds possible cpu number %d\n",
645 cpu
, num_possible_cpus());
671 str
= strchr(str
, ',');
679 __setup("reboot=", reboot_setup
);
683 #define REBOOT_COLD_STR "cold"
684 #define REBOOT_WARM_STR "warm"
685 #define REBOOT_HARD_STR "hard"
686 #define REBOOT_SOFT_STR "soft"
687 #define REBOOT_GPIO_STR "gpio"
688 #define REBOOT_UNDEFINED_STR "undefined"
690 #define BOOT_TRIPLE_STR "triple"
691 #define BOOT_KBD_STR "kbd"
692 #define BOOT_BIOS_STR "bios"
693 #define BOOT_ACPI_STR "acpi"
694 #define BOOT_EFI_STR "efi"
695 #define BOOT_PCI_STR "pci"
697 static ssize_t
mode_show(struct kobject
*kobj
, struct kobj_attribute
*attr
, char *buf
)
701 switch (reboot_mode
) {
703 val
= REBOOT_COLD_STR
;
706 val
= REBOOT_WARM_STR
;
709 val
= REBOOT_HARD_STR
;
712 val
= REBOOT_SOFT_STR
;
715 val
= REBOOT_GPIO_STR
;
718 val
= REBOOT_UNDEFINED_STR
;
721 return sprintf(buf
, "%s\n", val
);
723 static ssize_t
mode_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
724 const char *buf
, size_t count
)
726 if (!capable(CAP_SYS_BOOT
))
729 if (!strncmp(buf
, REBOOT_COLD_STR
, strlen(REBOOT_COLD_STR
)))
730 reboot_mode
= REBOOT_COLD
;
731 else if (!strncmp(buf
, REBOOT_WARM_STR
, strlen(REBOOT_WARM_STR
)))
732 reboot_mode
= REBOOT_WARM
;
733 else if (!strncmp(buf
, REBOOT_HARD_STR
, strlen(REBOOT_HARD_STR
)))
734 reboot_mode
= REBOOT_HARD
;
735 else if (!strncmp(buf
, REBOOT_SOFT_STR
, strlen(REBOOT_SOFT_STR
)))
736 reboot_mode
= REBOOT_SOFT
;
737 else if (!strncmp(buf
, REBOOT_GPIO_STR
, strlen(REBOOT_GPIO_STR
)))
738 reboot_mode
= REBOOT_GPIO
;
746 static struct kobj_attribute reboot_mode_attr
= __ATTR_RW(mode
);
749 static ssize_t
force_show(struct kobject
*kobj
, struct kobj_attribute
*attr
, char *buf
)
751 return sprintf(buf
, "%d\n", reboot_force
);
753 static ssize_t
force_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
754 const char *buf
, size_t count
)
758 if (!capable(CAP_SYS_BOOT
))
761 if (kstrtobool(buf
, &res
))
769 static struct kobj_attribute reboot_force_attr
= __ATTR_RW(force
);
771 static ssize_t
type_show(struct kobject
*kobj
, struct kobj_attribute
*attr
, char *buf
)
775 switch (reboot_type
) {
777 val
= BOOT_TRIPLE_STR
;
795 val
= REBOOT_UNDEFINED_STR
;
798 return sprintf(buf
, "%s\n", val
);
800 static ssize_t
type_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
801 const char *buf
, size_t count
)
803 if (!capable(CAP_SYS_BOOT
))
806 if (!strncmp(buf
, BOOT_TRIPLE_STR
, strlen(BOOT_TRIPLE_STR
)))
807 reboot_type
= BOOT_TRIPLE
;
808 else if (!strncmp(buf
, BOOT_KBD_STR
, strlen(BOOT_KBD_STR
)))
809 reboot_type
= BOOT_KBD
;
810 else if (!strncmp(buf
, BOOT_BIOS_STR
, strlen(BOOT_BIOS_STR
)))
811 reboot_type
= BOOT_BIOS
;
812 else if (!strncmp(buf
, BOOT_ACPI_STR
, strlen(BOOT_ACPI_STR
)))
813 reboot_type
= BOOT_ACPI
;
814 else if (!strncmp(buf
, BOOT_EFI_STR
, strlen(BOOT_EFI_STR
)))
815 reboot_type
= BOOT_EFI
;
816 else if (!strncmp(buf
, BOOT_PCI_STR
, strlen(BOOT_PCI_STR
)))
817 reboot_type
= BOOT_CF9_FORCE
;
825 static struct kobj_attribute reboot_type_attr
= __ATTR_RW(type
);
829 static ssize_t
cpu_show(struct kobject
*kobj
, struct kobj_attribute
*attr
, char *buf
)
831 return sprintf(buf
, "%d\n", reboot_cpu
);
833 static ssize_t
cpu_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
834 const char *buf
, size_t count
)
839 if (!capable(CAP_SYS_BOOT
))
842 rc
= kstrtouint(buf
, 0, &cpunum
);
847 if (cpunum
>= num_possible_cpus())
855 static struct kobj_attribute reboot_cpu_attr
= __ATTR_RW(cpu
);
858 static struct attribute
*reboot_attrs
[] = {
859 &reboot_mode_attr
.attr
,
861 &reboot_force_attr
.attr
,
862 &reboot_type_attr
.attr
,
865 &reboot_cpu_attr
.attr
,
870 static const struct attribute_group reboot_attr_group
= {
871 .attrs
= reboot_attrs
,
874 static int __init
reboot_ksysfs_init(void)
876 struct kobject
*reboot_kobj
;
879 reboot_kobj
= kobject_create_and_add("reboot", kernel_kobj
);
883 ret
= sysfs_create_group(reboot_kobj
, &reboot_attr_group
);
885 kobject_put(reboot_kobj
);
891 late_initcall(reboot_ksysfs_init
);