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 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 printk_prefer_direct_enter();
451 pr_warn("Failed to start orderly reboot: forcing the issue\n");
453 kernel_restart(NULL
);
454 printk_prefer_direct_exit();
460 static int __orderly_poweroff(bool force
)
464 ret
= run_cmd(poweroff_cmd
);
467 printk_prefer_direct_enter();
468 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
471 * I guess this should try to kick off some daemon to sync and
472 * poweroff asap. Or not even bother syncing if we're doing an
473 * emergency shutdown?
477 printk_prefer_direct_exit();
483 static bool poweroff_force
;
485 static void poweroff_work_func(struct work_struct
*work
)
487 __orderly_poweroff(poweroff_force
);
490 static DECLARE_WORK(poweroff_work
, poweroff_work_func
);
493 * orderly_poweroff - Trigger an orderly system poweroff
494 * @force: force poweroff if command execution fails
496 * This may be called from any context to trigger a system shutdown.
497 * If the orderly shutdown fails, it will force an immediate shutdown.
499 void orderly_poweroff(bool force
)
501 if (force
) /* do not override the pending "true" */
502 poweroff_force
= true;
503 schedule_work(&poweroff_work
);
505 EXPORT_SYMBOL_GPL(orderly_poweroff
);
507 static void reboot_work_func(struct work_struct
*work
)
512 static DECLARE_WORK(reboot_work
, reboot_work_func
);
515 * orderly_reboot - Trigger an orderly system reboot
517 * This may be called from any context to trigger a system reboot.
518 * If the orderly reboot fails, it will force an immediate reboot.
520 void orderly_reboot(void)
522 schedule_work(&reboot_work
);
524 EXPORT_SYMBOL_GPL(orderly_reboot
);
527 * hw_failure_emergency_poweroff_func - emergency poweroff work after a known delay
528 * @work: work_struct associated with the emergency poweroff function
530 * This function is called in very critical situations to force
531 * a kernel poweroff after a configurable timeout value.
533 static void hw_failure_emergency_poweroff_func(struct work_struct
*work
)
535 printk_prefer_direct_enter();
538 * We have reached here after the emergency shutdown waiting period has
539 * expired. This means orderly_poweroff has not been able to shut off
540 * the system for some reason.
542 * Try to shut down the system immediately using kernel_power_off
545 pr_emerg("Hardware protection timed-out. Trying forced poweroff\n");
549 * Worst of the worst case trigger emergency restart
551 pr_emerg("Hardware protection shutdown failed. Trying emergency restart\n");
554 printk_prefer_direct_exit();
557 static DECLARE_DELAYED_WORK(hw_failure_emergency_poweroff_work
,
558 hw_failure_emergency_poweroff_func
);
561 * hw_failure_emergency_poweroff - Trigger an emergency system poweroff
563 * This may be called from any critical situation to trigger a system shutdown
564 * after a given period of time. If time is negative this is not scheduled.
566 static void hw_failure_emergency_poweroff(int poweroff_delay_ms
)
568 if (poweroff_delay_ms
<= 0)
570 schedule_delayed_work(&hw_failure_emergency_poweroff_work
,
571 msecs_to_jiffies(poweroff_delay_ms
));
575 * hw_protection_shutdown - Trigger an emergency system poweroff
577 * @reason: Reason of emergency shutdown to be printed.
578 * @ms_until_forced: Time to wait for orderly shutdown before tiggering a
579 * forced shudown. Negative value disables the forced
582 * Initiate an emergency system shutdown in order to protect hardware from
583 * further damage. Usage examples include a thermal protection or a voltage or
584 * current regulator failures.
585 * NOTE: The request is ignored if protection shutdown is already pending even
586 * if the previous request has given a large timeout for forced shutdown.
587 * Can be called from any context.
589 void hw_protection_shutdown(const char *reason
, int ms_until_forced
)
591 static atomic_t allow_proceed
= ATOMIC_INIT(1);
593 printk_prefer_direct_enter();
595 pr_emerg("HARDWARE PROTECTION shutdown (%s)\n", reason
);
597 /* Shutdown should be initiated only once. */
598 if (!atomic_dec_and_test(&allow_proceed
))
602 * Queue a backup emergency shutdown in the event of
603 * orderly_poweroff failure
605 hw_failure_emergency_poweroff(ms_until_forced
);
606 orderly_poweroff(true);
608 printk_prefer_direct_exit();
610 EXPORT_SYMBOL_GPL(hw_protection_shutdown
);
612 static int __init
reboot_setup(char *str
)
615 enum reboot_mode
*mode
;
618 * Having anything passed on the command line via
619 * reboot= will cause us to disable DMI checking
624 if (!strncmp(str
, "panic_", 6)) {
625 mode
= &panic_reboot_mode
;
646 * reboot_cpu is s[mp]#### with #### being the processor
647 * to be used for rebooting. Skip 's' or 'smp' prefix.
649 str
+= str
[1] == 'm' && str
[2] == 'p' ? 3 : 1;
651 if (isdigit(str
[0])) {
652 int cpu
= simple_strtoul(str
, NULL
, 0);
654 if (cpu
>= num_possible_cpus()) {
655 pr_err("Ignoring the CPU number in reboot= option. "
656 "CPU %d exceeds possible cpu number %d\n",
657 cpu
, num_possible_cpus());
683 str
= strchr(str
, ',');
691 __setup("reboot=", reboot_setup
);
695 #define REBOOT_COLD_STR "cold"
696 #define REBOOT_WARM_STR "warm"
697 #define REBOOT_HARD_STR "hard"
698 #define REBOOT_SOFT_STR "soft"
699 #define REBOOT_GPIO_STR "gpio"
700 #define REBOOT_UNDEFINED_STR "undefined"
702 #define BOOT_TRIPLE_STR "triple"
703 #define BOOT_KBD_STR "kbd"
704 #define BOOT_BIOS_STR "bios"
705 #define BOOT_ACPI_STR "acpi"
706 #define BOOT_EFI_STR "efi"
707 #define BOOT_PCI_STR "pci"
709 static ssize_t
mode_show(struct kobject
*kobj
, struct kobj_attribute
*attr
, char *buf
)
713 switch (reboot_mode
) {
715 val
= REBOOT_COLD_STR
;
718 val
= REBOOT_WARM_STR
;
721 val
= REBOOT_HARD_STR
;
724 val
= REBOOT_SOFT_STR
;
727 val
= REBOOT_GPIO_STR
;
730 val
= REBOOT_UNDEFINED_STR
;
733 return sprintf(buf
, "%s\n", val
);
735 static ssize_t
mode_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
736 const char *buf
, size_t count
)
738 if (!capable(CAP_SYS_BOOT
))
741 if (!strncmp(buf
, REBOOT_COLD_STR
, strlen(REBOOT_COLD_STR
)))
742 reboot_mode
= REBOOT_COLD
;
743 else if (!strncmp(buf
, REBOOT_WARM_STR
, strlen(REBOOT_WARM_STR
)))
744 reboot_mode
= REBOOT_WARM
;
745 else if (!strncmp(buf
, REBOOT_HARD_STR
, strlen(REBOOT_HARD_STR
)))
746 reboot_mode
= REBOOT_HARD
;
747 else if (!strncmp(buf
, REBOOT_SOFT_STR
, strlen(REBOOT_SOFT_STR
)))
748 reboot_mode
= REBOOT_SOFT
;
749 else if (!strncmp(buf
, REBOOT_GPIO_STR
, strlen(REBOOT_GPIO_STR
)))
750 reboot_mode
= REBOOT_GPIO
;
758 static struct kobj_attribute reboot_mode_attr
= __ATTR_RW(mode
);
761 static ssize_t
force_show(struct kobject
*kobj
, struct kobj_attribute
*attr
, char *buf
)
763 return sprintf(buf
, "%d\n", reboot_force
);
765 static ssize_t
force_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
766 const char *buf
, size_t count
)
770 if (!capable(CAP_SYS_BOOT
))
773 if (kstrtobool(buf
, &res
))
781 static struct kobj_attribute reboot_force_attr
= __ATTR_RW(force
);
783 static ssize_t
type_show(struct kobject
*kobj
, struct kobj_attribute
*attr
, char *buf
)
787 switch (reboot_type
) {
789 val
= BOOT_TRIPLE_STR
;
807 val
= REBOOT_UNDEFINED_STR
;
810 return sprintf(buf
, "%s\n", val
);
812 static ssize_t
type_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
813 const char *buf
, size_t count
)
815 if (!capable(CAP_SYS_BOOT
))
818 if (!strncmp(buf
, BOOT_TRIPLE_STR
, strlen(BOOT_TRIPLE_STR
)))
819 reboot_type
= BOOT_TRIPLE
;
820 else if (!strncmp(buf
, BOOT_KBD_STR
, strlen(BOOT_KBD_STR
)))
821 reboot_type
= BOOT_KBD
;
822 else if (!strncmp(buf
, BOOT_BIOS_STR
, strlen(BOOT_BIOS_STR
)))
823 reboot_type
= BOOT_BIOS
;
824 else if (!strncmp(buf
, BOOT_ACPI_STR
, strlen(BOOT_ACPI_STR
)))
825 reboot_type
= BOOT_ACPI
;
826 else if (!strncmp(buf
, BOOT_EFI_STR
, strlen(BOOT_EFI_STR
)))
827 reboot_type
= BOOT_EFI
;
828 else if (!strncmp(buf
, BOOT_PCI_STR
, strlen(BOOT_PCI_STR
)))
829 reboot_type
= BOOT_CF9_FORCE
;
837 static struct kobj_attribute reboot_type_attr
= __ATTR_RW(type
);
841 static ssize_t
cpu_show(struct kobject
*kobj
, struct kobj_attribute
*attr
, char *buf
)
843 return sprintf(buf
, "%d\n", reboot_cpu
);
845 static ssize_t
cpu_store(struct kobject
*kobj
, struct kobj_attribute
*attr
,
846 const char *buf
, size_t count
)
851 if (!capable(CAP_SYS_BOOT
))
854 rc
= kstrtouint(buf
, 0, &cpunum
);
859 if (cpunum
>= num_possible_cpus())
867 static struct kobj_attribute reboot_cpu_attr
= __ATTR_RW(cpu
);
870 static struct attribute
*reboot_attrs
[] = {
871 &reboot_mode_attr
.attr
,
873 &reboot_force_attr
.attr
,
874 &reboot_type_attr
.attr
,
877 &reboot_cpu_attr
.attr
,
882 static const struct attribute_group reboot_attr_group
= {
883 .attrs
= reboot_attrs
,
886 static int __init
reboot_ksysfs_init(void)
888 struct kobject
*reboot_kobj
;
891 reboot_kobj
= kobject_create_and_add("reboot", kernel_kobj
);
895 ret
= sysfs_create_group(reboot_kobj
, &reboot_attr_group
);
897 kobject_put(reboot_kobj
);
903 late_initcall(reboot_ksysfs_init
);