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/ctype.h>
11 #include <linux/export.h>
12 #include <linux/kexec.h>
13 #include <linux/kmod.h>
14 #include <linux/kmsg_dump.h>
15 #include <linux/reboot.h>
16 #include <linux/suspend.h>
17 #include <linux/syscalls.h>
18 #include <linux/syscore_ops.h>
19 #include <linux/uaccess.h>
22 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
27 EXPORT_SYMBOL(cad_pid);
29 #if defined(CONFIG_ARM)
30 #define DEFAULT_REBOOT_MODE = REBOOT_HARD
32 #define DEFAULT_REBOOT_MODE
34 enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
35 enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
38 * This variable is used privately to keep track of whether or not
39 * reboot_type is still set to its default value (i.e., reboot= hasn't
40 * been set on the command line). This is needed so that we can
41 * suppress DMI scanning for reboot quirks. Without it, it's
42 * impossible to override a faulty reboot quirk without recompiling.
44 int reboot_default = 1;
46 enum reboot_type reboot_type = BOOT_ACPI;
50 * If set, this is used for preparing the system to power off.
53 void (*pm_power_off_prepare)(void);
54 EXPORT_SYMBOL_GPL(pm_power_off_prepare);
57 * emergency_restart - reboot the system
59 * Without shutting down any hardware or taking any locks
60 * reboot the system. This is called when we know we are in
61 * trouble so this is our best effort to reboot. This is
62 * safe to call in interrupt context.
64 void emergency_restart(void)
66 kmsg_dump(KMSG_DUMP_EMERG);
67 system_state = SYSTEM_RESTART;
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);
522 static int __init reboot_setup(char *str)
525 enum reboot_mode *mode;
528 * Having anything passed on the command line via
529 * reboot= will cause us to disable DMI checking
534 if (!strncmp(str, "panic_", 6)) {
535 mode = &panic_reboot_mode;
555 if (isdigit(*(str+1)))
556 reboot_cpu = simple_strtoul(str+1, NULL, 0);
557 else if (str[1] == 'm' && str[2] == 'p' &&
559 reboot_cpu = simple_strtoul(str+3, NULL, 0);
562 if (reboot_cpu >= num_possible_cpus()) {
563 pr_err("Ignoring the CPU number in reboot= option. "
564 "CPU %d exceeds possible cpu number %d\n",
565 reboot_cpu, num_possible_cpus());
589 str = strchr(str, ',');
597 __setup("reboot=", reboot_setup);