2 * linux/kernel/reboot.c
4 * Copyright (C) 2013 Linus Torvalds
7 #define pr_fmt(fmt) "reboot: " fmt
9 #include <linux/ctype.h>
10 #include <linux/export.h>
11 #include <linux/kexec.h>
12 #include <linux/kmod.h>
13 #include <linux/kmsg_dump.h>
14 #include <linux/reboot.h>
15 #include <linux/suspend.h>
16 #include <linux/syscalls.h>
17 #include <linux/syscore_ops.h>
18 #include <linux/uaccess.h>
21 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
26 EXPORT_SYMBOL(cad_pid);
28 #if defined(CONFIG_ARM) || defined(CONFIG_UNICORE32)
29 #define DEFAULT_REBOOT_MODE = REBOOT_HARD
31 #define DEFAULT_REBOOT_MODE
33 enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
34 enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
37 * This variable is used privately to keep track of whether or not
38 * reboot_type is still set to its default value (i.e., reboot= hasn't
39 * been set on the command line). This is needed so that we can
40 * suppress DMI scanning for reboot quirks. Without it, it's
41 * impossible to override a faulty reboot quirk without recompiling.
43 int reboot_default = 1;
45 enum reboot_type reboot_type = BOOT_ACPI;
49 * If set, this is used for preparing the system to power off.
52 void (*pm_power_off_prepare)(void);
53 EXPORT_SYMBOL_GPL(pm_power_off_prepare);
56 * emergency_restart - reboot the system
58 * Without shutting down any hardware or taking any locks
59 * reboot the system. This is called when we know we are in
60 * trouble so this is our best effort to reboot. This is
61 * safe to call in interrupt context.
63 void emergency_restart(void)
65 kmsg_dump(KMSG_DUMP_EMERG);
66 machine_emergency_restart();
68 EXPORT_SYMBOL_GPL(emergency_restart);
70 void kernel_restart_prepare(char *cmd)
72 blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
73 system_state = SYSTEM_RESTART;
74 usermodehelper_disable();
79 * register_reboot_notifier - Register function to be called at reboot time
80 * @nb: Info about notifier function to be called
82 * Registers a function with the list of functions
83 * to be called at reboot time.
85 * Currently always returns zero, as blocking_notifier_chain_register()
86 * always returns zero.
88 int register_reboot_notifier(struct notifier_block *nb)
90 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
92 EXPORT_SYMBOL(register_reboot_notifier);
95 * unregister_reboot_notifier - Unregister previously registered reboot notifier
96 * @nb: Hook to be unregistered
98 * Unregisters a previously registered reboot
101 * Returns zero on success, or %-ENOENT on failure.
103 int unregister_reboot_notifier(struct notifier_block *nb)
105 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
107 EXPORT_SYMBOL(unregister_reboot_notifier);
109 static void devm_unregister_reboot_notifier(struct device *dev, void *res)
111 WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
114 int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
116 struct notifier_block **rcnb;
119 rcnb = devres_alloc(devm_unregister_reboot_notifier,
120 sizeof(*rcnb), GFP_KERNEL);
124 ret = register_reboot_notifier(nb);
127 devres_add(dev, rcnb);
134 EXPORT_SYMBOL(devm_register_reboot_notifier);
137 * Notifier list for kernel code which wants to be called
138 * to restart the system.
140 static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
143 * register_restart_handler - Register function to be called to reset
145 * @nb: Info about handler function to be called
146 * @nb->priority: Handler priority. Handlers should follow the
147 * following guidelines for setting priorities.
148 * 0: Restart handler of last resort,
149 * with limited restart capabilities
150 * 128: Default restart handler; use if no other
151 * restart handler is expected to be available,
152 * and/or if restart functionality is
153 * sufficient to restart the entire system
154 * 255: Highest priority restart handler, will
155 * preempt all other restart handlers
157 * Registers a function with code to be called to restart the
160 * Registered functions will be called from machine_restart as last
161 * step of the restart sequence (if the architecture specific
162 * machine_restart function calls do_kernel_restart - see below
164 * Registered functions are expected to restart the system immediately.
165 * If more than one function is registered, the restart handler priority
166 * selects which function will be called first.
168 * Restart handlers are expected to be registered from non-architecture
169 * code, typically from drivers. A typical use case would be a system
170 * where restart functionality is provided through a watchdog. Multiple
171 * restart handlers may exist; for example, one restart handler might
172 * restart the entire system, while another only restarts the CPU.
173 * In such cases, the restart handler which only restarts part of the
174 * hardware is expected to register with low priority to ensure that
175 * it only runs if no other means to restart the system is available.
177 * Currently always returns zero, as atomic_notifier_chain_register()
178 * always returns zero.
180 int register_restart_handler(struct notifier_block *nb)
182 return atomic_notifier_chain_register(&restart_handler_list, nb);
184 EXPORT_SYMBOL(register_restart_handler);
187 * unregister_restart_handler - Unregister previously registered
189 * @nb: Hook to be unregistered
191 * Unregisters a previously registered restart handler function.
193 * Returns zero on success, or %-ENOENT on failure.
195 int unregister_restart_handler(struct notifier_block *nb)
197 return atomic_notifier_chain_unregister(&restart_handler_list, nb);
199 EXPORT_SYMBOL(unregister_restart_handler);
202 * do_kernel_restart - Execute kernel restart handler call chain
204 * Calls functions registered with register_restart_handler.
206 * Expected to be called from machine_restart as last step of the restart
209 * Restarts the system immediately if a restart handler function has been
210 * registered. Otherwise does nothing.
212 void do_kernel_restart(char *cmd)
214 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
217 void migrate_to_reboot_cpu(void)
219 /* The boot cpu is always logical cpu 0 */
220 int cpu = reboot_cpu;
222 cpu_hotplug_disable();
224 /* Make certain the cpu I'm about to reboot on is online */
225 if (!cpu_online(cpu))
226 cpu = cpumask_first(cpu_online_mask);
228 /* Prevent races with other tasks migrating this task */
229 current->flags |= PF_NO_SETAFFINITY;
231 /* Make certain I only run on the appropriate processor */
232 set_cpus_allowed_ptr(current, cpumask_of(cpu));
236 * kernel_restart - reboot the system
237 * @cmd: pointer to buffer containing command to execute for restart
240 * Shutdown everything and perform a clean reboot.
241 * This is not safe to call in interrupt context.
243 void kernel_restart(char *cmd)
245 kernel_restart_prepare(cmd);
246 migrate_to_reboot_cpu();
249 pr_emerg("Restarting system\n");
251 pr_emerg("Restarting system with command '%s'\n", cmd);
252 kmsg_dump(KMSG_DUMP_RESTART);
253 machine_restart(cmd);
255 EXPORT_SYMBOL_GPL(kernel_restart);
257 static void kernel_shutdown_prepare(enum system_states state)
259 blocking_notifier_call_chain(&reboot_notifier_list,
260 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
261 system_state = state;
262 usermodehelper_disable();
266 * kernel_halt - halt the system
268 * Shutdown everything and perform a clean system halt.
270 void kernel_halt(void)
272 kernel_shutdown_prepare(SYSTEM_HALT);
273 migrate_to_reboot_cpu();
275 pr_emerg("System halted\n");
276 kmsg_dump(KMSG_DUMP_HALT);
279 EXPORT_SYMBOL_GPL(kernel_halt);
282 * kernel_power_off - power_off the system
284 * Shutdown everything and perform a clean system power_off.
286 void kernel_power_off(void)
288 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
289 if (pm_power_off_prepare)
290 pm_power_off_prepare();
291 migrate_to_reboot_cpu();
293 pr_emerg("Power down\n");
294 kmsg_dump(KMSG_DUMP_POWEROFF);
297 EXPORT_SYMBOL_GPL(kernel_power_off);
299 DEFINE_MUTEX(system_transition_mutex);
302 * Reboot system call: for obvious reasons only root may call it,
303 * and even root needs to set up some magic numbers in the registers
304 * so that some mistake won't make this reboot the whole machine.
305 * You can also set the meaning of the ctrl-alt-del-key here.
307 * reboot doesn't sync: do that yourself before calling this.
309 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
312 struct pid_namespace *pid_ns = task_active_pid_ns(current);
316 /* We only trust the superuser with rebooting the system. */
317 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
320 /* For safety, we require "magic" arguments. */
321 if (magic1 != LINUX_REBOOT_MAGIC1 ||
322 (magic2 != LINUX_REBOOT_MAGIC2 &&
323 magic2 != LINUX_REBOOT_MAGIC2A &&
324 magic2 != LINUX_REBOOT_MAGIC2B &&
325 magic2 != LINUX_REBOOT_MAGIC2C))
329 * If pid namespaces are enabled and the current task is in a child
330 * pid_namespace, the command is handled by reboot_pid_ns() which will
333 ret = reboot_pid_ns(pid_ns, cmd);
337 /* Instead of trying to make the power_off code look like
338 * halt when pm_power_off is not set do it the easy way.
340 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
341 cmd = LINUX_REBOOT_CMD_HALT;
343 mutex_lock(&system_transition_mutex);
345 case LINUX_REBOOT_CMD_RESTART:
346 kernel_restart(NULL);
349 case LINUX_REBOOT_CMD_CAD_ON:
353 case LINUX_REBOOT_CMD_CAD_OFF:
357 case LINUX_REBOOT_CMD_HALT:
360 panic("cannot halt");
362 case LINUX_REBOOT_CMD_POWER_OFF:
367 case LINUX_REBOOT_CMD_RESTART2:
368 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
373 buffer[sizeof(buffer) - 1] = '\0';
375 kernel_restart(buffer);
378 #ifdef CONFIG_KEXEC_CORE
379 case LINUX_REBOOT_CMD_KEXEC:
380 ret = kernel_kexec();
384 #ifdef CONFIG_HIBERNATION
385 case LINUX_REBOOT_CMD_SW_SUSPEND:
394 mutex_unlock(&system_transition_mutex);
398 static void deferred_cad(struct work_struct *dummy)
400 kernel_restart(NULL);
404 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
405 * As it's called within an interrupt, it may NOT sync: the only choice
406 * is whether to reboot at once, or just ignore the ctrl-alt-del.
408 void ctrl_alt_del(void)
410 static DECLARE_WORK(cad_work, deferred_cad);
413 schedule_work(&cad_work);
415 kill_cad_pid(SIGINT, 1);
418 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
419 static const char reboot_cmd[] = "/sbin/reboot";
421 static int run_cmd(const char *cmd)
424 static char *envp[] = {
426 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
430 argv = argv_split(GFP_KERNEL, cmd, NULL);
432 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
441 static int __orderly_reboot(void)
445 ret = run_cmd(reboot_cmd);
448 pr_warn("Failed to start orderly reboot: forcing the issue\n");
450 kernel_restart(NULL);
456 static int __orderly_poweroff(bool force)
460 ret = run_cmd(poweroff_cmd);
463 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
466 * I guess this should try to kick off some daemon to sync and
467 * poweroff asap. Or not even bother syncing if we're doing an
468 * emergency shutdown?
477 static bool poweroff_force;
479 static void poweroff_work_func(struct work_struct *work)
481 __orderly_poweroff(poweroff_force);
484 static DECLARE_WORK(poweroff_work, poweroff_work_func);
487 * orderly_poweroff - Trigger an orderly system poweroff
488 * @force: force poweroff if command execution fails
490 * This may be called from any context to trigger a system shutdown.
491 * If the orderly shutdown fails, it will force an immediate shutdown.
493 void orderly_poweroff(bool force)
495 if (force) /* do not override the pending "true" */
496 poweroff_force = true;
497 schedule_work(&poweroff_work);
499 EXPORT_SYMBOL_GPL(orderly_poweroff);
501 static void reboot_work_func(struct work_struct *work)
506 static DECLARE_WORK(reboot_work, reboot_work_func);
509 * orderly_reboot - Trigger an orderly system reboot
511 * This may be called from any context to trigger a system reboot.
512 * If the orderly reboot fails, it will force an immediate reboot.
514 void orderly_reboot(void)
516 schedule_work(&reboot_work);
518 EXPORT_SYMBOL_GPL(orderly_reboot);
520 static int __init reboot_setup(char *str)
523 enum reboot_mode *mode;
526 * Having anything passed on the command line via
527 * reboot= will cause us to disable DMI checking
532 if (!strncmp(str, "panic_", 6)) {
533 mode = &panic_reboot_mode;
556 if (isdigit(*(str+1))) {
557 rc = kstrtoint(str+1, 0, &reboot_cpu);
560 } else if (str[1] == 'm' && str[2] == 'p' &&
562 rc = kstrtoint(str+3, 0, &reboot_cpu);
587 str = strchr(str, ',');
595 __setup("reboot=", reboot_setup);