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;
36 * This variable is used privately to keep track of whether or not
37 * reboot_type is still set to its default value (i.e., reboot= hasn't
38 * been set on the command line). This is needed so that we can
39 * suppress DMI scanning for reboot quirks. Without it, it's
40 * impossible to override a faulty reboot quirk without recompiling.
42 int reboot_default = 1;
44 enum reboot_type reboot_type = BOOT_ACPI;
48 * If set, this is used for preparing the system to power off.
51 void (*pm_power_off_prepare)(void);
54 * emergency_restart - reboot the system
56 * Without shutting down any hardware or taking any locks
57 * reboot the system. This is called when we know we are in
58 * trouble so this is our best effort to reboot. This is
59 * safe to call in interrupt context.
61 void emergency_restart(void)
63 kmsg_dump(KMSG_DUMP_EMERG);
64 machine_emergency_restart();
66 EXPORT_SYMBOL_GPL(emergency_restart);
68 void kernel_restart_prepare(char *cmd)
70 blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
71 system_state = SYSTEM_RESTART;
72 usermodehelper_disable();
77 * register_reboot_notifier - Register function to be called at reboot time
78 * @nb: Info about notifier function to be called
80 * Registers a function with the list of functions
81 * to be called at reboot time.
83 * Currently always returns zero, as blocking_notifier_chain_register()
84 * always returns zero.
86 int register_reboot_notifier(struct notifier_block *nb)
88 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
90 EXPORT_SYMBOL(register_reboot_notifier);
93 * unregister_reboot_notifier - Unregister previously registered reboot notifier
94 * @nb: Hook to be unregistered
96 * Unregisters a previously registered reboot
99 * Returns zero on success, or %-ENOENT on failure.
101 int unregister_reboot_notifier(struct notifier_block *nb)
103 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
105 EXPORT_SYMBOL(unregister_reboot_notifier);
108 * Notifier list for kernel code which wants to be called
109 * to restart the system.
111 static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
114 * register_restart_handler - Register function to be called to reset
116 * @nb: Info about handler function to be called
117 * @nb->priority: Handler priority. Handlers should follow the
118 * following guidelines for setting priorities.
119 * 0: Restart handler of last resort,
120 * with limited restart capabilities
121 * 128: Default restart handler; use if no other
122 * restart handler is expected to be available,
123 * and/or if restart functionality is
124 * sufficient to restart the entire system
125 * 255: Highest priority restart handler, will
126 * preempt all other restart handlers
128 * Registers a function with code to be called to restart the
131 * Registered functions will be called from machine_restart as last
132 * step of the restart sequence (if the architecture specific
133 * machine_restart function calls do_kernel_restart - see below
135 * Registered functions are expected to restart the system immediately.
136 * If more than one function is registered, the restart handler priority
137 * selects which function will be called first.
139 * Restart handlers are expected to be registered from non-architecture
140 * code, typically from drivers. A typical use case would be a system
141 * where restart functionality is provided through a watchdog. Multiple
142 * restart handlers may exist; for example, one restart handler might
143 * restart the entire system, while another only restarts the CPU.
144 * In such cases, the restart handler which only restarts part of the
145 * hardware is expected to register with low priority to ensure that
146 * it only runs if no other means to restart the system is available.
148 * Currently always returns zero, as atomic_notifier_chain_register()
149 * always returns zero.
151 int register_restart_handler(struct notifier_block *nb)
153 return atomic_notifier_chain_register(&restart_handler_list, nb);
155 EXPORT_SYMBOL(register_restart_handler);
158 * unregister_restart_handler - Unregister previously registered
160 * @nb: Hook to be unregistered
162 * Unregisters a previously registered restart handler function.
164 * Returns zero on success, or %-ENOENT on failure.
166 int unregister_restart_handler(struct notifier_block *nb)
168 return atomic_notifier_chain_unregister(&restart_handler_list, nb);
170 EXPORT_SYMBOL(unregister_restart_handler);
173 * do_kernel_restart - Execute kernel restart handler call chain
175 * Calls functions registered with register_restart_handler.
177 * Expected to be called from machine_restart as last step of the restart
180 * Restarts the system immediately if a restart handler function has been
181 * registered. Otherwise does nothing.
183 void do_kernel_restart(char *cmd)
185 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
188 static ATOMIC_NOTIFIER_HEAD(i2c_restart_handler_list);
190 int register_i2c_restart_handler(struct notifier_block *nb)
192 return atomic_notifier_chain_register(&i2c_restart_handler_list, nb);
194 EXPORT_SYMBOL(register_i2c_restart_handler);
196 int unregister_i2c_restart_handler(struct notifier_block *nb)
198 return atomic_notifier_chain_unregister(&i2c_restart_handler_list, nb);
200 EXPORT_SYMBOL(unregister_i2c_restart_handler);
202 void do_kernel_i2c_restart(char *cmd)
204 atomic_notifier_call_chain(&i2c_restart_handler_list, reboot_mode, cmd);
207 void migrate_to_reboot_cpu(void)
209 /* The boot cpu is always logical cpu 0 */
210 int cpu = reboot_cpu;
212 cpu_hotplug_disable();
214 /* Make certain the cpu I'm about to reboot on is online */
215 if (!cpu_online(cpu))
216 cpu = cpumask_first(cpu_online_mask);
218 /* Prevent races with other tasks migrating this task */
219 current->flags |= PF_NO_SETAFFINITY;
221 /* Make certain I only run on the appropriate processor */
222 set_cpus_allowed_ptr(current, cpumask_of(cpu));
226 * kernel_restart - reboot the system
227 * @cmd: pointer to buffer containing command to execute for restart
230 * Shutdown everything and perform a clean reboot.
231 * This is not safe to call in interrupt context.
233 void kernel_restart(char *cmd)
235 kernel_restart_prepare(cmd);
236 migrate_to_reboot_cpu();
239 pr_emerg("Restarting system\n");
241 pr_emerg("Restarting system with command '%s'\n", cmd);
242 kmsg_dump(KMSG_DUMP_RESTART);
243 machine_restart(cmd);
245 EXPORT_SYMBOL_GPL(kernel_restart);
247 static void kernel_shutdown_prepare(enum system_states state)
249 blocking_notifier_call_chain(&reboot_notifier_list,
250 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
251 system_state = state;
252 usermodehelper_disable();
256 * kernel_halt - halt the system
258 * Shutdown everything and perform a clean system halt.
260 void kernel_halt(void)
262 kernel_shutdown_prepare(SYSTEM_HALT);
263 migrate_to_reboot_cpu();
265 pr_emerg("System halted\n");
266 kmsg_dump(KMSG_DUMP_HALT);
269 EXPORT_SYMBOL_GPL(kernel_halt);
272 * kernel_power_off - power_off the system
274 * Shutdown everything and perform a clean system power_off.
276 void kernel_power_off(void)
278 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
279 if (pm_power_off_prepare)
280 pm_power_off_prepare();
281 migrate_to_reboot_cpu();
283 pr_emerg("Power down\n");
284 kmsg_dump(KMSG_DUMP_POWEROFF);
287 EXPORT_SYMBOL_GPL(kernel_power_off);
289 static DEFINE_MUTEX(reboot_mutex);
292 * Reboot system call: for obvious reasons only root may call it,
293 * and even root needs to set up some magic numbers in the registers
294 * so that some mistake won't make this reboot the whole machine.
295 * You can also set the meaning of the ctrl-alt-del-key here.
297 * reboot doesn't sync: do that yourself before calling this.
299 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
302 struct pid_namespace *pid_ns = task_active_pid_ns(current);
306 /* We only trust the superuser with rebooting the system. */
307 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
310 /* For safety, we require "magic" arguments. */
311 if (magic1 != LINUX_REBOOT_MAGIC1 ||
312 (magic2 != LINUX_REBOOT_MAGIC2 &&
313 magic2 != LINUX_REBOOT_MAGIC2A &&
314 magic2 != LINUX_REBOOT_MAGIC2B &&
315 magic2 != LINUX_REBOOT_MAGIC2C))
319 * If pid namespaces are enabled and the current task is in a child
320 * pid_namespace, the command is handled by reboot_pid_ns() which will
323 ret = reboot_pid_ns(pid_ns, cmd);
327 /* Instead of trying to make the power_off code look like
328 * halt when pm_power_off is not set do it the easy way.
330 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
331 cmd = LINUX_REBOOT_CMD_HALT;
333 mutex_lock(&reboot_mutex);
335 case LINUX_REBOOT_CMD_RESTART:
336 kernel_restart(NULL);
339 case LINUX_REBOOT_CMD_CAD_ON:
343 case LINUX_REBOOT_CMD_CAD_OFF:
347 case LINUX_REBOOT_CMD_HALT:
350 panic("cannot halt");
352 case LINUX_REBOOT_CMD_POWER_OFF:
357 case LINUX_REBOOT_CMD_RESTART2:
358 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
363 buffer[sizeof(buffer) - 1] = '\0';
365 kernel_restart(buffer);
368 #ifdef CONFIG_KEXEC_CORE
369 case LINUX_REBOOT_CMD_KEXEC:
370 ret = kernel_kexec();
374 #ifdef CONFIG_HIBERNATION
375 case LINUX_REBOOT_CMD_SW_SUSPEND:
384 mutex_unlock(&reboot_mutex);
388 static void deferred_cad(struct work_struct *dummy)
390 kernel_restart(NULL);
394 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
395 * As it's called within an interrupt, it may NOT sync: the only choice
396 * is whether to reboot at once, or just ignore the ctrl-alt-del.
398 void ctrl_alt_del(void)
400 static DECLARE_WORK(cad_work, deferred_cad);
403 schedule_work(&cad_work);
405 kill_cad_pid(SIGINT, 1);
408 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
409 static const char reboot_cmd[] = "/sbin/reboot";
411 static int run_cmd(const char *cmd)
414 static char *envp[] = {
416 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
420 argv = argv_split(GFP_KERNEL, cmd, NULL);
422 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
431 static int __orderly_reboot(void)
435 ret = run_cmd(reboot_cmd);
438 pr_warn("Failed to start orderly reboot: forcing the issue\n");
440 kernel_restart(NULL);
446 static int __orderly_poweroff(bool force)
450 ret = run_cmd(poweroff_cmd);
453 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
456 * I guess this should try to kick off some daemon to sync and
457 * poweroff asap. Or not even bother syncing if we're doing an
458 * emergency shutdown?
467 static bool poweroff_force;
469 static void poweroff_work_func(struct work_struct *work)
471 __orderly_poweroff(poweroff_force);
474 static DECLARE_WORK(poweroff_work, poweroff_work_func);
477 * orderly_poweroff - Trigger an orderly system poweroff
478 * @force: force poweroff if command execution fails
480 * This may be called from any context to trigger a system shutdown.
481 * If the orderly shutdown fails, it will force an immediate shutdown.
483 void orderly_poweroff(bool force)
485 if (force) /* do not override the pending "true" */
486 poweroff_force = true;
487 schedule_work(&poweroff_work);
489 EXPORT_SYMBOL_GPL(orderly_poweroff);
491 static void reboot_work_func(struct work_struct *work)
496 static DECLARE_WORK(reboot_work, reboot_work_func);
499 * orderly_reboot - Trigger an orderly system reboot
501 * This may be called from any context to trigger a system reboot.
502 * If the orderly reboot fails, it will force an immediate reboot.
504 void orderly_reboot(void)
506 schedule_work(&reboot_work);
508 EXPORT_SYMBOL_GPL(orderly_reboot);
510 static int __init reboot_setup(char *str)
514 * Having anything passed on the command line via
515 * reboot= will cause us to disable DMI checking
522 reboot_mode = REBOOT_WARM;
526 reboot_mode = REBOOT_COLD;
530 reboot_mode = REBOOT_HARD;
537 if (isdigit(*(str+1))) {
538 rc = kstrtoint(str+1, 0, &reboot_cpu);
541 } else if (str[1] == 'm' && str[2] == 'p' &&
543 rc = kstrtoint(str+3, 0, &reboot_cpu);
547 reboot_mode = REBOOT_SOFT;
551 reboot_mode = REBOOT_GPIO;
568 str = strchr(str, ',');
576 __setup("reboot=", reboot_setup);