2 * linux/kernel/reboot.c
4 * Copyright (C) 2013 Linus Torvalds
7 #define pr_fmt(fmt) "reboot: " fmt
9 #include <linux/export.h>
10 #include <linux/kexec.h>
11 #include <linux/kmod.h>
12 #include <linux/kmsg_dump.h>
13 #include <linux/reboot.h>
14 #include <linux/suspend.h>
15 #include <linux/syscalls.h>
16 #include <linux/syscore_ops.h>
17 #include <linux/uaccess.h>
20 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
25 EXPORT_SYMBOL(cad_pid);
28 * If set, this is used for preparing the system to power off.
31 void (*pm_power_off_prepare)(void);
34 * emergency_restart - reboot the system
36 * Without shutting down any hardware or taking any locks
37 * reboot the system. This is called when we know we are in
38 * trouble so this is our best effort to reboot. This is
39 * safe to call in interrupt context.
41 void emergency_restart(void)
43 kmsg_dump(KMSG_DUMP_EMERG);
44 machine_emergency_restart();
46 EXPORT_SYMBOL_GPL(emergency_restart);
48 void kernel_restart_prepare(char *cmd)
50 blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
51 system_state = SYSTEM_RESTART;
52 usermodehelper_disable();
57 * register_reboot_notifier - Register function to be called at reboot time
58 * @nb: Info about notifier function to be called
60 * Registers a function with the list of functions
61 * to be called at reboot time.
63 * Currently always returns zero, as blocking_notifier_chain_register()
64 * always returns zero.
66 int register_reboot_notifier(struct notifier_block *nb)
68 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
70 EXPORT_SYMBOL(register_reboot_notifier);
73 * unregister_reboot_notifier - Unregister previously registered reboot notifier
74 * @nb: Hook to be unregistered
76 * Unregisters a previously registered reboot
79 * Returns zero on success, or %-ENOENT on failure.
81 int unregister_reboot_notifier(struct notifier_block *nb)
83 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
85 EXPORT_SYMBOL(unregister_reboot_notifier);
87 static void migrate_to_reboot_cpu(void)
89 /* The boot cpu is always logical cpu 0 */
92 cpu_hotplug_disable();
94 /* Make certain the cpu I'm about to reboot on is online */
96 cpu = cpumask_first(cpu_online_mask);
98 /* Prevent races with other tasks migrating this task */
99 current->flags |= PF_NO_SETAFFINITY;
101 /* Make certain I only run on the appropriate processor */
102 set_cpus_allowed_ptr(current, cpumask_of(cpu));
106 * kernel_restart - reboot the system
107 * @cmd: pointer to buffer containing command to execute for restart
110 * Shutdown everything and perform a clean reboot.
111 * This is not safe to call in interrupt context.
113 void kernel_restart(char *cmd)
115 kernel_restart_prepare(cmd);
116 migrate_to_reboot_cpu();
119 pr_emerg("Restarting system\n");
121 pr_emerg("Restarting system with command '%s'\n", cmd);
122 kmsg_dump(KMSG_DUMP_RESTART);
123 machine_restart(cmd);
125 EXPORT_SYMBOL_GPL(kernel_restart);
127 static void kernel_shutdown_prepare(enum system_states state)
129 blocking_notifier_call_chain(&reboot_notifier_list,
130 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
131 system_state = state;
132 usermodehelper_disable();
136 * kernel_halt - halt the system
138 * Shutdown everything and perform a clean system halt.
140 void kernel_halt(void)
142 kernel_shutdown_prepare(SYSTEM_HALT);
143 migrate_to_reboot_cpu();
145 pr_emerg("System halted\n");
146 kmsg_dump(KMSG_DUMP_HALT);
149 EXPORT_SYMBOL_GPL(kernel_halt);
152 * kernel_power_off - power_off the system
154 * Shutdown everything and perform a clean system power_off.
156 void kernel_power_off(void)
158 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
159 if (pm_power_off_prepare)
160 pm_power_off_prepare();
161 migrate_to_reboot_cpu();
163 pr_emerg("Power down\n");
164 kmsg_dump(KMSG_DUMP_POWEROFF);
167 EXPORT_SYMBOL_GPL(kernel_power_off);
169 static DEFINE_MUTEX(reboot_mutex);
172 * Reboot system call: for obvious reasons only root may call it,
173 * and even root needs to set up some magic numbers in the registers
174 * so that some mistake won't make this reboot the whole machine.
175 * You can also set the meaning of the ctrl-alt-del-key here.
177 * reboot doesn't sync: do that yourself before calling this.
179 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
182 struct pid_namespace *pid_ns = task_active_pid_ns(current);
186 /* We only trust the superuser with rebooting the system. */
187 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
190 /* For safety, we require "magic" arguments. */
191 if (magic1 != LINUX_REBOOT_MAGIC1 ||
192 (magic2 != LINUX_REBOOT_MAGIC2 &&
193 magic2 != LINUX_REBOOT_MAGIC2A &&
194 magic2 != LINUX_REBOOT_MAGIC2B &&
195 magic2 != LINUX_REBOOT_MAGIC2C))
199 * If pid namespaces are enabled and the current task is in a child
200 * pid_namespace, the command is handled by reboot_pid_ns() which will
203 ret = reboot_pid_ns(pid_ns, cmd);
207 /* Instead of trying to make the power_off code look like
208 * halt when pm_power_off is not set do it the easy way.
210 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
211 cmd = LINUX_REBOOT_CMD_HALT;
213 mutex_lock(&reboot_mutex);
215 case LINUX_REBOOT_CMD_RESTART:
216 kernel_restart(NULL);
219 case LINUX_REBOOT_CMD_CAD_ON:
223 case LINUX_REBOOT_CMD_CAD_OFF:
227 case LINUX_REBOOT_CMD_HALT:
230 panic("cannot halt");
232 case LINUX_REBOOT_CMD_POWER_OFF:
237 case LINUX_REBOOT_CMD_RESTART2:
238 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
243 buffer[sizeof(buffer) - 1] = '\0';
245 kernel_restart(buffer);
249 case LINUX_REBOOT_CMD_KEXEC:
250 ret = kernel_kexec();
254 #ifdef CONFIG_HIBERNATION
255 case LINUX_REBOOT_CMD_SW_SUSPEND:
264 mutex_unlock(&reboot_mutex);
268 static void deferred_cad(struct work_struct *dummy)
270 kernel_restart(NULL);
274 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
275 * As it's called within an interrupt, it may NOT sync: the only choice
276 * is whether to reboot at once, or just ignore the ctrl-alt-del.
278 void ctrl_alt_del(void)
280 static DECLARE_WORK(cad_work, deferred_cad);
283 schedule_work(&cad_work);
285 kill_cad_pid(SIGINT, 1);
288 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
290 static int __orderly_poweroff(bool force)
293 static char *envp[] = {
295 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
300 argv = argv_split(GFP_KERNEL, poweroff_cmd, NULL);
302 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
309 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
311 * I guess this should try to kick off some daemon to sync and
312 * poweroff asap. Or not even bother syncing if we're doing an
313 * emergency shutdown?
322 static bool poweroff_force;
324 static void poweroff_work_func(struct work_struct *work)
326 __orderly_poweroff(poweroff_force);
329 static DECLARE_WORK(poweroff_work, poweroff_work_func);
332 * orderly_poweroff - Trigger an orderly system poweroff
333 * @force: force poweroff if command execution fails
335 * This may be called from any context to trigger a system shutdown.
336 * If the orderly shutdown fails, it will force an immediate shutdown.
338 int orderly_poweroff(bool force)
340 if (force) /* do not override the pending "true" */
341 poweroff_force = true;
342 schedule_work(&poweroff_work);
345 EXPORT_SYMBOL_GPL(orderly_poweroff);