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1 /*
2 * linux/kernel/reboot.c
3 *
4 * Copyright (C) 2013 Linus Torvalds
5 */
6
7 #define pr_fmt(fmt) "reboot: " fmt
8
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>
19
20 /*
21 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
22 */
23
24 int C_A_D = 1;
25 struct pid *cad_pid;
26 EXPORT_SYMBOL(cad_pid);
27
28 #if defined(CONFIG_ARM) || defined(CONFIG_UNICORE32)
29 #define DEFAULT_REBOOT_MODE = REBOOT_HARD
30 #else
31 #define DEFAULT_REBOOT_MODE
32 #endif
33 enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
34
35 /*
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.
41 */
42 int reboot_default = 1;
43 int reboot_cpu;
44 enum reboot_type reboot_type = BOOT_ACPI;
45 int reboot_force;
46
47 /*
48 * If set, this is used for preparing the system to power off.
49 */
50
51 void (*pm_power_off_prepare)(void);
52
53 /**
54 * emergency_restart - reboot the system
55 *
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.
60 */
61 void emergency_restart(void)
62 {
63 kmsg_dump(KMSG_DUMP_EMERG);
64 machine_emergency_restart();
65 }
66 EXPORT_SYMBOL_GPL(emergency_restart);
67
68 void kernel_restart_prepare(char *cmd)
69 {
70 blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
71 system_state = SYSTEM_RESTART;
72 usermodehelper_disable();
73 device_shutdown();
74 }
75
76 /**
77 * register_reboot_notifier - Register function to be called at reboot time
78 * @nb: Info about notifier function to be called
79 *
80 * Registers a function with the list of functions
81 * to be called at reboot time.
82 *
83 * Currently always returns zero, as blocking_notifier_chain_register()
84 * always returns zero.
85 */
86 int register_reboot_notifier(struct notifier_block *nb)
87 {
88 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
89 }
90 EXPORT_SYMBOL(register_reboot_notifier);
91
92 /**
93 * unregister_reboot_notifier - Unregister previously registered reboot notifier
94 * @nb: Hook to be unregistered
95 *
96 * Unregisters a previously registered reboot
97 * notifier function.
98 *
99 * Returns zero on success, or %-ENOENT on failure.
100 */
101 int unregister_reboot_notifier(struct notifier_block *nb)
102 {
103 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
104 }
105 EXPORT_SYMBOL(unregister_reboot_notifier);
106
107 /*
108 * Notifier list for kernel code which wants to be called
109 * to restart the system.
110 */
111 static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
112
113 /**
114 * register_restart_handler - Register function to be called to reset
115 * the system
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
127 *
128 * Registers a function with code to be called to restart the
129 * system.
130 *
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
134 * for details).
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.
138 *
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.
147 *
148 * Currently always returns zero, as atomic_notifier_chain_register()
149 * always returns zero.
150 */
151 int register_restart_handler(struct notifier_block *nb)
152 {
153 return atomic_notifier_chain_register(&restart_handler_list, nb);
154 }
155 EXPORT_SYMBOL(register_restart_handler);
156
157 /**
158 * unregister_restart_handler - Unregister previously registered
159 * restart handler
160 * @nb: Hook to be unregistered
161 *
162 * Unregisters a previously registered restart handler function.
163 *
164 * Returns zero on success, or %-ENOENT on failure.
165 */
166 int unregister_restart_handler(struct notifier_block *nb)
167 {
168 return atomic_notifier_chain_unregister(&restart_handler_list, nb);
169 }
170 EXPORT_SYMBOL(unregister_restart_handler);
171
172 /**
173 * do_kernel_restart - Execute kernel restart handler call chain
174 *
175 * Calls functions registered with register_restart_handler.
176 *
177 * Expected to be called from machine_restart as last step of the restart
178 * sequence.
179 *
180 * Restarts the system immediately if a restart handler function has been
181 * registered. Otherwise does nothing.
182 */
183 void do_kernel_restart(char *cmd)
184 {
185 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
186 }
187
188 void migrate_to_reboot_cpu(void)
189 {
190 /* The boot cpu is always logical cpu 0 */
191 int cpu = reboot_cpu;
192
193 cpu_hotplug_disable();
194
195 /* Make certain the cpu I'm about to reboot on is online */
196 if (!cpu_online(cpu))
197 cpu = cpumask_first(cpu_online_mask);
198
199 /* Prevent races with other tasks migrating this task */
200 current->flags |= PF_NO_SETAFFINITY;
201
202 /* Make certain I only run on the appropriate processor */
203 set_cpus_allowed_ptr(current, cpumask_of(cpu));
204 }
205
206 /**
207 * kernel_restart - reboot the system
208 * @cmd: pointer to buffer containing command to execute for restart
209 * or %NULL
210 *
211 * Shutdown everything and perform a clean reboot.
212 * This is not safe to call in interrupt context.
213 */
214 void kernel_restart(char *cmd)
215 {
216 kernel_restart_prepare(cmd);
217 migrate_to_reboot_cpu();
218 syscore_shutdown();
219 if (!cmd)
220 pr_emerg("Restarting system\n");
221 else
222 pr_emerg("Restarting system with command '%s'\n", cmd);
223 kmsg_dump(KMSG_DUMP_RESTART);
224 machine_restart(cmd);
225 }
226 EXPORT_SYMBOL_GPL(kernel_restart);
227
228 static void kernel_shutdown_prepare(enum system_states state)
229 {
230 blocking_notifier_call_chain(&reboot_notifier_list,
231 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
232 system_state = state;
233 usermodehelper_disable();
234 device_shutdown();
235 }
236 /**
237 * kernel_halt - halt the system
238 *
239 * Shutdown everything and perform a clean system halt.
240 */
241 void kernel_halt(void)
242 {
243 kernel_shutdown_prepare(SYSTEM_HALT);
244 migrate_to_reboot_cpu();
245 syscore_shutdown();
246 pr_emerg("System halted\n");
247 kmsg_dump(KMSG_DUMP_HALT);
248 machine_halt();
249 }
250 EXPORT_SYMBOL_GPL(kernel_halt);
251
252 /**
253 * kernel_power_off - power_off the system
254 *
255 * Shutdown everything and perform a clean system power_off.
256 */
257 void kernel_power_off(void)
258 {
259 kernel_shutdown_prepare(SYSTEM_POWER_OFF);
260 if (pm_power_off_prepare)
261 pm_power_off_prepare();
262 migrate_to_reboot_cpu();
263 syscore_shutdown();
264 pr_emerg("Power down\n");
265 kmsg_dump(KMSG_DUMP_POWEROFF);
266 machine_power_off();
267 }
268 EXPORT_SYMBOL_GPL(kernel_power_off);
269
270 static DEFINE_MUTEX(reboot_mutex);
271
272 /*
273 * Reboot system call: for obvious reasons only root may call it,
274 * and even root needs to set up some magic numbers in the registers
275 * so that some mistake won't make this reboot the whole machine.
276 * You can also set the meaning of the ctrl-alt-del-key here.
277 *
278 * reboot doesn't sync: do that yourself before calling this.
279 */
280 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
281 void __user *, arg)
282 {
283 struct pid_namespace *pid_ns = task_active_pid_ns(current);
284 char buffer[256];
285 int ret = 0;
286
287 /* We only trust the superuser with rebooting the system. */
288 if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
289 return -EPERM;
290
291 /* For safety, we require "magic" arguments. */
292 if (magic1 != LINUX_REBOOT_MAGIC1 ||
293 (magic2 != LINUX_REBOOT_MAGIC2 &&
294 magic2 != LINUX_REBOOT_MAGIC2A &&
295 magic2 != LINUX_REBOOT_MAGIC2B &&
296 magic2 != LINUX_REBOOT_MAGIC2C))
297 return -EINVAL;
298
299 /*
300 * If pid namespaces are enabled and the current task is in a child
301 * pid_namespace, the command is handled by reboot_pid_ns() which will
302 * call do_exit().
303 */
304 ret = reboot_pid_ns(pid_ns, cmd);
305 if (ret)
306 return ret;
307
308 /* Instead of trying to make the power_off code look like
309 * halt when pm_power_off is not set do it the easy way.
310 */
311 if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
312 cmd = LINUX_REBOOT_CMD_HALT;
313
314 mutex_lock(&reboot_mutex);
315 switch (cmd) {
316 case LINUX_REBOOT_CMD_RESTART:
317 kernel_restart(NULL);
318 break;
319
320 case LINUX_REBOOT_CMD_CAD_ON:
321 C_A_D = 1;
322 break;
323
324 case LINUX_REBOOT_CMD_CAD_OFF:
325 C_A_D = 0;
326 break;
327
328 case LINUX_REBOOT_CMD_HALT:
329 kernel_halt();
330 do_exit(0);
331 panic("cannot halt");
332
333 case LINUX_REBOOT_CMD_POWER_OFF:
334 kernel_power_off();
335 do_exit(0);
336 break;
337
338 case LINUX_REBOOT_CMD_RESTART2:
339 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
340 if (ret < 0) {
341 ret = -EFAULT;
342 break;
343 }
344 buffer[sizeof(buffer) - 1] = '\0';
345
346 kernel_restart(buffer);
347 break;
348
349 #ifdef CONFIG_KEXEC_CORE
350 case LINUX_REBOOT_CMD_KEXEC:
351 ret = kernel_kexec();
352 break;
353 #endif
354
355 #ifdef CONFIG_HIBERNATION
356 case LINUX_REBOOT_CMD_SW_SUSPEND:
357 ret = hibernate();
358 break;
359 #endif
360
361 default:
362 ret = -EINVAL;
363 break;
364 }
365 mutex_unlock(&reboot_mutex);
366 return ret;
367 }
368
369 static void deferred_cad(struct work_struct *dummy)
370 {
371 kernel_restart(NULL);
372 }
373
374 /*
375 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
376 * As it's called within an interrupt, it may NOT sync: the only choice
377 * is whether to reboot at once, or just ignore the ctrl-alt-del.
378 */
379 void ctrl_alt_del(void)
380 {
381 static DECLARE_WORK(cad_work, deferred_cad);
382
383 if (C_A_D)
384 schedule_work(&cad_work);
385 else
386 kill_cad_pid(SIGINT, 1);
387 }
388
389 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
390 static const char reboot_cmd[] = "/sbin/reboot";
391
392 static int run_cmd(const char *cmd)
393 {
394 char **argv;
395 static char *envp[] = {
396 "HOME=/",
397 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
398 NULL
399 };
400 int ret;
401 argv = argv_split(GFP_KERNEL, cmd, NULL);
402 if (argv) {
403 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
404 argv_free(argv);
405 } else {
406 ret = -ENOMEM;
407 }
408
409 return ret;
410 }
411
412 static int __orderly_reboot(void)
413 {
414 int ret;
415
416 ret = run_cmd(reboot_cmd);
417
418 if (ret) {
419 pr_warn("Failed to start orderly reboot: forcing the issue\n");
420 emergency_sync();
421 kernel_restart(NULL);
422 }
423
424 return ret;
425 }
426
427 static int __orderly_poweroff(bool force)
428 {
429 int ret;
430
431 ret = run_cmd(poweroff_cmd);
432
433 if (ret && force) {
434 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
435
436 /*
437 * I guess this should try to kick off some daemon to sync and
438 * poweroff asap. Or not even bother syncing if we're doing an
439 * emergency shutdown?
440 */
441 emergency_sync();
442 kernel_power_off();
443 }
444
445 return ret;
446 }
447
448 static bool poweroff_force;
449
450 static void poweroff_work_func(struct work_struct *work)
451 {
452 __orderly_poweroff(poweroff_force);
453 }
454
455 static DECLARE_WORK(poweroff_work, poweroff_work_func);
456
457 /**
458 * orderly_poweroff - Trigger an orderly system poweroff
459 * @force: force poweroff if command execution fails
460 *
461 * This may be called from any context to trigger a system shutdown.
462 * If the orderly shutdown fails, it will force an immediate shutdown.
463 */
464 void orderly_poweroff(bool force)
465 {
466 if (force) /* do not override the pending "true" */
467 poweroff_force = true;
468 schedule_work(&poweroff_work);
469 }
470 EXPORT_SYMBOL_GPL(orderly_poweroff);
471
472 static void reboot_work_func(struct work_struct *work)
473 {
474 __orderly_reboot();
475 }
476
477 static DECLARE_WORK(reboot_work, reboot_work_func);
478
479 /**
480 * orderly_reboot - Trigger an orderly system reboot
481 *
482 * This may be called from any context to trigger a system reboot.
483 * If the orderly reboot fails, it will force an immediate reboot.
484 */
485 void orderly_reboot(void)
486 {
487 schedule_work(&reboot_work);
488 }
489 EXPORT_SYMBOL_GPL(orderly_reboot);
490
491 static int __init reboot_setup(char *str)
492 {
493 for (;;) {
494 /*
495 * Having anything passed on the command line via
496 * reboot= will cause us to disable DMI checking
497 * below.
498 */
499 reboot_default = 0;
500
501 switch (*str) {
502 case 'w':
503 reboot_mode = REBOOT_WARM;
504 break;
505
506 case 'c':
507 reboot_mode = REBOOT_COLD;
508 break;
509
510 case 'h':
511 reboot_mode = REBOOT_HARD;
512 break;
513
514 case 's':
515 {
516 int rc;
517
518 if (isdigit(*(str+1))) {
519 rc = kstrtoint(str+1, 0, &reboot_cpu);
520 if (rc)
521 return rc;
522 } else if (str[1] == 'm' && str[2] == 'p' &&
523 isdigit(*(str+3))) {
524 rc = kstrtoint(str+3, 0, &reboot_cpu);
525 if (rc)
526 return rc;
527 } else
528 reboot_mode = REBOOT_SOFT;
529 break;
530 }
531 case 'g':
532 reboot_mode = REBOOT_GPIO;
533 break;
534
535 case 'b':
536 case 'a':
537 case 'k':
538 case 't':
539 case 'e':
540 case 'p':
541 reboot_type = *str;
542 break;
543
544 case 'f':
545 reboot_force = 1;
546 break;
547 }
548
549 str = strchr(str, ',');
550 if (str)
551 str++;
552 else
553 break;
554 }
555 return 1;
556 }
557 __setup("reboot=", reboot_setup);