projects/linux·blob v4.0-rc1 · refs

514 lines · 12.5 KiB

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
24int C_A_D = 1;
25struct pid *cad_pid;
26EXPORT_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
33enum 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 */
42int reboot_default = 1;
43int reboot_cpu;
44enum reboot_type reboot_type = BOOT_ACPI;
45int reboot_force;
46
47/*
48 * If set, this is used for preparing the system to power off.
49 */
50
51void (*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 */
61void emergency_restart(void)
62{
63 kmsg_dump(KMSG_DUMP_EMERG);
64 machine_emergency_restart();
65}
66EXPORT_SYMBOL_GPL(emergency_restart);
67
68void 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 */
86int register_reboot_notifier(struct notifier_block *nb)
87{
88 return blocking_notifier_chain_register(&reboot_notifier_list, nb);
89}
90EXPORT_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 */
101int unregister_reboot_notifier(struct notifier_block *nb)
102{
103 return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
104}
105EXPORT_SYMBOL(unregister_reboot_notifier);
106
107/*
108 * Notifier list for kernel code which wants to be called
109 * to restart the system.
110 */
111static 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 */
151int register_restart_handler(struct notifier_block *nb)
152{
153 return atomic_notifier_chain_register(&restart_handler_list, nb);
154}
155EXPORT_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 */
166int unregister_restart_handler(struct notifier_block *nb)
167{
168 return atomic_notifier_chain_unregister(&restart_handler_list, nb);
169}
170EXPORT_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 */
183void do_kernel_restart(char *cmd)
184{
185 atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
186}
187
188void 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 */
214void 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}
226EXPORT_SYMBOL_GPL(kernel_restart);
227
228static 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 */
241void 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}
250EXPORT_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 */
257void 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}
268EXPORT_SYMBOL_GPL(kernel_power_off);
269
270static 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 */
280SYSCALL_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
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
369static 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 */
379void 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
389char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
390
391static int __orderly_poweroff(bool force)
392{
393 char **argv;
394 static char *envp[] = {
395 "HOME=/",
396 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
397 NULL
398 };
399 int ret;
400
401 argv = argv_split(GFP_KERNEL, poweroff_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 if (ret && force) {
410 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
411 /*
412 * I guess this should try to kick off some daemon to sync and
413 * poweroff asap. Or not even bother syncing if we're doing an
414 * emergency shutdown?
415 */
416 emergency_sync();
417 kernel_power_off();
418 }
419
420 return ret;
421}
422
423static bool poweroff_force;
424
425static void poweroff_work_func(struct work_struct *work)
426{
427 __orderly_poweroff(poweroff_force);
428}
429
430static DECLARE_WORK(poweroff_work, poweroff_work_func);
431
432/**
433 * orderly_poweroff - Trigger an orderly system poweroff
434 * @force: force poweroff if command execution fails
435 *
436 * This may be called from any context to trigger a system shutdown.
437 * If the orderly shutdown fails, it will force an immediate shutdown.
438 */
439int orderly_poweroff(bool force)
440{
441 if (force) /* do not override the pending "true" */
442 poweroff_force = true;
443 schedule_work(&poweroff_work);
444 return 0;
445}
446EXPORT_SYMBOL_GPL(orderly_poweroff);
447
448static int __init reboot_setup(char *str)
449{
450 for (;;) {
451 /*
452 * Having anything passed on the command line via
453 * reboot= will cause us to disable DMI checking
454 * below.
455 */
456 reboot_default = 0;
457
458 switch (*str) {
459 case 'w':
460 reboot_mode = REBOOT_WARM;
461 break;
462
463 case 'c':
464 reboot_mode = REBOOT_COLD;
465 break;
466
467 case 'h':
468 reboot_mode = REBOOT_HARD;
469 break;
470
471 case 's':
472 {
473 int rc;
474
475 if (isdigit(*(str+1))) {
476 rc = kstrtoint(str+1, 0, &reboot_cpu);
477 if (rc)
478 return rc;
479 } else if (str[1] == 'm' && str[2] == 'p' &&
480 isdigit(*(str+3))) {
481 rc = kstrtoint(str+3, 0, &reboot_cpu);
482 if (rc)
483 return rc;
484 } else
485 reboot_mode = REBOOT_SOFT;
486 break;
487 }
488 case 'g':
489 reboot_mode = REBOOT_GPIO;
490 break;
491
492 case 'b':
493 case 'a':
494 case 'k':
495 case 't':
496 case 'e':
497 case 'p':
498 reboot_type = *str;
499 break;
500
501 case 'f':
502 reboot_force = 1;
503 break;
504 }
505
506 str = strchr(str, ',');
507 if (str)
508 str++;
509 else
510 break;
511 }
512 return 1;
513}
514__setup("reboot=", reboot_setup);