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Linux/kernel/reboot.c

  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);
558 

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