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 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);