root/kernel/reboot.c

DEFINITIONS

1. emergency_restart
2. kernel_restart_prepare
3. register_reboot_notifier
4. unregister_reboot_notifier
5. devm_unregister_reboot_notifier
6. devm_register_reboot_notifier
7. register_restart_handler
8. unregister_restart_handler
9. do_kernel_restart
10. migrate_to_reboot_cpu
11. kernel_restart
12. kernel_shutdown_prepare
13. kernel_halt
14. kernel_power_off
15. SYSCALL_DEFINE4
16. deferred_cad
17. ctrl_alt_del
18. run_cmd
19. __orderly_reboot
20. __orderly_poweroff
21. poweroff_work_func
22. orderly_poweroff
23. reboot_work_func
24. orderly_reboot
25. reboot_setup

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/kernel/reboot.c
   4  *
   5  *  Copyright (C) 2013  Linus Torvalds
   6  */
   7 
   8 #define pr_fmt(fmt)     "reboot: " fmt
   9 
  10 #include <linux/ctype.h>
  11 #include <linux/export.h>
  12 #include <linux/kexec.h>
  13 #include <linux/kmod.h>
  14 #include <linux/kmsg_dump.h>
  15 #include <linux/reboot.h>
  16 #include <linux/suspend.h>
  17 #include <linux/syscalls.h>
  18 #include <linux/syscore_ops.h>
  19 #include <linux/uaccess.h>
  20 
  21 /*
  22  * this indicates whether you can reboot with ctrl-alt-del: the default is yes
  23  */
  24 
  25 int C_A_D = 1;
  26 struct pid *cad_pid;
  27 EXPORT_SYMBOL(cad_pid);
  28 
  29 #if defined(CONFIG_ARM) || defined(CONFIG_UNICORE32)
  30 #define DEFAULT_REBOOT_MODE             = REBOOT_HARD
  31 #else
  32 #define DEFAULT_REBOOT_MODE
  33 #endif
  34 enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
  35 enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
  36 
  37 /*
  38  * This variable is used privately to keep track of whether or not
  39  * reboot_type is still set to its default value (i.e., reboot= hasn't
  40  * been set on the command line).  This is needed so that we can
  41  * suppress DMI scanning for reboot quirks.  Without it, it's
  42  * impossible to override a faulty reboot quirk without recompiling.
  43  */
  44 int reboot_default = 1;
  45 int reboot_cpu;
  46 enum reboot_type reboot_type = BOOT_ACPI;
  47 int reboot_force;
  48 
  49 /*
  50  * If set, this is used for preparing the system to power off.
  51  */
  52 
  53 void (*pm_power_off_prepare)(void);
  54 EXPORT_SYMBOL_GPL(pm_power_off_prepare);
  55 
  56 /**
  57  *      emergency_restart - reboot the system
  58  *
  59  *      Without shutting down any hardware or taking any locks
  60  *      reboot the system.  This is called when we know we are in
  61  *      trouble so this is our best effort to reboot.  This is
  62  *      safe to call in interrupt context.
  63  */
  64 void emergency_restart(void)
  65 {
  66         kmsg_dump(KMSG_DUMP_EMERG);
  67         machine_emergency_restart();
  68 }
  69 EXPORT_SYMBOL_GPL(emergency_restart);
  70 
  71 void kernel_restart_prepare(char *cmd)
  72 {
  73         blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
  74         system_state = SYSTEM_RESTART;
  75         usermodehelper_disable();
  76         device_shutdown();
  77 }
  78 
  79 /**
  80  *      register_reboot_notifier - Register function to be called at reboot time
  81  *      @nb: Info about notifier function to be called
  82  *
  83  *      Registers a function with the list of functions
  84  *      to be called at reboot time.
  85  *
  86  *      Currently always returns zero, as blocking_notifier_chain_register()
  87  *      always returns zero.
  88  */
  89 int register_reboot_notifier(struct notifier_block *nb)
  90 {
  91         return blocking_notifier_chain_register(&reboot_notifier_list, nb);
  92 }
  93 EXPORT_SYMBOL(register_reboot_notifier);
  94 
  95 /**
  96  *      unregister_reboot_notifier - Unregister previously registered reboot notifier
  97  *      @nb: Hook to be unregistered
  98  *
  99  *      Unregisters a previously registered reboot
 100  *      notifier function.
 101  *
 102  *      Returns zero on success, or %-ENOENT on failure.
 103  */
 104 int unregister_reboot_notifier(struct notifier_block *nb)
 105 {
 106         return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
 107 }
 108 EXPORT_SYMBOL(unregister_reboot_notifier);
 109 
 110 static void devm_unregister_reboot_notifier(struct device *dev, void *res)
 111 {
 112         WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
 113 }
 114 
 115 int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
 116 {
 117         struct notifier_block **rcnb;
 118         int ret;
 119 
 120         rcnb = devres_alloc(devm_unregister_reboot_notifier,
 121                             sizeof(*rcnb), GFP_KERNEL);
 122         if (!rcnb)
 123                 return -ENOMEM;
 124 
 125         ret = register_reboot_notifier(nb);
 126         if (!ret) {
 127                 *rcnb = nb;
 128                 devres_add(dev, rcnb);
 129         } else {
 130                 devres_free(rcnb);
 131         }
 132 
 133         return ret;
 134 }
 135 EXPORT_SYMBOL(devm_register_reboot_notifier);
 136 
 137 /*
 138  *      Notifier list for kernel code which wants to be called
 139  *      to restart the system.
 140  */
 141 static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
 142 
 143 /**
 144  *      register_restart_handler - Register function to be called to reset
 145  *                                 the system
 146  *      @nb: Info about handler function to be called
 147  *      @nb->priority:  Handler priority. Handlers should follow the
 148  *                      following guidelines for setting priorities.
 149  *                      0:      Restart handler of last resort,
 150  *                              with limited restart capabilities
 151  *                      128:    Default restart handler; use if no other
 152  *                              restart handler is expected to be available,
 153  *                              and/or if restart functionality is
 154  *                              sufficient to restart the entire system
 155  *                      255:    Highest priority restart handler, will
 156  *                              preempt all other restart handlers
 157  *
 158  *      Registers a function with code to be called to restart the
 159  *      system.
 160  *
 161  *      Registered functions will be called from machine_restart as last
 162  *      step of the restart sequence (if the architecture specific
 163  *      machine_restart function calls do_kernel_restart - see below
 164  *      for details).
 165  *      Registered functions are expected to restart the system immediately.
 166  *      If more than one function is registered, the restart handler priority
 167  *      selects which function will be called first.
 168  *
 169  *      Restart handlers are expected to be registered from non-architecture
 170  *      code, typically from drivers. A typical use case would be a system
 171  *      where restart functionality is provided through a watchdog. Multiple
 172  *      restart handlers may exist; for example, one restart handler might
 173  *      restart the entire system, while another only restarts the CPU.
 174  *      In such cases, the restart handler which only restarts part of the
 175  *      hardware is expected to register with low priority to ensure that
 176  *      it only runs if no other means to restart the system is available.
 177  *
 178  *      Currently always returns zero, as atomic_notifier_chain_register()
 179  *      always returns zero.
 180  */
 181 int register_restart_handler(struct notifier_block *nb)
 182 {
 183         return atomic_notifier_chain_register(&restart_handler_list, nb);
 184 }
 185 EXPORT_SYMBOL(register_restart_handler);
 186 
 187 /**
 188  *      unregister_restart_handler - Unregister previously registered
 189  *                                   restart handler
 190  *      @nb: Hook to be unregistered
 191  *
 192  *      Unregisters a previously registered restart handler function.
 193  *
 194  *      Returns zero on success, or %-ENOENT on failure.
 195  */
 196 int unregister_restart_handler(struct notifier_block *nb)
 197 {
 198         return atomic_notifier_chain_unregister(&restart_handler_list, nb);
 199 }
 200 EXPORT_SYMBOL(unregister_restart_handler);
 201 
 202 /**
 203  *      do_kernel_restart - Execute kernel restart handler call chain
 204  *
 205  *      Calls functions registered with register_restart_handler.
 206  *
 207  *      Expected to be called from machine_restart as last step of the restart
 208  *      sequence.
 209  *
 210  *      Restarts the system immediately if a restart handler function has been
 211  *      registered. Otherwise does nothing.
 212  */
 213 void do_kernel_restart(char *cmd)
 214 {
 215         atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
 216 }
 217 
 218 void migrate_to_reboot_cpu(void)
 219 {
 220         /* The boot cpu is always logical cpu 0 */
 221         int cpu = reboot_cpu;
 222 
 223         cpu_hotplug_disable();
 224 
 225         /* Make certain the cpu I'm about to reboot on is online */
 226         if (!cpu_online(cpu))
 227                 cpu = cpumask_first(cpu_online_mask);
 228 
 229         /* Prevent races with other tasks migrating this task */
 230         current->flags |= PF_NO_SETAFFINITY;
 231 
 232         /* Make certain I only run on the appropriate processor */
 233         set_cpus_allowed_ptr(current, cpumask_of(cpu));
 234 }
 235 
 236 /**
 237  *      kernel_restart - reboot the system
 238  *      @cmd: pointer to buffer containing command to execute for restart
 239  *              or %NULL
 240  *
 241  *      Shutdown everything and perform a clean reboot.
 242  *      This is not safe to call in interrupt context.
 243  */
 244 void kernel_restart(char *cmd)
 245 {
 246         kernel_restart_prepare(cmd);
 247         migrate_to_reboot_cpu();
 248         syscore_shutdown();
 249         if (!cmd)
 250                 pr_emerg("Restarting system\n");
 251         else
 252                 pr_emerg("Restarting system with command '%s'\n", cmd);
 253         kmsg_dump(KMSG_DUMP_RESTART);
 254         machine_restart(cmd);
 255 }
 256 EXPORT_SYMBOL_GPL(kernel_restart);
 257 
 258 static void kernel_shutdown_prepare(enum system_states state)
 259 {
 260         blocking_notifier_call_chain(&reboot_notifier_list,
 261                 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
 262         system_state = state;
 263         usermodehelper_disable();
 264         device_shutdown();
 265 }
 266 /**
 267  *      kernel_halt - halt the system
 268  *
 269  *      Shutdown everything and perform a clean system halt.
 270  */
 271 void kernel_halt(void)
 272 {
 273         kernel_shutdown_prepare(SYSTEM_HALT);
 274         migrate_to_reboot_cpu();
 275         syscore_shutdown();
 276         pr_emerg("System halted\n");
 277         kmsg_dump(KMSG_DUMP_HALT);
 278         machine_halt();
 279 }
 280 EXPORT_SYMBOL_GPL(kernel_halt);
 281 
 282 /**
 283  *      kernel_power_off - power_off the system
 284  *
 285  *      Shutdown everything and perform a clean system power_off.
 286  */
 287 void kernel_power_off(void)
 288 {
 289         kernel_shutdown_prepare(SYSTEM_POWER_OFF);
 290         if (pm_power_off_prepare)
 291                 pm_power_off_prepare();
 292         migrate_to_reboot_cpu();
 293         syscore_shutdown();
 294         pr_emerg("Power down\n");
 295         kmsg_dump(KMSG_DUMP_POWEROFF);
 296         machine_power_off();
 297 }
 298 EXPORT_SYMBOL_GPL(kernel_power_off);
 299 
 300 DEFINE_MUTEX(system_transition_mutex);
 301 
 302 /*
 303  * Reboot system call: for obvious reasons only root may call it,
 304  * and even root needs to set up some magic numbers in the registers
 305  * so that some mistake won't make this reboot the whole machine.
 306  * You can also set the meaning of the ctrl-alt-del-key here.
 307  *
 308  * reboot doesn't sync: do that yourself before calling this.
 309  */
 310 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 311                 void __user *, arg)
 312 {
 313         struct pid_namespace *pid_ns = task_active_pid_ns(current);
 314         char buffer[256];
 315         int ret = 0;
 316 
 317         /* We only trust the superuser with rebooting the system. */
 318         if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
 319                 return -EPERM;
 320 
 321         /* For safety, we require "magic" arguments. */
 322         if (magic1 != LINUX_REBOOT_MAGIC1 ||
 323                         (magic2 != LINUX_REBOOT_MAGIC2 &&
 324                         magic2 != LINUX_REBOOT_MAGIC2A &&
 325                         magic2 != LINUX_REBOOT_MAGIC2B &&
 326                         magic2 != LINUX_REBOOT_MAGIC2C))
 327                 return -EINVAL;
 328 
 329         /*
 330          * If pid namespaces are enabled and the current task is in a child
 331          * pid_namespace, the command is handled by reboot_pid_ns() which will
 332          * call do_exit().
 333          */
 334         ret = reboot_pid_ns(pid_ns, cmd);
 335         if (ret)
 336                 return ret;
 337 
 338         /* Instead of trying to make the power_off code look like
 339          * halt when pm_power_off is not set do it the easy way.
 340          */
 341         if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
 342                 cmd = LINUX_REBOOT_CMD_HALT;
 343 
 344         mutex_lock(&system_transition_mutex);
 345         switch (cmd) {
 346         case LINUX_REBOOT_CMD_RESTART:
 347                 kernel_restart(NULL);
 348                 break;
 349 
 350         case LINUX_REBOOT_CMD_CAD_ON:
 351                 C_A_D = 1;
 352                 break;
 353 
 354         case LINUX_REBOOT_CMD_CAD_OFF:
 355                 C_A_D = 0;
 356                 break;
 357 
 358         case LINUX_REBOOT_CMD_HALT:
 359                 kernel_halt();
 360                 do_exit(0);
 361                 panic("cannot halt");
 362 
 363         case LINUX_REBOOT_CMD_POWER_OFF:
 364                 kernel_power_off();
 365                 do_exit(0);
 366                 break;
 367 
 368         case LINUX_REBOOT_CMD_RESTART2:
 369                 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
 370                 if (ret < 0) {
 371                         ret = -EFAULT;
 372                         break;
 373                 }
 374                 buffer[sizeof(buffer) - 1] = '\0';
 375 
 376                 kernel_restart(buffer);
 377                 break;
 378 
 379 #ifdef CONFIG_KEXEC_CORE
 380         case LINUX_REBOOT_CMD_KEXEC:
 381                 ret = kernel_kexec();
 382                 break;
 383 #endif
 384 
 385 #ifdef CONFIG_HIBERNATION
 386         case LINUX_REBOOT_CMD_SW_SUSPEND:
 387                 ret = hibernate();
 388                 break;
 389 #endif
 390 
 391         default:
 392                 ret = -EINVAL;
 393                 break;
 394         }
 395         mutex_unlock(&system_transition_mutex);
 396         return ret;
 397 }
 398 
 399 static void deferred_cad(struct work_struct *dummy)
 400 {
 401         kernel_restart(NULL);
 402 }
 403 
 404 /*
 405  * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
 406  * As it's called within an interrupt, it may NOT sync: the only choice
 407  * is whether to reboot at once, or just ignore the ctrl-alt-del.
 408  */
 409 void ctrl_alt_del(void)
 410 {
 411         static DECLARE_WORK(cad_work, deferred_cad);
 412 
 413         if (C_A_D)
 414                 schedule_work(&cad_work);
 415         else
 416                 kill_cad_pid(SIGINT, 1);
 417 }
 418 
 419 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
 420 static const char reboot_cmd[] = "/sbin/reboot";
 421 
 422 static int run_cmd(const char *cmd)
 423 {
 424         char **argv;
 425         static char *envp[] = {
 426                 "HOME=/",
 427                 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
 428                 NULL
 429         };
 430         int ret;
 431         argv = argv_split(GFP_KERNEL, cmd, NULL);
 432         if (argv) {
 433                 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
 434                 argv_free(argv);
 435         } else {
 436                 ret = -ENOMEM;
 437         }
 438 
 439         return ret;
 440 }
 441 
 442 static int __orderly_reboot(void)
 443 {
 444         int ret;
 445 
 446         ret = run_cmd(reboot_cmd);
 447 
 448         if (ret) {
 449                 pr_warn("Failed to start orderly reboot: forcing the issue\n");
 450                 emergency_sync();
 451                 kernel_restart(NULL);
 452         }
 453 
 454         return ret;
 455 }
 456 
 457 static int __orderly_poweroff(bool force)
 458 {
 459         int ret;
 460 
 461         ret = run_cmd(poweroff_cmd);
 462 
 463         if (ret && force) {
 464                 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
 465 
 466                 /*
 467                  * I guess this should try to kick off some daemon to sync and
 468                  * poweroff asap.  Or not even bother syncing if we're doing an
 469                  * emergency shutdown?
 470                  */
 471                 emergency_sync();
 472                 kernel_power_off();
 473         }
 474 
 475         return ret;
 476 }
 477 
 478 static bool poweroff_force;
 479 
 480 static void poweroff_work_func(struct work_struct *work)
 481 {
 482         __orderly_poweroff(poweroff_force);
 483 }
 484 
 485 static DECLARE_WORK(poweroff_work, poweroff_work_func);
 486 
 487 /**
 488  * orderly_poweroff - Trigger an orderly system poweroff
 489  * @force: force poweroff if command execution fails
 490  *
 491  * This may be called from any context to trigger a system shutdown.
 492  * If the orderly shutdown fails, it will force an immediate shutdown.
 493  */
 494 void orderly_poweroff(bool force)
 495 {
 496         if (force) /* do not override the pending "true" */
 497                 poweroff_force = true;
 498         schedule_work(&poweroff_work);
 499 }
 500 EXPORT_SYMBOL_GPL(orderly_poweroff);
 501 
 502 static void reboot_work_func(struct work_struct *work)
 503 {
 504         __orderly_reboot();
 505 }
 506 
 507 static DECLARE_WORK(reboot_work, reboot_work_func);
 508 
 509 /**
 510  * orderly_reboot - Trigger an orderly system reboot
 511  *
 512  * This may be called from any context to trigger a system reboot.
 513  * If the orderly reboot fails, it will force an immediate reboot.
 514  */
 515 void orderly_reboot(void)
 516 {
 517         schedule_work(&reboot_work);
 518 }
 519 EXPORT_SYMBOL_GPL(orderly_reboot);
 520 
 521 static int __init reboot_setup(char *str)
 522 {
 523         for (;;) {
 524                 enum reboot_mode *mode;
 525 
 526                 /*
 527                  * Having anything passed on the command line via
 528                  * reboot= will cause us to disable DMI checking
 529                  * below.
 530                  */
 531                 reboot_default = 0;
 532 
 533                 if (!strncmp(str, "panic_", 6)) {
 534                         mode = &panic_reboot_mode;
 535                         str += 6;
 536                 } else {
 537                         mode = &reboot_mode;
 538                 }
 539 
 540                 switch (*str) {
 541                 case 'w':
 542                         *mode = REBOOT_WARM;
 543                         break;
 544 
 545                 case 'c':
 546                         *mode = REBOOT_COLD;
 547                         break;
 548 
 549                 case 'h':
 550                         *mode = REBOOT_HARD;
 551                         break;
 552 
 553                 case 's':
 554                 {
 555                         int rc;
 556 
 557                         if (isdigit(*(str+1))) {
 558                                 rc = kstrtoint(str+1, 0, &reboot_cpu);
 559                                 if (rc)
 560                                         return rc;
 561                         } else if (str[1] == 'm' && str[2] == 'p' &&
 562                                    isdigit(*(str+3))) {
 563                                 rc = kstrtoint(str+3, 0, &reboot_cpu);
 564                                 if (rc)
 565                                         return rc;
 566                         } else
 567                                 *mode = REBOOT_SOFT;
 568                         break;
 569                 }
 570                 case 'g':
 571                         *mode = REBOOT_GPIO;
 572                         break;
 573 
 574                 case 'b':
 575                 case 'a':
 576                 case 'k':
 577                 case 't':
 578                 case 'e':
 579                 case 'p':
 580                         reboot_type = *str;
 581                         break;
 582 
 583                 case 'f':
 584                         reboot_force = 1;
 585                         break;
 586                 }
 587 
 588                 str = strchr(str, ',');
 589                 if (str)
 590                         str++;
 591                 else
 592                         break;
 593         }
 594         return 1;
 595 }
 596 __setup("reboot=", reboot_setup);