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 static void migrate_to_reboot_cpu(void)
 108 {
 109         /* The boot cpu is always logical cpu 0 */
 110         int cpu = reboot_cpu;
 111
 112         cpu_hotplug_disable();
 113
 114         /* Make certain the cpu I'm about to reboot on is online */
 115         if (!cpu_online(cpu))
 116                 cpu = cpumask_first(cpu_online_mask);
 117
 118         /* Prevent races with other tasks migrating this task */
 119         current->flags |= PF_NO_SETAFFINITY;
 120
 121         /* Make certain I only run on the appropriate processor */
 122         set_cpus_allowed_ptr(current, cpumask_of(cpu));
 123 }
 124
 125 /**
 126  *      kernel_restart - reboot the system
 127  *      @cmd: pointer to buffer containing command to execute for restart
 128  *              or %NULL
 129  *
 130  *      Shutdown everything and perform a clean reboot.
 131  *      This is not safe to call in interrupt context.
 132  */
 133 void kernel_restart(char *cmd)
 134 {
 135         kernel_restart_prepare(cmd);
 136         migrate_to_reboot_cpu();
 137         syscore_shutdown();
 138         if (!cmd)
 139                 pr_emerg("Restarting system\n");
 140         else
 141                 pr_emerg("Restarting system with command '%s'\n", cmd);
 142         kmsg_dump(KMSG_DUMP_RESTART);
 143         machine_restart(cmd);
 144 }
 145 EXPORT_SYMBOL_GPL(kernel_restart);
 146
 147 static void kernel_shutdown_prepare(enum system_states state)
 148 {
 149         blocking_notifier_call_chain(&reboot_notifier_list,
 150                 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
 151         system_state = state;
 152         usermodehelper_disable();
 153         device_shutdown();
 154 }
 155 /**
 156  *      kernel_halt - halt the system
 157  *
 158  *      Shutdown everything and perform a clean system halt.
 159  */
 160 void kernel_halt(void)
 161 {
 162         kernel_shutdown_prepare(SYSTEM_HALT);
 163         migrate_to_reboot_cpu();
 164         syscore_shutdown();
 165         pr_emerg("System halted\n");
 166         kmsg_dump(KMSG_DUMP_HALT);
 167         machine_halt();
 168 }
 169 EXPORT_SYMBOL_GPL(kernel_halt);
 170
 171 /**
 172  *      kernel_power_off - power_off the system
 173  *
 174  *      Shutdown everything and perform a clean system power_off.
 175  */
 176 void kernel_power_off(void)
 177 {
 178         kernel_shutdown_prepare(SYSTEM_POWER_OFF);
 179         if (pm_power_off_prepare)
 180                 pm_power_off_prepare();
 181         migrate_to_reboot_cpu();
 182         syscore_shutdown();
 183         pr_emerg("Power down\n");
 184         kmsg_dump(KMSG_DUMP_POWEROFF);
 185         machine_power_off();
 186 }
 187 EXPORT_SYMBOL_GPL(kernel_power_off);
 188
 189 static DEFINE_MUTEX(reboot_mutex);
 190
 191 /*
 192  * Reboot system call: for obvious reasons only root may call it,
 193  * and even root needs to set up some magic numbers in the registers
 194  * so that some mistake won't make this reboot the whole machine.
 195  * You can also set the meaning of the ctrl-alt-del-key here.
 196  *
 197  * reboot doesn't sync: do that yourself before calling this.
 198  */
 199 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 200                 void __user *, arg)
 201 {
 202         struct pid_namespace *pid_ns = task_active_pid_ns(current);
 203         char buffer[256];
 204         int ret = 0;
 205
 206         /* We only trust the superuser with rebooting the system. */
 207         if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
 208                 return -EPERM;
 209
 210         /* For safety, we require "magic" arguments. */
 211         if (magic1 != LINUX_REBOOT_MAGIC1 ||
 212                         (magic2 != LINUX_REBOOT_MAGIC2 &&
 213                         magic2 != LINUX_REBOOT_MAGIC2A &&
 214                         magic2 != LINUX_REBOOT_MAGIC2B &&
 215                         magic2 != LINUX_REBOOT_MAGIC2C))
 216                 return -EINVAL;
 217
 218         /*
 219          * If pid namespaces are enabled and the current task is in a child
 220          * pid_namespace, the command is handled by reboot_pid_ns() which will
 221          * call do_exit().
 222          */
 223         ret = reboot_pid_ns(pid_ns, cmd);
 224         if (ret)
 225                 return ret;
 226
 227         /* Instead of trying to make the power_off code look like
 228          * halt when pm_power_off is not set do it the easy way.
 229          */
 230         if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
 231                 cmd = LINUX_REBOOT_CMD_HALT;
 232
 233         mutex_lock(&reboot_mutex);
 234         switch (cmd) {
 235         case LINUX_REBOOT_CMD_RESTART:
 236                 kernel_restart(NULL);
 237                 break;
 238
 239         case LINUX_REBOOT_CMD_CAD_ON:
 240                 C_A_D = 1;
 241                 break;
 242
 243         case LINUX_REBOOT_CMD_CAD_OFF:
 244                 C_A_D = 0;
 245                 break;
 246
 247         case LINUX_REBOOT_CMD_HALT:
 248                 kernel_halt();
 249                 do_exit(0);
 250                 panic("cannot halt");
 251
 252         case LINUX_REBOOT_CMD_POWER_OFF:
 253                 kernel_power_off();
 254                 do_exit(0);
 255                 break;
 256
 257         case LINUX_REBOOT_CMD_RESTART2:
 258                 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
 259                 if (ret < 0) {
 260                         ret = -EFAULT;
 261                         break;
 262                 }
 263                 buffer[sizeof(buffer) - 1] = '\0';
 264
 265                 kernel_restart(buffer);
 266                 break;
 267
 268 #ifdef CONFIG_KEXEC
 269         case LINUX_REBOOT_CMD_KEXEC:
 270                 ret = kernel_kexec();
 271                 break;
 272 #endif
 273
 274 #ifdef CONFIG_HIBERNATION
 275         case LINUX_REBOOT_CMD_SW_SUSPEND:
 276                 ret = hibernate();
 277                 break;
 278 #endif
 279
 280         default:
 281                 ret = -EINVAL;
 282                 break;
 283         }
 284         mutex_unlock(&reboot_mutex);
 285         return ret;
 286 }
 287
 288 static void deferred_cad(struct work_struct *dummy)
 289 {
 290         kernel_restart(NULL);
 291 }
 292
 293 /*
 294  * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
 295  * As it's called within an interrupt, it may NOT sync: the only choice
 296  * is whether to reboot at once, or just ignore the ctrl-alt-del.
 297  */
 298 void ctrl_alt_del(void)
 299 {
 300         static DECLARE_WORK(cad_work, deferred_cad);
 301
 302         if (C_A_D)
 303                 schedule_work(&cad_work);
 304         else
 305                 kill_cad_pid(SIGINT, 1);
 306 }
 307
 308 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
 309
 310 static int __orderly_poweroff(bool force)
 311 {
 312         char **argv;
 313         static char *envp[] = {
 314                 "HOME=/",
 315                 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
 316                 NULL
 317         };
 318         int ret;
 319
 320         argv = argv_split(GFP_KERNEL, poweroff_cmd, NULL);
 321         if (argv) {
 322                 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
 323                 argv_free(argv);
 324         } else {
 325                 ret = -ENOMEM;
 326         }
 327
 328         if (ret && force) {
 329                 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
 330                 /*
 331                  * I guess this should try to kick off some daemon to sync and
 332                  * poweroff asap.  Or not even bother syncing if we're doing an
 333                  * emergency shutdown?
 334                  */
 335                 emergency_sync();
 336                 kernel_power_off();
 337         }
 338
 339         return ret;
 340 }
 341
 342 static bool poweroff_force;
 343
 344 static void poweroff_work_func(struct work_struct *work)
 345 {
 346         __orderly_poweroff(poweroff_force);
 347 }
 348
 349 static DECLARE_WORK(poweroff_work, poweroff_work_func);
 350
 351 /**
 352  * orderly_poweroff - Trigger an orderly system poweroff
 353  * @force: force poweroff if command execution fails
 354  *
 355  * This may be called from any context to trigger a system shutdown.
 356  * If the orderly shutdown fails, it will force an immediate shutdown.
 357  */
 358 int orderly_poweroff(bool force)
 359 {
 360         if (force) /* do not override the pending "true" */
 361                 poweroff_force = true;
 362         schedule_work(&poweroff_work);
 363         return 0;
 364 }
 365 EXPORT_SYMBOL_GPL(orderly_poweroff);
 366
 367 static int __init reboot_setup(char *str)
 368 {
 369         for (;;) {
 370                 /*
 371                  * Having anything passed on the command line via
 372                  * reboot= will cause us to disable DMI checking
 373                  * below.
 374                  */
 375                 reboot_default = 0;
 376
 377                 switch (*str) {
 378                 case 'w':
 379                         reboot_mode = REBOOT_WARM;
 380                         break;
 381
 382                 case 'c':
 383                         reboot_mode = REBOOT_COLD;
 384                         break;
 385
 386                 case 'h':
 387                         reboot_mode = REBOOT_HARD;
 388                         break;
 389
 390                 case 's':
 391                         if (isdigit(*(str+1)))
 392                                 reboot_cpu = simple_strtoul(str+1, NULL, 0);
 393                         else if (str[1] == 'm' && str[2] == 'p' &&
 394                                                         isdigit(*(str+3)))
 395                                 reboot_cpu = simple_strtoul(str+3, NULL, 0);
 396                         else
 397                                 reboot_mode = REBOOT_SOFT;
 398                         break;
 399
 400                 case 'g':
 401                         reboot_mode = REBOOT_GPIO;
 402                         break;
 403
 404                 case 'b':
 405                 case 'a':
 406                 case 'k':
 407                 case 't':
 408                 case 'e':
 409                 case 'p':
 410                         reboot_type = *str;
 411                         break;
 412
 413                 case 'f':
 414                         reboot_force = 1;
 415                         break;
 416                 }
 417
 418                 str = strchr(str, ',');
 419                 if (str)
 420                         str++;
 421                 else
 422                         break;
 423         }
 424         return 1;
 425 }
 426 __setup("reboot=", reboot_setup);