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 int reboot_default;
  36 int reboot_cpu;
  37 enum reboot_type reboot_type = BOOT_ACPI;
  38 int reboot_force;
  39
  40 /*
  41  * If set, this is used for preparing the system to power off.
  42  */
  43
  44 void (*pm_power_off_prepare)(void);
  45
  46 /**
  47  *      emergency_restart - reboot the system
  48  *
  49  *      Without shutting down any hardware or taking any locks
  50  *      reboot the system.  This is called when we know we are in
  51  *      trouble so this is our best effort to reboot.  This is
  52  *      safe to call in interrupt context.
  53  */
  54 void emergency_restart(void)
  55 {
  56         kmsg_dump(KMSG_DUMP_EMERG);
  57         machine_emergency_restart();
  58 }
  59 EXPORT_SYMBOL_GPL(emergency_restart);
  60
  61 void kernel_restart_prepare(char *cmd)
  62 {
  63         blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
  64         system_state = SYSTEM_RESTART;
  65         usermodehelper_disable();
  66         device_shutdown();
  67 }
  68
  69 /**
  70  *      register_reboot_notifier - Register function to be called at reboot time
  71  *      @nb: Info about notifier function to be called
  72  *
  73  *      Registers a function with the list of functions
  74  *      to be called at reboot time.
  75  *
  76  *      Currently always returns zero, as blocking_notifier_chain_register()
  77  *      always returns zero.
  78  */
  79 int register_reboot_notifier(struct notifier_block *nb)
  80 {
  81         return blocking_notifier_chain_register(&reboot_notifier_list, nb);
  82 }
  83 EXPORT_SYMBOL(register_reboot_notifier);
  84
  85 /**
  86  *      unregister_reboot_notifier - Unregister previously registered reboot notifier
  87  *      @nb: Hook to be unregistered
  88  *
  89  *      Unregisters a previously registered reboot
  90  *      notifier function.
  91  *
  92  *      Returns zero on success, or %-ENOENT on failure.
  93  */
  94 int unregister_reboot_notifier(struct notifier_block *nb)
  95 {
  96         return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
  97 }
  98 EXPORT_SYMBOL(unregister_reboot_notifier);
  99
 100 static void migrate_to_reboot_cpu(void)
 101 {
 102         /* The boot cpu is always logical cpu 0 */
 103         int cpu = reboot_cpu;
 104
 105         cpu_hotplug_disable();
 106
 107         /* Make certain the cpu I'm about to reboot on is online */
 108         if (!cpu_online(cpu))
 109                 cpu = cpumask_first(cpu_online_mask);
 110
 111         /* Prevent races with other tasks migrating this task */
 112         current->flags |= PF_NO_SETAFFINITY;
 113
 114         /* Make certain I only run on the appropriate processor */
 115         set_cpus_allowed_ptr(current, cpumask_of(cpu));
 116 }
 117
 118 /**
 119  *      kernel_restart - reboot the system
 120  *      @cmd: pointer to buffer containing command to execute for restart
 121  *              or %NULL
 122  *
 123  *      Shutdown everything and perform a clean reboot.
 124  *      This is not safe to call in interrupt context.
 125  */
 126 void kernel_restart(char *cmd)
 127 {
 128         kernel_restart_prepare(cmd);
 129         migrate_to_reboot_cpu();
 130         syscore_shutdown();
 131         if (!cmd)
 132                 pr_emerg("Restarting system\n");
 133         else
 134                 pr_emerg("Restarting system with command '%s'\n", cmd);
 135         kmsg_dump(KMSG_DUMP_RESTART);
 136         machine_restart(cmd);
 137 }
 138 EXPORT_SYMBOL_GPL(kernel_restart);
 139
 140 static void kernel_shutdown_prepare(enum system_states state)
 141 {
 142         blocking_notifier_call_chain(&reboot_notifier_list,
 143                 (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
 144         system_state = state;
 145         usermodehelper_disable();
 146         device_shutdown();
 147 }
 148 /**
 149  *      kernel_halt - halt the system
 150  *
 151  *      Shutdown everything and perform a clean system halt.
 152  */
 153 void kernel_halt(void)
 154 {
 155         kernel_shutdown_prepare(SYSTEM_HALT);
 156         migrate_to_reboot_cpu();
 157         syscore_shutdown();
 158         pr_emerg("System halted\n");
 159         kmsg_dump(KMSG_DUMP_HALT);
 160         machine_halt();
 161 }
 162 EXPORT_SYMBOL_GPL(kernel_halt);
 163
 164 /**
 165  *      kernel_power_off - power_off the system
 166  *
 167  *      Shutdown everything and perform a clean system power_off.
 168  */
 169 void kernel_power_off(void)
 170 {
 171         kernel_shutdown_prepare(SYSTEM_POWER_OFF);
 172         if (pm_power_off_prepare)
 173                 pm_power_off_prepare();
 174         migrate_to_reboot_cpu();
 175         syscore_shutdown();
 176         pr_emerg("Power down\n");
 177         kmsg_dump(KMSG_DUMP_POWEROFF);
 178         machine_power_off();
 179 }
 180 EXPORT_SYMBOL_GPL(kernel_power_off);
 181
 182 static DEFINE_MUTEX(reboot_mutex);
 183
 184 /*
 185  * Reboot system call: for obvious reasons only root may call it,
 186  * and even root needs to set up some magic numbers in the registers
 187  * so that some mistake won't make this reboot the whole machine.
 188  * You can also set the meaning of the ctrl-alt-del-key here.
 189  *
 190  * reboot doesn't sync: do that yourself before calling this.
 191  */
 192 SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 193                 void __user *, arg)
 194 {
 195         struct pid_namespace *pid_ns = task_active_pid_ns(current);
 196         char buffer[256];
 197         int ret = 0;
 198
 199         /* We only trust the superuser with rebooting the system. */
 200         if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
 201                 return -EPERM;
 202
 203         /* For safety, we require "magic" arguments. */
 204         if (magic1 != LINUX_REBOOT_MAGIC1 ||
 205                         (magic2 != LINUX_REBOOT_MAGIC2 &&
 206                         magic2 != LINUX_REBOOT_MAGIC2A &&
 207                         magic2 != LINUX_REBOOT_MAGIC2B &&
 208                         magic2 != LINUX_REBOOT_MAGIC2C))
 209                 return -EINVAL;
 210
 211         /*
 212          * If pid namespaces are enabled and the current task is in a child
 213          * pid_namespace, the command is handled by reboot_pid_ns() which will
 214          * call do_exit().
 215          */
 216         ret = reboot_pid_ns(pid_ns, cmd);
 217         if (ret)
 218                 return ret;
 219
 220         /* Instead of trying to make the power_off code look like
 221          * halt when pm_power_off is not set do it the easy way.
 222          */
 223         if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
 224                 cmd = LINUX_REBOOT_CMD_HALT;
 225
 226         mutex_lock(&reboot_mutex);
 227         switch (cmd) {
 228         case LINUX_REBOOT_CMD_RESTART:
 229                 kernel_restart(NULL);
 230                 break;
 231
 232         case LINUX_REBOOT_CMD_CAD_ON:
 233                 C_A_D = 1;
 234                 break;
 235
 236         case LINUX_REBOOT_CMD_CAD_OFF:
 237                 C_A_D = 0;
 238                 break;
 239
 240         case LINUX_REBOOT_CMD_HALT:
 241                 kernel_halt();
 242                 do_exit(0);
 243                 panic("cannot halt");
 244
 245         case LINUX_REBOOT_CMD_POWER_OFF:
 246                 kernel_power_off();
 247                 do_exit(0);
 248                 break;
 249
 250         case LINUX_REBOOT_CMD_RESTART2:
 251                 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
 252                 if (ret < 0) {
 253                         ret = -EFAULT;
 254                         break;
 255                 }
 256                 buffer[sizeof(buffer) - 1] = '\0';
 257
 258                 kernel_restart(buffer);
 259                 break;
 260
 261 #ifdef CONFIG_KEXEC
 262         case LINUX_REBOOT_CMD_KEXEC:
 263                 ret = kernel_kexec();
 264                 break;
 265 #endif
 266
 267 #ifdef CONFIG_HIBERNATION
 268         case LINUX_REBOOT_CMD_SW_SUSPEND:
 269                 ret = hibernate();
 270                 break;
 271 #endif
 272
 273         default:
 274                 ret = -EINVAL;
 275                 break;
 276         }
 277         mutex_unlock(&reboot_mutex);
 278         return ret;
 279 }
 280
 281 static void deferred_cad(struct work_struct *dummy)
 282 {
 283         kernel_restart(NULL);
 284 }
 285
 286 /*
 287  * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
 288  * As it's called within an interrupt, it may NOT sync: the only choice
 289  * is whether to reboot at once, or just ignore the ctrl-alt-del.
 290  */
 291 void ctrl_alt_del(void)
 292 {
 293         static DECLARE_WORK(cad_work, deferred_cad);
 294
 295         if (C_A_D)
 296                 schedule_work(&cad_work);
 297         else
 298                 kill_cad_pid(SIGINT, 1);
 299 }
 300
 301 char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
 302
 303 static int __orderly_poweroff(bool force)
 304 {
 305         char **argv;
 306         static char *envp[] = {
 307                 "HOME=/",
 308                 "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
 309                 NULL
 310         };
 311         int ret;
 312
 313         argv = argv_split(GFP_KERNEL, poweroff_cmd, NULL);
 314         if (argv) {
 315                 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
 316                 argv_free(argv);
 317         } else {
 318                 ret = -ENOMEM;
 319         }
 320
 321         if (ret && force) {
 322                 pr_warn("Failed to start orderly shutdown: forcing the issue\n");
 323                 /*
 324                  * I guess this should try to kick off some daemon to sync and
 325                  * poweroff asap.  Or not even bother syncing if we're doing an
 326                  * emergency shutdown?
 327                  */
 328                 emergency_sync();
 329                 kernel_power_off();
 330         }
 331
 332         return ret;
 333 }
 334
 335 static bool poweroff_force;
 336
 337 static void poweroff_work_func(struct work_struct *work)
 338 {
 339         __orderly_poweroff(poweroff_force);
 340 }
 341
 342 static DECLARE_WORK(poweroff_work, poweroff_work_func);
 343
 344 /**
 345  * orderly_poweroff - Trigger an orderly system poweroff
 346  * @force: force poweroff if command execution fails
 347  *
 348  * This may be called from any context to trigger a system shutdown.
 349  * If the orderly shutdown fails, it will force an immediate shutdown.
 350  */
 351 int orderly_poweroff(bool force)
 352 {
 353         if (force) /* do not override the pending "true" */
 354                 poweroff_force = true;
 355         schedule_work(&poweroff_work);
 356         return 0;
 357 }
 358 EXPORT_SYMBOL_GPL(orderly_poweroff);
 359
 360 static int __init reboot_setup(char *str)
 361 {
 362         for (;;) {
 363                 /*
 364                  * Having anything passed on the command line via
 365                  * reboot= will cause us to disable DMI checking
 366                  * below.
 367                  */
 368                 reboot_default = 0;
 369
 370                 switch (*str) {
 371                 case 'w':
 372                         reboot_mode = REBOOT_WARM;
 373                         break;
 374
 375                 case 'c':
 376                         reboot_mode = REBOOT_COLD;
 377                         break;
 378
 379                 case 'h':
 380                         reboot_mode = REBOOT_HARD;
 381                         break;
 382
 383                 case 's':
 384                         if (isdigit(*(str+1)))
 385                                 reboot_cpu = simple_strtoul(str+1, NULL, 0);
 386                         else if (str[1] == 'm' && str[2] == 'p' &&
 387                                                         isdigit(*(str+3)))
 388                                 reboot_cpu = simple_strtoul(str+3, NULL, 0);
 389                         else
 390                                 reboot_mode = REBOOT_SOFT;
 391                         break;
 392
 393                 case 'g':
 394                         reboot_mode = REBOOT_GPIO;
 395                         break;
 396
 397                 case 'b':
 398                 case 'a':
 399                 case 'k':
 400                 case 't':
 401                 case 'e':
 402                 case 'p':
 403                         reboot_type = *str;
 404                         break;
 405
 406                 case 'f':
 407                         reboot_force = 1;
 408                         break;
 409                 }
 410
 411                 str = strchr(str, ',');
 412                 if (str)
 413                         str++;
 414                 else
 415                         break;
 416         }
 417         return 1;
 418 }
 419 __setup("reboot=", reboot_setup);