linux/kernel/reboot.c
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   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
  24int C_A_D = 1;
  25struct pid *cad_pid;
  26EXPORT_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
  33enum 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 */
  42int reboot_default = 1;
  43int reboot_cpu;
  44enum reboot_type reboot_type = BOOT_ACPI;
  45int reboot_force;
  46
  47/*
  48 * If set, this is used for preparing the system to power off.
  49 */
  50
  51void (*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 */
  61void emergency_restart(void)
  62{
  63        kmsg_dump(KMSG_DUMP_EMERG);
  64        machine_emergency_restart();
  65}
  66EXPORT_SYMBOL_GPL(emergency_restart);
  67
  68void 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 */
  86int register_reboot_notifier(struct notifier_block *nb)
  87{
  88        return blocking_notifier_chain_register(&reboot_notifier_list, nb);
  89}
  90EXPORT_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 */
 101int unregister_reboot_notifier(struct notifier_block *nb)
 102{
 103        return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
 104}
 105EXPORT_SYMBOL(unregister_reboot_notifier);
 106
 107static 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 */
 133void 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}
 145EXPORT_SYMBOL_GPL(kernel_restart);
 146
 147static 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 */
 160void 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}
 169EXPORT_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 */
 176void 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}
 187EXPORT_SYMBOL_GPL(kernel_power_off);
 188
 189static 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 */
 199SYSCALL_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
 288static 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 */
 298void 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
 308char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
 309
 310static 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
 342static bool poweroff_force;
 343
 344static void poweroff_work_func(struct work_struct *work)
 345{
 346        __orderly_poweroff(poweroff_force);
 347}
 348
 349static 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 */
 358int 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}
 365EXPORT_SYMBOL_GPL(orderly_poweroff);
 366
 367static 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);
 427
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