staging: comedi: cb_pcidas: tidy up cb_pcidas_trimpot_write()

[linux/fpc-iii.git] / kernel / reboot.c

/*
 *  linux/kernel/reboot.c
 *
 *  Copyright (C) 2013  Linus Torvalds
 */

#define pr_fmt(fmt)     "reboot: " fmt

#include <linux/ctype.h>
#include <linux/export.h>
#include <linux/kexec.h>
#include <linux/kmod.h>
#include <linux/kmsg_dump.h>
#include <linux/reboot.h>
#include <linux/suspend.h>
#include <linux/syscalls.h>
#include <linux/syscore_ops.h>
#include <linux/uaccess.h>

/*
 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
 */

int C_A_D = 1;
struct pid *cad_pid;
EXPORT_SYMBOL(cad_pid);

#if defined(CONFIG_ARM) || defined(CONFIG_UNICORE32)
#define DEFAULT_REBOOT_MODE             = REBOOT_HARD
#else
#define DEFAULT_REBOOT_MODE
#endif
enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;

/*
 * This variable is used privately to keep track of whether or not
 * reboot_type is still set to its default value (i.e., reboot= hasn't
 * been set on the command line).  This is needed so that we can
 * suppress DMI scanning for reboot quirks.  Without it, it's
 * impossible to override a faulty reboot quirk without recompiling.
 */
int reboot_default = 1;
int reboot_cpu;
enum reboot_type reboot_type = BOOT_ACPI;
int reboot_force;

/*
 * If set, this is used for preparing the system to power off.
 */

void (*pm_power_off_prepare)(void);

/**
 *      emergency_restart - reboot the system
 *
 *      Without shutting down any hardware or taking any locks
 *      reboot the system.  This is called when we know we are in
 *      trouble so this is our best effort to reboot.  This is
 *      safe to call in interrupt context.
 */
void emergency_restart(void)
{
        kmsg_dump(KMSG_DUMP_EMERG);
        machine_emergency_restart();
}
EXPORT_SYMBOL_GPL(emergency_restart);

void kernel_restart_prepare(char *cmd)
{
        blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
        system_state = SYSTEM_RESTART;
        usermodehelper_disable();
        device_shutdown();
}

/**
 *      register_reboot_notifier - Register function to be called at reboot time
 *      @nb: Info about notifier function to be called
 *
 *      Registers a function with the list of functions
 *      to be called at reboot time.
 *
 *      Currently always returns zero, as blocking_notifier_chain_register()
 *      always returns zero.
 */
int register_reboot_notifier(struct notifier_block *nb)
{
        return blocking_notifier_chain_register(&reboot_notifier_list, nb);
}
EXPORT_SYMBOL(register_reboot_notifier);

/**
 *      unregister_reboot_notifier - Unregister previously registered reboot notifier
 *      @nb: Hook to be unregistered
 *
 *      Unregisters a previously registered reboot
 *      notifier function.
 *
 *      Returns zero on success, or %-ENOENT on failure.
 */
int unregister_reboot_notifier(struct notifier_block *nb)
{
        return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
}
EXPORT_SYMBOL(unregister_reboot_notifier);

/*
 *      Notifier list for kernel code which wants to be called
 *      to restart the system.
 */
static ATOMIC_NOTIFIER_HEAD(restart_handler_list);

/**
 *      register_restart_handler - Register function to be called to reset
 *                                 the system
 *      @nb: Info about handler function to be called
 *      @nb->priority:  Handler priority. Handlers should follow the
 *                      following guidelines for setting priorities.
 *                      0:      Restart handler of last resort,
 *                              with limited restart capabilities
 *                      128:    Default restart handler; use if no other
 *                              restart handler is expected to be available,
 *                              and/or if restart functionality is
 *                              sufficient to restart the entire system
 *                      255:    Highest priority restart handler, will
 *                              preempt all other restart handlers
 *
 *      Registers a function with code to be called to restart the
 *      system.
 *
 *      Registered functions will be called from machine_restart as last
 *      step of the restart sequence (if the architecture specific
 *      machine_restart function calls do_kernel_restart - see below
 *      for details).
 *      Registered functions are expected to restart the system immediately.
 *      If more than one function is registered, the restart handler priority
 *      selects which function will be called first.
 *
 *      Restart handlers are expected to be registered from non-architecture
 *      code, typically from drivers. A typical use case would be a system
 *      where restart functionality is provided through a watchdog. Multiple
 *      restart handlers may exist; for example, one restart handler might
 *      restart the entire system, while another only restarts the CPU.
 *      In such cases, the restart handler which only restarts part of the
 *      hardware is expected to register with low priority to ensure that
 *      it only runs if no other means to restart the system is available.
 *
 *      Currently always returns zero, as atomic_notifier_chain_register()
 *      always returns zero.
 */
int register_restart_handler(struct notifier_block *nb)
{
        return atomic_notifier_chain_register(&restart_handler_list, nb);
}
EXPORT_SYMBOL(register_restart_handler);

/**
 *      unregister_restart_handler - Unregister previously registered
 *                                   restart handler
 *      @nb: Hook to be unregistered
 *
 *      Unregisters a previously registered restart handler function.
 *
 *      Returns zero on success, or %-ENOENT on failure.
 */
int unregister_restart_handler(struct notifier_block *nb)
{
        return atomic_notifier_chain_unregister(&restart_handler_list, nb);
}
EXPORT_SYMBOL(unregister_restart_handler);

/**
 *      do_kernel_restart - Execute kernel restart handler call chain
 *
 *      Calls functions registered with register_restart_handler.
 *
 *      Expected to be called from machine_restart as last step of the restart
 *      sequence.
 *
 *      Restarts the system immediately if a restart handler function has been
 *      registered. Otherwise does nothing.
 */
void do_kernel_restart(char *cmd)
{
        atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
}

void migrate_to_reboot_cpu(void)
{
        /* The boot cpu is always logical cpu 0 */
        int cpu = reboot_cpu;

        cpu_hotplug_disable();

        /* Make certain the cpu I'm about to reboot on is online */
        if (!cpu_online(cpu))
                cpu = cpumask_first(cpu_online_mask);

        /* Prevent races with other tasks migrating this task */
        current->flags |= PF_NO_SETAFFINITY;

        /* Make certain I only run on the appropriate processor */
        set_cpus_allowed_ptr(current, cpumask_of(cpu));
}

/**
 *      kernel_restart - reboot the system
 *      @cmd: pointer to buffer containing command to execute for restart
 *              or %NULL
 *
 *      Shutdown everything and perform a clean reboot.
 *      This is not safe to call in interrupt context.
 */
void kernel_restart(char *cmd)
{
        kernel_restart_prepare(cmd);
        migrate_to_reboot_cpu();
        syscore_shutdown();
        if (!cmd)
                pr_emerg("Restarting system\n");
        else
                pr_emerg("Restarting system with command '%s'\n", cmd);
        kmsg_dump(KMSG_DUMP_RESTART);
        machine_restart(cmd);
}
EXPORT_SYMBOL_GPL(kernel_restart);

static void kernel_shutdown_prepare(enum system_states state)
{
        blocking_notifier_call_chain(&reboot_notifier_list,
                (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
        system_state = state;
        usermodehelper_disable();
        device_shutdown();
}
/**
 *      kernel_halt - halt the system
 *
 *      Shutdown everything and perform a clean system halt.
 */
void kernel_halt(void)
{
        kernel_shutdown_prepare(SYSTEM_HALT);
        migrate_to_reboot_cpu();
        syscore_shutdown();
        pr_emerg("System halted\n");
        kmsg_dump(KMSG_DUMP_HALT);
        machine_halt();
}
EXPORT_SYMBOL_GPL(kernel_halt);

/**
 *      kernel_power_off - power_off the system
 *
 *      Shutdown everything and perform a clean system power_off.
 */
void kernel_power_off(void)
{
        kernel_shutdown_prepare(SYSTEM_POWER_OFF);
        if (pm_power_off_prepare)
                pm_power_off_prepare();
        migrate_to_reboot_cpu();
        syscore_shutdown();
        pr_emerg("Power down\n");
        kmsg_dump(KMSG_DUMP_POWEROFF);
        machine_power_off();
}
EXPORT_SYMBOL_GPL(kernel_power_off);

static DEFINE_MUTEX(reboot_mutex);

/*
 * Reboot system call: for obvious reasons only root may call it,
 * and even root needs to set up some magic numbers in the registers
 * so that some mistake won't make this reboot the whole machine.
 * You can also set the meaning of the ctrl-alt-del-key here.
 *
 * reboot doesn't sync: do that yourself before calling this.
 */
SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
                void __user *, arg)
{
        struct pid_namespace *pid_ns = task_active_pid_ns(current);
        char buffer[256];
        int ret = 0;

        /* We only trust the superuser with rebooting the system. */
        if (!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))
                return -EPERM;

        /* For safety, we require "magic" arguments. */
        if (magic1 != LINUX_REBOOT_MAGIC1 ||
                        (magic2 != LINUX_REBOOT_MAGIC2 &&
                        magic2 != LINUX_REBOOT_MAGIC2A &&
                        magic2 != LINUX_REBOOT_MAGIC2B &&
                        magic2 != LINUX_REBOOT_MAGIC2C))
                return -EINVAL;

        /*
         * If pid namespaces are enabled and the current task is in a child
         * pid_namespace, the command is handled by reboot_pid_ns() which will
         * call do_exit().
         */
        ret = reboot_pid_ns(pid_ns, cmd);
        if (ret)
                return ret;

        /* Instead of trying to make the power_off code look like
         * halt when pm_power_off is not set do it the easy way.
         */
        if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
                cmd = LINUX_REBOOT_CMD_HALT;

        mutex_lock(&reboot_mutex);
        switch (cmd) {
        case LINUX_REBOOT_CMD_RESTART:
                kernel_restart(NULL);
                break;

        case LINUX_REBOOT_CMD_CAD_ON:
                C_A_D = 1;
                break;

        case LINUX_REBOOT_CMD_CAD_OFF:
                C_A_D = 0;
                break;

        case LINUX_REBOOT_CMD_HALT:
                kernel_halt();
                do_exit(0);
                panic("cannot halt");

        case LINUX_REBOOT_CMD_POWER_OFF:
                kernel_power_off();
                do_exit(0);
                break;

        case LINUX_REBOOT_CMD_RESTART2:
                ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
                if (ret < 0) {
                        ret = -EFAULT;
                        break;
                }
                buffer[sizeof(buffer) - 1] = '\0';

                kernel_restart(buffer);
                break;

#ifdef CONFIG_KEXEC_CORE
        case LINUX_REBOOT_CMD_KEXEC:
                ret = kernel_kexec();
                break;
#endif

#ifdef CONFIG_HIBERNATION
        case LINUX_REBOOT_CMD_SW_SUSPEND:
                ret = hibernate();
                break;
#endif

        default:
                ret = -EINVAL;
                break;
        }
        mutex_unlock(&reboot_mutex);
        return ret;
}

static void deferred_cad(struct work_struct *dummy)
{
        kernel_restart(NULL);
}

/*
 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
 * As it's called within an interrupt, it may NOT sync: the only choice
 * is whether to reboot at once, or just ignore the ctrl-alt-del.
 */
void ctrl_alt_del(void)
{
        static DECLARE_WORK(cad_work, deferred_cad);

        if (C_A_D)
                schedule_work(&cad_work);
        else
                kill_cad_pid(SIGINT, 1);
}

char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
static const char reboot_cmd[] = "/sbin/reboot";

static int run_cmd(const char *cmd)
{
        char **argv;
        static char *envp[] = {
                "HOME=/",
                "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
                NULL
        };
        int ret;
        argv = argv_split(GFP_KERNEL, cmd, NULL);
        if (argv) {
                ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
                argv_free(argv);
        } else {
                ret = -ENOMEM;
        }

        return ret;
}

static int __orderly_reboot(void)
{
        int ret;

        ret = run_cmd(reboot_cmd);

        if (ret) {
                pr_warn("Failed to start orderly reboot: forcing the issue\n");
                emergency_sync();
                kernel_restart(NULL);
        }

        return ret;
}

static int __orderly_poweroff(bool force)
{
        int ret;

        ret = run_cmd(poweroff_cmd);

        if (ret && force) {
                pr_warn("Failed to start orderly shutdown: forcing the issue\n");

                /*
                 * I guess this should try to kick off some daemon to sync and
                 * poweroff asap.  Or not even bother syncing if we're doing an
                 * emergency shutdown?
                 */
                emergency_sync();
                kernel_power_off();
        }

        return ret;
}

static bool poweroff_force;

static void poweroff_work_func(struct work_struct *work)
{
        __orderly_poweroff(poweroff_force);
}

static DECLARE_WORK(poweroff_work, poweroff_work_func);

/**
 * orderly_poweroff - Trigger an orderly system poweroff
 * @force: force poweroff if command execution fails
 *
 * This may be called from any context to trigger a system shutdown.
 * If the orderly shutdown fails, it will force an immediate shutdown.
 */
void orderly_poweroff(bool force)
{
        if (force) /* do not override the pending "true" */
                poweroff_force = true;
        schedule_work(&poweroff_work);
}
EXPORT_SYMBOL_GPL(orderly_poweroff);

static void reboot_work_func(struct work_struct *work)
{
        __orderly_reboot();
}

static DECLARE_WORK(reboot_work, reboot_work_func);

/**
 * orderly_reboot - Trigger an orderly system reboot
 *
 * This may be called from any context to trigger a system reboot.
 * If the orderly reboot fails, it will force an immediate reboot.
 */
void orderly_reboot(void)
{
        schedule_work(&reboot_work);
}
EXPORT_SYMBOL_GPL(orderly_reboot);

static int __init reboot_setup(char *str)
{
        for (;;) {
                /*
                 * Having anything passed on the command line via
                 * reboot= will cause us to disable DMI checking
                 * below.
                 */
                reboot_default = 0;

                switch (*str) {
                case 'w':
                        reboot_mode = REBOOT_WARM;
                        break;

                case 'c':
                        reboot_mode = REBOOT_COLD;
                        break;

                case 'h':
                        reboot_mode = REBOOT_HARD;
                        break;

                case 's':
                {
                        int rc;

                        if (isdigit(*(str+1))) {
                                rc = kstrtoint(str+1, 0, &reboot_cpu);
                                if (rc)
                                        return rc;
                        } else if (str[1] == 'm' && str[2] == 'p' &&
                                   isdigit(*(str+3))) {
                                rc = kstrtoint(str+3, 0, &reboot_cpu);
                                if (rc)
                                        return rc;
                        } else
                                reboot_mode = REBOOT_SOFT;
                        break;
                }
                case 'g':
                        reboot_mode = REBOOT_GPIO;
                        break;

                case 'b':
                case 'a':
                case 'k':
                case 't':
                case 'e':
                case 'p':
                        reboot_type = *str;
                        break;

                case 'f':
                        reboot_force = 1;
                        break;
                }

                str = strchr(str, ',');
                if (str)
                        str++;
                else
                        break;
        }
        return 1;
}
__setup("reboot=", reboot_setup);