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/*
* 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);
EXPORT_SYMBOL_GPL(pm_power_off_prepare);
/**
* 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);
static void devm_unregister_reboot_notifier(struct device *dev, void *res)
{
WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
}
int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
{
struct notifier_block **rcnb;
int ret;
rcnb = devres_alloc(devm_unregister_reboot_notifier,
sizeof(*rcnb), GFP_KERNEL);
if (!rcnb)
return -ENOMEM;
ret = register_reboot_notifier(nb);
if (!ret) {
*rcnb = nb;
devres_add(dev, rcnb);
} else {
devres_free(rcnb);
}
return ret;
}
EXPORT_SYMBOL(devm_register_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);
DEFINE_MUTEX(system_transition_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(&system_transition_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);
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