cregit-Linux how code gets into the kernel

Release 4.9 kernel/reboot.c

Directory: kernel
/*
 *  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(); }

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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(); }

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/** * 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); }

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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); }

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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); }

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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); }

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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); }

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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)); }

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/** * 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); }

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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(); }

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/** * 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(); }

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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(); }

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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); }

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/* * 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); }

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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; }

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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; }

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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; }

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

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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); }

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

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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); }

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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; }

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__setup("reboot=", reboot_setup);

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Directory: kernel