// SPDX-License-Identifier: GPL-2.0-only /* * linux/kernel/reboot.c * * Copyright (C) 2013 Linus Torvalds */ #define pr_fmt(fmt) "reboot: " fmt #include <linux/atomic.h> #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) #define DEFAULT_REBOOT_MODE = REBOOT_HARD #else #define DEFAULT_REBOOT_MODE #endif enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE; EXPORT_SYMBOL_GPL(reboot_mode); enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED; /* * 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_SHUTDOWN); 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_SHUTDOWN); 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_SHUTDOWN); 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); 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(&system_transition_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); /** * hw_failure_emergency_poweroff_func - emergency poweroff work after a known delay * @work: work_struct associated with the emergency poweroff function * * This function is called in very critical situations to force * a kernel poweroff after a configurable timeout value. */ static void hw_failure_emergency_poweroff_func(struct work_struct *work) { /* * We have reached here after the emergency shutdown waiting period has * expired. This means orderly_poweroff has not been able to shut off * the system for some reason. * * Try to shut down the system immediately using kernel_power_off * if populated */ pr_emerg("Hardware protection timed-out. Trying forced poweroff\n"); kernel_power_off(); /* * Worst of the worst case trigger emergency restart */ pr_emerg("Hardware protection shutdown failed. Trying emergency restart\n"); emergency_restart(); } static DECLARE_DELAYED_WORK(hw_failure_emergency_poweroff_work, hw_failure_emergency_poweroff_func); /** * hw_failure_emergency_poweroff - Trigger an emergency system poweroff * * This may be called from any critical situation to trigger a system shutdown * after a given period of time. If time is negative this is not scheduled. */ static void hw_failure_emergency_poweroff(int poweroff_delay_ms) { if (poweroff_delay_ms <= 0) return; schedule_delayed_work(&hw_failure_emergency_poweroff_work, msecs_to_jiffies(poweroff_delay_ms)); } /** * hw_protection_shutdown - Trigger an emergency system poweroff * * @reason: Reason of emergency shutdown to be printed. * @ms_until_forced: Time to wait for orderly shutdown before tiggering a * forced shudown. Negative value disables the forced * shutdown. * * Initiate an emergency system shutdown in order to protect hardware from * further damage. Usage examples include a thermal protection or a voltage or * current regulator failures. * NOTE: The request is ignored if protection shutdown is already pending even * if the previous request has given a large timeout for forced shutdown. * Can be called from any context. */ void hw_protection_shutdown(const char *reason, int ms_until_forced) { static atomic_t allow_proceed = ATOMIC_INIT(1); pr_emerg("HARDWARE PROTECTION shutdown (%s)\n", reason); /* Shutdown should be initiated only once. */ if (!atomic_dec_and_test(&allow_proceed)) return; /* * Queue a backup emergency shutdown in the event of * orderly_poweroff failure */ hw_failure_emergency_poweroff(ms_until_forced); orderly_poweroff(true); } EXPORT_SYMBOL_GPL(hw_protection_shutdown); static int __init reboot_setup(char *str) { for (;;) { enum reboot_mode *mode; /* * Having anything passed on the command line via * reboot= will cause us to disable DMI checking * below. */ reboot_default = 0; if (!strncmp(str, "panic_", 6)) { mode = &panic_reboot_mode; str += 6; } else { mode = &reboot_mode; } switch (*str) { case 'w': *mode = REBOOT_WARM; break; case 'c': *mode = REBOOT_COLD; break; case 'h': *mode = REBOOT_HARD; break; case 's': /* * reboot_cpu is s[mp]#### with #### being the processor * to be used for rebooting. Skip 's' or 'smp' prefix. */ str += str[1] == 'm' && str[2] == 'p' ? 3 : 1; if (isdigit(str[0])) { int cpu = simple_strtoul(str, NULL, 0); if (cpu >= num_possible_cpus()) { pr_err("Ignoring the CPU number in reboot= option. " "CPU %d exceeds possible cpu number %d\n", cpu, num_possible_cpus()); break; } reboot_cpu = cpu; } else *mode = REBOOT_SOFT; break; case 'g': *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); #ifdef CONFIG_SYSFS #define REBOOT_COLD_STR "cold" #define REBOOT_WARM_STR "warm" #define REBOOT_HARD_STR "hard" #define REBOOT_SOFT_STR "soft" #define REBOOT_GPIO_STR "gpio" #define REBOOT_UNDEFINED_STR "undefined" #define BOOT_TRIPLE_STR "triple" #define BOOT_KBD_STR "kbd" #define BOOT_BIOS_STR "bios" #define BOOT_ACPI_STR "acpi" #define BOOT_EFI_STR "efi" #define BOOT_PCI_STR "pci" static ssize_t mode_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { const char *val; switch (reboot_mode) { case REBOOT_COLD: val = REBOOT_COLD_STR; break; case REBOOT_WARM: val = REBOOT_WARM_STR; break; case REBOOT_HARD: val = REBOOT_HARD_STR; break; case REBOOT_SOFT: val = REBOOT_SOFT_STR; break; case REBOOT_GPIO: val = REBOOT_GPIO_STR; break; default: val = REBOOT_UNDEFINED_STR; } return sprintf(buf, "%s\n", val); } static ssize_t mode_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { if (!capable(CAP_SYS_BOOT)) return -EPERM; if (!strncmp(buf, REBOOT_COLD_STR, strlen(REBOOT_COLD_STR))) reboot_mode = REBOOT_COLD; else if (!strncmp(buf, REBOOT_WARM_STR, strlen(REBOOT_WARM_STR))) reboot_mode = REBOOT_WARM; else if (!strncmp(buf, REBOOT_HARD_STR, strlen(REBOOT_HARD_STR))) reboot_mode = REBOOT_HARD; else if (!strncmp(buf, REBOOT_SOFT_STR, strlen(REBOOT_SOFT_STR))) reboot_mode = REBOOT_SOFT; else if (!strncmp(buf, REBOOT_GPIO_STR, strlen(REBOOT_GPIO_STR))) reboot_mode = REBOOT_GPIO; else return -EINVAL; reboot_default = 0; return count; } static struct kobj_attribute reboot_mode_attr = __ATTR_RW(mode); #ifdef CONFIG_X86 static ssize_t force_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return sprintf(buf, "%d\n", reboot_force); } static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { bool res; if (!capable(CAP_SYS_BOOT)) return -EPERM; if (kstrtobool(buf, &res)) return -EINVAL; reboot_default = 0; reboot_force = res; return count; } static struct kobj_attribute reboot_force_attr = __ATTR_RW(force); static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { const char *val; switch (reboot_type) { case BOOT_TRIPLE: val = BOOT_TRIPLE_STR; break; case BOOT_KBD: val = BOOT_KBD_STR; break; case BOOT_BIOS: val = BOOT_BIOS_STR; break; case BOOT_ACPI: val = BOOT_ACPI_STR; break; case BOOT_EFI: val = BOOT_EFI_STR; break; case BOOT_CF9_FORCE: val = BOOT_PCI_STR; break; default: val = REBOOT_UNDEFINED_STR; } return sprintf(buf, "%s\n", val); } static ssize_t type_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { if (!capable(CAP_SYS_BOOT)) return -EPERM; if (!strncmp(buf, BOOT_TRIPLE_STR, strlen(BOOT_TRIPLE_STR))) reboot_type = BOOT_TRIPLE; else if (!strncmp(buf, BOOT_KBD_STR, strlen(BOOT_KBD_STR))) reboot_type = BOOT_KBD; else if (!strncmp(buf, BOOT_BIOS_STR, strlen(BOOT_BIOS_STR))) reboot_type = BOOT_BIOS; else if (!strncmp(buf, BOOT_ACPI_STR, strlen(BOOT_ACPI_STR))) reboot_type = BOOT_ACPI; else if (!strncmp(buf, BOOT_EFI_STR, strlen(BOOT_EFI_STR))) reboot_type = BOOT_EFI; else if (!strncmp(buf, BOOT_PCI_STR, strlen(BOOT_PCI_STR))) reboot_type = BOOT_CF9_FORCE; else return -EINVAL; reboot_default = 0; return count; } static struct kobj_attribute reboot_type_attr = __ATTR_RW(type); #endif #ifdef CONFIG_SMP static ssize_t cpu_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return sprintf(buf, "%d\n", reboot_cpu); } static ssize_t cpu_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { unsigned int cpunum; int rc; if (!capable(CAP_SYS_BOOT)) return -EPERM; rc = kstrtouint(buf, 0, &cpunum); if (rc) return rc; if (cpunum >= num_possible_cpus()) return -ERANGE; reboot_default = 0; reboot_cpu = cpunum; return count; } static struct kobj_attribute reboot_cpu_attr = __ATTR_RW(cpu); #endif static struct attribute *reboot_attrs[] = { &reboot_mode_attr.attr, #ifdef CONFIG_X86 &reboot_force_attr.attr, &reboot_type_attr.attr, #endif #ifdef CONFIG_SMP &reboot_cpu_attr.attr, #endif NULL, }; static const struct attribute_group reboot_attr_group = { .attrs = reboot_attrs, }; static int __init reboot_ksysfs_init(void) { struct kobject *reboot_kobj; int ret; reboot_kobj = kobject_create_and_add("reboot", kernel_kobj); if (!reboot_kobj) return -ENOMEM; ret = sysfs_create_group(reboot_kobj, &reboot_attr_group); if (ret) { kobject_put(reboot_kobj); return ret; } return 0; } late_initcall(reboot_ksysfs_init); #endif