Root/kernel/reboot.c

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
107void 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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