2 * Linux Magic System Request Key Hacks
4 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
5 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
7 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
8 * overhauled to use key registration
9 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies
11 * Copyright (c) 2010 Dmitry Torokhov
12 * Input handler conversion
15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17 #include <linux/sched.h>
18 #include <linux/sched/rt.h>
19 #include <linux/interrupt.h>
22 #include <linux/mount.h>
23 #include <linux/kdev_t.h>
24 #include <linux/major.h>
25 #include <linux/reboot.h>
26 #include <linux/sysrq.h>
27 #include <linux/kbd_kern.h>
28 #include <linux/proc_fs.h>
29 #include <linux/nmi.h>
30 #include <linux/quotaops.h>
31 #include <linux/perf_event.h>
32 #include <linux/kernel.h>
33 #include <linux/module.h>
34 #include <linux/suspend.h>
35 #include <linux/writeback.h>
36 #include <linux/swap.h>
37 #include <linux/spinlock.h>
38 #include <linux/vt_kern.h>
39 #include <linux/workqueue.h>
40 #include <linux/hrtimer.h>
41 #include <linux/oom.h>
42 #include <linux/slab.h>
43 #include <linux/input.h>
44 #include <linux/uaccess.h>
46 #include <asm/ptrace.h>
47 #include <asm/irq_regs.h>
49 /* Whether we react on sysrq keys or just ignore them */
50 static int __read_mostly sysrq_enabled = SYSRQ_DEFAULT_ENABLE;
51 static bool __read_mostly sysrq_always_enabled;
53 static bool sysrq_on(void)
55 return sysrq_enabled || sysrq_always_enabled;
59 * A value of 1 means 'all', other nonzero values are an op mask:
61 static bool sysrq_on_mask(int mask)
63 return sysrq_always_enabled ||
65 (sysrq_enabled & mask);
68 static int __init sysrq_always_enabled_setup(char *str)
70 sysrq_always_enabled = true;
71 pr_info("sysrq always enabled.\n");
76 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
79 static void sysrq_handle_loglevel(int key)
85 printk("Loglevel set to %d\n", i);
88 static struct sysrq_key_op sysrq_loglevel_op = {
89 .handler = sysrq_handle_loglevel,
90 .help_msg = "loglevel(0-9)",
91 .action_msg = "Changing Loglevel",
92 .enable_mask = SYSRQ_ENABLE_LOG,
96 static void sysrq_handle_SAK(int key)
98 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
99 schedule_work(SAK_work);
101 static struct sysrq_key_op sysrq_SAK_op = {
102 .handler = sysrq_handle_SAK,
105 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
108 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
112 static void sysrq_handle_unraw(int key)
114 vt_reset_unicode(fg_console);
117 static struct sysrq_key_op sysrq_unraw_op = {
118 .handler = sysrq_handle_unraw,
120 .action_msg = "Keyboard mode set to system default",
121 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
124 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
125 #endif /* CONFIG_VT */
127 static void sysrq_handle_crash(int key)
131 panic_on_oops = 1; /* force panic */
135 static struct sysrq_key_op sysrq_crash_op = {
136 .handler = sysrq_handle_crash,
138 .action_msg = "Trigger a crash",
139 .enable_mask = SYSRQ_ENABLE_DUMP,
142 static void sysrq_handle_reboot(int key)
148 static struct sysrq_key_op sysrq_reboot_op = {
149 .handler = sysrq_handle_reboot,
150 .help_msg = "reBoot",
151 .action_msg = "Resetting",
152 .enable_mask = SYSRQ_ENABLE_BOOT,
155 static void sysrq_handle_sync(int key)
159 static struct sysrq_key_op sysrq_sync_op = {
160 .handler = sysrq_handle_sync,
162 .action_msg = "Emergency Sync",
163 .enable_mask = SYSRQ_ENABLE_SYNC,
166 static void sysrq_handle_show_timers(int key)
168 sysrq_timer_list_show();
171 static struct sysrq_key_op sysrq_show_timers_op = {
172 .handler = sysrq_handle_show_timers,
173 .help_msg = "show-all-timers(Q)",
174 .action_msg = "Show clockevent devices & pending hrtimers (no others)",
177 static void sysrq_handle_mountro(int key)
181 static struct sysrq_key_op sysrq_mountro_op = {
182 .handler = sysrq_handle_mountro,
183 .help_msg = "Unmount",
184 .action_msg = "Emergency Remount R/O",
185 .enable_mask = SYSRQ_ENABLE_REMOUNT,
188 #ifdef CONFIG_LOCKDEP
189 static void sysrq_handle_showlocks(int key)
191 debug_show_all_locks();
194 static struct sysrq_key_op sysrq_showlocks_op = {
195 .handler = sysrq_handle_showlocks,
196 .help_msg = "show-all-locks(D)",
197 .action_msg = "Show Locks Held",
200 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
204 static DEFINE_SPINLOCK(show_lock);
206 static void showacpu(void *dummy)
210 /* Idle CPUs have no interesting backtrace. */
211 if (idle_cpu(smp_processor_id()))
214 spin_lock_irqsave(&show_lock, flags);
215 printk(KERN_INFO "CPU%d:\n", smp_processor_id());
216 show_stack(NULL, NULL);
217 spin_unlock_irqrestore(&show_lock, flags);
220 static void sysrq_showregs_othercpus(struct work_struct *dummy)
222 smp_call_function(showacpu, NULL, 0);
225 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
227 static void sysrq_handle_showallcpus(int key)
230 * Fall back to the workqueue based printing if the
231 * backtrace printing did not succeed or the
232 * architecture has no support for it:
234 if (!trigger_all_cpu_backtrace()) {
235 struct pt_regs *regs = get_irq_regs();
238 printk(KERN_INFO "CPU%d:\n", smp_processor_id());
241 schedule_work(&sysrq_showallcpus);
245 static struct sysrq_key_op sysrq_showallcpus_op = {
246 .handler = sysrq_handle_showallcpus,
247 .help_msg = "show-backtrace-all-active-cpus(L)",
248 .action_msg = "Show backtrace of all active CPUs",
249 .enable_mask = SYSRQ_ENABLE_DUMP,
253 static void sysrq_handle_showregs(int key)
255 struct pt_regs *regs = get_irq_regs();
258 perf_event_print_debug();
260 static struct sysrq_key_op sysrq_showregs_op = {
261 .handler = sysrq_handle_showregs,
262 .help_msg = "show-registers(P)",
263 .action_msg = "Show Regs",
264 .enable_mask = SYSRQ_ENABLE_DUMP,
267 static void sysrq_handle_showstate(int key)
271 static struct sysrq_key_op sysrq_showstate_op = {
272 .handler = sysrq_handle_showstate,
273 .help_msg = "show-task-states(T)",
274 .action_msg = "Show State",
275 .enable_mask = SYSRQ_ENABLE_DUMP,
278 static void sysrq_handle_showstate_blocked(int key)
280 show_state_filter(TASK_UNINTERRUPTIBLE);
282 static struct sysrq_key_op sysrq_showstate_blocked_op = {
283 .handler = sysrq_handle_showstate_blocked,
284 .help_msg = "show-blocked-tasks(W)",
285 .action_msg = "Show Blocked State",
286 .enable_mask = SYSRQ_ENABLE_DUMP,
289 #ifdef CONFIG_TRACING
290 #include <linux/ftrace.h>
292 static void sysrq_ftrace_dump(int key)
294 ftrace_dump(DUMP_ALL);
296 static struct sysrq_key_op sysrq_ftrace_dump_op = {
297 .handler = sysrq_ftrace_dump,
298 .help_msg = "dump-ftrace-buffer(Z)",
299 .action_msg = "Dump ftrace buffer",
300 .enable_mask = SYSRQ_ENABLE_DUMP,
303 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
306 static void sysrq_handle_showmem(int key)
310 static struct sysrq_key_op sysrq_showmem_op = {
311 .handler = sysrq_handle_showmem,
312 .help_msg = "show-memory-usage(M)",
313 .action_msg = "Show Memory",
314 .enable_mask = SYSRQ_ENABLE_DUMP,
318 * Signal sysrq helper function. Sends a signal to all user processes.
320 static void send_sig_all(int sig)
322 struct task_struct *p;
324 read_lock(&tasklist_lock);
325 for_each_process(p) {
326 if (p->flags & PF_KTHREAD)
328 if (is_global_init(p))
331 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
333 read_unlock(&tasklist_lock);
336 static void sysrq_handle_term(int key)
338 send_sig_all(SIGTERM);
339 console_loglevel = 8;
341 static struct sysrq_key_op sysrq_term_op = {
342 .handler = sysrq_handle_term,
343 .help_msg = "terminate-all-tasks(E)",
344 .action_msg = "Terminate All Tasks",
345 .enable_mask = SYSRQ_ENABLE_SIGNAL,
348 static void moom_callback(struct work_struct *ignored)
350 out_of_memory(node_zonelist(first_online_node, GFP_KERNEL), GFP_KERNEL,
354 static DECLARE_WORK(moom_work, moom_callback);
356 static void sysrq_handle_moom(int key)
358 schedule_work(&moom_work);
360 static struct sysrq_key_op sysrq_moom_op = {
361 .handler = sysrq_handle_moom,
362 .help_msg = "memory-full-oom-kill(F)",
363 .action_msg = "Manual OOM execution",
364 .enable_mask = SYSRQ_ENABLE_SIGNAL,
368 static void sysrq_handle_thaw(int key)
370 emergency_thaw_all();
372 static struct sysrq_key_op sysrq_thaw_op = {
373 .handler = sysrq_handle_thaw,
374 .help_msg = "thaw-filesystems(J)",
375 .action_msg = "Emergency Thaw of all frozen filesystems",
376 .enable_mask = SYSRQ_ENABLE_SIGNAL,
380 static void sysrq_handle_kill(int key)
382 send_sig_all(SIGKILL);
383 console_loglevel = 8;
385 static struct sysrq_key_op sysrq_kill_op = {
386 .handler = sysrq_handle_kill,
387 .help_msg = "kill-all-tasks(I)",
388 .action_msg = "Kill All Tasks",
389 .enable_mask = SYSRQ_ENABLE_SIGNAL,
392 static void sysrq_handle_unrt(int key)
394 normalize_rt_tasks();
396 static struct sysrq_key_op sysrq_unrt_op = {
397 .handler = sysrq_handle_unrt,
398 .help_msg = "nice-all-RT-tasks(N)",
399 .action_msg = "Nice All RT Tasks",
400 .enable_mask = SYSRQ_ENABLE_RTNICE,
403 /* Key Operations table and lock */
404 static DEFINE_SPINLOCK(sysrq_key_table_lock);
406 static struct sysrq_key_op *sysrq_key_table[36] = {
407 &sysrq_loglevel_op, /* 0 */
408 &sysrq_loglevel_op, /* 1 */
409 &sysrq_loglevel_op, /* 2 */
410 &sysrq_loglevel_op, /* 3 */
411 &sysrq_loglevel_op, /* 4 */
412 &sysrq_loglevel_op, /* 5 */
413 &sysrq_loglevel_op, /* 6 */
414 &sysrq_loglevel_op, /* 7 */
415 &sysrq_loglevel_op, /* 8 */
416 &sysrq_loglevel_op, /* 9 */
419 * a: Don't use for system provided sysrqs, it is handled specially on
420 * sparc and will never arrive.
423 &sysrq_reboot_op, /* b */
424 &sysrq_crash_op, /* c & ibm_emac driver debug */
425 &sysrq_showlocks_op, /* d */
426 &sysrq_term_op, /* e */
427 &sysrq_moom_op, /* f */
428 /* g: May be registered for the kernel debugger */
430 NULL, /* h - reserved for help */
431 &sysrq_kill_op, /* i */
433 &sysrq_thaw_op, /* j */
437 &sysrq_SAK_op, /* k */
439 &sysrq_showallcpus_op, /* l */
443 &sysrq_showmem_op, /* m */
444 &sysrq_unrt_op, /* n */
445 /* o: This will often be registered as 'Off' at init time */
447 &sysrq_showregs_op, /* p */
448 &sysrq_show_timers_op, /* q */
449 &sysrq_unraw_op, /* r */
450 &sysrq_sync_op, /* s */
451 &sysrq_showstate_op, /* t */
452 &sysrq_mountro_op, /* u */
453 /* v: May be registered for frame buffer console restore */
455 &sysrq_showstate_blocked_op, /* w */
456 /* x: May be registered on ppc/powerpc for xmon */
457 /* x: May be registered on sparc64 for global PMU dump */
459 /* y: May be registered on sparc64 for global register dump */
461 &sysrq_ftrace_dump_op, /* z */
464 /* key2index calculation, -1 on invalid index */
465 static int sysrq_key_table_key2index(int key)
469 if ((key >= '0') && (key <= '9'))
471 else if ((key >= 'a') && (key <= 'z'))
472 retval = key + 10 - 'a';
479 * get and put functions for the table, exposed to modules.
481 struct sysrq_key_op *__sysrq_get_key_op(int key)
483 struct sysrq_key_op *op_p = NULL;
486 i = sysrq_key_table_key2index(key);
488 op_p = sysrq_key_table[i];
493 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
495 int i = sysrq_key_table_key2index(key);
498 sysrq_key_table[i] = op_p;
501 void __handle_sysrq(int key, bool check_mask)
503 struct sysrq_key_op *op_p;
508 spin_lock_irqsave(&sysrq_key_table_lock, flags);
510 * Raise the apparent loglevel to maximum so that the sysrq header
511 * is shown to provide the user with positive feedback. We do not
512 * simply emit this at KERN_EMERG as that would change message
513 * routing in the consumers of /proc/kmsg.
515 orig_log_level = console_loglevel;
516 console_loglevel = 7;
517 printk(KERN_INFO "SysRq : ");
519 op_p = __sysrq_get_key_op(key);
522 * Should we check for enabled operations (/proc/sysrq-trigger
523 * should not) and is the invoked operation enabled?
525 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
526 printk("%s\n", op_p->action_msg);
527 console_loglevel = orig_log_level;
530 printk("This sysrq operation is disabled.\n");
534 /* Only print the help msg once per handler */
535 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
536 if (sysrq_key_table[i]) {
539 for (j = 0; sysrq_key_table[i] !=
540 sysrq_key_table[j]; j++)
544 printk("%s ", sysrq_key_table[i]->help_msg);
548 console_loglevel = orig_log_level;
550 spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
553 void handle_sysrq(int key)
556 __handle_sysrq(key, true);
558 EXPORT_SYMBOL(handle_sysrq);
562 /* Simple translation table for the SysRq keys */
563 static const unsigned char sysrq_xlate[KEY_CNT] =
564 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
565 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
566 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
567 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
568 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
569 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
570 "\r\000/"; /* 0x60 - 0x6f */
573 struct input_handle handle;
574 struct work_struct reinject_work;
575 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
577 unsigned int alt_use;
583 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
585 struct sysrq_state *sysrq =
586 container_of(work, struct sysrq_state, reinject_work);
587 struct input_handle *handle = &sysrq->handle;
588 unsigned int alt_code = sysrq->alt_use;
590 if (sysrq->need_reinject) {
591 /* we do not want the assignment to be reordered */
592 sysrq->reinjecting = true;
595 /* Simulate press and release of Alt + SysRq */
596 input_inject_event(handle, EV_KEY, alt_code, 1);
597 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
598 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
600 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
601 input_inject_event(handle, EV_KEY, alt_code, 0);
602 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
605 sysrq->reinjecting = false;
609 static bool sysrq_filter(struct input_handle *handle,
610 unsigned int type, unsigned int code, int value)
612 struct sysrq_state *sysrq = handle->private;
613 bool was_active = sysrq->active;
617 * Do not filter anything if we are in the process of re-injecting
618 * Alt+SysRq combination.
620 if (sysrq->reinjecting)
635 /* One of ALTs is being released */
636 if (sysrq->active && code == sysrq->alt_use)
637 sysrq->active = false;
639 sysrq->alt = KEY_RESERVED;
641 } else if (value != 2) {
643 sysrq->need_reinject = false;
648 if (value == 1 && sysrq->alt != KEY_RESERVED) {
649 sysrq->active = true;
650 sysrq->alt_use = sysrq->alt;
652 * If nothing else will be pressed we'll need
653 * to re-inject Alt-SysRq keysroke.
655 sysrq->need_reinject = true;
659 * Pretend that sysrq was never pressed at all. This
660 * is needed to properly handle KGDB which will try
661 * to release all keys after exiting debugger. If we
662 * do not clear key bit it KGDB will end up sending
663 * release events for Alt and SysRq, potentially
664 * triggering print screen function.
667 clear_bit(KEY_SYSRQ, handle->dev->key);
672 if (sysrq->active && value && value != 2) {
673 sysrq->need_reinject = false;
674 __handle_sysrq(sysrq_xlate[code], true);
679 suppress = sysrq->active;
681 if (!sysrq->active) {
683 * If we are not suppressing key presses keep track of
684 * keyboard state so we can release keys that have been
685 * pressed before entering SysRq mode.
688 set_bit(code, sysrq->key_down);
690 clear_bit(code, sysrq->key_down);
693 schedule_work(&sysrq->reinject_work);
695 } else if (value == 0 &&
696 test_and_clear_bit(code, sysrq->key_down)) {
698 * Pass on release events for keys that was pressed before
699 * entering SysRq mode.
706 suppress = sysrq->active;
713 static int sysrq_connect(struct input_handler *handler,
714 struct input_dev *dev,
715 const struct input_device_id *id)
717 struct sysrq_state *sysrq;
720 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
724 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
726 sysrq->handle.dev = dev;
727 sysrq->handle.handler = handler;
728 sysrq->handle.name = "sysrq";
729 sysrq->handle.private = sysrq;
731 error = input_register_handle(&sysrq->handle);
733 pr_err("Failed to register input sysrq handler, error %d\n",
738 error = input_open_device(&sysrq->handle);
740 pr_err("Failed to open input device, error %d\n", error);
747 input_unregister_handle(&sysrq->handle);
753 static void sysrq_disconnect(struct input_handle *handle)
755 struct sysrq_state *sysrq = handle->private;
757 input_close_device(handle);
758 cancel_work_sync(&sysrq->reinject_work);
759 input_unregister_handle(handle);
764 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
765 * keyboards have SysRq key predefined and so user may add it to keymap
766 * later, but we expect all such keyboards to have left alt.
768 static const struct input_device_id sysrq_ids[] = {
770 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
771 INPUT_DEVICE_ID_MATCH_KEYBIT,
772 .evbit = { BIT_MASK(EV_KEY) },
773 .keybit = { BIT_MASK(KEY_LEFTALT) },
778 static struct input_handler sysrq_handler = {
779 .filter = sysrq_filter,
780 .connect = sysrq_connect,
781 .disconnect = sysrq_disconnect,
783 .id_table = sysrq_ids,
786 static bool sysrq_handler_registered;
788 static inline void sysrq_register_handler(void)
792 error = input_register_handler(&sysrq_handler);
794 pr_err("Failed to register input handler, error %d", error);
796 sysrq_handler_registered = true;
799 static inline void sysrq_unregister_handler(void)
801 if (sysrq_handler_registered) {
802 input_unregister_handler(&sysrq_handler);
803 sysrq_handler_registered = false;
809 static inline void sysrq_register_handler(void)
813 static inline void sysrq_unregister_handler(void)
817 #endif /* CONFIG_INPUT */
819 int sysrq_toggle_support(int enable_mask)
821 bool was_enabled = sysrq_on();
823 sysrq_enabled = enable_mask;
825 if (was_enabled != sysrq_on()) {
827 sysrq_register_handler();
829 sysrq_unregister_handler();
835 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
836 struct sysrq_key_op *remove_op_p)
841 spin_lock_irqsave(&sysrq_key_table_lock, flags);
842 if (__sysrq_get_key_op(key) == remove_op_p) {
843 __sysrq_put_key_op(key, insert_op_p);
848 spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
852 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
854 return __sysrq_swap_key_ops(key, op_p, NULL);
856 EXPORT_SYMBOL(register_sysrq_key);
858 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
860 return __sysrq_swap_key_ops(key, NULL, op_p);
862 EXPORT_SYMBOL(unregister_sysrq_key);
864 #ifdef CONFIG_PROC_FS
866 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
868 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
869 size_t count, loff_t *ppos)
874 if (get_user(c, buf))
876 __handle_sysrq(c, false);
882 static const struct file_operations proc_sysrq_trigger_operations = {
883 .write = write_sysrq_trigger,
884 .llseek = noop_llseek,
887 static void sysrq_init_procfs(void)
889 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
890 &proc_sysrq_trigger_operations))
891 pr_err("Failed to register proc interface\n");
896 static inline void sysrq_init_procfs(void)
900 #endif /* CONFIG_PROC_FS */
902 static int __init sysrq_init(void)
907 sysrq_register_handler();
911 module_init(sysrq_init);