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>
45 #include <linux/moduleparam.h>
47 #include <asm/ptrace.h>
48 #include <asm/irq_regs.h>
50 /* Whether we react on sysrq keys or just ignore them */
51 static int __read_mostly sysrq_enabled = SYSRQ_DEFAULT_ENABLE;
52 static bool __read_mostly sysrq_always_enabled;
54 static bool sysrq_on(void)
56 return sysrq_enabled || sysrq_always_enabled;
60 * A value of 1 means 'all', other nonzero values are an op mask:
62 static bool sysrq_on_mask(int mask)
64 return sysrq_always_enabled ||
66 (sysrq_enabled & mask);
69 static int __init sysrq_always_enabled_setup(char *str)
71 sysrq_always_enabled = true;
72 pr_info("sysrq always enabled.\n");
77 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
80 static void sysrq_handle_loglevel(int key)
86 printk("Loglevel set to %d\n", i);
89 static struct sysrq_key_op sysrq_loglevel_op = {
90 .handler = sysrq_handle_loglevel,
91 .help_msg = "loglevel(0-9)",
92 .action_msg = "Changing Loglevel",
93 .enable_mask = SYSRQ_ENABLE_LOG,
97 static void sysrq_handle_SAK(int key)
99 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
100 schedule_work(SAK_work);
102 static struct sysrq_key_op sysrq_SAK_op = {
103 .handler = sysrq_handle_SAK,
106 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
109 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
113 static void sysrq_handle_unraw(int key)
115 vt_reset_unicode(fg_console);
118 static struct sysrq_key_op sysrq_unraw_op = {
119 .handler = sysrq_handle_unraw,
121 .action_msg = "Keyboard mode set to system default",
122 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
125 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
126 #endif /* CONFIG_VT */
128 static void sysrq_handle_crash(int key)
132 panic_on_oops = 1; /* force panic */
136 static struct sysrq_key_op sysrq_crash_op = {
137 .handler = sysrq_handle_crash,
139 .action_msg = "Trigger a crash",
140 .enable_mask = SYSRQ_ENABLE_DUMP,
143 static void sysrq_handle_reboot(int key)
149 static struct sysrq_key_op sysrq_reboot_op = {
150 .handler = sysrq_handle_reboot,
151 .help_msg = "reBoot",
152 .action_msg = "Resetting",
153 .enable_mask = SYSRQ_ENABLE_BOOT,
156 static void sysrq_handle_sync(int key)
160 static struct sysrq_key_op sysrq_sync_op = {
161 .handler = sysrq_handle_sync,
163 .action_msg = "Emergency Sync",
164 .enable_mask = SYSRQ_ENABLE_SYNC,
167 static void sysrq_handle_show_timers(int key)
169 sysrq_timer_list_show();
172 static struct sysrq_key_op sysrq_show_timers_op = {
173 .handler = sysrq_handle_show_timers,
174 .help_msg = "show-all-timers(Q)",
175 .action_msg = "Show clockevent devices & pending hrtimers (no others)",
178 static void sysrq_handle_mountro(int key)
182 static struct sysrq_key_op sysrq_mountro_op = {
183 .handler = sysrq_handle_mountro,
184 .help_msg = "Unmount",
185 .action_msg = "Emergency Remount R/O",
186 .enable_mask = SYSRQ_ENABLE_REMOUNT,
189 #ifdef CONFIG_LOCKDEP
190 static void sysrq_handle_showlocks(int key)
192 debug_show_all_locks();
195 static struct sysrq_key_op sysrq_showlocks_op = {
196 .handler = sysrq_handle_showlocks,
197 .help_msg = "show-all-locks(D)",
198 .action_msg = "Show Locks Held",
201 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
205 static DEFINE_SPINLOCK(show_lock);
207 static void showacpu(void *dummy)
211 /* Idle CPUs have no interesting backtrace. */
212 if (idle_cpu(smp_processor_id()))
215 spin_lock_irqsave(&show_lock, flags);
216 printk(KERN_INFO "CPU%d:\n", smp_processor_id());
217 show_stack(NULL, NULL);
218 spin_unlock_irqrestore(&show_lock, flags);
221 static void sysrq_showregs_othercpus(struct work_struct *dummy)
223 smp_call_function(showacpu, NULL, 0);
226 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
228 static void sysrq_handle_showallcpus(int key)
231 * Fall back to the workqueue based printing if the
232 * backtrace printing did not succeed or the
233 * architecture has no support for it:
235 if (!trigger_all_cpu_backtrace()) {
236 struct pt_regs *regs = get_irq_regs();
239 printk(KERN_INFO "CPU%d:\n", smp_processor_id());
242 schedule_work(&sysrq_showallcpus);
246 static struct sysrq_key_op sysrq_showallcpus_op = {
247 .handler = sysrq_handle_showallcpus,
248 .help_msg = "show-backtrace-all-active-cpus(L)",
249 .action_msg = "Show backtrace of all active CPUs",
250 .enable_mask = SYSRQ_ENABLE_DUMP,
254 static void sysrq_handle_showregs(int key)
256 struct pt_regs *regs = get_irq_regs();
259 perf_event_print_debug();
261 static struct sysrq_key_op sysrq_showregs_op = {
262 .handler = sysrq_handle_showregs,
263 .help_msg = "show-registers(P)",
264 .action_msg = "Show Regs",
265 .enable_mask = SYSRQ_ENABLE_DUMP,
268 static void sysrq_handle_showstate(int key)
272 static struct sysrq_key_op sysrq_showstate_op = {
273 .handler = sysrq_handle_showstate,
274 .help_msg = "show-task-states(T)",
275 .action_msg = "Show State",
276 .enable_mask = SYSRQ_ENABLE_DUMP,
279 static void sysrq_handle_showstate_blocked(int key)
281 show_state_filter(TASK_UNINTERRUPTIBLE);
283 static struct sysrq_key_op sysrq_showstate_blocked_op = {
284 .handler = sysrq_handle_showstate_blocked,
285 .help_msg = "show-blocked-tasks(W)",
286 .action_msg = "Show Blocked State",
287 .enable_mask = SYSRQ_ENABLE_DUMP,
290 #ifdef CONFIG_TRACING
291 #include <linux/ftrace.h>
293 static void sysrq_ftrace_dump(int key)
295 ftrace_dump(DUMP_ALL);
297 static struct sysrq_key_op sysrq_ftrace_dump_op = {
298 .handler = sysrq_ftrace_dump,
299 .help_msg = "dump-ftrace-buffer(Z)",
300 .action_msg = "Dump ftrace buffer",
301 .enable_mask = SYSRQ_ENABLE_DUMP,
304 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
307 static void sysrq_handle_showmem(int key)
311 static struct sysrq_key_op sysrq_showmem_op = {
312 .handler = sysrq_handle_showmem,
313 .help_msg = "show-memory-usage(M)",
314 .action_msg = "Show Memory",
315 .enable_mask = SYSRQ_ENABLE_DUMP,
319 * Signal sysrq helper function. Sends a signal to all user processes.
321 static void send_sig_all(int sig)
323 struct task_struct *p;
325 read_lock(&tasklist_lock);
326 for_each_process(p) {
327 if (p->flags & PF_KTHREAD)
329 if (is_global_init(p))
332 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
334 read_unlock(&tasklist_lock);
337 static void sysrq_handle_term(int key)
339 send_sig_all(SIGTERM);
340 console_loglevel = 8;
342 static struct sysrq_key_op sysrq_term_op = {
343 .handler = sysrq_handle_term,
344 .help_msg = "terminate-all-tasks(E)",
345 .action_msg = "Terminate All Tasks",
346 .enable_mask = SYSRQ_ENABLE_SIGNAL,
349 static void moom_callback(struct work_struct *ignored)
351 out_of_memory(node_zonelist(first_online_node, GFP_KERNEL), GFP_KERNEL,
355 static DECLARE_WORK(moom_work, moom_callback);
357 static void sysrq_handle_moom(int key)
359 schedule_work(&moom_work);
361 static struct sysrq_key_op sysrq_moom_op = {
362 .handler = sysrq_handle_moom,
363 .help_msg = "memory-full-oom-kill(F)",
364 .action_msg = "Manual OOM execution",
365 .enable_mask = SYSRQ_ENABLE_SIGNAL,
369 static void sysrq_handle_thaw(int key)
371 emergency_thaw_all();
373 static struct sysrq_key_op sysrq_thaw_op = {
374 .handler = sysrq_handle_thaw,
375 .help_msg = "thaw-filesystems(J)",
376 .action_msg = "Emergency Thaw of all frozen filesystems",
377 .enable_mask = SYSRQ_ENABLE_SIGNAL,
381 static void sysrq_handle_kill(int key)
383 send_sig_all(SIGKILL);
384 console_loglevel = 8;
386 static struct sysrq_key_op sysrq_kill_op = {
387 .handler = sysrq_handle_kill,
388 .help_msg = "kill-all-tasks(I)",
389 .action_msg = "Kill All Tasks",
390 .enable_mask = SYSRQ_ENABLE_SIGNAL,
393 static void sysrq_handle_unrt(int key)
395 normalize_rt_tasks();
397 static struct sysrq_key_op sysrq_unrt_op = {
398 .handler = sysrq_handle_unrt,
399 .help_msg = "nice-all-RT-tasks(N)",
400 .action_msg = "Nice All RT Tasks",
401 .enable_mask = SYSRQ_ENABLE_RTNICE,
404 /* Key Operations table and lock */
405 static DEFINE_SPINLOCK(sysrq_key_table_lock);
407 static struct sysrq_key_op *sysrq_key_table[36] = {
408 &sysrq_loglevel_op, /* 0 */
409 &sysrq_loglevel_op, /* 1 */
410 &sysrq_loglevel_op, /* 2 */
411 &sysrq_loglevel_op, /* 3 */
412 &sysrq_loglevel_op, /* 4 */
413 &sysrq_loglevel_op, /* 5 */
414 &sysrq_loglevel_op, /* 6 */
415 &sysrq_loglevel_op, /* 7 */
416 &sysrq_loglevel_op, /* 8 */
417 &sysrq_loglevel_op, /* 9 */
420 * a: Don't use for system provided sysrqs, it is handled specially on
421 * sparc and will never arrive.
424 &sysrq_reboot_op, /* b */
425 &sysrq_crash_op, /* c & ibm_emac driver debug */
426 &sysrq_showlocks_op, /* d */
427 &sysrq_term_op, /* e */
428 &sysrq_moom_op, /* f */
429 /* g: May be registered for the kernel debugger */
431 NULL, /* h - reserved for help */
432 &sysrq_kill_op, /* i */
434 &sysrq_thaw_op, /* j */
438 &sysrq_SAK_op, /* k */
440 &sysrq_showallcpus_op, /* l */
444 &sysrq_showmem_op, /* m */
445 &sysrq_unrt_op, /* n */
446 /* o: This will often be registered as 'Off' at init time */
448 &sysrq_showregs_op, /* p */
449 &sysrq_show_timers_op, /* q */
450 &sysrq_unraw_op, /* r */
451 &sysrq_sync_op, /* s */
452 &sysrq_showstate_op, /* t */
453 &sysrq_mountro_op, /* u */
454 /* v: May be registered for frame buffer console restore */
456 &sysrq_showstate_blocked_op, /* w */
457 /* x: May be registered on ppc/powerpc for xmon */
458 /* x: May be registered on sparc64 for global PMU dump */
460 /* y: May be registered on sparc64 for global register dump */
462 &sysrq_ftrace_dump_op, /* z */
465 /* key2index calculation, -1 on invalid index */
466 static int sysrq_key_table_key2index(int key)
470 if ((key >= '0') && (key <= '9'))
472 else if ((key >= 'a') && (key <= 'z'))
473 retval = key + 10 - 'a';
480 * get and put functions for the table, exposed to modules.
482 struct sysrq_key_op *__sysrq_get_key_op(int key)
484 struct sysrq_key_op *op_p = NULL;
487 i = sysrq_key_table_key2index(key);
489 op_p = sysrq_key_table[i];
494 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
496 int i = sysrq_key_table_key2index(key);
499 sysrq_key_table[i] = op_p;
502 void __handle_sysrq(int key, bool check_mask)
504 struct sysrq_key_op *op_p;
509 spin_lock_irqsave(&sysrq_key_table_lock, flags);
511 * Raise the apparent loglevel to maximum so that the sysrq header
512 * is shown to provide the user with positive feedback. We do not
513 * simply emit this at KERN_EMERG as that would change message
514 * routing in the consumers of /proc/kmsg.
516 orig_log_level = console_loglevel;
517 console_loglevel = 7;
518 printk(KERN_INFO "SysRq : ");
520 op_p = __sysrq_get_key_op(key);
523 * Should we check for enabled operations (/proc/sysrq-trigger
524 * should not) and is the invoked operation enabled?
526 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
527 printk("%s\n", op_p->action_msg);
528 console_loglevel = orig_log_level;
531 printk("This sysrq operation is disabled.\n");
535 /* Only print the help msg once per handler */
536 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
537 if (sysrq_key_table[i]) {
540 for (j = 0; sysrq_key_table[i] !=
541 sysrq_key_table[j]; j++)
545 printk("%s ", sysrq_key_table[i]->help_msg);
549 console_loglevel = orig_log_level;
551 spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
554 void handle_sysrq(int key)
557 __handle_sysrq(key, true);
559 EXPORT_SYMBOL(handle_sysrq);
563 /* Simple translation table for the SysRq keys */
564 static const unsigned char sysrq_xlate[KEY_CNT] =
565 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
566 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
567 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
568 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
569 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
570 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
571 "\r\000/"; /* 0x60 - 0x6f */
574 struct input_handle handle;
575 struct work_struct reinject_work;
576 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
578 unsigned int alt_use;
583 /* reset sequence handling */
585 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
588 int reset_seq_version;
591 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
592 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
593 static unsigned int sysrq_reset_seq_len;
594 static unsigned int sysrq_reset_seq_version = 1;
596 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
601 state->reset_seq_cnt = 0;
603 for (i = 0; i < sysrq_reset_seq_len; i++) {
604 key = sysrq_reset_seq[i];
606 if (key == KEY_RESERVED || key > KEY_MAX)
609 __set_bit(key, state->reset_keybit);
610 state->reset_seq_len++;
612 if (test_bit(key, state->key_down))
613 state->reset_seq_cnt++;
616 /* Disable reset until old keys are not released */
617 state->reset_canceled = state->reset_seq_cnt != 0;
619 state->reset_seq_version = sysrq_reset_seq_version;
622 static bool sysrq_detect_reset_sequence(struct sysrq_state *state,
623 unsigned int code, int value)
625 if (!test_bit(code, state->reset_keybit)) {
627 * Pressing any key _not_ in reset sequence cancels
628 * the reset sequence.
630 if (value && state->reset_seq_cnt)
631 state->reset_canceled = true;
632 } else if (value == 0) {
634 if (--state->reset_seq_cnt == 0)
635 state->reset_canceled = false;
636 } else if (value == 1) {
637 /* key press, not autorepeat */
638 if (++state->reset_seq_cnt == state->reset_seq_len &&
639 !state->reset_canceled) {
647 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
649 struct sysrq_state *sysrq =
650 container_of(work, struct sysrq_state, reinject_work);
651 struct input_handle *handle = &sysrq->handle;
652 unsigned int alt_code = sysrq->alt_use;
654 if (sysrq->need_reinject) {
655 /* we do not want the assignment to be reordered */
656 sysrq->reinjecting = true;
659 /* Simulate press and release of Alt + SysRq */
660 input_inject_event(handle, EV_KEY, alt_code, 1);
661 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
662 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
664 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
665 input_inject_event(handle, EV_KEY, alt_code, 0);
666 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
669 sysrq->reinjecting = false;
673 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
674 unsigned int code, int value)
676 bool was_active = sysrq->active;
684 /* One of ALTs is being released */
685 if (sysrq->active && code == sysrq->alt_use)
686 sysrq->active = false;
688 sysrq->alt = KEY_RESERVED;
690 } else if (value != 2) {
692 sysrq->need_reinject = false;
697 if (value == 1 && sysrq->alt != KEY_RESERVED) {
698 sysrq->active = true;
699 sysrq->alt_use = sysrq->alt;
701 * If nothing else will be pressed we'll need
702 * to re-inject Alt-SysRq keysroke.
704 sysrq->need_reinject = true;
708 * Pretend that sysrq was never pressed at all. This
709 * is needed to properly handle KGDB which will try
710 * to release all keys after exiting debugger. If we
711 * do not clear key bit it KGDB will end up sending
712 * release events for Alt and SysRq, potentially
713 * triggering print screen function.
716 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
721 if (sysrq->active && value && value != 2) {
722 sysrq->need_reinject = false;
723 __handle_sysrq(sysrq_xlate[code], true);
728 suppress = sysrq->active;
730 if (!sysrq->active) {
733 * See if reset sequence has changed since the last time.
735 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
736 sysrq_parse_reset_sequence(sysrq);
739 * If we are not suppressing key presses keep track of
740 * keyboard state so we can release keys that have been
741 * pressed before entering SysRq mode.
744 set_bit(code, sysrq->key_down);
746 clear_bit(code, sysrq->key_down);
749 schedule_work(&sysrq->reinject_work);
751 if (sysrq_detect_reset_sequence(sysrq, code, value)) {
752 /* Force emergency reboot */
753 __handle_sysrq(sysrq_xlate[KEY_B], false);
756 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
758 * Pass on release events for keys that was pressed before
759 * entering SysRq mode.
767 static bool sysrq_filter(struct input_handle *handle,
768 unsigned int type, unsigned int code, int value)
770 struct sysrq_state *sysrq = handle->private;
774 * Do not filter anything if we are in the process of re-injecting
775 * Alt+SysRq combination.
777 if (sysrq->reinjecting)
787 suppress = sysrq_handle_keypress(sysrq, code, value);
791 suppress = sysrq->active;
798 static int sysrq_connect(struct input_handler *handler,
799 struct input_dev *dev,
800 const struct input_device_id *id)
802 struct sysrq_state *sysrq;
805 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
809 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
811 sysrq->handle.dev = dev;
812 sysrq->handle.handler = handler;
813 sysrq->handle.name = "sysrq";
814 sysrq->handle.private = sysrq;
816 error = input_register_handle(&sysrq->handle);
818 pr_err("Failed to register input sysrq handler, error %d\n",
823 error = input_open_device(&sysrq->handle);
825 pr_err("Failed to open input device, error %d\n", error);
832 input_unregister_handle(&sysrq->handle);
838 static void sysrq_disconnect(struct input_handle *handle)
840 struct sysrq_state *sysrq = handle->private;
842 input_close_device(handle);
843 cancel_work_sync(&sysrq->reinject_work);
844 input_unregister_handle(handle);
849 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
850 * keyboards have SysRq key predefined and so user may add it to keymap
851 * later, but we expect all such keyboards to have left alt.
853 static const struct input_device_id sysrq_ids[] = {
855 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
856 INPUT_DEVICE_ID_MATCH_KEYBIT,
857 .evbit = { BIT_MASK(EV_KEY) },
858 .keybit = { BIT_MASK(KEY_LEFTALT) },
863 static struct input_handler sysrq_handler = {
864 .filter = sysrq_filter,
865 .connect = sysrq_connect,
866 .disconnect = sysrq_disconnect,
868 .id_table = sysrq_ids,
871 static bool sysrq_handler_registered;
873 static inline void sysrq_register_handler(void)
875 extern unsigned short platform_sysrq_reset_seq[] __weak;
880 if (platform_sysrq_reset_seq) {
881 for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
882 key = platform_sysrq_reset_seq[i];
883 if (key == KEY_RESERVED || key > KEY_MAX)
886 sysrq_reset_seq[sysrq_reset_seq_len++] = key;
890 error = input_register_handler(&sysrq_handler);
892 pr_err("Failed to register input handler, error %d", error);
894 sysrq_handler_registered = true;
897 static inline void sysrq_unregister_handler(void)
899 if (sysrq_handler_registered) {
900 input_unregister_handler(&sysrq_handler);
901 sysrq_handler_registered = false;
905 static int sysrq_reset_seq_param_set(const char *buffer,
906 const struct kernel_param *kp)
911 error = strict_strtoul(buffer, 0, &val);
918 *((unsigned short *)kp->arg) = val;
919 sysrq_reset_seq_version++;
924 static struct kernel_param_ops param_ops_sysrq_reset_seq = {
925 .get = param_get_ushort,
926 .set = sysrq_reset_seq_param_set,
929 #define param_check_sysrq_reset_seq(name, p) \
930 __param_check(name, p, unsigned short)
932 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
933 &sysrq_reset_seq_len, 0644);
937 static inline void sysrq_register_handler(void)
941 static inline void sysrq_unregister_handler(void)
945 #endif /* CONFIG_INPUT */
947 int sysrq_toggle_support(int enable_mask)
949 bool was_enabled = sysrq_on();
951 sysrq_enabled = enable_mask;
953 if (was_enabled != sysrq_on()) {
955 sysrq_register_handler();
957 sysrq_unregister_handler();
963 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
964 struct sysrq_key_op *remove_op_p)
969 spin_lock_irqsave(&sysrq_key_table_lock, flags);
970 if (__sysrq_get_key_op(key) == remove_op_p) {
971 __sysrq_put_key_op(key, insert_op_p);
976 spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
980 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
982 return __sysrq_swap_key_ops(key, op_p, NULL);
984 EXPORT_SYMBOL(register_sysrq_key);
986 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
988 return __sysrq_swap_key_ops(key, NULL, op_p);
990 EXPORT_SYMBOL(unregister_sysrq_key);
992 #ifdef CONFIG_PROC_FS
994 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
996 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
997 size_t count, loff_t *ppos)
1002 if (get_user(c, buf))
1004 __handle_sysrq(c, false);
1010 static const struct file_operations proc_sysrq_trigger_operations = {
1011 .write = write_sysrq_trigger,
1012 .llseek = noop_llseek,
1015 static void sysrq_init_procfs(void)
1017 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1018 &proc_sysrq_trigger_operations))
1019 pr_err("Failed to register proc interface\n");
1024 static inline void sysrq_init_procfs(void)
1028 #endif /* CONFIG_PROC_FS */
1030 static int __init sysrq_init(void)
1032 sysrq_init_procfs();
1035 sysrq_register_handler();
1039 module_init(sysrq_init);