1 // SPDX-License-Identifier: GPL-2.0
3 * Linux Magic System Request Key Hacks
5 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
6 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
8 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
9 * overhauled to use key registration
10 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies
12 * Copyright (c) 2010 Dmitry Torokhov
13 * Input handler conversion
16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18 #include <linux/sched/signal.h>
19 #include <linux/sched/rt.h>
20 #include <linux/sched/debug.h>
21 #include <linux/sched/task.h>
22 #include <linux/ctype.h>
23 #include <linux/interrupt.h>
26 #include <linux/mount.h>
27 #include <linux/kdev_t.h>
28 #include <linux/major.h>
29 #include <linux/reboot.h>
30 #include <linux/sysrq.h>
31 #include <linux/kbd_kern.h>
32 #include <linux/proc_fs.h>
33 #include <linux/nmi.h>
34 #include <linux/quotaops.h>
35 #include <linux/perf_event.h>
36 #include <linux/kernel.h>
37 #include <linux/module.h>
38 #include <linux/suspend.h>
39 #include <linux/writeback.h>
40 #include <linux/swap.h>
41 #include <linux/spinlock.h>
42 #include <linux/vt_kern.h>
43 #include <linux/workqueue.h>
44 #include <linux/hrtimer.h>
45 #include <linux/oom.h>
46 #include <linux/slab.h>
47 #include <linux/input.h>
48 #include <linux/uaccess.h>
49 #include <linux/moduleparam.h>
50 #include <linux/jiffies.h>
51 #include <linux/syscalls.h>
53 #include <linux/rcupdate.h>
55 #include <asm/ptrace.h>
56 #include <asm/irq_regs.h>
58 /* Whether we react on sysrq keys or just ignore them */
59 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
60 static bool __read_mostly sysrq_always_enabled;
62 static bool sysrq_on(void)
64 return sysrq_enabled || sysrq_always_enabled;
68 * sysrq_mask - Getter for sysrq_enabled mask.
70 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
74 if (sysrq_always_enabled)
78 EXPORT_SYMBOL_GPL(sysrq_mask);
81 * A value of 1 means 'all', other nonzero values are an op mask:
83 static bool sysrq_on_mask(int mask)
85 return sysrq_always_enabled ||
87 (sysrq_enabled & mask);
90 static int __init sysrq_always_enabled_setup(char *str)
92 sysrq_always_enabled = true;
93 pr_info("sysrq always enabled.\n");
98 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
101 static void sysrq_handle_loglevel(int key)
106 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
107 pr_info("Loglevel set to %d\n", i);
108 console_loglevel = i;
110 static const struct sysrq_key_op sysrq_loglevel_op = {
111 .handler = sysrq_handle_loglevel,
112 .help_msg = "loglevel(0-9)",
113 .action_msg = "Changing Loglevel",
114 .enable_mask = SYSRQ_ENABLE_LOG,
118 static void sysrq_handle_SAK(int key)
120 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
122 schedule_work(SAK_work);
124 static const struct sysrq_key_op sysrq_SAK_op = {
125 .handler = sysrq_handle_SAK,
126 .help_msg = "sak(k)",
128 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
131 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
135 static void sysrq_handle_unraw(int key)
137 vt_reset_unicode(fg_console);
140 static const struct sysrq_key_op sysrq_unraw_op = {
141 .handler = sysrq_handle_unraw,
142 .help_msg = "unraw(r)",
143 .action_msg = "Keyboard mode set to system default",
144 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
147 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
148 #endif /* CONFIG_VT */
150 static void sysrq_handle_crash(int key)
152 /* release the RCU read lock before crashing */
155 panic("sysrq triggered crash\n");
157 static const struct sysrq_key_op sysrq_crash_op = {
158 .handler = sysrq_handle_crash,
159 .help_msg = "crash(c)",
160 .action_msg = "Trigger a crash",
161 .enable_mask = SYSRQ_ENABLE_DUMP,
164 static void sysrq_handle_reboot(int key)
170 static const struct sysrq_key_op sysrq_reboot_op = {
171 .handler = sysrq_handle_reboot,
172 .help_msg = "reboot(b)",
173 .action_msg = "Resetting",
174 .enable_mask = SYSRQ_ENABLE_BOOT,
177 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
179 static void sysrq_handle_sync(int key)
183 static const struct sysrq_key_op sysrq_sync_op = {
184 .handler = sysrq_handle_sync,
185 .help_msg = "sync(s)",
186 .action_msg = "Emergency Sync",
187 .enable_mask = SYSRQ_ENABLE_SYNC,
190 static void sysrq_handle_show_timers(int key)
192 sysrq_timer_list_show();
195 static const struct sysrq_key_op sysrq_show_timers_op = {
196 .handler = sysrq_handle_show_timers,
197 .help_msg = "show-all-timers(q)",
198 .action_msg = "Show clockevent devices & pending hrtimers (no others)",
201 static void sysrq_handle_mountro(int key)
205 static const struct sysrq_key_op sysrq_mountro_op = {
206 .handler = sysrq_handle_mountro,
207 .help_msg = "unmount(u)",
208 .action_msg = "Emergency Remount R/O",
209 .enable_mask = SYSRQ_ENABLE_REMOUNT,
212 #ifdef CONFIG_LOCKDEP
213 static void sysrq_handle_showlocks(int key)
215 debug_show_all_locks();
218 static const struct sysrq_key_op sysrq_showlocks_op = {
219 .handler = sysrq_handle_showlocks,
220 .help_msg = "show-all-locks(d)",
221 .action_msg = "Show Locks Held",
224 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
228 static DEFINE_RAW_SPINLOCK(show_lock);
230 static void showacpu(void *dummy)
234 /* Idle CPUs have no interesting backtrace. */
235 if (idle_cpu(smp_processor_id())) {
236 pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
240 raw_spin_lock_irqsave(&show_lock, flags);
241 pr_info("CPU%d:\n", smp_processor_id());
242 show_stack(NULL, NULL, KERN_INFO);
243 raw_spin_unlock_irqrestore(&show_lock, flags);
246 static void sysrq_showregs_othercpus(struct work_struct *dummy)
248 smp_call_function(showacpu, NULL, 0);
251 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
253 static void sysrq_handle_showallcpus(int key)
256 * Fall back to the workqueue based printing if the
257 * backtrace printing did not succeed or the
258 * architecture has no support for it:
260 if (!trigger_all_cpu_backtrace()) {
261 struct pt_regs *regs = NULL;
264 regs = get_irq_regs();
266 pr_info("CPU%d:\n", smp_processor_id());
270 show_stack(NULL, NULL, KERN_INFO);
272 schedule_work(&sysrq_showallcpus);
276 static const struct sysrq_key_op sysrq_showallcpus_op = {
277 .handler = sysrq_handle_showallcpus,
278 .help_msg = "show-backtrace-all-active-cpus(l)",
279 .action_msg = "Show backtrace of all active CPUs",
280 .enable_mask = SYSRQ_ENABLE_DUMP,
284 static void sysrq_handle_showregs(int key)
286 struct pt_regs *regs = NULL;
289 regs = get_irq_regs();
292 perf_event_print_debug();
294 static const struct sysrq_key_op sysrq_showregs_op = {
295 .handler = sysrq_handle_showregs,
296 .help_msg = "show-registers(p)",
297 .action_msg = "Show Regs",
298 .enable_mask = SYSRQ_ENABLE_DUMP,
301 static void sysrq_handle_showstate(int key)
304 show_workqueue_state();
306 static const struct sysrq_key_op sysrq_showstate_op = {
307 .handler = sysrq_handle_showstate,
308 .help_msg = "show-task-states(t)",
309 .action_msg = "Show State",
310 .enable_mask = SYSRQ_ENABLE_DUMP,
313 static void sysrq_handle_showstate_blocked(int key)
315 show_state_filter(TASK_UNINTERRUPTIBLE);
317 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
318 .handler = sysrq_handle_showstate_blocked,
319 .help_msg = "show-blocked-tasks(w)",
320 .action_msg = "Show Blocked State",
321 .enable_mask = SYSRQ_ENABLE_DUMP,
324 #ifdef CONFIG_TRACING
325 #include <linux/ftrace.h>
327 static void sysrq_ftrace_dump(int key)
329 ftrace_dump(DUMP_ALL);
331 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
332 .handler = sysrq_ftrace_dump,
333 .help_msg = "dump-ftrace-buffer(z)",
334 .action_msg = "Dump ftrace buffer",
335 .enable_mask = SYSRQ_ENABLE_DUMP,
338 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
341 static void sysrq_handle_showmem(int key)
345 static const struct sysrq_key_op sysrq_showmem_op = {
346 .handler = sysrq_handle_showmem,
347 .help_msg = "show-memory-usage(m)",
348 .action_msg = "Show Memory",
349 .enable_mask = SYSRQ_ENABLE_DUMP,
353 * Signal sysrq helper function. Sends a signal to all user processes.
355 static void send_sig_all(int sig)
357 struct task_struct *p;
359 read_lock(&tasklist_lock);
360 for_each_process(p) {
361 if (p->flags & PF_KTHREAD)
363 if (is_global_init(p))
366 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
368 read_unlock(&tasklist_lock);
371 static void sysrq_handle_term(int key)
373 send_sig_all(SIGTERM);
374 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
376 static const struct sysrq_key_op sysrq_term_op = {
377 .handler = sysrq_handle_term,
378 .help_msg = "terminate-all-tasks(e)",
379 .action_msg = "Terminate All Tasks",
380 .enable_mask = SYSRQ_ENABLE_SIGNAL,
383 static void moom_callback(struct work_struct *ignored)
385 const gfp_t gfp_mask = GFP_KERNEL;
386 struct oom_control oc = {
387 .zonelist = node_zonelist(first_memory_node, gfp_mask),
390 .gfp_mask = gfp_mask,
394 mutex_lock(&oom_lock);
395 if (!out_of_memory(&oc))
396 pr_info("OOM request ignored. No task eligible\n");
397 mutex_unlock(&oom_lock);
400 static DECLARE_WORK(moom_work, moom_callback);
402 static void sysrq_handle_moom(int key)
404 schedule_work(&moom_work);
406 static const struct sysrq_key_op sysrq_moom_op = {
407 .handler = sysrq_handle_moom,
408 .help_msg = "memory-full-oom-kill(f)",
409 .action_msg = "Manual OOM execution",
410 .enable_mask = SYSRQ_ENABLE_SIGNAL,
413 static void sysrq_handle_thaw(int key)
415 emergency_thaw_all();
417 static const struct sysrq_key_op sysrq_thaw_op = {
418 .handler = sysrq_handle_thaw,
419 .help_msg = "thaw-filesystems(j)",
420 .action_msg = "Emergency Thaw of all frozen filesystems",
421 .enable_mask = SYSRQ_ENABLE_SIGNAL,
424 static void sysrq_handle_kill(int key)
426 send_sig_all(SIGKILL);
427 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
429 static const struct sysrq_key_op sysrq_kill_op = {
430 .handler = sysrq_handle_kill,
431 .help_msg = "kill-all-tasks(i)",
432 .action_msg = "Kill All Tasks",
433 .enable_mask = SYSRQ_ENABLE_SIGNAL,
436 static void sysrq_handle_unrt(int key)
438 normalize_rt_tasks();
440 static const struct sysrq_key_op sysrq_unrt_op = {
441 .handler = sysrq_handle_unrt,
442 .help_msg = "nice-all-RT-tasks(n)",
443 .action_msg = "Nice All RT Tasks",
444 .enable_mask = SYSRQ_ENABLE_RTNICE,
447 /* Key Operations table and lock */
448 static DEFINE_SPINLOCK(sysrq_key_table_lock);
450 static const struct sysrq_key_op *sysrq_key_table[62] = {
451 &sysrq_loglevel_op, /* 0 */
452 &sysrq_loglevel_op, /* 1 */
453 &sysrq_loglevel_op, /* 2 */
454 &sysrq_loglevel_op, /* 3 */
455 &sysrq_loglevel_op, /* 4 */
456 &sysrq_loglevel_op, /* 5 */
457 &sysrq_loglevel_op, /* 6 */
458 &sysrq_loglevel_op, /* 7 */
459 &sysrq_loglevel_op, /* 8 */
460 &sysrq_loglevel_op, /* 9 */
463 * a: Don't use for system provided sysrqs, it is handled specially on
464 * sparc and will never arrive.
467 &sysrq_reboot_op, /* b */
468 &sysrq_crash_op, /* c */
469 &sysrq_showlocks_op, /* d */
470 &sysrq_term_op, /* e */
471 &sysrq_moom_op, /* f */
472 /* g: May be registered for the kernel debugger */
474 NULL, /* h - reserved for help */
475 &sysrq_kill_op, /* i */
477 &sysrq_thaw_op, /* j */
481 &sysrq_SAK_op, /* k */
483 &sysrq_showallcpus_op, /* l */
487 &sysrq_showmem_op, /* m */
488 &sysrq_unrt_op, /* n */
489 /* o: This will often be registered as 'Off' at init time */
491 &sysrq_showregs_op, /* p */
492 &sysrq_show_timers_op, /* q */
493 &sysrq_unraw_op, /* r */
494 &sysrq_sync_op, /* s */
495 &sysrq_showstate_op, /* t */
496 &sysrq_mountro_op, /* u */
497 /* v: May be registered for frame buffer console restore */
499 &sysrq_showstate_blocked_op, /* w */
500 /* x: May be registered on mips for TLB dump */
501 /* x: May be registered on ppc/powerpc for xmon */
502 /* x: May be registered on sparc64 for global PMU dump */
504 /* y: May be registered on sparc64 for global register dump */
506 &sysrq_ftrace_dump_op, /* z */
535 /* key2index calculation, -1 on invalid index */
536 static int sysrq_key_table_key2index(int key)
540 if ((key >= '0') && (key <= '9'))
542 else if ((key >= 'a') && (key <= 'z'))
543 retval = key + 10 - 'a';
544 else if ((key >= 'A') && (key <= 'Z'))
545 retval = key + 36 - 'A';
552 * get and put functions for the table, exposed to modules.
554 static const struct sysrq_key_op *__sysrq_get_key_op(int key)
556 const struct sysrq_key_op *op_p = NULL;
559 i = sysrq_key_table_key2index(key);
561 op_p = sysrq_key_table[i];
566 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p)
568 int i = sysrq_key_table_key2index(key);
571 sysrq_key_table[i] = op_p;
574 void __handle_sysrq(int key, bool check_mask)
576 const struct sysrq_key_op *op_p;
578 int orig_suppress_printk;
581 orig_suppress_printk = suppress_printk;
587 * Raise the apparent loglevel to maximum so that the sysrq header
588 * is shown to provide the user with positive feedback. We do not
589 * simply emit this at KERN_EMERG as that would change message
590 * routing in the consumers of /proc/kmsg.
592 orig_log_level = console_loglevel;
593 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
595 op_p = __sysrq_get_key_op(key);
598 * Should we check for enabled operations (/proc/sysrq-trigger
599 * should not) and is the invoked operation enabled?
601 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
602 pr_info("%s\n", op_p->action_msg);
603 console_loglevel = orig_log_level;
606 pr_info("This sysrq operation is disabled.\n");
607 console_loglevel = orig_log_level;
611 /* Only print the help msg once per handler */
612 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
613 if (sysrq_key_table[i]) {
616 for (j = 0; sysrq_key_table[i] !=
617 sysrq_key_table[j]; j++)
621 pr_cont("%s ", sysrq_key_table[i]->help_msg);
625 console_loglevel = orig_log_level;
630 suppress_printk = orig_suppress_printk;
633 void handle_sysrq(int key)
636 __handle_sysrq(key, true);
638 EXPORT_SYMBOL(handle_sysrq);
641 static int sysrq_reset_downtime_ms;
643 /* Simple translation table for the SysRq keys */
644 static const unsigned char sysrq_xlate[KEY_CNT] =
645 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
646 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
647 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
648 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
649 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
650 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
651 "\r\000/"; /* 0x60 - 0x6f */
654 struct input_handle handle;
655 struct work_struct reinject_work;
656 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
658 unsigned int alt_use;
660 unsigned int shift_use;
665 /* reset sequence handling */
667 bool reset_requested;
668 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
671 int reset_seq_version;
672 struct timer_list keyreset_timer;
675 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
676 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
677 static unsigned int sysrq_reset_seq_len;
678 static unsigned int sysrq_reset_seq_version = 1;
680 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
685 state->reset_seq_cnt = 0;
687 for (i = 0; i < sysrq_reset_seq_len; i++) {
688 key = sysrq_reset_seq[i];
690 if (key == KEY_RESERVED || key > KEY_MAX)
693 __set_bit(key, state->reset_keybit);
694 state->reset_seq_len++;
696 if (test_bit(key, state->key_down))
697 state->reset_seq_cnt++;
700 /* Disable reset until old keys are not released */
701 state->reset_canceled = state->reset_seq_cnt != 0;
703 state->reset_seq_version = sysrq_reset_seq_version;
706 static void sysrq_do_reset(struct timer_list *t)
708 struct sysrq_state *state = from_timer(state, t, keyreset_timer);
710 state->reset_requested = true;
715 static void sysrq_handle_reset_request(struct sysrq_state *state)
717 if (state->reset_requested)
718 __handle_sysrq(sysrq_xlate[KEY_B], false);
720 if (sysrq_reset_downtime_ms)
721 mod_timer(&state->keyreset_timer,
722 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
724 sysrq_do_reset(&state->keyreset_timer);
727 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
728 unsigned int code, int value)
730 if (!test_bit(code, state->reset_keybit)) {
732 * Pressing any key _not_ in reset sequence cancels
733 * the reset sequence. Also cancelling the timer in
734 * case additional keys were pressed after a reset
735 * has been requested.
737 if (value && state->reset_seq_cnt) {
738 state->reset_canceled = true;
739 del_timer(&state->keyreset_timer);
741 } else if (value == 0) {
743 * Key release - all keys in the reset sequence need
744 * to be pressed and held for the reset timeout
747 del_timer(&state->keyreset_timer);
749 if (--state->reset_seq_cnt == 0)
750 state->reset_canceled = false;
751 } else if (value == 1) {
752 /* key press, not autorepeat */
753 if (++state->reset_seq_cnt == state->reset_seq_len &&
754 !state->reset_canceled) {
755 sysrq_handle_reset_request(state);
761 static void sysrq_of_get_keyreset_config(void)
764 struct device_node *np;
765 struct property *prop;
768 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
770 pr_debug("No sysrq node found");
774 /* Reset in case a __weak definition was present */
775 sysrq_reset_seq_len = 0;
777 of_property_for_each_u32(np, "keyset", prop, p, key) {
778 if (key == KEY_RESERVED || key > KEY_MAX ||
779 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
782 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
785 /* Get reset timeout if any. */
786 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
791 static void sysrq_of_get_keyreset_config(void)
796 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
798 struct sysrq_state *sysrq =
799 container_of(work, struct sysrq_state, reinject_work);
800 struct input_handle *handle = &sysrq->handle;
801 unsigned int alt_code = sysrq->alt_use;
803 if (sysrq->need_reinject) {
804 /* we do not want the assignment to be reordered */
805 sysrq->reinjecting = true;
808 /* Simulate press and release of Alt + SysRq */
809 input_inject_event(handle, EV_KEY, alt_code, 1);
810 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
811 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
813 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
814 input_inject_event(handle, EV_KEY, alt_code, 0);
815 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
818 sysrq->reinjecting = false;
822 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
823 unsigned int code, int value)
825 bool was_active = sysrq->active;
833 /* One of ALTs is being released */
834 if (sysrq->active && code == sysrq->alt_use)
835 sysrq->active = false;
837 sysrq->alt = KEY_RESERVED;
839 } else if (value != 2) {
841 sysrq->need_reinject = false;
848 sysrq->shift = KEY_RESERVED;
854 if (value == 1 && sysrq->alt != KEY_RESERVED) {
855 sysrq->active = true;
856 sysrq->alt_use = sysrq->alt;
857 /* either RESERVED (for released) or actual code */
858 sysrq->shift_use = sysrq->shift;
860 * If nothing else will be pressed we'll need
861 * to re-inject Alt-SysRq keysroke.
863 sysrq->need_reinject = true;
867 * Pretend that sysrq was never pressed at all. This
868 * is needed to properly handle KGDB which will try
869 * to release all keys after exiting debugger. If we
870 * do not clear key bit it KGDB will end up sending
871 * release events for Alt and SysRq, potentially
872 * triggering print screen function.
875 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
880 if (sysrq->active && value && value != 2) {
881 unsigned char c = sysrq_xlate[code];
883 sysrq->need_reinject = false;
884 if (sysrq->shift_use != KEY_RESERVED)
886 __handle_sysrq(c, true);
891 suppress = sysrq->active;
893 if (!sysrq->active) {
896 * See if reset sequence has changed since the last time.
898 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
899 sysrq_parse_reset_sequence(sysrq);
902 * If we are not suppressing key presses keep track of
903 * keyboard state so we can release keys that have been
904 * pressed before entering SysRq mode.
907 set_bit(code, sysrq->key_down);
909 clear_bit(code, sysrq->key_down);
912 schedule_work(&sysrq->reinject_work);
914 /* Check for reset sequence */
915 sysrq_detect_reset_sequence(sysrq, code, value);
917 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
919 * Pass on release events for keys that was pressed before
920 * entering SysRq mode.
928 static bool sysrq_filter(struct input_handle *handle,
929 unsigned int type, unsigned int code, int value)
931 struct sysrq_state *sysrq = handle->private;
935 * Do not filter anything if we are in the process of re-injecting
936 * Alt+SysRq combination.
938 if (sysrq->reinjecting)
948 suppress = sysrq_handle_keypress(sysrq, code, value);
952 suppress = sysrq->active;
959 static int sysrq_connect(struct input_handler *handler,
960 struct input_dev *dev,
961 const struct input_device_id *id)
963 struct sysrq_state *sysrq;
966 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
970 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
972 sysrq->handle.dev = dev;
973 sysrq->handle.handler = handler;
974 sysrq->handle.name = "sysrq";
975 sysrq->handle.private = sysrq;
976 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
978 error = input_register_handle(&sysrq->handle);
980 pr_err("Failed to register input sysrq handler, error %d\n",
985 error = input_open_device(&sysrq->handle);
987 pr_err("Failed to open input device, error %d\n", error);
994 input_unregister_handle(&sysrq->handle);
1000 static void sysrq_disconnect(struct input_handle *handle)
1002 struct sysrq_state *sysrq = handle->private;
1004 input_close_device(handle);
1005 cancel_work_sync(&sysrq->reinject_work);
1006 del_timer_sync(&sysrq->keyreset_timer);
1007 input_unregister_handle(handle);
1012 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1013 * keyboards have SysRq key predefined and so user may add it to keymap
1014 * later, but we expect all such keyboards to have left alt.
1016 static const struct input_device_id sysrq_ids[] = {
1018 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1019 INPUT_DEVICE_ID_MATCH_KEYBIT,
1020 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1021 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1026 static struct input_handler sysrq_handler = {
1027 .filter = sysrq_filter,
1028 .connect = sysrq_connect,
1029 .disconnect = sysrq_disconnect,
1031 .id_table = sysrq_ids,
1034 static inline void sysrq_register_handler(void)
1038 sysrq_of_get_keyreset_config();
1040 error = input_register_handler(&sysrq_handler);
1042 pr_err("Failed to register input handler, error %d", error);
1045 static inline void sysrq_unregister_handler(void)
1047 input_unregister_handler(&sysrq_handler);
1050 static int sysrq_reset_seq_param_set(const char *buffer,
1051 const struct kernel_param *kp)
1056 error = kstrtoul(buffer, 0, &val);
1063 *((unsigned short *)kp->arg) = val;
1064 sysrq_reset_seq_version++;
1069 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1070 .get = param_get_ushort,
1071 .set = sysrq_reset_seq_param_set,
1074 #define param_check_sysrq_reset_seq(name, p) \
1075 __param_check(name, p, unsigned short)
1078 * not really modular, but the easiest way to keep compat with existing
1079 * bootargs behaviour is to continue using module_param here.
1081 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1082 &sysrq_reset_seq_len, 0644);
1084 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1088 static inline void sysrq_register_handler(void)
1092 static inline void sysrq_unregister_handler(void)
1096 #endif /* CONFIG_INPUT */
1098 int sysrq_toggle_support(int enable_mask)
1100 bool was_enabled = sysrq_on();
1102 sysrq_enabled = enable_mask;
1104 if (was_enabled != sysrq_on()) {
1106 sysrq_register_handler();
1108 sysrq_unregister_handler();
1113 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1115 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p,
1116 const struct sysrq_key_op *remove_op_p)
1120 spin_lock(&sysrq_key_table_lock);
1121 if (__sysrq_get_key_op(key) == remove_op_p) {
1122 __sysrq_put_key_op(key, insert_op_p);
1127 spin_unlock(&sysrq_key_table_lock);
1130 * A concurrent __handle_sysrq either got the old op or the new op.
1131 * Wait for it to go away before returning, so the code for an old
1132 * op is not freed (eg. on module unload) while it is in use.
1139 int register_sysrq_key(int key, const struct sysrq_key_op *op_p)
1141 return __sysrq_swap_key_ops(key, op_p, NULL);
1143 EXPORT_SYMBOL(register_sysrq_key);
1145 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)
1147 return __sysrq_swap_key_ops(key, NULL, op_p);
1149 EXPORT_SYMBOL(unregister_sysrq_key);
1151 #ifdef CONFIG_PROC_FS
1153 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1155 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1156 size_t count, loff_t *ppos)
1161 if (get_user(c, buf))
1163 __handle_sysrq(c, false);
1169 static const struct proc_ops sysrq_trigger_proc_ops = {
1170 .proc_write = write_sysrq_trigger,
1171 .proc_lseek = noop_llseek,
1174 static void sysrq_init_procfs(void)
1176 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1177 &sysrq_trigger_proc_ops))
1178 pr_err("Failed to register proc interface\n");
1183 static inline void sysrq_init_procfs(void)
1187 #endif /* CONFIG_PROC_FS */
1189 static int __init sysrq_init(void)
1191 sysrq_init_procfs();
1194 sysrq_register_handler();
1198 device_initcall(sysrq_init);