xref: /openbmc/linux/drivers/tty/sysrq.c (revision c2a311dc)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *	Linux Magic System Request Key Hacks
4  *
5  *	(c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
6  *	based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
7  *
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
11  *
12  *	Copyright (c) 2010 Dmitry Torokhov
13  *	Input handler conversion
14  */
15 
16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17 
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>
24 #include <linux/mm.h>
25 #include <linux/fs.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>
52 #include <linux/of.h>
53 #include <linux/rcupdate.h>
54 
55 #include <asm/ptrace.h>
56 #include <asm/irq_regs.h>
57 
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;
61 
62 static bool sysrq_on(void)
63 {
64 	return sysrq_enabled || sysrq_always_enabled;
65 }
66 
67 /**
68  * sysrq_mask - Getter for sysrq_enabled mask.
69  *
70  * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
71  */
72 int sysrq_mask(void)
73 {
74 	if (sysrq_always_enabled)
75 		return 1;
76 	return sysrq_enabled;
77 }
78 EXPORT_SYMBOL_GPL(sysrq_mask);
79 
80 /*
81  * A value of 1 means 'all', other nonzero values are an op mask:
82  */
83 static bool sysrq_on_mask(int mask)
84 {
85 	return sysrq_always_enabled ||
86 	       sysrq_enabled == 1 ||
87 	       (sysrq_enabled & mask);
88 }
89 
90 static int __init sysrq_always_enabled_setup(char *str)
91 {
92 	sysrq_always_enabled = true;
93 	pr_info("sysrq always enabled.\n");
94 
95 	return 1;
96 }
97 
98 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
99 
100 
101 static void sysrq_handle_loglevel(u8 key)
102 {
103 	u8 loglevel = key - '0';
104 
105 	console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
106 	pr_info("Loglevel set to %u\n", loglevel);
107 	console_loglevel = loglevel;
108 }
109 static const struct sysrq_key_op sysrq_loglevel_op = {
110 	.handler	= sysrq_handle_loglevel,
111 	.help_msg	= "loglevel(0-9)",
112 	.action_msg	= "Changing Loglevel",
113 	.enable_mask	= SYSRQ_ENABLE_LOG,
114 };
115 
116 #ifdef CONFIG_VT
117 static void sysrq_handle_SAK(u8 key)
118 {
119 	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
120 
121 	schedule_work(SAK_work);
122 }
123 static const struct sysrq_key_op sysrq_SAK_op = {
124 	.handler	= sysrq_handle_SAK,
125 	.help_msg	= "sak(k)",
126 	.action_msg	= "SAK",
127 	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
128 };
129 #else
130 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
131 #endif
132 
133 #ifdef CONFIG_VT
134 static void sysrq_handle_unraw(u8 key)
135 {
136 	vt_reset_unicode(fg_console);
137 }
138 
139 static const struct sysrq_key_op sysrq_unraw_op = {
140 	.handler	= sysrq_handle_unraw,
141 	.help_msg	= "unraw(r)",
142 	.action_msg	= "Keyboard mode set to system default",
143 	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
144 };
145 #else
146 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
147 #endif /* CONFIG_VT */
148 
149 static void sysrq_handle_crash(u8 key)
150 {
151 	/* release the RCU read lock before crashing */
152 	rcu_read_unlock();
153 
154 	panic("sysrq triggered crash\n");
155 }
156 static const struct sysrq_key_op sysrq_crash_op = {
157 	.handler	= sysrq_handle_crash,
158 	.help_msg	= "crash(c)",
159 	.action_msg	= "Trigger a crash",
160 	.enable_mask	= SYSRQ_ENABLE_DUMP,
161 };
162 
163 static void sysrq_handle_reboot(u8 key)
164 {
165 	lockdep_off();
166 	local_irq_enable();
167 	emergency_restart();
168 }
169 static const struct sysrq_key_op sysrq_reboot_op = {
170 	.handler	= sysrq_handle_reboot,
171 	.help_msg	= "reboot(b)",
172 	.action_msg	= "Resetting",
173 	.enable_mask	= SYSRQ_ENABLE_BOOT,
174 };
175 
176 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
177 
178 static void sysrq_handle_sync(u8 key)
179 {
180 	emergency_sync();
181 }
182 static const struct sysrq_key_op sysrq_sync_op = {
183 	.handler	= sysrq_handle_sync,
184 	.help_msg	= "sync(s)",
185 	.action_msg	= "Emergency Sync",
186 	.enable_mask	= SYSRQ_ENABLE_SYNC,
187 };
188 
189 static void sysrq_handle_show_timers(u8 key)
190 {
191 	sysrq_timer_list_show();
192 }
193 
194 static const struct sysrq_key_op sysrq_show_timers_op = {
195 	.handler	= sysrq_handle_show_timers,
196 	.help_msg	= "show-all-timers(q)",
197 	.action_msg	= "Show clockevent devices & pending hrtimers (no others)",
198 };
199 
200 static void sysrq_handle_mountro(u8 key)
201 {
202 	emergency_remount();
203 }
204 static const struct sysrq_key_op sysrq_mountro_op = {
205 	.handler	= sysrq_handle_mountro,
206 	.help_msg	= "unmount(u)",
207 	.action_msg	= "Emergency Remount R/O",
208 	.enable_mask	= SYSRQ_ENABLE_REMOUNT,
209 };
210 
211 #ifdef CONFIG_LOCKDEP
212 static void sysrq_handle_showlocks(u8 key)
213 {
214 	debug_show_all_locks();
215 }
216 
217 static const struct sysrq_key_op sysrq_showlocks_op = {
218 	.handler	= sysrq_handle_showlocks,
219 	.help_msg	= "show-all-locks(d)",
220 	.action_msg	= "Show Locks Held",
221 };
222 #else
223 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
224 #endif
225 
226 #ifdef CONFIG_SMP
227 static DEFINE_RAW_SPINLOCK(show_lock);
228 
229 static void showacpu(void *dummy)
230 {
231 	unsigned long flags;
232 
233 	/* Idle CPUs have no interesting backtrace. */
234 	if (idle_cpu(smp_processor_id())) {
235 		pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
236 		return;
237 	}
238 
239 	raw_spin_lock_irqsave(&show_lock, flags);
240 	pr_info("CPU%d:\n", smp_processor_id());
241 	show_stack(NULL, NULL, KERN_INFO);
242 	raw_spin_unlock_irqrestore(&show_lock, flags);
243 }
244 
245 static void sysrq_showregs_othercpus(struct work_struct *dummy)
246 {
247 	smp_call_function(showacpu, NULL, 0);
248 }
249 
250 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
251 
252 static void sysrq_handle_showallcpus(u8 key)
253 {
254 	/*
255 	 * Fall back to the workqueue based printing if the
256 	 * backtrace printing did not succeed or the
257 	 * architecture has no support for it:
258 	 */
259 	if (!trigger_all_cpu_backtrace()) {
260 		struct pt_regs *regs = NULL;
261 
262 		if (in_hardirq())
263 			regs = get_irq_regs();
264 
265 		pr_info("CPU%d:\n", smp_processor_id());
266 		if (regs)
267 			show_regs(regs);
268 		else
269 			show_stack(NULL, NULL, KERN_INFO);
270 
271 		schedule_work(&sysrq_showallcpus);
272 	}
273 }
274 
275 static const struct sysrq_key_op sysrq_showallcpus_op = {
276 	.handler	= sysrq_handle_showallcpus,
277 	.help_msg	= "show-backtrace-all-active-cpus(l)",
278 	.action_msg	= "Show backtrace of all active CPUs",
279 	.enable_mask	= SYSRQ_ENABLE_DUMP,
280 };
281 #else
282 #define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL)
283 #endif
284 
285 static void sysrq_handle_showregs(u8 key)
286 {
287 	struct pt_regs *regs = NULL;
288 
289 	if (in_hardirq())
290 		regs = get_irq_regs();
291 	if (regs)
292 		show_regs(regs);
293 	perf_event_print_debug();
294 }
295 static const struct sysrq_key_op sysrq_showregs_op = {
296 	.handler	= sysrq_handle_showregs,
297 	.help_msg	= "show-registers(p)",
298 	.action_msg	= "Show Regs",
299 	.enable_mask	= SYSRQ_ENABLE_DUMP,
300 };
301 
302 static void sysrq_handle_showstate(u8 key)
303 {
304 	show_state();
305 	show_all_workqueues();
306 }
307 static const struct sysrq_key_op sysrq_showstate_op = {
308 	.handler	= sysrq_handle_showstate,
309 	.help_msg	= "show-task-states(t)",
310 	.action_msg	= "Show State",
311 	.enable_mask	= SYSRQ_ENABLE_DUMP,
312 };
313 
314 static void sysrq_handle_showstate_blocked(u8 key)
315 {
316 	show_state_filter(TASK_UNINTERRUPTIBLE);
317 }
318 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
319 	.handler	= sysrq_handle_showstate_blocked,
320 	.help_msg	= "show-blocked-tasks(w)",
321 	.action_msg	= "Show Blocked State",
322 	.enable_mask	= SYSRQ_ENABLE_DUMP,
323 };
324 
325 #ifdef CONFIG_TRACING
326 #include <linux/ftrace.h>
327 
328 static void sysrq_ftrace_dump(u8 key)
329 {
330 	ftrace_dump(DUMP_ALL);
331 }
332 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
333 	.handler	= sysrq_ftrace_dump,
334 	.help_msg	= "dump-ftrace-buffer(z)",
335 	.action_msg	= "Dump ftrace buffer",
336 	.enable_mask	= SYSRQ_ENABLE_DUMP,
337 };
338 #else
339 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
340 #endif
341 
342 static void sysrq_handle_showmem(u8 key)
343 {
344 	show_mem();
345 }
346 static const struct sysrq_key_op sysrq_showmem_op = {
347 	.handler	= sysrq_handle_showmem,
348 	.help_msg	= "show-memory-usage(m)",
349 	.action_msg	= "Show Memory",
350 	.enable_mask	= SYSRQ_ENABLE_DUMP,
351 };
352 
353 /*
354  * Signal sysrq helper function.  Sends a signal to all user processes.
355  */
356 static void send_sig_all(int sig)
357 {
358 	struct task_struct *p;
359 
360 	read_lock(&tasklist_lock);
361 	for_each_process(p) {
362 		if (p->flags & PF_KTHREAD)
363 			continue;
364 		if (is_global_init(p))
365 			continue;
366 
367 		do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
368 	}
369 	read_unlock(&tasklist_lock);
370 }
371 
372 static void sysrq_handle_term(u8 key)
373 {
374 	send_sig_all(SIGTERM);
375 	console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
376 }
377 static const struct sysrq_key_op sysrq_term_op = {
378 	.handler	= sysrq_handle_term,
379 	.help_msg	= "terminate-all-tasks(e)",
380 	.action_msg	= "Terminate All Tasks",
381 	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
382 };
383 
384 static void moom_callback(struct work_struct *ignored)
385 {
386 	const gfp_t gfp_mask = GFP_KERNEL;
387 	struct oom_control oc = {
388 		.zonelist = node_zonelist(first_memory_node, gfp_mask),
389 		.nodemask = NULL,
390 		.memcg = NULL,
391 		.gfp_mask = gfp_mask,
392 		.order = -1,
393 	};
394 
395 	mutex_lock(&oom_lock);
396 	if (!out_of_memory(&oc))
397 		pr_info("OOM request ignored. No task eligible\n");
398 	mutex_unlock(&oom_lock);
399 }
400 
401 static DECLARE_WORK(moom_work, moom_callback);
402 
403 static void sysrq_handle_moom(u8 key)
404 {
405 	schedule_work(&moom_work);
406 }
407 static const struct sysrq_key_op sysrq_moom_op = {
408 	.handler	= sysrq_handle_moom,
409 	.help_msg	= "memory-full-oom-kill(f)",
410 	.action_msg	= "Manual OOM execution",
411 	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
412 };
413 
414 #ifdef CONFIG_BLOCK
415 static void sysrq_handle_thaw(u8 key)
416 {
417 	emergency_thaw_all();
418 }
419 static const struct sysrq_key_op sysrq_thaw_op = {
420 	.handler	= sysrq_handle_thaw,
421 	.help_msg	= "thaw-filesystems(j)",
422 	.action_msg	= "Emergency Thaw of all frozen filesystems",
423 	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
424 };
425 #else
426 #define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL)
427 #endif
428 
429 static void sysrq_handle_kill(u8 key)
430 {
431 	send_sig_all(SIGKILL);
432 	console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
433 }
434 static const struct sysrq_key_op sysrq_kill_op = {
435 	.handler	= sysrq_handle_kill,
436 	.help_msg	= "kill-all-tasks(i)",
437 	.action_msg	= "Kill All Tasks",
438 	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
439 };
440 
441 static void sysrq_handle_unrt(u8 key)
442 {
443 	normalize_rt_tasks();
444 }
445 static const struct sysrq_key_op sysrq_unrt_op = {
446 	.handler	= sysrq_handle_unrt,
447 	.help_msg	= "nice-all-RT-tasks(n)",
448 	.action_msg	= "Nice All RT Tasks",
449 	.enable_mask	= SYSRQ_ENABLE_RTNICE,
450 };
451 
452 /* Key Operations table and lock */
453 static DEFINE_SPINLOCK(sysrq_key_table_lock);
454 
455 static const struct sysrq_key_op *sysrq_key_table[62] = {
456 	&sysrq_loglevel_op,		/* 0 */
457 	&sysrq_loglevel_op,		/* 1 */
458 	&sysrq_loglevel_op,		/* 2 */
459 	&sysrq_loglevel_op,		/* 3 */
460 	&sysrq_loglevel_op,		/* 4 */
461 	&sysrq_loglevel_op,		/* 5 */
462 	&sysrq_loglevel_op,		/* 6 */
463 	&sysrq_loglevel_op,		/* 7 */
464 	&sysrq_loglevel_op,		/* 8 */
465 	&sysrq_loglevel_op,		/* 9 */
466 
467 	/*
468 	 * a: Don't use for system provided sysrqs, it is handled specially on
469 	 * sparc and will never arrive.
470 	 */
471 	NULL,				/* a */
472 	&sysrq_reboot_op,		/* b */
473 	&sysrq_crash_op,		/* c */
474 	&sysrq_showlocks_op,		/* d */
475 	&sysrq_term_op,			/* e */
476 	&sysrq_moom_op,			/* f */
477 	/* g: May be registered for the kernel debugger */
478 	NULL,				/* g */
479 	NULL,				/* h - reserved for help */
480 	&sysrq_kill_op,			/* i */
481 	&sysrq_thaw_op,			/* j */
482 	&sysrq_SAK_op,			/* k */
483 	&sysrq_showallcpus_op,		/* l */
484 	&sysrq_showmem_op,		/* m */
485 	&sysrq_unrt_op,			/* n */
486 	/* o: This will often be registered as 'Off' at init time */
487 	NULL,				/* o */
488 	&sysrq_showregs_op,		/* p */
489 	&sysrq_show_timers_op,		/* q */
490 	&sysrq_unraw_op,		/* r */
491 	&sysrq_sync_op,			/* s */
492 	&sysrq_showstate_op,		/* t */
493 	&sysrq_mountro_op,		/* u */
494 	/* v: May be registered for frame buffer console restore */
495 	NULL,				/* v */
496 	&sysrq_showstate_blocked_op,	/* w */
497 	/* x: May be registered on mips for TLB dump */
498 	/* x: May be registered on ppc/powerpc for xmon */
499 	/* x: May be registered on sparc64 for global PMU dump */
500 	NULL,				/* x */
501 	/* y: May be registered on sparc64 for global register dump */
502 	NULL,				/* y */
503 	&sysrq_ftrace_dump_op,		/* z */
504 	NULL,				/* A */
505 	NULL,				/* B */
506 	NULL,				/* C */
507 	NULL,				/* D */
508 	NULL,				/* E */
509 	NULL,				/* F */
510 	NULL,				/* G */
511 	NULL,				/* H */
512 	NULL,				/* I */
513 	NULL,				/* J */
514 	NULL,				/* K */
515 	NULL,				/* L */
516 	NULL,				/* M */
517 	NULL,				/* N */
518 	NULL,				/* O */
519 	NULL,				/* P */
520 	NULL,				/* Q */
521 	NULL,				/* R */
522 	NULL,				/* S */
523 	NULL,				/* T */
524 	NULL,				/* U */
525 	NULL,				/* V */
526 	NULL,				/* W */
527 	NULL,				/* X */
528 	NULL,				/* Y */
529 	NULL,				/* Z */
530 };
531 
532 /* key2index calculation, -1 on invalid index */
533 static int sysrq_key_table_key2index(u8 key)
534 {
535 	switch (key) {
536 	case '0' ... '9':
537 		return key - '0';
538 	case 'a' ... 'z':
539 		return key - 'a' + 10;
540 	case 'A' ... 'Z':
541 		return key - 'A' + 10 + 26;
542 	default:
543 		return -1;
544 	}
545 }
546 
547 /*
548  * get and put functions for the table, exposed to modules.
549  */
550 static const struct sysrq_key_op *__sysrq_get_key_op(u8 key)
551 {
552 	const struct sysrq_key_op *op_p = NULL;
553 	int i;
554 
555 	i = sysrq_key_table_key2index(key);
556 	if (i != -1)
557 		op_p = sysrq_key_table[i];
558 
559 	return op_p;
560 }
561 
562 static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p)
563 {
564 	int i = sysrq_key_table_key2index(key);
565 
566 	if (i != -1)
567 		sysrq_key_table[i] = op_p;
568 }
569 
570 void __handle_sysrq(u8 key, bool check_mask)
571 {
572 	const struct sysrq_key_op *op_p;
573 	int orig_log_level;
574 	int orig_suppress_printk;
575 	int i;
576 
577 	orig_suppress_printk = suppress_printk;
578 	suppress_printk = 0;
579 
580 	rcu_sysrq_start();
581 	rcu_read_lock();
582 	/*
583 	 * Raise the apparent loglevel to maximum so that the sysrq header
584 	 * is shown to provide the user with positive feedback.  We do not
585 	 * simply emit this at KERN_EMERG as that would change message
586 	 * routing in the consumers of /proc/kmsg.
587 	 */
588 	orig_log_level = console_loglevel;
589 	console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
590 
591 	op_p = __sysrq_get_key_op(key);
592 	if (op_p) {
593 		/*
594 		 * Should we check for enabled operations (/proc/sysrq-trigger
595 		 * should not) and is the invoked operation enabled?
596 		 */
597 		if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
598 			pr_info("%s\n", op_p->action_msg);
599 			console_loglevel = orig_log_level;
600 			op_p->handler(key);
601 		} else {
602 			pr_info("This sysrq operation is disabled.\n");
603 			console_loglevel = orig_log_level;
604 		}
605 	} else {
606 		pr_info("HELP : ");
607 		/* Only print the help msg once per handler */
608 		for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
609 			if (sysrq_key_table[i]) {
610 				int j;
611 
612 				for (j = 0; sysrq_key_table[i] !=
613 						sysrq_key_table[j]; j++)
614 					;
615 				if (j != i)
616 					continue;
617 				pr_cont("%s ", sysrq_key_table[i]->help_msg);
618 			}
619 		}
620 		pr_cont("\n");
621 		console_loglevel = orig_log_level;
622 	}
623 	rcu_read_unlock();
624 	rcu_sysrq_end();
625 
626 	suppress_printk = orig_suppress_printk;
627 }
628 
629 void handle_sysrq(u8 key)
630 {
631 	if (sysrq_on())
632 		__handle_sysrq(key, true);
633 }
634 EXPORT_SYMBOL(handle_sysrq);
635 
636 #ifdef CONFIG_INPUT
637 static int sysrq_reset_downtime_ms;
638 
639 /* Simple translation table for the SysRq keys */
640 static const unsigned char sysrq_xlate[KEY_CNT] =
641 	"\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
642 	"qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
643 	"dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
644 	"bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
645 	"\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
646 	"230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
647 	"\r\000/";                                      /* 0x60 - 0x6f */
648 
649 struct sysrq_state {
650 	struct input_handle handle;
651 	struct work_struct reinject_work;
652 	unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
653 	unsigned int alt;
654 	unsigned int alt_use;
655 	unsigned int shift;
656 	unsigned int shift_use;
657 	bool active;
658 	bool need_reinject;
659 	bool reinjecting;
660 
661 	/* reset sequence handling */
662 	bool reset_canceled;
663 	bool reset_requested;
664 	unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
665 	int reset_seq_len;
666 	int reset_seq_cnt;
667 	int reset_seq_version;
668 	struct timer_list keyreset_timer;
669 };
670 
671 #define SYSRQ_KEY_RESET_MAX	20 /* Should be plenty */
672 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
673 static unsigned int sysrq_reset_seq_len;
674 static unsigned int sysrq_reset_seq_version = 1;
675 
676 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
677 {
678 	int i;
679 	unsigned short key;
680 
681 	state->reset_seq_cnt = 0;
682 
683 	for (i = 0; i < sysrq_reset_seq_len; i++) {
684 		key = sysrq_reset_seq[i];
685 
686 		if (key == KEY_RESERVED || key > KEY_MAX)
687 			break;
688 
689 		__set_bit(key, state->reset_keybit);
690 		state->reset_seq_len++;
691 
692 		if (test_bit(key, state->key_down))
693 			state->reset_seq_cnt++;
694 	}
695 
696 	/* Disable reset until old keys are not released */
697 	state->reset_canceled = state->reset_seq_cnt != 0;
698 
699 	state->reset_seq_version = sysrq_reset_seq_version;
700 }
701 
702 static void sysrq_do_reset(struct timer_list *t)
703 {
704 	struct sysrq_state *state = from_timer(state, t, keyreset_timer);
705 
706 	state->reset_requested = true;
707 
708 	orderly_reboot();
709 }
710 
711 static void sysrq_handle_reset_request(struct sysrq_state *state)
712 {
713 	if (state->reset_requested)
714 		__handle_sysrq(sysrq_xlate[KEY_B], false);
715 
716 	if (sysrq_reset_downtime_ms)
717 		mod_timer(&state->keyreset_timer,
718 			jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
719 	else
720 		sysrq_do_reset(&state->keyreset_timer);
721 }
722 
723 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
724 					unsigned int code, int value)
725 {
726 	if (!test_bit(code, state->reset_keybit)) {
727 		/*
728 		 * Pressing any key _not_ in reset sequence cancels
729 		 * the reset sequence.  Also cancelling the timer in
730 		 * case additional keys were pressed after a reset
731 		 * has been requested.
732 		 */
733 		if (value && state->reset_seq_cnt) {
734 			state->reset_canceled = true;
735 			del_timer(&state->keyreset_timer);
736 		}
737 	} else if (value == 0) {
738 		/*
739 		 * Key release - all keys in the reset sequence need
740 		 * to be pressed and held for the reset timeout
741 		 * to hold.
742 		 */
743 		del_timer(&state->keyreset_timer);
744 
745 		if (--state->reset_seq_cnt == 0)
746 			state->reset_canceled = false;
747 	} else if (value == 1) {
748 		/* key press, not autorepeat */
749 		if (++state->reset_seq_cnt == state->reset_seq_len &&
750 		    !state->reset_canceled) {
751 			sysrq_handle_reset_request(state);
752 		}
753 	}
754 }
755 
756 #ifdef CONFIG_OF
757 static void sysrq_of_get_keyreset_config(void)
758 {
759 	u32 key;
760 	struct device_node *np;
761 	struct property *prop;
762 	const __be32 *p;
763 
764 	np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
765 	if (!np) {
766 		pr_debug("No sysrq node found");
767 		return;
768 	}
769 
770 	/* Reset in case a __weak definition was present */
771 	sysrq_reset_seq_len = 0;
772 
773 	of_property_for_each_u32(np, "keyset", prop, p, key) {
774 		if (key == KEY_RESERVED || key > KEY_MAX ||
775 		    sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
776 			break;
777 
778 		sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
779 	}
780 
781 	/* Get reset timeout if any. */
782 	of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
783 
784 	of_node_put(np);
785 }
786 #else
787 static void sysrq_of_get_keyreset_config(void)
788 {
789 }
790 #endif
791 
792 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
793 {
794 	struct sysrq_state *sysrq =
795 			container_of(work, struct sysrq_state, reinject_work);
796 	struct input_handle *handle = &sysrq->handle;
797 	unsigned int alt_code = sysrq->alt_use;
798 
799 	if (sysrq->need_reinject) {
800 		/* we do not want the assignment to be reordered */
801 		sysrq->reinjecting = true;
802 		mb();
803 
804 		/* Simulate press and release of Alt + SysRq */
805 		input_inject_event(handle, EV_KEY, alt_code, 1);
806 		input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
807 		input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
808 
809 		input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
810 		input_inject_event(handle, EV_KEY, alt_code, 0);
811 		input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
812 
813 		mb();
814 		sysrq->reinjecting = false;
815 	}
816 }
817 
818 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
819 				  unsigned int code, int value)
820 {
821 	bool was_active = sysrq->active;
822 	bool suppress;
823 
824 	switch (code) {
825 
826 	case KEY_LEFTALT:
827 	case KEY_RIGHTALT:
828 		if (!value) {
829 			/* One of ALTs is being released */
830 			if (sysrq->active && code == sysrq->alt_use)
831 				sysrq->active = false;
832 
833 			sysrq->alt = KEY_RESERVED;
834 
835 		} else if (value != 2) {
836 			sysrq->alt = code;
837 			sysrq->need_reinject = false;
838 		}
839 		break;
840 
841 	case KEY_LEFTSHIFT:
842 	case KEY_RIGHTSHIFT:
843 		if (!value)
844 			sysrq->shift = KEY_RESERVED;
845 		else if (value != 2)
846 			sysrq->shift = code;
847 		if (sysrq->active)
848 			sysrq->shift_use = sysrq->shift;
849 		break;
850 
851 	case KEY_SYSRQ:
852 		if (value == 1 && sysrq->alt != KEY_RESERVED) {
853 			sysrq->active = true;
854 			sysrq->alt_use = sysrq->alt;
855 			/* either RESERVED (for released) or actual code */
856 			sysrq->shift_use = sysrq->shift;
857 			/*
858 			 * If nothing else will be pressed we'll need
859 			 * to re-inject Alt-SysRq keysroke.
860 			 */
861 			sysrq->need_reinject = true;
862 		}
863 
864 		/*
865 		 * Pretend that sysrq was never pressed at all. This
866 		 * is needed to properly handle KGDB which will try
867 		 * to release all keys after exiting debugger. If we
868 		 * do not clear key bit it KGDB will end up sending
869 		 * release events for Alt and SysRq, potentially
870 		 * triggering print screen function.
871 		 */
872 		if (sysrq->active)
873 			clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
874 
875 		break;
876 
877 	default:
878 		if (sysrq->active && value && value != 2) {
879 			unsigned char c = sysrq_xlate[code];
880 
881 			sysrq->need_reinject = false;
882 			if (sysrq->shift_use != KEY_RESERVED)
883 				c = toupper(c);
884 			__handle_sysrq(c, true);
885 		}
886 		break;
887 	}
888 
889 	suppress = sysrq->active;
890 
891 	if (!sysrq->active) {
892 
893 		/*
894 		 * See if reset sequence has changed since the last time.
895 		 */
896 		if (sysrq->reset_seq_version != sysrq_reset_seq_version)
897 			sysrq_parse_reset_sequence(sysrq);
898 
899 		/*
900 		 * If we are not suppressing key presses keep track of
901 		 * keyboard state so we can release keys that have been
902 		 * pressed before entering SysRq mode.
903 		 */
904 		if (value)
905 			set_bit(code, sysrq->key_down);
906 		else
907 			clear_bit(code, sysrq->key_down);
908 
909 		if (was_active)
910 			schedule_work(&sysrq->reinject_work);
911 
912 		/* Check for reset sequence */
913 		sysrq_detect_reset_sequence(sysrq, code, value);
914 
915 	} else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
916 		/*
917 		 * Pass on release events for keys that was pressed before
918 		 * entering SysRq mode.
919 		 */
920 		suppress = false;
921 	}
922 
923 	return suppress;
924 }
925 
926 static bool sysrq_filter(struct input_handle *handle,
927 			 unsigned int type, unsigned int code, int value)
928 {
929 	struct sysrq_state *sysrq = handle->private;
930 	bool suppress;
931 
932 	/*
933 	 * Do not filter anything if we are in the process of re-injecting
934 	 * Alt+SysRq combination.
935 	 */
936 	if (sysrq->reinjecting)
937 		return false;
938 
939 	switch (type) {
940 
941 	case EV_SYN:
942 		suppress = false;
943 		break;
944 
945 	case EV_KEY:
946 		suppress = sysrq_handle_keypress(sysrq, code, value);
947 		break;
948 
949 	default:
950 		suppress = sysrq->active;
951 		break;
952 	}
953 
954 	return suppress;
955 }
956 
957 static int sysrq_connect(struct input_handler *handler,
958 			 struct input_dev *dev,
959 			 const struct input_device_id *id)
960 {
961 	struct sysrq_state *sysrq;
962 	int error;
963 
964 	sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
965 	if (!sysrq)
966 		return -ENOMEM;
967 
968 	INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
969 
970 	sysrq->handle.dev = dev;
971 	sysrq->handle.handler = handler;
972 	sysrq->handle.name = "sysrq";
973 	sysrq->handle.private = sysrq;
974 	timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
975 
976 	error = input_register_handle(&sysrq->handle);
977 	if (error) {
978 		pr_err("Failed to register input sysrq handler, error %d\n",
979 			error);
980 		goto err_free;
981 	}
982 
983 	error = input_open_device(&sysrq->handle);
984 	if (error) {
985 		pr_err("Failed to open input device, error %d\n", error);
986 		goto err_unregister;
987 	}
988 
989 	return 0;
990 
991  err_unregister:
992 	input_unregister_handle(&sysrq->handle);
993  err_free:
994 	kfree(sysrq);
995 	return error;
996 }
997 
998 static void sysrq_disconnect(struct input_handle *handle)
999 {
1000 	struct sysrq_state *sysrq = handle->private;
1001 
1002 	input_close_device(handle);
1003 	cancel_work_sync(&sysrq->reinject_work);
1004 	timer_shutdown_sync(&sysrq->keyreset_timer);
1005 	input_unregister_handle(handle);
1006 	kfree(sysrq);
1007 }
1008 
1009 /*
1010  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1011  * keyboards have SysRq key predefined and so user may add it to keymap
1012  * later, but we expect all such keyboards to have left alt.
1013  */
1014 static const struct input_device_id sysrq_ids[] = {
1015 	{
1016 		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1017 				INPUT_DEVICE_ID_MATCH_KEYBIT,
1018 		.evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1019 		.keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1020 	},
1021 	{ },
1022 };
1023 
1024 static struct input_handler sysrq_handler = {
1025 	.filter		= sysrq_filter,
1026 	.connect	= sysrq_connect,
1027 	.disconnect	= sysrq_disconnect,
1028 	.name		= "sysrq",
1029 	.id_table	= sysrq_ids,
1030 };
1031 
1032 static inline void sysrq_register_handler(void)
1033 {
1034 	int error;
1035 
1036 	sysrq_of_get_keyreset_config();
1037 
1038 	error = input_register_handler(&sysrq_handler);
1039 	if (error)
1040 		pr_err("Failed to register input handler, error %d", error);
1041 }
1042 
1043 static inline void sysrq_unregister_handler(void)
1044 {
1045 	input_unregister_handler(&sysrq_handler);
1046 }
1047 
1048 static int sysrq_reset_seq_param_set(const char *buffer,
1049 				     const struct kernel_param *kp)
1050 {
1051 	unsigned long val;
1052 	int error;
1053 
1054 	error = kstrtoul(buffer, 0, &val);
1055 	if (error < 0)
1056 		return error;
1057 
1058 	if (val > KEY_MAX)
1059 		return -EINVAL;
1060 
1061 	*((unsigned short *)kp->arg) = val;
1062 	sysrq_reset_seq_version++;
1063 
1064 	return 0;
1065 }
1066 
1067 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1068 	.get	= param_get_ushort,
1069 	.set	= sysrq_reset_seq_param_set,
1070 };
1071 
1072 #define param_check_sysrq_reset_seq(name, p)	\
1073 	__param_check(name, p, unsigned short)
1074 
1075 /*
1076  * not really modular, but the easiest way to keep compat with existing
1077  * bootargs behaviour is to continue using module_param here.
1078  */
1079 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1080 			 &sysrq_reset_seq_len, 0644);
1081 
1082 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1083 
1084 #else
1085 
1086 static inline void sysrq_register_handler(void)
1087 {
1088 }
1089 
1090 static inline void sysrq_unregister_handler(void)
1091 {
1092 }
1093 
1094 #endif /* CONFIG_INPUT */
1095 
1096 int sysrq_toggle_support(int enable_mask)
1097 {
1098 	bool was_enabled = sysrq_on();
1099 
1100 	sysrq_enabled = enable_mask;
1101 
1102 	if (was_enabled != sysrq_on()) {
1103 		if (sysrq_on())
1104 			sysrq_register_handler();
1105 		else
1106 			sysrq_unregister_handler();
1107 	}
1108 
1109 	return 0;
1110 }
1111 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1112 
1113 static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p,
1114 				const struct sysrq_key_op *remove_op_p)
1115 {
1116 	int retval;
1117 
1118 	spin_lock(&sysrq_key_table_lock);
1119 	if (__sysrq_get_key_op(key) == remove_op_p) {
1120 		__sysrq_put_key_op(key, insert_op_p);
1121 		retval = 0;
1122 	} else {
1123 		retval = -1;
1124 	}
1125 	spin_unlock(&sysrq_key_table_lock);
1126 
1127 	/*
1128 	 * A concurrent __handle_sysrq either got the old op or the new op.
1129 	 * Wait for it to go away before returning, so the code for an old
1130 	 * op is not freed (eg. on module unload) while it is in use.
1131 	 */
1132 	synchronize_rcu();
1133 
1134 	return retval;
1135 }
1136 
1137 int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1138 {
1139 	return __sysrq_swap_key_ops(key, op_p, NULL);
1140 }
1141 EXPORT_SYMBOL(register_sysrq_key);
1142 
1143 int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1144 {
1145 	return __sysrq_swap_key_ops(key, NULL, op_p);
1146 }
1147 EXPORT_SYMBOL(unregister_sysrq_key);
1148 
1149 #ifdef CONFIG_PROC_FS
1150 /*
1151  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1152  */
1153 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1154 				   size_t count, loff_t *ppos)
1155 {
1156 	if (count) {
1157 		char c;
1158 
1159 		if (get_user(c, buf))
1160 			return -EFAULT;
1161 		__handle_sysrq(c, false);
1162 	}
1163 
1164 	return count;
1165 }
1166 
1167 static const struct proc_ops sysrq_trigger_proc_ops = {
1168 	.proc_write	= write_sysrq_trigger,
1169 	.proc_lseek	= noop_llseek,
1170 };
1171 
1172 static void sysrq_init_procfs(void)
1173 {
1174 	if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1175 			 &sysrq_trigger_proc_ops))
1176 		pr_err("Failed to register proc interface\n");
1177 }
1178 
1179 #else
1180 
1181 static inline void sysrq_init_procfs(void)
1182 {
1183 }
1184 
1185 #endif /* CONFIG_PROC_FS */
1186 
1187 static int __init sysrq_init(void)
1188 {
1189 	sysrq_init_procfs();
1190 
1191 	if (sysrq_on())
1192 		sysrq_register_handler();
1193 
1194 	return 0;
1195 }
1196 device_initcall(sysrq_init);
1197