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/interrupt.h>
23#include <linux/mm.h>
24#include <linux/fs.h>
25#include <linux/mount.h>
26#include <linux/kdev_t.h>
27#include <linux/major.h>
28#include <linux/reboot.h>
29#include <linux/sysrq.h>
30#include <linux/kbd_kern.h>
31#include <linux/proc_fs.h>
32#include <linux/nmi.h>
33#include <linux/quotaops.h>
34#include <linux/perf_event.h>
35#include <linux/kernel.h>
36#include <linux/module.h>
37#include <linux/suspend.h>
38#include <linux/writeback.h>
39#include <linux/swap.h>
40#include <linux/spinlock.h>
41#include <linux/vt_kern.h>
42#include <linux/workqueue.h>
43#include <linux/hrtimer.h>
44#include <linux/oom.h>
45#include <linux/slab.h>
46#include <linux/input.h>
47#include <linux/uaccess.h>
48#include <linux/moduleparam.h>
49#include <linux/jiffies.h>
50#include <linux/syscalls.h>
51#include <linux/of.h>
52#include <linux/rcupdate.h>
53
54#include <asm/ptrace.h>
55#include <asm/irq_regs.h>
56
57/* Whether we react on sysrq keys or just ignore them */
58static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
59static bool __read_mostly sysrq_always_enabled;
60
61static bool sysrq_on(void)
62{
63 return sysrq_enabled || sysrq_always_enabled;
64}
65
66/*
67 * A value of 1 means 'all', other nonzero values are an op mask:
68 */
69static bool sysrq_on_mask(int mask)
70{
71 return sysrq_always_enabled ||
72 sysrq_enabled == 1 ||
73 (sysrq_enabled & mask);
74}
75
76static int __init sysrq_always_enabled_setup(char *str)
77{
78 sysrq_always_enabled = true;
79 pr_info("sysrq always enabled.\n");
80
81 return 1;
82}
83
84__setup("sysrq_always_enabled", sysrq_always_enabled_setup);
85
86
87static void sysrq_handle_loglevel(int key)
88{
89 int i;
90
91 i = key - '0';
92 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
93 pr_info("Loglevel set to %d\n", i);
94 console_loglevel = i;
95}
96static struct sysrq_key_op sysrq_loglevel_op = {
97 .handler = sysrq_handle_loglevel,
98 .help_msg = "loglevel(0-9)",
99 .action_msg = "Changing Loglevel",
100 .enable_mask = SYSRQ_ENABLE_LOG,
101};
102
103#ifdef CONFIG_VT
104static void sysrq_handle_SAK(int key)
105{
106 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
107 schedule_work(SAK_work);
108}
109static struct sysrq_key_op sysrq_SAK_op = {
110 .handler = sysrq_handle_SAK,
111 .help_msg = "sak(k)",
112 .action_msg = "SAK",
113 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
114};
115#else
116#define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
117#endif
118
119#ifdef CONFIG_VT
120static void sysrq_handle_unraw(int key)
121{
122 vt_reset_unicode(fg_console);
123}
124
125static struct sysrq_key_op sysrq_unraw_op = {
126 .handler = sysrq_handle_unraw,
127 .help_msg = "unraw(r)",
128 .action_msg = "Keyboard mode set to system default",
129 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
130};
131#else
132#define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
133#endif /* CONFIG_VT */
134
135static void sysrq_handle_crash(int key)
136{
137 /* release the RCU read lock before crashing */
138 rcu_read_unlock();
139
140 panic("sysrq triggered crash\n");
141}
142static struct sysrq_key_op sysrq_crash_op = {
143 .handler = sysrq_handle_crash,
144 .help_msg = "crash(c)",
145 .action_msg = "Trigger a crash",
146 .enable_mask = SYSRQ_ENABLE_DUMP,
147};
148
149static void sysrq_handle_reboot(int key)
150{
151 lockdep_off();
152 local_irq_enable();
153 emergency_restart();
154}
155static struct sysrq_key_op sysrq_reboot_op = {
156 .handler = sysrq_handle_reboot,
157 .help_msg = "reboot(b)",
158 .action_msg = "Resetting",
159 .enable_mask = SYSRQ_ENABLE_BOOT,
160};
161
162static void sysrq_handle_sync(int key)
163{
164 emergency_sync();
165}
166static struct sysrq_key_op sysrq_sync_op = {
167 .handler = sysrq_handle_sync,
168 .help_msg = "sync(s)",
169 .action_msg = "Emergency Sync",
170 .enable_mask = SYSRQ_ENABLE_SYNC,
171};
172
173static void sysrq_handle_show_timers(int key)
174{
175 sysrq_timer_list_show();
176}
177
178static struct sysrq_key_op sysrq_show_timers_op = {
179 .handler = sysrq_handle_show_timers,
180 .help_msg = "show-all-timers(q)",
181 .action_msg = "Show clockevent devices & pending hrtimers (no others)",
182};
183
184static void sysrq_handle_mountro(int key)
185{
186 emergency_remount();
187}
188static struct sysrq_key_op sysrq_mountro_op = {
189 .handler = sysrq_handle_mountro,
190 .help_msg = "unmount(u)",
191 .action_msg = "Emergency Remount R/O",
192 .enable_mask = SYSRQ_ENABLE_REMOUNT,
193};
194
195#ifdef CONFIG_LOCKDEP
196static void sysrq_handle_showlocks(int key)
197{
198 debug_show_all_locks();
199}
200
201static struct sysrq_key_op sysrq_showlocks_op = {
202 .handler = sysrq_handle_showlocks,
203 .help_msg = "show-all-locks(d)",
204 .action_msg = "Show Locks Held",
205};
206#else
207#define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
208#endif
209
210#ifdef CONFIG_SMP
211static DEFINE_SPINLOCK(show_lock);
212
213static void showacpu(void *dummy)
214{
215 unsigned long flags;
216
217 /* Idle CPUs have no interesting backtrace. */
218 if (idle_cpu(smp_processor_id()))
219 return;
220
221 spin_lock_irqsave(&show_lock, flags);
222 pr_info("CPU%d:\n", smp_processor_id());
223 show_stack(NULL, NULL);
224 spin_unlock_irqrestore(&show_lock, flags);
225}
226
227static void sysrq_showregs_othercpus(struct work_struct *dummy)
228{
229 smp_call_function(showacpu, NULL, 0);
230}
231
232static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
233
234static void sysrq_handle_showallcpus(int key)
235{
236 /*
237 * Fall back to the workqueue based printing if the
238 * backtrace printing did not succeed or the
239 * architecture has no support for it:
240 */
241 if (!trigger_all_cpu_backtrace()) {
242 struct pt_regs *regs = NULL;
243
244 if (in_irq())
245 regs = get_irq_regs();
246 if (regs) {
247 pr_info("CPU%d:\n", smp_processor_id());
248 show_regs(regs);
249 }
250 schedule_work(&sysrq_showallcpus);
251 }
252}
253
254static struct sysrq_key_op sysrq_showallcpus_op = {
255 .handler = sysrq_handle_showallcpus,
256 .help_msg = "show-backtrace-all-active-cpus(l)",
257 .action_msg = "Show backtrace of all active CPUs",
258 .enable_mask = SYSRQ_ENABLE_DUMP,
259};
260#endif
261
262static void sysrq_handle_showregs(int key)
263{
264 struct pt_regs *regs = NULL;
265
266 if (in_irq())
267 regs = get_irq_regs();
268 if (regs)
269 show_regs(regs);
270 perf_event_print_debug();
271}
272static struct sysrq_key_op sysrq_showregs_op = {
273 .handler = sysrq_handle_showregs,
274 .help_msg = "show-registers(p)",
275 .action_msg = "Show Regs",
276 .enable_mask = SYSRQ_ENABLE_DUMP,
277};
278
279static void sysrq_handle_showstate(int key)
280{
281 show_state();
282 show_workqueue_state();
283}
284static struct sysrq_key_op sysrq_showstate_op = {
285 .handler = sysrq_handle_showstate,
286 .help_msg = "show-task-states(t)",
287 .action_msg = "Show State",
288 .enable_mask = SYSRQ_ENABLE_DUMP,
289};
290
291static void sysrq_handle_showstate_blocked(int key)
292{
293 show_state_filter(TASK_UNINTERRUPTIBLE);
294}
295static struct sysrq_key_op sysrq_showstate_blocked_op = {
296 .handler = sysrq_handle_showstate_blocked,
297 .help_msg = "show-blocked-tasks(w)",
298 .action_msg = "Show Blocked State",
299 .enable_mask = SYSRQ_ENABLE_DUMP,
300};
301
302#ifdef CONFIG_TRACING
303#include <linux/ftrace.h>
304
305static void sysrq_ftrace_dump(int key)
306{
307 ftrace_dump(DUMP_ALL);
308}
309static struct sysrq_key_op sysrq_ftrace_dump_op = {
310 .handler = sysrq_ftrace_dump,
311 .help_msg = "dump-ftrace-buffer(z)",
312 .action_msg = "Dump ftrace buffer",
313 .enable_mask = SYSRQ_ENABLE_DUMP,
314};
315#else
316#define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
317#endif
318
319static void sysrq_handle_showmem(int key)
320{
321 show_mem(0, NULL);
322}
323static struct sysrq_key_op sysrq_showmem_op = {
324 .handler = sysrq_handle_showmem,
325 .help_msg = "show-memory-usage(m)",
326 .action_msg = "Show Memory",
327 .enable_mask = SYSRQ_ENABLE_DUMP,
328};
329
330/*
331 * Signal sysrq helper function. Sends a signal to all user processes.
332 */
333static void send_sig_all(int sig)
334{
335 struct task_struct *p;
336
337 read_lock(&tasklist_lock);
338 for_each_process(p) {
339 if (p->flags & PF_KTHREAD)
340 continue;
341 if (is_global_init(p))
342 continue;
343
344 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
345 }
346 read_unlock(&tasklist_lock);
347}
348
349static void sysrq_handle_term(int key)
350{
351 send_sig_all(SIGTERM);
352 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
353}
354static struct sysrq_key_op sysrq_term_op = {
355 .handler = sysrq_handle_term,
356 .help_msg = "terminate-all-tasks(e)",
357 .action_msg = "Terminate All Tasks",
358 .enable_mask = SYSRQ_ENABLE_SIGNAL,
359};
360
361static void moom_callback(struct work_struct *ignored)
362{
363 const gfp_t gfp_mask = GFP_KERNEL;
364 struct oom_control oc = {
365 .zonelist = node_zonelist(first_memory_node, gfp_mask),
366 .nodemask = NULL,
367 .memcg = NULL,
368 .gfp_mask = gfp_mask,
369 .order = -1,
370 };
371
372 mutex_lock(&oom_lock);
373 if (!out_of_memory(&oc))
374 pr_info("OOM request ignored. No task eligible\n");
375 mutex_unlock(&oom_lock);
376}
377
378static DECLARE_WORK(moom_work, moom_callback);
379
380static void sysrq_handle_moom(int key)
381{
382 schedule_work(&moom_work);
383}
384static struct sysrq_key_op sysrq_moom_op = {
385 .handler = sysrq_handle_moom,
386 .help_msg = "memory-full-oom-kill(f)",
387 .action_msg = "Manual OOM execution",
388 .enable_mask = SYSRQ_ENABLE_SIGNAL,
389};
390
391#ifdef CONFIG_BLOCK
392static void sysrq_handle_thaw(int key)
393{
394 emergency_thaw_all();
395}
396static struct sysrq_key_op sysrq_thaw_op = {
397 .handler = sysrq_handle_thaw,
398 .help_msg = "thaw-filesystems(j)",
399 .action_msg = "Emergency Thaw of all frozen filesystems",
400 .enable_mask = SYSRQ_ENABLE_SIGNAL,
401};
402#endif
403
404static void sysrq_handle_kill(int key)
405{
406 send_sig_all(SIGKILL);
407 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
408}
409static struct sysrq_key_op sysrq_kill_op = {
410 .handler = sysrq_handle_kill,
411 .help_msg = "kill-all-tasks(i)",
412 .action_msg = "Kill All Tasks",
413 .enable_mask = SYSRQ_ENABLE_SIGNAL,
414};
415
416static void sysrq_handle_unrt(int key)
417{
418 normalize_rt_tasks();
419}
420static struct sysrq_key_op sysrq_unrt_op = {
421 .handler = sysrq_handle_unrt,
422 .help_msg = "nice-all-RT-tasks(n)",
423 .action_msg = "Nice All RT Tasks",
424 .enable_mask = SYSRQ_ENABLE_RTNICE,
425};
426
427/* Key Operations table and lock */
428static DEFINE_SPINLOCK(sysrq_key_table_lock);
429
430static struct sysrq_key_op *sysrq_key_table[36] = {
431 &sysrq_loglevel_op, /* 0 */
432 &sysrq_loglevel_op, /* 1 */
433 &sysrq_loglevel_op, /* 2 */
434 &sysrq_loglevel_op, /* 3 */
435 &sysrq_loglevel_op, /* 4 */
436 &sysrq_loglevel_op, /* 5 */
437 &sysrq_loglevel_op, /* 6 */
438 &sysrq_loglevel_op, /* 7 */
439 &sysrq_loglevel_op, /* 8 */
440 &sysrq_loglevel_op, /* 9 */
441
442 /*
443 * a: Don't use for system provided sysrqs, it is handled specially on
444 * sparc and will never arrive.
445 */
446 NULL, /* a */
447 &sysrq_reboot_op, /* b */
448 &sysrq_crash_op, /* c */
449 &sysrq_showlocks_op, /* d */
450 &sysrq_term_op, /* e */
451 &sysrq_moom_op, /* f */
452 /* g: May be registered for the kernel debugger */
453 NULL, /* g */
454 NULL, /* h - reserved for help */
455 &sysrq_kill_op, /* i */
456#ifdef CONFIG_BLOCK
457 &sysrq_thaw_op, /* j */
458#else
459 NULL, /* j */
460#endif
461 &sysrq_SAK_op, /* k */
462#ifdef CONFIG_SMP
463 &sysrq_showallcpus_op, /* l */
464#else
465 NULL, /* l */
466#endif
467 &sysrq_showmem_op, /* m */
468 &sysrq_unrt_op, /* n */
469 /* o: This will often be registered as 'Off' at init time */
470 NULL, /* o */
471 &sysrq_showregs_op, /* p */
472 &sysrq_show_timers_op, /* q */
473 &sysrq_unraw_op, /* r */
474 &sysrq_sync_op, /* s */
475 &sysrq_showstate_op, /* t */
476 &sysrq_mountro_op, /* u */
477 /* v: May be registered for frame buffer console restore */
478 NULL, /* v */
479 &sysrq_showstate_blocked_op, /* w */
480 /* x: May be registered on mips for TLB dump */
481 /* x: May be registered on ppc/powerpc for xmon */
482 /* x: May be registered on sparc64 for global PMU dump */
483 NULL, /* x */
484 /* y: May be registered on sparc64 for global register dump */
485 NULL, /* y */
486 &sysrq_ftrace_dump_op, /* z */
487};
488
489/* key2index calculation, -1 on invalid index */
490static int sysrq_key_table_key2index(int key)
491{
492 int retval;
493
494 if ((key >= '0') && (key <= '9'))
495 retval = key - '0';
496 else if ((key >= 'a') && (key <= 'z'))
497 retval = key + 10 - 'a';
498 else
499 retval = -1;
500 return retval;
501}
502
503/*
504 * get and put functions for the table, exposed to modules.
505 */
506struct sysrq_key_op *__sysrq_get_key_op(int key)
507{
508 struct sysrq_key_op *op_p = NULL;
509 int i;
510
511 i = sysrq_key_table_key2index(key);
512 if (i != -1)
513 op_p = sysrq_key_table[i];
514
515 return op_p;
516}
517
518static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
519{
520 int i = sysrq_key_table_key2index(key);
521
522 if (i != -1)
523 sysrq_key_table[i] = op_p;
524}
525
526void __handle_sysrq(int key, bool check_mask)
527{
528 struct sysrq_key_op *op_p;
529 int orig_log_level;
530 int i;
531
532 rcu_sysrq_start();
533 rcu_read_lock();
534 /*
535 * Raise the apparent loglevel to maximum so that the sysrq header
536 * is shown to provide the user with positive feedback. We do not
537 * simply emit this at KERN_EMERG as that would change message
538 * routing in the consumers of /proc/kmsg.
539 */
540 orig_log_level = console_loglevel;
541 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
542
543 op_p = __sysrq_get_key_op(key);
544 if (op_p) {
545 /*
546 * Should we check for enabled operations (/proc/sysrq-trigger
547 * should not) and is the invoked operation enabled?
548 */
549 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
550 pr_info("%s\n", op_p->action_msg);
551 console_loglevel = orig_log_level;
552 op_p->handler(key);
553 } else {
554 pr_info("This sysrq operation is disabled.\n");
555 console_loglevel = orig_log_level;
556 }
557 } else {
558 pr_info("HELP : ");
559 /* Only print the help msg once per handler */
560 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
561 if (sysrq_key_table[i]) {
562 int j;
563
564 for (j = 0; sysrq_key_table[i] !=
565 sysrq_key_table[j]; j++)
566 ;
567 if (j != i)
568 continue;
569 pr_cont("%s ", sysrq_key_table[i]->help_msg);
570 }
571 }
572 pr_cont("\n");
573 console_loglevel = orig_log_level;
574 }
575 rcu_read_unlock();
576 rcu_sysrq_end();
577}
578
579void handle_sysrq(int key)
580{
581 if (sysrq_on())
582 __handle_sysrq(key, true);
583}
584EXPORT_SYMBOL(handle_sysrq);
585
586#ifdef CONFIG_INPUT
587static int sysrq_reset_downtime_ms;
588
589/* Simple translation table for the SysRq keys */
590static const unsigned char sysrq_xlate[KEY_CNT] =
591 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
592 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
593 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
594 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
595 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
596 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
597 "\r\000/"; /* 0x60 - 0x6f */
598
599struct sysrq_state {
600 struct input_handle handle;
601 struct work_struct reinject_work;
602 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
603 unsigned int alt;
604 unsigned int alt_use;
605 bool active;
606 bool need_reinject;
607 bool reinjecting;
608
609 /* reset sequence handling */
610 bool reset_canceled;
611 bool reset_requested;
612 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
613 int reset_seq_len;
614 int reset_seq_cnt;
615 int reset_seq_version;
616 struct timer_list keyreset_timer;
617};
618
619#define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
620static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
621static unsigned int sysrq_reset_seq_len;
622static unsigned int sysrq_reset_seq_version = 1;
623
624static void sysrq_parse_reset_sequence(struct sysrq_state *state)
625{
626 int i;
627 unsigned short key;
628
629 state->reset_seq_cnt = 0;
630
631 for (i = 0; i < sysrq_reset_seq_len; i++) {
632 key = sysrq_reset_seq[i];
633
634 if (key == KEY_RESERVED || key > KEY_MAX)
635 break;
636
637 __set_bit(key, state->reset_keybit);
638 state->reset_seq_len++;
639
640 if (test_bit(key, state->key_down))
641 state->reset_seq_cnt++;
642 }
643
644 /* Disable reset until old keys are not released */
645 state->reset_canceled = state->reset_seq_cnt != 0;
646
647 state->reset_seq_version = sysrq_reset_seq_version;
648}
649
650static void sysrq_do_reset(struct timer_list *t)
651{
652 struct sysrq_state *state = from_timer(state, t, keyreset_timer);
653
654 state->reset_requested = true;
655
656 orderly_reboot();
657}
658
659static void sysrq_handle_reset_request(struct sysrq_state *state)
660{
661 if (state->reset_requested)
662 __handle_sysrq(sysrq_xlate[KEY_B], false);
663
664 if (sysrq_reset_downtime_ms)
665 mod_timer(&state->keyreset_timer,
666 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
667 else
668 sysrq_do_reset(&state->keyreset_timer);
669}
670
671static void sysrq_detect_reset_sequence(struct sysrq_state *state,
672 unsigned int code, int value)
673{
674 if (!test_bit(code, state->reset_keybit)) {
675 /*
676 * Pressing any key _not_ in reset sequence cancels
677 * the reset sequence. Also cancelling the timer in
678 * case additional keys were pressed after a reset
679 * has been requested.
680 */
681 if (value && state->reset_seq_cnt) {
682 state->reset_canceled = true;
683 del_timer(&state->keyreset_timer);
684 }
685 } else if (value == 0) {
686 /*
687 * Key release - all keys in the reset sequence need
688 * to be pressed and held for the reset timeout
689 * to hold.
690 */
691 del_timer(&state->keyreset_timer);
692
693 if (--state->reset_seq_cnt == 0)
694 state->reset_canceled = false;
695 } else if (value == 1) {
696 /* key press, not autorepeat */
697 if (++state->reset_seq_cnt == state->reset_seq_len &&
698 !state->reset_canceled) {
699 sysrq_handle_reset_request(state);
700 }
701 }
702}
703
704#ifdef CONFIG_OF
705static void sysrq_of_get_keyreset_config(void)
706{
707 u32 key;
708 struct device_node *np;
709 struct property *prop;
710 const __be32 *p;
711
712 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
713 if (!np) {
714 pr_debug("No sysrq node found");
715 return;
716 }
717
718 /* Reset in case a __weak definition was present */
719 sysrq_reset_seq_len = 0;
720
721 of_property_for_each_u32(np, "keyset", prop, p, key) {
722 if (key == KEY_RESERVED || key > KEY_MAX ||
723 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
724 break;
725
726 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
727 }
728
729 /* Get reset timeout if any. */
730 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
731
732 of_node_put(np);
733}
734#else
735static void sysrq_of_get_keyreset_config(void)
736{
737}
738#endif
739
740static void sysrq_reinject_alt_sysrq(struct work_struct *work)
741{
742 struct sysrq_state *sysrq =
743 container_of(work, struct sysrq_state, reinject_work);
744 struct input_handle *handle = &sysrq->handle;
745 unsigned int alt_code = sysrq->alt_use;
746
747 if (sysrq->need_reinject) {
748 /* we do not want the assignment to be reordered */
749 sysrq->reinjecting = true;
750 mb();
751
752 /* Simulate press and release of Alt + SysRq */
753 input_inject_event(handle, EV_KEY, alt_code, 1);
754 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
755 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
756
757 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
758 input_inject_event(handle, EV_KEY, alt_code, 0);
759 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
760
761 mb();
762 sysrq->reinjecting = false;
763 }
764}
765
766static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
767 unsigned int code, int value)
768{
769 bool was_active = sysrq->active;
770 bool suppress;
771
772 switch (code) {
773
774 case KEY_LEFTALT:
775 case KEY_RIGHTALT:
776 if (!value) {
777 /* One of ALTs is being released */
778 if (sysrq->active && code == sysrq->alt_use)
779 sysrq->active = false;
780
781 sysrq->alt = KEY_RESERVED;
782
783 } else if (value != 2) {
784 sysrq->alt = code;
785 sysrq->need_reinject = false;
786 }
787 break;
788
789 case KEY_SYSRQ:
790 if (value == 1 && sysrq->alt != KEY_RESERVED) {
791 sysrq->active = true;
792 sysrq->alt_use = sysrq->alt;
793 /*
794 * If nothing else will be pressed we'll need
795 * to re-inject Alt-SysRq keysroke.
796 */
797 sysrq->need_reinject = true;
798 }
799
800 /*
801 * Pretend that sysrq was never pressed at all. This
802 * is needed to properly handle KGDB which will try
803 * to release all keys after exiting debugger. If we
804 * do not clear key bit it KGDB will end up sending
805 * release events for Alt and SysRq, potentially
806 * triggering print screen function.
807 */
808 if (sysrq->active)
809 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
810
811 break;
812
813 default:
814 if (sysrq->active && value && value != 2) {
815 sysrq->need_reinject = false;
816 __handle_sysrq(sysrq_xlate[code], true);
817 }
818 break;
819 }
820
821 suppress = sysrq->active;
822
823 if (!sysrq->active) {
824
825 /*
826 * See if reset sequence has changed since the last time.
827 */
828 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
829 sysrq_parse_reset_sequence(sysrq);
830
831 /*
832 * If we are not suppressing key presses keep track of
833 * keyboard state so we can release keys that have been
834 * pressed before entering SysRq mode.
835 */
836 if (value)
837 set_bit(code, sysrq->key_down);
838 else
839 clear_bit(code, sysrq->key_down);
840
841 if (was_active)
842 schedule_work(&sysrq->reinject_work);
843
844 /* Check for reset sequence */
845 sysrq_detect_reset_sequence(sysrq, code, value);
846
847 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
848 /*
849 * Pass on release events for keys that was pressed before
850 * entering SysRq mode.
851 */
852 suppress = false;
853 }
854
855 return suppress;
856}
857
858static bool sysrq_filter(struct input_handle *handle,
859 unsigned int type, unsigned int code, int value)
860{
861 struct sysrq_state *sysrq = handle->private;
862 bool suppress;
863
864 /*
865 * Do not filter anything if we are in the process of re-injecting
866 * Alt+SysRq combination.
867 */
868 if (sysrq->reinjecting)
869 return false;
870
871 switch (type) {
872
873 case EV_SYN:
874 suppress = false;
875 break;
876
877 case EV_KEY:
878 suppress = sysrq_handle_keypress(sysrq, code, value);
879 break;
880
881 default:
882 suppress = sysrq->active;
883 break;
884 }
885
886 return suppress;
887}
888
889static int sysrq_connect(struct input_handler *handler,
890 struct input_dev *dev,
891 const struct input_device_id *id)
892{
893 struct sysrq_state *sysrq;
894 int error;
895
896 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
897 if (!sysrq)
898 return -ENOMEM;
899
900 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
901
902 sysrq->handle.dev = dev;
903 sysrq->handle.handler = handler;
904 sysrq->handle.name = "sysrq";
905 sysrq->handle.private = sysrq;
906 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
907
908 error = input_register_handle(&sysrq->handle);
909 if (error) {
910 pr_err("Failed to register input sysrq handler, error %d\n",
911 error);
912 goto err_free;
913 }
914
915 error = input_open_device(&sysrq->handle);
916 if (error) {
917 pr_err("Failed to open input device, error %d\n", error);
918 goto err_unregister;
919 }
920
921 return 0;
922
923 err_unregister:
924 input_unregister_handle(&sysrq->handle);
925 err_free:
926 kfree(sysrq);
927 return error;
928}
929
930static void sysrq_disconnect(struct input_handle *handle)
931{
932 struct sysrq_state *sysrq = handle->private;
933
934 input_close_device(handle);
935 cancel_work_sync(&sysrq->reinject_work);
936 del_timer_sync(&sysrq->keyreset_timer);
937 input_unregister_handle(handle);
938 kfree(sysrq);
939}
940
941/*
942 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
943 * keyboards have SysRq key predefined and so user may add it to keymap
944 * later, but we expect all such keyboards to have left alt.
945 */
946static const struct input_device_id sysrq_ids[] = {
947 {
948 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
949 INPUT_DEVICE_ID_MATCH_KEYBIT,
950 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
951 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
952 },
953 { },
954};
955
956static struct input_handler sysrq_handler = {
957 .filter = sysrq_filter,
958 .connect = sysrq_connect,
959 .disconnect = sysrq_disconnect,
960 .name = "sysrq",
961 .id_table = sysrq_ids,
962};
963
964static bool sysrq_handler_registered;
965
966static inline void sysrq_register_handler(void)
967{
968 int error;
969
970 sysrq_of_get_keyreset_config();
971
972 error = input_register_handler(&sysrq_handler);
973 if (error)
974 pr_err("Failed to register input handler, error %d", error);
975 else
976 sysrq_handler_registered = true;
977}
978
979static inline void sysrq_unregister_handler(void)
980{
981 if (sysrq_handler_registered) {
982 input_unregister_handler(&sysrq_handler);
983 sysrq_handler_registered = false;
984 }
985}
986
987static int sysrq_reset_seq_param_set(const char *buffer,
988 const struct kernel_param *kp)
989{
990 unsigned long val;
991 int error;
992
993 error = kstrtoul(buffer, 0, &val);
994 if (error < 0)
995 return error;
996
997 if (val > KEY_MAX)
998 return -EINVAL;
999
1000 *((unsigned short *)kp->arg) = val;
1001 sysrq_reset_seq_version++;
1002
1003 return 0;
1004}
1005
1006static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1007 .get = param_get_ushort,
1008 .set = sysrq_reset_seq_param_set,
1009};
1010
1011#define param_check_sysrq_reset_seq(name, p) \
1012 __param_check(name, p, unsigned short)
1013
1014/*
1015 * not really modular, but the easiest way to keep compat with existing
1016 * bootargs behaviour is to continue using module_param here.
1017 */
1018module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1019 &sysrq_reset_seq_len, 0644);
1020
1021module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1022
1023#else
1024
1025static inline void sysrq_register_handler(void)
1026{
1027}
1028
1029static inline void sysrq_unregister_handler(void)
1030{
1031}
1032
1033#endif /* CONFIG_INPUT */
1034
1035int sysrq_toggle_support(int enable_mask)
1036{
1037 bool was_enabled = sysrq_on();
1038
1039 sysrq_enabled = enable_mask;
1040
1041 if (was_enabled != sysrq_on()) {
1042 if (sysrq_on())
1043 sysrq_register_handler();
1044 else
1045 sysrq_unregister_handler();
1046 }
1047
1048 return 0;
1049}
1050
1051static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1052 struct sysrq_key_op *remove_op_p)
1053{
1054 int retval;
1055
1056 spin_lock(&sysrq_key_table_lock);
1057 if (__sysrq_get_key_op(key) == remove_op_p) {
1058 __sysrq_put_key_op(key, insert_op_p);
1059 retval = 0;
1060 } else {
1061 retval = -1;
1062 }
1063 spin_unlock(&sysrq_key_table_lock);
1064
1065 /*
1066 * A concurrent __handle_sysrq either got the old op or the new op.
1067 * Wait for it to go away before returning, so the code for an old
1068 * op is not freed (eg. on module unload) while it is in use.
1069 */
1070 synchronize_rcu();
1071
1072 return retval;
1073}
1074
1075int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1076{
1077 return __sysrq_swap_key_ops(key, op_p, NULL);
1078}
1079EXPORT_SYMBOL(register_sysrq_key);
1080
1081int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1082{
1083 return __sysrq_swap_key_ops(key, NULL, op_p);
1084}
1085EXPORT_SYMBOL(unregister_sysrq_key);
1086
1087#ifdef CONFIG_PROC_FS
1088/*
1089 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1090 */
1091static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1092 size_t count, loff_t *ppos)
1093{
1094 if (count) {
1095 char c;
1096
1097 if (get_user(c, buf))
1098 return -EFAULT;
1099 __handle_sysrq(c, false);
1100 }
1101
1102 return count;
1103}
1104
1105static const struct file_operations proc_sysrq_trigger_operations = {
1106 .write = write_sysrq_trigger,
1107 .llseek = noop_llseek,
1108};
1109
1110static void sysrq_init_procfs(void)
1111{
1112 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1113 &proc_sysrq_trigger_operations))
1114 pr_err("Failed to register proc interface\n");
1115}
1116
1117#else
1118
1119static inline void sysrq_init_procfs(void)
1120{
1121}
1122
1123#endif /* CONFIG_PROC_FS */
1124
1125static int __init sysrq_init(void)
1126{
1127 sysrq_init_procfs();
1128
1129 if (sysrq_on())
1130 sysrq_register_handler();
1131
1132 return 0;
1133}
1134device_initcall(sysrq_init);
1135