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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 */
59static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
60static bool __read_mostly sysrq_always_enabled;
61
62static 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 */
72int sysrq_mask(void)
73{
74 if (sysrq_always_enabled)
75 return 1;
76 return sysrq_enabled;
77}
78EXPORT_SYMBOL_GPL(sysrq_mask);
79
80/*
81 * A value of 1 means 'all', other nonzero values are an op mask:
82 */
83static bool sysrq_on_mask(int mask)
84{
85 return sysrq_always_enabled ||
86 sysrq_enabled == 1 ||
87 (sysrq_enabled & mask);
88}
89
90static 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
101static 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}
109static 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
117static 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}
123static 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
134static void sysrq_handle_unraw(u8 key)
135{
136 vt_reset_unicode(fg_console);
137}
138
139static 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
149static 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}
156static 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
163static void sysrq_handle_reboot(u8 key)
164{
165 lockdep_off();
166 local_irq_enable();
167 emergency_restart();
168}
169static 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
176const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
177
178static void sysrq_handle_sync(u8 key)
179{
180 emergency_sync();
181}
182static 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
189static void sysrq_handle_show_timers(u8 key)
190{
191 sysrq_timer_list_show();
192}
193
194static 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
200static void sysrq_handle_mountro(u8 key)
201{
202 emergency_remount();
203}
204static 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
212static void sysrq_handle_showlocks(u8 key)
213{
214 debug_show_all_locks();
215}
216
217static 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
227static DEFINE_RAW_SPINLOCK(show_lock);
228
229static 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
245static void sysrq_showregs_othercpus(struct work_struct *dummy)
246{
247 smp_call_function(showacpu, NULL, 0);
248}
249
250static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
251
252static 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", get_cpu());
266 if (regs)
267 show_regs(regs);
268 else
269 show_stack(NULL, NULL, KERN_INFO);
270
271 schedule_work(&sysrq_showallcpus);
272 put_cpu();
273 }
274}
275
276static 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,
281};
282#else
283#define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL)
284#endif
285
286static void sysrq_handle_showregs(u8 key)
287{
288 struct pt_regs *regs = NULL;
289
290 if (in_hardirq())
291 regs = get_irq_regs();
292 if (regs)
293 show_regs(regs);
294 perf_event_print_debug();
295}
296static const struct sysrq_key_op sysrq_showregs_op = {
297 .handler = sysrq_handle_showregs,
298 .help_msg = "show-registers(p)",
299 .action_msg = "Show Regs",
300 .enable_mask = SYSRQ_ENABLE_DUMP,
301};
302
303static void sysrq_handle_showstate(u8 key)
304{
305 show_state();
306 show_all_workqueues();
307}
308static const struct sysrq_key_op sysrq_showstate_op = {
309 .handler = sysrq_handle_showstate,
310 .help_msg = "show-task-states(t)",
311 .action_msg = "Show State",
312 .enable_mask = SYSRQ_ENABLE_DUMP,
313};
314
315static void sysrq_handle_showstate_blocked(u8 key)
316{
317 show_state_filter(TASK_UNINTERRUPTIBLE);
318}
319static const struct sysrq_key_op sysrq_showstate_blocked_op = {
320 .handler = sysrq_handle_showstate_blocked,
321 .help_msg = "show-blocked-tasks(w)",
322 .action_msg = "Show Blocked State",
323 .enable_mask = SYSRQ_ENABLE_DUMP,
324};
325
326#ifdef CONFIG_TRACING
327#include <linux/ftrace.h>
328
329static void sysrq_ftrace_dump(u8 key)
330{
331 ftrace_dump(DUMP_ALL);
332}
333static const struct sysrq_key_op sysrq_ftrace_dump_op = {
334 .handler = sysrq_ftrace_dump,
335 .help_msg = "dump-ftrace-buffer(z)",
336 .action_msg = "Dump ftrace buffer",
337 .enable_mask = SYSRQ_ENABLE_DUMP,
338};
339#else
340#define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
341#endif
342
343static void sysrq_handle_showmem(u8 key)
344{
345 show_mem();
346}
347static const struct sysrq_key_op sysrq_showmem_op = {
348 .handler = sysrq_handle_showmem,
349 .help_msg = "show-memory-usage(m)",
350 .action_msg = "Show Memory",
351 .enable_mask = SYSRQ_ENABLE_DUMP,
352};
353
354/*
355 * Signal sysrq helper function. Sends a signal to all user processes.
356 */
357static void send_sig_all(int sig)
358{
359 struct task_struct *p;
360
361 read_lock(&tasklist_lock);
362 for_each_process(p) {
363 if (p->flags & PF_KTHREAD)
364 continue;
365 if (is_global_init(p))
366 continue;
367
368 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
369 }
370 read_unlock(&tasklist_lock);
371}
372
373static void sysrq_handle_term(u8 key)
374{
375 send_sig_all(SIGTERM);
376 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
377}
378static const struct sysrq_key_op sysrq_term_op = {
379 .handler = sysrq_handle_term,
380 .help_msg = "terminate-all-tasks(e)",
381 .action_msg = "Terminate All Tasks",
382 .enable_mask = SYSRQ_ENABLE_SIGNAL,
383};
384
385static void moom_callback(struct work_struct *ignored)
386{
387 const gfp_t gfp_mask = GFP_KERNEL;
388 struct oom_control oc = {
389 .zonelist = node_zonelist(first_memory_node, gfp_mask),
390 .nodemask = NULL,
391 .memcg = NULL,
392 .gfp_mask = gfp_mask,
393 .order = -1,
394 };
395
396 mutex_lock(&oom_lock);
397 if (!out_of_memory(&oc))
398 pr_info("OOM request ignored. No task eligible\n");
399 mutex_unlock(&oom_lock);
400}
401
402static DECLARE_WORK(moom_work, moom_callback);
403
404static void sysrq_handle_moom(u8 key)
405{
406 schedule_work(&moom_work);
407}
408static const struct sysrq_key_op sysrq_moom_op = {
409 .handler = sysrq_handle_moom,
410 .help_msg = "memory-full-oom-kill(f)",
411 .action_msg = "Manual OOM execution",
412 .enable_mask = SYSRQ_ENABLE_SIGNAL,
413};
414
415#ifdef CONFIG_BLOCK
416static void sysrq_handle_thaw(u8 key)
417{
418 emergency_thaw_all();
419}
420static const struct sysrq_key_op sysrq_thaw_op = {
421 .handler = sysrq_handle_thaw,
422 .help_msg = "thaw-filesystems(j)",
423 .action_msg = "Emergency Thaw of all frozen filesystems",
424 .enable_mask = SYSRQ_ENABLE_SIGNAL,
425};
426#else
427#define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL)
428#endif
429
430static void sysrq_handle_kill(u8 key)
431{
432 send_sig_all(SIGKILL);
433 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
434}
435static const struct sysrq_key_op sysrq_kill_op = {
436 .handler = sysrq_handle_kill,
437 .help_msg = "kill-all-tasks(i)",
438 .action_msg = "Kill All Tasks",
439 .enable_mask = SYSRQ_ENABLE_SIGNAL,
440};
441
442static void sysrq_handle_unrt(u8 key)
443{
444 normalize_rt_tasks();
445}
446static const struct sysrq_key_op sysrq_unrt_op = {
447 .handler = sysrq_handle_unrt,
448 .help_msg = "nice-all-RT-tasks(n)",
449 .action_msg = "Nice All RT Tasks",
450 .enable_mask = SYSRQ_ENABLE_RTNICE,
451};
452
453/* Key Operations table and lock */
454static DEFINE_SPINLOCK(sysrq_key_table_lock);
455
456static const struct sysrq_key_op *sysrq_key_table[62] = {
457 &sysrq_loglevel_op, /* 0 */
458 &sysrq_loglevel_op, /* 1 */
459 &sysrq_loglevel_op, /* 2 */
460 &sysrq_loglevel_op, /* 3 */
461 &sysrq_loglevel_op, /* 4 */
462 &sysrq_loglevel_op, /* 5 */
463 &sysrq_loglevel_op, /* 6 */
464 &sysrq_loglevel_op, /* 7 */
465 &sysrq_loglevel_op, /* 8 */
466 &sysrq_loglevel_op, /* 9 */
467
468 /*
469 * a: Don't use for system provided sysrqs, it is handled specially on
470 * sparc and will never arrive.
471 */
472 NULL, /* a */
473 &sysrq_reboot_op, /* b */
474 &sysrq_crash_op, /* c */
475 &sysrq_showlocks_op, /* d */
476 &sysrq_term_op, /* e */
477 &sysrq_moom_op, /* f */
478 /* g: May be registered for the kernel debugger */
479 NULL, /* g */
480 NULL, /* h - reserved for help */
481 &sysrq_kill_op, /* i */
482 &sysrq_thaw_op, /* j */
483 &sysrq_SAK_op, /* k */
484 &sysrq_showallcpus_op, /* l */
485 &sysrq_showmem_op, /* m */
486 &sysrq_unrt_op, /* n */
487 /* o: This will often be registered as 'Off' at init time */
488 NULL, /* o */
489 &sysrq_showregs_op, /* p */
490 &sysrq_show_timers_op, /* q */
491 &sysrq_unraw_op, /* r */
492 &sysrq_sync_op, /* s */
493 &sysrq_showstate_op, /* t */
494 &sysrq_mountro_op, /* u */
495 /* v: May be registered for frame buffer console restore */
496 NULL, /* v */
497 &sysrq_showstate_blocked_op, /* w */
498 /* x: May be registered on mips for TLB dump */
499 /* x: May be registered on ppc/powerpc for xmon */
500 /* x: May be registered on sparc64 for global PMU dump */
501 NULL, /* x */
502 /* y: May be registered on sparc64 for global register dump */
503 NULL, /* y */
504 &sysrq_ftrace_dump_op, /* z */
505 NULL, /* A */
506 NULL, /* B */
507 NULL, /* C */
508 NULL, /* D */
509 NULL, /* E */
510 NULL, /* F */
511 NULL, /* G */
512 NULL, /* H */
513 NULL, /* I */
514 NULL, /* J */
515 NULL, /* K */
516 NULL, /* L */
517 NULL, /* M */
518 NULL, /* N */
519 NULL, /* O */
520 NULL, /* P */
521 NULL, /* Q */
522 NULL, /* R */
523 NULL, /* S */
524 NULL, /* T */
525 NULL, /* U */
526 NULL, /* V */
527 NULL, /* W */
528 NULL, /* X */
529 NULL, /* Y */
530 NULL, /* Z */
531};
532
533/* key2index calculation, -1 on invalid index */
534static int sysrq_key_table_key2index(u8 key)
535{
536 switch (key) {
537 case '0' ... '9':
538 return key - '0';
539 case 'a' ... 'z':
540 return key - 'a' + 10;
541 case 'A' ... 'Z':
542 return key - 'A' + 10 + 26;
543 default:
544 return -1;
545 }
546}
547
548/*
549 * get and put functions for the table, exposed to modules.
550 */
551static const struct sysrq_key_op *__sysrq_get_key_op(u8 key)
552{
553 const struct sysrq_key_op *op_p = NULL;
554 int i;
555
556 i = sysrq_key_table_key2index(key);
557 if (i != -1)
558 op_p = sysrq_key_table[i];
559
560 return op_p;
561}
562
563static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p)
564{
565 int i = sysrq_key_table_key2index(key);
566
567 if (i != -1)
568 sysrq_key_table[i] = op_p;
569}
570
571void __handle_sysrq(u8 key, bool check_mask)
572{
573 const struct sysrq_key_op *op_p;
574 int orig_log_level;
575 int orig_suppress_printk;
576 int i;
577
578 orig_suppress_printk = suppress_printk;
579 suppress_printk = 0;
580
581 rcu_sysrq_start();
582 rcu_read_lock();
583 /*
584 * Raise the apparent loglevel to maximum so that the sysrq header
585 * is shown to provide the user with positive feedback. We do not
586 * simply emit this at KERN_EMERG as that would change message
587 * routing in the consumers of /proc/kmsg.
588 */
589 orig_log_level = console_loglevel;
590 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
591
592 op_p = __sysrq_get_key_op(key);
593 if (op_p) {
594 /*
595 * Should we check for enabled operations (/proc/sysrq-trigger
596 * should not) and is the invoked operation enabled?
597 */
598 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
599 pr_info("%s\n", op_p->action_msg);
600 console_loglevel = orig_log_level;
601 op_p->handler(key);
602 } else {
603 pr_info("This sysrq operation is disabled.\n");
604 console_loglevel = orig_log_level;
605 }
606 } else {
607 pr_info("HELP : ");
608 /* Only print the help msg once per handler */
609 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
610 if (sysrq_key_table[i]) {
611 int j;
612
613 for (j = 0; sysrq_key_table[i] !=
614 sysrq_key_table[j]; j++)
615 ;
616 if (j != i)
617 continue;
618 pr_cont("%s ", sysrq_key_table[i]->help_msg);
619 }
620 }
621 pr_cont("\n");
622 console_loglevel = orig_log_level;
623 }
624 rcu_read_unlock();
625 rcu_sysrq_end();
626
627 suppress_printk = orig_suppress_printk;
628}
629
630void handle_sysrq(u8 key)
631{
632 if (sysrq_on())
633 __handle_sysrq(key, true);
634}
635EXPORT_SYMBOL(handle_sysrq);
636
637#ifdef CONFIG_INPUT
638static int sysrq_reset_downtime_ms;
639
640/* Simple translation table for the SysRq keys */
641static const unsigned char sysrq_xlate[KEY_CNT] =
642 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
643 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
644 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
645 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
646 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
647 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
648 "\r\000/"; /* 0x60 - 0x6f */
649
650struct sysrq_state {
651 struct input_handle handle;
652 struct work_struct reinject_work;
653 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
654 unsigned int alt;
655 unsigned int alt_use;
656 unsigned int shift;
657 unsigned int shift_use;
658 bool active;
659 bool need_reinject;
660 bool reinjecting;
661
662 /* reset sequence handling */
663 bool reset_canceled;
664 bool reset_requested;
665 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
666 int reset_seq_len;
667 int reset_seq_cnt;
668 int reset_seq_version;
669 struct timer_list keyreset_timer;
670};
671
672#define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
673static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
674static unsigned int sysrq_reset_seq_len;
675static unsigned int sysrq_reset_seq_version = 1;
676
677static void sysrq_parse_reset_sequence(struct sysrq_state *state)
678{
679 int i;
680 unsigned short key;
681
682 state->reset_seq_cnt = 0;
683
684 for (i = 0; i < sysrq_reset_seq_len; i++) {
685 key = sysrq_reset_seq[i];
686
687 if (key == KEY_RESERVED || key > KEY_MAX)
688 break;
689
690 __set_bit(key, state->reset_keybit);
691 state->reset_seq_len++;
692
693 if (test_bit(key, state->key_down))
694 state->reset_seq_cnt++;
695 }
696
697 /* Disable reset until old keys are not released */
698 state->reset_canceled = state->reset_seq_cnt != 0;
699
700 state->reset_seq_version = sysrq_reset_seq_version;
701}
702
703static void sysrq_do_reset(struct timer_list *t)
704{
705 struct sysrq_state *state = from_timer(state, t, keyreset_timer);
706
707 state->reset_requested = true;
708
709 orderly_reboot();
710}
711
712static void sysrq_handle_reset_request(struct sysrq_state *state)
713{
714 if (state->reset_requested)
715 __handle_sysrq(sysrq_xlate[KEY_B], false);
716
717 if (sysrq_reset_downtime_ms)
718 mod_timer(&state->keyreset_timer,
719 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
720 else
721 sysrq_do_reset(&state->keyreset_timer);
722}
723
724static void sysrq_detect_reset_sequence(struct sysrq_state *state,
725 unsigned int code, int value)
726{
727 if (!test_bit(code, state->reset_keybit)) {
728 /*
729 * Pressing any key _not_ in reset sequence cancels
730 * the reset sequence. Also cancelling the timer in
731 * case additional keys were pressed after a reset
732 * has been requested.
733 */
734 if (value && state->reset_seq_cnt) {
735 state->reset_canceled = true;
736 del_timer(&state->keyreset_timer);
737 }
738 } else if (value == 0) {
739 /*
740 * Key release - all keys in the reset sequence need
741 * to be pressed and held for the reset timeout
742 * to hold.
743 */
744 del_timer(&state->keyreset_timer);
745
746 if (--state->reset_seq_cnt == 0)
747 state->reset_canceled = false;
748 } else if (value == 1) {
749 /* key press, not autorepeat */
750 if (++state->reset_seq_cnt == state->reset_seq_len &&
751 !state->reset_canceled) {
752 sysrq_handle_reset_request(state);
753 }
754 }
755}
756
757#ifdef CONFIG_OF
758static void sysrq_of_get_keyreset_config(void)
759{
760 u32 key;
761 struct device_node *np;
762 struct property *prop;
763 const __be32 *p;
764
765 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
766 if (!np) {
767 pr_debug("No sysrq node found");
768 return;
769 }
770
771 /* Reset in case a __weak definition was present */
772 sysrq_reset_seq_len = 0;
773
774 of_property_for_each_u32(np, "keyset", prop, p, key) {
775 if (key == KEY_RESERVED || key > KEY_MAX ||
776 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
777 break;
778
779 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
780 }
781
782 /* Get reset timeout if any. */
783 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
784
785 of_node_put(np);
786}
787#else
788static void sysrq_of_get_keyreset_config(void)
789{
790}
791#endif
792
793static void sysrq_reinject_alt_sysrq(struct work_struct *work)
794{
795 struct sysrq_state *sysrq =
796 container_of(work, struct sysrq_state, reinject_work);
797 struct input_handle *handle = &sysrq->handle;
798 unsigned int alt_code = sysrq->alt_use;
799
800 if (sysrq->need_reinject) {
801 /* we do not want the assignment to be reordered */
802 sysrq->reinjecting = true;
803 mb();
804
805 /* Simulate press and release of Alt + SysRq */
806 input_inject_event(handle, EV_KEY, alt_code, 1);
807 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
808 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
809
810 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
811 input_inject_event(handle, EV_KEY, alt_code, 0);
812 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
813
814 mb();
815 sysrq->reinjecting = false;
816 }
817}
818
819static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
820 unsigned int code, int value)
821{
822 bool was_active = sysrq->active;
823 bool suppress;
824
825 switch (code) {
826
827 case KEY_LEFTALT:
828 case KEY_RIGHTALT:
829 if (!value) {
830 /* One of ALTs is being released */
831 if (sysrq->active && code == sysrq->alt_use)
832 sysrq->active = false;
833
834 sysrq->alt = KEY_RESERVED;
835
836 } else if (value != 2) {
837 sysrq->alt = code;
838 sysrq->need_reinject = false;
839 }
840 break;
841
842 case KEY_LEFTSHIFT:
843 case KEY_RIGHTSHIFT:
844 if (!value)
845 sysrq->shift = KEY_RESERVED;
846 else if (value != 2)
847 sysrq->shift = code;
848 if (sysrq->active)
849 sysrq->shift_use = sysrq->shift;
850 break;
851
852 case KEY_SYSRQ:
853 if (value == 1 && sysrq->alt != KEY_RESERVED) {
854 sysrq->active = true;
855 sysrq->alt_use = sysrq->alt;
856 /* either RESERVED (for released) or actual code */
857 sysrq->shift_use = sysrq->shift;
858 /*
859 * If nothing else will be pressed we'll need
860 * to re-inject Alt-SysRq keysroke.
861 */
862 sysrq->need_reinject = true;
863 }
864
865 /*
866 * Pretend that sysrq was never pressed at all. This
867 * is needed to properly handle KGDB which will try
868 * to release all keys after exiting debugger. If we
869 * do not clear key bit it KGDB will end up sending
870 * release events for Alt and SysRq, potentially
871 * triggering print screen function.
872 */
873 if (sysrq->active)
874 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
875
876 break;
877
878 default:
879 if (sysrq->active && value && value != 2) {
880 unsigned char c = sysrq_xlate[code];
881
882 sysrq->need_reinject = false;
883 if (sysrq->shift_use != KEY_RESERVED)
884 c = toupper(c);
885 __handle_sysrq(c, true);
886 }
887 break;
888 }
889
890 suppress = sysrq->active;
891
892 if (!sysrq->active) {
893
894 /*
895 * See if reset sequence has changed since the last time.
896 */
897 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
898 sysrq_parse_reset_sequence(sysrq);
899
900 /*
901 * If we are not suppressing key presses keep track of
902 * keyboard state so we can release keys that have been
903 * pressed before entering SysRq mode.
904 */
905 if (value)
906 set_bit(code, sysrq->key_down);
907 else
908 clear_bit(code, sysrq->key_down);
909
910 if (was_active)
911 schedule_work(&sysrq->reinject_work);
912
913 /* Check for reset sequence */
914 sysrq_detect_reset_sequence(sysrq, code, value);
915
916 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
917 /*
918 * Pass on release events for keys that was pressed before
919 * entering SysRq mode.
920 */
921 suppress = false;
922 }
923
924 return suppress;
925}
926
927static bool sysrq_filter(struct input_handle *handle,
928 unsigned int type, unsigned int code, int value)
929{
930 struct sysrq_state *sysrq = handle->private;
931 bool suppress;
932
933 /*
934 * Do not filter anything if we are in the process of re-injecting
935 * Alt+SysRq combination.
936 */
937 if (sysrq->reinjecting)
938 return false;
939
940 switch (type) {
941
942 case EV_SYN:
943 suppress = false;
944 break;
945
946 case EV_KEY:
947 suppress = sysrq_handle_keypress(sysrq, code, value);
948 break;
949
950 default:
951 suppress = sysrq->active;
952 break;
953 }
954
955 return suppress;
956}
957
958static int sysrq_connect(struct input_handler *handler,
959 struct input_dev *dev,
960 const struct input_device_id *id)
961{
962 struct sysrq_state *sysrq;
963 int error;
964
965 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
966 if (!sysrq)
967 return -ENOMEM;
968
969 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
970
971 sysrq->handle.dev = dev;
972 sysrq->handle.handler = handler;
973 sysrq->handle.name = "sysrq";
974 sysrq->handle.private = sysrq;
975 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
976
977 error = input_register_handle(&sysrq->handle);
978 if (error) {
979 pr_err("Failed to register input sysrq handler, error %d\n",
980 error);
981 goto err_free;
982 }
983
984 error = input_open_device(&sysrq->handle);
985 if (error) {
986 pr_err("Failed to open input device, error %d\n", error);
987 goto err_unregister;
988 }
989
990 return 0;
991
992 err_unregister:
993 input_unregister_handle(&sysrq->handle);
994 err_free:
995 kfree(sysrq);
996 return error;
997}
998
999static void sysrq_disconnect(struct input_handle *handle)
1000{
1001 struct sysrq_state *sysrq = handle->private;
1002
1003 input_close_device(handle);
1004 cancel_work_sync(&sysrq->reinject_work);
1005 timer_shutdown_sync(&sysrq->keyreset_timer);
1006 input_unregister_handle(handle);
1007 kfree(sysrq);
1008}
1009
1010/*
1011 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1012 * keyboards have SysRq key predefined and so user may add it to keymap
1013 * later, but we expect all such keyboards to have left alt.
1014 */
1015static const struct input_device_id sysrq_ids[] = {
1016 {
1017 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1018 INPUT_DEVICE_ID_MATCH_KEYBIT,
1019 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1020 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1021 },
1022 { },
1023};
1024
1025static struct input_handler sysrq_handler = {
1026 .filter = sysrq_filter,
1027 .connect = sysrq_connect,
1028 .disconnect = sysrq_disconnect,
1029 .name = "sysrq",
1030 .id_table = sysrq_ids,
1031};
1032
1033static inline void sysrq_register_handler(void)
1034{
1035 int error;
1036
1037 sysrq_of_get_keyreset_config();
1038
1039 error = input_register_handler(&sysrq_handler);
1040 if (error)
1041 pr_err("Failed to register input handler, error %d", error);
1042}
1043
1044static inline void sysrq_unregister_handler(void)
1045{
1046 input_unregister_handler(&sysrq_handler);
1047}
1048
1049static int sysrq_reset_seq_param_set(const char *buffer,
1050 const struct kernel_param *kp)
1051{
1052 unsigned long val;
1053 int error;
1054
1055 error = kstrtoul(buffer, 0, &val);
1056 if (error < 0)
1057 return error;
1058
1059 if (val > KEY_MAX)
1060 return -EINVAL;
1061
1062 *((unsigned short *)kp->arg) = val;
1063 sysrq_reset_seq_version++;
1064
1065 return 0;
1066}
1067
1068static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1069 .get = param_get_ushort,
1070 .set = sysrq_reset_seq_param_set,
1071};
1072
1073#define param_check_sysrq_reset_seq(name, p) \
1074 __param_check(name, p, unsigned short)
1075
1076/*
1077 * not really modular, but the easiest way to keep compat with existing
1078 * bootargs behaviour is to continue using module_param here.
1079 */
1080module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1081 &sysrq_reset_seq_len, 0644);
1082
1083module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1084
1085#else
1086
1087static inline void sysrq_register_handler(void)
1088{
1089}
1090
1091static inline void sysrq_unregister_handler(void)
1092{
1093}
1094
1095#endif /* CONFIG_INPUT */
1096
1097int sysrq_toggle_support(int enable_mask)
1098{
1099 bool was_enabled = sysrq_on();
1100
1101 sysrq_enabled = enable_mask;
1102
1103 if (was_enabled != sysrq_on()) {
1104 if (sysrq_on())
1105 sysrq_register_handler();
1106 else
1107 sysrq_unregister_handler();
1108 }
1109
1110 return 0;
1111}
1112EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1113
1114static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p,
1115 const struct sysrq_key_op *remove_op_p)
1116{
1117 int retval;
1118
1119 spin_lock(&sysrq_key_table_lock);
1120 if (__sysrq_get_key_op(key) == remove_op_p) {
1121 __sysrq_put_key_op(key, insert_op_p);
1122 retval = 0;
1123 } else {
1124 retval = -1;
1125 }
1126 spin_unlock(&sysrq_key_table_lock);
1127
1128 /*
1129 * A concurrent __handle_sysrq either got the old op or the new op.
1130 * Wait for it to go away before returning, so the code for an old
1131 * op is not freed (eg. on module unload) while it is in use.
1132 */
1133 synchronize_rcu();
1134
1135 return retval;
1136}
1137
1138int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1139{
1140 return __sysrq_swap_key_ops(key, op_p, NULL);
1141}
1142EXPORT_SYMBOL(register_sysrq_key);
1143
1144int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1145{
1146 return __sysrq_swap_key_ops(key, NULL, op_p);
1147}
1148EXPORT_SYMBOL(unregister_sysrq_key);
1149
1150#ifdef CONFIG_PROC_FS
1151/*
1152 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1153 * Normally, only the first character written is processed.
1154 * However, if the first character is an underscore,
1155 * all characters are processed.
1156 */
1157static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1158 size_t count, loff_t *ppos)
1159{
1160 bool bulk = false;
1161 size_t i;
1162
1163 for (i = 0; i < count; i++) {
1164 char c;
1165
1166 if (get_user(c, buf + i))
1167 return -EFAULT;
1168
1169 if (c == '_')
1170 bulk = true;
1171 else
1172 __handle_sysrq(c, false);
1173
1174 if (!bulk)
1175 break;
1176 }
1177
1178 return count;
1179}
1180
1181static const struct proc_ops sysrq_trigger_proc_ops = {
1182 .proc_write = write_sysrq_trigger,
1183 .proc_lseek = noop_llseek,
1184};
1185
1186static void sysrq_init_procfs(void)
1187{
1188 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1189 &sysrq_trigger_proc_ops))
1190 pr_err("Failed to register proc interface\n");
1191}
1192
1193#else
1194
1195static inline void sysrq_init_procfs(void)
1196{
1197}
1198
1199#endif /* CONFIG_PROC_FS */
1200
1201static int __init sysrq_init(void)
1202{
1203 sysrq_init_procfs();
1204
1205 if (sysrq_on())
1206 sysrq_register_handler();
1207
1208 return 0;
1209}
1210device_initcall(sysrq_init);
1/*
2 * Linux Magic System Request Key Hacks
3 *
4 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
5 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
6 *
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
10 *
11 * Copyright (c) 2010 Dmitry Torokhov
12 * Input handler conversion
13 */
14
15#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
16
17#include <linux/sched.h>
18#include <linux/sched/rt.h>
19#include <linux/interrupt.h>
20#include <linux/mm.h>
21#include <linux/fs.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>
46#include <linux/jiffies.h>
47#include <linux/syscalls.h>
48#include <linux/of.h>
49#include <linux/rcupdate.h>
50
51#include <asm/ptrace.h>
52#include <asm/irq_regs.h>
53
54/* Whether we react on sysrq keys or just ignore them */
55static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
56static bool __read_mostly sysrq_always_enabled;
57
58static bool sysrq_on(void)
59{
60 return sysrq_enabled || sysrq_always_enabled;
61}
62
63/*
64 * A value of 1 means 'all', other nonzero values are an op mask:
65 */
66static bool sysrq_on_mask(int mask)
67{
68 return sysrq_always_enabled ||
69 sysrq_enabled == 1 ||
70 (sysrq_enabled & mask);
71}
72
73static int __init sysrq_always_enabled_setup(char *str)
74{
75 sysrq_always_enabled = true;
76 pr_info("sysrq always enabled.\n");
77
78 return 1;
79}
80
81__setup("sysrq_always_enabled", sysrq_always_enabled_setup);
82
83
84static void sysrq_handle_loglevel(int key)
85{
86 int i;
87
88 i = key - '0';
89 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
90 pr_info("Loglevel set to %d\n", i);
91 console_loglevel = i;
92}
93static struct sysrq_key_op sysrq_loglevel_op = {
94 .handler = sysrq_handle_loglevel,
95 .help_msg = "loglevel(0-9)",
96 .action_msg = "Changing Loglevel",
97 .enable_mask = SYSRQ_ENABLE_LOG,
98};
99
100#ifdef CONFIG_VT
101static void sysrq_handle_SAK(int key)
102{
103 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
104 schedule_work(SAK_work);
105}
106static struct sysrq_key_op sysrq_SAK_op = {
107 .handler = sysrq_handle_SAK,
108 .help_msg = "sak(k)",
109 .action_msg = "SAK",
110 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
111};
112#else
113#define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
114#endif
115
116#ifdef CONFIG_VT
117static void sysrq_handle_unraw(int key)
118{
119 vt_reset_unicode(fg_console);
120}
121
122static struct sysrq_key_op sysrq_unraw_op = {
123 .handler = sysrq_handle_unraw,
124 .help_msg = "unraw(r)",
125 .action_msg = "Keyboard mode set to system default",
126 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
127};
128#else
129#define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
130#endif /* CONFIG_VT */
131
132static void sysrq_handle_crash(int key)
133{
134 char *killer = NULL;
135
136 /* we need to release the RCU read lock here,
137 * otherwise we get an annoying
138 * 'BUG: sleeping function called from invalid context'
139 * complaint from the kernel before the panic.
140 */
141 rcu_read_unlock();
142 panic_on_oops = 1; /* force panic */
143 wmb();
144 *killer = 1;
145}
146static struct sysrq_key_op sysrq_crash_op = {
147 .handler = sysrq_handle_crash,
148 .help_msg = "crash(c)",
149 .action_msg = "Trigger a crash",
150 .enable_mask = SYSRQ_ENABLE_DUMP,
151};
152
153static void sysrq_handle_reboot(int key)
154{
155 lockdep_off();
156 local_irq_enable();
157 emergency_restart();
158}
159static struct sysrq_key_op sysrq_reboot_op = {
160 .handler = sysrq_handle_reboot,
161 .help_msg = "reboot(b)",
162 .action_msg = "Resetting",
163 .enable_mask = SYSRQ_ENABLE_BOOT,
164};
165
166static void sysrq_handle_sync(int key)
167{
168 emergency_sync();
169}
170static struct sysrq_key_op sysrq_sync_op = {
171 .handler = sysrq_handle_sync,
172 .help_msg = "sync(s)",
173 .action_msg = "Emergency Sync",
174 .enable_mask = SYSRQ_ENABLE_SYNC,
175};
176
177static void sysrq_handle_show_timers(int key)
178{
179 sysrq_timer_list_show();
180}
181
182static struct sysrq_key_op sysrq_show_timers_op = {
183 .handler = sysrq_handle_show_timers,
184 .help_msg = "show-all-timers(q)",
185 .action_msg = "Show clockevent devices & pending hrtimers (no others)",
186};
187
188static void sysrq_handle_mountro(int key)
189{
190 emergency_remount();
191}
192static struct sysrq_key_op sysrq_mountro_op = {
193 .handler = sysrq_handle_mountro,
194 .help_msg = "unmount(u)",
195 .action_msg = "Emergency Remount R/O",
196 .enable_mask = SYSRQ_ENABLE_REMOUNT,
197};
198
199#ifdef CONFIG_LOCKDEP
200static void sysrq_handle_showlocks(int key)
201{
202 debug_show_all_locks();
203}
204
205static struct sysrq_key_op sysrq_showlocks_op = {
206 .handler = sysrq_handle_showlocks,
207 .help_msg = "show-all-locks(d)",
208 .action_msg = "Show Locks Held",
209};
210#else
211#define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
212#endif
213
214#ifdef CONFIG_SMP
215static DEFINE_SPINLOCK(show_lock);
216
217static void showacpu(void *dummy)
218{
219 unsigned long flags;
220
221 /* Idle CPUs have no interesting backtrace. */
222 if (idle_cpu(smp_processor_id()))
223 return;
224
225 spin_lock_irqsave(&show_lock, flags);
226 pr_info("CPU%d:\n", smp_processor_id());
227 show_stack(NULL, NULL);
228 spin_unlock_irqrestore(&show_lock, flags);
229}
230
231static void sysrq_showregs_othercpus(struct work_struct *dummy)
232{
233 smp_call_function(showacpu, NULL, 0);
234}
235
236static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
237
238static void sysrq_handle_showallcpus(int key)
239{
240 /*
241 * Fall back to the workqueue based printing if the
242 * backtrace printing did not succeed or the
243 * architecture has no support for it:
244 */
245 if (!trigger_all_cpu_backtrace()) {
246 struct pt_regs *regs = get_irq_regs();
247
248 if (regs) {
249 pr_info("CPU%d:\n", smp_processor_id());
250 show_regs(regs);
251 }
252 schedule_work(&sysrq_showallcpus);
253 }
254}
255
256static struct sysrq_key_op sysrq_showallcpus_op = {
257 .handler = sysrq_handle_showallcpus,
258 .help_msg = "show-backtrace-all-active-cpus(l)",
259 .action_msg = "Show backtrace of all active CPUs",
260 .enable_mask = SYSRQ_ENABLE_DUMP,
261};
262#endif
263
264static void sysrq_handle_showregs(int key)
265{
266 struct pt_regs *regs = get_irq_regs();
267 if (regs)
268 show_regs(regs);
269 perf_event_print_debug();
270}
271static struct sysrq_key_op sysrq_showregs_op = {
272 .handler = sysrq_handle_showregs,
273 .help_msg = "show-registers(p)",
274 .action_msg = "Show Regs",
275 .enable_mask = SYSRQ_ENABLE_DUMP,
276};
277
278static void sysrq_handle_showstate(int key)
279{
280 show_state();
281 show_workqueue_state();
282}
283static struct sysrq_key_op sysrq_showstate_op = {
284 .handler = sysrq_handle_showstate,
285 .help_msg = "show-task-states(t)",
286 .action_msg = "Show State",
287 .enable_mask = SYSRQ_ENABLE_DUMP,
288};
289
290static void sysrq_handle_showstate_blocked(int key)
291{
292 show_state_filter(TASK_UNINTERRUPTIBLE);
293}
294static struct sysrq_key_op sysrq_showstate_blocked_op = {
295 .handler = sysrq_handle_showstate_blocked,
296 .help_msg = "show-blocked-tasks(w)",
297 .action_msg = "Show Blocked State",
298 .enable_mask = SYSRQ_ENABLE_DUMP,
299};
300
301#ifdef CONFIG_TRACING
302#include <linux/ftrace.h>
303
304static void sysrq_ftrace_dump(int key)
305{
306 ftrace_dump(DUMP_ALL);
307}
308static struct sysrq_key_op sysrq_ftrace_dump_op = {
309 .handler = sysrq_ftrace_dump,
310 .help_msg = "dump-ftrace-buffer(z)",
311 .action_msg = "Dump ftrace buffer",
312 .enable_mask = SYSRQ_ENABLE_DUMP,
313};
314#else
315#define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
316#endif
317
318static void sysrq_handle_showmem(int key)
319{
320 show_mem(0);
321}
322static struct sysrq_key_op sysrq_showmem_op = {
323 .handler = sysrq_handle_showmem,
324 .help_msg = "show-memory-usage(m)",
325 .action_msg = "Show Memory",
326 .enable_mask = SYSRQ_ENABLE_DUMP,
327};
328
329/*
330 * Signal sysrq helper function. Sends a signal to all user processes.
331 */
332static void send_sig_all(int sig)
333{
334 struct task_struct *p;
335
336 read_lock(&tasklist_lock);
337 for_each_process(p) {
338 if (p->flags & PF_KTHREAD)
339 continue;
340 if (is_global_init(p))
341 continue;
342
343 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
344 }
345 read_unlock(&tasklist_lock);
346}
347
348static void sysrq_handle_term(int key)
349{
350 send_sig_all(SIGTERM);
351 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
352}
353static struct sysrq_key_op sysrq_term_op = {
354 .handler = sysrq_handle_term,
355 .help_msg = "terminate-all-tasks(e)",
356 .action_msg = "Terminate All Tasks",
357 .enable_mask = SYSRQ_ENABLE_SIGNAL,
358};
359
360static void moom_callback(struct work_struct *ignored)
361{
362 const gfp_t gfp_mask = GFP_KERNEL;
363 struct oom_control oc = {
364 .zonelist = node_zonelist(first_memory_node, gfp_mask),
365 .nodemask = NULL,
366 .gfp_mask = gfp_mask,
367 .order = -1,
368 };
369
370 mutex_lock(&oom_lock);
371 if (!out_of_memory(&oc))
372 pr_info("OOM request ignored because killer is disabled\n");
373 mutex_unlock(&oom_lock);
374}
375
376static DECLARE_WORK(moom_work, moom_callback);
377
378static void sysrq_handle_moom(int key)
379{
380 schedule_work(&moom_work);
381}
382static struct sysrq_key_op sysrq_moom_op = {
383 .handler = sysrq_handle_moom,
384 .help_msg = "memory-full-oom-kill(f)",
385 .action_msg = "Manual OOM execution",
386 .enable_mask = SYSRQ_ENABLE_SIGNAL,
387};
388
389#ifdef CONFIG_BLOCK
390static void sysrq_handle_thaw(int key)
391{
392 emergency_thaw_all();
393}
394static struct sysrq_key_op sysrq_thaw_op = {
395 .handler = sysrq_handle_thaw,
396 .help_msg = "thaw-filesystems(j)",
397 .action_msg = "Emergency Thaw of all frozen filesystems",
398 .enable_mask = SYSRQ_ENABLE_SIGNAL,
399};
400#endif
401
402static void sysrq_handle_kill(int key)
403{
404 send_sig_all(SIGKILL);
405 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
406}
407static struct sysrq_key_op sysrq_kill_op = {
408 .handler = sysrq_handle_kill,
409 .help_msg = "kill-all-tasks(i)",
410 .action_msg = "Kill All Tasks",
411 .enable_mask = SYSRQ_ENABLE_SIGNAL,
412};
413
414static void sysrq_handle_unrt(int key)
415{
416 normalize_rt_tasks();
417}
418static struct sysrq_key_op sysrq_unrt_op = {
419 .handler = sysrq_handle_unrt,
420 .help_msg = "nice-all-RT-tasks(n)",
421 .action_msg = "Nice All RT Tasks",
422 .enable_mask = SYSRQ_ENABLE_RTNICE,
423};
424
425/* Key Operations table and lock */
426static DEFINE_SPINLOCK(sysrq_key_table_lock);
427
428static struct sysrq_key_op *sysrq_key_table[36] = {
429 &sysrq_loglevel_op, /* 0 */
430 &sysrq_loglevel_op, /* 1 */
431 &sysrq_loglevel_op, /* 2 */
432 &sysrq_loglevel_op, /* 3 */
433 &sysrq_loglevel_op, /* 4 */
434 &sysrq_loglevel_op, /* 5 */
435 &sysrq_loglevel_op, /* 6 */
436 &sysrq_loglevel_op, /* 7 */
437 &sysrq_loglevel_op, /* 8 */
438 &sysrq_loglevel_op, /* 9 */
439
440 /*
441 * a: Don't use for system provided sysrqs, it is handled specially on
442 * sparc and will never arrive.
443 */
444 NULL, /* a */
445 &sysrq_reboot_op, /* b */
446 &sysrq_crash_op, /* c & ibm_emac driver debug */
447 &sysrq_showlocks_op, /* d */
448 &sysrq_term_op, /* e */
449 &sysrq_moom_op, /* f */
450 /* g: May be registered for the kernel debugger */
451 NULL, /* g */
452 NULL, /* h - reserved for help */
453 &sysrq_kill_op, /* i */
454#ifdef CONFIG_BLOCK
455 &sysrq_thaw_op, /* j */
456#else
457 NULL, /* j */
458#endif
459 &sysrq_SAK_op, /* k */
460#ifdef CONFIG_SMP
461 &sysrq_showallcpus_op, /* l */
462#else
463 NULL, /* l */
464#endif
465 &sysrq_showmem_op, /* m */
466 &sysrq_unrt_op, /* n */
467 /* o: This will often be registered as 'Off' at init time */
468 NULL, /* o */
469 &sysrq_showregs_op, /* p */
470 &sysrq_show_timers_op, /* q */
471 &sysrq_unraw_op, /* r */
472 &sysrq_sync_op, /* s */
473 &sysrq_showstate_op, /* t */
474 &sysrq_mountro_op, /* u */
475 /* v: May be registered for frame buffer console restore */
476 NULL, /* v */
477 &sysrq_showstate_blocked_op, /* w */
478 /* x: May be registered on mips for TLB dump */
479 /* x: May be registered on ppc/powerpc for xmon */
480 /* x: May be registered on sparc64 for global PMU dump */
481 NULL, /* x */
482 /* y: May be registered on sparc64 for global register dump */
483 NULL, /* y */
484 &sysrq_ftrace_dump_op, /* z */
485};
486
487/* key2index calculation, -1 on invalid index */
488static int sysrq_key_table_key2index(int key)
489{
490 int retval;
491
492 if ((key >= '0') && (key <= '9'))
493 retval = key - '0';
494 else if ((key >= 'a') && (key <= 'z'))
495 retval = key + 10 - 'a';
496 else
497 retval = -1;
498 return retval;
499}
500
501/*
502 * get and put functions for the table, exposed to modules.
503 */
504struct sysrq_key_op *__sysrq_get_key_op(int key)
505{
506 struct sysrq_key_op *op_p = NULL;
507 int i;
508
509 i = sysrq_key_table_key2index(key);
510 if (i != -1)
511 op_p = sysrq_key_table[i];
512
513 return op_p;
514}
515
516static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
517{
518 int i = sysrq_key_table_key2index(key);
519
520 if (i != -1)
521 sysrq_key_table[i] = op_p;
522}
523
524void __handle_sysrq(int key, bool check_mask)
525{
526 struct sysrq_key_op *op_p;
527 int orig_log_level;
528 int i;
529
530 rcu_sysrq_start();
531 rcu_read_lock();
532 /*
533 * Raise the apparent loglevel to maximum so that the sysrq header
534 * is shown to provide the user with positive feedback. We do not
535 * simply emit this at KERN_EMERG as that would change message
536 * routing in the consumers of /proc/kmsg.
537 */
538 orig_log_level = console_loglevel;
539 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
540 pr_info("SysRq : ");
541
542 op_p = __sysrq_get_key_op(key);
543 if (op_p) {
544 /*
545 * Should we check for enabled operations (/proc/sysrq-trigger
546 * should not) and is the invoked operation enabled?
547 */
548 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
549 pr_cont("%s\n", op_p->action_msg);
550 console_loglevel = orig_log_level;
551 op_p->handler(key);
552 } else {
553 pr_cont("This sysrq operation is disabled.\n");
554 }
555 } else {
556 pr_cont("HELP : ");
557 /* Only print the help msg once per handler */
558 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
559 if (sysrq_key_table[i]) {
560 int j;
561
562 for (j = 0; sysrq_key_table[i] !=
563 sysrq_key_table[j]; j++)
564 ;
565 if (j != i)
566 continue;
567 pr_cont("%s ", sysrq_key_table[i]->help_msg);
568 }
569 }
570 pr_cont("\n");
571 console_loglevel = orig_log_level;
572 }
573 rcu_read_unlock();
574 rcu_sysrq_end();
575}
576
577void handle_sysrq(int key)
578{
579 if (sysrq_on())
580 __handle_sysrq(key, true);
581}
582EXPORT_SYMBOL(handle_sysrq);
583
584#ifdef CONFIG_INPUT
585static int sysrq_reset_downtime_ms;
586
587/* Simple translation table for the SysRq keys */
588static const unsigned char sysrq_xlate[KEY_CNT] =
589 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
590 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
591 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
592 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
593 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
594 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
595 "\r\000/"; /* 0x60 - 0x6f */
596
597struct sysrq_state {
598 struct input_handle handle;
599 struct work_struct reinject_work;
600 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
601 unsigned int alt;
602 unsigned int alt_use;
603 bool active;
604 bool need_reinject;
605 bool reinjecting;
606
607 /* reset sequence handling */
608 bool reset_canceled;
609 bool reset_requested;
610 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
611 int reset_seq_len;
612 int reset_seq_cnt;
613 int reset_seq_version;
614 struct timer_list keyreset_timer;
615};
616
617#define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
618static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
619static unsigned int sysrq_reset_seq_len;
620static unsigned int sysrq_reset_seq_version = 1;
621
622static void sysrq_parse_reset_sequence(struct sysrq_state *state)
623{
624 int i;
625 unsigned short key;
626
627 state->reset_seq_cnt = 0;
628
629 for (i = 0; i < sysrq_reset_seq_len; i++) {
630 key = sysrq_reset_seq[i];
631
632 if (key == KEY_RESERVED || key > KEY_MAX)
633 break;
634
635 __set_bit(key, state->reset_keybit);
636 state->reset_seq_len++;
637
638 if (test_bit(key, state->key_down))
639 state->reset_seq_cnt++;
640 }
641
642 /* Disable reset until old keys are not released */
643 state->reset_canceled = state->reset_seq_cnt != 0;
644
645 state->reset_seq_version = sysrq_reset_seq_version;
646}
647
648static void sysrq_do_reset(unsigned long _state)
649{
650 struct sysrq_state *state = (struct sysrq_state *) _state;
651
652 state->reset_requested = true;
653
654 sys_sync();
655 kernel_restart(NULL);
656}
657
658static void sysrq_handle_reset_request(struct sysrq_state *state)
659{
660 if (state->reset_requested)
661 __handle_sysrq(sysrq_xlate[KEY_B], false);
662
663 if (sysrq_reset_downtime_ms)
664 mod_timer(&state->keyreset_timer,
665 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
666 else
667 sysrq_do_reset((unsigned long)state);
668}
669
670static void sysrq_detect_reset_sequence(struct sysrq_state *state,
671 unsigned int code, int value)
672{
673 if (!test_bit(code, state->reset_keybit)) {
674 /*
675 * Pressing any key _not_ in reset sequence cancels
676 * the reset sequence. Also cancelling the timer in
677 * case additional keys were pressed after a reset
678 * has been requested.
679 */
680 if (value && state->reset_seq_cnt) {
681 state->reset_canceled = true;
682 del_timer(&state->keyreset_timer);
683 }
684 } else if (value == 0) {
685 /*
686 * Key release - all keys in the reset sequence need
687 * to be pressed and held for the reset timeout
688 * to hold.
689 */
690 del_timer(&state->keyreset_timer);
691
692 if (--state->reset_seq_cnt == 0)
693 state->reset_canceled = false;
694 } else if (value == 1) {
695 /* key press, not autorepeat */
696 if (++state->reset_seq_cnt == state->reset_seq_len &&
697 !state->reset_canceled) {
698 sysrq_handle_reset_request(state);
699 }
700 }
701}
702
703#ifdef CONFIG_OF
704static void sysrq_of_get_keyreset_config(void)
705{
706 u32 key;
707 struct device_node *np;
708 struct property *prop;
709 const __be32 *p;
710
711 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
712 if (!np) {
713 pr_debug("No sysrq node found");
714 return;
715 }
716
717 /* Reset in case a __weak definition was present */
718 sysrq_reset_seq_len = 0;
719
720 of_property_for_each_u32(np, "keyset", prop, p, key) {
721 if (key == KEY_RESERVED || key > KEY_MAX ||
722 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
723 break;
724
725 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
726 }
727
728 /* Get reset timeout if any. */
729 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
730}
731#else
732static void sysrq_of_get_keyreset_config(void)
733{
734}
735#endif
736
737static void sysrq_reinject_alt_sysrq(struct work_struct *work)
738{
739 struct sysrq_state *sysrq =
740 container_of(work, struct sysrq_state, reinject_work);
741 struct input_handle *handle = &sysrq->handle;
742 unsigned int alt_code = sysrq->alt_use;
743
744 if (sysrq->need_reinject) {
745 /* we do not want the assignment to be reordered */
746 sysrq->reinjecting = true;
747 mb();
748
749 /* Simulate press and release of Alt + SysRq */
750 input_inject_event(handle, EV_KEY, alt_code, 1);
751 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
752 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
753
754 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
755 input_inject_event(handle, EV_KEY, alt_code, 0);
756 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
757
758 mb();
759 sysrq->reinjecting = false;
760 }
761}
762
763static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
764 unsigned int code, int value)
765{
766 bool was_active = sysrq->active;
767 bool suppress;
768
769 switch (code) {
770
771 case KEY_LEFTALT:
772 case KEY_RIGHTALT:
773 if (!value) {
774 /* One of ALTs is being released */
775 if (sysrq->active && code == sysrq->alt_use)
776 sysrq->active = false;
777
778 sysrq->alt = KEY_RESERVED;
779
780 } else if (value != 2) {
781 sysrq->alt = code;
782 sysrq->need_reinject = false;
783 }
784 break;
785
786 case KEY_SYSRQ:
787 if (value == 1 && sysrq->alt != KEY_RESERVED) {
788 sysrq->active = true;
789 sysrq->alt_use = sysrq->alt;
790 /*
791 * If nothing else will be pressed we'll need
792 * to re-inject Alt-SysRq keysroke.
793 */
794 sysrq->need_reinject = true;
795 }
796
797 /*
798 * Pretend that sysrq was never pressed at all. This
799 * is needed to properly handle KGDB which will try
800 * to release all keys after exiting debugger. If we
801 * do not clear key bit it KGDB will end up sending
802 * release events for Alt and SysRq, potentially
803 * triggering print screen function.
804 */
805 if (sysrq->active)
806 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
807
808 break;
809
810 default:
811 if (sysrq->active && value && value != 2) {
812 sysrq->need_reinject = false;
813 __handle_sysrq(sysrq_xlate[code], true);
814 }
815 break;
816 }
817
818 suppress = sysrq->active;
819
820 if (!sysrq->active) {
821
822 /*
823 * See if reset sequence has changed since the last time.
824 */
825 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
826 sysrq_parse_reset_sequence(sysrq);
827
828 /*
829 * If we are not suppressing key presses keep track of
830 * keyboard state so we can release keys that have been
831 * pressed before entering SysRq mode.
832 */
833 if (value)
834 set_bit(code, sysrq->key_down);
835 else
836 clear_bit(code, sysrq->key_down);
837
838 if (was_active)
839 schedule_work(&sysrq->reinject_work);
840
841 /* Check for reset sequence */
842 sysrq_detect_reset_sequence(sysrq, code, value);
843
844 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
845 /*
846 * Pass on release events for keys that was pressed before
847 * entering SysRq mode.
848 */
849 suppress = false;
850 }
851
852 return suppress;
853}
854
855static bool sysrq_filter(struct input_handle *handle,
856 unsigned int type, unsigned int code, int value)
857{
858 struct sysrq_state *sysrq = handle->private;
859 bool suppress;
860
861 /*
862 * Do not filter anything if we are in the process of re-injecting
863 * Alt+SysRq combination.
864 */
865 if (sysrq->reinjecting)
866 return false;
867
868 switch (type) {
869
870 case EV_SYN:
871 suppress = false;
872 break;
873
874 case EV_KEY:
875 suppress = sysrq_handle_keypress(sysrq, code, value);
876 break;
877
878 default:
879 suppress = sysrq->active;
880 break;
881 }
882
883 return suppress;
884}
885
886static int sysrq_connect(struct input_handler *handler,
887 struct input_dev *dev,
888 const struct input_device_id *id)
889{
890 struct sysrq_state *sysrq;
891 int error;
892
893 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
894 if (!sysrq)
895 return -ENOMEM;
896
897 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
898
899 sysrq->handle.dev = dev;
900 sysrq->handle.handler = handler;
901 sysrq->handle.name = "sysrq";
902 sysrq->handle.private = sysrq;
903 setup_timer(&sysrq->keyreset_timer,
904 sysrq_do_reset, (unsigned long)sysrq);
905
906 error = input_register_handle(&sysrq->handle);
907 if (error) {
908 pr_err("Failed to register input sysrq handler, error %d\n",
909 error);
910 goto err_free;
911 }
912
913 error = input_open_device(&sysrq->handle);
914 if (error) {
915 pr_err("Failed to open input device, error %d\n", error);
916 goto err_unregister;
917 }
918
919 return 0;
920
921 err_unregister:
922 input_unregister_handle(&sysrq->handle);
923 err_free:
924 kfree(sysrq);
925 return error;
926}
927
928static void sysrq_disconnect(struct input_handle *handle)
929{
930 struct sysrq_state *sysrq = handle->private;
931
932 input_close_device(handle);
933 cancel_work_sync(&sysrq->reinject_work);
934 del_timer_sync(&sysrq->keyreset_timer);
935 input_unregister_handle(handle);
936 kfree(sysrq);
937}
938
939/*
940 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
941 * keyboards have SysRq key predefined and so user may add it to keymap
942 * later, but we expect all such keyboards to have left alt.
943 */
944static const struct input_device_id sysrq_ids[] = {
945 {
946 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
947 INPUT_DEVICE_ID_MATCH_KEYBIT,
948 .evbit = { BIT_MASK(EV_KEY) },
949 .keybit = { BIT_MASK(KEY_LEFTALT) },
950 },
951 { },
952};
953
954static struct input_handler sysrq_handler = {
955 .filter = sysrq_filter,
956 .connect = sysrq_connect,
957 .disconnect = sysrq_disconnect,
958 .name = "sysrq",
959 .id_table = sysrq_ids,
960};
961
962static bool sysrq_handler_registered;
963
964static inline void sysrq_register_handler(void)
965{
966 int error;
967
968 sysrq_of_get_keyreset_config();
969
970 error = input_register_handler(&sysrq_handler);
971 if (error)
972 pr_err("Failed to register input handler, error %d", error);
973 else
974 sysrq_handler_registered = true;
975}
976
977static inline void sysrq_unregister_handler(void)
978{
979 if (sysrq_handler_registered) {
980 input_unregister_handler(&sysrq_handler);
981 sysrq_handler_registered = false;
982 }
983}
984
985static int sysrq_reset_seq_param_set(const char *buffer,
986 const struct kernel_param *kp)
987{
988 unsigned long val;
989 int error;
990
991 error = kstrtoul(buffer, 0, &val);
992 if (error < 0)
993 return error;
994
995 if (val > KEY_MAX)
996 return -EINVAL;
997
998 *((unsigned short *)kp->arg) = val;
999 sysrq_reset_seq_version++;
1000
1001 return 0;
1002}
1003
1004static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1005 .get = param_get_ushort,
1006 .set = sysrq_reset_seq_param_set,
1007};
1008
1009#define param_check_sysrq_reset_seq(name, p) \
1010 __param_check(name, p, unsigned short)
1011
1012/*
1013 * not really modular, but the easiest way to keep compat with existing
1014 * bootargs behaviour is to continue using module_param here.
1015 */
1016module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1017 &sysrq_reset_seq_len, 0644);
1018
1019module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1020
1021#else
1022
1023static inline void sysrq_register_handler(void)
1024{
1025}
1026
1027static inline void sysrq_unregister_handler(void)
1028{
1029}
1030
1031#endif /* CONFIG_INPUT */
1032
1033int sysrq_toggle_support(int enable_mask)
1034{
1035 bool was_enabled = sysrq_on();
1036
1037 sysrq_enabled = enable_mask;
1038
1039 if (was_enabled != sysrq_on()) {
1040 if (sysrq_on())
1041 sysrq_register_handler();
1042 else
1043 sysrq_unregister_handler();
1044 }
1045
1046 return 0;
1047}
1048
1049static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1050 struct sysrq_key_op *remove_op_p)
1051{
1052 int retval;
1053
1054 spin_lock(&sysrq_key_table_lock);
1055 if (__sysrq_get_key_op(key) == remove_op_p) {
1056 __sysrq_put_key_op(key, insert_op_p);
1057 retval = 0;
1058 } else {
1059 retval = -1;
1060 }
1061 spin_unlock(&sysrq_key_table_lock);
1062
1063 /*
1064 * A concurrent __handle_sysrq either got the old op or the new op.
1065 * Wait for it to go away before returning, so the code for an old
1066 * op is not freed (eg. on module unload) while it is in use.
1067 */
1068 synchronize_rcu();
1069
1070 return retval;
1071}
1072
1073int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1074{
1075 return __sysrq_swap_key_ops(key, op_p, NULL);
1076}
1077EXPORT_SYMBOL(register_sysrq_key);
1078
1079int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1080{
1081 return __sysrq_swap_key_ops(key, NULL, op_p);
1082}
1083EXPORT_SYMBOL(unregister_sysrq_key);
1084
1085#ifdef CONFIG_PROC_FS
1086/*
1087 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1088 */
1089static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1090 size_t count, loff_t *ppos)
1091{
1092 if (count) {
1093 char c;
1094
1095 if (get_user(c, buf))
1096 return -EFAULT;
1097 __handle_sysrq(c, false);
1098 }
1099
1100 return count;
1101}
1102
1103static const struct file_operations proc_sysrq_trigger_operations = {
1104 .write = write_sysrq_trigger,
1105 .llseek = noop_llseek,
1106};
1107
1108static void sysrq_init_procfs(void)
1109{
1110 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1111 &proc_sysrq_trigger_operations))
1112 pr_err("Failed to register proc interface\n");
1113}
1114
1115#else
1116
1117static inline void sysrq_init_procfs(void)
1118{
1119}
1120
1121#endif /* CONFIG_PROC_FS */
1122
1123static int __init sysrq_init(void)
1124{
1125 sysrq_init_procfs();
1126
1127 if (sysrq_on())
1128 sysrq_register_handler();
1129
1130 return 0;
1131}
1132device_initcall(sysrq_init);