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