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