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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(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 pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
237 return;
238 }
239
240 raw_spin_lock_irqsave(&show_lock, flags);
241 pr_info("CPU%d:\n", smp_processor_id());
242 show_stack(NULL, NULL, KERN_INFO);
243 raw_spin_unlock_irqrestore(&show_lock, flags);
244}
245
246static void sysrq_showregs_othercpus(struct work_struct *dummy)
247{
248 smp_call_function(showacpu, NULL, 0);
249}
250
251static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
252
253static void sysrq_handle_showallcpus(int key)
254{
255 /*
256 * Fall back to the workqueue based printing if the
257 * backtrace printing did not succeed or the
258 * architecture has no support for it:
259 */
260 if (!trigger_all_cpu_backtrace()) {
261 struct pt_regs *regs = NULL;
262
263 if (in_hardirq())
264 regs = get_irq_regs();
265
266 pr_info("CPU%d:\n", smp_processor_id());
267 if (regs)
268 show_regs(regs);
269 else
270 show_stack(NULL, NULL, KERN_INFO);
271
272 schedule_work(&sysrq_showallcpus);
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(int 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(int 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(int 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(int 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(int key)
344{
345 show_mem(0, NULL);
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(int 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(int 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(int 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(int 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(int 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(int key)
535{
536 int retval;
537
538 if ((key >= '0') && (key <= '9'))
539 retval = key - '0';
540 else if ((key >= 'a') && (key <= 'z'))
541 retval = key + 10 - 'a';
542 else if ((key >= 'A') && (key <= 'Z'))
543 retval = key + 36 - 'A';
544 else
545 retval = -1;
546 return retval;
547}
548
549/*
550 * get and put functions for the table, exposed to modules.
551 */
552static const struct sysrq_key_op *__sysrq_get_key_op(int key)
553{
554 const struct sysrq_key_op *op_p = NULL;
555 int i;
556
557 i = sysrq_key_table_key2index(key);
558 if (i != -1)
559 op_p = sysrq_key_table[i];
560
561 return op_p;
562}
563
564static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p)
565{
566 int i = sysrq_key_table_key2index(key);
567
568 if (i != -1)
569 sysrq_key_table[i] = op_p;
570}
571
572void __handle_sysrq(int key, bool check_mask)
573{
574 const struct sysrq_key_op *op_p;
575 int orig_log_level;
576 int orig_suppress_printk;
577 int i;
578
579 orig_suppress_printk = suppress_printk;
580 suppress_printk = 0;
581
582 rcu_sysrq_start();
583 rcu_read_lock();
584 /*
585 * Raise the apparent loglevel to maximum so that the sysrq header
586 * is shown to provide the user with positive feedback. We do not
587 * simply emit this at KERN_EMERG as that would change message
588 * routing in the consumers of /proc/kmsg.
589 */
590 orig_log_level = console_loglevel;
591 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
592
593 op_p = __sysrq_get_key_op(key);
594 if (op_p) {
595 /*
596 * Should we check for enabled operations (/proc/sysrq-trigger
597 * should not) and is the invoked operation enabled?
598 */
599 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
600 pr_info("%s\n", op_p->action_msg);
601 console_loglevel = orig_log_level;
602 op_p->handler(key);
603 } else {
604 pr_info("This sysrq operation is disabled.\n");
605 console_loglevel = orig_log_level;
606 }
607 } else {
608 pr_info("HELP : ");
609 /* Only print the help msg once per handler */
610 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
611 if (sysrq_key_table[i]) {
612 int j;
613
614 for (j = 0; sysrq_key_table[i] !=
615 sysrq_key_table[j]; j++)
616 ;
617 if (j != i)
618 continue;
619 pr_cont("%s ", sysrq_key_table[i]->help_msg);
620 }
621 }
622 pr_cont("\n");
623 console_loglevel = orig_log_level;
624 }
625 rcu_read_unlock();
626 rcu_sysrq_end();
627
628 suppress_printk = orig_suppress_printk;
629}
630
631void handle_sysrq(int key)
632{
633 if (sysrq_on())
634 __handle_sysrq(key, true);
635}
636EXPORT_SYMBOL(handle_sysrq);
637
638#ifdef CONFIG_INPUT
639static int sysrq_reset_downtime_ms;
640
641/* Simple translation table for the SysRq keys */
642static const unsigned char sysrq_xlate[KEY_CNT] =
643 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
644 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
645 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
646 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
647 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
648 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
649 "\r\000/"; /* 0x60 - 0x6f */
650
651struct sysrq_state {
652 struct input_handle handle;
653 struct work_struct reinject_work;
654 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
655 unsigned int alt;
656 unsigned int alt_use;
657 unsigned int shift;
658 unsigned int shift_use;
659 bool active;
660 bool need_reinject;
661 bool reinjecting;
662
663 /* reset sequence handling */
664 bool reset_canceled;
665 bool reset_requested;
666 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
667 int reset_seq_len;
668 int reset_seq_cnt;
669 int reset_seq_version;
670 struct timer_list keyreset_timer;
671};
672
673#define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
674static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
675static unsigned int sysrq_reset_seq_len;
676static unsigned int sysrq_reset_seq_version = 1;
677
678static void sysrq_parse_reset_sequence(struct sysrq_state *state)
679{
680 int i;
681 unsigned short key;
682
683 state->reset_seq_cnt = 0;
684
685 for (i = 0; i < sysrq_reset_seq_len; i++) {
686 key = sysrq_reset_seq[i];
687
688 if (key == KEY_RESERVED || key > KEY_MAX)
689 break;
690
691 __set_bit(key, state->reset_keybit);
692 state->reset_seq_len++;
693
694 if (test_bit(key, state->key_down))
695 state->reset_seq_cnt++;
696 }
697
698 /* Disable reset until old keys are not released */
699 state->reset_canceled = state->reset_seq_cnt != 0;
700
701 state->reset_seq_version = sysrq_reset_seq_version;
702}
703
704static void sysrq_do_reset(struct timer_list *t)
705{
706 struct sysrq_state *state = from_timer(state, t, keyreset_timer);
707
708 state->reset_requested = true;
709
710 orderly_reboot();
711}
712
713static void sysrq_handle_reset_request(struct sysrq_state *state)
714{
715 if (state->reset_requested)
716 __handle_sysrq(sysrq_xlate[KEY_B], false);
717
718 if (sysrq_reset_downtime_ms)
719 mod_timer(&state->keyreset_timer,
720 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
721 else
722 sysrq_do_reset(&state->keyreset_timer);
723}
724
725static void sysrq_detect_reset_sequence(struct sysrq_state *state,
726 unsigned int code, int value)
727{
728 if (!test_bit(code, state->reset_keybit)) {
729 /*
730 * Pressing any key _not_ in reset sequence cancels
731 * the reset sequence. Also cancelling the timer in
732 * case additional keys were pressed after a reset
733 * has been requested.
734 */
735 if (value && state->reset_seq_cnt) {
736 state->reset_canceled = true;
737 del_timer(&state->keyreset_timer);
738 }
739 } else if (value == 0) {
740 /*
741 * Key release - all keys in the reset sequence need
742 * to be pressed and held for the reset timeout
743 * to hold.
744 */
745 del_timer(&state->keyreset_timer);
746
747 if (--state->reset_seq_cnt == 0)
748 state->reset_canceled = false;
749 } else if (value == 1) {
750 /* key press, not autorepeat */
751 if (++state->reset_seq_cnt == state->reset_seq_len &&
752 !state->reset_canceled) {
753 sysrq_handle_reset_request(state);
754 }
755 }
756}
757
758#ifdef CONFIG_OF
759static void sysrq_of_get_keyreset_config(void)
760{
761 u32 key;
762 struct device_node *np;
763 struct property *prop;
764 const __be32 *p;
765
766 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
767 if (!np) {
768 pr_debug("No sysrq node found");
769 return;
770 }
771
772 /* Reset in case a __weak definition was present */
773 sysrq_reset_seq_len = 0;
774
775 of_property_for_each_u32(np, "keyset", prop, p, key) {
776 if (key == KEY_RESERVED || key > KEY_MAX ||
777 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
778 break;
779
780 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
781 }
782
783 /* Get reset timeout if any. */
784 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
785
786 of_node_put(np);
787}
788#else
789static void sysrq_of_get_keyreset_config(void)
790{
791}
792#endif
793
794static void sysrq_reinject_alt_sysrq(struct work_struct *work)
795{
796 struct sysrq_state *sysrq =
797 container_of(work, struct sysrq_state, reinject_work);
798 struct input_handle *handle = &sysrq->handle;
799 unsigned int alt_code = sysrq->alt_use;
800
801 if (sysrq->need_reinject) {
802 /* we do not want the assignment to be reordered */
803 sysrq->reinjecting = true;
804 mb();
805
806 /* Simulate press and release of Alt + SysRq */
807 input_inject_event(handle, EV_KEY, alt_code, 1);
808 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
809 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
810
811 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
812 input_inject_event(handle, EV_KEY, alt_code, 0);
813 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
814
815 mb();
816 sysrq->reinjecting = false;
817 }
818}
819
820static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
821 unsigned int code, int value)
822{
823 bool was_active = sysrq->active;
824 bool suppress;
825
826 switch (code) {
827
828 case KEY_LEFTALT:
829 case KEY_RIGHTALT:
830 if (!value) {
831 /* One of ALTs is being released */
832 if (sysrq->active && code == sysrq->alt_use)
833 sysrq->active = false;
834
835 sysrq->alt = KEY_RESERVED;
836
837 } else if (value != 2) {
838 sysrq->alt = code;
839 sysrq->need_reinject = false;
840 }
841 break;
842
843 case KEY_LEFTSHIFT:
844 case KEY_RIGHTSHIFT:
845 if (!value)
846 sysrq->shift = KEY_RESERVED;
847 else if (value != 2)
848 sysrq->shift = code;
849 if (sysrq->active)
850 sysrq->shift_use = sysrq->shift;
851 break;
852
853 case KEY_SYSRQ:
854 if (value == 1 && sysrq->alt != KEY_RESERVED) {
855 sysrq->active = true;
856 sysrq->alt_use = sysrq->alt;
857 /* either RESERVED (for released) or actual code */
858 sysrq->shift_use = sysrq->shift;
859 /*
860 * If nothing else will be pressed we'll need
861 * to re-inject Alt-SysRq keysroke.
862 */
863 sysrq->need_reinject = true;
864 }
865
866 /*
867 * Pretend that sysrq was never pressed at all. This
868 * is needed to properly handle KGDB which will try
869 * to release all keys after exiting debugger. If we
870 * do not clear key bit it KGDB will end up sending
871 * release events for Alt and SysRq, potentially
872 * triggering print screen function.
873 */
874 if (sysrq->active)
875 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
876
877 break;
878
879 default:
880 if (sysrq->active && value && value != 2) {
881 unsigned char c = sysrq_xlate[code];
882
883 sysrq->need_reinject = false;
884 if (sysrq->shift_use != KEY_RESERVED)
885 c = toupper(c);
886 __handle_sysrq(c, true);
887 }
888 break;
889 }
890
891 suppress = sysrq->active;
892
893 if (!sysrq->active) {
894
895 /*
896 * See if reset sequence has changed since the last time.
897 */
898 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
899 sysrq_parse_reset_sequence(sysrq);
900
901 /*
902 * If we are not suppressing key presses keep track of
903 * keyboard state so we can release keys that have been
904 * pressed before entering SysRq mode.
905 */
906 if (value)
907 set_bit(code, sysrq->key_down);
908 else
909 clear_bit(code, sysrq->key_down);
910
911 if (was_active)
912 schedule_work(&sysrq->reinject_work);
913
914 /* Check for reset sequence */
915 sysrq_detect_reset_sequence(sysrq, code, value);
916
917 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
918 /*
919 * Pass on release events for keys that was pressed before
920 * entering SysRq mode.
921 */
922 suppress = false;
923 }
924
925 return suppress;
926}
927
928static bool sysrq_filter(struct input_handle *handle,
929 unsigned int type, unsigned int code, int value)
930{
931 struct sysrq_state *sysrq = handle->private;
932 bool suppress;
933
934 /*
935 * Do not filter anything if we are in the process of re-injecting
936 * Alt+SysRq combination.
937 */
938 if (sysrq->reinjecting)
939 return false;
940
941 switch (type) {
942
943 case EV_SYN:
944 suppress = false;
945 break;
946
947 case EV_KEY:
948 suppress = sysrq_handle_keypress(sysrq, code, value);
949 break;
950
951 default:
952 suppress = sysrq->active;
953 break;
954 }
955
956 return suppress;
957}
958
959static int sysrq_connect(struct input_handler *handler,
960 struct input_dev *dev,
961 const struct input_device_id *id)
962{
963 struct sysrq_state *sysrq;
964 int error;
965
966 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
967 if (!sysrq)
968 return -ENOMEM;
969
970 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
971
972 sysrq->handle.dev = dev;
973 sysrq->handle.handler = handler;
974 sysrq->handle.name = "sysrq";
975 sysrq->handle.private = sysrq;
976 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
977
978 error = input_register_handle(&sysrq->handle);
979 if (error) {
980 pr_err("Failed to register input sysrq handler, error %d\n",
981 error);
982 goto err_free;
983 }
984
985 error = input_open_device(&sysrq->handle);
986 if (error) {
987 pr_err("Failed to open input device, error %d\n", error);
988 goto err_unregister;
989 }
990
991 return 0;
992
993 err_unregister:
994 input_unregister_handle(&sysrq->handle);
995 err_free:
996 kfree(sysrq);
997 return error;
998}
999
1000static void sysrq_disconnect(struct input_handle *handle)
1001{
1002 struct sysrq_state *sysrq = handle->private;
1003
1004 input_close_device(handle);
1005 cancel_work_sync(&sysrq->reinject_work);
1006 timer_shutdown_sync(&sysrq->keyreset_timer);
1007 input_unregister_handle(handle);
1008 kfree(sysrq);
1009}
1010
1011/*
1012 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1013 * keyboards have SysRq key predefined and so user may add it to keymap
1014 * later, but we expect all such keyboards to have left alt.
1015 */
1016static const struct input_device_id sysrq_ids[] = {
1017 {
1018 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1019 INPUT_DEVICE_ID_MATCH_KEYBIT,
1020 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1021 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1022 },
1023 { },
1024};
1025
1026static struct input_handler sysrq_handler = {
1027 .filter = sysrq_filter,
1028 .connect = sysrq_connect,
1029 .disconnect = sysrq_disconnect,
1030 .name = "sysrq",
1031 .id_table = sysrq_ids,
1032};
1033
1034static inline void sysrq_register_handler(void)
1035{
1036 int error;
1037
1038 sysrq_of_get_keyreset_config();
1039
1040 error = input_register_handler(&sysrq_handler);
1041 if (error)
1042 pr_err("Failed to register input handler, error %d", error);
1043}
1044
1045static inline void sysrq_unregister_handler(void)
1046{
1047 input_unregister_handler(&sysrq_handler);
1048}
1049
1050static int sysrq_reset_seq_param_set(const char *buffer,
1051 const struct kernel_param *kp)
1052{
1053 unsigned long val;
1054 int error;
1055
1056 error = kstrtoul(buffer, 0, &val);
1057 if (error < 0)
1058 return error;
1059
1060 if (val > KEY_MAX)
1061 return -EINVAL;
1062
1063 *((unsigned short *)kp->arg) = val;
1064 sysrq_reset_seq_version++;
1065
1066 return 0;
1067}
1068
1069static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1070 .get = param_get_ushort,
1071 .set = sysrq_reset_seq_param_set,
1072};
1073
1074#define param_check_sysrq_reset_seq(name, p) \
1075 __param_check(name, p, unsigned short)
1076
1077/*
1078 * not really modular, but the easiest way to keep compat with existing
1079 * bootargs behaviour is to continue using module_param here.
1080 */
1081module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1082 &sysrq_reset_seq_len, 0644);
1083
1084module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1085
1086#else
1087
1088static inline void sysrq_register_handler(void)
1089{
1090}
1091
1092static inline void sysrq_unregister_handler(void)
1093{
1094}
1095
1096#endif /* CONFIG_INPUT */
1097
1098int sysrq_toggle_support(int enable_mask)
1099{
1100 bool was_enabled = sysrq_on();
1101
1102 sysrq_enabled = enable_mask;
1103
1104 if (was_enabled != sysrq_on()) {
1105 if (sysrq_on())
1106 sysrq_register_handler();
1107 else
1108 sysrq_unregister_handler();
1109 }
1110
1111 return 0;
1112}
1113EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1114
1115static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p,
1116 const struct sysrq_key_op *remove_op_p)
1117{
1118 int retval;
1119
1120 spin_lock(&sysrq_key_table_lock);
1121 if (__sysrq_get_key_op(key) == remove_op_p) {
1122 __sysrq_put_key_op(key, insert_op_p);
1123 retval = 0;
1124 } else {
1125 retval = -1;
1126 }
1127 spin_unlock(&sysrq_key_table_lock);
1128
1129 /*
1130 * A concurrent __handle_sysrq either got the old op or the new op.
1131 * Wait for it to go away before returning, so the code for an old
1132 * op is not freed (eg. on module unload) while it is in use.
1133 */
1134 synchronize_rcu();
1135
1136 return retval;
1137}
1138
1139int register_sysrq_key(int key, const struct sysrq_key_op *op_p)
1140{
1141 return __sysrq_swap_key_ops(key, op_p, NULL);
1142}
1143EXPORT_SYMBOL(register_sysrq_key);
1144
1145int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)
1146{
1147 return __sysrq_swap_key_ops(key, NULL, op_p);
1148}
1149EXPORT_SYMBOL(unregister_sysrq_key);
1150
1151#ifdef CONFIG_PROC_FS
1152/*
1153 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1154 */
1155static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1156 size_t count, loff_t *ppos)
1157{
1158 if (count) {
1159 char c;
1160
1161 if (get_user(c, buf))
1162 return -EFAULT;
1163 __handle_sysrq(c, false);
1164 }
1165
1166 return count;
1167}
1168
1169static const struct proc_ops sysrq_trigger_proc_ops = {
1170 .proc_write = write_sysrq_trigger,
1171 .proc_lseek = noop_llseek,
1172};
1173
1174static void sysrq_init_procfs(void)
1175{
1176 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1177 &sysrq_trigger_proc_ops))
1178 pr_err("Failed to register proc interface\n");
1179}
1180
1181#else
1182
1183static inline void sysrq_init_procfs(void)
1184{
1185}
1186
1187#endif /* CONFIG_PROC_FS */
1188
1189static int __init sysrq_init(void)
1190{
1191 sysrq_init_procfs();
1192
1193 if (sysrq_on())
1194 sysrq_register_handler();
1195
1196 return 0;
1197}
1198device_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);