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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Linux Magic System Request Key Hacks
4 *
5 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
6 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
7 *
8 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
9 * overhauled to use key registration
10 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies
11 *
12 * Copyright (c) 2010 Dmitry Torokhov
13 * Input handler conversion
14 */
15
16#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17
18#include <linux/sched/signal.h>
19#include <linux/sched/rt.h>
20#include <linux/sched/debug.h>
21#include <linux/sched/task.h>
22#include <linux/ctype.h>
23#include <linux/interrupt.h>
24#include <linux/mm.h>
25#include <linux/fs.h>
26#include <linux/mount.h>
27#include <linux/kdev_t.h>
28#include <linux/major.h>
29#include <linux/reboot.h>
30#include <linux/sysrq.h>
31#include <linux/kbd_kern.h>
32#include <linux/proc_fs.h>
33#include <linux/nmi.h>
34#include <linux/quotaops.h>
35#include <linux/perf_event.h>
36#include <linux/kernel.h>
37#include <linux/module.h>
38#include <linux/suspend.h>
39#include <linux/writeback.h>
40#include <linux/swap.h>
41#include <linux/spinlock.h>
42#include <linux/vt_kern.h>
43#include <linux/workqueue.h>
44#include <linux/hrtimer.h>
45#include <linux/oom.h>
46#include <linux/slab.h>
47#include <linux/input.h>
48#include <linux/uaccess.h>
49#include <linux/moduleparam.h>
50#include <linux/jiffies.h>
51#include <linux/syscalls.h>
52#include <linux/of.h>
53#include <linux/rcupdate.h>
54
55#include <asm/ptrace.h>
56#include <asm/irq_regs.h>
57
58/* Whether we react on sysrq keys or just ignore them */
59static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
60static bool __read_mostly sysrq_always_enabled;
61
62static bool sysrq_on(void)
63{
64 return sysrq_enabled || sysrq_always_enabled;
65}
66
67/**
68 * sysrq_mask - Getter for sysrq_enabled mask.
69 *
70 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
71 */
72int sysrq_mask(void)
73{
74 if (sysrq_always_enabled)
75 return 1;
76 return sysrq_enabled;
77}
78EXPORT_SYMBOL_GPL(sysrq_mask);
79
80/*
81 * A value of 1 means 'all', other nonzero values are an op mask:
82 */
83static bool sysrq_on_mask(int mask)
84{
85 return sysrq_always_enabled ||
86 sysrq_enabled == 1 ||
87 (sysrq_enabled & mask);
88}
89
90static int __init sysrq_always_enabled_setup(char *str)
91{
92 sysrq_always_enabled = true;
93 pr_info("sysrq always enabled.\n");
94
95 return 1;
96}
97
98__setup("sysrq_always_enabled", sysrq_always_enabled_setup);
99
100
101static void sysrq_handle_loglevel(u8 key)
102{
103 u8 loglevel = key - '0';
104
105 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
106 pr_info("Loglevel set to %u\n", loglevel);
107 console_loglevel = loglevel;
108}
109static const struct sysrq_key_op sysrq_loglevel_op = {
110 .handler = sysrq_handle_loglevel,
111 .help_msg = "loglevel(0-9)",
112 .action_msg = "Changing Loglevel",
113 .enable_mask = SYSRQ_ENABLE_LOG,
114};
115
116#ifdef CONFIG_VT
117static void sysrq_handle_SAK(u8 key)
118{
119 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
120
121 schedule_work(work: SAK_work);
122}
123static const struct sysrq_key_op sysrq_SAK_op = {
124 .handler = sysrq_handle_SAK,
125 .help_msg = "sak(k)",
126 .action_msg = "SAK",
127 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
128};
129#else
130#define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
131#endif
132
133#ifdef CONFIG_VT
134static void sysrq_handle_unraw(u8 key)
135{
136 vt_reset_unicode(console: fg_console);
137}
138
139static const struct sysrq_key_op sysrq_unraw_op = {
140 .handler = sysrq_handle_unraw,
141 .help_msg = "unraw(r)",
142 .action_msg = "Keyboard mode set to system default",
143 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
144};
145#else
146#define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
147#endif /* CONFIG_VT */
148
149static void sysrq_handle_crash(u8 key)
150{
151 /* release the RCU read lock before crashing */
152 rcu_read_unlock();
153
154 panic(fmt: "sysrq triggered crash\n");
155}
156static const struct sysrq_key_op sysrq_crash_op = {
157 .handler = sysrq_handle_crash,
158 .help_msg = "crash(c)",
159 .action_msg = "Trigger a crash",
160 .enable_mask = SYSRQ_ENABLE_DUMP,
161};
162
163static void sysrq_handle_reboot(u8 key)
164{
165 lockdep_off();
166 local_irq_enable();
167 emergency_restart();
168}
169static const struct sysrq_key_op sysrq_reboot_op = {
170 .handler = sysrq_handle_reboot,
171 .help_msg = "reboot(b)",
172 .action_msg = "Resetting",
173 .enable_mask = SYSRQ_ENABLE_BOOT,
174};
175
176const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
177
178static void sysrq_handle_sync(u8 key)
179{
180 emergency_sync();
181}
182static const struct sysrq_key_op sysrq_sync_op = {
183 .handler = sysrq_handle_sync,
184 .help_msg = "sync(s)",
185 .action_msg = "Emergency Sync",
186 .enable_mask = SYSRQ_ENABLE_SYNC,
187};
188
189static void sysrq_handle_show_timers(u8 key)
190{
191 sysrq_timer_list_show();
192}
193
194static const struct sysrq_key_op sysrq_show_timers_op = {
195 .handler = sysrq_handle_show_timers,
196 .help_msg = "show-all-timers(q)",
197 .action_msg = "Show clockevent devices & pending hrtimers (no others)",
198};
199
200static void sysrq_handle_mountro(u8 key)
201{
202 emergency_remount();
203}
204static const struct sysrq_key_op sysrq_mountro_op = {
205 .handler = sysrq_handle_mountro,
206 .help_msg = "unmount(u)",
207 .action_msg = "Emergency Remount R/O",
208 .enable_mask = SYSRQ_ENABLE_REMOUNT,
209};
210
211#ifdef CONFIG_LOCKDEP
212static void sysrq_handle_showlocks(u8 key)
213{
214 debug_show_all_locks();
215}
216
217static const struct sysrq_key_op sysrq_showlocks_op = {
218 .handler = sysrq_handle_showlocks,
219 .help_msg = "show-all-locks(d)",
220 .action_msg = "Show Locks Held",
221};
222#else
223#define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
224#endif
225
226#ifdef CONFIG_SMP
227static DEFINE_RAW_SPINLOCK(show_lock);
228
229static void showacpu(void *dummy)
230{
231 unsigned long flags;
232
233 /* Idle CPUs have no interesting backtrace. */
234 if (idle_cpu(smp_processor_id())) {
235 pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
236 return;
237 }
238
239 raw_spin_lock_irqsave(&show_lock, flags);
240 pr_info("CPU%d:\n", smp_processor_id());
241 show_stack(NULL, NULL, KERN_INFO);
242 raw_spin_unlock_irqrestore(&show_lock, flags);
243}
244
245static void sysrq_showregs_othercpus(struct work_struct *dummy)
246{
247 smp_call_function(func: showacpu, NULL, wait: 0);
248}
249
250static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
251
252static void sysrq_handle_showallcpus(u8 key)
253{
254 /*
255 * Fall back to the workqueue based printing if the
256 * backtrace printing did not succeed or the
257 * architecture has no support for it:
258 */
259 if (!trigger_all_cpu_backtrace()) {
260 struct pt_regs *regs = NULL;
261
262 if (in_hardirq())
263 regs = get_irq_regs();
264
265 pr_info("CPU%d:\n", get_cpu());
266 if (regs)
267 show_regs(regs);
268 else
269 show_stack(NULL, NULL, KERN_INFO);
270
271 schedule_work(work: &sysrq_showallcpus);
272 put_cpu();
273 }
274}
275
276static const struct sysrq_key_op sysrq_showallcpus_op = {
277 .handler = sysrq_handle_showallcpus,
278 .help_msg = "show-backtrace-all-active-cpus(l)",
279 .action_msg = "Show backtrace of all active CPUs",
280 .enable_mask = SYSRQ_ENABLE_DUMP,
281};
282#else
283#define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL)
284#endif
285
286static void sysrq_handle_showregs(u8 key)
287{
288 struct pt_regs *regs = NULL;
289
290 if (in_hardirq())
291 regs = get_irq_regs();
292 if (regs)
293 show_regs(regs);
294 perf_event_print_debug();
295}
296static const struct sysrq_key_op sysrq_showregs_op = {
297 .handler = sysrq_handle_showregs,
298 .help_msg = "show-registers(p)",
299 .action_msg = "Show Regs",
300 .enable_mask = SYSRQ_ENABLE_DUMP,
301};
302
303static void sysrq_handle_showstate(u8 key)
304{
305 show_state();
306 show_all_workqueues();
307}
308static const struct sysrq_key_op sysrq_showstate_op = {
309 .handler = sysrq_handle_showstate,
310 .help_msg = "show-task-states(t)",
311 .action_msg = "Show State",
312 .enable_mask = SYSRQ_ENABLE_DUMP,
313};
314
315static void sysrq_handle_showstate_blocked(u8 key)
316{
317 show_state_filter(TASK_UNINTERRUPTIBLE);
318}
319static const struct sysrq_key_op sysrq_showstate_blocked_op = {
320 .handler = sysrq_handle_showstate_blocked,
321 .help_msg = "show-blocked-tasks(w)",
322 .action_msg = "Show Blocked State",
323 .enable_mask = SYSRQ_ENABLE_DUMP,
324};
325
326#ifdef CONFIG_TRACING
327#include <linux/ftrace.h>
328
329static void sysrq_ftrace_dump(u8 key)
330{
331 ftrace_dump(oops_dump_mode: DUMP_ALL);
332}
333static const struct sysrq_key_op sysrq_ftrace_dump_op = {
334 .handler = sysrq_ftrace_dump,
335 .help_msg = "dump-ftrace-buffer(z)",
336 .action_msg = "Dump ftrace buffer",
337 .enable_mask = SYSRQ_ENABLE_DUMP,
338};
339#else
340#define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
341#endif
342
343static void sysrq_handle_showmem(u8 key)
344{
345 show_mem();
346}
347static const struct sysrq_key_op sysrq_showmem_op = {
348 .handler = sysrq_handle_showmem,
349 .help_msg = "show-memory-usage(m)",
350 .action_msg = "Show Memory",
351 .enable_mask = SYSRQ_ENABLE_DUMP,
352};
353
354/*
355 * Signal sysrq helper function. Sends a signal to all user processes.
356 */
357static void send_sig_all(int sig)
358{
359 struct task_struct *p;
360
361 read_lock(&tasklist_lock);
362 for_each_process(p) {
363 if (p->flags & PF_KTHREAD)
364 continue;
365 if (is_global_init(tsk: p))
366 continue;
367
368 do_send_sig_info(sig, SEND_SIG_PRIV, p, type: PIDTYPE_MAX);
369 }
370 read_unlock(&tasklist_lock);
371}
372
373static void sysrq_handle_term(u8 key)
374{
375 send_sig_all(SIGTERM);
376 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
377}
378static const struct sysrq_key_op sysrq_term_op = {
379 .handler = sysrq_handle_term,
380 .help_msg = "terminate-all-tasks(e)",
381 .action_msg = "Terminate All Tasks",
382 .enable_mask = SYSRQ_ENABLE_SIGNAL,
383};
384
385static void moom_callback(struct work_struct *ignored)
386{
387 const gfp_t gfp_mask = GFP_KERNEL;
388 struct oom_control oc = {
389 .zonelist = node_zonelist(first_memory_node, flags: 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: &oc))
398 pr_info("OOM request ignored. No task eligible\n");
399 mutex_unlock(lock: &oom_lock);
400}
401
402static DECLARE_WORK(moom_work, moom_callback);
403
404static void sysrq_handle_moom(u8 key)
405{
406 schedule_work(work: &moom_work);
407}
408static const struct sysrq_key_op sysrq_moom_op = {
409 .handler = sysrq_handle_moom,
410 .help_msg = "memory-full-oom-kill(f)",
411 .action_msg = "Manual OOM execution",
412 .enable_mask = SYSRQ_ENABLE_SIGNAL,
413};
414
415#ifdef CONFIG_BLOCK
416static void sysrq_handle_thaw(u8 key)
417{
418 emergency_thaw_all();
419}
420static const struct sysrq_key_op sysrq_thaw_op = {
421 .handler = sysrq_handle_thaw,
422 .help_msg = "thaw-filesystems(j)",
423 .action_msg = "Emergency Thaw of all frozen filesystems",
424 .enable_mask = SYSRQ_ENABLE_SIGNAL,
425};
426#else
427#define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL)
428#endif
429
430static void sysrq_handle_kill(u8 key)
431{
432 send_sig_all(SIGKILL);
433 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
434}
435static const struct sysrq_key_op sysrq_kill_op = {
436 .handler = sysrq_handle_kill,
437 .help_msg = "kill-all-tasks(i)",
438 .action_msg = "Kill All Tasks",
439 .enable_mask = SYSRQ_ENABLE_SIGNAL,
440};
441
442static void sysrq_handle_unrt(u8 key)
443{
444 normalize_rt_tasks();
445}
446static const struct sysrq_key_op sysrq_unrt_op = {
447 .handler = sysrq_handle_unrt,
448 .help_msg = "nice-all-RT-tasks(n)",
449 .action_msg = "Nice All RT Tasks",
450 .enable_mask = SYSRQ_ENABLE_RTNICE,
451};
452
453static void sysrq_handle_replay_logs(u8 key)
454{
455 console_try_replay_all();
456}
457static struct sysrq_key_op sysrq_replay_logs_op = {
458 .handler = sysrq_handle_replay_logs,
459 .help_msg = "replay-kernel-logs(R)",
460 .action_msg = "Replay kernel logs on consoles",
461 .enable_mask = SYSRQ_ENABLE_DUMP,
462};
463
464/* Key Operations table and lock */
465static DEFINE_SPINLOCK(sysrq_key_table_lock);
466
467static const struct sysrq_key_op *sysrq_key_table[62] = {
468 &sysrq_loglevel_op, /* 0 */
469 &sysrq_loglevel_op, /* 1 */
470 &sysrq_loglevel_op, /* 2 */
471 &sysrq_loglevel_op, /* 3 */
472 &sysrq_loglevel_op, /* 4 */
473 &sysrq_loglevel_op, /* 5 */
474 &sysrq_loglevel_op, /* 6 */
475 &sysrq_loglevel_op, /* 7 */
476 &sysrq_loglevel_op, /* 8 */
477 &sysrq_loglevel_op, /* 9 */
478
479 /*
480 * a: Don't use for system provided sysrqs, it is handled specially on
481 * sparc and will never arrive.
482 */
483 NULL, /* a */
484 &sysrq_reboot_op, /* b */
485 &sysrq_crash_op, /* c */
486 &sysrq_showlocks_op, /* d */
487 &sysrq_term_op, /* e */
488 &sysrq_moom_op, /* f */
489 /* g: May be registered for the kernel debugger */
490 NULL, /* g */
491 NULL, /* h - reserved for help */
492 &sysrq_kill_op, /* i */
493 &sysrq_thaw_op, /* j */
494 &sysrq_SAK_op, /* k */
495 &sysrq_showallcpus_op, /* l */
496 &sysrq_showmem_op, /* m */
497 &sysrq_unrt_op, /* n */
498 /* o: This will often be registered as 'Off' at init time */
499 NULL, /* o */
500 &sysrq_showregs_op, /* p */
501 &sysrq_show_timers_op, /* q */
502 &sysrq_unraw_op, /* r */
503 &sysrq_sync_op, /* s */
504 &sysrq_showstate_op, /* t */
505 &sysrq_mountro_op, /* u */
506 /* v: May be registered for frame buffer console restore */
507 NULL, /* v */
508 &sysrq_showstate_blocked_op, /* w */
509 /* x: May be registered on mips for TLB dump */
510 /* x: May be registered on ppc/powerpc for xmon */
511 /* x: May be registered on sparc64 for global PMU dump */
512 NULL, /* x */
513 /* y: May be registered on sparc64 for global register dump */
514 NULL, /* y */
515 &sysrq_ftrace_dump_op, /* z */
516 NULL, /* A */
517 NULL, /* B */
518 NULL, /* C */
519 NULL, /* D */
520 NULL, /* E */
521 NULL, /* F */
522 NULL, /* G */
523 NULL, /* H */
524 NULL, /* I */
525 NULL, /* J */
526 NULL, /* K */
527 NULL, /* L */
528 NULL, /* M */
529 NULL, /* N */
530 NULL, /* O */
531 NULL, /* P */
532 NULL, /* Q */
533 &sysrq_replay_logs_op, /* R */
534 /* S: May be registered by sched_ext for resetting */
535 NULL, /* S */
536 NULL, /* T */
537 NULL, /* U */
538 NULL, /* V */
539 NULL, /* W */
540 NULL, /* X */
541 NULL, /* Y */
542 NULL, /* Z */
543};
544
545/* key2index calculation, -1 on invalid index */
546static int sysrq_key_table_key2index(u8 key)
547{
548 switch (key) {
549 case '0' ... '9':
550 return key - '0';
551 case 'a' ... 'z':
552 return key - 'a' + 10;
553 case 'A' ... 'Z':
554 return key - 'A' + 10 + 26;
555 default:
556 return -1;
557 }
558}
559
560/*
561 * get and put functions for the table, exposed to modules.
562 */
563static const struct sysrq_key_op *__sysrq_get_key_op(u8 key)
564{
565 const struct sysrq_key_op *op_p = NULL;
566 int i;
567
568 i = sysrq_key_table_key2index(key);
569 if (i != -1)
570 op_p = sysrq_key_table[i];
571
572 return op_p;
573}
574
575static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p)
576{
577 int i = sysrq_key_table_key2index(key);
578
579 if (i != -1)
580 sysrq_key_table[i] = op_p;
581}
582
583void __handle_sysrq(u8 key, bool check_mask)
584{
585 const struct sysrq_key_op *op_p;
586 int orig_suppress_printk;
587 int i;
588
589 orig_suppress_printk = suppress_printk;
590 suppress_printk = 0;
591
592 rcu_sysrq_start();
593 rcu_read_lock();
594 /*
595 * Enter in the force_console context so that sysrq header is shown to
596 * provide the user with positive feedback. We do not simply emit this
597 * at KERN_EMERG as that would change message routing in the consumers
598 * of /proc/kmsg.
599 */
600 printk_force_console_enter();
601
602 op_p = __sysrq_get_key_op(key);
603 if (op_p) {
604 /*
605 * Should we check for enabled operations (/proc/sysrq-trigger
606 * should not) and is the invoked operation enabled?
607 */
608 if (!check_mask || sysrq_on_mask(mask: op_p->enable_mask)) {
609 pr_info("%s\n", op_p->action_msg);
610 printk_force_console_exit();
611 op_p->handler(key);
612 } else {
613 pr_info("This sysrq operation is disabled.\n");
614 printk_force_console_exit();
615 }
616 } else {
617 pr_info("HELP : ");
618 /* Only print the help msg once per handler */
619 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
620 if (sysrq_key_table[i]) {
621 int j;
622
623 for (j = 0; sysrq_key_table[i] !=
624 sysrq_key_table[j]; j++)
625 ;
626 if (j != i)
627 continue;
628 pr_cont("%s ", sysrq_key_table[i]->help_msg);
629 }
630 }
631 pr_cont("\n");
632 printk_force_console_exit();
633 }
634 rcu_read_unlock();
635 rcu_sysrq_end();
636
637 suppress_printk = orig_suppress_printk;
638}
639
640void handle_sysrq(u8 key)
641{
642 if (sysrq_on())
643 __handle_sysrq(key, check_mask: true);
644}
645EXPORT_SYMBOL(handle_sysrq);
646
647#ifdef CONFIG_INPUT
648static int sysrq_reset_downtime_ms;
649
650/* Simple translation table for the SysRq keys */
651static const unsigned char sysrq_xlate[KEY_CNT] =
652 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
653 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
654 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
655 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
656 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
657 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
658 "\r\000/"; /* 0x60 - 0x6f */
659
660struct sysrq_state {
661 struct input_handle handle;
662 struct work_struct reinject_work;
663 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
664 unsigned int alt;
665 unsigned int alt_use;
666 unsigned int shift;
667 unsigned int shift_use;
668 bool active;
669 bool need_reinject;
670 bool reinjecting;
671
672 /* reset sequence handling */
673 bool reset_canceled;
674 bool reset_requested;
675 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
676 int reset_seq_len;
677 int reset_seq_cnt;
678 int reset_seq_version;
679 struct timer_list keyreset_timer;
680};
681
682#define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
683static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
684static unsigned int sysrq_reset_seq_len;
685static unsigned int sysrq_reset_seq_version = 1;
686
687static void sysrq_parse_reset_sequence(struct sysrq_state *state)
688{
689 int i;
690 unsigned short key;
691
692 state->reset_seq_cnt = 0;
693
694 for (i = 0; i < sysrq_reset_seq_len; i++) {
695 key = sysrq_reset_seq[i];
696
697 if (key == KEY_RESERVED || key > KEY_MAX)
698 break;
699
700 __set_bit(key, state->reset_keybit);
701 state->reset_seq_len++;
702
703 if (test_bit(key, state->key_down))
704 state->reset_seq_cnt++;
705 }
706
707 /* Disable reset until old keys are not released */
708 state->reset_canceled = state->reset_seq_cnt != 0;
709
710 state->reset_seq_version = sysrq_reset_seq_version;
711}
712
713static void sysrq_do_reset(struct timer_list *t)
714{
715 struct sysrq_state *state = timer_container_of(state, t,
716 keyreset_timer);
717
718 state->reset_requested = true;
719
720 orderly_reboot();
721}
722
723static void sysrq_handle_reset_request(struct sysrq_state *state)
724{
725 if (state->reset_requested)
726 __handle_sysrq(key: sysrq_xlate[KEY_B], check_mask: false);
727
728 if (sysrq_reset_downtime_ms)
729 mod_timer(timer: &state->keyreset_timer,
730 expires: jiffies + msecs_to_jiffies(m: sysrq_reset_downtime_ms));
731 else
732 sysrq_do_reset(t: &state->keyreset_timer);
733}
734
735static void sysrq_detect_reset_sequence(struct sysrq_state *state,
736 unsigned int code, int value)
737{
738 if (!test_bit(code, state->reset_keybit)) {
739 /*
740 * Pressing any key _not_ in reset sequence cancels
741 * the reset sequence. Also cancelling the timer in
742 * case additional keys were pressed after a reset
743 * has been requested.
744 */
745 if (value && state->reset_seq_cnt) {
746 state->reset_canceled = true;
747 timer_delete(timer: &state->keyreset_timer);
748 }
749 } else if (value == 0) {
750 /*
751 * Key release - all keys in the reset sequence need
752 * to be pressed and held for the reset timeout
753 * to hold.
754 */
755 timer_delete(timer: &state->keyreset_timer);
756
757 if (--state->reset_seq_cnt == 0)
758 state->reset_canceled = false;
759 } else if (value == 1) {
760 /* key press, not autorepeat */
761 if (++state->reset_seq_cnt == state->reset_seq_len &&
762 !state->reset_canceled) {
763 sysrq_handle_reset_request(state);
764 }
765 }
766}
767
768#ifdef CONFIG_OF
769static void sysrq_of_get_keyreset_config(void)
770{
771 u32 key;
772 struct device_node *np;
773
774 np = of_find_node_by_path(path: "/chosen/linux,sysrq-reset-seq");
775 if (!np) {
776 pr_debug("No sysrq node found");
777 return;
778 }
779
780 /* Reset in case a __weak definition was present */
781 sysrq_reset_seq_len = 0;
782
783 of_property_for_each_u32(np, "keyset", key) {
784 if (key == KEY_RESERVED || key > KEY_MAX ||
785 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
786 break;
787
788 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
789 }
790
791 /* Get reset timeout if any. */
792 of_property_read_u32(np, propname: "timeout-ms", out_value: &sysrq_reset_downtime_ms);
793
794 of_node_put(node: np);
795}
796#else
797static void sysrq_of_get_keyreset_config(void)
798{
799}
800#endif
801
802static void sysrq_reinject_alt_sysrq(struct work_struct *work)
803{
804 struct sysrq_state *sysrq =
805 container_of(work, struct sysrq_state, reinject_work);
806 struct input_handle *handle = &sysrq->handle;
807 unsigned int alt_code = sysrq->alt_use;
808
809 if (sysrq->need_reinject) {
810 /* we do not want the assignment to be reordered */
811 sysrq->reinjecting = true;
812 mb();
813
814 /* Simulate press and release of Alt + SysRq */
815 input_inject_event(handle, EV_KEY, code: alt_code, value: 1);
816 input_inject_event(handle, EV_KEY, KEY_SYSRQ, value: 1);
817 input_inject_event(handle, EV_SYN, SYN_REPORT, value: 1);
818
819 input_inject_event(handle, EV_KEY, KEY_SYSRQ, value: 0);
820 input_inject_event(handle, EV_KEY, code: alt_code, value: 0);
821 input_inject_event(handle, EV_SYN, SYN_REPORT, value: 1);
822
823 mb();
824 sysrq->reinjecting = false;
825 }
826}
827
828static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
829 unsigned int code, int value)
830{
831 bool was_active = sysrq->active;
832 bool suppress;
833
834 switch (code) {
835
836 case KEY_LEFTALT:
837 case KEY_RIGHTALT:
838 if (!value) {
839 /* One of ALTs is being released */
840 if (sysrq->active && code == sysrq->alt_use)
841 sysrq->active = false;
842
843 sysrq->alt = KEY_RESERVED;
844
845 } else if (value != 2) {
846 sysrq->alt = code;
847 sysrq->need_reinject = false;
848 }
849 break;
850
851 case KEY_LEFTSHIFT:
852 case KEY_RIGHTSHIFT:
853 if (!value)
854 sysrq->shift = KEY_RESERVED;
855 else if (value != 2)
856 sysrq->shift = code;
857 if (sysrq->active)
858 sysrq->shift_use = sysrq->shift;
859 break;
860
861 case KEY_SYSRQ:
862 if (value == 1 && sysrq->alt != KEY_RESERVED) {
863 sysrq->active = true;
864 sysrq->alt_use = sysrq->alt;
865 /* either RESERVED (for released) or actual code */
866 sysrq->shift_use = sysrq->shift;
867 /*
868 * If nothing else will be pressed we'll need
869 * to re-inject Alt-SysRq keysroke.
870 */
871 sysrq->need_reinject = true;
872 }
873
874 /*
875 * Pretend that sysrq was never pressed at all. This
876 * is needed to properly handle KGDB which will try
877 * to release all keys after exiting debugger. If we
878 * do not clear key bit it KGDB will end up sending
879 * release events for Alt and SysRq, potentially
880 * triggering print screen function.
881 */
882 if (sysrq->active)
883 clear_bit(KEY_SYSRQ, addr: sysrq->handle.dev->key);
884
885 break;
886
887 default:
888 if (sysrq->active && value && value != 2) {
889 unsigned char c = sysrq_xlate[code];
890
891 sysrq->need_reinject = false;
892 if (sysrq->shift_use != KEY_RESERVED)
893 c = toupper(c);
894 __handle_sysrq(key: c, check_mask: true);
895 }
896 break;
897 }
898
899 suppress = sysrq->active;
900
901 if (!sysrq->active) {
902
903 /*
904 * See if reset sequence has changed since the last time.
905 */
906 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
907 sysrq_parse_reset_sequence(state: sysrq);
908
909 /*
910 * If we are not suppressing key presses keep track of
911 * keyboard state so we can release keys that have been
912 * pressed before entering SysRq mode.
913 */
914 if (value)
915 set_bit(nr: code, addr: sysrq->key_down);
916 else
917 clear_bit(nr: code, addr: sysrq->key_down);
918
919 if (was_active)
920 schedule_work(work: &sysrq->reinject_work);
921
922 /* Check for reset sequence */
923 sysrq_detect_reset_sequence(state: sysrq, code, value);
924
925 } else if (value == 0 && test_and_clear_bit(nr: code, addr: sysrq->key_down)) {
926 /*
927 * Pass on release events for keys that was pressed before
928 * entering SysRq mode.
929 */
930 suppress = false;
931 }
932
933 return suppress;
934}
935
936static bool sysrq_filter(struct input_handle *handle,
937 unsigned int type, unsigned int code, int value)
938{
939 struct sysrq_state *sysrq = handle->private;
940 bool suppress;
941
942 /*
943 * Do not filter anything if we are in the process of re-injecting
944 * Alt+SysRq combination.
945 */
946 if (sysrq->reinjecting)
947 return false;
948
949 switch (type) {
950
951 case EV_SYN:
952 suppress = false;
953 break;
954
955 case EV_KEY:
956 suppress = sysrq_handle_keypress(sysrq, code, value);
957 break;
958
959 default:
960 suppress = sysrq->active;
961 break;
962 }
963
964 return suppress;
965}
966
967static int sysrq_connect(struct input_handler *handler,
968 struct input_dev *dev,
969 const struct input_device_id *id)
970{
971 struct sysrq_state *sysrq;
972 int error;
973
974 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
975 if (!sysrq)
976 return -ENOMEM;
977
978 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
979
980 sysrq->handle.dev = dev;
981 sysrq->handle.handler = handler;
982 sysrq->handle.name = "sysrq";
983 sysrq->handle.private = sysrq;
984 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
985
986 error = input_register_handle(&sysrq->handle);
987 if (error) {
988 pr_err("Failed to register input sysrq handler, error %d\n",
989 error);
990 goto err_free;
991 }
992
993 error = input_open_device(&sysrq->handle);
994 if (error) {
995 pr_err("Failed to open input device, error %d\n", error);
996 goto err_unregister;
997 }
998
999 return 0;
1000
1001 err_unregister:
1002 input_unregister_handle(&sysrq->handle);
1003 err_free:
1004 kfree(objp: sysrq);
1005 return error;
1006}
1007
1008static void sysrq_disconnect(struct input_handle *handle)
1009{
1010 struct sysrq_state *sysrq = handle->private;
1011
1012 input_close_device(handle);
1013 cancel_work_sync(work: &sysrq->reinject_work);
1014 timer_shutdown_sync(timer: &sysrq->keyreset_timer);
1015 input_unregister_handle(handle);
1016 kfree(objp: sysrq);
1017}
1018
1019/*
1020 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1021 * keyboards have SysRq key predefined and so user may add it to keymap
1022 * later, but we expect all such keyboards to have left alt.
1023 */
1024static const struct input_device_id sysrq_ids[] = {
1025 {
1026 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1027 INPUT_DEVICE_ID_MATCH_KEYBIT,
1028 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1029 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1030 },
1031 { },
1032};
1033
1034static struct input_handler sysrq_handler = {
1035 .filter = sysrq_filter,
1036 .connect = sysrq_connect,
1037 .disconnect = sysrq_disconnect,
1038 .name = "sysrq",
1039 .id_table = sysrq_ids,
1040};
1041
1042static inline void sysrq_register_handler(void)
1043{
1044 int error;
1045
1046 sysrq_of_get_keyreset_config();
1047
1048 error = input_register_handler(&sysrq_handler);
1049 if (error)
1050 pr_err("Failed to register input handler, error %d", error);
1051}
1052
1053static inline void sysrq_unregister_handler(void)
1054{
1055 input_unregister_handler(&sysrq_handler);
1056}
1057
1058static int sysrq_reset_seq_param_set(const char *buffer,
1059 const struct kernel_param *kp)
1060{
1061 unsigned long val;
1062 int error;
1063
1064 error = kstrtoul(s: buffer, base: 0, res: &val);
1065 if (error < 0)
1066 return error;
1067
1068 if (val > KEY_MAX)
1069 return -EINVAL;
1070
1071 *((unsigned short *)kp->arg) = val;
1072 sysrq_reset_seq_version++;
1073
1074 return 0;
1075}
1076
1077static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1078 .get = param_get_ushort,
1079 .set = sysrq_reset_seq_param_set,
1080};
1081
1082#define param_check_sysrq_reset_seq(name, p) \
1083 __param_check(name, p, unsigned short)
1084
1085/*
1086 * not really modular, but the easiest way to keep compat with existing
1087 * bootargs behaviour is to continue using module_param here.
1088 */
1089module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1090 &sysrq_reset_seq_len, 0644);
1091
1092module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1093
1094#else
1095
1096static inline void sysrq_register_handler(void)
1097{
1098}
1099
1100static inline void sysrq_unregister_handler(void)
1101{
1102}
1103
1104#endif /* CONFIG_INPUT */
1105
1106int sysrq_toggle_support(int enable_mask)
1107{
1108 bool was_enabled = sysrq_on();
1109
1110 sysrq_enabled = enable_mask;
1111
1112 if (was_enabled != sysrq_on()) {
1113 if (sysrq_on())
1114 sysrq_register_handler();
1115 else
1116 sysrq_unregister_handler();
1117 }
1118
1119 return 0;
1120}
1121EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1122
1123static int sysrq_sysctl_handler(const struct ctl_table *table, int write,
1124 void *buffer, size_t *lenp, loff_t *ppos)
1125{
1126 int tmp, ret;
1127 struct ctl_table t = *table;
1128
1129 tmp = sysrq_mask();
1130 t.data = &tmp;
1131
1132 /*
1133 * Behaves like do_proc_dointvec as t does not have min nor max.
1134 */
1135 ret = proc_dointvec_minmax(table: &t, dir: write, buffer, lenp, ppos);
1136 if (ret)
1137 return ret;
1138
1139 if (write)
1140 sysrq_toggle_support(tmp);
1141
1142 return 0;
1143}
1144
1145static const struct ctl_table sysrq_sysctl_table[] = {
1146 {
1147 .procname = "sysrq",
1148 .data = NULL,
1149 .maxlen = sizeof(int),
1150 .mode = 0644,
1151 .proc_handler = sysrq_sysctl_handler,
1152 },
1153};
1154
1155static int __init init_sysrq_sysctl(void)
1156{
1157 register_sysctl_init("kernel", sysrq_sysctl_table);
1158 return 0;
1159}
1160
1161subsys_initcall(init_sysrq_sysctl);
1162
1163static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p,
1164 const struct sysrq_key_op *remove_op_p)
1165{
1166 int retval;
1167
1168 spin_lock(lock: &sysrq_key_table_lock);
1169 if (__sysrq_get_key_op(key) == remove_op_p) {
1170 __sysrq_put_key_op(key, op_p: insert_op_p);
1171 retval = 0;
1172 } else {
1173 retval = -1;
1174 }
1175 spin_unlock(lock: &sysrq_key_table_lock);
1176
1177 /*
1178 * A concurrent __handle_sysrq either got the old op or the new op.
1179 * Wait for it to go away before returning, so the code for an old
1180 * op is not freed (eg. on module unload) while it is in use.
1181 */
1182 synchronize_rcu();
1183
1184 return retval;
1185}
1186
1187int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1188{
1189 return __sysrq_swap_key_ops(key, insert_op_p: op_p, NULL);
1190}
1191EXPORT_SYMBOL(register_sysrq_key);
1192
1193int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1194{
1195 return __sysrq_swap_key_ops(key, NULL, remove_op_p: op_p);
1196}
1197EXPORT_SYMBOL(unregister_sysrq_key);
1198
1199#ifdef CONFIG_PROC_FS
1200/*
1201 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1202 * Normally, only the first character written is processed.
1203 * However, if the first character is an underscore,
1204 * all characters are processed.
1205 */
1206static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1207 size_t count, loff_t *ppos)
1208{
1209 bool bulk = false;
1210 size_t i;
1211
1212 for (i = 0; i < count; i++) {
1213 char c;
1214
1215 if (get_user(c, buf + i))
1216 return -EFAULT;
1217
1218 if (c == '_')
1219 bulk = true;
1220 else
1221 __handle_sysrq(key: c, check_mask: false);
1222
1223 if (!bulk)
1224 break;
1225 }
1226
1227 return count;
1228}
1229
1230static const struct proc_ops sysrq_trigger_proc_ops = {
1231 .proc_write = write_sysrq_trigger,
1232 .proc_lseek = noop_llseek,
1233};
1234
1235static void sysrq_init_procfs(void)
1236{
1237 if (!proc_create(name: "sysrq-trigger", S_IWUSR, NULL,
1238 proc_ops: &sysrq_trigger_proc_ops))
1239 pr_err("Failed to register proc interface\n");
1240}
1241
1242#else
1243
1244static inline void sysrq_init_procfs(void)
1245{
1246}
1247
1248#endif /* CONFIG_PROC_FS */
1249
1250static int __init sysrq_init(void)
1251{
1252 sysrq_init_procfs();
1253
1254 if (sysrq_on())
1255 sysrq_register_handler();
1256
1257 return 0;
1258}
1259device_initcall(sysrq_init);
1260

source code of linux/drivers/tty/sysrq.c