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