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