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(u8 key)103 static void sysrq_handle_loglevel(u8 key)
104 {
105 u8 loglevel = key - '0';
106
107 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
108 pr_info("Loglevel set to %u\n", loglevel);
109 console_loglevel = loglevel;
110 }
111 static const struct sysrq_key_op sysrq_loglevel_op = {
112 .handler = sysrq_handle_loglevel,
113 .help_msg = "loglevel(0-9)",
114 .action_msg = "Changing Loglevel",
115 .enable_mask = SYSRQ_ENABLE_LOG,
116 };
117
118 #ifdef CONFIG_VT
sysrq_handle_SAK(u8 key)119 static void sysrq_handle_SAK(u8 key)
120 {
121 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
122
123 schedule_work(SAK_work);
124 }
125 static const struct sysrq_key_op sysrq_SAK_op = {
126 .handler = sysrq_handle_SAK,
127 .help_msg = "sak(k)",
128 .action_msg = "SAK",
129 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
130 };
131 #else
132 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
133 #endif
134
135 #ifdef CONFIG_VT
sysrq_handle_unraw(u8 key)136 static void sysrq_handle_unraw(u8 key)
137 {
138 vt_reset_unicode(fg_console);
139 }
140
141 static const struct sysrq_key_op sysrq_unraw_op = {
142 .handler = sysrq_handle_unraw,
143 .help_msg = "unraw(r)",
144 .action_msg = "Keyboard mode set to system default",
145 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
146 };
147 #else
148 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
149 #endif /* CONFIG_VT */
150
sysrq_handle_crash(u8 key)151 static void sysrq_handle_crash(u8 key)
152 {
153 /* release the RCU read lock before crashing */
154 rcu_read_unlock();
155
156 trace_android_vh_sysrq_crash(current);
157
158 panic("sysrq triggered crash\n");
159 }
160 static const struct sysrq_key_op sysrq_crash_op = {
161 .handler = sysrq_handle_crash,
162 .help_msg = "crash(c)",
163 .action_msg = "Trigger a crash",
164 .enable_mask = SYSRQ_ENABLE_DUMP,
165 };
166
sysrq_handle_reboot(u8 key)167 static void sysrq_handle_reboot(u8 key)
168 {
169 lockdep_off();
170 local_irq_enable();
171 emergency_restart();
172 }
173 static const struct sysrq_key_op sysrq_reboot_op = {
174 .handler = sysrq_handle_reboot,
175 .help_msg = "reboot(b)",
176 .action_msg = "Resetting",
177 .enable_mask = SYSRQ_ENABLE_BOOT,
178 };
179
180 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
181
sysrq_handle_sync(u8 key)182 static void sysrq_handle_sync(u8 key)
183 {
184 emergency_sync();
185 }
186 static const struct sysrq_key_op sysrq_sync_op = {
187 .handler = sysrq_handle_sync,
188 .help_msg = "sync(s)",
189 .action_msg = "Emergency Sync",
190 .enable_mask = SYSRQ_ENABLE_SYNC,
191 };
192
sysrq_handle_show_timers(u8 key)193 static void sysrq_handle_show_timers(u8 key)
194 {
195 sysrq_timer_list_show();
196 }
197
198 static const struct sysrq_key_op sysrq_show_timers_op = {
199 .handler = sysrq_handle_show_timers,
200 .help_msg = "show-all-timers(q)",
201 .action_msg = "Show clockevent devices & pending hrtimers (no others)",
202 };
203
sysrq_handle_mountro(u8 key)204 static void sysrq_handle_mountro(u8 key)
205 {
206 emergency_remount();
207 }
208 static const struct sysrq_key_op sysrq_mountro_op = {
209 .handler = sysrq_handle_mountro,
210 .help_msg = "unmount(u)",
211 .action_msg = "Emergency Remount R/O",
212 .enable_mask = SYSRQ_ENABLE_REMOUNT,
213 };
214
215 #ifdef CONFIG_LOCKDEP
sysrq_handle_showlocks(u8 key)216 static void sysrq_handle_showlocks(u8 key)
217 {
218 debug_show_all_locks();
219 }
220
221 static const struct sysrq_key_op sysrq_showlocks_op = {
222 .handler = sysrq_handle_showlocks,
223 .help_msg = "show-all-locks(d)",
224 .action_msg = "Show Locks Held",
225 };
226 #else
227 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
228 #endif
229
230 #ifdef CONFIG_SMP
231 static DEFINE_RAW_SPINLOCK(show_lock);
232
showacpu(void * dummy)233 static void showacpu(void *dummy)
234 {
235 unsigned long flags;
236
237 /* Idle CPUs have no interesting backtrace. */
238 if (idle_cpu(smp_processor_id())) {
239 pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
240 return;
241 }
242
243 raw_spin_lock_irqsave(&show_lock, flags);
244 pr_info("CPU%d:\n", smp_processor_id());
245 show_stack(NULL, NULL, KERN_INFO);
246 raw_spin_unlock_irqrestore(&show_lock, flags);
247 }
248
sysrq_showregs_othercpus(struct work_struct * dummy)249 static void sysrq_showregs_othercpus(struct work_struct *dummy)
250 {
251 smp_call_function(showacpu, NULL, 0);
252 }
253
254 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
255
sysrq_handle_showallcpus(u8 key)256 static void sysrq_handle_showallcpus(u8 key)
257 {
258 /*
259 * Fall back to the workqueue based printing if the
260 * backtrace printing did not succeed or the
261 * architecture has no support for it:
262 */
263 if (!trigger_all_cpu_backtrace()) {
264 struct pt_regs *regs = NULL;
265
266 if (in_hardirq())
267 regs = get_irq_regs();
268
269 pr_info("CPU%d:\n", get_cpu());
270 if (regs)
271 show_regs(regs);
272 else
273 show_stack(NULL, NULL, KERN_INFO);
274
275 schedule_work(&sysrq_showallcpus);
276 put_cpu();
277 }
278 }
279
280 static const struct sysrq_key_op sysrq_showallcpus_op = {
281 .handler = sysrq_handle_showallcpus,
282 .help_msg = "show-backtrace-all-active-cpus(l)",
283 .action_msg = "Show backtrace of all active CPUs",
284 .enable_mask = SYSRQ_ENABLE_DUMP,
285 };
286 #else
287 #define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL)
288 #endif
289
sysrq_handle_showregs(u8 key)290 static void sysrq_handle_showregs(u8 key)
291 {
292 struct pt_regs *regs = NULL;
293
294 if (in_hardirq())
295 regs = get_irq_regs();
296 if (regs)
297 show_regs(regs);
298 perf_event_print_debug();
299 }
300 static const struct sysrq_key_op sysrq_showregs_op = {
301 .handler = sysrq_handle_showregs,
302 .help_msg = "show-registers(p)",
303 .action_msg = "Show Regs",
304 .enable_mask = SYSRQ_ENABLE_DUMP,
305 };
306
sysrq_handle_showstate(u8 key)307 static void sysrq_handle_showstate(u8 key)
308 {
309 show_state();
310 show_all_workqueues();
311 }
312 static const struct sysrq_key_op sysrq_showstate_op = {
313 .handler = sysrq_handle_showstate,
314 .help_msg = "show-task-states(t)",
315 .action_msg = "Show State",
316 .enable_mask = SYSRQ_ENABLE_DUMP,
317 };
318
sysrq_handle_showstate_blocked(u8 key)319 static void sysrq_handle_showstate_blocked(u8 key)
320 {
321 show_state_filter(TASK_UNINTERRUPTIBLE);
322 }
323 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
324 .handler = sysrq_handle_showstate_blocked,
325 .help_msg = "show-blocked-tasks(w)",
326 .action_msg = "Show Blocked State",
327 .enable_mask = SYSRQ_ENABLE_DUMP,
328 };
329
330 #ifdef CONFIG_TRACING
331 #include <linux/ftrace.h>
332
sysrq_ftrace_dump(u8 key)333 static void sysrq_ftrace_dump(u8 key)
334 {
335 ftrace_dump(DUMP_ALL);
336 }
337 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
338 .handler = sysrq_ftrace_dump,
339 .help_msg = "dump-ftrace-buffer(z)",
340 .action_msg = "Dump ftrace buffer",
341 .enable_mask = SYSRQ_ENABLE_DUMP,
342 };
343 #else
344 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
345 #endif
346
sysrq_handle_showmem(u8 key)347 static void sysrq_handle_showmem(u8 key)
348 {
349 show_mem();
350 }
351 static const struct sysrq_key_op sysrq_showmem_op = {
352 .handler = sysrq_handle_showmem,
353 .help_msg = "show-memory-usage(m)",
354 .action_msg = "Show Memory",
355 .enable_mask = SYSRQ_ENABLE_DUMP,
356 };
357
358 /*
359 * Signal sysrq helper function. Sends a signal to all user processes.
360 */
send_sig_all(int sig)361 static void send_sig_all(int sig)
362 {
363 struct task_struct *p;
364
365 read_lock(&tasklist_lock);
366 for_each_process(p) {
367 if (p->flags & PF_KTHREAD)
368 continue;
369 if (is_global_init(p))
370 continue;
371
372 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
373 }
374 read_unlock(&tasklist_lock);
375 }
376
sysrq_handle_term(u8 key)377 static void sysrq_handle_term(u8 key)
378 {
379 send_sig_all(SIGTERM);
380 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
381 }
382 static const struct sysrq_key_op sysrq_term_op = {
383 .handler = sysrq_handle_term,
384 .help_msg = "terminate-all-tasks(e)",
385 .action_msg = "Terminate All Tasks",
386 .enable_mask = SYSRQ_ENABLE_SIGNAL,
387 };
388
moom_callback(struct work_struct * ignored)389 static void moom_callback(struct work_struct *ignored)
390 {
391 const gfp_t gfp_mask = GFP_KERNEL;
392 struct oom_control oc = {
393 .zonelist = node_zonelist(first_memory_node, gfp_mask),
394 .nodemask = NULL,
395 .memcg = NULL,
396 .gfp_mask = gfp_mask,
397 .order = -1,
398 };
399
400 mutex_lock(&oom_lock);
401 if (!out_of_memory(&oc))
402 pr_info("OOM request ignored. No task eligible\n");
403 mutex_unlock(&oom_lock);
404 }
405
406 static DECLARE_WORK(moom_work, moom_callback);
407
sysrq_handle_moom(u8 key)408 static void sysrq_handle_moom(u8 key)
409 {
410 schedule_work(&moom_work);
411 }
412 static const struct sysrq_key_op sysrq_moom_op = {
413 .handler = sysrq_handle_moom,
414 .help_msg = "memory-full-oom-kill(f)",
415 .action_msg = "Manual OOM execution",
416 .enable_mask = SYSRQ_ENABLE_SIGNAL,
417 };
418
419 #ifdef CONFIG_BLOCK
sysrq_handle_thaw(u8 key)420 static void sysrq_handle_thaw(u8 key)
421 {
422 emergency_thaw_all();
423 }
424 static const struct sysrq_key_op sysrq_thaw_op = {
425 .handler = sysrq_handle_thaw,
426 .help_msg = "thaw-filesystems(j)",
427 .action_msg = "Emergency Thaw of all frozen filesystems",
428 .enable_mask = SYSRQ_ENABLE_SIGNAL,
429 };
430 #else
431 #define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL)
432 #endif
433
sysrq_handle_kill(u8 key)434 static void sysrq_handle_kill(u8 key)
435 {
436 send_sig_all(SIGKILL);
437 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
438 }
439 static const struct sysrq_key_op sysrq_kill_op = {
440 .handler = sysrq_handle_kill,
441 .help_msg = "kill-all-tasks(i)",
442 .action_msg = "Kill All Tasks",
443 .enable_mask = SYSRQ_ENABLE_SIGNAL,
444 };
445
sysrq_handle_unrt(u8 key)446 static void sysrq_handle_unrt(u8 key)
447 {
448 normalize_rt_tasks();
449 }
450 static const struct sysrq_key_op sysrq_unrt_op = {
451 .handler = sysrq_handle_unrt,
452 .help_msg = "nice-all-RT-tasks(n)",
453 .action_msg = "Nice All RT Tasks",
454 .enable_mask = SYSRQ_ENABLE_RTNICE,
455 };
456
sysrq_handle_replay_logs(u8 key)457 static void sysrq_handle_replay_logs(u8 key)
458 {
459 console_try_replay_all();
460 }
461 static struct sysrq_key_op sysrq_replay_logs_op = {
462 .handler = sysrq_handle_replay_logs,
463 .help_msg = "replay-kernel-logs(R)",
464 .action_msg = "Replay kernel logs on consoles",
465 .enable_mask = SYSRQ_ENABLE_DUMP,
466 };
467
468 /* Key Operations table and lock */
469 static DEFINE_SPINLOCK(sysrq_key_table_lock);
470
471 static const struct sysrq_key_op *sysrq_key_table[62] = {
472 &sysrq_loglevel_op, /* 0 */
473 &sysrq_loglevel_op, /* 1 */
474 &sysrq_loglevel_op, /* 2 */
475 &sysrq_loglevel_op, /* 3 */
476 &sysrq_loglevel_op, /* 4 */
477 &sysrq_loglevel_op, /* 5 */
478 &sysrq_loglevel_op, /* 6 */
479 &sysrq_loglevel_op, /* 7 */
480 &sysrq_loglevel_op, /* 8 */
481 &sysrq_loglevel_op, /* 9 */
482
483 /*
484 * a: Don't use for system provided sysrqs, it is handled specially on
485 * sparc and will never arrive.
486 */
487 NULL, /* a */
488 &sysrq_reboot_op, /* b */
489 &sysrq_crash_op, /* c */
490 &sysrq_showlocks_op, /* d */
491 &sysrq_term_op, /* e */
492 &sysrq_moom_op, /* f */
493 /* g: May be registered for the kernel debugger */
494 NULL, /* g */
495 NULL, /* h - reserved for help */
496 &sysrq_kill_op, /* i */
497 &sysrq_thaw_op, /* j */
498 &sysrq_SAK_op, /* k */
499 &sysrq_showallcpus_op, /* l */
500 &sysrq_showmem_op, /* m */
501 &sysrq_unrt_op, /* n */
502 /* o: This will often be registered as 'Off' at init time */
503 NULL, /* o */
504 &sysrq_showregs_op, /* p */
505 &sysrq_show_timers_op, /* q */
506 &sysrq_unraw_op, /* r */
507 &sysrq_sync_op, /* s */
508 &sysrq_showstate_op, /* t */
509 &sysrq_mountro_op, /* u */
510 /* v: May be registered for frame buffer console restore */
511 NULL, /* v */
512 &sysrq_showstate_blocked_op, /* w */
513 /* x: May be registered on mips for TLB dump */
514 /* x: May be registered on ppc/powerpc for xmon */
515 /* x: May be registered on sparc64 for global PMU dump */
516 NULL, /* x */
517 /* y: May be registered on sparc64 for global register dump */
518 NULL, /* y */
519 &sysrq_ftrace_dump_op, /* z */
520 NULL, /* A */
521 NULL, /* B */
522 NULL, /* C */
523 NULL, /* D */
524 NULL, /* E */
525 NULL, /* F */
526 NULL, /* G */
527 NULL, /* H */
528 NULL, /* I */
529 NULL, /* J */
530 NULL, /* K */
531 NULL, /* L */
532 NULL, /* M */
533 NULL, /* N */
534 NULL, /* O */
535 NULL, /* P */
536 NULL, /* Q */
537 &sysrq_replay_logs_op, /* R */
538 /* S: May be registered by sched_ext for resetting */
539 NULL, /* S */
540 NULL, /* T */
541 NULL, /* U */
542 NULL, /* V */
543 NULL, /* W */
544 NULL, /* X */
545 NULL, /* Y */
546 NULL, /* Z */
547 };
548
549 /* key2index calculation, -1 on invalid index */
sysrq_key_table_key2index(u8 key)550 static int sysrq_key_table_key2index(u8 key)
551 {
552 switch (key) {
553 case '0' ... '9':
554 return key - '0';
555 case 'a' ... 'z':
556 return key - 'a' + 10;
557 case 'A' ... 'Z':
558 return key - 'A' + 10 + 26;
559 default:
560 return -1;
561 }
562 }
563
564 /*
565 * get and put functions for the table, exposed to modules.
566 */
__sysrq_get_key_op(u8 key)567 static const struct sysrq_key_op *__sysrq_get_key_op(u8 key)
568 {
569 const struct sysrq_key_op *op_p = NULL;
570 int i;
571
572 i = sysrq_key_table_key2index(key);
573 if (i != -1)
574 op_p = sysrq_key_table[i];
575
576 return op_p;
577 }
578
__sysrq_put_key_op(u8 key,const struct sysrq_key_op * op_p)579 static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p)
580 {
581 int i = sysrq_key_table_key2index(key);
582
583 if (i != -1)
584 sysrq_key_table[i] = op_p;
585 }
586
__handle_sysrq(u8 key,bool check_mask)587 void __handle_sysrq(u8 key, bool check_mask)
588 {
589 const struct sysrq_key_op *op_p;
590 int orig_log_level;
591 int orig_suppress_printk;
592 int i;
593
594 orig_suppress_printk = suppress_printk;
595 suppress_printk = 0;
596
597 rcu_sysrq_start();
598 rcu_read_lock();
599 /*
600 * Raise the apparent loglevel to maximum so that the sysrq header
601 * is shown to provide the user with positive feedback. We do not
602 * simply emit this at KERN_EMERG as that would change message
603 * routing in the consumers of /proc/kmsg.
604 */
605 orig_log_level = console_loglevel;
606 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
607
608 op_p = __sysrq_get_key_op(key);
609 if (op_p) {
610 /*
611 * Should we check for enabled operations (/proc/sysrq-trigger
612 * should not) and is the invoked operation enabled?
613 */
614 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
615 pr_info("%s\n", op_p->action_msg);
616 console_loglevel = orig_log_level;
617 op_p->handler(key);
618 } else {
619 pr_info("This sysrq operation is disabled.\n");
620 console_loglevel = orig_log_level;
621 }
622 } else {
623 pr_info("HELP : ");
624 /* Only print the help msg once per handler */
625 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
626 if (sysrq_key_table[i]) {
627 int j;
628
629 for (j = 0; sysrq_key_table[i] !=
630 sysrq_key_table[j]; j++)
631 ;
632 if (j != i)
633 continue;
634 pr_cont("%s ", sysrq_key_table[i]->help_msg);
635 }
636 }
637 pr_cont("\n");
638 console_loglevel = orig_log_level;
639 }
640 rcu_read_unlock();
641 rcu_sysrq_end();
642
643 suppress_printk = orig_suppress_printk;
644 }
645
handle_sysrq(u8 key)646 void handle_sysrq(u8 key)
647 {
648 if (sysrq_on())
649 __handle_sysrq(key, true);
650 }
651 EXPORT_SYMBOL(handle_sysrq);
652
653 #ifdef CONFIG_INPUT
654 static int sysrq_reset_downtime_ms;
655
656 /* Simple translation table for the SysRq keys */
657 static const unsigned char sysrq_xlate[KEY_CNT] =
658 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
659 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
660 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
661 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
662 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
663 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
664 "\r\000/"; /* 0x60 - 0x6f */
665
666 struct sysrq_state {
667 struct input_handle handle;
668 struct work_struct reinject_work;
669 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
670 unsigned int alt;
671 unsigned int alt_use;
672 unsigned int shift;
673 unsigned int shift_use;
674 bool active;
675 bool need_reinject;
676 bool reinjecting;
677
678 /* reset sequence handling */
679 bool reset_canceled;
680 bool reset_requested;
681 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
682 int reset_seq_len;
683 int reset_seq_cnt;
684 int reset_seq_version;
685 struct timer_list keyreset_timer;
686 };
687
688 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
689 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
690 static unsigned int sysrq_reset_seq_len;
691 static unsigned int sysrq_reset_seq_version = 1;
692
sysrq_parse_reset_sequence(struct sysrq_state * state)693 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
694 {
695 int i;
696 unsigned short key;
697
698 state->reset_seq_cnt = 0;
699
700 for (i = 0; i < sysrq_reset_seq_len; i++) {
701 key = sysrq_reset_seq[i];
702
703 if (key == KEY_RESERVED || key > KEY_MAX)
704 break;
705
706 __set_bit(key, state->reset_keybit);
707 state->reset_seq_len++;
708
709 if (test_bit(key, state->key_down))
710 state->reset_seq_cnt++;
711 }
712
713 /* Disable reset until old keys are not released */
714 state->reset_canceled = state->reset_seq_cnt != 0;
715
716 state->reset_seq_version = sysrq_reset_seq_version;
717 }
718
sysrq_do_reset(struct timer_list * t)719 static void sysrq_do_reset(struct timer_list *t)
720 {
721 struct sysrq_state *state = from_timer(state, t, keyreset_timer);
722
723 state->reset_requested = true;
724
725 orderly_reboot();
726 }
727
sysrq_handle_reset_request(struct sysrq_state * state)728 static void sysrq_handle_reset_request(struct sysrq_state *state)
729 {
730 if (state->reset_requested)
731 __handle_sysrq(sysrq_xlate[KEY_B], false);
732
733 if (sysrq_reset_downtime_ms)
734 mod_timer(&state->keyreset_timer,
735 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
736 else
737 sysrq_do_reset(&state->keyreset_timer);
738 }
739
sysrq_detect_reset_sequence(struct sysrq_state * state,unsigned int code,int value)740 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
741 unsigned int code, int value)
742 {
743 if (!test_bit(code, state->reset_keybit)) {
744 /*
745 * Pressing any key _not_ in reset sequence cancels
746 * the reset sequence. Also cancelling the timer in
747 * case additional keys were pressed after a reset
748 * has been requested.
749 */
750 if (value && state->reset_seq_cnt) {
751 state->reset_canceled = true;
752 del_timer(&state->keyreset_timer);
753 }
754 } else if (value == 0) {
755 /*
756 * Key release - all keys in the reset sequence need
757 * to be pressed and held for the reset timeout
758 * to hold.
759 */
760 del_timer(&state->keyreset_timer);
761
762 if (--state->reset_seq_cnt == 0)
763 state->reset_canceled = false;
764 } else if (value == 1) {
765 /* key press, not autorepeat */
766 if (++state->reset_seq_cnt == state->reset_seq_len &&
767 !state->reset_canceled) {
768 sysrq_handle_reset_request(state);
769 }
770 }
771 }
772
773 #ifdef CONFIG_OF
sysrq_of_get_keyreset_config(void)774 static void sysrq_of_get_keyreset_config(void)
775 {
776 u32 key;
777 struct device_node *np;
778
779 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
780 if (!np) {
781 pr_debug("No sysrq node found");
782 return;
783 }
784
785 /* Reset in case a __weak definition was present */
786 sysrq_reset_seq_len = 0;
787
788 of_property_for_each_u32(np, "keyset", key) {
789 if (key == KEY_RESERVED || key > KEY_MAX ||
790 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
791 break;
792
793 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
794 }
795
796 /* Get reset timeout if any. */
797 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
798
799 of_node_put(np);
800 }
801 #else
sysrq_of_get_keyreset_config(void)802 static void sysrq_of_get_keyreset_config(void)
803 {
804 }
805 #endif
806
sysrq_reinject_alt_sysrq(struct work_struct * work)807 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
808 {
809 struct sysrq_state *sysrq =
810 container_of(work, struct sysrq_state, reinject_work);
811 struct input_handle *handle = &sysrq->handle;
812 unsigned int alt_code = sysrq->alt_use;
813
814 if (sysrq->need_reinject) {
815 /* we do not want the assignment to be reordered */
816 sysrq->reinjecting = true;
817 mb();
818
819 /* Simulate press and release of Alt + SysRq */
820 input_inject_event(handle, EV_KEY, alt_code, 1);
821 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
822 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
823
824 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
825 input_inject_event(handle, EV_KEY, alt_code, 0);
826 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
827
828 mb();
829 sysrq->reinjecting = false;
830 }
831 }
832
sysrq_handle_keypress(struct sysrq_state * sysrq,unsigned int code,int value)833 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
834 unsigned int code, int value)
835 {
836 bool was_active = sysrq->active;
837 bool suppress;
838
839 switch (code) {
840
841 case KEY_LEFTALT:
842 case KEY_RIGHTALT:
843 if (!value) {
844 /* One of ALTs is being released */
845 if (sysrq->active && code == sysrq->alt_use)
846 sysrq->active = false;
847
848 sysrq->alt = KEY_RESERVED;
849
850 } else if (value != 2) {
851 sysrq->alt = code;
852 sysrq->need_reinject = false;
853 }
854 break;
855
856 case KEY_LEFTSHIFT:
857 case KEY_RIGHTSHIFT:
858 if (!value)
859 sysrq->shift = KEY_RESERVED;
860 else if (value != 2)
861 sysrq->shift = code;
862 if (sysrq->active)
863 sysrq->shift_use = sysrq->shift;
864 break;
865
866 case KEY_SYSRQ:
867 if (value == 1 && sysrq->alt != KEY_RESERVED) {
868 sysrq->active = true;
869 sysrq->alt_use = sysrq->alt;
870 /* either RESERVED (for released) or actual code */
871 sysrq->shift_use = sysrq->shift;
872 /*
873 * If nothing else will be pressed we'll need
874 * to re-inject Alt-SysRq keysroke.
875 */
876 sysrq->need_reinject = true;
877 }
878
879 /*
880 * Pretend that sysrq was never pressed at all. This
881 * is needed to properly handle KGDB which will try
882 * to release all keys after exiting debugger. If we
883 * do not clear key bit it KGDB will end up sending
884 * release events for Alt and SysRq, potentially
885 * triggering print screen function.
886 */
887 if (sysrq->active)
888 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
889
890 break;
891
892 default:
893 if (sysrq->active && value && value != 2) {
894 unsigned char c = sysrq_xlate[code];
895
896 sysrq->need_reinject = false;
897 if (sysrq->shift_use != KEY_RESERVED)
898 c = toupper(c);
899 __handle_sysrq(c, true);
900 }
901 break;
902 }
903
904 suppress = sysrq->active;
905
906 if (!sysrq->active) {
907
908 /*
909 * See if reset sequence has changed since the last time.
910 */
911 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
912 sysrq_parse_reset_sequence(sysrq);
913
914 /*
915 * If we are not suppressing key presses keep track of
916 * keyboard state so we can release keys that have been
917 * pressed before entering SysRq mode.
918 */
919 if (value)
920 set_bit(code, sysrq->key_down);
921 else
922 clear_bit(code, sysrq->key_down);
923
924 if (was_active)
925 schedule_work(&sysrq->reinject_work);
926
927 /* Check for reset sequence */
928 sysrq_detect_reset_sequence(sysrq, code, value);
929
930 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
931 /*
932 * Pass on release events for keys that was pressed before
933 * entering SysRq mode.
934 */
935 suppress = false;
936 }
937
938 return suppress;
939 }
940
sysrq_filter(struct input_handle * handle,unsigned int type,unsigned int code,int value)941 static bool sysrq_filter(struct input_handle *handle,
942 unsigned int type, unsigned int code, int value)
943 {
944 struct sysrq_state *sysrq = handle->private;
945 bool suppress;
946
947 /*
948 * Do not filter anything if we are in the process of re-injecting
949 * Alt+SysRq combination.
950 */
951 if (sysrq->reinjecting)
952 return false;
953
954 switch (type) {
955
956 case EV_SYN:
957 suppress = false;
958 break;
959
960 case EV_KEY:
961 suppress = sysrq_handle_keypress(sysrq, code, value);
962 break;
963
964 default:
965 suppress = sysrq->active;
966 break;
967 }
968
969 return suppress;
970 }
971
sysrq_connect(struct input_handler * handler,struct input_dev * dev,const struct input_device_id * id)972 static int sysrq_connect(struct input_handler *handler,
973 struct input_dev *dev,
974 const struct input_device_id *id)
975 {
976 struct sysrq_state *sysrq;
977 int error;
978
979 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
980 if (!sysrq)
981 return -ENOMEM;
982
983 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
984
985 sysrq->handle.dev = dev;
986 sysrq->handle.handler = handler;
987 sysrq->handle.name = "sysrq";
988 sysrq->handle.private = sysrq;
989 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
990
991 error = input_register_handle(&sysrq->handle);
992 if (error) {
993 pr_err("Failed to register input sysrq handler, error %d\n",
994 error);
995 goto err_free;
996 }
997
998 error = input_open_device(&sysrq->handle);
999 if (error) {
1000 pr_err("Failed to open input device, error %d\n", error);
1001 goto err_unregister;
1002 }
1003
1004 return 0;
1005
1006 err_unregister:
1007 input_unregister_handle(&sysrq->handle);
1008 err_free:
1009 kfree(sysrq);
1010 return error;
1011 }
1012
sysrq_disconnect(struct input_handle * handle)1013 static void sysrq_disconnect(struct input_handle *handle)
1014 {
1015 struct sysrq_state *sysrq = handle->private;
1016
1017 input_close_device(handle);
1018 cancel_work_sync(&sysrq->reinject_work);
1019 timer_shutdown_sync(&sysrq->keyreset_timer);
1020 input_unregister_handle(handle);
1021 kfree(sysrq);
1022 }
1023
1024 /*
1025 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1026 * keyboards have SysRq key predefined and so user may add it to keymap
1027 * later, but we expect all such keyboards to have left alt.
1028 */
1029 static const struct input_device_id sysrq_ids[] = {
1030 {
1031 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1032 INPUT_DEVICE_ID_MATCH_KEYBIT,
1033 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1034 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1035 },
1036 { },
1037 };
1038
1039 static struct input_handler sysrq_handler = {
1040 .filter = sysrq_filter,
1041 .connect = sysrq_connect,
1042 .disconnect = sysrq_disconnect,
1043 .name = "sysrq",
1044 .id_table = sysrq_ids,
1045 };
1046
sysrq_register_handler(void)1047 static inline void sysrq_register_handler(void)
1048 {
1049 int error;
1050
1051 sysrq_of_get_keyreset_config();
1052
1053 error = input_register_handler(&sysrq_handler);
1054 if (error)
1055 pr_err("Failed to register input handler, error %d", error);
1056 }
1057
sysrq_unregister_handler(void)1058 static inline void sysrq_unregister_handler(void)
1059 {
1060 input_unregister_handler(&sysrq_handler);
1061 }
1062
sysrq_reset_seq_param_set(const char * buffer,const struct kernel_param * kp)1063 static int sysrq_reset_seq_param_set(const char *buffer,
1064 const struct kernel_param *kp)
1065 {
1066 unsigned long val;
1067 int error;
1068
1069 error = kstrtoul(buffer, 0, &val);
1070 if (error < 0)
1071 return error;
1072
1073 if (val > KEY_MAX)
1074 return -EINVAL;
1075
1076 *((unsigned short *)kp->arg) = val;
1077 sysrq_reset_seq_version++;
1078
1079 return 0;
1080 }
1081
1082 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1083 .get = param_get_ushort,
1084 .set = sysrq_reset_seq_param_set,
1085 };
1086
1087 #define param_check_sysrq_reset_seq(name, p) \
1088 __param_check(name, p, unsigned short)
1089
1090 /*
1091 * not really modular, but the easiest way to keep compat with existing
1092 * bootargs behaviour is to continue using module_param here.
1093 */
1094 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1095 &sysrq_reset_seq_len, 0644);
1096
1097 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1098
1099 #else
1100
sysrq_register_handler(void)1101 static inline void sysrq_register_handler(void)
1102 {
1103 }
1104
sysrq_unregister_handler(void)1105 static inline void sysrq_unregister_handler(void)
1106 {
1107 }
1108
1109 #endif /* CONFIG_INPUT */
1110
sysrq_toggle_support(int enable_mask)1111 int sysrq_toggle_support(int enable_mask)
1112 {
1113 bool was_enabled = sysrq_on();
1114
1115 sysrq_enabled = enable_mask;
1116
1117 if (was_enabled != sysrq_on()) {
1118 if (sysrq_on())
1119 sysrq_register_handler();
1120 else
1121 sysrq_unregister_handler();
1122 }
1123
1124 return 0;
1125 }
1126 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1127
__sysrq_swap_key_ops(u8 key,const struct sysrq_key_op * insert_op_p,const struct sysrq_key_op * remove_op_p)1128 static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p,
1129 const struct sysrq_key_op *remove_op_p)
1130 {
1131 int retval;
1132
1133 spin_lock(&sysrq_key_table_lock);
1134 if (__sysrq_get_key_op(key) == remove_op_p) {
1135 __sysrq_put_key_op(key, insert_op_p);
1136 retval = 0;
1137 } else {
1138 retval = -1;
1139 }
1140 spin_unlock(&sysrq_key_table_lock);
1141
1142 /*
1143 * A concurrent __handle_sysrq either got the old op or the new op.
1144 * Wait for it to go away before returning, so the code for an old
1145 * op is not freed (eg. on module unload) while it is in use.
1146 */
1147 synchronize_rcu();
1148
1149 return retval;
1150 }
1151
register_sysrq_key(u8 key,const struct sysrq_key_op * op_p)1152 int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1153 {
1154 return __sysrq_swap_key_ops(key, op_p, NULL);
1155 }
1156 EXPORT_SYMBOL(register_sysrq_key);
1157
unregister_sysrq_key(u8 key,const struct sysrq_key_op * op_p)1158 int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1159 {
1160 return __sysrq_swap_key_ops(key, NULL, op_p);
1161 }
1162 EXPORT_SYMBOL(unregister_sysrq_key);
1163
1164 #ifdef CONFIG_PROC_FS
1165 /*
1166 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1167 * Normally, only the first character written is processed.
1168 * However, if the first character is an underscore,
1169 * all characters are processed.
1170 */
write_sysrq_trigger(struct file * file,const char __user * buf,size_t count,loff_t * ppos)1171 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1172 size_t count, loff_t *ppos)
1173 {
1174 bool bulk = false;
1175 size_t i;
1176
1177 for (i = 0; i < count; i++) {
1178 char c;
1179
1180 if (get_user(c, buf + i))
1181 return -EFAULT;
1182
1183 if (c == '_')
1184 bulk = true;
1185 else
1186 __handle_sysrq(c, false);
1187
1188 if (!bulk)
1189 break;
1190 }
1191
1192 return count;
1193 }
1194
1195 static const struct proc_ops sysrq_trigger_proc_ops = {
1196 .proc_write = write_sysrq_trigger,
1197 .proc_lseek = noop_llseek,
1198 };
1199
sysrq_init_procfs(void)1200 static void sysrq_init_procfs(void)
1201 {
1202 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1203 &sysrq_trigger_proc_ops))
1204 pr_err("Failed to register proc interface\n");
1205 }
1206
1207 #else
1208
sysrq_init_procfs(void)1209 static inline void sysrq_init_procfs(void)
1210 {
1211 }
1212
1213 #endif /* CONFIG_PROC_FS */
1214
sysrq_init(void)1215 static int __init sysrq_init(void)
1216 {
1217 sysrq_init_procfs();
1218
1219 if (sysrq_on())
1220 sysrq_register_handler();
1221
1222 return 0;
1223 }
1224 device_initcall(sysrq_init);
1225