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(u8 key)101 static void sysrq_handle_loglevel(u8 key)
102 {
103 u8 loglevel = key - '0';
104
105 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
106 pr_info("Loglevel set to %u\n", loglevel);
107 console_loglevel = loglevel;
108 }
109 static const struct sysrq_key_op sysrq_loglevel_op = {
110 .handler = sysrq_handle_loglevel,
111 .help_msg = "loglevel(0-9)",
112 .action_msg = "Changing Loglevel",
113 .enable_mask = SYSRQ_ENABLE_LOG,
114 };
115
116 #ifdef CONFIG_VT
sysrq_handle_SAK(u8 key)117 static void sysrq_handle_SAK(u8 key)
118 {
119 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
120
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(u8 key)134 static void sysrq_handle_unraw(u8 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(u8 key)149 static void sysrq_handle_crash(u8 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(u8 key)163 static void sysrq_handle_reboot(u8 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(u8 key)178 static void sysrq_handle_sync(u8 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(u8 key)189 static void sysrq_handle_show_timers(u8 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(u8 key)200 static void sysrq_handle_mountro(u8 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(u8 key)212 static void sysrq_handle_showlocks(u8 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(u8 key)252 static void sysrq_handle_showallcpus(u8 key)
253 {
254 /*
255 * Fall back to the workqueue based printing if the
256 * backtrace printing did not succeed or the
257 * architecture has no support for it:
258 */
259 if (!trigger_all_cpu_backtrace()) {
260 struct pt_regs *regs = NULL;
261
262 if (in_hardirq())
263 regs = get_irq_regs();
264
265 pr_info("CPU%d:\n", get_cpu());
266 if (regs)
267 show_regs(regs);
268 else
269 show_stack(NULL, NULL, KERN_INFO);
270
271 schedule_work(&sysrq_showallcpus);
272 put_cpu();
273 }
274 }
275
276 static const struct sysrq_key_op sysrq_showallcpus_op = {
277 .handler = sysrq_handle_showallcpus,
278 .help_msg = "show-backtrace-all-active-cpus(l)",
279 .action_msg = "Show backtrace of all active CPUs",
280 .enable_mask = SYSRQ_ENABLE_DUMP,
281 };
282 #else
283 #define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL)
284 #endif
285
sysrq_handle_showregs(u8 key)286 static void sysrq_handle_showregs(u8 key)
287 {
288 struct pt_regs *regs = NULL;
289
290 if (in_hardirq())
291 regs = get_irq_regs();
292 if (regs)
293 show_regs(regs);
294 perf_event_print_debug();
295 }
296 static const struct sysrq_key_op sysrq_showregs_op = {
297 .handler = sysrq_handle_showregs,
298 .help_msg = "show-registers(p)",
299 .action_msg = "Show Regs",
300 .enable_mask = SYSRQ_ENABLE_DUMP,
301 };
302
sysrq_handle_showstate(u8 key)303 static void sysrq_handle_showstate(u8 key)
304 {
305 show_state();
306 show_all_workqueues();
307 }
308 static const struct sysrq_key_op sysrq_showstate_op = {
309 .handler = sysrq_handle_showstate,
310 .help_msg = "show-task-states(t)",
311 .action_msg = "Show State",
312 .enable_mask = SYSRQ_ENABLE_DUMP,
313 };
314
sysrq_handle_showstate_blocked(u8 key)315 static void sysrq_handle_showstate_blocked(u8 key)
316 {
317 show_state_filter(TASK_UNINTERRUPTIBLE);
318 }
319 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
320 .handler = sysrq_handle_showstate_blocked,
321 .help_msg = "show-blocked-tasks(w)",
322 .action_msg = "Show Blocked State",
323 .enable_mask = SYSRQ_ENABLE_DUMP,
324 };
325
326 #ifdef CONFIG_TRACING
327 #include <linux/ftrace.h>
328
sysrq_ftrace_dump(u8 key)329 static void sysrq_ftrace_dump(u8 key)
330 {
331 ftrace_dump(DUMP_ALL);
332 }
333 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
334 .handler = sysrq_ftrace_dump,
335 .help_msg = "dump-ftrace-buffer(z)",
336 .action_msg = "Dump ftrace buffer",
337 .enable_mask = SYSRQ_ENABLE_DUMP,
338 };
339 #else
340 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
341 #endif
342
sysrq_handle_showmem(u8 key)343 static void sysrq_handle_showmem(u8 key)
344 {
345 show_mem();
346 }
347 static const struct sysrq_key_op sysrq_showmem_op = {
348 .handler = sysrq_handle_showmem,
349 .help_msg = "show-memory-usage(m)",
350 .action_msg = "Show Memory",
351 .enable_mask = SYSRQ_ENABLE_DUMP,
352 };
353
354 /*
355 * Signal sysrq helper function. Sends a signal to all user processes.
356 */
send_sig_all(int sig)357 static void send_sig_all(int sig)
358 {
359 struct task_struct *p;
360
361 read_lock(&tasklist_lock);
362 for_each_process(p) {
363 if (p->flags & PF_KTHREAD)
364 continue;
365 if (is_global_init(p))
366 continue;
367
368 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
369 }
370 read_unlock(&tasklist_lock);
371 }
372
sysrq_handle_term(u8 key)373 static void sysrq_handle_term(u8 key)
374 {
375 send_sig_all(SIGTERM);
376 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
377 }
378 static const struct sysrq_key_op sysrq_term_op = {
379 .handler = sysrq_handle_term,
380 .help_msg = "terminate-all-tasks(e)",
381 .action_msg = "Terminate All Tasks",
382 .enable_mask = SYSRQ_ENABLE_SIGNAL,
383 };
384
moom_callback(struct work_struct * ignored)385 static void moom_callback(struct work_struct *ignored)
386 {
387 const gfp_t gfp_mask = GFP_KERNEL;
388 struct oom_control oc = {
389 .zonelist = node_zonelist(first_memory_node, gfp_mask),
390 .nodemask = NULL,
391 .memcg = NULL,
392 .gfp_mask = gfp_mask,
393 .order = -1,
394 };
395
396 mutex_lock(&oom_lock);
397 if (!out_of_memory(&oc))
398 pr_info("OOM request ignored. No task eligible\n");
399 mutex_unlock(&oom_lock);
400 }
401
402 static DECLARE_WORK(moom_work, moom_callback);
403
sysrq_handle_moom(u8 key)404 static void sysrq_handle_moom(u8 key)
405 {
406 schedule_work(&moom_work);
407 }
408 static const struct sysrq_key_op sysrq_moom_op = {
409 .handler = sysrq_handle_moom,
410 .help_msg = "memory-full-oom-kill(f)",
411 .action_msg = "Manual OOM execution",
412 .enable_mask = SYSRQ_ENABLE_SIGNAL,
413 };
414
415 #ifdef CONFIG_BLOCK
sysrq_handle_thaw(u8 key)416 static void sysrq_handle_thaw(u8 key)
417 {
418 emergency_thaw_all();
419 }
420 static const struct sysrq_key_op sysrq_thaw_op = {
421 .handler = sysrq_handle_thaw,
422 .help_msg = "thaw-filesystems(j)",
423 .action_msg = "Emergency Thaw of all frozen filesystems",
424 .enable_mask = SYSRQ_ENABLE_SIGNAL,
425 };
426 #else
427 #define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL)
428 #endif
429
sysrq_handle_kill(u8 key)430 static void sysrq_handle_kill(u8 key)
431 {
432 send_sig_all(SIGKILL);
433 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
434 }
435 static const struct sysrq_key_op sysrq_kill_op = {
436 .handler = sysrq_handle_kill,
437 .help_msg = "kill-all-tasks(i)",
438 .action_msg = "Kill All Tasks",
439 .enable_mask = SYSRQ_ENABLE_SIGNAL,
440 };
441
sysrq_handle_unrt(u8 key)442 static void sysrq_handle_unrt(u8 key)
443 {
444 normalize_rt_tasks();
445 }
446 static const struct sysrq_key_op sysrq_unrt_op = {
447 .handler = sysrq_handle_unrt,
448 .help_msg = "nice-all-RT-tasks(n)",
449 .action_msg = "Nice All RT Tasks",
450 .enable_mask = SYSRQ_ENABLE_RTNICE,
451 };
452
sysrq_handle_replay_logs(u8 key)453 static void sysrq_handle_replay_logs(u8 key)
454 {
455 console_try_replay_all();
456 }
457 static struct sysrq_key_op sysrq_replay_logs_op = {
458 .handler = sysrq_handle_replay_logs,
459 .help_msg = "replay-kernel-logs(R)",
460 .action_msg = "Replay kernel logs on consoles",
461 .enable_mask = SYSRQ_ENABLE_DUMP,
462 };
463
464 /* Key Operations table and lock */
465 static DEFINE_SPINLOCK(sysrq_key_table_lock);
466
467 static const struct sysrq_key_op *sysrq_key_table[62] = {
468 &sysrq_loglevel_op, /* 0 */
469 &sysrq_loglevel_op, /* 1 */
470 &sysrq_loglevel_op, /* 2 */
471 &sysrq_loglevel_op, /* 3 */
472 &sysrq_loglevel_op, /* 4 */
473 &sysrq_loglevel_op, /* 5 */
474 &sysrq_loglevel_op, /* 6 */
475 &sysrq_loglevel_op, /* 7 */
476 &sysrq_loglevel_op, /* 8 */
477 &sysrq_loglevel_op, /* 9 */
478
479 /*
480 * a: Don't use for system provided sysrqs, it is handled specially on
481 * sparc and will never arrive.
482 */
483 NULL, /* a */
484 &sysrq_reboot_op, /* b */
485 &sysrq_crash_op, /* c */
486 &sysrq_showlocks_op, /* d */
487 &sysrq_term_op, /* e */
488 &sysrq_moom_op, /* f */
489 /* g: May be registered for the kernel debugger */
490 NULL, /* g */
491 NULL, /* h - reserved for help */
492 &sysrq_kill_op, /* i */
493 &sysrq_thaw_op, /* j */
494 &sysrq_SAK_op, /* k */
495 &sysrq_showallcpus_op, /* l */
496 &sysrq_showmem_op, /* m */
497 &sysrq_unrt_op, /* n */
498 /* o: This will often be registered as 'Off' at init time */
499 NULL, /* o */
500 &sysrq_showregs_op, /* p */
501 &sysrq_show_timers_op, /* q */
502 &sysrq_unraw_op, /* r */
503 &sysrq_sync_op, /* s */
504 &sysrq_showstate_op, /* t */
505 &sysrq_mountro_op, /* u */
506 /* v: May be registered for frame buffer console restore */
507 NULL, /* v */
508 &sysrq_showstate_blocked_op, /* w */
509 /* x: May be registered on mips for TLB dump */
510 /* x: May be registered on ppc/powerpc for xmon */
511 /* x: May be registered on sparc64 for global PMU dump */
512 NULL, /* x */
513 /* y: May be registered on sparc64 for global register dump */
514 NULL, /* y */
515 &sysrq_ftrace_dump_op, /* z */
516 NULL, /* A */
517 NULL, /* B */
518 NULL, /* C */
519 NULL, /* D */
520 NULL, /* E */
521 NULL, /* F */
522 NULL, /* G */
523 NULL, /* H */
524 NULL, /* I */
525 NULL, /* J */
526 NULL, /* K */
527 NULL, /* L */
528 NULL, /* M */
529 NULL, /* N */
530 NULL, /* O */
531 NULL, /* P */
532 NULL, /* Q */
533 &sysrq_replay_logs_op, /* R */
534 /* S: May be registered by sched_ext for resetting */
535 NULL, /* S */
536 NULL, /* T */
537 NULL, /* U */
538 NULL, /* V */
539 NULL, /* W */
540 NULL, /* X */
541 NULL, /* Y */
542 NULL, /* Z */
543 };
544
545 /* key2index calculation, -1 on invalid index */
sysrq_key_table_key2index(u8 key)546 static int sysrq_key_table_key2index(u8 key)
547 {
548 switch (key) {
549 case '0' ... '9':
550 return key - '0';
551 case 'a' ... 'z':
552 return key - 'a' + 10;
553 case 'A' ... 'Z':
554 return key - 'A' + 10 + 26;
555 default:
556 return -1;
557 }
558 }
559
560 /*
561 * get and put functions for the table, exposed to modules.
562 */
__sysrq_get_key_op(u8 key)563 static const struct sysrq_key_op *__sysrq_get_key_op(u8 key)
564 {
565 const struct sysrq_key_op *op_p = NULL;
566 int i;
567
568 i = sysrq_key_table_key2index(key);
569 if (i != -1)
570 op_p = sysrq_key_table[i];
571
572 return op_p;
573 }
574
__sysrq_put_key_op(u8 key,const struct sysrq_key_op * op_p)575 static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p)
576 {
577 int i = sysrq_key_table_key2index(key);
578
579 if (i != -1)
580 sysrq_key_table[i] = op_p;
581 }
582
__handle_sysrq(u8 key,bool check_mask)583 void __handle_sysrq(u8 key, bool check_mask)
584 {
585 const struct sysrq_key_op *op_p;
586 int orig_log_level;
587 int orig_suppress_printk;
588 int i;
589
590 orig_suppress_printk = suppress_printk;
591 suppress_printk = 0;
592
593 rcu_sysrq_start();
594 rcu_read_lock();
595 /*
596 * Raise the apparent loglevel to maximum so that the sysrq header
597 * is shown to provide the user with positive feedback. We do not
598 * simply emit this at KERN_EMERG as that would change message
599 * routing in the consumers of /proc/kmsg.
600 */
601 orig_log_level = console_loglevel;
602 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
603
604 op_p = __sysrq_get_key_op(key);
605 if (op_p) {
606 /*
607 * Should we check for enabled operations (/proc/sysrq-trigger
608 * should not) and is the invoked operation enabled?
609 */
610 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
611 pr_info("%s\n", op_p->action_msg);
612 console_loglevel = orig_log_level;
613 op_p->handler(key);
614 } else {
615 pr_info("This sysrq operation is disabled.\n");
616 console_loglevel = orig_log_level;
617 }
618 } else {
619 pr_info("HELP : ");
620 /* Only print the help msg once per handler */
621 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
622 if (sysrq_key_table[i]) {
623 int j;
624
625 for (j = 0; sysrq_key_table[i] !=
626 sysrq_key_table[j]; j++)
627 ;
628 if (j != i)
629 continue;
630 pr_cont("%s ", sysrq_key_table[i]->help_msg);
631 }
632 }
633 pr_cont("\n");
634 console_loglevel = orig_log_level;
635 }
636 rcu_read_unlock();
637 rcu_sysrq_end();
638
639 suppress_printk = orig_suppress_printk;
640 }
641
handle_sysrq(u8 key)642 void handle_sysrq(u8 key)
643 {
644 if (sysrq_on())
645 __handle_sysrq(key, true);
646 }
647 EXPORT_SYMBOL(handle_sysrq);
648
649 #ifdef CONFIG_INPUT
650 static int sysrq_reset_downtime_ms;
651
652 /* Simple translation table for the SysRq keys */
653 static const unsigned char sysrq_xlate[KEY_CNT] =
654 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
655 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
656 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
657 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
658 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
659 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
660 "\r\000/"; /* 0x60 - 0x6f */
661
662 struct sysrq_state {
663 struct input_handle handle;
664 struct work_struct reinject_work;
665 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
666 unsigned int alt;
667 unsigned int alt_use;
668 unsigned int shift;
669 unsigned int shift_use;
670 bool active;
671 bool need_reinject;
672 bool reinjecting;
673
674 /* reset sequence handling */
675 bool reset_canceled;
676 bool reset_requested;
677 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
678 int reset_seq_len;
679 int reset_seq_cnt;
680 int reset_seq_version;
681 struct timer_list keyreset_timer;
682 };
683
684 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
685 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
686 static unsigned int sysrq_reset_seq_len;
687 static unsigned int sysrq_reset_seq_version = 1;
688
sysrq_parse_reset_sequence(struct sysrq_state * state)689 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
690 {
691 int i;
692 unsigned short key;
693
694 state->reset_seq_cnt = 0;
695
696 for (i = 0; i < sysrq_reset_seq_len; i++) {
697 key = sysrq_reset_seq[i];
698
699 if (key == KEY_RESERVED || key > KEY_MAX)
700 break;
701
702 __set_bit(key, state->reset_keybit);
703 state->reset_seq_len++;
704
705 if (test_bit(key, state->key_down))
706 state->reset_seq_cnt++;
707 }
708
709 /* Disable reset until old keys are not released */
710 state->reset_canceled = state->reset_seq_cnt != 0;
711
712 state->reset_seq_version = sysrq_reset_seq_version;
713 }
714
sysrq_do_reset(struct timer_list * t)715 static void sysrq_do_reset(struct timer_list *t)
716 {
717 struct sysrq_state *state = from_timer(state, t, keyreset_timer);
718
719 state->reset_requested = true;
720
721 orderly_reboot();
722 }
723
sysrq_handle_reset_request(struct sysrq_state * state)724 static void sysrq_handle_reset_request(struct sysrq_state *state)
725 {
726 if (state->reset_requested)
727 __handle_sysrq(sysrq_xlate[KEY_B], false);
728
729 if (sysrq_reset_downtime_ms)
730 mod_timer(&state->keyreset_timer,
731 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
732 else
733 sysrq_do_reset(&state->keyreset_timer);
734 }
735
sysrq_detect_reset_sequence(struct sysrq_state * state,unsigned int code,int value)736 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
737 unsigned int code, int value)
738 {
739 if (!test_bit(code, state->reset_keybit)) {
740 /*
741 * Pressing any key _not_ in reset sequence cancels
742 * the reset sequence. Also cancelling the timer in
743 * case additional keys were pressed after a reset
744 * has been requested.
745 */
746 if (value && state->reset_seq_cnt) {
747 state->reset_canceled = true;
748 del_timer(&state->keyreset_timer);
749 }
750 } else if (value == 0) {
751 /*
752 * Key release - all keys in the reset sequence need
753 * to be pressed and held for the reset timeout
754 * to hold.
755 */
756 del_timer(&state->keyreset_timer);
757
758 if (--state->reset_seq_cnt == 0)
759 state->reset_canceled = false;
760 } else if (value == 1) {
761 /* key press, not autorepeat */
762 if (++state->reset_seq_cnt == state->reset_seq_len &&
763 !state->reset_canceled) {
764 sysrq_handle_reset_request(state);
765 }
766 }
767 }
768
769 #ifdef CONFIG_OF
sysrq_of_get_keyreset_config(void)770 static void sysrq_of_get_keyreset_config(void)
771 {
772 u32 key;
773 struct device_node *np;
774
775 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
776 if (!np) {
777 pr_debug("No sysrq node found");
778 return;
779 }
780
781 /* Reset in case a __weak definition was present */
782 sysrq_reset_seq_len = 0;
783
784 of_property_for_each_u32(np, "keyset", key) {
785 if (key == KEY_RESERVED || key > KEY_MAX ||
786 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
787 break;
788
789 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
790 }
791
792 /* Get reset timeout if any. */
793 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
794
795 of_node_put(np);
796 }
797 #else
sysrq_of_get_keyreset_config(void)798 static void sysrq_of_get_keyreset_config(void)
799 {
800 }
801 #endif
802
sysrq_reinject_alt_sysrq(struct work_struct * work)803 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
804 {
805 struct sysrq_state *sysrq =
806 container_of(work, struct sysrq_state, reinject_work);
807 struct input_handle *handle = &sysrq->handle;
808 unsigned int alt_code = sysrq->alt_use;
809
810 if (sysrq->need_reinject) {
811 /* we do not want the assignment to be reordered */
812 sysrq->reinjecting = true;
813 mb();
814
815 /* Simulate press and release of Alt + SysRq */
816 input_inject_event(handle, EV_KEY, alt_code, 1);
817 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
818 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
819
820 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
821 input_inject_event(handle, EV_KEY, alt_code, 0);
822 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
823
824 mb();
825 sysrq->reinjecting = false;
826 }
827 }
828
sysrq_handle_keypress(struct sysrq_state * sysrq,unsigned int code,int value)829 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
830 unsigned int code, int value)
831 {
832 bool was_active = sysrq->active;
833 bool suppress;
834
835 switch (code) {
836
837 case KEY_LEFTALT:
838 case KEY_RIGHTALT:
839 if (!value) {
840 /* One of ALTs is being released */
841 if (sysrq->active && code == sysrq->alt_use)
842 sysrq->active = false;
843
844 sysrq->alt = KEY_RESERVED;
845
846 } else if (value != 2) {
847 sysrq->alt = code;
848 sysrq->need_reinject = false;
849 }
850 break;
851
852 case KEY_LEFTSHIFT:
853 case KEY_RIGHTSHIFT:
854 if (!value)
855 sysrq->shift = KEY_RESERVED;
856 else if (value != 2)
857 sysrq->shift = code;
858 if (sysrq->active)
859 sysrq->shift_use = sysrq->shift;
860 break;
861
862 case KEY_SYSRQ:
863 if (value == 1 && sysrq->alt != KEY_RESERVED) {
864 sysrq->active = true;
865 sysrq->alt_use = sysrq->alt;
866 /* either RESERVED (for released) or actual code */
867 sysrq->shift_use = sysrq->shift;
868 /*
869 * If nothing else will be pressed we'll need
870 * to re-inject Alt-SysRq keysroke.
871 */
872 sysrq->need_reinject = true;
873 }
874
875 /*
876 * Pretend that sysrq was never pressed at all. This
877 * is needed to properly handle KGDB which will try
878 * to release all keys after exiting debugger. If we
879 * do not clear key bit it KGDB will end up sending
880 * release events for Alt and SysRq, potentially
881 * triggering print screen function.
882 */
883 if (sysrq->active)
884 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
885
886 break;
887
888 default:
889 if (sysrq->active && value && value != 2) {
890 unsigned char c = sysrq_xlate[code];
891
892 sysrq->need_reinject = false;
893 if (sysrq->shift_use != KEY_RESERVED)
894 c = toupper(c);
895 __handle_sysrq(c, true);
896 }
897 break;
898 }
899
900 suppress = sysrq->active;
901
902 if (!sysrq->active) {
903
904 /*
905 * See if reset sequence has changed since the last time.
906 */
907 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
908 sysrq_parse_reset_sequence(sysrq);
909
910 /*
911 * If we are not suppressing key presses keep track of
912 * keyboard state so we can release keys that have been
913 * pressed before entering SysRq mode.
914 */
915 if (value)
916 set_bit(code, sysrq->key_down);
917 else
918 clear_bit(code, sysrq->key_down);
919
920 if (was_active)
921 schedule_work(&sysrq->reinject_work);
922
923 /* Check for reset sequence */
924 sysrq_detect_reset_sequence(sysrq, code, value);
925
926 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
927 /*
928 * Pass on release events for keys that was pressed before
929 * entering SysRq mode.
930 */
931 suppress = false;
932 }
933
934 return suppress;
935 }
936
sysrq_filter(struct input_handle * handle,unsigned int type,unsigned int code,int value)937 static bool sysrq_filter(struct input_handle *handle,
938 unsigned int type, unsigned int code, int value)
939 {
940 struct sysrq_state *sysrq = handle->private;
941 bool suppress;
942
943 /*
944 * Do not filter anything if we are in the process of re-injecting
945 * Alt+SysRq combination.
946 */
947 if (sysrq->reinjecting)
948 return false;
949
950 switch (type) {
951
952 case EV_SYN:
953 suppress = false;
954 break;
955
956 case EV_KEY:
957 suppress = sysrq_handle_keypress(sysrq, code, value);
958 break;
959
960 default:
961 suppress = sysrq->active;
962 break;
963 }
964
965 return suppress;
966 }
967
sysrq_connect(struct input_handler * handler,struct input_dev * dev,const struct input_device_id * id)968 static int sysrq_connect(struct input_handler *handler,
969 struct input_dev *dev,
970 const struct input_device_id *id)
971 {
972 struct sysrq_state *sysrq;
973 int error;
974
975 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
976 if (!sysrq)
977 return -ENOMEM;
978
979 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
980
981 sysrq->handle.dev = dev;
982 sysrq->handle.handler = handler;
983 sysrq->handle.name = "sysrq";
984 sysrq->handle.private = sysrq;
985 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
986
987 error = input_register_handle(&sysrq->handle);
988 if (error) {
989 pr_err("Failed to register input sysrq handler, error %d\n",
990 error);
991 goto err_free;
992 }
993
994 error = input_open_device(&sysrq->handle);
995 if (error) {
996 pr_err("Failed to open input device, error %d\n", error);
997 goto err_unregister;
998 }
999
1000 return 0;
1001
1002 err_unregister:
1003 input_unregister_handle(&sysrq->handle);
1004 err_free:
1005 kfree(sysrq);
1006 return error;
1007 }
1008
sysrq_disconnect(struct input_handle * handle)1009 static void sysrq_disconnect(struct input_handle *handle)
1010 {
1011 struct sysrq_state *sysrq = handle->private;
1012
1013 input_close_device(handle);
1014 cancel_work_sync(&sysrq->reinject_work);
1015 timer_shutdown_sync(&sysrq->keyreset_timer);
1016 input_unregister_handle(handle);
1017 kfree(sysrq);
1018 }
1019
1020 /*
1021 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1022 * keyboards have SysRq key predefined and so user may add it to keymap
1023 * later, but we expect all such keyboards to have left alt.
1024 */
1025 static const struct input_device_id sysrq_ids[] = {
1026 {
1027 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1028 INPUT_DEVICE_ID_MATCH_KEYBIT,
1029 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1030 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1031 },
1032 { },
1033 };
1034
1035 static struct input_handler sysrq_handler = {
1036 .filter = sysrq_filter,
1037 .connect = sysrq_connect,
1038 .disconnect = sysrq_disconnect,
1039 .name = "sysrq",
1040 .id_table = sysrq_ids,
1041 };
1042
sysrq_register_handler(void)1043 static inline void sysrq_register_handler(void)
1044 {
1045 int error;
1046
1047 sysrq_of_get_keyreset_config();
1048
1049 error = input_register_handler(&sysrq_handler);
1050 if (error)
1051 pr_err("Failed to register input handler, error %d", error);
1052 }
1053
sysrq_unregister_handler(void)1054 static inline void sysrq_unregister_handler(void)
1055 {
1056 input_unregister_handler(&sysrq_handler);
1057 }
1058
sysrq_reset_seq_param_set(const char * buffer,const struct kernel_param * kp)1059 static int sysrq_reset_seq_param_set(const char *buffer,
1060 const struct kernel_param *kp)
1061 {
1062 unsigned long val;
1063 int error;
1064
1065 error = kstrtoul(buffer, 0, &val);
1066 if (error < 0)
1067 return error;
1068
1069 if (val > KEY_MAX)
1070 return -EINVAL;
1071
1072 *((unsigned short *)kp->arg) = val;
1073 sysrq_reset_seq_version++;
1074
1075 return 0;
1076 }
1077
1078 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1079 .get = param_get_ushort,
1080 .set = sysrq_reset_seq_param_set,
1081 };
1082
1083 #define param_check_sysrq_reset_seq(name, p) \
1084 __param_check(name, p, unsigned short)
1085
1086 /*
1087 * not really modular, but the easiest way to keep compat with existing
1088 * bootargs behaviour is to continue using module_param here.
1089 */
1090 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1091 &sysrq_reset_seq_len, 0644);
1092
1093 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1094
1095 #else
1096
sysrq_register_handler(void)1097 static inline void sysrq_register_handler(void)
1098 {
1099 }
1100
sysrq_unregister_handler(void)1101 static inline void sysrq_unregister_handler(void)
1102 {
1103 }
1104
1105 #endif /* CONFIG_INPUT */
1106
sysrq_toggle_support(int enable_mask)1107 int sysrq_toggle_support(int enable_mask)
1108 {
1109 bool was_enabled = sysrq_on();
1110
1111 sysrq_enabled = enable_mask;
1112
1113 if (was_enabled != sysrq_on()) {
1114 if (sysrq_on())
1115 sysrq_register_handler();
1116 else
1117 sysrq_unregister_handler();
1118 }
1119
1120 return 0;
1121 }
1122 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1123
__sysrq_swap_key_ops(u8 key,const struct sysrq_key_op * insert_op_p,const struct sysrq_key_op * remove_op_p)1124 static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p,
1125 const struct sysrq_key_op *remove_op_p)
1126 {
1127 int retval;
1128
1129 spin_lock(&sysrq_key_table_lock);
1130 if (__sysrq_get_key_op(key) == remove_op_p) {
1131 __sysrq_put_key_op(key, insert_op_p);
1132 retval = 0;
1133 } else {
1134 retval = -1;
1135 }
1136 spin_unlock(&sysrq_key_table_lock);
1137
1138 /*
1139 * A concurrent __handle_sysrq either got the old op or the new op.
1140 * Wait for it to go away before returning, so the code for an old
1141 * op is not freed (eg. on module unload) while it is in use.
1142 */
1143 synchronize_rcu();
1144
1145 return retval;
1146 }
1147
register_sysrq_key(u8 key,const struct sysrq_key_op * op_p)1148 int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1149 {
1150 return __sysrq_swap_key_ops(key, op_p, NULL);
1151 }
1152 EXPORT_SYMBOL(register_sysrq_key);
1153
unregister_sysrq_key(u8 key,const struct sysrq_key_op * op_p)1154 int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1155 {
1156 return __sysrq_swap_key_ops(key, NULL, op_p);
1157 }
1158 EXPORT_SYMBOL(unregister_sysrq_key);
1159
1160 #ifdef CONFIG_PROC_FS
1161 /*
1162 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1163 * Normally, only the first character written is processed.
1164 * However, if the first character is an underscore,
1165 * all characters are processed.
1166 */
write_sysrq_trigger(struct file * file,const char __user * buf,size_t count,loff_t * ppos)1167 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1168 size_t count, loff_t *ppos)
1169 {
1170 bool bulk = false;
1171 size_t i;
1172
1173 for (i = 0; i < count; i++) {
1174 char c;
1175
1176 if (get_user(c, buf + i))
1177 return -EFAULT;
1178
1179 if (c == '_')
1180 bulk = true;
1181 else
1182 __handle_sysrq(c, false);
1183
1184 if (!bulk)
1185 break;
1186 }
1187
1188 return count;
1189 }
1190
1191 static const struct proc_ops sysrq_trigger_proc_ops = {
1192 .proc_write = write_sysrq_trigger,
1193 .proc_lseek = noop_llseek,
1194 };
1195
sysrq_init_procfs(void)1196 static void sysrq_init_procfs(void)
1197 {
1198 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1199 &sysrq_trigger_proc_ops))
1200 pr_err("Failed to register proc interface\n");
1201 }
1202
1203 #else
1204
sysrq_init_procfs(void)1205 static inline void sysrq_init_procfs(void)
1206 {
1207 }
1208
1209 #endif /* CONFIG_PROC_FS */
1210
sysrq_init(void)1211 static int __init sysrq_init(void)
1212 {
1213 sysrq_init_procfs();
1214
1215 if (sysrq_on())
1216 sysrq_register_handler();
1217
1218 return 0;
1219 }
1220 device_initcall(sysrq_init);
1221