1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Linux Magic System Request Key Hacks
4 *
5 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
6 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
7 *
8 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
9 * overhauled to use key registration
10 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies
11 *
12 * Copyright (c) 2010 Dmitry Torokhov
13 * Input handler conversion
14 */
15
16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17
18 #include <linux/sched/signal.h>
19 #include <linux/sched/rt.h>
20 #include <linux/sched/debug.h>
21 #include <linux/sched/task.h>
22 #include <linux/ctype.h>
23 #include <linux/interrupt.h>
24 #include <linux/mm.h>
25 #include <linux/fs.h>
26 #include <linux/mount.h>
27 #include <linux/kdev_t.h>
28 #include <linux/major.h>
29 #include <linux/reboot.h>
30 #include <linux/sysrq.h>
31 #include <linux/kbd_kern.h>
32 #include <linux/proc_fs.h>
33 #include <linux/nmi.h>
34 #include <linux/quotaops.h>
35 #include <linux/perf_event.h>
36 #include <linux/kernel.h>
37 #include <linux/module.h>
38 #include <linux/suspend.h>
39 #include <linux/writeback.h>
40 #include <linux/swap.h>
41 #include <linux/spinlock.h>
42 #include <linux/vt_kern.h>
43 #include <linux/workqueue.h>
44 #include <linux/hrtimer.h>
45 #include <linux/oom.h>
46 #include <linux/slab.h>
47 #include <linux/input.h>
48 #include <linux/uaccess.h>
49 #include <linux/moduleparam.h>
50 #include <linux/jiffies.h>
51 #include <linux/syscalls.h>
52 #include <linux/of.h>
53 #include <linux/rcupdate.h>
54
55 #include <asm/ptrace.h>
56 #include <asm/irq_regs.h>
57
58 /* Whether we react on sysrq keys or just ignore them */
59 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
60 static bool __read_mostly sysrq_always_enabled;
61
sysrq_on(void)62 static bool sysrq_on(void)
63 {
64 return sysrq_enabled || sysrq_always_enabled;
65 }
66
67 /**
68 * sysrq_mask - Getter for sysrq_enabled mask.
69 *
70 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
71 */
sysrq_mask(void)72 int sysrq_mask(void)
73 {
74 if (sysrq_always_enabled)
75 return 1;
76 return sysrq_enabled;
77 }
78 EXPORT_SYMBOL_GPL(sysrq_mask);
79
80 /*
81 * A value of 1 means 'all', other nonzero values are an op mask:
82 */
sysrq_on_mask(int mask)83 static bool sysrq_on_mask(int mask)
84 {
85 return sysrq_always_enabled ||
86 sysrq_enabled == 1 ||
87 (sysrq_enabled & mask);
88 }
89
sysrq_always_enabled_setup(char * str)90 static int __init sysrq_always_enabled_setup(char *str)
91 {
92 sysrq_always_enabled = true;
93 pr_info("sysrq always enabled.\n");
94
95 return 1;
96 }
97
98 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
99
100
sysrq_handle_loglevel(int key)101 static void sysrq_handle_loglevel(int key)
102 {
103 int i;
104
105 i = key - '0';
106 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
107 pr_info("Loglevel set to %d\n", i);
108 console_loglevel = i;
109 }
110 static const struct sysrq_key_op sysrq_loglevel_op = {
111 .handler = sysrq_handle_loglevel,
112 .help_msg = "loglevel(0-9)",
113 .action_msg = "Changing Loglevel",
114 .enable_mask = SYSRQ_ENABLE_LOG,
115 };
116
117 #ifdef CONFIG_VT
sysrq_handle_SAK(int key)118 static void sysrq_handle_SAK(int key)
119 {
120 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
121
122 schedule_work(SAK_work);
123 }
124 static const struct sysrq_key_op sysrq_SAK_op = {
125 .handler = sysrq_handle_SAK,
126 .help_msg = "sak(k)",
127 .action_msg = "SAK",
128 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
129 };
130 #else
131 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
132 #endif
133
134 #ifdef CONFIG_VT
sysrq_handle_unraw(int key)135 static void sysrq_handle_unraw(int key)
136 {
137 vt_reset_unicode(fg_console);
138 }
139
140 static const struct sysrq_key_op sysrq_unraw_op = {
141 .handler = sysrq_handle_unraw,
142 .help_msg = "unraw(r)",
143 .action_msg = "Keyboard mode set to system default",
144 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
145 };
146 #else
147 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
148 #endif /* CONFIG_VT */
149
sysrq_handle_crash(int key)150 static void sysrq_handle_crash(int key)
151 {
152 /* release the RCU read lock before crashing */
153 rcu_read_unlock();
154
155 panic("sysrq triggered crash\n");
156 }
157 static const struct sysrq_key_op sysrq_crash_op = {
158 .handler = sysrq_handle_crash,
159 .help_msg = "crash(c)",
160 .action_msg = "Trigger a crash",
161 .enable_mask = SYSRQ_ENABLE_DUMP,
162 };
163
sysrq_handle_reboot(int key)164 static void sysrq_handle_reboot(int key)
165 {
166 lockdep_off();
167 local_irq_enable();
168 emergency_restart();
169 }
170 static const struct sysrq_key_op sysrq_reboot_op = {
171 .handler = sysrq_handle_reboot,
172 .help_msg = "reboot(b)",
173 .action_msg = "Resetting",
174 .enable_mask = SYSRQ_ENABLE_BOOT,
175 };
176
177 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
178
sysrq_handle_sync(int key)179 static void sysrq_handle_sync(int key)
180 {
181 emergency_sync();
182 }
183 static const struct sysrq_key_op sysrq_sync_op = {
184 .handler = sysrq_handle_sync,
185 .help_msg = "sync(s)",
186 .action_msg = "Emergency Sync",
187 .enable_mask = SYSRQ_ENABLE_SYNC,
188 };
189
sysrq_handle_show_timers(int key)190 static void sysrq_handle_show_timers(int key)
191 {
192 sysrq_timer_list_show();
193 }
194
195 static const struct sysrq_key_op sysrq_show_timers_op = {
196 .handler = sysrq_handle_show_timers,
197 .help_msg = "show-all-timers(q)",
198 .action_msg = "Show clockevent devices & pending hrtimers (no others)",
199 };
200
sysrq_handle_mountro(int key)201 static void sysrq_handle_mountro(int key)
202 {
203 emergency_remount();
204 }
205 static const struct sysrq_key_op sysrq_mountro_op = {
206 .handler = sysrq_handle_mountro,
207 .help_msg = "unmount(u)",
208 .action_msg = "Emergency Remount R/O",
209 .enable_mask = SYSRQ_ENABLE_REMOUNT,
210 };
211
212 #ifdef CONFIG_LOCKDEP
sysrq_handle_showlocks(int key)213 static void sysrq_handle_showlocks(int key)
214 {
215 debug_show_all_locks();
216 }
217
218 static const struct sysrq_key_op sysrq_showlocks_op = {
219 .handler = sysrq_handle_showlocks,
220 .help_msg = "show-all-locks(d)",
221 .action_msg = "Show Locks Held",
222 };
223 #else
224 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
225 #endif
226
227 #ifdef CONFIG_SMP
228 static DEFINE_RAW_SPINLOCK(show_lock);
229
showacpu(void * dummy)230 static void showacpu(void *dummy)
231 {
232 unsigned long flags;
233
234 /* Idle CPUs have no interesting backtrace. */
235 if (idle_cpu(smp_processor_id()))
236 return;
237
238 raw_spin_lock_irqsave(&show_lock, flags);
239 pr_info("CPU%d:\n", smp_processor_id());
240 show_stack(NULL, NULL, KERN_INFO);
241 raw_spin_unlock_irqrestore(&show_lock, flags);
242 }
243
sysrq_showregs_othercpus(struct work_struct * dummy)244 static void sysrq_showregs_othercpus(struct work_struct *dummy)
245 {
246 smp_call_function(showacpu, NULL, 0);
247 }
248
249 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
250
sysrq_handle_showallcpus(int key)251 static void sysrq_handle_showallcpus(int key)
252 {
253 /*
254 * Fall back to the workqueue based printing if the
255 * backtrace printing did not succeed or the
256 * architecture has no support for it:
257 */
258 if (!trigger_all_cpu_backtrace()) {
259 struct pt_regs *regs = NULL;
260
261 if (in_hardirq())
262 regs = get_irq_regs();
263 if (regs) {
264 pr_info("CPU%d:\n", smp_processor_id());
265 show_regs(regs);
266 }
267 schedule_work(&sysrq_showallcpus);
268 }
269 }
270
271 static const struct sysrq_key_op sysrq_showallcpus_op = {
272 .handler = sysrq_handle_showallcpus,
273 .help_msg = "show-backtrace-all-active-cpus(l)",
274 .action_msg = "Show backtrace of all active CPUs",
275 .enable_mask = SYSRQ_ENABLE_DUMP,
276 };
277 #endif
278
sysrq_handle_showregs(int key)279 static void sysrq_handle_showregs(int key)
280 {
281 struct pt_regs *regs = NULL;
282
283 if (in_hardirq())
284 regs = get_irq_regs();
285 if (regs)
286 show_regs(regs);
287 perf_event_print_debug();
288 }
289 static const struct sysrq_key_op sysrq_showregs_op = {
290 .handler = sysrq_handle_showregs,
291 .help_msg = "show-registers(p)",
292 .action_msg = "Show Regs",
293 .enable_mask = SYSRQ_ENABLE_DUMP,
294 };
295
sysrq_handle_showstate(int key)296 static void sysrq_handle_showstate(int key)
297 {
298 show_state();
299 show_workqueue_state();
300 }
301 static const struct sysrq_key_op sysrq_showstate_op = {
302 .handler = sysrq_handle_showstate,
303 .help_msg = "show-task-states(t)",
304 .action_msg = "Show State",
305 .enable_mask = SYSRQ_ENABLE_DUMP,
306 };
307
sysrq_handle_showstate_blocked(int key)308 static void sysrq_handle_showstate_blocked(int key)
309 {
310 show_state_filter(TASK_UNINTERRUPTIBLE);
311 }
312 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
313 .handler = sysrq_handle_showstate_blocked,
314 .help_msg = "show-blocked-tasks(w)",
315 .action_msg = "Show Blocked State",
316 .enable_mask = SYSRQ_ENABLE_DUMP,
317 };
318
319 #ifdef CONFIG_TRACING
320 #include <linux/ftrace.h>
321
sysrq_ftrace_dump(int key)322 static void sysrq_ftrace_dump(int key)
323 {
324 ftrace_dump(DUMP_ALL);
325 }
326 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
327 .handler = sysrq_ftrace_dump,
328 .help_msg = "dump-ftrace-buffer(z)",
329 .action_msg = "Dump ftrace buffer",
330 .enable_mask = SYSRQ_ENABLE_DUMP,
331 };
332 #else
333 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
334 #endif
335
sysrq_handle_showmem(int key)336 static void sysrq_handle_showmem(int key)
337 {
338 show_mem(0, NULL);
339 }
340 static const struct sysrq_key_op sysrq_showmem_op = {
341 .handler = sysrq_handle_showmem,
342 .help_msg = "show-memory-usage(m)",
343 .action_msg = "Show Memory",
344 .enable_mask = SYSRQ_ENABLE_DUMP,
345 };
346
347 /*
348 * Signal sysrq helper function. Sends a signal to all user processes.
349 */
send_sig_all(int sig)350 static void send_sig_all(int sig)
351 {
352 struct task_struct *p;
353
354 read_lock(&tasklist_lock);
355 for_each_process(p) {
356 if (p->flags & PF_KTHREAD)
357 continue;
358 if (is_global_init(p))
359 continue;
360
361 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
362 }
363 read_unlock(&tasklist_lock);
364 }
365
sysrq_handle_term(int key)366 static void sysrq_handle_term(int key)
367 {
368 send_sig_all(SIGTERM);
369 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
370 }
371 static const struct sysrq_key_op sysrq_term_op = {
372 .handler = sysrq_handle_term,
373 .help_msg = "terminate-all-tasks(e)",
374 .action_msg = "Terminate All Tasks",
375 .enable_mask = SYSRQ_ENABLE_SIGNAL,
376 };
377
moom_callback(struct work_struct * ignored)378 static void moom_callback(struct work_struct *ignored)
379 {
380 const gfp_t gfp_mask = GFP_KERNEL;
381 struct oom_control oc = {
382 .zonelist = node_zonelist(first_memory_node, gfp_mask),
383 .nodemask = NULL,
384 .memcg = NULL,
385 .gfp_mask = gfp_mask,
386 .order = -1,
387 };
388
389 mutex_lock(&oom_lock);
390 if (!out_of_memory(&oc))
391 pr_info("OOM request ignored. No task eligible\n");
392 mutex_unlock(&oom_lock);
393 }
394
395 static DECLARE_WORK(moom_work, moom_callback);
396
sysrq_handle_moom(int key)397 static void sysrq_handle_moom(int key)
398 {
399 schedule_work(&moom_work);
400 }
401 static const struct sysrq_key_op sysrq_moom_op = {
402 .handler = sysrq_handle_moom,
403 .help_msg = "memory-full-oom-kill(f)",
404 .action_msg = "Manual OOM execution",
405 .enable_mask = SYSRQ_ENABLE_SIGNAL,
406 };
407
sysrq_handle_thaw(int key)408 static void sysrq_handle_thaw(int key)
409 {
410 emergency_thaw_all();
411 }
412 static const struct sysrq_key_op sysrq_thaw_op = {
413 .handler = sysrq_handle_thaw,
414 .help_msg = "thaw-filesystems(j)",
415 .action_msg = "Emergency Thaw of all frozen filesystems",
416 .enable_mask = SYSRQ_ENABLE_SIGNAL,
417 };
418
sysrq_handle_kill(int key)419 static void sysrq_handle_kill(int key)
420 {
421 send_sig_all(SIGKILL);
422 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
423 }
424 static const struct sysrq_key_op sysrq_kill_op = {
425 .handler = sysrq_handle_kill,
426 .help_msg = "kill-all-tasks(i)",
427 .action_msg = "Kill All Tasks",
428 .enable_mask = SYSRQ_ENABLE_SIGNAL,
429 };
430
sysrq_handle_unrt(int key)431 static void sysrq_handle_unrt(int key)
432 {
433 normalize_rt_tasks();
434 }
435 static const struct sysrq_key_op sysrq_unrt_op = {
436 .handler = sysrq_handle_unrt,
437 .help_msg = "nice-all-RT-tasks(n)",
438 .action_msg = "Nice All RT Tasks",
439 .enable_mask = SYSRQ_ENABLE_RTNICE,
440 };
441
442 /* Key Operations table and lock */
443 static DEFINE_SPINLOCK(sysrq_key_table_lock);
444
445 static const struct sysrq_key_op *sysrq_key_table[62] = {
446 &sysrq_loglevel_op, /* 0 */
447 &sysrq_loglevel_op, /* 1 */
448 &sysrq_loglevel_op, /* 2 */
449 &sysrq_loglevel_op, /* 3 */
450 &sysrq_loglevel_op, /* 4 */
451 &sysrq_loglevel_op, /* 5 */
452 &sysrq_loglevel_op, /* 6 */
453 &sysrq_loglevel_op, /* 7 */
454 &sysrq_loglevel_op, /* 8 */
455 &sysrq_loglevel_op, /* 9 */
456
457 /*
458 * a: Don't use for system provided sysrqs, it is handled specially on
459 * sparc and will never arrive.
460 */
461 NULL, /* a */
462 &sysrq_reboot_op, /* b */
463 &sysrq_crash_op, /* c */
464 &sysrq_showlocks_op, /* d */
465 &sysrq_term_op, /* e */
466 &sysrq_moom_op, /* f */
467 /* g: May be registered for the kernel debugger */
468 NULL, /* g */
469 NULL, /* h - reserved for help */
470 &sysrq_kill_op, /* i */
471 #ifdef CONFIG_BLOCK
472 &sysrq_thaw_op, /* j */
473 #else
474 NULL, /* j */
475 #endif
476 &sysrq_SAK_op, /* k */
477 #ifdef CONFIG_SMP
478 &sysrq_showallcpus_op, /* l */
479 #else
480 NULL, /* l */
481 #endif
482 &sysrq_showmem_op, /* m */
483 &sysrq_unrt_op, /* n */
484 /* o: This will often be registered as 'Off' at init time */
485 NULL, /* o */
486 &sysrq_showregs_op, /* p */
487 &sysrq_show_timers_op, /* q */
488 &sysrq_unraw_op, /* r */
489 &sysrq_sync_op, /* s */
490 &sysrq_showstate_op, /* t */
491 &sysrq_mountro_op, /* u */
492 /* v: May be registered for frame buffer console restore */
493 NULL, /* v */
494 &sysrq_showstate_blocked_op, /* w */
495 /* x: May be registered on mips for TLB dump */
496 /* x: May be registered on ppc/powerpc for xmon */
497 /* x: May be registered on sparc64 for global PMU dump */
498 NULL, /* x */
499 /* y: May be registered on sparc64 for global register dump */
500 NULL, /* y */
501 &sysrq_ftrace_dump_op, /* z */
502 NULL, /* A */
503 NULL, /* B */
504 NULL, /* C */
505 NULL, /* D */
506 NULL, /* E */
507 NULL, /* F */
508 NULL, /* G */
509 NULL, /* H */
510 NULL, /* I */
511 NULL, /* J */
512 NULL, /* K */
513 NULL, /* L */
514 NULL, /* M */
515 NULL, /* N */
516 NULL, /* O */
517 NULL, /* P */
518 NULL, /* Q */
519 NULL, /* R */
520 NULL, /* S */
521 NULL, /* T */
522 NULL, /* U */
523 NULL, /* V */
524 NULL, /* W */
525 NULL, /* X */
526 NULL, /* Y */
527 NULL, /* Z */
528 };
529
530 /* key2index calculation, -1 on invalid index */
sysrq_key_table_key2index(int key)531 static int sysrq_key_table_key2index(int key)
532 {
533 int retval;
534
535 if ((key >= '0') && (key <= '9'))
536 retval = key - '0';
537 else if ((key >= 'a') && (key <= 'z'))
538 retval = key + 10 - 'a';
539 else if ((key >= 'A') && (key <= 'Z'))
540 retval = key + 36 - 'A';
541 else
542 retval = -1;
543 return retval;
544 }
545
546 /*
547 * get and put functions for the table, exposed to modules.
548 */
__sysrq_get_key_op(int key)549 static const struct sysrq_key_op *__sysrq_get_key_op(int key)
550 {
551 const struct sysrq_key_op *op_p = NULL;
552 int i;
553
554 i = sysrq_key_table_key2index(key);
555 if (i != -1)
556 op_p = sysrq_key_table[i];
557
558 return op_p;
559 }
560
__sysrq_put_key_op(int key,const struct sysrq_key_op * op_p)561 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p)
562 {
563 int i = sysrq_key_table_key2index(key);
564
565 if (i != -1)
566 sysrq_key_table[i] = op_p;
567 }
568
__handle_sysrq(int key,bool check_mask)569 void __handle_sysrq(int key, bool check_mask)
570 {
571 const struct sysrq_key_op *op_p;
572 int orig_log_level;
573 int orig_suppress_printk;
574 int i;
575
576 orig_suppress_printk = suppress_printk;
577 suppress_printk = 0;
578
579 rcu_sysrq_start();
580 rcu_read_lock();
581 /*
582 * Raise the apparent loglevel to maximum so that the sysrq header
583 * is shown to provide the user with positive feedback. We do not
584 * simply emit this at KERN_EMERG as that would change message
585 * routing in the consumers of /proc/kmsg.
586 */
587 orig_log_level = console_loglevel;
588 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
589
590 op_p = __sysrq_get_key_op(key);
591 if (op_p) {
592 /*
593 * Should we check for enabled operations (/proc/sysrq-trigger
594 * should not) and is the invoked operation enabled?
595 */
596 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
597 pr_info("%s\n", op_p->action_msg);
598 console_loglevel = orig_log_level;
599 op_p->handler(key);
600 } else {
601 pr_info("This sysrq operation is disabled.\n");
602 console_loglevel = orig_log_level;
603 }
604 } else {
605 pr_info("HELP : ");
606 /* Only print the help msg once per handler */
607 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
608 if (sysrq_key_table[i]) {
609 int j;
610
611 for (j = 0; sysrq_key_table[i] !=
612 sysrq_key_table[j]; j++)
613 ;
614 if (j != i)
615 continue;
616 pr_cont("%s ", sysrq_key_table[i]->help_msg);
617 }
618 }
619 pr_cont("\n");
620 console_loglevel = orig_log_level;
621 }
622 rcu_read_unlock();
623 rcu_sysrq_end();
624
625 suppress_printk = orig_suppress_printk;
626 }
627
handle_sysrq(int key)628 void handle_sysrq(int key)
629 {
630 if (sysrq_on())
631 __handle_sysrq(key, true);
632 }
633 EXPORT_SYMBOL(handle_sysrq);
634
635 #ifdef CONFIG_INPUT
636 static int sysrq_reset_downtime_ms;
637
638 /* Simple translation table for the SysRq keys */
639 static const unsigned char sysrq_xlate[KEY_CNT] =
640 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
641 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
642 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
643 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
644 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
645 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
646 "\r\000/"; /* 0x60 - 0x6f */
647
648 struct sysrq_state {
649 struct input_handle handle;
650 struct work_struct reinject_work;
651 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
652 unsigned int alt;
653 unsigned int alt_use;
654 unsigned int shift;
655 unsigned int shift_use;
656 bool active;
657 bool need_reinject;
658 bool reinjecting;
659
660 /* reset sequence handling */
661 bool reset_canceled;
662 bool reset_requested;
663 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
664 int reset_seq_len;
665 int reset_seq_cnt;
666 int reset_seq_version;
667 struct timer_list keyreset_timer;
668 };
669
670 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
671 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
672 static unsigned int sysrq_reset_seq_len;
673 static unsigned int sysrq_reset_seq_version = 1;
674
sysrq_parse_reset_sequence(struct sysrq_state * state)675 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
676 {
677 int i;
678 unsigned short key;
679
680 state->reset_seq_cnt = 0;
681
682 for (i = 0; i < sysrq_reset_seq_len; i++) {
683 key = sysrq_reset_seq[i];
684
685 if (key == KEY_RESERVED || key > KEY_MAX)
686 break;
687
688 __set_bit(key, state->reset_keybit);
689 state->reset_seq_len++;
690
691 if (test_bit(key, state->key_down))
692 state->reset_seq_cnt++;
693 }
694
695 /* Disable reset until old keys are not released */
696 state->reset_canceled = state->reset_seq_cnt != 0;
697
698 state->reset_seq_version = sysrq_reset_seq_version;
699 }
700
sysrq_do_reset(struct timer_list * t)701 static void sysrq_do_reset(struct timer_list *t)
702 {
703 struct sysrq_state *state = from_timer(state, t, keyreset_timer);
704
705 state->reset_requested = true;
706
707 orderly_reboot();
708 }
709
sysrq_handle_reset_request(struct sysrq_state * state)710 static void sysrq_handle_reset_request(struct sysrq_state *state)
711 {
712 if (state->reset_requested)
713 __handle_sysrq(sysrq_xlate[KEY_B], false);
714
715 if (sysrq_reset_downtime_ms)
716 mod_timer(&state->keyreset_timer,
717 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
718 else
719 sysrq_do_reset(&state->keyreset_timer);
720 }
721
sysrq_detect_reset_sequence(struct sysrq_state * state,unsigned int code,int value)722 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
723 unsigned int code, int value)
724 {
725 if (!test_bit(code, state->reset_keybit)) {
726 /*
727 * Pressing any key _not_ in reset sequence cancels
728 * the reset sequence. Also cancelling the timer in
729 * case additional keys were pressed after a reset
730 * has been requested.
731 */
732 if (value && state->reset_seq_cnt) {
733 state->reset_canceled = true;
734 del_timer(&state->keyreset_timer);
735 }
736 } else if (value == 0) {
737 /*
738 * Key release - all keys in the reset sequence need
739 * to be pressed and held for the reset timeout
740 * to hold.
741 */
742 del_timer(&state->keyreset_timer);
743
744 if (--state->reset_seq_cnt == 0)
745 state->reset_canceled = false;
746 } else if (value == 1) {
747 /* key press, not autorepeat */
748 if (++state->reset_seq_cnt == state->reset_seq_len &&
749 !state->reset_canceled) {
750 sysrq_handle_reset_request(state);
751 }
752 }
753 }
754
755 #ifdef CONFIG_OF
sysrq_of_get_keyreset_config(void)756 static void sysrq_of_get_keyreset_config(void)
757 {
758 u32 key;
759 struct device_node *np;
760 struct property *prop;
761 const __be32 *p;
762
763 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
764 if (!np) {
765 pr_debug("No sysrq node found");
766 return;
767 }
768
769 /* Reset in case a __weak definition was present */
770 sysrq_reset_seq_len = 0;
771
772 of_property_for_each_u32(np, "keyset", prop, p, key) {
773 if (key == KEY_RESERVED || key > KEY_MAX ||
774 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
775 break;
776
777 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
778 }
779
780 /* Get reset timeout if any. */
781 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
782
783 of_node_put(np);
784 }
785 #else
sysrq_of_get_keyreset_config(void)786 static void sysrq_of_get_keyreset_config(void)
787 {
788 }
789 #endif
790
sysrq_reinject_alt_sysrq(struct work_struct * work)791 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
792 {
793 struct sysrq_state *sysrq =
794 container_of(work, struct sysrq_state, reinject_work);
795 struct input_handle *handle = &sysrq->handle;
796 unsigned int alt_code = sysrq->alt_use;
797
798 if (sysrq->need_reinject) {
799 /* we do not want the assignment to be reordered */
800 sysrq->reinjecting = true;
801 mb();
802
803 /* Simulate press and release of Alt + SysRq */
804 input_inject_event(handle, EV_KEY, alt_code, 1);
805 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
806 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
807
808 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
809 input_inject_event(handle, EV_KEY, alt_code, 0);
810 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
811
812 mb();
813 sysrq->reinjecting = false;
814 }
815 }
816
sysrq_handle_keypress(struct sysrq_state * sysrq,unsigned int code,int value)817 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
818 unsigned int code, int value)
819 {
820 bool was_active = sysrq->active;
821 bool suppress;
822
823 switch (code) {
824
825 case KEY_LEFTALT:
826 case KEY_RIGHTALT:
827 if (!value) {
828 /* One of ALTs is being released */
829 if (sysrq->active && code == sysrq->alt_use)
830 sysrq->active = false;
831
832 sysrq->alt = KEY_RESERVED;
833
834 } else if (value != 2) {
835 sysrq->alt = code;
836 sysrq->need_reinject = false;
837 }
838 break;
839
840 case KEY_LEFTSHIFT:
841 case KEY_RIGHTSHIFT:
842 if (!value)
843 sysrq->shift = KEY_RESERVED;
844 else if (value != 2)
845 sysrq->shift = code;
846 break;
847
848 case KEY_SYSRQ:
849 if (value == 1 && sysrq->alt != KEY_RESERVED) {
850 sysrq->active = true;
851 sysrq->alt_use = sysrq->alt;
852 /* either RESERVED (for released) or actual code */
853 sysrq->shift_use = sysrq->shift;
854 /*
855 * If nothing else will be pressed we'll need
856 * to re-inject Alt-SysRq keysroke.
857 */
858 sysrq->need_reinject = true;
859 }
860
861 /*
862 * Pretend that sysrq was never pressed at all. This
863 * is needed to properly handle KGDB which will try
864 * to release all keys after exiting debugger. If we
865 * do not clear key bit it KGDB will end up sending
866 * release events for Alt and SysRq, potentially
867 * triggering print screen function.
868 */
869 if (sysrq->active)
870 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
871
872 break;
873
874 default:
875 if (sysrq->active && value && value != 2) {
876 unsigned char c = sysrq_xlate[code];
877
878 sysrq->need_reinject = false;
879 if (sysrq->shift_use != KEY_RESERVED)
880 c = toupper(c);
881 __handle_sysrq(c, true);
882 }
883 break;
884 }
885
886 suppress = sysrq->active;
887
888 if (!sysrq->active) {
889
890 /*
891 * See if reset sequence has changed since the last time.
892 */
893 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
894 sysrq_parse_reset_sequence(sysrq);
895
896 /*
897 * If we are not suppressing key presses keep track of
898 * keyboard state so we can release keys that have been
899 * pressed before entering SysRq mode.
900 */
901 if (value)
902 set_bit(code, sysrq->key_down);
903 else
904 clear_bit(code, sysrq->key_down);
905
906 if (was_active)
907 schedule_work(&sysrq->reinject_work);
908
909 /* Check for reset sequence */
910 sysrq_detect_reset_sequence(sysrq, code, value);
911
912 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
913 /*
914 * Pass on release events for keys that was pressed before
915 * entering SysRq mode.
916 */
917 suppress = false;
918 }
919
920 return suppress;
921 }
922
sysrq_filter(struct input_handle * handle,unsigned int type,unsigned int code,int value)923 static bool sysrq_filter(struct input_handle *handle,
924 unsigned int type, unsigned int code, int value)
925 {
926 struct sysrq_state *sysrq = handle->private;
927 bool suppress;
928
929 /*
930 * Do not filter anything if we are in the process of re-injecting
931 * Alt+SysRq combination.
932 */
933 if (sysrq->reinjecting)
934 return false;
935
936 switch (type) {
937
938 case EV_SYN:
939 suppress = false;
940 break;
941
942 case EV_KEY:
943 suppress = sysrq_handle_keypress(sysrq, code, value);
944 break;
945
946 default:
947 suppress = sysrq->active;
948 break;
949 }
950
951 return suppress;
952 }
953
sysrq_connect(struct input_handler * handler,struct input_dev * dev,const struct input_device_id * id)954 static int sysrq_connect(struct input_handler *handler,
955 struct input_dev *dev,
956 const struct input_device_id *id)
957 {
958 struct sysrq_state *sysrq;
959 int error;
960
961 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
962 if (!sysrq)
963 return -ENOMEM;
964
965 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
966
967 sysrq->handle.dev = dev;
968 sysrq->handle.handler = handler;
969 sysrq->handle.name = "sysrq";
970 sysrq->handle.private = sysrq;
971 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
972
973 error = input_register_handle(&sysrq->handle);
974 if (error) {
975 pr_err("Failed to register input sysrq handler, error %d\n",
976 error);
977 goto err_free;
978 }
979
980 error = input_open_device(&sysrq->handle);
981 if (error) {
982 pr_err("Failed to open input device, error %d\n", error);
983 goto err_unregister;
984 }
985
986 return 0;
987
988 err_unregister:
989 input_unregister_handle(&sysrq->handle);
990 err_free:
991 kfree(sysrq);
992 return error;
993 }
994
sysrq_disconnect(struct input_handle * handle)995 static void sysrq_disconnect(struct input_handle *handle)
996 {
997 struct sysrq_state *sysrq = handle->private;
998
999 input_close_device(handle);
1000 cancel_work_sync(&sysrq->reinject_work);
1001 del_timer_sync(&sysrq->keyreset_timer);
1002 input_unregister_handle(handle);
1003 kfree(sysrq);
1004 }
1005
1006 /*
1007 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1008 * keyboards have SysRq key predefined and so user may add it to keymap
1009 * later, but we expect all such keyboards to have left alt.
1010 */
1011 static const struct input_device_id sysrq_ids[] = {
1012 {
1013 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1014 INPUT_DEVICE_ID_MATCH_KEYBIT,
1015 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1016 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1017 },
1018 { },
1019 };
1020
1021 static struct input_handler sysrq_handler = {
1022 .filter = sysrq_filter,
1023 .connect = sysrq_connect,
1024 .disconnect = sysrq_disconnect,
1025 .name = "sysrq",
1026 .id_table = sysrq_ids,
1027 };
1028
sysrq_register_handler(void)1029 static inline void sysrq_register_handler(void)
1030 {
1031 int error;
1032
1033 sysrq_of_get_keyreset_config();
1034
1035 error = input_register_handler(&sysrq_handler);
1036 if (error)
1037 pr_err("Failed to register input handler, error %d", error);
1038 }
1039
sysrq_unregister_handler(void)1040 static inline void sysrq_unregister_handler(void)
1041 {
1042 input_unregister_handler(&sysrq_handler);
1043 }
1044
sysrq_reset_seq_param_set(const char * buffer,const struct kernel_param * kp)1045 static int sysrq_reset_seq_param_set(const char *buffer,
1046 const struct kernel_param *kp)
1047 {
1048 unsigned long val;
1049 int error;
1050
1051 error = kstrtoul(buffer, 0, &val);
1052 if (error < 0)
1053 return error;
1054
1055 if (val > KEY_MAX)
1056 return -EINVAL;
1057
1058 *((unsigned short *)kp->arg) = val;
1059 sysrq_reset_seq_version++;
1060
1061 return 0;
1062 }
1063
1064 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1065 .get = param_get_ushort,
1066 .set = sysrq_reset_seq_param_set,
1067 };
1068
1069 #define param_check_sysrq_reset_seq(name, p) \
1070 __param_check(name, p, unsigned short)
1071
1072 /*
1073 * not really modular, but the easiest way to keep compat with existing
1074 * bootargs behaviour is to continue using module_param here.
1075 */
1076 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1077 &sysrq_reset_seq_len, 0644);
1078
1079 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1080
1081 #else
1082
sysrq_register_handler(void)1083 static inline void sysrq_register_handler(void)
1084 {
1085 }
1086
sysrq_unregister_handler(void)1087 static inline void sysrq_unregister_handler(void)
1088 {
1089 }
1090
1091 #endif /* CONFIG_INPUT */
1092
sysrq_toggle_support(int enable_mask)1093 int sysrq_toggle_support(int enable_mask)
1094 {
1095 bool was_enabled = sysrq_on();
1096
1097 sysrq_enabled = enable_mask;
1098
1099 if (was_enabled != sysrq_on()) {
1100 if (sysrq_on())
1101 sysrq_register_handler();
1102 else
1103 sysrq_unregister_handler();
1104 }
1105
1106 return 0;
1107 }
1108 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1109
__sysrq_swap_key_ops(int key,const struct sysrq_key_op * insert_op_p,const struct sysrq_key_op * remove_op_p)1110 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p,
1111 const struct sysrq_key_op *remove_op_p)
1112 {
1113 int retval;
1114
1115 spin_lock(&sysrq_key_table_lock);
1116 if (__sysrq_get_key_op(key) == remove_op_p) {
1117 __sysrq_put_key_op(key, insert_op_p);
1118 retval = 0;
1119 } else {
1120 retval = -1;
1121 }
1122 spin_unlock(&sysrq_key_table_lock);
1123
1124 /*
1125 * A concurrent __handle_sysrq either got the old op or the new op.
1126 * Wait for it to go away before returning, so the code for an old
1127 * op is not freed (eg. on module unload) while it is in use.
1128 */
1129 synchronize_rcu();
1130
1131 return retval;
1132 }
1133
register_sysrq_key(int key,const struct sysrq_key_op * op_p)1134 int register_sysrq_key(int key, const struct sysrq_key_op *op_p)
1135 {
1136 return __sysrq_swap_key_ops(key, op_p, NULL);
1137 }
1138 EXPORT_SYMBOL(register_sysrq_key);
1139
unregister_sysrq_key(int key,const struct sysrq_key_op * op_p)1140 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)
1141 {
1142 return __sysrq_swap_key_ops(key, NULL, op_p);
1143 }
1144 EXPORT_SYMBOL(unregister_sysrq_key);
1145
1146 #ifdef CONFIG_PROC_FS
1147 /*
1148 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1149 */
write_sysrq_trigger(struct file * file,const char __user * buf,size_t count,loff_t * ppos)1150 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1151 size_t count, loff_t *ppos)
1152 {
1153 if (count) {
1154 char c;
1155
1156 if (get_user(c, buf))
1157 return -EFAULT;
1158 __handle_sysrq(c, false);
1159 }
1160
1161 return count;
1162 }
1163
1164 static const struct proc_ops sysrq_trigger_proc_ops = {
1165 .proc_write = write_sysrq_trigger,
1166 .proc_lseek = noop_llseek,
1167 };
1168
sysrq_init_procfs(void)1169 static void sysrq_init_procfs(void)
1170 {
1171 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1172 &sysrq_trigger_proc_ops))
1173 pr_err("Failed to register proc interface\n");
1174 }
1175
1176 #else
1177
sysrq_init_procfs(void)1178 static inline void sysrq_init_procfs(void)
1179 {
1180 }
1181
1182 #endif /* CONFIG_PROC_FS */
1183
sysrq_init(void)1184 static int __init sysrq_init(void)
1185 {
1186 sysrq_init_procfs();
1187
1188 if (sysrq_on())
1189 sysrq_register_handler();
1190
1191 return 0;
1192 }
1193 device_initcall(sysrq_init);
1194
