1 /*
2 * Linux Magic System Request Key Hacks
3 *
4 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
5 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
6 *
7 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
8 * overhauled to use key registration
9 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies
10 *
11 * Copyright (c) 2010 Dmitry Torokhov
12 * Input handler conversion
13 */
14
15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
16
17 #include <linux/sched.h>
18 #include <linux/interrupt.h>
19 #include <linux/mm.h>
20 #include <linux/fs.h>
21 #include <linux/mount.h>
22 #include <linux/kdev_t.h>
23 #include <linux/major.h>
24 #include <linux/reboot.h>
25 #include <linux/sysrq.h>
26 #include <linux/kbd_kern.h>
27 #include <linux/proc_fs.h>
28 #include <linux/nmi.h>
29 #include <linux/quotaops.h>
30 #include <linux/perf_event.h>
31 #include <linux/kernel.h>
32 #include <linux/module.h>
33 #include <linux/suspend.h>
34 #include <linux/writeback.h>
35 #include <linux/buffer_head.h> /* for fsync_bdev() */
36 #include <linux/swap.h>
37 #include <linux/spinlock.h>
38 #include <linux/vt_kern.h>
39 #include <linux/workqueue.h>
40 #include <linux/hrtimer.h>
41 #include <linux/oom.h>
42 #include <linux/slab.h>
43 #include <linux/input.h>
44
45 #include <asm/ptrace.h>
46 #include <asm/irq_regs.h>
47
48 /* Whether we react on sysrq keys or just ignore them */
49 static int __read_mostly sysrq_enabled = SYSRQ_DEFAULT_ENABLE;
50 static bool __read_mostly sysrq_always_enabled;
51
sysrq_on(void)52 static bool sysrq_on(void)
53 {
54 return sysrq_enabled || sysrq_always_enabled;
55 }
56
57 /*
58 * A value of 1 means 'all', other nonzero values are an op mask:
59 */
sysrq_on_mask(int mask)60 static bool sysrq_on_mask(int mask)
61 {
62 return sysrq_always_enabled ||
63 sysrq_enabled == 1 ||
64 (sysrq_enabled & mask);
65 }
66
sysrq_always_enabled_setup(char * str)67 static int __init sysrq_always_enabled_setup(char *str)
68 {
69 sysrq_always_enabled = true;
70 pr_info("sysrq always enabled.\n");
71
72 return 1;
73 }
74
75 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
76
77
sysrq_handle_loglevel(int key)78 static void sysrq_handle_loglevel(int key)
79 {
80 int i;
81
82 i = key - '0';
83 console_loglevel = 7;
84 printk("Loglevel set to %d\n", i);
85 console_loglevel = i;
86 }
87 static struct sysrq_key_op sysrq_loglevel_op = {
88 .handler = sysrq_handle_loglevel,
89 .help_msg = "loglevel(0-9)",
90 .action_msg = "Changing Loglevel",
91 .enable_mask = SYSRQ_ENABLE_LOG,
92 };
93
94 #ifdef CONFIG_VT
sysrq_handle_SAK(int key)95 static void sysrq_handle_SAK(int key)
96 {
97 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
98 schedule_work(SAK_work);
99 }
100 static struct sysrq_key_op sysrq_SAK_op = {
101 .handler = sysrq_handle_SAK,
102 .help_msg = "saK",
103 .action_msg = "SAK",
104 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
105 };
106 #else
107 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
108 #endif
109
110 #ifdef CONFIG_VT
sysrq_handle_unraw(int key)111 static void sysrq_handle_unraw(int key)
112 {
113 struct kbd_struct *kbd = &kbd_table[fg_console];
114
115 if (kbd)
116 kbd->kbdmode = default_utf8 ? VC_UNICODE : VC_XLATE;
117 }
118 static struct sysrq_key_op sysrq_unraw_op = {
119 .handler = sysrq_handle_unraw,
120 .help_msg = "unRaw",
121 .action_msg = "Keyboard mode set to system default",
122 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
123 };
124 #else
125 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
126 #endif /* CONFIG_VT */
127
sysrq_handle_crash(int key)128 static void sysrq_handle_crash(int key)
129 {
130 char *killer = NULL;
131
132 panic_on_oops = 1; /* force panic */
133 wmb();
134 *killer = 1;
135 }
136 static struct sysrq_key_op sysrq_crash_op = {
137 .handler = sysrq_handle_crash,
138 .help_msg = "Crash",
139 .action_msg = "Trigger a crash",
140 .enable_mask = SYSRQ_ENABLE_DUMP,
141 };
142
sysrq_handle_reboot(int key)143 static void sysrq_handle_reboot(int key)
144 {
145 lockdep_off();
146 local_irq_enable();
147 emergency_restart();
148 }
149 static struct sysrq_key_op sysrq_reboot_op = {
150 .handler = sysrq_handle_reboot,
151 .help_msg = "reBoot",
152 .action_msg = "Resetting",
153 .enable_mask = SYSRQ_ENABLE_BOOT,
154 };
155
sysrq_handle_sync(int key)156 static void sysrq_handle_sync(int key)
157 {
158 emergency_sync();
159 }
160 static struct sysrq_key_op sysrq_sync_op = {
161 .handler = sysrq_handle_sync,
162 .help_msg = "Sync",
163 .action_msg = "Emergency Sync",
164 .enable_mask = SYSRQ_ENABLE_SYNC,
165 };
166
sysrq_handle_show_timers(int key)167 static void sysrq_handle_show_timers(int key)
168 {
169 sysrq_timer_list_show();
170 }
171
172 static struct sysrq_key_op sysrq_show_timers_op = {
173 .handler = sysrq_handle_show_timers,
174 .help_msg = "show-all-timers(Q)",
175 .action_msg = "Show clockevent devices & pending hrtimers (no others)",
176 };
177
sysrq_handle_mountro(int key)178 static void sysrq_handle_mountro(int key)
179 {
180 emergency_remount();
181 }
182 static struct sysrq_key_op sysrq_mountro_op = {
183 .handler = sysrq_handle_mountro,
184 .help_msg = "Unmount",
185 .action_msg = "Emergency Remount R/O",
186 .enable_mask = SYSRQ_ENABLE_REMOUNT,
187 };
188
189 #ifdef CONFIG_LOCKDEP
sysrq_handle_showlocks(int key)190 static void sysrq_handle_showlocks(int key)
191 {
192 debug_show_all_locks();
193 }
194
195 static struct sysrq_key_op sysrq_showlocks_op = {
196 .handler = sysrq_handle_showlocks,
197 .help_msg = "show-all-locks(D)",
198 .action_msg = "Show Locks Held",
199 };
200 #else
201 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
202 #endif
203
204 #ifdef CONFIG_SMP
205 static DEFINE_SPINLOCK(show_lock);
206
showacpu(void * dummy)207 static void showacpu(void *dummy)
208 {
209 unsigned long flags;
210
211 /* Idle CPUs have no interesting backtrace. */
212 if (idle_cpu(smp_processor_id()))
213 return;
214
215 spin_lock_irqsave(&show_lock, flags);
216 printk(KERN_INFO "CPU%d:\n", smp_processor_id());
217 show_stack(NULL, NULL);
218 spin_unlock_irqrestore(&show_lock, flags);
219 }
220
sysrq_showregs_othercpus(struct work_struct * dummy)221 static void sysrq_showregs_othercpus(struct work_struct *dummy)
222 {
223 smp_call_function(showacpu, NULL, 0);
224 }
225
226 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
227
sysrq_handle_showallcpus(int key)228 static void sysrq_handle_showallcpus(int key)
229 {
230 /*
231 * Fall back to the workqueue based printing if the
232 * backtrace printing did not succeed or the
233 * architecture has no support for it:
234 */
235 if (!trigger_all_cpu_backtrace()) {
236 struct pt_regs *regs = get_irq_regs();
237
238 if (regs) {
239 printk(KERN_INFO "CPU%d:\n", smp_processor_id());
240 show_regs(regs);
241 }
242 schedule_work(&sysrq_showallcpus);
243 }
244 }
245
246 static struct sysrq_key_op sysrq_showallcpus_op = {
247 .handler = sysrq_handle_showallcpus,
248 .help_msg = "show-backtrace-all-active-cpus(L)",
249 .action_msg = "Show backtrace of all active CPUs",
250 .enable_mask = SYSRQ_ENABLE_DUMP,
251 };
252 #endif
253
sysrq_handle_showregs(int key)254 static void sysrq_handle_showregs(int key)
255 {
256 struct pt_regs *regs = get_irq_regs();
257 if (regs)
258 show_regs(regs);
259 perf_event_print_debug();
260 }
261 static struct sysrq_key_op sysrq_showregs_op = {
262 .handler = sysrq_handle_showregs,
263 .help_msg = "show-registers(P)",
264 .action_msg = "Show Regs",
265 .enable_mask = SYSRQ_ENABLE_DUMP,
266 };
267
sysrq_handle_showstate(int key)268 static void sysrq_handle_showstate(int key)
269 {
270 show_state();
271 }
272 static struct sysrq_key_op sysrq_showstate_op = {
273 .handler = sysrq_handle_showstate,
274 .help_msg = "show-task-states(T)",
275 .action_msg = "Show State",
276 .enable_mask = SYSRQ_ENABLE_DUMP,
277 };
278
sysrq_handle_showstate_blocked(int key)279 static void sysrq_handle_showstate_blocked(int key)
280 {
281 show_state_filter(TASK_UNINTERRUPTIBLE);
282 }
283 static struct sysrq_key_op sysrq_showstate_blocked_op = {
284 .handler = sysrq_handle_showstate_blocked,
285 .help_msg = "show-blocked-tasks(W)",
286 .action_msg = "Show Blocked State",
287 .enable_mask = SYSRQ_ENABLE_DUMP,
288 };
289
290 #ifdef CONFIG_TRACING
291 #include <linux/ftrace.h>
292
sysrq_ftrace_dump(int key)293 static void sysrq_ftrace_dump(int key)
294 {
295 ftrace_dump(DUMP_ALL);
296 }
297 static struct sysrq_key_op sysrq_ftrace_dump_op = {
298 .handler = sysrq_ftrace_dump,
299 .help_msg = "dump-ftrace-buffer(Z)",
300 .action_msg = "Dump ftrace buffer",
301 .enable_mask = SYSRQ_ENABLE_DUMP,
302 };
303 #else
304 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
305 #endif
306
sysrq_handle_showmem(int key)307 static void sysrq_handle_showmem(int key)
308 {
309 show_mem(0);
310 }
311 static struct sysrq_key_op sysrq_showmem_op = {
312 .handler = sysrq_handle_showmem,
313 .help_msg = "show-memory-usage(M)",
314 .action_msg = "Show Memory",
315 .enable_mask = SYSRQ_ENABLE_DUMP,
316 };
317
318 /*
319 * Signal sysrq helper function. Sends a signal to all user processes.
320 */
send_sig_all(int sig)321 static void send_sig_all(int sig)
322 {
323 struct task_struct *p;
324
325 for_each_process(p) {
326 if (p->mm && !is_global_init(p))
327 /* Not swapper, init nor kernel thread */
328 force_sig(sig, p);
329 }
330 }
331
sysrq_handle_term(int key)332 static void sysrq_handle_term(int key)
333 {
334 send_sig_all(SIGTERM);
335 console_loglevel = 8;
336 }
337 static struct sysrq_key_op sysrq_term_op = {
338 .handler = sysrq_handle_term,
339 .help_msg = "terminate-all-tasks(E)",
340 .action_msg = "Terminate All Tasks",
341 .enable_mask = SYSRQ_ENABLE_SIGNAL,
342 };
343
moom_callback(struct work_struct * ignored)344 static void moom_callback(struct work_struct *ignored)
345 {
346 out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0, NULL);
347 }
348
349 static DECLARE_WORK(moom_work, moom_callback);
350
sysrq_handle_moom(int key)351 static void sysrq_handle_moom(int key)
352 {
353 schedule_work(&moom_work);
354 }
355 static struct sysrq_key_op sysrq_moom_op = {
356 .handler = sysrq_handle_moom,
357 .help_msg = "memory-full-oom-kill(F)",
358 .action_msg = "Manual OOM execution",
359 .enable_mask = SYSRQ_ENABLE_SIGNAL,
360 };
361
362 #ifdef CONFIG_BLOCK
sysrq_handle_thaw(int key)363 static void sysrq_handle_thaw(int key)
364 {
365 emergency_thaw_all();
366 }
367 static struct sysrq_key_op sysrq_thaw_op = {
368 .handler = sysrq_handle_thaw,
369 .help_msg = "thaw-filesystems(J)",
370 .action_msg = "Emergency Thaw of all frozen filesystems",
371 .enable_mask = SYSRQ_ENABLE_SIGNAL,
372 };
373 #endif
374
sysrq_handle_kill(int key)375 static void sysrq_handle_kill(int key)
376 {
377 send_sig_all(SIGKILL);
378 console_loglevel = 8;
379 }
380 static struct sysrq_key_op sysrq_kill_op = {
381 .handler = sysrq_handle_kill,
382 .help_msg = "kill-all-tasks(I)",
383 .action_msg = "Kill All Tasks",
384 .enable_mask = SYSRQ_ENABLE_SIGNAL,
385 };
386
sysrq_handle_unrt(int key)387 static void sysrq_handle_unrt(int key)
388 {
389 normalize_rt_tasks();
390 }
391 static struct sysrq_key_op sysrq_unrt_op = {
392 .handler = sysrq_handle_unrt,
393 .help_msg = "nice-all-RT-tasks(N)",
394 .action_msg = "Nice All RT Tasks",
395 .enable_mask = SYSRQ_ENABLE_RTNICE,
396 };
397
398 /* Key Operations table and lock */
399 static DEFINE_SPINLOCK(sysrq_key_table_lock);
400
401 static struct sysrq_key_op *sysrq_key_table[36] = {
402 &sysrq_loglevel_op, /* 0 */
403 &sysrq_loglevel_op, /* 1 */
404 &sysrq_loglevel_op, /* 2 */
405 &sysrq_loglevel_op, /* 3 */
406 &sysrq_loglevel_op, /* 4 */
407 &sysrq_loglevel_op, /* 5 */
408 &sysrq_loglevel_op, /* 6 */
409 &sysrq_loglevel_op, /* 7 */
410 &sysrq_loglevel_op, /* 8 */
411 &sysrq_loglevel_op, /* 9 */
412
413 /*
414 * a: Don't use for system provided sysrqs, it is handled specially on
415 * sparc and will never arrive.
416 */
417 NULL, /* a */
418 &sysrq_reboot_op, /* b */
419 &sysrq_crash_op, /* c & ibm_emac driver debug */
420 &sysrq_showlocks_op, /* d */
421 &sysrq_term_op, /* e */
422 &sysrq_moom_op, /* f */
423 /* g: May be registered for the kernel debugger */
424 NULL, /* g */
425 NULL, /* h - reserved for help */
426 &sysrq_kill_op, /* i */
427 #ifdef CONFIG_BLOCK
428 &sysrq_thaw_op, /* j */
429 #else
430 NULL, /* j */
431 #endif
432 &sysrq_SAK_op, /* k */
433 #ifdef CONFIG_SMP
434 &sysrq_showallcpus_op, /* l */
435 #else
436 NULL, /* l */
437 #endif
438 &sysrq_showmem_op, /* m */
439 &sysrq_unrt_op, /* n */
440 /* o: This will often be registered as 'Off' at init time */
441 NULL, /* o */
442 &sysrq_showregs_op, /* p */
443 &sysrq_show_timers_op, /* q */
444 &sysrq_unraw_op, /* r */
445 &sysrq_sync_op, /* s */
446 &sysrq_showstate_op, /* t */
447 &sysrq_mountro_op, /* u */
448 /* v: May be registered for frame buffer console restore */
449 NULL, /* v */
450 &sysrq_showstate_blocked_op, /* w */
451 /* x: May be registered on ppc/powerpc for xmon */
452 NULL, /* x */
453 /* y: May be registered on sparc64 for global register dump */
454 NULL, /* y */
455 &sysrq_ftrace_dump_op, /* z */
456 };
457
458 /* key2index calculation, -1 on invalid index */
sysrq_key_table_key2index(int key)459 static int sysrq_key_table_key2index(int key)
460 {
461 int retval;
462
463 if ((key >= '0') && (key <= '9'))
464 retval = key - '0';
465 else if ((key >= 'a') && (key <= 'z'))
466 retval = key + 10 - 'a';
467 else
468 retval = -1;
469 return retval;
470 }
471
472 /*
473 * get and put functions for the table, exposed to modules.
474 */
__sysrq_get_key_op(int key)475 struct sysrq_key_op *__sysrq_get_key_op(int key)
476 {
477 struct sysrq_key_op *op_p = NULL;
478 int i;
479
480 i = sysrq_key_table_key2index(key);
481 if (i != -1)
482 op_p = sysrq_key_table[i];
483
484 return op_p;
485 }
486
__sysrq_put_key_op(int key,struct sysrq_key_op * op_p)487 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
488 {
489 int i = sysrq_key_table_key2index(key);
490
491 if (i != -1)
492 sysrq_key_table[i] = op_p;
493 }
494
__handle_sysrq(int key,bool check_mask)495 void __handle_sysrq(int key, bool check_mask)
496 {
497 struct sysrq_key_op *op_p;
498 int orig_log_level;
499 int i;
500 unsigned long flags;
501
502 spin_lock_irqsave(&sysrq_key_table_lock, flags);
503 /*
504 * Raise the apparent loglevel to maximum so that the sysrq header
505 * is shown to provide the user with positive feedback. We do not
506 * simply emit this at KERN_EMERG as that would change message
507 * routing in the consumers of /proc/kmsg.
508 */
509 orig_log_level = console_loglevel;
510 console_loglevel = 7;
511 printk(KERN_INFO "SysRq : ");
512
513 op_p = __sysrq_get_key_op(key);
514 if (op_p) {
515 /*
516 * Should we check for enabled operations (/proc/sysrq-trigger
517 * should not) and is the invoked operation enabled?
518 */
519 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
520 printk("%s\n", op_p->action_msg);
521 console_loglevel = orig_log_level;
522 op_p->handler(key);
523 } else {
524 printk("This sysrq operation is disabled.\n");
525 }
526 } else {
527 printk("HELP : ");
528 /* Only print the help msg once per handler */
529 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
530 if (sysrq_key_table[i]) {
531 int j;
532
533 for (j = 0; sysrq_key_table[i] !=
534 sysrq_key_table[j]; j++)
535 ;
536 if (j != i)
537 continue;
538 printk("%s ", sysrq_key_table[i]->help_msg);
539 }
540 }
541 printk("\n");
542 console_loglevel = orig_log_level;
543 }
544 spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
545 }
546
handle_sysrq(int key)547 void handle_sysrq(int key)
548 {
549 if (sysrq_on())
550 __handle_sysrq(key, true);
551 }
552 EXPORT_SYMBOL(handle_sysrq);
553
554 #ifdef CONFIG_INPUT
555
556 /* Simple translation table for the SysRq keys */
557 static const unsigned char sysrq_xlate[KEY_CNT] =
558 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
559 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
560 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
561 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
562 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
563 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
564 "\r\000/"; /* 0x60 - 0x6f */
565
566 struct sysrq_state {
567 struct input_handle handle;
568 struct work_struct reinject_work;
569 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
570 unsigned int alt;
571 unsigned int alt_use;
572 bool active;
573 bool need_reinject;
574 bool reinjecting;
575 };
576
sysrq_reinject_alt_sysrq(struct work_struct * work)577 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
578 {
579 struct sysrq_state *sysrq =
580 container_of(work, struct sysrq_state, reinject_work);
581 struct input_handle *handle = &sysrq->handle;
582 unsigned int alt_code = sysrq->alt_use;
583
584 if (sysrq->need_reinject) {
585 /* we do not want the assignment to be reordered */
586 sysrq->reinjecting = true;
587 mb();
588
589 /* Simulate press and release of Alt + SysRq */
590 input_inject_event(handle, EV_KEY, alt_code, 1);
591 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
592 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
593
594 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
595 input_inject_event(handle, EV_KEY, alt_code, 0);
596 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
597
598 mb();
599 sysrq->reinjecting = false;
600 }
601 }
602
sysrq_filter(struct input_handle * handle,unsigned int type,unsigned int code,int value)603 static bool sysrq_filter(struct input_handle *handle,
604 unsigned int type, unsigned int code, int value)
605 {
606 struct sysrq_state *sysrq = handle->private;
607 bool was_active = sysrq->active;
608 bool suppress;
609
610 /*
611 * Do not filter anything if we are in the process of re-injecting
612 * Alt+SysRq combination.
613 */
614 if (sysrq->reinjecting)
615 return false;
616
617 switch (type) {
618
619 case EV_SYN:
620 suppress = false;
621 break;
622
623 case EV_KEY:
624 switch (code) {
625
626 case KEY_LEFTALT:
627 case KEY_RIGHTALT:
628 if (!value) {
629 /* One of ALTs is being released */
630 if (sysrq->active && code == sysrq->alt_use)
631 sysrq->active = false;
632
633 sysrq->alt = KEY_RESERVED;
634
635 } else if (value != 2) {
636 sysrq->alt = code;
637 sysrq->need_reinject = false;
638 }
639 break;
640
641 case KEY_SYSRQ:
642 if (value == 1 && sysrq->alt != KEY_RESERVED) {
643 sysrq->active = true;
644 sysrq->alt_use = sysrq->alt;
645 /*
646 * If nothing else will be pressed we'll need
647 * to re-inject Alt-SysRq keysroke.
648 */
649 sysrq->need_reinject = true;
650 }
651
652 /*
653 * Pretend that sysrq was never pressed at all. This
654 * is needed to properly handle KGDB which will try
655 * to release all keys after exiting debugger. If we
656 * do not clear key bit it KGDB will end up sending
657 * release events for Alt and SysRq, potentially
658 * triggering print screen function.
659 */
660 if (sysrq->active)
661 clear_bit(KEY_SYSRQ, handle->dev->key);
662
663 break;
664
665 default:
666 if (sysrq->active && value && value != 2) {
667 sysrq->need_reinject = false;
668 __handle_sysrq(sysrq_xlate[code], true);
669 }
670 break;
671 }
672
673 suppress = sysrq->active;
674
675 if (!sysrq->active) {
676 /*
677 * If we are not suppressing key presses keep track of
678 * keyboard state so we can release keys that have been
679 * pressed before entering SysRq mode.
680 */
681 if (value)
682 set_bit(code, sysrq->key_down);
683 else
684 clear_bit(code, sysrq->key_down);
685
686 if (was_active)
687 schedule_work(&sysrq->reinject_work);
688
689 } else if (value == 0 &&
690 test_and_clear_bit(code, sysrq->key_down)) {
691 /*
692 * Pass on release events for keys that was pressed before
693 * entering SysRq mode.
694 */
695 suppress = false;
696 }
697 break;
698
699 default:
700 suppress = sysrq->active;
701 break;
702 }
703
704 return suppress;
705 }
706
sysrq_connect(struct input_handler * handler,struct input_dev * dev,const struct input_device_id * id)707 static int sysrq_connect(struct input_handler *handler,
708 struct input_dev *dev,
709 const struct input_device_id *id)
710 {
711 struct sysrq_state *sysrq;
712 int error;
713
714 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
715 if (!sysrq)
716 return -ENOMEM;
717
718 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
719
720 sysrq->handle.dev = dev;
721 sysrq->handle.handler = handler;
722 sysrq->handle.name = "sysrq";
723 sysrq->handle.private = sysrq;
724
725 error = input_register_handle(&sysrq->handle);
726 if (error) {
727 pr_err("Failed to register input sysrq handler, error %d\n",
728 error);
729 goto err_free;
730 }
731
732 error = input_open_device(&sysrq->handle);
733 if (error) {
734 pr_err("Failed to open input device, error %d\n", error);
735 goto err_unregister;
736 }
737
738 return 0;
739
740 err_unregister:
741 input_unregister_handle(&sysrq->handle);
742 err_free:
743 kfree(sysrq);
744 return error;
745 }
746
sysrq_disconnect(struct input_handle * handle)747 static void sysrq_disconnect(struct input_handle *handle)
748 {
749 struct sysrq_state *sysrq = handle->private;
750
751 input_close_device(handle);
752 cancel_work_sync(&sysrq->reinject_work);
753 input_unregister_handle(handle);
754 kfree(sysrq);
755 }
756
757 /*
758 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
759 * keyboards have SysRq key predefined and so user may add it to keymap
760 * later, but we expect all such keyboards to have left alt.
761 */
762 static const struct input_device_id sysrq_ids[] = {
763 {
764 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
765 INPUT_DEVICE_ID_MATCH_KEYBIT,
766 .evbit = { BIT_MASK(EV_KEY) },
767 .keybit = { BIT_MASK(KEY_LEFTALT) },
768 },
769 { },
770 };
771
772 static struct input_handler sysrq_handler = {
773 .filter = sysrq_filter,
774 .connect = sysrq_connect,
775 .disconnect = sysrq_disconnect,
776 .name = "sysrq",
777 .id_table = sysrq_ids,
778 };
779
780 static bool sysrq_handler_registered;
781
sysrq_register_handler(void)782 static inline void sysrq_register_handler(void)
783 {
784 int error;
785
786 error = input_register_handler(&sysrq_handler);
787 if (error)
788 pr_err("Failed to register input handler, error %d", error);
789 else
790 sysrq_handler_registered = true;
791 }
792
sysrq_unregister_handler(void)793 static inline void sysrq_unregister_handler(void)
794 {
795 if (sysrq_handler_registered) {
796 input_unregister_handler(&sysrq_handler);
797 sysrq_handler_registered = false;
798 }
799 }
800
801 #else
802
sysrq_register_handler(void)803 static inline void sysrq_register_handler(void)
804 {
805 }
806
sysrq_unregister_handler(void)807 static inline void sysrq_unregister_handler(void)
808 {
809 }
810
811 #endif /* CONFIG_INPUT */
812
sysrq_toggle_support(int enable_mask)813 int sysrq_toggle_support(int enable_mask)
814 {
815 bool was_enabled = sysrq_on();
816
817 sysrq_enabled = enable_mask;
818
819 if (was_enabled != sysrq_on()) {
820 if (sysrq_on())
821 sysrq_register_handler();
822 else
823 sysrq_unregister_handler();
824 }
825
826 return 0;
827 }
828
__sysrq_swap_key_ops(int key,struct sysrq_key_op * insert_op_p,struct sysrq_key_op * remove_op_p)829 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
830 struct sysrq_key_op *remove_op_p)
831 {
832 int retval;
833 unsigned long flags;
834
835 spin_lock_irqsave(&sysrq_key_table_lock, flags);
836 if (__sysrq_get_key_op(key) == remove_op_p) {
837 __sysrq_put_key_op(key, insert_op_p);
838 retval = 0;
839 } else {
840 retval = -1;
841 }
842 spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
843 return retval;
844 }
845
register_sysrq_key(int key,struct sysrq_key_op * op_p)846 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
847 {
848 return __sysrq_swap_key_ops(key, op_p, NULL);
849 }
850 EXPORT_SYMBOL(register_sysrq_key);
851
unregister_sysrq_key(int key,struct sysrq_key_op * op_p)852 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
853 {
854 return __sysrq_swap_key_ops(key, NULL, op_p);
855 }
856 EXPORT_SYMBOL(unregister_sysrq_key);
857
858 #ifdef CONFIG_PROC_FS
859 /*
860 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
861 */
write_sysrq_trigger(struct file * file,const char __user * buf,size_t count,loff_t * ppos)862 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
863 size_t count, loff_t *ppos)
864 {
865 if (count) {
866 char c;
867
868 if (get_user(c, buf))
869 return -EFAULT;
870 __handle_sysrq(c, false);
871 }
872
873 return count;
874 }
875
876 static const struct file_operations proc_sysrq_trigger_operations = {
877 .write = write_sysrq_trigger,
878 .llseek = noop_llseek,
879 };
880
sysrq_init_procfs(void)881 static void sysrq_init_procfs(void)
882 {
883 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
884 &proc_sysrq_trigger_operations))
885 pr_err("Failed to register proc interface\n");
886 }
887
888 #else
889
sysrq_init_procfs(void)890 static inline void sysrq_init_procfs(void)
891 {
892 }
893
894 #endif /* CONFIG_PROC_FS */
895
sysrq_init(void)896 static int __init sysrq_init(void)
897 {
898 sysrq_init_procfs();
899
900 if (sysrq_on())
901 sysrq_register_handler();
902
903 return 0;
904 }
905 module_init(sysrq_init);
906