Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
[platform/adaptation/renesas_rcar/renesas_kernel.git] / drivers / tty / sysrq.c
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/sched/rt.h>
19 #include <linux/interrupt.h>
20 #include <linux/mm.h>
21 #include <linux/fs.h>
22 #include <linux/mount.h>
23 #include <linux/kdev_t.h>
24 #include <linux/major.h>
25 #include <linux/reboot.h>
26 #include <linux/sysrq.h>
27 #include <linux/kbd_kern.h>
28 #include <linux/proc_fs.h>
29 #include <linux/nmi.h>
30 #include <linux/quotaops.h>
31 #include <linux/perf_event.h>
32 #include <linux/kernel.h>
33 #include <linux/module.h>
34 #include <linux/suspend.h>
35 #include <linux/writeback.h>
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 #include <linux/uaccess.h>
45 #include <linux/moduleparam.h>
46 #include <linux/jiffies.h>
47 #include <linux/syscalls.h>
48
49 #include <asm/ptrace.h>
50 #include <asm/irq_regs.h>
51
52 /* Whether we react on sysrq keys or just ignore them */
53 static int __read_mostly sysrq_enabled = SYSRQ_DEFAULT_ENABLE;
54 static bool __read_mostly sysrq_always_enabled;
55
56 unsigned short platform_sysrq_reset_seq[] __weak = { KEY_RESERVED };
57 int sysrq_reset_downtime_ms __weak;
58
59 static bool sysrq_on(void)
60 {
61         return sysrq_enabled || sysrq_always_enabled;
62 }
63
64 /*
65  * A value of 1 means 'all', other nonzero values are an op mask:
66  */
67 static bool sysrq_on_mask(int mask)
68 {
69         return sysrq_always_enabled ||
70                sysrq_enabled == 1 ||
71                (sysrq_enabled & mask);
72 }
73
74 static int __init sysrq_always_enabled_setup(char *str)
75 {
76         sysrq_always_enabled = true;
77         pr_info("sysrq always enabled.\n");
78
79         return 1;
80 }
81
82 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
83
84
85 static void sysrq_handle_loglevel(int key)
86 {
87         int i;
88
89         i = key - '0';
90         console_loglevel = 7;
91         printk("Loglevel set to %d\n", i);
92         console_loglevel = i;
93 }
94 static struct sysrq_key_op sysrq_loglevel_op = {
95         .handler        = sysrq_handle_loglevel,
96         .help_msg       = "loglevel(0-9)",
97         .action_msg     = "Changing Loglevel",
98         .enable_mask    = SYSRQ_ENABLE_LOG,
99 };
100
101 #ifdef CONFIG_VT
102 static void sysrq_handle_SAK(int key)
103 {
104         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
105         schedule_work(SAK_work);
106 }
107 static struct sysrq_key_op sysrq_SAK_op = {
108         .handler        = sysrq_handle_SAK,
109         .help_msg       = "sak(k)",
110         .action_msg     = "SAK",
111         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
112 };
113 #else
114 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
115 #endif
116
117 #ifdef CONFIG_VT
118 static void sysrq_handle_unraw(int key)
119 {
120         vt_reset_unicode(fg_console);
121 }
122
123 static struct sysrq_key_op sysrq_unraw_op = {
124         .handler        = sysrq_handle_unraw,
125         .help_msg       = "unraw(r)",
126         .action_msg     = "Keyboard mode set to system default",
127         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
128 };
129 #else
130 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
131 #endif /* CONFIG_VT */
132
133 static void sysrq_handle_crash(int key)
134 {
135         char *killer = NULL;
136
137         panic_on_oops = 1;      /* force panic */
138         wmb();
139         *killer = 1;
140 }
141 static struct sysrq_key_op sysrq_crash_op = {
142         .handler        = sysrq_handle_crash,
143         .help_msg       = "crash(c)",
144         .action_msg     = "Trigger a crash",
145         .enable_mask    = SYSRQ_ENABLE_DUMP,
146 };
147
148 static void sysrq_handle_reboot(int key)
149 {
150         lockdep_off();
151         local_irq_enable();
152         emergency_restart();
153 }
154 static struct sysrq_key_op sysrq_reboot_op = {
155         .handler        = sysrq_handle_reboot,
156         .help_msg       = "reboot(b)",
157         .action_msg     = "Resetting",
158         .enable_mask    = SYSRQ_ENABLE_BOOT,
159 };
160
161 static void sysrq_handle_sync(int key)
162 {
163         emergency_sync();
164 }
165 static struct sysrq_key_op sysrq_sync_op = {
166         .handler        = sysrq_handle_sync,
167         .help_msg       = "sync(s)",
168         .action_msg     = "Emergency Sync",
169         .enable_mask    = SYSRQ_ENABLE_SYNC,
170 };
171
172 static void sysrq_handle_show_timers(int key)
173 {
174         sysrq_timer_list_show();
175 }
176
177 static struct sysrq_key_op sysrq_show_timers_op = {
178         .handler        = sysrq_handle_show_timers,
179         .help_msg       = "show-all-timers(q)",
180         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
181 };
182
183 static void sysrq_handle_mountro(int key)
184 {
185         emergency_remount();
186 }
187 static struct sysrq_key_op sysrq_mountro_op = {
188         .handler        = sysrq_handle_mountro,
189         .help_msg       = "unmount(u)",
190         .action_msg     = "Emergency Remount R/O",
191         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
192 };
193
194 #ifdef CONFIG_LOCKDEP
195 static void sysrq_handle_showlocks(int key)
196 {
197         debug_show_all_locks();
198 }
199
200 static struct sysrq_key_op sysrq_showlocks_op = {
201         .handler        = sysrq_handle_showlocks,
202         .help_msg       = "show-all-locks(d)",
203         .action_msg     = "Show Locks Held",
204 };
205 #else
206 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
207 #endif
208
209 #ifdef CONFIG_SMP
210 static DEFINE_SPINLOCK(show_lock);
211
212 static void showacpu(void *dummy)
213 {
214         unsigned long flags;
215
216         /* Idle CPUs have no interesting backtrace. */
217         if (idle_cpu(smp_processor_id()))
218                 return;
219
220         spin_lock_irqsave(&show_lock, flags);
221         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
222         show_stack(NULL, NULL);
223         spin_unlock_irqrestore(&show_lock, flags);
224 }
225
226 static void sysrq_showregs_othercpus(struct work_struct *dummy)
227 {
228         smp_call_function(showacpu, NULL, 0);
229 }
230
231 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
232
233 static void sysrq_handle_showallcpus(int key)
234 {
235         /*
236          * Fall back to the workqueue based printing if the
237          * backtrace printing did not succeed or the
238          * architecture has no support for it:
239          */
240         if (!trigger_all_cpu_backtrace()) {
241                 struct pt_regs *regs = get_irq_regs();
242
243                 if (regs) {
244                         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
245                         show_regs(regs);
246                 }
247                 schedule_work(&sysrq_showallcpus);
248         }
249 }
250
251 static struct sysrq_key_op sysrq_showallcpus_op = {
252         .handler        = sysrq_handle_showallcpus,
253         .help_msg       = "show-backtrace-all-active-cpus(l)",
254         .action_msg     = "Show backtrace of all active CPUs",
255         .enable_mask    = SYSRQ_ENABLE_DUMP,
256 };
257 #endif
258
259 static void sysrq_handle_showregs(int key)
260 {
261         struct pt_regs *regs = get_irq_regs();
262         if (regs)
263                 show_regs(regs);
264         perf_event_print_debug();
265 }
266 static struct sysrq_key_op sysrq_showregs_op = {
267         .handler        = sysrq_handle_showregs,
268         .help_msg       = "show-registers(p)",
269         .action_msg     = "Show Regs",
270         .enable_mask    = SYSRQ_ENABLE_DUMP,
271 };
272
273 static void sysrq_handle_showstate(int key)
274 {
275         show_state();
276 }
277 static struct sysrq_key_op sysrq_showstate_op = {
278         .handler        = sysrq_handle_showstate,
279         .help_msg       = "show-task-states(t)",
280         .action_msg     = "Show State",
281         .enable_mask    = SYSRQ_ENABLE_DUMP,
282 };
283
284 static void sysrq_handle_showstate_blocked(int key)
285 {
286         show_state_filter(TASK_UNINTERRUPTIBLE);
287 }
288 static struct sysrq_key_op sysrq_showstate_blocked_op = {
289         .handler        = sysrq_handle_showstate_blocked,
290         .help_msg       = "show-blocked-tasks(w)",
291         .action_msg     = "Show Blocked State",
292         .enable_mask    = SYSRQ_ENABLE_DUMP,
293 };
294
295 #ifdef CONFIG_TRACING
296 #include <linux/ftrace.h>
297
298 static void sysrq_ftrace_dump(int key)
299 {
300         ftrace_dump(DUMP_ALL);
301 }
302 static struct sysrq_key_op sysrq_ftrace_dump_op = {
303         .handler        = sysrq_ftrace_dump,
304         .help_msg       = "dump-ftrace-buffer(z)",
305         .action_msg     = "Dump ftrace buffer",
306         .enable_mask    = SYSRQ_ENABLE_DUMP,
307 };
308 #else
309 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
310 #endif
311
312 static void sysrq_handle_showmem(int key)
313 {
314         show_mem(0);
315 }
316 static struct sysrq_key_op sysrq_showmem_op = {
317         .handler        = sysrq_handle_showmem,
318         .help_msg       = "show-memory-usage(m)",
319         .action_msg     = "Show Memory",
320         .enable_mask    = SYSRQ_ENABLE_DUMP,
321 };
322
323 /*
324  * Signal sysrq helper function.  Sends a signal to all user processes.
325  */
326 static void send_sig_all(int sig)
327 {
328         struct task_struct *p;
329
330         read_lock(&tasklist_lock);
331         for_each_process(p) {
332                 if (p->flags & PF_KTHREAD)
333                         continue;
334                 if (is_global_init(p))
335                         continue;
336
337                 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
338         }
339         read_unlock(&tasklist_lock);
340 }
341
342 static void sysrq_handle_term(int key)
343 {
344         send_sig_all(SIGTERM);
345         console_loglevel = 8;
346 }
347 static struct sysrq_key_op sysrq_term_op = {
348         .handler        = sysrq_handle_term,
349         .help_msg       = "terminate-all-tasks(e)",
350         .action_msg     = "Terminate All Tasks",
351         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
352 };
353
354 static void moom_callback(struct work_struct *ignored)
355 {
356         out_of_memory(node_zonelist(first_online_node, GFP_KERNEL), GFP_KERNEL,
357                       0, NULL, true);
358 }
359
360 static DECLARE_WORK(moom_work, moom_callback);
361
362 static void sysrq_handle_moom(int key)
363 {
364         schedule_work(&moom_work);
365 }
366 static struct sysrq_key_op sysrq_moom_op = {
367         .handler        = sysrq_handle_moom,
368         .help_msg       = "memory-full-oom-kill(f)",
369         .action_msg     = "Manual OOM execution",
370         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
371 };
372
373 #ifdef CONFIG_BLOCK
374 static void sysrq_handle_thaw(int key)
375 {
376         emergency_thaw_all();
377 }
378 static struct sysrq_key_op sysrq_thaw_op = {
379         .handler        = sysrq_handle_thaw,
380         .help_msg       = "thaw-filesystems(j)",
381         .action_msg     = "Emergency Thaw of all frozen filesystems",
382         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
383 };
384 #endif
385
386 static void sysrq_handle_kill(int key)
387 {
388         send_sig_all(SIGKILL);
389         console_loglevel = 8;
390 }
391 static struct sysrq_key_op sysrq_kill_op = {
392         .handler        = sysrq_handle_kill,
393         .help_msg       = "kill-all-tasks(i)",
394         .action_msg     = "Kill All Tasks",
395         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
396 };
397
398 static void sysrq_handle_unrt(int key)
399 {
400         normalize_rt_tasks();
401 }
402 static struct sysrq_key_op sysrq_unrt_op = {
403         .handler        = sysrq_handle_unrt,
404         .help_msg       = "nice-all-RT-tasks(n)",
405         .action_msg     = "Nice All RT Tasks",
406         .enable_mask    = SYSRQ_ENABLE_RTNICE,
407 };
408
409 /* Key Operations table and lock */
410 static DEFINE_SPINLOCK(sysrq_key_table_lock);
411
412 static struct sysrq_key_op *sysrq_key_table[36] = {
413         &sysrq_loglevel_op,             /* 0 */
414         &sysrq_loglevel_op,             /* 1 */
415         &sysrq_loglevel_op,             /* 2 */
416         &sysrq_loglevel_op,             /* 3 */
417         &sysrq_loglevel_op,             /* 4 */
418         &sysrq_loglevel_op,             /* 5 */
419         &sysrq_loglevel_op,             /* 6 */
420         &sysrq_loglevel_op,             /* 7 */
421         &sysrq_loglevel_op,             /* 8 */
422         &sysrq_loglevel_op,             /* 9 */
423
424         /*
425          * a: Don't use for system provided sysrqs, it is handled specially on
426          * sparc and will never arrive.
427          */
428         NULL,                           /* a */
429         &sysrq_reboot_op,               /* b */
430         &sysrq_crash_op,                /* c & ibm_emac driver debug */
431         &sysrq_showlocks_op,            /* d */
432         &sysrq_term_op,                 /* e */
433         &sysrq_moom_op,                 /* f */
434         /* g: May be registered for the kernel debugger */
435         NULL,                           /* g */
436         NULL,                           /* h - reserved for help */
437         &sysrq_kill_op,                 /* i */
438 #ifdef CONFIG_BLOCK
439         &sysrq_thaw_op,                 /* j */
440 #else
441         NULL,                           /* j */
442 #endif
443         &sysrq_SAK_op,                  /* k */
444 #ifdef CONFIG_SMP
445         &sysrq_showallcpus_op,          /* l */
446 #else
447         NULL,                           /* l */
448 #endif
449         &sysrq_showmem_op,              /* m */
450         &sysrq_unrt_op,                 /* n */
451         /* o: This will often be registered as 'Off' at init time */
452         NULL,                           /* o */
453         &sysrq_showregs_op,             /* p */
454         &sysrq_show_timers_op,          /* q */
455         &sysrq_unraw_op,                /* r */
456         &sysrq_sync_op,                 /* s */
457         &sysrq_showstate_op,            /* t */
458         &sysrq_mountro_op,              /* u */
459         /* v: May be registered for frame buffer console restore */
460         NULL,                           /* v */
461         &sysrq_showstate_blocked_op,    /* w */
462         /* x: May be registered on ppc/powerpc for xmon */
463         /* x: May be registered on sparc64 for global PMU dump */
464         NULL,                           /* x */
465         /* y: May be registered on sparc64 for global register dump */
466         NULL,                           /* y */
467         &sysrq_ftrace_dump_op,          /* z */
468 };
469
470 /* key2index calculation, -1 on invalid index */
471 static int sysrq_key_table_key2index(int key)
472 {
473         int retval;
474
475         if ((key >= '0') && (key <= '9'))
476                 retval = key - '0';
477         else if ((key >= 'a') && (key <= 'z'))
478                 retval = key + 10 - 'a';
479         else
480                 retval = -1;
481         return retval;
482 }
483
484 /*
485  * get and put functions for the table, exposed to modules.
486  */
487 struct sysrq_key_op *__sysrq_get_key_op(int key)
488 {
489         struct sysrq_key_op *op_p = NULL;
490         int i;
491
492         i = sysrq_key_table_key2index(key);
493         if (i != -1)
494                 op_p = sysrq_key_table[i];
495
496         return op_p;
497 }
498
499 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
500 {
501         int i = sysrq_key_table_key2index(key);
502
503         if (i != -1)
504                 sysrq_key_table[i] = op_p;
505 }
506
507 void __handle_sysrq(int key, bool check_mask)
508 {
509         struct sysrq_key_op *op_p;
510         int orig_log_level;
511         int i;
512         unsigned long flags;
513
514         spin_lock_irqsave(&sysrq_key_table_lock, flags);
515         /*
516          * Raise the apparent loglevel to maximum so that the sysrq header
517          * is shown to provide the user with positive feedback.  We do not
518          * simply emit this at KERN_EMERG as that would change message
519          * routing in the consumers of /proc/kmsg.
520          */
521         orig_log_level = console_loglevel;
522         console_loglevel = 7;
523         printk(KERN_INFO "SysRq : ");
524
525         op_p = __sysrq_get_key_op(key);
526         if (op_p) {
527                 /*
528                  * Should we check for enabled operations (/proc/sysrq-trigger
529                  * should not) and is the invoked operation enabled?
530                  */
531                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
532                         printk("%s\n", op_p->action_msg);
533                         console_loglevel = orig_log_level;
534                         op_p->handler(key);
535                 } else {
536                         printk("This sysrq operation is disabled.\n");
537                 }
538         } else {
539                 printk("HELP : ");
540                 /* Only print the help msg once per handler */
541                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
542                         if (sysrq_key_table[i]) {
543                                 int j;
544
545                                 for (j = 0; sysrq_key_table[i] !=
546                                                 sysrq_key_table[j]; j++)
547                                         ;
548                                 if (j != i)
549                                         continue;
550                                 printk("%s ", sysrq_key_table[i]->help_msg);
551                         }
552                 }
553                 printk("\n");
554                 console_loglevel = orig_log_level;
555         }
556         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
557 }
558
559 void handle_sysrq(int key)
560 {
561         if (sysrq_on())
562                 __handle_sysrq(key, true);
563 }
564 EXPORT_SYMBOL(handle_sysrq);
565
566 #ifdef CONFIG_INPUT
567
568 /* Simple translation table for the SysRq keys */
569 static const unsigned char sysrq_xlate[KEY_CNT] =
570         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
571         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
572         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
573         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
574         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
575         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
576         "\r\000/";                                      /* 0x60 - 0x6f */
577
578 struct sysrq_state {
579         struct input_handle handle;
580         struct work_struct reinject_work;
581         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
582         unsigned int alt;
583         unsigned int alt_use;
584         bool active;
585         bool need_reinject;
586         bool reinjecting;
587
588         /* reset sequence handling */
589         bool reset_canceled;
590         bool reset_requested;
591         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
592         int reset_seq_len;
593         int reset_seq_cnt;
594         int reset_seq_version;
595         struct timer_list keyreset_timer;
596 };
597
598 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
599 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
600 static unsigned int sysrq_reset_seq_len;
601 static unsigned int sysrq_reset_seq_version = 1;
602
603 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
604 {
605         int i;
606         unsigned short key;
607
608         state->reset_seq_cnt = 0;
609
610         for (i = 0; i < sysrq_reset_seq_len; i++) {
611                 key = sysrq_reset_seq[i];
612
613                 if (key == KEY_RESERVED || key > KEY_MAX)
614                         break;
615
616                 __set_bit(key, state->reset_keybit);
617                 state->reset_seq_len++;
618
619                 if (test_bit(key, state->key_down))
620                         state->reset_seq_cnt++;
621         }
622
623         /* Disable reset until old keys are not released */
624         state->reset_canceled = state->reset_seq_cnt != 0;
625
626         state->reset_seq_version = sysrq_reset_seq_version;
627 }
628
629 static void sysrq_do_reset(unsigned long _state)
630 {
631         struct sysrq_state *state = (struct sysrq_state *) _state;
632
633         state->reset_requested = true;
634
635         sys_sync();
636         kernel_restart(NULL);
637 }
638
639 static void sysrq_handle_reset_request(struct sysrq_state *state)
640 {
641         if (state->reset_requested)
642                 __handle_sysrq(sysrq_xlate[KEY_B], false);
643
644         if (sysrq_reset_downtime_ms)
645                 mod_timer(&state->keyreset_timer,
646                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
647         else
648                 sysrq_do_reset((unsigned long)state);
649 }
650
651 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
652                                         unsigned int code, int value)
653 {
654         if (!test_bit(code, state->reset_keybit)) {
655                 /*
656                  * Pressing any key _not_ in reset sequence cancels
657                  * the reset sequence.  Also cancelling the timer in
658                  * case additional keys were pressed after a reset
659                  * has been requested.
660                  */
661                 if (value && state->reset_seq_cnt) {
662                         state->reset_canceled = true;
663                         del_timer(&state->keyreset_timer);
664                 }
665         } else if (value == 0) {
666                 /*
667                  * Key release - all keys in the reset sequence need
668                  * to be pressed and held for the reset timeout
669                  * to hold.
670                  */
671                 del_timer(&state->keyreset_timer);
672
673                 if (--state->reset_seq_cnt == 0)
674                         state->reset_canceled = false;
675         } else if (value == 1) {
676                 /* key press, not autorepeat */
677                 if (++state->reset_seq_cnt == state->reset_seq_len &&
678                     !state->reset_canceled) {
679                         sysrq_handle_reset_request(state);
680                 }
681         }
682 }
683
684 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
685 {
686         struct sysrq_state *sysrq =
687                         container_of(work, struct sysrq_state, reinject_work);
688         struct input_handle *handle = &sysrq->handle;
689         unsigned int alt_code = sysrq->alt_use;
690
691         if (sysrq->need_reinject) {
692                 /* we do not want the assignment to be reordered */
693                 sysrq->reinjecting = true;
694                 mb();
695
696                 /* Simulate press and release of Alt + SysRq */
697                 input_inject_event(handle, EV_KEY, alt_code, 1);
698                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
699                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
700
701                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
702                 input_inject_event(handle, EV_KEY, alt_code, 0);
703                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
704
705                 mb();
706                 sysrq->reinjecting = false;
707         }
708 }
709
710 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
711                                   unsigned int code, int value)
712 {
713         bool was_active = sysrq->active;
714         bool suppress;
715
716         switch (code) {
717
718         case KEY_LEFTALT:
719         case KEY_RIGHTALT:
720                 if (!value) {
721                         /* One of ALTs is being released */
722                         if (sysrq->active && code == sysrq->alt_use)
723                                 sysrq->active = false;
724
725                         sysrq->alt = KEY_RESERVED;
726
727                 } else if (value != 2) {
728                         sysrq->alt = code;
729                         sysrq->need_reinject = false;
730                 }
731                 break;
732
733         case KEY_SYSRQ:
734                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
735                         sysrq->active = true;
736                         sysrq->alt_use = sysrq->alt;
737                         /*
738                          * If nothing else will be pressed we'll need
739                          * to re-inject Alt-SysRq keysroke.
740                          */
741                         sysrq->need_reinject = true;
742                 }
743
744                 /*
745                  * Pretend that sysrq was never pressed at all. This
746                  * is needed to properly handle KGDB which will try
747                  * to release all keys after exiting debugger. If we
748                  * do not clear key bit it KGDB will end up sending
749                  * release events for Alt and SysRq, potentially
750                  * triggering print screen function.
751                  */
752                 if (sysrq->active)
753                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
754
755                 break;
756
757         default:
758                 if (sysrq->active && value && value != 2) {
759                         sysrq->need_reinject = false;
760                         __handle_sysrq(sysrq_xlate[code], true);
761                 }
762                 break;
763         }
764
765         suppress = sysrq->active;
766
767         if (!sysrq->active) {
768
769                 /*
770                  * See if reset sequence has changed since the last time.
771                  */
772                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
773                         sysrq_parse_reset_sequence(sysrq);
774
775                 /*
776                  * If we are not suppressing key presses keep track of
777                  * keyboard state so we can release keys that have been
778                  * pressed before entering SysRq mode.
779                  */
780                 if (value)
781                         set_bit(code, sysrq->key_down);
782                 else
783                         clear_bit(code, sysrq->key_down);
784
785                 if (was_active)
786                         schedule_work(&sysrq->reinject_work);
787
788                 /* Check for reset sequence */
789                 sysrq_detect_reset_sequence(sysrq, code, value);
790
791         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
792                 /*
793                  * Pass on release events for keys that was pressed before
794                  * entering SysRq mode.
795                  */
796                 suppress = false;
797         }
798
799         return suppress;
800 }
801
802 static bool sysrq_filter(struct input_handle *handle,
803                          unsigned int type, unsigned int code, int value)
804 {
805         struct sysrq_state *sysrq = handle->private;
806         bool suppress;
807
808         /*
809          * Do not filter anything if we are in the process of re-injecting
810          * Alt+SysRq combination.
811          */
812         if (sysrq->reinjecting)
813                 return false;
814
815         switch (type) {
816
817         case EV_SYN:
818                 suppress = false;
819                 break;
820
821         case EV_KEY:
822                 suppress = sysrq_handle_keypress(sysrq, code, value);
823                 break;
824
825         default:
826                 suppress = sysrq->active;
827                 break;
828         }
829
830         return suppress;
831 }
832
833 static int sysrq_connect(struct input_handler *handler,
834                          struct input_dev *dev,
835                          const struct input_device_id *id)
836 {
837         struct sysrq_state *sysrq;
838         int error;
839
840         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
841         if (!sysrq)
842                 return -ENOMEM;
843
844         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
845
846         sysrq->handle.dev = dev;
847         sysrq->handle.handler = handler;
848         sysrq->handle.name = "sysrq";
849         sysrq->handle.private = sysrq;
850         setup_timer(&sysrq->keyreset_timer,
851                     sysrq_do_reset, (unsigned long)sysrq);
852
853         error = input_register_handle(&sysrq->handle);
854         if (error) {
855                 pr_err("Failed to register input sysrq handler, error %d\n",
856                         error);
857                 goto err_free;
858         }
859
860         error = input_open_device(&sysrq->handle);
861         if (error) {
862                 pr_err("Failed to open input device, error %d\n", error);
863                 goto err_unregister;
864         }
865
866         return 0;
867
868  err_unregister:
869         input_unregister_handle(&sysrq->handle);
870  err_free:
871         kfree(sysrq);
872         return error;
873 }
874
875 static void sysrq_disconnect(struct input_handle *handle)
876 {
877         struct sysrq_state *sysrq = handle->private;
878
879         input_close_device(handle);
880         cancel_work_sync(&sysrq->reinject_work);
881         del_timer_sync(&sysrq->keyreset_timer);
882         input_unregister_handle(handle);
883         kfree(sysrq);
884 }
885
886 /*
887  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
888  * keyboards have SysRq key predefined and so user may add it to keymap
889  * later, but we expect all such keyboards to have left alt.
890  */
891 static const struct input_device_id sysrq_ids[] = {
892         {
893                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
894                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
895                 .evbit = { BIT_MASK(EV_KEY) },
896                 .keybit = { BIT_MASK(KEY_LEFTALT) },
897         },
898         { },
899 };
900
901 static struct input_handler sysrq_handler = {
902         .filter         = sysrq_filter,
903         .connect        = sysrq_connect,
904         .disconnect     = sysrq_disconnect,
905         .name           = "sysrq",
906         .id_table       = sysrq_ids,
907 };
908
909 static bool sysrq_handler_registered;
910
911 static inline void sysrq_register_handler(void)
912 {
913         unsigned short key;
914         int error;
915         int i;
916
917         for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
918                 key = platform_sysrq_reset_seq[i];
919                 if (key == KEY_RESERVED || key > KEY_MAX)
920                         break;
921
922                 sysrq_reset_seq[sysrq_reset_seq_len++] = key;
923         }
924
925         error = input_register_handler(&sysrq_handler);
926         if (error)
927                 pr_err("Failed to register input handler, error %d", error);
928         else
929                 sysrq_handler_registered = true;
930 }
931
932 static inline void sysrq_unregister_handler(void)
933 {
934         if (sysrq_handler_registered) {
935                 input_unregister_handler(&sysrq_handler);
936                 sysrq_handler_registered = false;
937         }
938 }
939
940 static int sysrq_reset_seq_param_set(const char *buffer,
941                                      const struct kernel_param *kp)
942 {
943         unsigned long val;
944         int error;
945
946         error = kstrtoul(buffer, 0, &val);
947         if (error < 0)
948                 return error;
949
950         if (val > KEY_MAX)
951                 return -EINVAL;
952
953         *((unsigned short *)kp->arg) = val;
954         sysrq_reset_seq_version++;
955
956         return 0;
957 }
958
959 static struct kernel_param_ops param_ops_sysrq_reset_seq = {
960         .get    = param_get_ushort,
961         .set    = sysrq_reset_seq_param_set,
962 };
963
964 #define param_check_sysrq_reset_seq(name, p)    \
965         __param_check(name, p, unsigned short)
966
967 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
968                          &sysrq_reset_seq_len, 0644);
969
970 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
971
972 #else
973
974 static inline void sysrq_register_handler(void)
975 {
976 }
977
978 static inline void sysrq_unregister_handler(void)
979 {
980 }
981
982 #endif /* CONFIG_INPUT */
983
984 int sysrq_toggle_support(int enable_mask)
985 {
986         bool was_enabled = sysrq_on();
987
988         sysrq_enabled = enable_mask;
989
990         if (was_enabled != sysrq_on()) {
991                 if (sysrq_on())
992                         sysrq_register_handler();
993                 else
994                         sysrq_unregister_handler();
995         }
996
997         return 0;
998 }
999
1000 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1001                                 struct sysrq_key_op *remove_op_p)
1002 {
1003         int retval;
1004         unsigned long flags;
1005
1006         spin_lock_irqsave(&sysrq_key_table_lock, flags);
1007         if (__sysrq_get_key_op(key) == remove_op_p) {
1008                 __sysrq_put_key_op(key, insert_op_p);
1009                 retval = 0;
1010         } else {
1011                 retval = -1;
1012         }
1013         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
1014         return retval;
1015 }
1016
1017 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1018 {
1019         return __sysrq_swap_key_ops(key, op_p, NULL);
1020 }
1021 EXPORT_SYMBOL(register_sysrq_key);
1022
1023 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1024 {
1025         return __sysrq_swap_key_ops(key, NULL, op_p);
1026 }
1027 EXPORT_SYMBOL(unregister_sysrq_key);
1028
1029 #ifdef CONFIG_PROC_FS
1030 /*
1031  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1032  */
1033 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1034                                    size_t count, loff_t *ppos)
1035 {
1036         if (count) {
1037                 char c;
1038
1039                 if (get_user(c, buf))
1040                         return -EFAULT;
1041                 __handle_sysrq(c, false);
1042         }
1043
1044         return count;
1045 }
1046
1047 static const struct file_operations proc_sysrq_trigger_operations = {
1048         .write          = write_sysrq_trigger,
1049         .llseek         = noop_llseek,
1050 };
1051
1052 static void sysrq_init_procfs(void)
1053 {
1054         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1055                          &proc_sysrq_trigger_operations))
1056                 pr_err("Failed to register proc interface\n");
1057 }
1058
1059 #else
1060
1061 static inline void sysrq_init_procfs(void)
1062 {
1063 }
1064
1065 #endif /* CONFIG_PROC_FS */
1066
1067 static int __init sysrq_init(void)
1068 {
1069         sysrq_init_procfs();
1070
1071         if (sysrq_on())
1072                 sysrq_register_handler();
1073
1074         return 0;
1075 }
1076 module_init(sysrq_init);