mm, oom: force oom kill on sysrq+f
[linux-2.6.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/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/swap.h>
36 #include <linux/spinlock.h>
37 #include <linux/vt_kern.h>
38 #include <linux/workqueue.h>
39 #include <linux/hrtimer.h>
40 #include <linux/oom.h>
41 #include <linux/slab.h>
42 #include <linux/input.h>
43 #include <linux/uaccess.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
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  */
60 static bool sysrq_on_mask(int mask)
61 {
62         return sysrq_always_enabled ||
63                sysrq_enabled == 1 ||
64                (sysrq_enabled & mask);
65 }
66
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
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
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
111 static void sysrq_handle_unraw(int key)
112 {
113         vt_reset_unicode(fg_console);
114 }
115
116 static struct sysrq_key_op sysrq_unraw_op = {
117         .handler        = sysrq_handle_unraw,
118         .help_msg       = "unRaw",
119         .action_msg     = "Keyboard mode set to system default",
120         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
121 };
122 #else
123 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
124 #endif /* CONFIG_VT */
125
126 static void sysrq_handle_crash(int key)
127 {
128         char *killer = NULL;
129
130         panic_on_oops = 1;      /* force panic */
131         wmb();
132         *killer = 1;
133 }
134 static struct sysrq_key_op sysrq_crash_op = {
135         .handler        = sysrq_handle_crash,
136         .help_msg       = "Crash",
137         .action_msg     = "Trigger a crash",
138         .enable_mask    = SYSRQ_ENABLE_DUMP,
139 };
140
141 static void sysrq_handle_reboot(int key)
142 {
143         lockdep_off();
144         local_irq_enable();
145         emergency_restart();
146 }
147 static struct sysrq_key_op sysrq_reboot_op = {
148         .handler        = sysrq_handle_reboot,
149         .help_msg       = "reBoot",
150         .action_msg     = "Resetting",
151         .enable_mask    = SYSRQ_ENABLE_BOOT,
152 };
153
154 static void sysrq_handle_sync(int key)
155 {
156         emergency_sync();
157 }
158 static struct sysrq_key_op sysrq_sync_op = {
159         .handler        = sysrq_handle_sync,
160         .help_msg       = "Sync",
161         .action_msg     = "Emergency Sync",
162         .enable_mask    = SYSRQ_ENABLE_SYNC,
163 };
164
165 static void sysrq_handle_show_timers(int key)
166 {
167         sysrq_timer_list_show();
168 }
169
170 static struct sysrq_key_op sysrq_show_timers_op = {
171         .handler        = sysrq_handle_show_timers,
172         .help_msg       = "show-all-timers(Q)",
173         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
174 };
175
176 static void sysrq_handle_mountro(int key)
177 {
178         emergency_remount();
179 }
180 static struct sysrq_key_op sysrq_mountro_op = {
181         .handler        = sysrq_handle_mountro,
182         .help_msg       = "Unmount",
183         .action_msg     = "Emergency Remount R/O",
184         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
185 };
186
187 #ifdef CONFIG_LOCKDEP
188 static void sysrq_handle_showlocks(int key)
189 {
190         debug_show_all_locks();
191 }
192
193 static struct sysrq_key_op sysrq_showlocks_op = {
194         .handler        = sysrq_handle_showlocks,
195         .help_msg       = "show-all-locks(D)",
196         .action_msg     = "Show Locks Held",
197 };
198 #else
199 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
200 #endif
201
202 #ifdef CONFIG_SMP
203 static DEFINE_SPINLOCK(show_lock);
204
205 static void showacpu(void *dummy)
206 {
207         unsigned long flags;
208
209         /* Idle CPUs have no interesting backtrace. */
210         if (idle_cpu(smp_processor_id()))
211                 return;
212
213         spin_lock_irqsave(&show_lock, flags);
214         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
215         show_stack(NULL, NULL);
216         spin_unlock_irqrestore(&show_lock, flags);
217 }
218
219 static void sysrq_showregs_othercpus(struct work_struct *dummy)
220 {
221         smp_call_function(showacpu, NULL, 0);
222 }
223
224 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
225
226 static void sysrq_handle_showallcpus(int key)
227 {
228         /*
229          * Fall back to the workqueue based printing if the
230          * backtrace printing did not succeed or the
231          * architecture has no support for it:
232          */
233         if (!trigger_all_cpu_backtrace()) {
234                 struct pt_regs *regs = get_irq_regs();
235
236                 if (regs) {
237                         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
238                         show_regs(regs);
239                 }
240                 schedule_work(&sysrq_showallcpus);
241         }
242 }
243
244 static struct sysrq_key_op sysrq_showallcpus_op = {
245         .handler        = sysrq_handle_showallcpus,
246         .help_msg       = "show-backtrace-all-active-cpus(L)",
247         .action_msg     = "Show backtrace of all active CPUs",
248         .enable_mask    = SYSRQ_ENABLE_DUMP,
249 };
250 #endif
251
252 static void sysrq_handle_showregs(int key)
253 {
254         struct pt_regs *regs = get_irq_regs();
255         if (regs)
256                 show_regs(regs);
257         perf_event_print_debug();
258 }
259 static struct sysrq_key_op sysrq_showregs_op = {
260         .handler        = sysrq_handle_showregs,
261         .help_msg       = "show-registers(P)",
262         .action_msg     = "Show Regs",
263         .enable_mask    = SYSRQ_ENABLE_DUMP,
264 };
265
266 static void sysrq_handle_showstate(int key)
267 {
268         show_state();
269 }
270 static struct sysrq_key_op sysrq_showstate_op = {
271         .handler        = sysrq_handle_showstate,
272         .help_msg       = "show-task-states(T)",
273         .action_msg     = "Show State",
274         .enable_mask    = SYSRQ_ENABLE_DUMP,
275 };
276
277 static void sysrq_handle_showstate_blocked(int key)
278 {
279         show_state_filter(TASK_UNINTERRUPTIBLE);
280 }
281 static struct sysrq_key_op sysrq_showstate_blocked_op = {
282         .handler        = sysrq_handle_showstate_blocked,
283         .help_msg       = "show-blocked-tasks(W)",
284         .action_msg     = "Show Blocked State",
285         .enable_mask    = SYSRQ_ENABLE_DUMP,
286 };
287
288 #ifdef CONFIG_TRACING
289 #include <linux/ftrace.h>
290
291 static void sysrq_ftrace_dump(int key)
292 {
293         ftrace_dump(DUMP_ALL);
294 }
295 static struct sysrq_key_op sysrq_ftrace_dump_op = {
296         .handler        = sysrq_ftrace_dump,
297         .help_msg       = "dump-ftrace-buffer(Z)",
298         .action_msg     = "Dump ftrace buffer",
299         .enable_mask    = SYSRQ_ENABLE_DUMP,
300 };
301 #else
302 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
303 #endif
304
305 static void sysrq_handle_showmem(int key)
306 {
307         show_mem(0);
308 }
309 static struct sysrq_key_op sysrq_showmem_op = {
310         .handler        = sysrq_handle_showmem,
311         .help_msg       = "show-memory-usage(M)",
312         .action_msg     = "Show Memory",
313         .enable_mask    = SYSRQ_ENABLE_DUMP,
314 };
315
316 /*
317  * Signal sysrq helper function.  Sends a signal to all user processes.
318  */
319 static void send_sig_all(int sig)
320 {
321         struct task_struct *p;
322
323         read_lock(&tasklist_lock);
324         for_each_process(p) {
325                 if (p->flags & PF_KTHREAD)
326                         continue;
327                 if (is_global_init(p))
328                         continue;
329
330                 force_sig(sig, p);
331         }
332         read_unlock(&tasklist_lock);
333 }
334
335 static void sysrq_handle_term(int key)
336 {
337         send_sig_all(SIGTERM);
338         console_loglevel = 8;
339 }
340 static struct sysrq_key_op sysrq_term_op = {
341         .handler        = sysrq_handle_term,
342         .help_msg       = "terminate-all-tasks(E)",
343         .action_msg     = "Terminate All Tasks",
344         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
345 };
346
347 static void moom_callback(struct work_struct *ignored)
348 {
349         out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0, NULL, true);
350 }
351
352 static DECLARE_WORK(moom_work, moom_callback);
353
354 static void sysrq_handle_moom(int key)
355 {
356         schedule_work(&moom_work);
357 }
358 static struct sysrq_key_op sysrq_moom_op = {
359         .handler        = sysrq_handle_moom,
360         .help_msg       = "memory-full-oom-kill(F)",
361         .action_msg     = "Manual OOM execution",
362         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
363 };
364
365 #ifdef CONFIG_BLOCK
366 static void sysrq_handle_thaw(int key)
367 {
368         emergency_thaw_all();
369 }
370 static struct sysrq_key_op sysrq_thaw_op = {
371         .handler        = sysrq_handle_thaw,
372         .help_msg       = "thaw-filesystems(J)",
373         .action_msg     = "Emergency Thaw of all frozen filesystems",
374         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
375 };
376 #endif
377
378 static void sysrq_handle_kill(int key)
379 {
380         send_sig_all(SIGKILL);
381         console_loglevel = 8;
382 }
383 static struct sysrq_key_op sysrq_kill_op = {
384         .handler        = sysrq_handle_kill,
385         .help_msg       = "kill-all-tasks(I)",
386         .action_msg     = "Kill All Tasks",
387         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
388 };
389
390 static void sysrq_handle_unrt(int key)
391 {
392         normalize_rt_tasks();
393 }
394 static struct sysrq_key_op sysrq_unrt_op = {
395         .handler        = sysrq_handle_unrt,
396         .help_msg       = "nice-all-RT-tasks(N)",
397         .action_msg     = "Nice All RT Tasks",
398         .enable_mask    = SYSRQ_ENABLE_RTNICE,
399 };
400
401 /* Key Operations table and lock */
402 static DEFINE_SPINLOCK(sysrq_key_table_lock);
403
404 static struct sysrq_key_op *sysrq_key_table[36] = {
405         &sysrq_loglevel_op,             /* 0 */
406         &sysrq_loglevel_op,             /* 1 */
407         &sysrq_loglevel_op,             /* 2 */
408         &sysrq_loglevel_op,             /* 3 */
409         &sysrq_loglevel_op,             /* 4 */
410         &sysrq_loglevel_op,             /* 5 */
411         &sysrq_loglevel_op,             /* 6 */
412         &sysrq_loglevel_op,             /* 7 */
413         &sysrq_loglevel_op,             /* 8 */
414         &sysrq_loglevel_op,             /* 9 */
415
416         /*
417          * a: Don't use for system provided sysrqs, it is handled specially on
418          * sparc and will never arrive.
419          */
420         NULL,                           /* a */
421         &sysrq_reboot_op,               /* b */
422         &sysrq_crash_op,                /* c & ibm_emac driver debug */
423         &sysrq_showlocks_op,            /* d */
424         &sysrq_term_op,                 /* e */
425         &sysrq_moom_op,                 /* f */
426         /* g: May be registered for the kernel debugger */
427         NULL,                           /* g */
428         NULL,                           /* h - reserved for help */
429         &sysrq_kill_op,                 /* i */
430 #ifdef CONFIG_BLOCK
431         &sysrq_thaw_op,                 /* j */
432 #else
433         NULL,                           /* j */
434 #endif
435         &sysrq_SAK_op,                  /* k */
436 #ifdef CONFIG_SMP
437         &sysrq_showallcpus_op,          /* l */
438 #else
439         NULL,                           /* l */
440 #endif
441         &sysrq_showmem_op,              /* m */
442         &sysrq_unrt_op,                 /* n */
443         /* o: This will often be registered as 'Off' at init time */
444         NULL,                           /* o */
445         &sysrq_showregs_op,             /* p */
446         &sysrq_show_timers_op,          /* q */
447         &sysrq_unraw_op,                /* r */
448         &sysrq_sync_op,                 /* s */
449         &sysrq_showstate_op,            /* t */
450         &sysrq_mountro_op,              /* u */
451         /* v: May be registered for frame buffer console restore */
452         NULL,                           /* v */
453         &sysrq_showstate_blocked_op,    /* w */
454         /* x: May be registered on ppc/powerpc for xmon */
455         NULL,                           /* x */
456         /* y: May be registered on sparc64 for global register dump */
457         NULL,                           /* y */
458         &sysrq_ftrace_dump_op,          /* z */
459 };
460
461 /* key2index calculation, -1 on invalid index */
462 static int sysrq_key_table_key2index(int key)
463 {
464         int retval;
465
466         if ((key >= '0') && (key <= '9'))
467                 retval = key - '0';
468         else if ((key >= 'a') && (key <= 'z'))
469                 retval = key + 10 - 'a';
470         else
471                 retval = -1;
472         return retval;
473 }
474
475 /*
476  * get and put functions for the table, exposed to modules.
477  */
478 struct sysrq_key_op *__sysrq_get_key_op(int key)
479 {
480         struct sysrq_key_op *op_p = NULL;
481         int i;
482
483         i = sysrq_key_table_key2index(key);
484         if (i != -1)
485                 op_p = sysrq_key_table[i];
486
487         return op_p;
488 }
489
490 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
491 {
492         int i = sysrq_key_table_key2index(key);
493
494         if (i != -1)
495                 sysrq_key_table[i] = op_p;
496 }
497
498 void __handle_sysrq(int key, bool check_mask)
499 {
500         struct sysrq_key_op *op_p;
501         int orig_log_level;
502         int i;
503         unsigned long flags;
504
505         spin_lock_irqsave(&sysrq_key_table_lock, flags);
506         /*
507          * Raise the apparent loglevel to maximum so that the sysrq header
508          * is shown to provide the user with positive feedback.  We do not
509          * simply emit this at KERN_EMERG as that would change message
510          * routing in the consumers of /proc/kmsg.
511          */
512         orig_log_level = console_loglevel;
513         console_loglevel = 7;
514         printk(KERN_INFO "SysRq : ");
515
516         op_p = __sysrq_get_key_op(key);
517         if (op_p) {
518                 /*
519                  * Should we check for enabled operations (/proc/sysrq-trigger
520                  * should not) and is the invoked operation enabled?
521                  */
522                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
523                         printk("%s\n", op_p->action_msg);
524                         console_loglevel = orig_log_level;
525                         op_p->handler(key);
526                 } else {
527                         printk("This sysrq operation is disabled.\n");
528                 }
529         } else {
530                 printk("HELP : ");
531                 /* Only print the help msg once per handler */
532                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
533                         if (sysrq_key_table[i]) {
534                                 int j;
535
536                                 for (j = 0; sysrq_key_table[i] !=
537                                                 sysrq_key_table[j]; j++)
538                                         ;
539                                 if (j != i)
540                                         continue;
541                                 printk("%s ", sysrq_key_table[i]->help_msg);
542                         }
543                 }
544                 printk("\n");
545                 console_loglevel = orig_log_level;
546         }
547         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
548 }
549
550 void handle_sysrq(int key)
551 {
552         if (sysrq_on())
553                 __handle_sysrq(key, true);
554 }
555 EXPORT_SYMBOL(handle_sysrq);
556
557 #ifdef CONFIG_INPUT
558
559 /* Simple translation table for the SysRq keys */
560 static const unsigned char sysrq_xlate[KEY_CNT] =
561         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
562         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
563         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
564         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
565         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
566         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
567         "\r\000/";                                      /* 0x60 - 0x6f */
568
569 struct sysrq_state {
570         struct input_handle handle;
571         struct work_struct reinject_work;
572         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
573         unsigned int alt;
574         unsigned int alt_use;
575         bool active;
576         bool need_reinject;
577         bool reinjecting;
578 };
579
580 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
581 {
582         struct sysrq_state *sysrq =
583                         container_of(work, struct sysrq_state, reinject_work);
584         struct input_handle *handle = &sysrq->handle;
585         unsigned int alt_code = sysrq->alt_use;
586
587         if (sysrq->need_reinject) {
588                 /* we do not want the assignment to be reordered */
589                 sysrq->reinjecting = true;
590                 mb();
591
592                 /* Simulate press and release of Alt + SysRq */
593                 input_inject_event(handle, EV_KEY, alt_code, 1);
594                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
595                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
596
597                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
598                 input_inject_event(handle, EV_KEY, alt_code, 0);
599                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
600
601                 mb();
602                 sysrq->reinjecting = false;
603         }
604 }
605
606 static bool sysrq_filter(struct input_handle *handle,
607                          unsigned int type, unsigned int code, int value)
608 {
609         struct sysrq_state *sysrq = handle->private;
610         bool was_active = sysrq->active;
611         bool suppress;
612
613         /*
614          * Do not filter anything if we are in the process of re-injecting
615          * Alt+SysRq combination.
616          */
617         if (sysrq->reinjecting)
618                 return false;
619
620         switch (type) {
621
622         case EV_SYN:
623                 suppress = false;
624                 break;
625
626         case EV_KEY:
627                 switch (code) {
628
629                 case KEY_LEFTALT:
630                 case KEY_RIGHTALT:
631                         if (!value) {
632                                 /* One of ALTs is being released */
633                                 if (sysrq->active && code == sysrq->alt_use)
634                                         sysrq->active = false;
635
636                                 sysrq->alt = KEY_RESERVED;
637
638                         } else if (value != 2) {
639                                 sysrq->alt = code;
640                                 sysrq->need_reinject = false;
641                         }
642                         break;
643
644                 case KEY_SYSRQ:
645                         if (value == 1 && sysrq->alt != KEY_RESERVED) {
646                                 sysrq->active = true;
647                                 sysrq->alt_use = sysrq->alt;
648                                 /*
649                                  * If nothing else will be pressed we'll need
650                                  * to re-inject Alt-SysRq keysroke.
651                                  */
652                                 sysrq->need_reinject = true;
653                         }
654
655                         /*
656                          * Pretend that sysrq was never pressed at all. This
657                          * is needed to properly handle KGDB which will try
658                          * to release all keys after exiting debugger. If we
659                          * do not clear key bit it KGDB will end up sending
660                          * release events for Alt and SysRq, potentially
661                          * triggering print screen function.
662                          */
663                         if (sysrq->active)
664                                 clear_bit(KEY_SYSRQ, handle->dev->key);
665
666                         break;
667
668                 default:
669                         if (sysrq->active && value && value != 2) {
670                                 sysrq->need_reinject = false;
671                                 __handle_sysrq(sysrq_xlate[code], true);
672                         }
673                         break;
674                 }
675
676                 suppress = sysrq->active;
677
678                 if (!sysrq->active) {
679                         /*
680                          * If we are not suppressing key presses keep track of
681                          * keyboard state so we can release keys that have been
682                          * pressed before entering SysRq mode.
683                          */
684                         if (value)
685                                 set_bit(code, sysrq->key_down);
686                         else
687                                 clear_bit(code, sysrq->key_down);
688
689                         if (was_active)
690                                 schedule_work(&sysrq->reinject_work);
691
692                 } else if (value == 0 &&
693                            test_and_clear_bit(code, sysrq->key_down)) {
694                         /*
695                          * Pass on release events for keys that was pressed before
696                          * entering SysRq mode.
697                          */
698                         suppress = false;
699                 }
700                 break;
701
702         default:
703                 suppress = sysrq->active;
704                 break;
705         }
706
707         return suppress;
708 }
709
710 static int sysrq_connect(struct input_handler *handler,
711                          struct input_dev *dev,
712                          const struct input_device_id *id)
713 {
714         struct sysrq_state *sysrq;
715         int error;
716
717         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
718         if (!sysrq)
719                 return -ENOMEM;
720
721         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
722
723         sysrq->handle.dev = dev;
724         sysrq->handle.handler = handler;
725         sysrq->handle.name = "sysrq";
726         sysrq->handle.private = sysrq;
727
728         error = input_register_handle(&sysrq->handle);
729         if (error) {
730                 pr_err("Failed to register input sysrq handler, error %d\n",
731                         error);
732                 goto err_free;
733         }
734
735         error = input_open_device(&sysrq->handle);
736         if (error) {
737                 pr_err("Failed to open input device, error %d\n", error);
738                 goto err_unregister;
739         }
740
741         return 0;
742
743  err_unregister:
744         input_unregister_handle(&sysrq->handle);
745  err_free:
746         kfree(sysrq);
747         return error;
748 }
749
750 static void sysrq_disconnect(struct input_handle *handle)
751 {
752         struct sysrq_state *sysrq = handle->private;
753
754         input_close_device(handle);
755         cancel_work_sync(&sysrq->reinject_work);
756         input_unregister_handle(handle);
757         kfree(sysrq);
758 }
759
760 /*
761  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
762  * keyboards have SysRq key predefined and so user may add it to keymap
763  * later, but we expect all such keyboards to have left alt.
764  */
765 static const struct input_device_id sysrq_ids[] = {
766         {
767                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
768                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
769                 .evbit = { BIT_MASK(EV_KEY) },
770                 .keybit = { BIT_MASK(KEY_LEFTALT) },
771         },
772         { },
773 };
774
775 static struct input_handler sysrq_handler = {
776         .filter         = sysrq_filter,
777         .connect        = sysrq_connect,
778         .disconnect     = sysrq_disconnect,
779         .name           = "sysrq",
780         .id_table       = sysrq_ids,
781 };
782
783 static bool sysrq_handler_registered;
784
785 static inline void sysrq_register_handler(void)
786 {
787         int error;
788
789         error = input_register_handler(&sysrq_handler);
790         if (error)
791                 pr_err("Failed to register input handler, error %d", error);
792         else
793                 sysrq_handler_registered = true;
794 }
795
796 static inline void sysrq_unregister_handler(void)
797 {
798         if (sysrq_handler_registered) {
799                 input_unregister_handler(&sysrq_handler);
800                 sysrq_handler_registered = false;
801         }
802 }
803
804 #else
805
806 static inline void sysrq_register_handler(void)
807 {
808 }
809
810 static inline void sysrq_unregister_handler(void)
811 {
812 }
813
814 #endif /* CONFIG_INPUT */
815
816 int sysrq_toggle_support(int enable_mask)
817 {
818         bool was_enabled = sysrq_on();
819
820         sysrq_enabled = enable_mask;
821
822         if (was_enabled != sysrq_on()) {
823                 if (sysrq_on())
824                         sysrq_register_handler();
825                 else
826                         sysrq_unregister_handler();
827         }
828
829         return 0;
830 }
831
832 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
833                                 struct sysrq_key_op *remove_op_p)
834 {
835         int retval;
836         unsigned long flags;
837
838         spin_lock_irqsave(&sysrq_key_table_lock, flags);
839         if (__sysrq_get_key_op(key) == remove_op_p) {
840                 __sysrq_put_key_op(key, insert_op_p);
841                 retval = 0;
842         } else {
843                 retval = -1;
844         }
845         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
846         return retval;
847 }
848
849 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
850 {
851         return __sysrq_swap_key_ops(key, op_p, NULL);
852 }
853 EXPORT_SYMBOL(register_sysrq_key);
854
855 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
856 {
857         return __sysrq_swap_key_ops(key, NULL, op_p);
858 }
859 EXPORT_SYMBOL(unregister_sysrq_key);
860
861 #ifdef CONFIG_PROC_FS
862 /*
863  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
864  */
865 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
866                                    size_t count, loff_t *ppos)
867 {
868         if (count) {
869                 char c;
870
871                 if (get_user(c, buf))
872                         return -EFAULT;
873                 __handle_sysrq(c, false);
874         }
875
876         return count;
877 }
878
879 static const struct file_operations proc_sysrq_trigger_operations = {
880         .write          = write_sysrq_trigger,
881         .llseek         = noop_llseek,
882 };
883
884 static void sysrq_init_procfs(void)
885 {
886         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
887                          &proc_sysrq_trigger_operations))
888                 pr_err("Failed to register proc interface\n");
889 }
890
891 #else
892
893 static inline void sysrq_init_procfs(void)
894 {
895 }
896
897 #endif /* CONFIG_PROC_FS */
898
899 static int __init sysrq_init(void)
900 {
901         sysrq_init_procfs();
902
903         if (sysrq_on())
904                 sysrq_register_handler();
905
906         return 0;
907 }
908 module_init(sysrq_init);