Version:  2.0.40 2.2.26 2.4.37 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17

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

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