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

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