Version:  2.0.40 2.2.26 2.4.37 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 3.18 3.19 4.0

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         pr_info("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         pr_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                         pr_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         if (!out_of_memory(node_zonelist(first_memory_node, GFP_KERNEL),
359                            GFP_KERNEL, 0, NULL, true))
360                 pr_info("OOM request ignored because killer is disabled\n");
361 }
362 
363 static DECLARE_WORK(moom_work, moom_callback);
364 
365 static void sysrq_handle_moom(int key)
366 {
367         schedule_work(&moom_work);
368 }
369 static struct sysrq_key_op sysrq_moom_op = {
370         .handler        = sysrq_handle_moom,
371         .help_msg       = "memory-full-oom-kill(f)",
372         .action_msg     = "Manual OOM execution",
373         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
374 };
375 
376 #ifdef CONFIG_BLOCK
377 static void sysrq_handle_thaw(int key)
378 {
379         emergency_thaw_all();
380 }
381 static struct sysrq_key_op sysrq_thaw_op = {
382         .handler        = sysrq_handle_thaw,
383         .help_msg       = "thaw-filesystems(j)",
384         .action_msg     = "Emergency Thaw of all frozen filesystems",
385         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
386 };
387 #endif
388 
389 static void sysrq_handle_kill(int key)
390 {
391         send_sig_all(SIGKILL);
392         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
393 }
394 static struct sysrq_key_op sysrq_kill_op = {
395         .handler        = sysrq_handle_kill,
396         .help_msg       = "kill-all-tasks(i)",
397         .action_msg     = "Kill All Tasks",
398         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
399 };
400 
401 static void sysrq_handle_unrt(int key)
402 {
403         normalize_rt_tasks();
404 }
405 static struct sysrq_key_op sysrq_unrt_op = {
406         .handler        = sysrq_handle_unrt,
407         .help_msg       = "nice-all-RT-tasks(n)",
408         .action_msg     = "Nice All RT Tasks",
409         .enable_mask    = SYSRQ_ENABLE_RTNICE,
410 };
411 
412 /* Key Operations table and lock */
413 static DEFINE_SPINLOCK(sysrq_key_table_lock);
414 
415 static struct sysrq_key_op *sysrq_key_table[36] = {
416         &sysrq_loglevel_op,             /* 0 */
417         &sysrq_loglevel_op,             /* 1 */
418         &sysrq_loglevel_op,             /* 2 */
419         &sysrq_loglevel_op,             /* 3 */
420         &sysrq_loglevel_op,             /* 4 */
421         &sysrq_loglevel_op,             /* 5 */
422         &sysrq_loglevel_op,             /* 6 */
423         &sysrq_loglevel_op,             /* 7 */
424         &sysrq_loglevel_op,             /* 8 */
425         &sysrq_loglevel_op,             /* 9 */
426 
427         /*
428          * a: Don't use for system provided sysrqs, it is handled specially on
429          * sparc and will never arrive.
430          */
431         NULL,                           /* a */
432         &sysrq_reboot_op,               /* b */
433         &sysrq_crash_op,                /* c & ibm_emac driver debug */
434         &sysrq_showlocks_op,            /* d */
435         &sysrq_term_op,                 /* e */
436         &sysrq_moom_op,                 /* f */
437         /* g: May be registered for the kernel debugger */
438         NULL,                           /* g */
439         NULL,                           /* h - reserved for help */
440         &sysrq_kill_op,                 /* i */
441 #ifdef CONFIG_BLOCK
442         &sysrq_thaw_op,                 /* j */
443 #else
444         NULL,                           /* j */
445 #endif
446         &sysrq_SAK_op,                  /* k */
447 #ifdef CONFIG_SMP
448         &sysrq_showallcpus_op,          /* l */
449 #else
450         NULL,                           /* l */
451 #endif
452         &sysrq_showmem_op,              /* m */
453         &sysrq_unrt_op,                 /* n */
454         /* o: This will often be registered as 'Off' at init time */
455         NULL,                           /* o */
456         &sysrq_showregs_op,             /* p */
457         &sysrq_show_timers_op,          /* q */
458         &sysrq_unraw_op,                /* r */
459         &sysrq_sync_op,                 /* s */
460         &sysrq_showstate_op,            /* t */
461         &sysrq_mountro_op,              /* u */
462         /* v: May be registered for frame buffer console restore */
463         NULL,                           /* v */
464         &sysrq_showstate_blocked_op,    /* w */
465         /* x: May be registered on ppc/powerpc for xmon */
466         /* x: May be registered on sparc64 for global PMU dump */
467         NULL,                           /* x */
468         /* y: May be registered on sparc64 for global register dump */
469         NULL,                           /* y */
470         &sysrq_ftrace_dump_op,          /* z */
471 };
472 
473 /* key2index calculation, -1 on invalid index */
474 static int sysrq_key_table_key2index(int key)
475 {
476         int retval;
477 
478         if ((key >= '') && (key <= '9'))
479                 retval = key - '';
480         else if ((key >= 'a') && (key <= 'z'))
481                 retval = key + 10 - 'a';
482         else
483                 retval = -1;
484         return retval;
485 }
486 
487 /*
488  * get and put functions for the table, exposed to modules.
489  */
490 struct sysrq_key_op *__sysrq_get_key_op(int key)
491 {
492         struct sysrq_key_op *op_p = NULL;
493         int i;
494 
495         i = sysrq_key_table_key2index(key);
496         if (i != -1)
497                 op_p = sysrq_key_table[i];
498 
499         return op_p;
500 }
501 
502 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
503 {
504         int i = sysrq_key_table_key2index(key);
505 
506         if (i != -1)
507                 sysrq_key_table[i] = op_p;
508 }
509 
510 void __handle_sysrq(int key, bool check_mask)
511 {
512         struct sysrq_key_op *op_p;
513         int orig_log_level;
514         int i;
515 
516         rcu_sysrq_start();
517         rcu_read_lock();
518         /*
519          * Raise the apparent loglevel to maximum so that the sysrq header
520          * is shown to provide the user with positive feedback.  We do not
521          * simply emit this at KERN_EMERG as that would change message
522          * routing in the consumers of /proc/kmsg.
523          */
524         orig_log_level = console_loglevel;
525         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
526         pr_info("SysRq : ");
527 
528         op_p = __sysrq_get_key_op(key);
529         if (op_p) {
530                 /*
531                  * Should we check for enabled operations (/proc/sysrq-trigger
532                  * should not) and is the invoked operation enabled?
533                  */
534                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
535                         pr_cont("%s\n", op_p->action_msg);
536                         console_loglevel = orig_log_level;
537                         op_p->handler(key);
538                 } else {
539                         pr_cont("This sysrq operation is disabled.\n");
540                 }
541         } else {
542                 pr_cont("HELP : ");
543                 /* Only print the help msg once per handler */
544                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
545                         if (sysrq_key_table[i]) {
546                                 int j;
547 
548                                 for (j = 0; sysrq_key_table[i] !=
549                                                 sysrq_key_table[j]; j++)
550                                         ;
551                                 if (j != i)
552                                         continue;
553                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
554                         }
555                 }
556                 pr_cont("\n");
557                 console_loglevel = orig_log_level;
558         }
559         rcu_read_unlock();
560         rcu_sysrq_end();
561 }
562 
563 void handle_sysrq(int key)
564 {
565         if (sysrq_on())
566                 __handle_sysrq(key, true);
567 }
568 EXPORT_SYMBOL(handle_sysrq);
569 
570 #ifdef CONFIG_INPUT
571 
572 /* Simple translation table for the SysRq keys */
573 static const unsigned char sysrq_xlate[KEY_CNT] =
574         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
575         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
576         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
577         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
578         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
579         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
580         "\r\000/";                                      /* 0x60 - 0x6f */
581 
582 struct sysrq_state {
583         struct input_handle handle;
584         struct work_struct reinject_work;
585         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
586         unsigned int alt;
587         unsigned int alt_use;
588         bool active;
589         bool need_reinject;
590         bool reinjecting;
591 
592         /* reset sequence handling */
593         bool reset_canceled;
594         bool reset_requested;
595         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
596         int reset_seq_len;
597         int reset_seq_cnt;
598         int reset_seq_version;
599         struct timer_list keyreset_timer;
600 };
601 
602 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
603 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
604 static unsigned int sysrq_reset_seq_len;
605 static unsigned int sysrq_reset_seq_version = 1;
606 
607 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
608 {
609         int i;
610         unsigned short key;
611 
612         state->reset_seq_cnt = 0;
613 
614         for (i = 0; i < sysrq_reset_seq_len; i++) {
615                 key = sysrq_reset_seq[i];
616 
617                 if (key == KEY_RESERVED || key > KEY_MAX)
618                         break;
619 
620                 __set_bit(key, state->reset_keybit);
621                 state->reset_seq_len++;
622 
623                 if (test_bit(key, state->key_down))
624                         state->reset_seq_cnt++;
625         }
626 
627         /* Disable reset until old keys are not released */
628         state->reset_canceled = state->reset_seq_cnt != 0;
629 
630         state->reset_seq_version = sysrq_reset_seq_version;
631 }
632 
633 static void sysrq_do_reset(unsigned long _state)
634 {
635         struct sysrq_state *state = (struct sysrq_state *) _state;
636 
637         state->reset_requested = true;
638 
639         sys_sync();
640         kernel_restart(NULL);
641 }
642 
643 static void sysrq_handle_reset_request(struct sysrq_state *state)
644 {
645         if (state->reset_requested)
646                 __handle_sysrq(sysrq_xlate[KEY_B], false);
647 
648         if (sysrq_reset_downtime_ms)
649                 mod_timer(&state->keyreset_timer,
650                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
651         else
652                 sysrq_do_reset((unsigned long)state);
653 }
654 
655 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
656                                         unsigned int code, int value)
657 {
658         if (!test_bit(code, state->reset_keybit)) {
659                 /*
660                  * Pressing any key _not_ in reset sequence cancels
661                  * the reset sequence.  Also cancelling the timer in
662                  * case additional keys were pressed after a reset
663                  * has been requested.
664                  */
665                 if (value && state->reset_seq_cnt) {
666                         state->reset_canceled = true;
667                         del_timer(&state->keyreset_timer);
668                 }
669         } else if (value == 0) {
670                 /*
671                  * Key release - all keys in the reset sequence need
672                  * to be pressed and held for the reset timeout
673                  * to hold.
674                  */
675                 del_timer(&state->keyreset_timer);
676 
677                 if (--state->reset_seq_cnt == 0)
678                         state->reset_canceled = false;
679         } else if (value == 1) {
680                 /* key press, not autorepeat */
681                 if (++state->reset_seq_cnt == state->reset_seq_len &&
682                     !state->reset_canceled) {
683                         sysrq_handle_reset_request(state);
684                 }
685         }
686 }
687 
688 #ifdef CONFIG_OF
689 static void sysrq_of_get_keyreset_config(void)
690 {
691         u32 key;
692         struct device_node *np;
693         struct property *prop;
694         const __be32 *p;
695 
696         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
697         if (!np) {
698                 pr_debug("No sysrq node found");
699                 return;
700         }
701 
702         /* Reset in case a __weak definition was present */
703         sysrq_reset_seq_len = 0;
704 
705         of_property_for_each_u32(np, "keyset", prop, p, key) {
706                 if (key == KEY_RESERVED || key > KEY_MAX ||
707                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
708                         break;
709 
710                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
711         }
712 
713         /* Get reset timeout if any. */
714         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
715 }
716 #else
717 static void sysrq_of_get_keyreset_config(void)
718 {
719 }
720 #endif
721 
722 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
723 {
724         struct sysrq_state *sysrq =
725                         container_of(work, struct sysrq_state, reinject_work);
726         struct input_handle *handle = &sysrq->handle;
727         unsigned int alt_code = sysrq->alt_use;
728 
729         if (sysrq->need_reinject) {
730                 /* we do not want the assignment to be reordered */
731                 sysrq->reinjecting = true;
732                 mb();
733 
734                 /* Simulate press and release of Alt + SysRq */
735                 input_inject_event(handle, EV_KEY, alt_code, 1);
736                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
737                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
738 
739                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
740                 input_inject_event(handle, EV_KEY, alt_code, 0);
741                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
742 
743                 mb();
744                 sysrq->reinjecting = false;
745         }
746 }
747 
748 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
749                                   unsigned int code, int value)
750 {
751         bool was_active = sysrq->active;
752         bool suppress;
753 
754         switch (code) {
755 
756         case KEY_LEFTALT:
757         case KEY_RIGHTALT:
758                 if (!value) {
759                         /* One of ALTs is being released */
760                         if (sysrq->active && code == sysrq->alt_use)
761                                 sysrq->active = false;
762 
763                         sysrq->alt = KEY_RESERVED;
764 
765                 } else if (value != 2) {
766                         sysrq->alt = code;
767                         sysrq->need_reinject = false;
768                 }
769                 break;
770 
771         case KEY_SYSRQ:
772                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
773                         sysrq->active = true;
774                         sysrq->alt_use = sysrq->alt;
775                         /*
776                          * If nothing else will be pressed we'll need
777                          * to re-inject Alt-SysRq keysroke.
778                          */
779                         sysrq->need_reinject = true;
780                 }
781 
782                 /*
783                  * Pretend that sysrq was never pressed at all. This
784                  * is needed to properly handle KGDB which will try
785                  * to release all keys after exiting debugger. If we
786                  * do not clear key bit it KGDB will end up sending
787                  * release events for Alt and SysRq, potentially
788                  * triggering print screen function.
789                  */
790                 if (sysrq->active)
791                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
792 
793                 break;
794 
795         default:
796                 if (sysrq->active && value && value != 2) {
797                         sysrq->need_reinject = false;
798                         __handle_sysrq(sysrq_xlate[code], true);
799                 }
800                 break;
801         }
802 
803         suppress = sysrq->active;
804 
805         if (!sysrq->active) {
806 
807                 /*
808                  * See if reset sequence has changed since the last time.
809                  */
810                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
811                         sysrq_parse_reset_sequence(sysrq);
812 
813                 /*
814                  * If we are not suppressing key presses keep track of
815                  * keyboard state so we can release keys that have been
816                  * pressed before entering SysRq mode.
817                  */
818                 if (value)
819                         set_bit(code, sysrq->key_down);
820                 else
821                         clear_bit(code, sysrq->key_down);
822 
823                 if (was_active)
824                         schedule_work(&sysrq->reinject_work);
825 
826                 /* Check for reset sequence */
827                 sysrq_detect_reset_sequence(sysrq, code, value);
828 
829         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
830                 /*
831                  * Pass on release events for keys that was pressed before
832                  * entering SysRq mode.
833                  */
834                 suppress = false;
835         }
836 
837         return suppress;
838 }
839 
840 static bool sysrq_filter(struct input_handle *handle,
841                          unsigned int type, unsigned int code, int value)
842 {
843         struct sysrq_state *sysrq = handle->private;
844         bool suppress;
845 
846         /*
847          * Do not filter anything if we are in the process of re-injecting
848          * Alt+SysRq combination.
849          */
850         if (sysrq->reinjecting)
851                 return false;
852 
853         switch (type) {
854 
855         case EV_SYN:
856                 suppress = false;
857                 break;
858 
859         case EV_KEY:
860                 suppress = sysrq_handle_keypress(sysrq, code, value);
861                 break;
862 
863         default:
864                 suppress = sysrq->active;
865                 break;
866         }
867 
868         return suppress;
869 }
870 
871 static int sysrq_connect(struct input_handler *handler,
872                          struct input_dev *dev,
873                          const struct input_device_id *id)
874 {
875         struct sysrq_state *sysrq;
876         int error;
877 
878         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
879         if (!sysrq)
880                 return -ENOMEM;
881 
882         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
883 
884         sysrq->handle.dev = dev;
885         sysrq->handle.handler = handler;
886         sysrq->handle.name = "sysrq";
887         sysrq->handle.private = sysrq;
888         setup_timer(&sysrq->keyreset_timer,
889                     sysrq_do_reset, (unsigned long)sysrq);
890 
891         error = input_register_handle(&sysrq->handle);
892         if (error) {
893                 pr_err("Failed to register input sysrq handler, error %d\n",
894                         error);
895                 goto err_free;
896         }
897 
898         error = input_open_device(&sysrq->handle);
899         if (error) {
900                 pr_err("Failed to open input device, error %d\n", error);
901                 goto err_unregister;
902         }
903 
904         return 0;
905 
906  err_unregister:
907         input_unregister_handle(&sysrq->handle);
908  err_free:
909         kfree(sysrq);
910         return error;
911 }
912 
913 static void sysrq_disconnect(struct input_handle *handle)
914 {
915         struct sysrq_state *sysrq = handle->private;
916 
917         input_close_device(handle);
918         cancel_work_sync(&sysrq->reinject_work);
919         del_timer_sync(&sysrq->keyreset_timer);
920         input_unregister_handle(handle);
921         kfree(sysrq);
922 }
923 
924 /*
925  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
926  * keyboards have SysRq key predefined and so user may add it to keymap
927  * later, but we expect all such keyboards to have left alt.
928  */
929 static const struct input_device_id sysrq_ids[] = {
930         {
931                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
932                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
933                 .evbit = { BIT_MASK(EV_KEY) },
934                 .keybit = { BIT_MASK(KEY_LEFTALT) },
935         },
936         { },
937 };
938 
939 static struct input_handler sysrq_handler = {
940         .filter         = sysrq_filter,
941         .connect        = sysrq_connect,
942         .disconnect     = sysrq_disconnect,
943         .name           = "sysrq",
944         .id_table       = sysrq_ids,
945 };
946 
947 static bool sysrq_handler_registered;
948 
949 static inline void sysrq_register_handler(void)
950 {
951         unsigned short key;
952         int error;
953         int i;
954 
955         /* First check if a __weak interface was instantiated. */
956         for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
957                 key = platform_sysrq_reset_seq[i];
958                 if (key == KEY_RESERVED || key > KEY_MAX)
959                         break;
960 
961                 sysrq_reset_seq[sysrq_reset_seq_len++] = key;
962         }
963 
964         /*
965          * DT configuration takes precedence over anything that would
966          * have been defined via the __weak interface.
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 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 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1013                          &sysrq_reset_seq_len, 0644);
1014 
1015 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1016 
1017 #else
1018 
1019 static inline void sysrq_register_handler(void)
1020 {
1021 }
1022 
1023 static inline void sysrq_unregister_handler(void)
1024 {
1025 }
1026 
1027 #endif /* CONFIG_INPUT */
1028 
1029 int sysrq_toggle_support(int enable_mask)
1030 {
1031         bool was_enabled = sysrq_on();
1032 
1033         sysrq_enabled = enable_mask;
1034 
1035         if (was_enabled != sysrq_on()) {
1036                 if (sysrq_on())
1037                         sysrq_register_handler();
1038                 else
1039                         sysrq_unregister_handler();
1040         }
1041 
1042         return 0;
1043 }
1044 
1045 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1046                                 struct sysrq_key_op *remove_op_p)
1047 {
1048         int retval;
1049 
1050         spin_lock(&sysrq_key_table_lock);
1051         if (__sysrq_get_key_op(key) == remove_op_p) {
1052                 __sysrq_put_key_op(key, insert_op_p);
1053                 retval = 0;
1054         } else {
1055                 retval = -1;
1056         }
1057         spin_unlock(&sysrq_key_table_lock);
1058 
1059         /*
1060          * A concurrent __handle_sysrq either got the old op or the new op.
1061          * Wait for it to go away before returning, so the code for an old
1062          * op is not freed (eg. on module unload) while it is in use.
1063          */
1064         synchronize_rcu();
1065 
1066         return retval;
1067 }
1068 
1069 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1070 {
1071         return __sysrq_swap_key_ops(key, op_p, NULL);
1072 }
1073 EXPORT_SYMBOL(register_sysrq_key);
1074 
1075 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1076 {
1077         return __sysrq_swap_key_ops(key, NULL, op_p);
1078 }
1079 EXPORT_SYMBOL(unregister_sysrq_key);
1080 
1081 #ifdef CONFIG_PROC_FS
1082 /*
1083  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1084  */
1085 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1086                                    size_t count, loff_t *ppos)
1087 {
1088         if (count) {
1089                 char c;
1090 
1091                 if (get_user(c, buf))
1092                         return -EFAULT;
1093                 __handle_sysrq(c, false);
1094         }
1095 
1096         return count;
1097 }
1098 
1099 static const struct file_operations proc_sysrq_trigger_operations = {
1100         .write          = write_sysrq_trigger,
1101         .llseek         = noop_llseek,
1102 };
1103 
1104 static void sysrq_init_procfs(void)
1105 {
1106         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1107                          &proc_sysrq_trigger_operations))
1108                 pr_err("Failed to register proc interface\n");
1109 }
1110 
1111 #else
1112 
1113 static inline void sysrq_init_procfs(void)
1114 {
1115 }
1116 
1117 #endif /* CONFIG_PROC_FS */
1118 
1119 static int __init sysrq_init(void)
1120 {
1121         sysrq_init_procfs();
1122 
1123         if (sysrq_on())
1124                 sysrq_register_handler();
1125 
1126         return 0;
1127 }
1128 module_init(sysrq_init);
1129 

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