Version:  2.0.40 2.2.26 2.4.37 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 4.1

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

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