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