1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Linux Magic System Request Key Hacks
4 *
5 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
6 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
7 *
8 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
9 * overhauled to use key registration
10 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies
11 *
12 * Copyright (c) 2010 Dmitry Torokhov
13 * Input handler conversion
14 */
15
16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17
18 #include <linux/sched/signal.h>
19 #include <linux/sched/rt.h>
20 #include <linux/sched/debug.h>
21 #include <linux/sched/task.h>
22 #include <linux/ctype.h>
23 #include <linux/interrupt.h>
24 #include <linux/mm.h>
25 #include <linux/fs.h>
26 #include <linux/mount.h>
27 #include <linux/kdev_t.h>
28 #include <linux/major.h>
29 #include <linux/reboot.h>
30 #include <linux/sysrq.h>
31 #include <linux/kbd_kern.h>
32 #include <linux/proc_fs.h>
33 #include <linux/nmi.h>
34 #include <linux/quotaops.h>
35 #include <linux/perf_event.h>
36 #include <linux/kernel.h>
37 #include <linux/module.h>
38 #include <linux/suspend.h>
39 #include <linux/writeback.h>
40 #include <linux/swap.h>
41 #include <linux/spinlock.h>
42 #include <linux/vt_kern.h>
43 #include <linux/workqueue.h>
44 #include <linux/hrtimer.h>
45 #include <linux/oom.h>
46 #include <linux/slab.h>
47 #include <linux/input.h>
48 #include <linux/uaccess.h>
49 #include <linux/moduleparam.h>
50 #include <linux/jiffies.h>
51 #include <linux/syscalls.h>
52 #include <linux/of.h>
53 #include <linux/rcupdate.h>
54
55 #include <asm/ptrace.h>
56 #include <asm/irq_regs.h>
57
58 /* Whether we react on sysrq keys or just ignore them */
59 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
60 static bool __read_mostly sysrq_always_enabled;
61
sysrq_on(void)62 static bool sysrq_on(void)
63 {
64 return sysrq_enabled || sysrq_always_enabled;
65 }
66
67 /**
68 * sysrq_mask - Getter for sysrq_enabled mask.
69 *
70 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
71 */
sysrq_mask(void)72 int sysrq_mask(void)
73 {
74 if (sysrq_always_enabled)
75 return 1;
76 return sysrq_enabled;
77 }
78 EXPORT_SYMBOL_GPL(sysrq_mask);
79
80 /*
81 * A value of 1 means 'all', other nonzero values are an op mask:
82 */
sysrq_on_mask(int mask)83 static bool sysrq_on_mask(int mask)
84 {
85 return sysrq_always_enabled ||
86 sysrq_enabled == 1 ||
87 (sysrq_enabled & mask);
88 }
89
sysrq_always_enabled_setup(char * str)90 static int __init sysrq_always_enabled_setup(char *str)
91 {
92 sysrq_always_enabled = true;
93 pr_info("sysrq always enabled.\n");
94
95 return 1;
96 }
97
98 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
99
100
sysrq_handle_loglevel(int key)101 static void sysrq_handle_loglevel(int key)
102 {
103 int i;
104
105 i = key - '0';
106 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
107 pr_info("Loglevel set to %d\n", i);
108 console_loglevel = i;
109 }
110 static const struct sysrq_key_op sysrq_loglevel_op = {
111 .handler = sysrq_handle_loglevel,
112 .help_msg = "loglevel(0-9)",
113 .action_msg = "Changing Loglevel",
114 .enable_mask = SYSRQ_ENABLE_LOG,
115 };
116
117 #ifdef CONFIG_VT
sysrq_handle_SAK(int key)118 static void sysrq_handle_SAK(int key)
119 {
120 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
121 schedule_work(SAK_work);
122 }
123 static const struct sysrq_key_op sysrq_SAK_op = {
124 .handler = sysrq_handle_SAK,
125 .help_msg = "sak(k)",
126 .action_msg = "SAK",
127 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
128 };
129 #else
130 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
131 #endif
132
133 #ifdef CONFIG_VT
sysrq_handle_unraw(int key)134 static void sysrq_handle_unraw(int key)
135 {
136 vt_reset_unicode(fg_console);
137 }
138
139 static const struct sysrq_key_op sysrq_unraw_op = {
140 .handler = sysrq_handle_unraw,
141 .help_msg = "unraw(r)",
142 .action_msg = "Keyboard mode set to system default",
143 .enable_mask = SYSRQ_ENABLE_KEYBOARD,
144 };
145 #else
146 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
147 #endif /* CONFIG_VT */
148
sysrq_handle_crash(int key)149 static void sysrq_handle_crash(int key)
150 {
151 /* release the RCU read lock before crashing */
152 rcu_read_unlock();
153
154 panic("sysrq triggered crash\n");
155 }
156 static const struct sysrq_key_op sysrq_crash_op = {
157 .handler = sysrq_handle_crash,
158 .help_msg = "crash(c)",
159 .action_msg = "Trigger a crash",
160 .enable_mask = SYSRQ_ENABLE_DUMP,
161 };
162
sysrq_handle_reboot(int key)163 static void sysrq_handle_reboot(int key)
164 {
165 lockdep_off();
166 local_irq_enable();
167 emergency_restart();
168 }
169 static const struct sysrq_key_op sysrq_reboot_op = {
170 .handler = sysrq_handle_reboot,
171 .help_msg = "reboot(b)",
172 .action_msg = "Resetting",
173 .enable_mask = SYSRQ_ENABLE_BOOT,
174 };
175
176 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
177
sysrq_handle_sync(int key)178 static void sysrq_handle_sync(int key)
179 {
180 emergency_sync();
181 }
182 static const struct sysrq_key_op sysrq_sync_op = {
183 .handler = sysrq_handle_sync,
184 .help_msg = "sync(s)",
185 .action_msg = "Emergency Sync",
186 .enable_mask = SYSRQ_ENABLE_SYNC,
187 };
188
sysrq_handle_show_timers(int key)189 static void sysrq_handle_show_timers(int key)
190 {
191 sysrq_timer_list_show();
192 }
193
194 static const struct sysrq_key_op sysrq_show_timers_op = {
195 .handler = sysrq_handle_show_timers,
196 .help_msg = "show-all-timers(q)",
197 .action_msg = "Show clockevent devices & pending hrtimers (no others)",
198 };
199
sysrq_handle_mountro(int key)200 static void sysrq_handle_mountro(int key)
201 {
202 emergency_remount();
203 }
204 static const struct sysrq_key_op sysrq_mountro_op = {
205 .handler = sysrq_handle_mountro,
206 .help_msg = "unmount(u)",
207 .action_msg = "Emergency Remount R/O",
208 .enable_mask = SYSRQ_ENABLE_REMOUNT,
209 };
210
211 #ifdef CONFIG_LOCKDEP
sysrq_handle_showlocks(int key)212 static void sysrq_handle_showlocks(int key)
213 {
214 debug_show_all_locks();
215 }
216
217 static const struct sysrq_key_op sysrq_showlocks_op = {
218 .handler = sysrq_handle_showlocks,
219 .help_msg = "show-all-locks(d)",
220 .action_msg = "Show Locks Held",
221 };
222 #else
223 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
224 #endif
225
226 #ifdef CONFIG_SMP
227 static DEFINE_RAW_SPINLOCK(show_lock);
228
showacpu(void * dummy)229 static void showacpu(void *dummy)
230 {
231 unsigned long flags;
232
233 /* Idle CPUs have no interesting backtrace. */
234 if (idle_cpu(smp_processor_id()))
235 return;
236
237 raw_spin_lock_irqsave(&show_lock, flags);
238 pr_info("CPU%d:\n", smp_processor_id());
239 show_stack(NULL, NULL, KERN_INFO);
240 raw_spin_unlock_irqrestore(&show_lock, flags);
241 }
242
sysrq_showregs_othercpus(struct work_struct * dummy)243 static void sysrq_showregs_othercpus(struct work_struct *dummy)
244 {
245 smp_call_function(showacpu, NULL, 0);
246 }
247
248 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
249
sysrq_handle_showallcpus(int key)250 static void sysrq_handle_showallcpus(int key)
251 {
252 /*
253 * Fall back to the workqueue based printing if the
254 * backtrace printing did not succeed or the
255 * architecture has no support for it:
256 */
257 if (!trigger_all_cpu_backtrace()) {
258 struct pt_regs *regs = NULL;
259
260 if (in_irq())
261 regs = get_irq_regs();
262 if (regs) {
263 pr_info("CPU%d:\n", smp_processor_id());
264 show_regs(regs);
265 }
266 schedule_work(&sysrq_showallcpus);
267 }
268 }
269
270 static const struct sysrq_key_op sysrq_showallcpus_op = {
271 .handler = sysrq_handle_showallcpus,
272 .help_msg = "show-backtrace-all-active-cpus(l)",
273 .action_msg = "Show backtrace of all active CPUs",
274 .enable_mask = SYSRQ_ENABLE_DUMP,
275 };
276 #endif
277
sysrq_handle_showregs(int key)278 static void sysrq_handle_showregs(int key)
279 {
280 struct pt_regs *regs = NULL;
281
282 if (in_irq())
283 regs = get_irq_regs();
284 if (regs)
285 show_regs(regs);
286 perf_event_print_debug();
287 }
288 static const struct sysrq_key_op sysrq_showregs_op = {
289 .handler = sysrq_handle_showregs,
290 .help_msg = "show-registers(p)",
291 .action_msg = "Show Regs",
292 .enable_mask = SYSRQ_ENABLE_DUMP,
293 };
294
sysrq_handle_showstate(int key)295 static void sysrq_handle_showstate(int key)
296 {
297 show_state();
298 show_workqueue_state();
299 }
300 static const struct sysrq_key_op sysrq_showstate_op = {
301 .handler = sysrq_handle_showstate,
302 .help_msg = "show-task-states(t)",
303 .action_msg = "Show State",
304 .enable_mask = SYSRQ_ENABLE_DUMP,
305 };
306
sysrq_handle_showstate_blocked(int key)307 static void sysrq_handle_showstate_blocked(int key)
308 {
309 show_state_filter(TASK_UNINTERRUPTIBLE);
310 }
311 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
312 .handler = sysrq_handle_showstate_blocked,
313 .help_msg = "show-blocked-tasks(w)",
314 .action_msg = "Show Blocked State",
315 .enable_mask = SYSRQ_ENABLE_DUMP,
316 };
317
318 #ifdef CONFIG_TRACING
319 #include <linux/ftrace.h>
320
sysrq_ftrace_dump(int key)321 static void sysrq_ftrace_dump(int key)
322 {
323 ftrace_dump(DUMP_ALL);
324 }
325 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
326 .handler = sysrq_ftrace_dump,
327 .help_msg = "dump-ftrace-buffer(z)",
328 .action_msg = "Dump ftrace buffer",
329 .enable_mask = SYSRQ_ENABLE_DUMP,
330 };
331 #else
332 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
333 #endif
334
sysrq_handle_showmem(int key)335 static void sysrq_handle_showmem(int key)
336 {
337 show_mem(0, NULL);
338 }
339 static const struct sysrq_key_op sysrq_showmem_op = {
340 .handler = sysrq_handle_showmem,
341 .help_msg = "show-memory-usage(m)",
342 .action_msg = "Show Memory",
343 .enable_mask = SYSRQ_ENABLE_DUMP,
344 };
345
346 /*
347 * Signal sysrq helper function. Sends a signal to all user processes.
348 */
send_sig_all(int sig)349 static void send_sig_all(int sig)
350 {
351 struct task_struct *p;
352
353 read_lock(&tasklist_lock);
354 for_each_process(p) {
355 if (p->flags & PF_KTHREAD)
356 continue;
357 if (is_global_init(p))
358 continue;
359
360 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
361 }
362 read_unlock(&tasklist_lock);
363 }
364
sysrq_handle_term(int key)365 static void sysrq_handle_term(int key)
366 {
367 send_sig_all(SIGTERM);
368 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
369 }
370 static const struct sysrq_key_op sysrq_term_op = {
371 .handler = sysrq_handle_term,
372 .help_msg = "terminate-all-tasks(e)",
373 .action_msg = "Terminate All Tasks",
374 .enable_mask = SYSRQ_ENABLE_SIGNAL,
375 };
376
moom_callback(struct work_struct * ignored)377 static void moom_callback(struct work_struct *ignored)
378 {
379 const gfp_t gfp_mask = GFP_KERNEL;
380 struct oom_control oc = {
381 .zonelist = node_zonelist(first_memory_node, gfp_mask),
382 .nodemask = NULL,
383 .memcg = NULL,
384 .gfp_mask = gfp_mask,
385 .order = -1,
386 };
387
388 mutex_lock(&oom_lock);
389 if (!out_of_memory(&oc))
390 pr_info("OOM request ignored. No task eligible\n");
391 mutex_unlock(&oom_lock);
392 }
393
394 static DECLARE_WORK(moom_work, moom_callback);
395
sysrq_handle_moom(int key)396 static void sysrq_handle_moom(int key)
397 {
398 schedule_work(&moom_work);
399 }
400 static const struct sysrq_key_op sysrq_moom_op = {
401 .handler = sysrq_handle_moom,
402 .help_msg = "memory-full-oom-kill(f)",
403 .action_msg = "Manual OOM execution",
404 .enable_mask = SYSRQ_ENABLE_SIGNAL,
405 };
406
sysrq_handle_thaw(int key)407 static void sysrq_handle_thaw(int key)
408 {
409 emergency_thaw_all();
410 }
411 static const struct sysrq_key_op sysrq_thaw_op = {
412 .handler = sysrq_handle_thaw,
413 .help_msg = "thaw-filesystems(j)",
414 .action_msg = "Emergency Thaw of all frozen filesystems",
415 .enable_mask = SYSRQ_ENABLE_SIGNAL,
416 };
417
sysrq_handle_kill(int key)418 static void sysrq_handle_kill(int key)
419 {
420 send_sig_all(SIGKILL);
421 console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
422 }
423 static const struct sysrq_key_op sysrq_kill_op = {
424 .handler = sysrq_handle_kill,
425 .help_msg = "kill-all-tasks(i)",
426 .action_msg = "Kill All Tasks",
427 .enable_mask = SYSRQ_ENABLE_SIGNAL,
428 };
429
sysrq_handle_unrt(int key)430 static void sysrq_handle_unrt(int key)
431 {
432 normalize_rt_tasks();
433 }
434 static const struct sysrq_key_op sysrq_unrt_op = {
435 .handler = sysrq_handle_unrt,
436 .help_msg = "nice-all-RT-tasks(n)",
437 .action_msg = "Nice All RT Tasks",
438 .enable_mask = SYSRQ_ENABLE_RTNICE,
439 };
440
441 /* Key Operations table and lock */
442 static DEFINE_SPINLOCK(sysrq_key_table_lock);
443
444 static const struct sysrq_key_op *sysrq_key_table[62] = {
445 &sysrq_loglevel_op, /* 0 */
446 &sysrq_loglevel_op, /* 1 */
447 &sysrq_loglevel_op, /* 2 */
448 &sysrq_loglevel_op, /* 3 */
449 &sysrq_loglevel_op, /* 4 */
450 &sysrq_loglevel_op, /* 5 */
451 &sysrq_loglevel_op, /* 6 */
452 &sysrq_loglevel_op, /* 7 */
453 &sysrq_loglevel_op, /* 8 */
454 &sysrq_loglevel_op, /* 9 */
455
456 /*
457 * a: Don't use for system provided sysrqs, it is handled specially on
458 * sparc and will never arrive.
459 */
460 NULL, /* a */
461 &sysrq_reboot_op, /* b */
462 &sysrq_crash_op, /* c */
463 &sysrq_showlocks_op, /* d */
464 &sysrq_term_op, /* e */
465 &sysrq_moom_op, /* f */
466 /* g: May be registered for the kernel debugger */
467 NULL, /* g */
468 NULL, /* h - reserved for help */
469 &sysrq_kill_op, /* i */
470 #ifdef CONFIG_BLOCK
471 &sysrq_thaw_op, /* j */
472 #else
473 NULL, /* j */
474 #endif
475 &sysrq_SAK_op, /* k */
476 #ifdef CONFIG_SMP
477 &sysrq_showallcpus_op, /* l */
478 #else
479 NULL, /* l */
480 #endif
481 &sysrq_showmem_op, /* m */
482 &sysrq_unrt_op, /* n */
483 /* o: This will often be registered as 'Off' at init time */
484 NULL, /* o */
485 &sysrq_showregs_op, /* p */
486 &sysrq_show_timers_op, /* q */
487 &sysrq_unraw_op, /* r */
488 &sysrq_sync_op, /* s */
489 &sysrq_showstate_op, /* t */
490 &sysrq_mountro_op, /* u */
491 /* v: May be registered for frame buffer console restore */
492 NULL, /* v */
493 &sysrq_showstate_blocked_op, /* w */
494 /* x: May be registered on mips for TLB dump */
495 /* x: May be registered on ppc/powerpc for xmon */
496 /* x: May be registered on sparc64 for global PMU dump */
497 NULL, /* x */
498 /* y: May be registered on sparc64 for global register dump */
499 NULL, /* y */
500 &sysrq_ftrace_dump_op, /* z */
501 NULL, /* A */
502 NULL, /* B */
503 NULL, /* C */
504 NULL, /* D */
505 NULL, /* E */
506 NULL, /* F */
507 NULL, /* G */
508 NULL, /* H */
509 NULL, /* I */
510 NULL, /* J */
511 NULL, /* K */
512 NULL, /* L */
513 NULL, /* M */
514 NULL, /* N */
515 NULL, /* O */
516 NULL, /* P */
517 NULL, /* Q */
518 NULL, /* R */
519 NULL, /* S */
520 NULL, /* T */
521 NULL, /* U */
522 NULL, /* V */
523 NULL, /* W */
524 NULL, /* X */
525 NULL, /* Y */
526 NULL, /* Z */
527 };
528
529 /* key2index calculation, -1 on invalid index */
sysrq_key_table_key2index(int key)530 static int sysrq_key_table_key2index(int key)
531 {
532 int retval;
533
534 if ((key >= '0') && (key <= '9'))
535 retval = key - '0';
536 else if ((key >= 'a') && (key <= 'z'))
537 retval = key + 10 - 'a';
538 else if ((key >= 'A') && (key <= 'Z'))
539 retval = key + 36 - 'A';
540 else
541 retval = -1;
542 return retval;
543 }
544
545 /*
546 * get and put functions for the table, exposed to modules.
547 */
__sysrq_get_key_op(int key)548 static const struct sysrq_key_op *__sysrq_get_key_op(int key)
549 {
550 const struct sysrq_key_op *op_p = NULL;
551 int i;
552
553 i = sysrq_key_table_key2index(key);
554 if (i != -1)
555 op_p = sysrq_key_table[i];
556
557 return op_p;
558 }
559
__sysrq_put_key_op(int key,const struct sysrq_key_op * op_p)560 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p)
561 {
562 int i = sysrq_key_table_key2index(key);
563
564 if (i != -1)
565 sysrq_key_table[i] = op_p;
566 }
567
__handle_sysrq(int key,bool check_mask)568 void __handle_sysrq(int key, bool check_mask)
569 {
570 const struct sysrq_key_op *op_p;
571 int orig_log_level;
572 int orig_suppress_printk;
573 int i;
574
575 orig_suppress_printk = suppress_printk;
576 suppress_printk = 0;
577
578 rcu_sysrq_start();
579 rcu_read_lock();
580 /*
581 * Raise the apparent loglevel to maximum so that the sysrq header
582 * is shown to provide the user with positive feedback. We do not
583 * simply emit this at KERN_EMERG as that would change message
584 * routing in the consumers of /proc/kmsg.
585 */
586 orig_log_level = console_loglevel;
587 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
588
589 op_p = __sysrq_get_key_op(key);
590 if (op_p) {
591 /*
592 * Should we check for enabled operations (/proc/sysrq-trigger
593 * should not) and is the invoked operation enabled?
594 */
595 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
596 pr_info("%s\n", op_p->action_msg);
597 console_loglevel = orig_log_level;
598 op_p->handler(key);
599 } else {
600 pr_info("This sysrq operation is disabled.\n");
601 console_loglevel = orig_log_level;
602 }
603 } else {
604 pr_info("HELP : ");
605 /* Only print the help msg once per handler */
606 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
607 if (sysrq_key_table[i]) {
608 int j;
609
610 for (j = 0; sysrq_key_table[i] !=
611 sysrq_key_table[j]; j++)
612 ;
613 if (j != i)
614 continue;
615 pr_cont("%s ", sysrq_key_table[i]->help_msg);
616 }
617 }
618 pr_cont("\n");
619 console_loglevel = orig_log_level;
620 }
621 rcu_read_unlock();
622 rcu_sysrq_end();
623
624 suppress_printk = orig_suppress_printk;
625 }
626
handle_sysrq(int key)627 void handle_sysrq(int key)
628 {
629 if (sysrq_on())
630 __handle_sysrq(key, true);
631 }
632 EXPORT_SYMBOL(handle_sysrq);
633
634 #ifdef CONFIG_INPUT
635 static int sysrq_reset_downtime_ms;
636
637 /* Simple translation table for the SysRq keys */
638 static const unsigned char sysrq_xlate[KEY_CNT] =
639 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */
640 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */
641 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */
642 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */
643 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */
644 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
645 "\r\000/"; /* 0x60 - 0x6f */
646
647 struct sysrq_state {
648 struct input_handle handle;
649 struct work_struct reinject_work;
650 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
651 unsigned int alt;
652 unsigned int alt_use;
653 unsigned int shift;
654 unsigned int shift_use;
655 bool active;
656 bool need_reinject;
657 bool reinjecting;
658
659 /* reset sequence handling */
660 bool reset_canceled;
661 bool reset_requested;
662 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
663 int reset_seq_len;
664 int reset_seq_cnt;
665 int reset_seq_version;
666 struct timer_list keyreset_timer;
667 };
668
669 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */
670 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
671 static unsigned int sysrq_reset_seq_len;
672 static unsigned int sysrq_reset_seq_version = 1;
673
sysrq_parse_reset_sequence(struct sysrq_state * state)674 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
675 {
676 int i;
677 unsigned short key;
678
679 state->reset_seq_cnt = 0;
680
681 for (i = 0; i < sysrq_reset_seq_len; i++) {
682 key = sysrq_reset_seq[i];
683
684 if (key == KEY_RESERVED || key > KEY_MAX)
685 break;
686
687 __set_bit(key, state->reset_keybit);
688 state->reset_seq_len++;
689
690 if (test_bit(key, state->key_down))
691 state->reset_seq_cnt++;
692 }
693
694 /* Disable reset until old keys are not released */
695 state->reset_canceled = state->reset_seq_cnt != 0;
696
697 state->reset_seq_version = sysrq_reset_seq_version;
698 }
699
sysrq_do_reset(struct timer_list * t)700 static void sysrq_do_reset(struct timer_list *t)
701 {
702 struct sysrq_state *state = from_timer(state, t, keyreset_timer);
703
704 state->reset_requested = true;
705
706 orderly_reboot();
707 }
708
sysrq_handle_reset_request(struct sysrq_state * state)709 static void sysrq_handle_reset_request(struct sysrq_state *state)
710 {
711 if (state->reset_requested)
712 __handle_sysrq(sysrq_xlate[KEY_B], false);
713
714 if (sysrq_reset_downtime_ms)
715 mod_timer(&state->keyreset_timer,
716 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
717 else
718 sysrq_do_reset(&state->keyreset_timer);
719 }
720
sysrq_detect_reset_sequence(struct sysrq_state * state,unsigned int code,int value)721 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
722 unsigned int code, int value)
723 {
724 if (!test_bit(code, state->reset_keybit)) {
725 /*
726 * Pressing any key _not_ in reset sequence cancels
727 * the reset sequence. Also cancelling the timer in
728 * case additional keys were pressed after a reset
729 * has been requested.
730 */
731 if (value && state->reset_seq_cnt) {
732 state->reset_canceled = true;
733 del_timer(&state->keyreset_timer);
734 }
735 } else if (value == 0) {
736 /*
737 * Key release - all keys in the reset sequence need
738 * to be pressed and held for the reset timeout
739 * to hold.
740 */
741 del_timer(&state->keyreset_timer);
742
743 if (--state->reset_seq_cnt == 0)
744 state->reset_canceled = false;
745 } else if (value == 1) {
746 /* key press, not autorepeat */
747 if (++state->reset_seq_cnt == state->reset_seq_len &&
748 !state->reset_canceled) {
749 sysrq_handle_reset_request(state);
750 }
751 }
752 }
753
754 #ifdef CONFIG_OF
sysrq_of_get_keyreset_config(void)755 static void sysrq_of_get_keyreset_config(void)
756 {
757 u32 key;
758 struct device_node *np;
759 struct property *prop;
760 const __be32 *p;
761
762 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
763 if (!np) {
764 pr_debug("No sysrq node found");
765 return;
766 }
767
768 /* Reset in case a __weak definition was present */
769 sysrq_reset_seq_len = 0;
770
771 of_property_for_each_u32(np, "keyset", prop, p, key) {
772 if (key == KEY_RESERVED || key > KEY_MAX ||
773 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
774 break;
775
776 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
777 }
778
779 /* Get reset timeout if any. */
780 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
781
782 of_node_put(np);
783 }
784 #else
sysrq_of_get_keyreset_config(void)785 static void sysrq_of_get_keyreset_config(void)
786 {
787 }
788 #endif
789
sysrq_reinject_alt_sysrq(struct work_struct * work)790 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
791 {
792 struct sysrq_state *sysrq =
793 container_of(work, struct sysrq_state, reinject_work);
794 struct input_handle *handle = &sysrq->handle;
795 unsigned int alt_code = sysrq->alt_use;
796
797 if (sysrq->need_reinject) {
798 /* we do not want the assignment to be reordered */
799 sysrq->reinjecting = true;
800 mb();
801
802 /* Simulate press and release of Alt + SysRq */
803 input_inject_event(handle, EV_KEY, alt_code, 1);
804 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
805 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
806
807 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
808 input_inject_event(handle, EV_KEY, alt_code, 0);
809 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
810
811 mb();
812 sysrq->reinjecting = false;
813 }
814 }
815
sysrq_handle_keypress(struct sysrq_state * sysrq,unsigned int code,int value)816 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
817 unsigned int code, int value)
818 {
819 bool was_active = sysrq->active;
820 bool suppress;
821
822 switch (code) {
823
824 case KEY_LEFTALT:
825 case KEY_RIGHTALT:
826 if (!value) {
827 /* One of ALTs is being released */
828 if (sysrq->active && code == sysrq->alt_use)
829 sysrq->active = false;
830
831 sysrq->alt = KEY_RESERVED;
832
833 } else if (value != 2) {
834 sysrq->alt = code;
835 sysrq->need_reinject = false;
836 }
837 break;
838
839 case KEY_LEFTSHIFT:
840 case KEY_RIGHTSHIFT:
841 if (!value)
842 sysrq->shift = KEY_RESERVED;
843 else if (value != 2)
844 sysrq->shift = code;
845 break;
846
847 case KEY_SYSRQ:
848 if (value == 1 && sysrq->alt != KEY_RESERVED) {
849 sysrq->active = true;
850 sysrq->alt_use = sysrq->alt;
851 /* either RESERVED (for released) or actual code */
852 sysrq->shift_use = sysrq->shift;
853 /*
854 * If nothing else will be pressed we'll need
855 * to re-inject Alt-SysRq keysroke.
856 */
857 sysrq->need_reinject = true;
858 }
859
860 /*
861 * Pretend that sysrq was never pressed at all. This
862 * is needed to properly handle KGDB which will try
863 * to release all keys after exiting debugger. If we
864 * do not clear key bit it KGDB will end up sending
865 * release events for Alt and SysRq, potentially
866 * triggering print screen function.
867 */
868 if (sysrq->active)
869 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
870
871 break;
872
873 default:
874 if (sysrq->active && value && value != 2) {
875 unsigned char c = sysrq_xlate[code];
876
877 sysrq->need_reinject = false;
878 if (sysrq->shift_use != KEY_RESERVED)
879 c = toupper(c);
880 __handle_sysrq(c, true);
881 }
882 break;
883 }
884
885 suppress = sysrq->active;
886
887 if (!sysrq->active) {
888
889 /*
890 * See if reset sequence has changed since the last time.
891 */
892 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
893 sysrq_parse_reset_sequence(sysrq);
894
895 /*
896 * If we are not suppressing key presses keep track of
897 * keyboard state so we can release keys that have been
898 * pressed before entering SysRq mode.
899 */
900 if (value)
901 set_bit(code, sysrq->key_down);
902 else
903 clear_bit(code, sysrq->key_down);
904
905 if (was_active)
906 schedule_work(&sysrq->reinject_work);
907
908 /* Check for reset sequence */
909 sysrq_detect_reset_sequence(sysrq, code, value);
910
911 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
912 /*
913 * Pass on release events for keys that was pressed before
914 * entering SysRq mode.
915 */
916 suppress = false;
917 }
918
919 return suppress;
920 }
921
sysrq_filter(struct input_handle * handle,unsigned int type,unsigned int code,int value)922 static bool sysrq_filter(struct input_handle *handle,
923 unsigned int type, unsigned int code, int value)
924 {
925 struct sysrq_state *sysrq = handle->private;
926 bool suppress;
927
928 /*
929 * Do not filter anything if we are in the process of re-injecting
930 * Alt+SysRq combination.
931 */
932 if (sysrq->reinjecting)
933 return false;
934
935 switch (type) {
936
937 case EV_SYN:
938 suppress = false;
939 break;
940
941 case EV_KEY:
942 suppress = sysrq_handle_keypress(sysrq, code, value);
943 break;
944
945 default:
946 suppress = sysrq->active;
947 break;
948 }
949
950 return suppress;
951 }
952
sysrq_connect(struct input_handler * handler,struct input_dev * dev,const struct input_device_id * id)953 static int sysrq_connect(struct input_handler *handler,
954 struct input_dev *dev,
955 const struct input_device_id *id)
956 {
957 struct sysrq_state *sysrq;
958 int error;
959
960 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
961 if (!sysrq)
962 return -ENOMEM;
963
964 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
965
966 sysrq->handle.dev = dev;
967 sysrq->handle.handler = handler;
968 sysrq->handle.name = "sysrq";
969 sysrq->handle.private = sysrq;
970 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
971
972 error = input_register_handle(&sysrq->handle);
973 if (error) {
974 pr_err("Failed to register input sysrq handler, error %d\n",
975 error);
976 goto err_free;
977 }
978
979 error = input_open_device(&sysrq->handle);
980 if (error) {
981 pr_err("Failed to open input device, error %d\n", error);
982 goto err_unregister;
983 }
984
985 return 0;
986
987 err_unregister:
988 input_unregister_handle(&sysrq->handle);
989 err_free:
990 kfree(sysrq);
991 return error;
992 }
993
sysrq_disconnect(struct input_handle * handle)994 static void sysrq_disconnect(struct input_handle *handle)
995 {
996 struct sysrq_state *sysrq = handle->private;
997
998 input_close_device(handle);
999 cancel_work_sync(&sysrq->reinject_work);
1000 del_timer_sync(&sysrq->keyreset_timer);
1001 input_unregister_handle(handle);
1002 kfree(sysrq);
1003 }
1004
1005 /*
1006 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1007 * keyboards have SysRq key predefined and so user may add it to keymap
1008 * later, but we expect all such keyboards to have left alt.
1009 */
1010 static const struct input_device_id sysrq_ids[] = {
1011 {
1012 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1013 INPUT_DEVICE_ID_MATCH_KEYBIT,
1014 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1015 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1016 },
1017 { },
1018 };
1019
1020 static struct input_handler sysrq_handler = {
1021 .filter = sysrq_filter,
1022 .connect = sysrq_connect,
1023 .disconnect = sysrq_disconnect,
1024 .name = "sysrq",
1025 .id_table = sysrq_ids,
1026 };
1027
sysrq_register_handler(void)1028 static inline void sysrq_register_handler(void)
1029 {
1030 int error;
1031
1032 sysrq_of_get_keyreset_config();
1033
1034 error = input_register_handler(&sysrq_handler);
1035 if (error)
1036 pr_err("Failed to register input handler, error %d", error);
1037 }
1038
sysrq_unregister_handler(void)1039 static inline void sysrq_unregister_handler(void)
1040 {
1041 input_unregister_handler(&sysrq_handler);
1042 }
1043
sysrq_reset_seq_param_set(const char * buffer,const struct kernel_param * kp)1044 static int sysrq_reset_seq_param_set(const char *buffer,
1045 const struct kernel_param *kp)
1046 {
1047 unsigned long val;
1048 int error;
1049
1050 error = kstrtoul(buffer, 0, &val);
1051 if (error < 0)
1052 return error;
1053
1054 if (val > KEY_MAX)
1055 return -EINVAL;
1056
1057 *((unsigned short *)kp->arg) = val;
1058 sysrq_reset_seq_version++;
1059
1060 return 0;
1061 }
1062
1063 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1064 .get = param_get_ushort,
1065 .set = sysrq_reset_seq_param_set,
1066 };
1067
1068 #define param_check_sysrq_reset_seq(name, p) \
1069 __param_check(name, p, unsigned short)
1070
1071 /*
1072 * not really modular, but the easiest way to keep compat with existing
1073 * bootargs behaviour is to continue using module_param here.
1074 */
1075 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1076 &sysrq_reset_seq_len, 0644);
1077
1078 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1079
1080 #else
1081
sysrq_register_handler(void)1082 static inline void sysrq_register_handler(void)
1083 {
1084 }
1085
sysrq_unregister_handler(void)1086 static inline void sysrq_unregister_handler(void)
1087 {
1088 }
1089
1090 #endif /* CONFIG_INPUT */
1091
sysrq_toggle_support(int enable_mask)1092 int sysrq_toggle_support(int enable_mask)
1093 {
1094 bool was_enabled = sysrq_on();
1095
1096 sysrq_enabled = enable_mask;
1097
1098 if (was_enabled != sysrq_on()) {
1099 if (sysrq_on())
1100 sysrq_register_handler();
1101 else
1102 sysrq_unregister_handler();
1103 }
1104
1105 return 0;
1106 }
1107 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1108
__sysrq_swap_key_ops(int key,const struct sysrq_key_op * insert_op_p,const struct sysrq_key_op * remove_op_p)1109 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p,
1110 const struct sysrq_key_op *remove_op_p)
1111 {
1112 int retval;
1113
1114 spin_lock(&sysrq_key_table_lock);
1115 if (__sysrq_get_key_op(key) == remove_op_p) {
1116 __sysrq_put_key_op(key, insert_op_p);
1117 retval = 0;
1118 } else {
1119 retval = -1;
1120 }
1121 spin_unlock(&sysrq_key_table_lock);
1122
1123 /*
1124 * A concurrent __handle_sysrq either got the old op or the new op.
1125 * Wait for it to go away before returning, so the code for an old
1126 * op is not freed (eg. on module unload) while it is in use.
1127 */
1128 synchronize_rcu();
1129
1130 return retval;
1131 }
1132
register_sysrq_key(int key,const struct sysrq_key_op * op_p)1133 int register_sysrq_key(int key, const struct sysrq_key_op *op_p)
1134 {
1135 return __sysrq_swap_key_ops(key, op_p, NULL);
1136 }
1137 EXPORT_SYMBOL(register_sysrq_key);
1138
unregister_sysrq_key(int key,const struct sysrq_key_op * op_p)1139 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)
1140 {
1141 return __sysrq_swap_key_ops(key, NULL, op_p);
1142 }
1143 EXPORT_SYMBOL(unregister_sysrq_key);
1144
1145 #ifdef CONFIG_PROC_FS
1146 /*
1147 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1148 */
write_sysrq_trigger(struct file * file,const char __user * buf,size_t count,loff_t * ppos)1149 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1150 size_t count, loff_t *ppos)
1151 {
1152 if (count) {
1153 char c;
1154
1155 if (get_user(c, buf))
1156 return -EFAULT;
1157 __handle_sysrq(c, false);
1158 }
1159
1160 return count;
1161 }
1162
1163 static const struct proc_ops sysrq_trigger_proc_ops = {
1164 .proc_write = write_sysrq_trigger,
1165 .proc_lseek = noop_llseek,
1166 };
1167
sysrq_init_procfs(void)1168 static void sysrq_init_procfs(void)
1169 {
1170 if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1171 &sysrq_trigger_proc_ops))
1172 pr_err("Failed to register proc interface\n");
1173 }
1174
1175 #else
1176
sysrq_init_procfs(void)1177 static inline void sysrq_init_procfs(void)
1178 {
1179 }
1180
1181 #endif /* CONFIG_PROC_FS */
1182
sysrq_init(void)1183 static int __init sysrq_init(void)
1184 {
1185 sysrq_init_procfs();
1186
1187 if (sysrq_on())
1188 sysrq_register_handler();
1189
1190 return 0;
1191 }
1192 device_initcall(sysrq_init);
1193
