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