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