Version:  2.0.40 2.2.26 2.4.37 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4

Linux/drivers/tty/sysrq.c

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

This page was automatically generated by LXR 0.3.1 (source).  •  Linux is a registered trademark of Linus Torvalds  •  Contact us