drivers/tty/sysrq.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      Linux Magic System Request Key Hacks
   4  *
   5  *      (c) 1997 Martin Mares <[email protected]>
   6  *      based on ideas by Pavel Machek <[email protected]>
   7  *
   8  *      (c) 2000 Crutcher Dunnavant <[email protected]>
   9  *      overhauled to use key registration
  10  *      based upon discusions in irc://irc.openprojects.net/#kernelnewbies
  11  *
  12  *      Copyright (c) 2010 Dmitry Torokhov
  13  *      Input handler conversion
  14  */
  15
  16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18 #include <linux/sched/signal.h>
  19 #include <linux/sched/rt.h>
  20 #include <linux/sched/debug.h>
  21 #include <linux/sched/task.h>
  22 #include <linux/ctype.h>
  23 #include <linux/interrupt.h>
  24 #include <linux/mm.h>
  25 #include <linux/fs.h>
  26 #include <linux/mount.h>
  27 #include <linux/kdev_t.h>
  28 #include <linux/major.h>
  29 #include <linux/reboot.h>
  30 #include <linux/sysrq.h>
  31 #include <linux/kbd_kern.h>
  32 #include <linux/proc_fs.h>
  33 #include <linux/nmi.h>
  34 #include <linux/quotaops.h>
  35 #include <linux/perf_event.h>
  36 #include <linux/kernel.h>
  37 #include <linux/module.h>
  38 #include <linux/suspend.h>
  39 #include <linux/writeback.h>
  40 #include <linux/swap.h>
  41 #include <linux/spinlock.h>
  42 #include <linux/vt_kern.h>
  43 #include <linux/workqueue.h>
  44 #include <linux/hrtimer.h>
  45 #include <linux/oom.h>
  46 #include <linux/slab.h>
  47 #include <linux/input.h>
  48 #include <linux/uaccess.h>
  49 #include <linux/moduleparam.h>
  50 #include <linux/jiffies.h>
  51 #include <linux/syscalls.h>
  52 #include <linux/of.h>
  53 #include <linux/rcupdate.h>
  54
  55 #include <asm/ptrace.h>
  56 #include <asm/irq_regs.h>
  57
  58 /* Whether we react on sysrq keys or just ignore them */
  59 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
  60 static bool __read_mostly sysrq_always_enabled;
  61
  62 static bool sysrq_on(void)
  63 {
  64         return sysrq_enabled || sysrq_always_enabled;
  65 }
  66
  67 /**
  68  * sysrq_mask - Getter for sysrq_enabled mask.
  69  *
  70  * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
  71  */
  72 int sysrq_mask(void)
  73 {
  74         if (sysrq_always_enabled)
  75                 return 1;
  76         return sysrq_enabled;
  77 }
  78 EXPORT_SYMBOL_GPL(sysrq_mask);
  79
  80 /*
  81  * A value of 1 means 'all', other nonzero values are an op mask:
  82  */
  83 static bool sysrq_on_mask(int mask)
  84 {
  85         return sysrq_always_enabled ||
  86                sysrq_enabled == 1 ||
  87                (sysrq_enabled & mask);
  88 }
  89
  90 static int __init sysrq_always_enabled_setup(char *str)
  91 {
  92         sysrq_always_enabled = true;
  93         pr_info("sysrq always enabled.\n");
  94
  95         return 1;
  96 }
  97
  98 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  99
 100
 101 static void sysrq_handle_loglevel(u8 key)
 102 {
 103         u8 loglevel = key - '0';
 104
 105         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 106         pr_info("Loglevel set to %u\n", loglevel);
 107         console_loglevel = loglevel;
 108 }
 109 static const struct sysrq_key_op sysrq_loglevel_op = {
 110         .handler        = sysrq_handle_loglevel,
 111         .help_msg       = "loglevel(0-9)",
 112         .action_msg     = "Changing Loglevel",
 113         .enable_mask    = SYSRQ_ENABLE_LOG,
 114 };
 115
 116 #ifdef CONFIG_VT
 117 static void sysrq_handle_SAK(u8 key)
 118 {
 119         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 120
 121         schedule_work(SAK_work);
 122 }
 123 static const struct sysrq_key_op sysrq_SAK_op = {
 124         .handler        = sysrq_handle_SAK,
 125         .help_msg       = "sak(k)",
 126         .action_msg     = "SAK",
 127         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 128 };
 129 #else
 130 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
 131 #endif
 132
 133 #ifdef CONFIG_VT
 134 static void sysrq_handle_unraw(u8 key)
 135 {
 136         vt_reset_unicode(fg_console);
 137 }
 138
 139 static const struct sysrq_key_op sysrq_unraw_op = {
 140         .handler        = sysrq_handle_unraw,
 141         .help_msg       = "unraw(r)",
 142         .action_msg     = "Keyboard mode set to system default",
 143         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 144 };
 145 #else
 146 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
 147 #endif /* CONFIG_VT */
 148
 149 static void sysrq_handle_crash(u8 key)
 150 {
 151         /* release the RCU read lock before crashing */
 152         rcu_read_unlock();
 153
 154         panic("sysrq triggered crash\n");
 155 }
 156 static const struct sysrq_key_op sysrq_crash_op = {
 157         .handler        = sysrq_handle_crash,
 158         .help_msg       = "crash(c)",
 159         .action_msg     = "Trigger a crash",
 160         .enable_mask    = SYSRQ_ENABLE_DUMP,
 161 };
 162
 163 static void sysrq_handle_reboot(u8 key)
 164 {
 165         lockdep_off();
 166         local_irq_enable();
 167         emergency_restart();
 168 }
 169 static const struct sysrq_key_op sysrq_reboot_op = {
 170         .handler        = sysrq_handle_reboot,
 171         .help_msg       = "reboot(b)",
 172         .action_msg     = "Resetting",
 173         .enable_mask    = SYSRQ_ENABLE_BOOT,
 174 };
 175
 176 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
 177
 178 static void sysrq_handle_sync(u8 key)
 179 {
 180         emergency_sync();
 181 }
 182 static const struct sysrq_key_op sysrq_sync_op = {
 183         .handler        = sysrq_handle_sync,
 184         .help_msg       = "sync(s)",
 185         .action_msg     = "Emergency Sync",
 186         .enable_mask    = SYSRQ_ENABLE_SYNC,
 187 };
 188
 189 static void sysrq_handle_show_timers(u8 key)
 190 {
 191         sysrq_timer_list_show();
 192 }
 193
 194 static const struct sysrq_key_op sysrq_show_timers_op = {
 195         .handler        = sysrq_handle_show_timers,
 196         .help_msg       = "show-all-timers(q)",
 197         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 198 };
 199
 200 static void sysrq_handle_mountro(u8 key)
 201 {
 202         emergency_remount();
 203 }
 204 static const struct sysrq_key_op sysrq_mountro_op = {
 205         .handler        = sysrq_handle_mountro,
 206         .help_msg       = "unmount(u)",
 207         .action_msg     = "Emergency Remount R/O",
 208         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 209 };
 210
 211 #ifdef CONFIG_LOCKDEP
 212 static void sysrq_handle_showlocks(u8 key)
 213 {
 214         debug_show_all_locks();
 215 }
 216
 217 static const struct sysrq_key_op sysrq_showlocks_op = {
 218         .handler        = sysrq_handle_showlocks,
 219         .help_msg       = "show-all-locks(d)",
 220         .action_msg     = "Show Locks Held",
 221 };
 222 #else
 223 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
 224 #endif
 225
 226 #ifdef CONFIG_SMP
 227 static DEFINE_RAW_SPINLOCK(show_lock);
 228
 229 static void showacpu(void *dummy)
 230 {
 231         unsigned long flags;
 232
 233         /* Idle CPUs have no interesting backtrace. */
 234         if (idle_cpu(smp_processor_id())) {
 235                 pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
 236                 return;
 237         }
 238
 239         raw_spin_lock_irqsave(&show_lock, flags);
 240         pr_info("CPU%d:\n", smp_processor_id());
 241         show_stack(NULL, NULL, KERN_INFO);
 242         raw_spin_unlock_irqrestore(&show_lock, flags);
 243 }
 244
 245 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 246 {
 247         smp_call_function(showacpu, NULL, 0);
 248 }
 249
 250 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 251
 252 static void sysrq_handle_showallcpus(u8 key)
 253 {
 254         /*
 255          * Fall back to the workqueue based printing if the
 256          * backtrace printing did not succeed or the
 257          * architecture has no support for it:
 258          */
 259         if (!trigger_all_cpu_backtrace()) {
 260                 struct pt_regs *regs = NULL;
 261
 262                 if (in_hardirq())
 263                         regs = get_irq_regs();
 264
 265                 pr_info("CPU%d:\n", get_cpu());
 266                 if (regs)
 267                         show_regs(regs);
 268                 else
 269                         show_stack(NULL, NULL, KERN_INFO);
 270
 271                 schedule_work(&sysrq_showallcpus);
 272                 put_cpu();
 273         }
 274 }
 275
 276 static const struct sysrq_key_op sysrq_showallcpus_op = {
 277         .handler        = sysrq_handle_showallcpus,
 278         .help_msg       = "show-backtrace-all-active-cpus(l)",
 279         .action_msg     = "Show backtrace of all active CPUs",
 280         .enable_mask    = SYSRQ_ENABLE_DUMP,
 281 };
 282 #else
 283 #define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL)
 284 #endif
 285
 286 static void sysrq_handle_showregs(u8 key)
 287 {
 288         struct pt_regs *regs = NULL;
 289
 290         if (in_hardirq())
 291                 regs = get_irq_regs();
 292         if (regs)
 293                 show_regs(regs);
 294         perf_event_print_debug();
 295 }
 296 static const struct sysrq_key_op sysrq_showregs_op = {
 297         .handler        = sysrq_handle_showregs,
 298         .help_msg       = "show-registers(p)",
 299         .action_msg     = "Show Regs",
 300         .enable_mask    = SYSRQ_ENABLE_DUMP,
 301 };
 302
 303 static void sysrq_handle_showstate(u8 key)
 304 {
 305         show_state();
 306         show_all_workqueues();
 307 }
 308 static const struct sysrq_key_op sysrq_showstate_op = {
 309         .handler        = sysrq_handle_showstate,
 310         .help_msg       = "show-task-states(t)",
 311         .action_msg     = "Show State",
 312         .enable_mask    = SYSRQ_ENABLE_DUMP,
 313 };
 314
 315 static void sysrq_handle_showstate_blocked(u8 key)
 316 {
 317         show_state_filter(TASK_UNINTERRUPTIBLE);
 318 }
 319 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
 320         .handler        = sysrq_handle_showstate_blocked,
 321         .help_msg       = "show-blocked-tasks(w)",
 322         .action_msg     = "Show Blocked State",
 323         .enable_mask    = SYSRQ_ENABLE_DUMP,
 324 };
 325
 326 #ifdef CONFIG_TRACING
 327 #include <linux/ftrace.h>
 328
 329 static void sysrq_ftrace_dump(u8 key)
 330 {
 331         ftrace_dump(DUMP_ALL);
 332 }
 333 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
 334         .handler        = sysrq_ftrace_dump,
 335         .help_msg       = "dump-ftrace-buffer(z)",
 336         .action_msg     = "Dump ftrace buffer",
 337         .enable_mask    = SYSRQ_ENABLE_DUMP,
 338 };
 339 #else
 340 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
 341 #endif
 342
 343 static void sysrq_handle_showmem(u8 key)
 344 {
 345         show_mem();
 346 }
 347 static const struct sysrq_key_op sysrq_showmem_op = {
 348         .handler        = sysrq_handle_showmem,
 349         .help_msg       = "show-memory-usage(m)",
 350         .action_msg     = "Show Memory",
 351         .enable_mask    = SYSRQ_ENABLE_DUMP,
 352 };
 353
 354 /*
 355  * Signal sysrq helper function.  Sends a signal to all user processes.
 356  */
 357 static void send_sig_all(int sig)
 358 {
 359         struct task_struct *p;
 360
 361         read_lock(&tasklist_lock);
 362         for_each_process(p) {
 363                 if (p->flags & PF_KTHREAD)
 364                         continue;
 365                 if (is_global_init(p))
 366                         continue;
 367
 368                 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
 369         }
 370         read_unlock(&tasklist_lock);
 371 }
 372
 373 static void sysrq_handle_term(u8 key)
 374 {
 375         send_sig_all(SIGTERM);
 376         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 377 }
 378 static const struct sysrq_key_op sysrq_term_op = {
 379         .handler        = sysrq_handle_term,
 380         .help_msg       = "terminate-all-tasks(e)",
 381         .action_msg     = "Terminate All Tasks",
 382         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 383 };
 384
 385 static void moom_callback(struct work_struct *ignored)
 386 {
 387         const gfp_t gfp_mask = GFP_KERNEL;
 388         struct oom_control oc = {
 389                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 390                 .nodemask = NULL,
 391                 .memcg = NULL,
 392                 .gfp_mask = gfp_mask,
 393                 .order = -1,
 394         };
 395
 396         mutex_lock(&oom_lock);
 397         if (!out_of_memory(&oc))
 398                 pr_info("OOM request ignored. No task eligible\n");
 399         mutex_unlock(&oom_lock);
 400 }
 401
 402 static DECLARE_WORK(moom_work, moom_callback);
 403
 404 static void sysrq_handle_moom(u8 key)
 405 {
 406         schedule_work(&moom_work);
 407 }
 408 static const struct sysrq_key_op sysrq_moom_op = {
 409         .handler        = sysrq_handle_moom,
 410         .help_msg       = "memory-full-oom-kill(f)",
 411         .action_msg     = "Manual OOM execution",
 412         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 413 };
 414
 415 #ifdef CONFIG_BLOCK
 416 static void sysrq_handle_thaw(u8 key)
 417 {
 418         emergency_thaw_all();
 419 }
 420 static const struct sysrq_key_op sysrq_thaw_op = {
 421         .handler        = sysrq_handle_thaw,
 422         .help_msg       = "thaw-filesystems(j)",
 423         .action_msg     = "Emergency Thaw of all frozen filesystems",
 424         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 425 };
 426 #else
 427 #define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL)
 428 #endif
 429
 430 static void sysrq_handle_kill(u8 key)
 431 {
 432         send_sig_all(SIGKILL);
 433         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 434 }
 435 static const struct sysrq_key_op sysrq_kill_op = {
 436         .handler        = sysrq_handle_kill,
 437         .help_msg       = "kill-all-tasks(i)",
 438         .action_msg     = "Kill All Tasks",
 439         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 440 };
 441
 442 static void sysrq_handle_unrt(u8 key)
 443 {
 444         normalize_rt_tasks();
 445 }
 446 static const struct sysrq_key_op sysrq_unrt_op = {
 447         .handler        = sysrq_handle_unrt,
 448         .help_msg       = "nice-all-RT-tasks(n)",
 449         .action_msg     = "Nice All RT Tasks",
 450         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 451 };
 452
 453 static void sysrq_handle_replay_logs(u8 key)
 454 {
 455         console_replay_all();
 456 }
 457 static struct sysrq_key_op sysrq_replay_logs_op = {
 458         .handler        = sysrq_handle_replay_logs,
 459         .help_msg       = "replay-kernel-logs(R)",
 460         .action_msg     = "Replay kernel logs on consoles",
 461         .enable_mask    = SYSRQ_ENABLE_DUMP,
 462 };
 463
 464 /* Key Operations table and lock */
 465 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 466
 467 static const struct sysrq_key_op *sysrq_key_table[62] = {
 468         &sysrq_loglevel_op,             /* 0 */
 469         &sysrq_loglevel_op,             /* 1 */
 470         &sysrq_loglevel_op,             /* 2 */
 471         &sysrq_loglevel_op,             /* 3 */
 472         &sysrq_loglevel_op,             /* 4 */
 473         &sysrq_loglevel_op,             /* 5 */
 474         &sysrq_loglevel_op,             /* 6 */
 475         &sysrq_loglevel_op,             /* 7 */
 476         &sysrq_loglevel_op,             /* 8 */
 477         &sysrq_loglevel_op,             /* 9 */
 478
 479         /*
 480          * a: Don't use for system provided sysrqs, it is handled specially on
 481          * sparc and will never arrive.
 482          */
 483         NULL,                           /* a */
 484         &sysrq_reboot_op,               /* b */
 485         &sysrq_crash_op,                /* c */
 486         &sysrq_showlocks_op,            /* d */
 487         &sysrq_term_op,                 /* e */
 488         &sysrq_moom_op,                 /* f */
 489         /* g: May be registered for the kernel debugger */
 490         NULL,                           /* g */
 491         NULL,                           /* h - reserved for help */
 492         &sysrq_kill_op,                 /* i */
 493         &sysrq_thaw_op,                 /* j */
 494         &sysrq_SAK_op,                  /* k */
 495         &sysrq_showallcpus_op,          /* l */
 496         &sysrq_showmem_op,              /* m */
 497         &sysrq_unrt_op,                 /* n */
 498         /* o: This will often be registered as 'Off' at init time */
 499         NULL,                           /* o */
 500         &sysrq_showregs_op,             /* p */
 501         &sysrq_show_timers_op,          /* q */
 502         &sysrq_unraw_op,                /* r */
 503         &sysrq_sync_op,                 /* s */
 504         &sysrq_showstate_op,            /* t */
 505         &sysrq_mountro_op,              /* u */
 506         /* v: May be registered for frame buffer console restore */
 507         NULL,                           /* v */
 508         &sysrq_showstate_blocked_op,    /* w */
 509         /* x: May be registered on mips for TLB dump */
 510         /* x: May be registered on ppc/powerpc for xmon */
 511         /* x: May be registered on sparc64 for global PMU dump */
 512         NULL,                           /* x */
 513         /* y: May be registered on sparc64 for global register dump */
 514         NULL,                           /* y */
 515         &sysrq_ftrace_dump_op,          /* z */
 516         NULL,                           /* A */
 517         NULL,                           /* B */
 518         NULL,                           /* C */
 519         NULL,                           /* D */
 520         NULL,                           /* E */
 521         NULL,                           /* F */
 522         NULL,                           /* G */
 523         NULL,                           /* H */
 524         NULL,                           /* I */
 525         NULL,                           /* J */
 526         NULL,                           /* K */
 527         NULL,                           /* L */
 528         NULL,                           /* M */
 529         NULL,                           /* N */
 530         NULL,                           /* O */
 531         NULL,                           /* P */
 532         NULL,                           /* Q */
 533         &sysrq_replay_logs_op,          /* R */
 534         NULL,                           /* S */
 535         NULL,                           /* T */
 536         NULL,                           /* U */
 537         NULL,                           /* V */
 538         NULL,                           /* W */
 539         NULL,                           /* X */
 540         NULL,                           /* Y */
 541         NULL,                           /* Z */
 542 };
 543
 544 /* key2index calculation, -1 on invalid index */
 545 static int sysrq_key_table_key2index(u8 key)
 546 {
 547         switch (key) {
 548         case '0' ... '9':
 549                 return key - '0';
 550         case 'a' ... 'z':
 551                 return key - 'a' + 10;
 552         case 'A' ... 'Z':
 553                 return key - 'A' + 10 + 26;
 554         default:
 555                 return -1;
 556         }
 557 }
 558
 559 /*
 560  * get and put functions for the table, exposed to modules.
 561  */
 562 static const struct sysrq_key_op *__sysrq_get_key_op(u8 key)
 563 {
 564         const struct sysrq_key_op *op_p = NULL;
 565         int i;
 566
 567         i = sysrq_key_table_key2index(key);
 568         if (i != -1)
 569                 op_p = sysrq_key_table[i];
 570
 571         return op_p;
 572 }
 573
 574 static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p)
 575 {
 576         int i = sysrq_key_table_key2index(key);
 577
 578         if (i != -1)
 579                 sysrq_key_table[i] = op_p;
 580 }
 581
 582 void __handle_sysrq(u8 key, bool check_mask)
 583 {
 584         const struct sysrq_key_op *op_p;
 585         int orig_log_level;
 586         int orig_suppress_printk;
 587         int i;
 588
 589         orig_suppress_printk = suppress_printk;
 590         suppress_printk = 0;
 591
 592         rcu_sysrq_start();
 593         rcu_read_lock();
 594         /*
 595          * Raise the apparent loglevel to maximum so that the sysrq header
 596          * is shown to provide the user with positive feedback.  We do not
 597          * simply emit this at KERN_EMERG as that would change message
 598          * routing in the consumers of /proc/kmsg.
 599          */
 600         orig_log_level = console_loglevel;
 601         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 602
 603         op_p = __sysrq_get_key_op(key);
 604         if (op_p) {
 605                 /*
 606                  * Should we check for enabled operations (/proc/sysrq-trigger
 607                  * should not) and is the invoked operation enabled?
 608                  */
 609                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 610                         pr_info("%s\n", op_p->action_msg);
 611                         console_loglevel = orig_log_level;
 612                         op_p->handler(key);
 613                 } else {
 614                         pr_info("This sysrq operation is disabled.\n");
 615                         console_loglevel = orig_log_level;
 616                 }
 617         } else {
 618                 pr_info("HELP : ");
 619                 /* Only print the help msg once per handler */
 620                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 621                         if (sysrq_key_table[i]) {
 622                                 int j;
 623
 624                                 for (j = 0; sysrq_key_table[i] !=
 625                                                 sysrq_key_table[j]; j++)
 626                                         ;
 627                                 if (j != i)
 628                                         continue;
 629                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 630                         }
 631                 }
 632                 pr_cont("\n");
 633                 console_loglevel = orig_log_level;
 634         }
 635         rcu_read_unlock();
 636         rcu_sysrq_end();
 637
 638         suppress_printk = orig_suppress_printk;
 639 }
 640
 641 void handle_sysrq(u8 key)
 642 {
 643         if (sysrq_on())
 644                 __handle_sysrq(key, true);
 645 }
 646 EXPORT_SYMBOL(handle_sysrq);
 647
 648 #ifdef CONFIG_INPUT
 649 static int sysrq_reset_downtime_ms;
 650
 651 /* Simple translation table for the SysRq keys */
 652 static const unsigned char sysrq_xlate[KEY_CNT] =
 653         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 654         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 655         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 656         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 657         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 658         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 659         "\r\000/";                                      /* 0x60 - 0x6f */
 660
 661 struct sysrq_state {
 662         struct input_handle handle;
 663         struct work_struct reinject_work;
 664         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 665         unsigned int alt;
 666         unsigned int alt_use;
 667         unsigned int shift;
 668         unsigned int shift_use;
 669         bool active;
 670         bool need_reinject;
 671         bool reinjecting;
 672
 673         /* reset sequence handling */
 674         bool reset_canceled;
 675         bool reset_requested;
 676         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 677         int reset_seq_len;
 678         int reset_seq_cnt;
 679         int reset_seq_version;
 680         struct timer_list keyreset_timer;
 681 };
 682
 683 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 684 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 685 static unsigned int sysrq_reset_seq_len;
 686 static unsigned int sysrq_reset_seq_version = 1;
 687
 688 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 689 {
 690         int i;
 691         unsigned short key;
 692
 693         state->reset_seq_cnt = 0;
 694
 695         for (i = 0; i < sysrq_reset_seq_len; i++) {
 696                 key = sysrq_reset_seq[i];
 697
 698                 if (key == KEY_RESERVED || key > KEY_MAX)
 699                         break;
 700
 701                 __set_bit(key, state->reset_keybit);
 702                 state->reset_seq_len++;
 703
 704                 if (test_bit(key, state->key_down))
 705                         state->reset_seq_cnt++;
 706         }
 707
 708         /* Disable reset until old keys are not released */
 709         state->reset_canceled = state->reset_seq_cnt != 0;
 710
 711         state->reset_seq_version = sysrq_reset_seq_version;
 712 }
 713
 714 static void sysrq_do_reset(struct timer_list *t)
 715 {
 716         struct sysrq_state *state = from_timer(state, t, keyreset_timer);
 717
 718         state->reset_requested = true;
 719
 720         orderly_reboot();
 721 }
 722
 723 static void sysrq_handle_reset_request(struct sysrq_state *state)
 724 {
 725         if (state->reset_requested)
 726                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 727
 728         if (sysrq_reset_downtime_ms)
 729                 mod_timer(&state->keyreset_timer,
 730                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 731         else
 732                 sysrq_do_reset(&state->keyreset_timer);
 733 }
 734
 735 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 736                                         unsigned int code, int value)
 737 {
 738         if (!test_bit(code, state->reset_keybit)) {
 739                 /*
 740                  * Pressing any key _not_ in reset sequence cancels
 741                  * the reset sequence.  Also cancelling the timer in
 742                  * case additional keys were pressed after a reset
 743                  * has been requested.
 744                  */
 745                 if (value && state->reset_seq_cnt) {
 746                         state->reset_canceled = true;
 747                         del_timer(&state->keyreset_timer);
 748                 }
 749         } else if (value == 0) {
 750                 /*
 751                  * Key release - all keys in the reset sequence need
 752                  * to be pressed and held for the reset timeout
 753                  * to hold.
 754                  */
 755                 del_timer(&state->keyreset_timer);
 756
 757                 if (--state->reset_seq_cnt == 0)
 758                         state->reset_canceled = false;
 759         } else if (value == 1) {
 760                 /* key press, not autorepeat */
 761                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 762                     !state->reset_canceled) {
 763                         sysrq_handle_reset_request(state);
 764                 }
 765         }
 766 }
 767
 768 #ifdef CONFIG_OF
 769 static void sysrq_of_get_keyreset_config(void)
 770 {
 771         u32 key;
 772         struct device_node *np;
 773         struct property *prop;
 774         const __be32 *p;
 775
 776         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 777         if (!np) {
 778                 pr_debug("No sysrq node found");
 779                 return;
 780         }
 781
 782         /* Reset in case a __weak definition was present */
 783         sysrq_reset_seq_len = 0;
 784
 785         of_property_for_each_u32(np, "keyset", prop, p, key) {
 786                 if (key == KEY_RESERVED || key > KEY_MAX ||
 787                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 788                         break;
 789
 790                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 791         }
 792
 793         /* Get reset timeout if any. */
 794         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 795
 796         of_node_put(np);
 797 }
 798 #else
 799 static void sysrq_of_get_keyreset_config(void)
 800 {
 801 }
 802 #endif
 803
 804 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 805 {
 806         struct sysrq_state *sysrq =
 807                         container_of(work, struct sysrq_state, reinject_work);
 808         struct input_handle *handle = &sysrq->handle;
 809         unsigned int alt_code = sysrq->alt_use;
 810
 811         if (sysrq->need_reinject) {
 812                 /* we do not want the assignment to be reordered */
 813                 sysrq->reinjecting = true;
 814                 mb();
 815
 816                 /* Simulate press and release of Alt + SysRq */
 817                 input_inject_event(handle, EV_KEY, alt_code, 1);
 818                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 819                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 820
 821                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 822                 input_inject_event(handle, EV_KEY, alt_code, 0);
 823                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 824
 825                 mb();
 826                 sysrq->reinjecting = false;
 827         }
 828 }
 829
 830 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 831                                   unsigned int code, int value)
 832 {
 833         bool was_active = sysrq->active;
 834         bool suppress;
 835
 836         switch (code) {
 837
 838         case KEY_LEFTALT:
 839         case KEY_RIGHTALT:
 840                 if (!value) {
 841                         /* One of ALTs is being released */
 842                         if (sysrq->active && code == sysrq->alt_use)
 843                                 sysrq->active = false;
 844
 845                         sysrq->alt = KEY_RESERVED;
 846
 847                 } else if (value != 2) {
 848                         sysrq->alt = code;
 849                         sysrq->need_reinject = false;
 850                 }
 851                 break;
 852
 853         case KEY_LEFTSHIFT:
 854         case KEY_RIGHTSHIFT:
 855                 if (!value)
 856                         sysrq->shift = KEY_RESERVED;
 857                 else if (value != 2)
 858                         sysrq->shift = code;
 859                 if (sysrq->active)
 860                         sysrq->shift_use = sysrq->shift;
 861                 break;
 862
 863         case KEY_SYSRQ:
 864                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 865                         sysrq->active = true;
 866                         sysrq->alt_use = sysrq->alt;
 867                         /* either RESERVED (for released) or actual code */
 868                         sysrq->shift_use = sysrq->shift;
 869                         /*
 870                          * If nothing else will be pressed we'll need
 871                          * to re-inject Alt-SysRq keysroke.
 872                          */
 873                         sysrq->need_reinject = true;
 874                 }
 875
 876                 /*
 877                  * Pretend that sysrq was never pressed at all. This
 878                  * is needed to properly handle KGDB which will try
 879                  * to release all keys after exiting debugger. If we
 880                  * do not clear key bit it KGDB will end up sending
 881                  * release events for Alt and SysRq, potentially
 882                  * triggering print screen function.
 883                  */
 884                 if (sysrq->active)
 885                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 886
 887                 break;
 888
 889         default:
 890                 if (sysrq->active && value && value != 2) {
 891                         unsigned char c = sysrq_xlate[code];
 892
 893                         sysrq->need_reinject = false;
 894                         if (sysrq->shift_use != KEY_RESERVED)
 895                                 c = toupper(c);
 896                         __handle_sysrq(c, true);
 897                 }
 898                 break;
 899         }
 900
 901         suppress = sysrq->active;
 902
 903         if (!sysrq->active) {
 904
 905                 /*
 906                  * See if reset sequence has changed since the last time.
 907                  */
 908                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 909                         sysrq_parse_reset_sequence(sysrq);
 910
 911                 /*
 912                  * If we are not suppressing key presses keep track of
 913                  * keyboard state so we can release keys that have been
 914                  * pressed before entering SysRq mode.
 915                  */
 916                 if (value)
 917                         set_bit(code, sysrq->key_down);
 918                 else
 919                         clear_bit(code, sysrq->key_down);
 920
 921                 if (was_active)
 922                         schedule_work(&sysrq->reinject_work);
 923
 924                 /* Check for reset sequence */
 925                 sysrq_detect_reset_sequence(sysrq, code, value);
 926
 927         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 928                 /*
 929                  * Pass on release events for keys that was pressed before
 930                  * entering SysRq mode.
 931                  */
 932                 suppress = false;
 933         }
 934
 935         return suppress;
 936 }
 937
 938 static bool sysrq_filter(struct input_handle *handle,
 939                          unsigned int type, unsigned int code, int value)
 940 {
 941         struct sysrq_state *sysrq = handle->private;
 942         bool suppress;
 943
 944         /*
 945          * Do not filter anything if we are in the process of re-injecting
 946          * Alt+SysRq combination.
 947          */
 948         if (sysrq->reinjecting)
 949                 return false;
 950
 951         switch (type) {
 952
 953         case EV_SYN:
 954                 suppress = false;
 955                 break;
 956
 957         case EV_KEY:
 958                 suppress = sysrq_handle_keypress(sysrq, code, value);
 959                 break;
 960
 961         default:
 962                 suppress = sysrq->active;
 963                 break;
 964         }
 965
 966         return suppress;
 967 }
 968
 969 static int sysrq_connect(struct input_handler *handler,
 970                          struct input_dev *dev,
 971                          const struct input_device_id *id)
 972 {
 973         struct sysrq_state *sysrq;
 974         int error;
 975
 976         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 977         if (!sysrq)
 978                 return -ENOMEM;
 979
 980         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 981
 982         sysrq->handle.dev = dev;
 983         sysrq->handle.handler = handler;
 984         sysrq->handle.name = "sysrq";
 985         sysrq->handle.private = sysrq;
 986         timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 987
 988         error = input_register_handle(&sysrq->handle);
 989         if (error) {
 990                 pr_err("Failed to register input sysrq handler, error %d\n",
 991                         error);
 992                 goto err_free;
 993         }
 994
 995         error = input_open_device(&sysrq->handle);
 996         if (error) {
 997                 pr_err("Failed to open input device, error %d\n", error);
 998                 goto err_unregister;
 999         }
1000
1001         return 0;
1002
1003  err_unregister:
1004         input_unregister_handle(&sysrq->handle);
1005  err_free:
1006         kfree(sysrq);
1007         return error;
1008 }
1009
1010 static void sysrq_disconnect(struct input_handle *handle)
1011 {
1012         struct sysrq_state *sysrq = handle->private;
1013
1014         input_close_device(handle);
1015         cancel_work_sync(&sysrq->reinject_work);
1016         timer_shutdown_sync(&sysrq->keyreset_timer);
1017         input_unregister_handle(handle);
1018         kfree(sysrq);
1019 }
1020
1021 /*
1022  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1023  * keyboards have SysRq key predefined and so user may add it to keymap
1024  * later, but we expect all such keyboards to have left alt.
1025  */
1026 static const struct input_device_id sysrq_ids[] = {
1027         {
1028                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1029                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
1030                 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1031                 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1032         },
1033         { },
1034 };
1035
1036 static struct input_handler sysrq_handler = {
1037         .filter         = sysrq_filter,
1038         .connect        = sysrq_connect,
1039         .disconnect     = sysrq_disconnect,
1040         .name           = "sysrq",
1041         .id_table       = sysrq_ids,
1042 };
1043
1044 static inline void sysrq_register_handler(void)
1045 {
1046         int error;
1047
1048         sysrq_of_get_keyreset_config();
1049
1050         error = input_register_handler(&sysrq_handler);
1051         if (error)
1052                 pr_err("Failed to register input handler, error %d", error);
1053 }
1054
1055 static inline void sysrq_unregister_handler(void)
1056 {
1057         input_unregister_handler(&sysrq_handler);
1058 }
1059
1060 static int sysrq_reset_seq_param_set(const char *buffer,
1061                                      const struct kernel_param *kp)
1062 {
1063         unsigned long val;
1064         int error;
1065
1066         error = kstrtoul(buffer, 0, &val);
1067         if (error < 0)
1068                 return error;
1069
1070         if (val > KEY_MAX)
1071                 return -EINVAL;
1072
1073         *((unsigned short *)kp->arg) = val;
1074         sysrq_reset_seq_version++;
1075
1076         return 0;
1077 }
1078
1079 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1080         .get    = param_get_ushort,
1081         .set    = sysrq_reset_seq_param_set,
1082 };
1083
1084 #define param_check_sysrq_reset_seq(name, p)    \
1085         __param_check(name, p, unsigned short)
1086
1087 /*
1088  * not really modular, but the easiest way to keep compat with existing
1089  * bootargs behaviour is to continue using module_param here.
1090  */
1091 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1092                          &sysrq_reset_seq_len, 0644);
1093
1094 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1095
1096 #else
1097
1098 static inline void sysrq_register_handler(void)
1099 {
1100 }
1101
1102 static inline void sysrq_unregister_handler(void)
1103 {
1104 }
1105
1106 #endif /* CONFIG_INPUT */
1107
1108 int sysrq_toggle_support(int enable_mask)
1109 {
1110         bool was_enabled = sysrq_on();
1111
1112         sysrq_enabled = enable_mask;
1113
1114         if (was_enabled != sysrq_on()) {
1115                 if (sysrq_on())
1116                         sysrq_register_handler();
1117                 else
1118                         sysrq_unregister_handler();
1119         }
1120
1121         return 0;
1122 }
1123 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1124
1125 static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p,
1126                                 const struct sysrq_key_op *remove_op_p)
1127 {
1128         int retval;
1129
1130         spin_lock(&sysrq_key_table_lock);
1131         if (__sysrq_get_key_op(key) == remove_op_p) {
1132                 __sysrq_put_key_op(key, insert_op_p);
1133                 retval = 0;
1134         } else {
1135                 retval = -1;
1136         }
1137         spin_unlock(&sysrq_key_table_lock);
1138
1139         /*
1140          * A concurrent __handle_sysrq either got the old op or the new op.
1141          * Wait for it to go away before returning, so the code for an old
1142          * op is not freed (eg. on module unload) while it is in use.
1143          */
1144         synchronize_rcu();
1145
1146         return retval;
1147 }
1148
1149 int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1150 {
1151         return __sysrq_swap_key_ops(key, op_p, NULL);
1152 }
1153 EXPORT_SYMBOL(register_sysrq_key);
1154
1155 int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1156 {
1157         return __sysrq_swap_key_ops(key, NULL, op_p);
1158 }
1159 EXPORT_SYMBOL(unregister_sysrq_key);
1160
1161 #ifdef CONFIG_PROC_FS
1162 /*
1163  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1164  * Normally, only the first character written is processed.
1165  * However, if the first character is an underscore,
1166  * all characters are processed.
1167  */
1168 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1169                                    size_t count, loff_t *ppos)
1170 {
1171         bool bulk = false;
1172         size_t i;
1173
1174         for (i = 0; i < count; i++) {
1175                 char c;
1176
1177                 if (get_user(c, buf + i))
1178                         return -EFAULT;
1179
1180                 if (c == '_')
1181                         bulk = true;
1182                 else
1183                         __handle_sysrq(c, false);
1184
1185                 if (!bulk)
1186                         break;
1187         }
1188
1189         return count;
1190 }
1191
1192 static const struct proc_ops sysrq_trigger_proc_ops = {
1193         .proc_write     = write_sysrq_trigger,
1194         .proc_lseek     = noop_llseek,
1195 };
1196
1197 static void sysrq_init_procfs(void)
1198 {
1199         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1200                          &sysrq_trigger_proc_ops))
1201                 pr_err("Failed to register proc interface\n");
1202 }
1203
1204 #else
1205
1206 static inline void sysrq_init_procfs(void)
1207 {
1208 }
1209
1210 #endif /* CONFIG_PROC_FS */
1211
1212 static int __init sysrq_init(void)
1213 {
1214         sysrq_init_procfs();
1215
1216         if (sysrq_on())
1217                 sysrq_register_handler();
1218
1219         return 0;
1220 }
1221 device_initcall(sysrq_init);