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