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