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