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