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