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
  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(first_online_node, GFP_KERNEL), GFP_KERNEL,
 351                       0, NULL, true);
 352 }
 353
 354 static DECLARE_WORK(moom_work, moom_callback);
 355
 356 static void sysrq_handle_moom(int key)
 357 {
 358         schedule_work(&moom_work);
 359 }
 360 static struct sysrq_key_op sysrq_moom_op = {
 361         .handler        = sysrq_handle_moom,
 362         .help_msg       = "memory-full-oom-kill(F)",
 363         .action_msg     = "Manual OOM execution",
 364         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 365 };
 366
 367 #ifdef CONFIG_BLOCK
 368 static void sysrq_handle_thaw(int key)
 369 {
 370         emergency_thaw_all();
 371 }
 372 static struct sysrq_key_op sysrq_thaw_op = {
 373         .handler        = sysrq_handle_thaw,
 374         .help_msg       = "thaw-filesystems(J)",
 375         .action_msg     = "Emergency Thaw of all frozen filesystems",
 376         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 377 };
 378 #endif
 379
 380 static void sysrq_handle_kill(int key)
 381 {
 382         send_sig_all(SIGKILL);
 383         console_loglevel = 8;
 384 }
 385 static struct sysrq_key_op sysrq_kill_op = {
 386         .handler        = sysrq_handle_kill,
 387         .help_msg       = "kill-all-tasks(I)",
 388         .action_msg     = "Kill All Tasks",
 389         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 390 };
 391
 392 static void sysrq_handle_unrt(int key)
 393 {
 394         normalize_rt_tasks();
 395 }
 396 static struct sysrq_key_op sysrq_unrt_op = {
 397         .handler        = sysrq_handle_unrt,
 398         .help_msg       = "nice-all-RT-tasks(N)",
 399         .action_msg     = "Nice All RT Tasks",
 400         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 401 };
 402
 403 /* Key Operations table and lock */
 404 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 405
 406 static struct sysrq_key_op *sysrq_key_table[36] = {
 407         &sysrq_loglevel_op,             /* 0 */
 408         &sysrq_loglevel_op,             /* 1 */
 409         &sysrq_loglevel_op,             /* 2 */
 410         &sysrq_loglevel_op,             /* 3 */
 411         &sysrq_loglevel_op,             /* 4 */
 412         &sysrq_loglevel_op,             /* 5 */
 413         &sysrq_loglevel_op,             /* 6 */
 414         &sysrq_loglevel_op,             /* 7 */
 415         &sysrq_loglevel_op,             /* 8 */
 416         &sysrq_loglevel_op,             /* 9 */
 417
 418         /*
 419          * a: Don't use for system provided sysrqs, it is handled specially on
 420          * sparc and will never arrive.
 421          */
 422         NULL,                           /* a */
 423         &sysrq_reboot_op,               /* b */
 424         &sysrq_crash_op,                /* c & ibm_emac driver debug */
 425         &sysrq_showlocks_op,            /* d */
 426         &sysrq_term_op,                 /* e */
 427         &sysrq_moom_op,                 /* f */
 428         /* g: May be registered for the kernel debugger */
 429         NULL,                           /* g */
 430         NULL,                           /* h - reserved for help */
 431         &sysrq_kill_op,                 /* i */
 432 #ifdef CONFIG_BLOCK
 433         &sysrq_thaw_op,                 /* j */
 434 #else
 435         NULL,                           /* j */
 436 #endif
 437         &sysrq_SAK_op,                  /* k */
 438 #ifdef CONFIG_SMP
 439         &sysrq_showallcpus_op,          /* l */
 440 #else
 441         NULL,                           /* l */
 442 #endif
 443         &sysrq_showmem_op,              /* m */
 444         &sysrq_unrt_op,                 /* n */
 445         /* o: This will often be registered as 'Off' at init time */
 446         NULL,                           /* o */
 447         &sysrq_showregs_op,             /* p */
 448         &sysrq_show_timers_op,          /* q */
 449         &sysrq_unraw_op,                /* r */
 450         &sysrq_sync_op,                 /* s */
 451         &sysrq_showstate_op,            /* t */
 452         &sysrq_mountro_op,              /* u */
 453         /* v: May be registered for frame buffer console restore */
 454         NULL,                           /* v */
 455         &sysrq_showstate_blocked_op,    /* w */
 456         /* x: May be registered on ppc/powerpc for xmon */
 457         /* x: May be registered on sparc64 for global PMU dump */
 458         NULL,                           /* x */
 459         /* y: May be registered on sparc64 for global register dump */
 460         NULL,                           /* y */
 461         &sysrq_ftrace_dump_op,          /* z */
 462 };
 463
 464 /* key2index calculation, -1 on invalid index */
 465 static int sysrq_key_table_key2index(int key)
 466 {
 467         int retval;
 468
 469         if ((key >= '0') && (key <= '9'))
 470                 retval = key - '0';
 471         else if ((key >= 'a') && (key <= 'z'))
 472                 retval = key + 10 - 'a';
 473         else
 474                 retval = -1;
 475         return retval;
 476 }
 477
 478 /*
 479  * get and put functions for the table, exposed to modules.
 480  */
 481 struct sysrq_key_op *__sysrq_get_key_op(int key)
 482 {
 483         struct sysrq_key_op *op_p = NULL;
 484         int i;
 485
 486         i = sysrq_key_table_key2index(key);
 487         if (i != -1)
 488                 op_p = sysrq_key_table[i];
 489
 490         return op_p;
 491 }
 492
 493 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 494 {
 495         int i = sysrq_key_table_key2index(key);
 496
 497         if (i != -1)
 498                 sysrq_key_table[i] = op_p;
 499 }
 500
 501 void __handle_sysrq(int key, bool check_mask)
 502 {
 503         struct sysrq_key_op *op_p;
 504         int orig_log_level;
 505         int i;
 506         unsigned long flags;
 507
 508         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 509         /*
 510          * Raise the apparent loglevel to maximum so that the sysrq header
 511          * is shown to provide the user with positive feedback.  We do not
 512          * simply emit this at KERN_EMERG as that would change message
 513          * routing in the consumers of /proc/kmsg.
 514          */
 515         orig_log_level = console_loglevel;
 516         console_loglevel = 7;
 517         printk(KERN_INFO "SysRq : ");
 518
 519         op_p = __sysrq_get_key_op(key);
 520         if (op_p) {
 521                 /*
 522                  * Should we check for enabled operations (/proc/sysrq-trigger
 523                  * should not) and is the invoked operation enabled?
 524                  */
 525                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 526                         printk("%s\n", op_p->action_msg);
 527                         console_loglevel = orig_log_level;
 528                         op_p->handler(key);
 529                 } else {
 530                         printk("This sysrq operation is disabled.\n");
 531                 }
 532         } else {
 533                 printk("HELP : ");
 534                 /* Only print the help msg once per handler */
 535                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 536                         if (sysrq_key_table[i]) {
 537                                 int j;
 538
 539                                 for (j = 0; sysrq_key_table[i] !=
 540                                                 sysrq_key_table[j]; j++)
 541                                         ;
 542                                 if (j != i)
 543                                         continue;
 544                                 printk("%s ", sysrq_key_table[i]->help_msg);
 545                         }
 546                 }
 547                 printk("\n");
 548                 console_loglevel = orig_log_level;
 549         }
 550         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 551 }
 552
 553 void handle_sysrq(int key)
 554 {
 555         if (sysrq_on())
 556                 __handle_sysrq(key, true);
 557 }
 558 EXPORT_SYMBOL(handle_sysrq);
 559
 560 #ifdef CONFIG_INPUT
 561
 562 /* Simple translation table for the SysRq keys */
 563 static const unsigned char sysrq_xlate[KEY_CNT] =
 564         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 565         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 566         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 567         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 568         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 569         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 570         "\r\000/";                                      /* 0x60 - 0x6f */
 571
 572 struct sysrq_state {
 573         struct input_handle handle;
 574         struct work_struct reinject_work;
 575         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 576         unsigned int alt;
 577         unsigned int alt_use;
 578         bool active;
 579         bool need_reinject;
 580         bool reinjecting;
 581 };
 582
 583 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 584 {
 585         struct sysrq_state *sysrq =
 586                         container_of(work, struct sysrq_state, reinject_work);
 587         struct input_handle *handle = &sysrq->handle;
 588         unsigned int alt_code = sysrq->alt_use;
 589
 590         if (sysrq->need_reinject) {
 591                 /* we do not want the assignment to be reordered */
 592                 sysrq->reinjecting = true;
 593                 mb();
 594
 595                 /* Simulate press and release of Alt + SysRq */
 596                 input_inject_event(handle, EV_KEY, alt_code, 1);
 597                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 598                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 599
 600                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 601                 input_inject_event(handle, EV_KEY, alt_code, 0);
 602                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 603
 604                 mb();
 605                 sysrq->reinjecting = false;
 606         }
 607 }
 608
 609 static bool sysrq_filter(struct input_handle *handle,
 610                          unsigned int type, unsigned int code, int value)
 611 {
 612         struct sysrq_state *sysrq = handle->private;
 613         bool was_active = sysrq->active;
 614         bool suppress;
 615
 616         /*
 617          * Do not filter anything if we are in the process of re-injecting
 618          * Alt+SysRq combination.
 619          */
 620         if (sysrq->reinjecting)
 621                 return false;
 622
 623         switch (type) {
 624
 625         case EV_SYN:
 626                 suppress = false;
 627                 break;
 628
 629         case EV_KEY:
 630                 switch (code) {
 631
 632                 case KEY_LEFTALT:
 633                 case KEY_RIGHTALT:
 634                         if (!value) {
 635                                 /* One of ALTs is being released */
 636                                 if (sysrq->active && code == sysrq->alt_use)
 637                                         sysrq->active = false;
 638
 639                                 sysrq->alt = KEY_RESERVED;
 640
 641                         } else if (value != 2) {
 642                                 sysrq->alt = code;
 643                                 sysrq->need_reinject = false;
 644                         }
 645                         break;
 646
 647                 case KEY_SYSRQ:
 648                         if (value == 1 && sysrq->alt != KEY_RESERVED) {
 649                                 sysrq->active = true;
 650                                 sysrq->alt_use = sysrq->alt;
 651                                 /*
 652                                  * If nothing else will be pressed we'll need
 653                                  * to re-inject Alt-SysRq keysroke.
 654                                  */
 655                                 sysrq->need_reinject = true;
 656                         }
 657
 658                         /*
 659                          * Pretend that sysrq was never pressed at all. This
 660                          * is needed to properly handle KGDB which will try
 661                          * to release all keys after exiting debugger. If we
 662                          * do not clear key bit it KGDB will end up sending
 663                          * release events for Alt and SysRq, potentially
 664                          * triggering print screen function.
 665                          */
 666                         if (sysrq->active)
 667                                 clear_bit(KEY_SYSRQ, handle->dev->key);
 668
 669                         break;
 670
 671                 default:
 672                         if (sysrq->active && value && value != 2) {
 673                                 sysrq->need_reinject = false;
 674                                 __handle_sysrq(sysrq_xlate[code], true);
 675                         }
 676                         break;
 677                 }
 678
 679                 suppress = sysrq->active;
 680
 681                 if (!sysrq->active) {
 682                         /*
 683                          * If we are not suppressing key presses keep track of
 684                          * keyboard state so we can release keys that have been
 685                          * pressed before entering SysRq mode.
 686                          */
 687                         if (value)
 688                                 set_bit(code, sysrq->key_down);
 689                         else
 690                                 clear_bit(code, sysrq->key_down);
 691
 692                         if (was_active)
 693                                 schedule_work(&sysrq->reinject_work);
 694
 695                 } else if (value == 0 &&
 696                            test_and_clear_bit(code, sysrq->key_down)) {
 697                         /*
 698                          * Pass on release events for keys that was pressed before
 699                          * entering SysRq mode.
 700                          */
 701                         suppress = false;
 702                 }
 703                 break;
 704
 705         default:
 706                 suppress = sysrq->active;
 707                 break;
 708         }
 709
 710         return suppress;
 711 }
 712
 713 static int sysrq_connect(struct input_handler *handler,
 714                          struct input_dev *dev,
 715                          const struct input_device_id *id)
 716 {
 717         struct sysrq_state *sysrq;
 718         int error;
 719
 720         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 721         if (!sysrq)
 722                 return -ENOMEM;
 723
 724         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 725
 726         sysrq->handle.dev = dev;
 727         sysrq->handle.handler = handler;
 728         sysrq->handle.name = "sysrq";
 729         sysrq->handle.private = sysrq;
 730
 731         error = input_register_handle(&sysrq->handle);
 732         if (error) {
 733                 pr_err("Failed to register input sysrq handler, error %d\n",
 734                         error);
 735                 goto err_free;
 736         }
 737
 738         error = input_open_device(&sysrq->handle);
 739         if (error) {
 740                 pr_err("Failed to open input device, error %d\n", error);
 741                 goto err_unregister;
 742         }
 743
 744         return 0;
 745
 746  err_unregister:
 747         input_unregister_handle(&sysrq->handle);
 748  err_free:
 749         kfree(sysrq);
 750         return error;
 751 }
 752
 753 static void sysrq_disconnect(struct input_handle *handle)
 754 {
 755         struct sysrq_state *sysrq = handle->private;
 756
 757         input_close_device(handle);
 758         cancel_work_sync(&sysrq->reinject_work);
 759         input_unregister_handle(handle);
 760         kfree(sysrq);
 761 }
 762
 763 /*
 764  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 765  * keyboards have SysRq key predefined and so user may add it to keymap
 766  * later, but we expect all such keyboards to have left alt.
 767  */
 768 static const struct input_device_id sysrq_ids[] = {
 769         {
 770                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 771                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 772                 .evbit = { BIT_MASK(EV_KEY) },
 773                 .keybit = { BIT_MASK(KEY_LEFTALT) },
 774         },
 775         { },
 776 };
 777
 778 static struct input_handler sysrq_handler = {
 779         .filter         = sysrq_filter,
 780         .connect        = sysrq_connect,
 781         .disconnect     = sysrq_disconnect,
 782         .name           = "sysrq",
 783         .id_table       = sysrq_ids,
 784 };
 785
 786 static bool sysrq_handler_registered;
 787
 788 static inline void sysrq_register_handler(void)
 789 {
 790         int error;
 791
 792         error = input_register_handler(&sysrq_handler);
 793         if (error)
 794                 pr_err("Failed to register input handler, error %d", error);
 795         else
 796                 sysrq_handler_registered = true;
 797 }
 798
 799 static inline void sysrq_unregister_handler(void)
 800 {
 801         if (sysrq_handler_registered) {
 802                 input_unregister_handler(&sysrq_handler);
 803                 sysrq_handler_registered = false;
 804         }
 805 }
 806
 807 #else
 808
 809 static inline void sysrq_register_handler(void)
 810 {
 811 }
 812
 813 static inline void sysrq_unregister_handler(void)
 814 {
 815 }
 816
 817 #endif /* CONFIG_INPUT */
 818
 819 int sysrq_toggle_support(int enable_mask)
 820 {
 821         bool was_enabled = sysrq_on();
 822
 823         sysrq_enabled = enable_mask;
 824
 825         if (was_enabled != sysrq_on()) {
 826                 if (sysrq_on())
 827                         sysrq_register_handler();
 828                 else
 829                         sysrq_unregister_handler();
 830         }
 831
 832         return 0;
 833 }
 834
 835 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
 836                                 struct sysrq_key_op *remove_op_p)
 837 {
 838         int retval;
 839         unsigned long flags;
 840
 841         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 842         if (__sysrq_get_key_op(key) == remove_op_p) {
 843                 __sysrq_put_key_op(key, insert_op_p);
 844                 retval = 0;
 845         } else {
 846                 retval = -1;
 847         }
 848         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 849         return retval;
 850 }
 851
 852 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
 853 {
 854         return __sysrq_swap_key_ops(key, op_p, NULL);
 855 }
 856 EXPORT_SYMBOL(register_sysrq_key);
 857
 858 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
 859 {
 860         return __sysrq_swap_key_ops(key, NULL, op_p);
 861 }
 862 EXPORT_SYMBOL(unregister_sysrq_key);
 863
 864 #ifdef CONFIG_PROC_FS
 865 /*
 866  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
 867  */
 868 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
 869                                    size_t count, loff_t *ppos)
 870 {
 871         if (count) {
 872                 char c;
 873
 874                 if (get_user(c, buf))
 875                         return -EFAULT;
 876                 __handle_sysrq(c, false);
 877         }
 878
 879         return count;
 880 }
 881
 882 static const struct file_operations proc_sysrq_trigger_operations = {
 883         .write          = write_sysrq_trigger,
 884         .llseek         = noop_llseek,
 885 };
 886
 887 static void sysrq_init_procfs(void)
 888 {
 889         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
 890                          &proc_sysrq_trigger_operations))
 891                 pr_err("Failed to register proc interface\n");
 892 }
 893
 894 #else
 895
 896 static inline void sysrq_init_procfs(void)
 897 {
 898 }
 899
 900 #endif /* CONFIG_PROC_FS */
 901
 902 static int __init sysrq_init(void)
 903 {
 904         sysrq_init_procfs();
 905
 906         if (sysrq_on())
 907                 sysrq_register_handler();
 908
 909         return 0;
 910 }
 911 module_init(sysrq_init);