drivers/tty/sysrq.c

   1 /*
   2  *      Linux Magic System Request Key Hacks
   3  *
   4  *      (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   5  *      based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
   6  *
   7  *      (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
   8  *      overhauled to use key registration
   9  *      based upon discusions in irc://irc.openprojects.net/#kernelnewbies
  10  *
  11  *      Copyright (c) 2010 Dmitry Torokhov
  12  *      Input handler conversion
  13  */
  14
  15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  16
  17 #include <linux/sched.h>
  18 #include <linux/sched/rt.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/mm.h>
  21 #include <linux/fs.h>
  22 #include <linux/mount.h>
  23 #include <linux/kdev_t.h>
  24 #include <linux/major.h>
  25 #include <linux/reboot.h>
  26 #include <linux/sysrq.h>
  27 #include <linux/kbd_kern.h>
  28 #include <linux/proc_fs.h>
  29 #include <linux/nmi.h>
  30 #include <linux/quotaops.h>
  31 #include <linux/perf_event.h>
  32 #include <linux/kernel.h>
  33 #include <linux/module.h>
  34 #include <linux/suspend.h>
  35 #include <linux/writeback.h>
  36 #include <linux/swap.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/vt_kern.h>
  39 #include <linux/workqueue.h>
  40 #include <linux/hrtimer.h>
  41 #include <linux/oom.h>
  42 #include <linux/slab.h>
  43 #include <linux/input.h>
  44 #include <linux/uaccess.h>
  45 #include <linux/moduleparam.h>
  46 #include <linux/jiffies.h>
  47
  48 #include <asm/ptrace.h>
  49 #include <asm/irq_regs.h>
  50
  51 /* Whether we react on sysrq keys or just ignore them */
  52 static int __read_mostly sysrq_enabled = SYSRQ_DEFAULT_ENABLE;
  53 static bool __read_mostly sysrq_always_enabled;
  54
  55 unsigned short platform_sysrq_reset_seq[] __weak = { KEY_RESERVED };
  56 int sysrq_reset_downtime_ms __weak;
  57
  58 static bool sysrq_on(void)
  59 {
  60         return sysrq_enabled || sysrq_always_enabled;
  61 }
  62
  63 /*
  64  * A value of 1 means 'all', other nonzero values are an op mask:
  65  */
  66 static bool sysrq_on_mask(int mask)
  67 {
  68         return sysrq_always_enabled ||
  69                sysrq_enabled == 1 ||
  70                (sysrq_enabled & mask);
  71 }
  72
  73 static int __init sysrq_always_enabled_setup(char *str)
  74 {
  75         sysrq_always_enabled = true;
  76         pr_info("sysrq always enabled.\n");
  77
  78         return 1;
  79 }
  80
  81 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  82
  83
  84 static void sysrq_handle_loglevel(int key)
  85 {
  86         int i;
  87
  88         i = key - '0';
  89         console_loglevel = 7;
  90         printk("Loglevel set to %d\n", i);
  91         console_loglevel = i;
  92 }
  93 static struct sysrq_key_op sysrq_loglevel_op = {
  94         .handler        = sysrq_handle_loglevel,
  95         .help_msg       = "loglevel(0-9)",
  96         .action_msg     = "Changing Loglevel",
  97         .enable_mask    = SYSRQ_ENABLE_LOG,
  98 };
  99
 100 #ifdef CONFIG_VT
 101 static void sysrq_handle_SAK(int key)
 102 {
 103         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 104         schedule_work(SAK_work);
 105 }
 106 static struct sysrq_key_op sysrq_SAK_op = {
 107         .handler        = sysrq_handle_SAK,
 108         .help_msg       = "sak(k)",
 109         .action_msg     = "SAK",
 110         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 111 };
 112 #else
 113 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
 114 #endif
 115
 116 #ifdef CONFIG_VT
 117 static void sysrq_handle_unraw(int key)
 118 {
 119         vt_reset_unicode(fg_console);
 120 }
 121
 122 static struct sysrq_key_op sysrq_unraw_op = {
 123         .handler        = sysrq_handle_unraw,
 124         .help_msg       = "unraw(r)",
 125         .action_msg     = "Keyboard mode set to system default",
 126         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 127 };
 128 #else
 129 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
 130 #endif /* CONFIG_VT */
 131
 132 static void sysrq_handle_crash(int key)
 133 {
 134         char *killer = NULL;
 135
 136         panic_on_oops = 1;      /* force panic */
 137         wmb();
 138         *killer = 1;
 139 }
 140 static struct sysrq_key_op sysrq_crash_op = {
 141         .handler        = sysrq_handle_crash,
 142         .help_msg       = "crash(c)",
 143         .action_msg     = "Trigger a crash",
 144         .enable_mask    = SYSRQ_ENABLE_DUMP,
 145 };
 146
 147 static void sysrq_handle_reboot(int key)
 148 {
 149         lockdep_off();
 150         local_irq_enable();
 151         emergency_restart();
 152 }
 153 static struct sysrq_key_op sysrq_reboot_op = {
 154         .handler        = sysrq_handle_reboot,
 155         .help_msg       = "reboot(b)",
 156         .action_msg     = "Resetting",
 157         .enable_mask    = SYSRQ_ENABLE_BOOT,
 158 };
 159
 160 static void sysrq_handle_sync(int key)
 161 {
 162         emergency_sync();
 163 }
 164 static struct sysrq_key_op sysrq_sync_op = {
 165         .handler        = sysrq_handle_sync,
 166         .help_msg       = "sync(s)",
 167         .action_msg     = "Emergency Sync",
 168         .enable_mask    = SYSRQ_ENABLE_SYNC,
 169 };
 170
 171 static void sysrq_handle_show_timers(int key)
 172 {
 173         sysrq_timer_list_show();
 174 }
 175
 176 static struct sysrq_key_op sysrq_show_timers_op = {
 177         .handler        = sysrq_handle_show_timers,
 178         .help_msg       = "show-all-timers(q)",
 179         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 180 };
 181
 182 static void sysrq_handle_mountro(int key)
 183 {
 184         emergency_remount();
 185 }
 186 static struct sysrq_key_op sysrq_mountro_op = {
 187         .handler        = sysrq_handle_mountro,
 188         .help_msg       = "unmount(u)",
 189         .action_msg     = "Emergency Remount R/O",
 190         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 191 };
 192
 193 #ifdef CONFIG_LOCKDEP
 194 static void sysrq_handle_showlocks(int key)
 195 {
 196         debug_show_all_locks();
 197 }
 198
 199 static struct sysrq_key_op sysrq_showlocks_op = {
 200         .handler        = sysrq_handle_showlocks,
 201         .help_msg       = "show-all-locks(d)",
 202         .action_msg     = "Show Locks Held",
 203 };
 204 #else
 205 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
 206 #endif
 207
 208 #ifdef CONFIG_SMP
 209 static DEFINE_SPINLOCK(show_lock);
 210
 211 static void showacpu(void *dummy)
 212 {
 213         unsigned long flags;
 214
 215         /* Idle CPUs have no interesting backtrace. */
 216         if (idle_cpu(smp_processor_id()))
 217                 return;
 218
 219         spin_lock_irqsave(&show_lock, flags);
 220         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 221         show_stack(NULL, NULL);
 222         spin_unlock_irqrestore(&show_lock, flags);
 223 }
 224
 225 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 226 {
 227         smp_call_function(showacpu, NULL, 0);
 228 }
 229
 230 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 231
 232 static void sysrq_handle_showallcpus(int key)
 233 {
 234         /*
 235          * Fall back to the workqueue based printing if the
 236          * backtrace printing did not succeed or the
 237          * architecture has no support for it:
 238          */
 239         if (!trigger_all_cpu_backtrace()) {
 240                 struct pt_regs *regs = get_irq_regs();
 241
 242                 if (regs) {
 243                         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 244                         show_regs(regs);
 245                 }
 246                 schedule_work(&sysrq_showallcpus);
 247         }
 248 }
 249
 250 static struct sysrq_key_op sysrq_showallcpus_op = {
 251         .handler        = sysrq_handle_showallcpus,
 252         .help_msg       = "show-backtrace-all-active-cpus(l)",
 253         .action_msg     = "Show backtrace of all active CPUs",
 254         .enable_mask    = SYSRQ_ENABLE_DUMP,
 255 };
 256 #endif
 257
 258 static void sysrq_handle_showregs(int key)
 259 {
 260         struct pt_regs *regs = get_irq_regs();
 261         if (regs)
 262                 show_regs(regs);
 263         perf_event_print_debug();
 264 }
 265 static struct sysrq_key_op sysrq_showregs_op = {
 266         .handler        = sysrq_handle_showregs,
 267         .help_msg       = "show-registers(p)",
 268         .action_msg     = "Show Regs",
 269         .enable_mask    = SYSRQ_ENABLE_DUMP,
 270 };
 271
 272 static void sysrq_handle_showstate(int key)
 273 {
 274         show_state();
 275 }
 276 static struct sysrq_key_op sysrq_showstate_op = {
 277         .handler        = sysrq_handle_showstate,
 278         .help_msg       = "show-task-states(t)",
 279         .action_msg     = "Show State",
 280         .enable_mask    = SYSRQ_ENABLE_DUMP,
 281 };
 282
 283 static void sysrq_handle_showstate_blocked(int key)
 284 {
 285         show_state_filter(TASK_UNINTERRUPTIBLE);
 286 }
 287 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 288         .handler        = sysrq_handle_showstate_blocked,
 289         .help_msg       = "show-blocked-tasks(w)",
 290         .action_msg     = "Show Blocked State",
 291         .enable_mask    = SYSRQ_ENABLE_DUMP,
 292 };
 293
 294 #ifdef CONFIG_TRACING
 295 #include <linux/ftrace.h>
 296
 297 static void sysrq_ftrace_dump(int key)
 298 {
 299         ftrace_dump(DUMP_ALL);
 300 }
 301 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 302         .handler        = sysrq_ftrace_dump,
 303         .help_msg       = "dump-ftrace-buffer(z)",
 304         .action_msg     = "Dump ftrace buffer",
 305         .enable_mask    = SYSRQ_ENABLE_DUMP,
 306 };
 307 #else
 308 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
 309 #endif
 310
 311 static void sysrq_handle_showmem(int key)
 312 {
 313         show_mem(0);
 314 }
 315 static struct sysrq_key_op sysrq_showmem_op = {
 316         .handler        = sysrq_handle_showmem,
 317         .help_msg       = "show-memory-usage(m)",
 318         .action_msg     = "Show Memory",
 319         .enable_mask    = SYSRQ_ENABLE_DUMP,
 320 };
 321
 322 /*
 323  * Signal sysrq helper function.  Sends a signal to all user processes.
 324  */
 325 static void send_sig_all(int sig)
 326 {
 327         struct task_struct *p;
 328
 329         read_lock(&tasklist_lock);
 330         for_each_process(p) {
 331                 if (p->flags & PF_KTHREAD)
 332                         continue;
 333                 if (is_global_init(p))
 334                         continue;
 335
 336                 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
 337         }
 338         read_unlock(&tasklist_lock);
 339 }
 340
 341 static void sysrq_handle_term(int key)
 342 {
 343         send_sig_all(SIGTERM);
 344         console_loglevel = 8;
 345 }
 346 static struct sysrq_key_op sysrq_term_op = {
 347         .handler        = sysrq_handle_term,
 348         .help_msg       = "terminate-all-tasks(e)",
 349         .action_msg     = "Terminate All Tasks",
 350         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 351 };
 352
 353 static void moom_callback(struct work_struct *ignored)
 354 {
 355         out_of_memory(node_zonelist(first_online_node, GFP_KERNEL), GFP_KERNEL,
 356                       0, NULL, true);
 357 }
 358
 359 static DECLARE_WORK(moom_work, moom_callback);
 360
 361 static void sysrq_handle_moom(int key)
 362 {
 363         schedule_work(&moom_work);
 364 }
 365 static struct sysrq_key_op sysrq_moom_op = {
 366         .handler        = sysrq_handle_moom,
 367         .help_msg       = "memory-full-oom-kill(f)",
 368         .action_msg     = "Manual OOM execution",
 369         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 370 };
 371
 372 #ifdef CONFIG_BLOCK
 373 static void sysrq_handle_thaw(int key)
 374 {
 375         emergency_thaw_all();
 376 }
 377 static struct sysrq_key_op sysrq_thaw_op = {
 378         .handler        = sysrq_handle_thaw,
 379         .help_msg       = "thaw-filesystems(j)",
 380         .action_msg     = "Emergency Thaw of all frozen filesystems",
 381         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 382 };
 383 #endif
 384
 385 static void sysrq_handle_kill(int key)
 386 {
 387         send_sig_all(SIGKILL);
 388         console_loglevel = 8;
 389 }
 390 static struct sysrq_key_op sysrq_kill_op = {
 391         .handler        = sysrq_handle_kill,
 392         .help_msg       = "kill-all-tasks(i)",
 393         .action_msg     = "Kill All Tasks",
 394         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 395 };
 396
 397 static void sysrq_handle_unrt(int key)
 398 {
 399         normalize_rt_tasks();
 400 }
 401 static struct sysrq_key_op sysrq_unrt_op = {
 402         .handler        = sysrq_handle_unrt,
 403         .help_msg       = "nice-all-RT-tasks(n)",
 404         .action_msg     = "Nice All RT Tasks",
 405         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 406 };
 407
 408 extern struct sysrq_key_op sysrq_show_blocked_group_op;
 409
 410 /* Key Operations table and lock */
 411 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 412
 413 static struct sysrq_key_op *sysrq_key_table[36] = {
 414         &sysrq_loglevel_op,             /* 0 */
 415         &sysrq_loglevel_op,             /* 1 */
 416         &sysrq_loglevel_op,             /* 2 */
 417         &sysrq_loglevel_op,             /* 3 */
 418         &sysrq_loglevel_op,             /* 4 */
 419         &sysrq_loglevel_op,             /* 5 */
 420         &sysrq_loglevel_op,             /* 6 */
 421         &sysrq_loglevel_op,             /* 7 */
 422         &sysrq_loglevel_op,             /* 8 */
 423         &sysrq_loglevel_op,             /* 9 */
 424
 425         /*
 426          * a: Don't use for system provided sysrqs, it is handled specially on
 427          * sparc and will never arrive.
 428          */
 429         NULL,                           /* a */
 430         &sysrq_reboot_op,               /* b */
 431         &sysrq_crash_op,                /* c & ibm_emac driver debug */
 432         &sysrq_showlocks_op,            /* d */
 433         &sysrq_term_op,                 /* e */
 434         &sysrq_moom_op,                 /* f */
 435         /* g: May be registered for the kernel debugger */
 436         NULL,                           /* g */
 437         NULL,                           /* h - reserved for help */
 438         &sysrq_kill_op,                 /* i */
 439 #ifdef CONFIG_BLOCK
 440         &sysrq_thaw_op,                 /* j */
 441 #else
 442         NULL,                           /* j */
 443 #endif
 444         &sysrq_SAK_op,                  /* k */
 445 #ifdef CONFIG_SMP
 446         &sysrq_showallcpus_op,          /* l */
 447 #else
 448         NULL,                           /* l */
 449 #endif
 450         &sysrq_showmem_op,              /* m */
 451         &sysrq_unrt_op,                 /* n */
 452         /* o: This will often be registered as 'Off' at init time */
 453         NULL,                           /* o */
 454         &sysrq_showregs_op,             /* p */
 455         &sysrq_show_timers_op,          /* q */
 456         &sysrq_unraw_op,                /* r */
 457         &sysrq_sync_op,                 /* s */
 458         &sysrq_showstate_op,            /* t */
 459         &sysrq_mountro_op,              /* u */
 460         /* v: May be registered for frame buffer console restore */
 461         NULL,                           /* v */
 462         &sysrq_showstate_blocked_op,    /* w */
 463         /* x: May be registered on ppc/powerpc for xmon */
 464         /* x: May be registered on sparc64 for global PMU dump */
 465         /* x: On SPRD platform, used for dump blocked thread's group stack */
 466         &sysrq_show_blocked_group_op,                           /* x */
 467         /* y: May be registered on sparc64 for global register dump */
 468         NULL,                           /* y */
 469         &sysrq_ftrace_dump_op,          /* z */
 470 };
 471
 472 /* key2index calculation, -1 on invalid index */
 473 static int sysrq_key_table_key2index(int key)
 474 {
 475         int retval;
 476
 477         if ((key >= '0') && (key <= '9'))
 478                 retval = key - '0';
 479         else if ((key >= 'a') && (key <= 'z'))
 480                 retval = key + 10 - 'a';
 481         else
 482                 retval = -1;
 483         return retval;
 484 }
 485
 486 /*
 487  * get and put functions for the table, exposed to modules.
 488  */
 489 struct sysrq_key_op *__sysrq_get_key_op(int key)
 490 {
 491         struct sysrq_key_op *op_p = NULL;
 492         int i;
 493
 494         i = sysrq_key_table_key2index(key);
 495         if (i != -1)
 496                 op_p = sysrq_key_table[i];
 497
 498         return op_p;
 499 }
 500
 501 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 502 {
 503         int i = sysrq_key_table_key2index(key);
 504
 505         if (i != -1)
 506                 sysrq_key_table[i] = op_p;
 507 }
 508
 509 void __handle_sysrq(int key, bool check_mask)
 510 {
 511         struct sysrq_key_op *op_p;
 512         int orig_log_level;
 513         int i;
 514         unsigned long flags;
 515
 516         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 517         /*
 518          * Raise the apparent loglevel to maximum so that the sysrq header
 519          * is shown to provide the user with positive feedback.  We do not
 520          * simply emit this at KERN_EMERG as that would change message
 521          * routing in the consumers of /proc/kmsg.
 522          */
 523         orig_log_level = console_loglevel;
 524         console_loglevel = 7;
 525         printk(KERN_INFO "SysRq : ");
 526
 527         op_p = __sysrq_get_key_op(key);
 528         if (op_p) {
 529                 /*
 530                  * Should we check for enabled operations (/proc/sysrq-trigger
 531                  * should not) and is the invoked operation enabled?
 532                  */
 533                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 534                         printk("%s\n", op_p->action_msg);
 535                         console_loglevel = orig_log_level;
 536                         op_p->handler(key);
 537                 } else {
 538                         printk("This sysrq operation is disabled.\n");
 539                 }
 540         } else {
 541                 printk("HELP : ");
 542                 /* Only print the help msg once per handler */
 543                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 544                         if (sysrq_key_table[i]) {
 545                                 int j;
 546
 547                                 for (j = 0; sysrq_key_table[i] !=
 548                                                 sysrq_key_table[j]; j++)
 549                                         ;
 550                                 if (j != i)
 551                                         continue;
 552                                 printk("%s ", sysrq_key_table[i]->help_msg);
 553                         }
 554                 }
 555                 printk("\n");
 556                 console_loglevel = orig_log_level;
 557         }
 558         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 559 }
 560
 561 void handle_sysrq(int key)
 562 {
 563         if (sysrq_on())
 564                 __handle_sysrq(key, true);
 565 }
 566 EXPORT_SYMBOL(handle_sysrq);
 567
 568 #ifdef CONFIG_INPUT
 569
 570 /* Simple translation table for the SysRq keys */
 571 static const unsigned char sysrq_xlate[KEY_CNT] =
 572         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 573         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 574         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 575         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 576         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 577         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 578         "\r\000/";                                      /* 0x60 - 0x6f */
 579
 580 struct sysrq_state {
 581         struct input_handle handle;
 582         struct work_struct reinject_work;
 583         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 584         unsigned int alt;
 585         unsigned int alt_use;
 586         bool active;
 587         bool need_reinject;
 588         bool reinjecting;
 589
 590         /* reset sequence handling */
 591         bool reset_canceled;
 592         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 593         int reset_seq_len;
 594         int reset_seq_cnt;
 595         int reset_seq_version;
 596         struct timer_list keyreset_timer;
 597 };
 598
 599 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 600 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 601 static unsigned int sysrq_reset_seq_len;
 602 static unsigned int sysrq_reset_seq_version = 1;
 603
 604 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 605 {
 606         int i;
 607         unsigned short key;
 608
 609         state->reset_seq_cnt = 0;
 610
 611         for (i = 0; i < sysrq_reset_seq_len; i++) {
 612                 key = sysrq_reset_seq[i];
 613
 614                 if (key == KEY_RESERVED || key > KEY_MAX)
 615                         break;
 616
 617                 __set_bit(key, state->reset_keybit);
 618                 state->reset_seq_len++;
 619
 620                 if (test_bit(key, state->key_down))
 621                         state->reset_seq_cnt++;
 622         }
 623
 624         /* Disable reset until old keys are not released */
 625         state->reset_canceled = state->reset_seq_cnt != 0;
 626
 627         state->reset_seq_version = sysrq_reset_seq_version;
 628 }
 629
 630 static void sysrq_do_reset(unsigned long dummy)
 631 {
 632         __handle_sysrq(sysrq_xlate[KEY_B], false);
 633 }
 634
 635 static void sysrq_handle_reset_request(struct sysrq_state *state)
 636 {
 637         if (sysrq_reset_downtime_ms)
 638                 mod_timer(&state->keyreset_timer,
 639                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 640         else
 641                 sysrq_do_reset(0);
 642 }
 643
 644 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 645                                         unsigned int code, int value)
 646 {
 647         if (!test_bit(code, state->reset_keybit)) {
 648                 /*
 649                  * Pressing any key _not_ in reset sequence cancels
 650                  * the reset sequence.  Also cancelling the timer in
 651                  * case additional keys were pressed after a reset
 652                  * has been requested.
 653                  */
 654                 if (value && state->reset_seq_cnt) {
 655                         state->reset_canceled = true;
 656                         del_timer(&state->keyreset_timer);
 657                 }
 658         } else if (value == 0) {
 659                 /*
 660                  * Key release - all keys in the reset sequence need
 661                  * to be pressed and held for the reset timeout
 662                  * to hold.
 663                  */
 664                 del_timer(&state->keyreset_timer);
 665
 666                 if (--state->reset_seq_cnt == 0)
 667                         state->reset_canceled = false;
 668         } else if (value == 1) {
 669                 /* key press, not autorepeat */
 670                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 671                     !state->reset_canceled) {
 672                         sysrq_handle_reset_request(state);
 673                 }
 674         }
 675 }
 676
 677 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 678 {
 679         struct sysrq_state *sysrq =
 680                         container_of(work, struct sysrq_state, reinject_work);
 681         struct input_handle *handle = &sysrq->handle;
 682         unsigned int alt_code = sysrq->alt_use;
 683
 684         if (sysrq->need_reinject) {
 685                 /* we do not want the assignment to be reordered */
 686                 sysrq->reinjecting = true;
 687                 mb();
 688
 689                 /* Simulate press and release of Alt + SysRq */
 690                 input_inject_event(handle, EV_KEY, alt_code, 1);
 691                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 692                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 693
 694                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 695                 input_inject_event(handle, EV_KEY, alt_code, 0);
 696                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 697
 698                 mb();
 699                 sysrq->reinjecting = false;
 700         }
 701 }
 702
 703 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 704                                   unsigned int code, int value)
 705 {
 706         bool was_active = sysrq->active;
 707         bool suppress;
 708
 709         switch (code) {
 710
 711         case KEY_LEFTALT:
 712         case KEY_RIGHTALT:
 713                 if (!value) {
 714                         /* One of ALTs is being released */
 715                         if (sysrq->active && code == sysrq->alt_use)
 716                                 sysrq->active = false;
 717
 718                         sysrq->alt = KEY_RESERVED;
 719
 720                 } else if (value != 2) {
 721                         sysrq->alt = code;
 722                         sysrq->need_reinject = false;
 723                 }
 724                 break;
 725
 726         case KEY_SYSRQ:
 727                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 728                         sysrq->active = true;
 729                         sysrq->alt_use = sysrq->alt;
 730                         /*
 731                          * If nothing else will be pressed we'll need
 732                          * to re-inject Alt-SysRq keysroke.
 733                          */
 734                         sysrq->need_reinject = true;
 735                 }
 736
 737                 /*
 738                  * Pretend that sysrq was never pressed at all. This
 739                  * is needed to properly handle KGDB which will try
 740                  * to release all keys after exiting debugger. If we
 741                  * do not clear key bit it KGDB will end up sending
 742                  * release events for Alt and SysRq, potentially
 743                  * triggering print screen function.
 744                  */
 745                 if (sysrq->active)
 746                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 747
 748                 break;
 749
 750         default:
 751                 if (sysrq->active && value && value != 2) {
 752                         sysrq->need_reinject = false;
 753                         __handle_sysrq(sysrq_xlate[code], true);
 754                 }
 755                 break;
 756         }
 757
 758         suppress = sysrq->active;
 759
 760         if (!sysrq->active) {
 761
 762                 /*
 763                  * See if reset sequence has changed since the last time.
 764                  */
 765                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 766                         sysrq_parse_reset_sequence(sysrq);
 767
 768                 /*
 769                  * If we are not suppressing key presses keep track of
 770                  * keyboard state so we can release keys that have been
 771                  * pressed before entering SysRq mode.
 772                  */
 773                 if (value)
 774                         set_bit(code, sysrq->key_down);
 775                 else
 776                         clear_bit(code, sysrq->key_down);
 777
 778                 if (was_active)
 779                         schedule_work(&sysrq->reinject_work);
 780
 781                 /* Check for reset sequence */
 782                 sysrq_detect_reset_sequence(sysrq, code, value);
 783
 784         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 785                 /*
 786                  * Pass on release events for keys that was pressed before
 787                  * entering SysRq mode.
 788                  */
 789                 suppress = false;
 790         }
 791
 792         return suppress;
 793 }
 794
 795 static bool sysrq_filter(struct input_handle *handle,
 796                          unsigned int type, unsigned int code, int value)
 797 {
 798         struct sysrq_state *sysrq = handle->private;
 799         bool suppress;
 800
 801         /*
 802          * Do not filter anything if we are in the process of re-injecting
 803          * Alt+SysRq combination.
 804          */
 805         if (sysrq->reinjecting)
 806                 return false;
 807
 808         switch (type) {
 809
 810         case EV_SYN:
 811                 suppress = false;
 812                 break;
 813
 814         case EV_KEY:
 815                 suppress = sysrq_handle_keypress(sysrq, code, value);
 816                 break;
 817
 818         default:
 819                 suppress = sysrq->active;
 820                 break;
 821         }
 822
 823         return suppress;
 824 }
 825
 826 static int sysrq_connect(struct input_handler *handler,
 827                          struct input_dev *dev,
 828                          const struct input_device_id *id)
 829 {
 830         struct sysrq_state *sysrq;
 831         int error;
 832
 833         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 834         if (!sysrq)
 835                 return -ENOMEM;
 836
 837         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 838
 839         sysrq->handle.dev = dev;
 840         sysrq->handle.handler = handler;
 841         sysrq->handle.name = "sysrq";
 842         sysrq->handle.private = sysrq;
 843         setup_timer(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 844
 845         error = input_register_handle(&sysrq->handle);
 846         if (error) {
 847                 pr_err("Failed to register input sysrq handler, error %d\n",
 848                         error);
 849                 goto err_free;
 850         }
 851
 852         error = input_open_device(&sysrq->handle);
 853         if (error) {
 854                 pr_err("Failed to open input device, error %d\n", error);
 855                 goto err_unregister;
 856         }
 857
 858         return 0;
 859
 860  err_unregister:
 861         input_unregister_handle(&sysrq->handle);
 862  err_free:
 863         kfree(sysrq);
 864         return error;
 865 }
 866
 867 static void sysrq_disconnect(struct input_handle *handle)
 868 {
 869         struct sysrq_state *sysrq = handle->private;
 870
 871         input_close_device(handle);
 872         cancel_work_sync(&sysrq->reinject_work);
 873         del_timer_sync(&sysrq->keyreset_timer);
 874         input_unregister_handle(handle);
 875         kfree(sysrq);
 876 }
 877
 878 /*
 879  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 880  * keyboards have SysRq key predefined and so user may add it to keymap
 881  * later, but we expect all such keyboards to have left alt.
 882  */
 883 static const struct input_device_id sysrq_ids[] = {
 884         {
 885                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 886                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 887                 .evbit = { BIT_MASK(EV_KEY) },
 888                 .keybit = { BIT_MASK(KEY_LEFTALT) },
 889         },
 890         { },
 891 };
 892
 893 static struct input_handler sysrq_handler = {
 894         .filter         = sysrq_filter,
 895         .connect        = sysrq_connect,
 896         .disconnect     = sysrq_disconnect,
 897         .name           = "sysrq",
 898         .id_table       = sysrq_ids,
 899 };
 900
 901 static bool sysrq_handler_registered;
 902
 903 static inline void sysrq_register_handler(void)
 904 {
 905         unsigned short key;
 906         int error;
 907         int i;
 908
 909         for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
 910                 key = platform_sysrq_reset_seq[i];
 911                 if (key == KEY_RESERVED || key > KEY_MAX)
 912                         break;
 913
 914                 sysrq_reset_seq[sysrq_reset_seq_len++] = key;
 915         }
 916
 917         error = input_register_handler(&sysrq_handler);
 918         if (error)
 919                 pr_err("Failed to register input handler, error %d", error);
 920         else
 921                 sysrq_handler_registered = true;
 922 }
 923
 924 static inline void sysrq_unregister_handler(void)
 925 {
 926         if (sysrq_handler_registered) {
 927                 input_unregister_handler(&sysrq_handler);
 928                 sysrq_handler_registered = false;
 929         }
 930 }
 931
 932 static int sysrq_reset_seq_param_set(const char *buffer,
 933                                      const struct kernel_param *kp)
 934 {
 935         unsigned long val;
 936         int error;
 937
 938         error = strict_strtoul(buffer, 0, &val);
 939         if (error < 0)
 940                 return error;
 941
 942         if (val > KEY_MAX)
 943                 return -EINVAL;
 944
 945         *((unsigned short *)kp->arg) = val;
 946         sysrq_reset_seq_version++;
 947
 948         return 0;
 949 }
 950
 951 static struct kernel_param_ops param_ops_sysrq_reset_seq = {
 952         .get    = param_get_ushort,
 953         .set    = sysrq_reset_seq_param_set,
 954 };
 955
 956 #define param_check_sysrq_reset_seq(name, p)    \
 957         __param_check(name, p, unsigned short)
 958
 959 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
 960                          &sysrq_reset_seq_len, 0644);
 961
 962 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
 963
 964 #else
 965
 966 static inline void sysrq_register_handler(void)
 967 {
 968 }
 969
 970 static inline void sysrq_unregister_handler(void)
 971 {
 972 }
 973
 974 #endif /* CONFIG_INPUT */
 975
 976 int sysrq_toggle_support(int enable_mask)
 977 {
 978         bool was_enabled = sysrq_on();
 979
 980         sysrq_enabled = enable_mask;
 981
 982         if (was_enabled != sysrq_on()) {
 983                 if (sysrq_on())
 984                         sysrq_register_handler();
 985                 else
 986                         sysrq_unregister_handler();
 987         }
 988
 989         return 0;
 990 }
 991
 992 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
 993                                 struct sysrq_key_op *remove_op_p)
 994 {
 995         int retval;
 996         unsigned long flags;
 997
 998         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 999         if (__sysrq_get_key_op(key) == remove_op_p) {
1000                 __sysrq_put_key_op(key, insert_op_p);
1001                 retval = 0;
1002         } else {
1003                 retval = -1;
1004         }
1005         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
1006         return retval;
1007 }
1008
1009 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1010 {
1011         return __sysrq_swap_key_ops(key, op_p, NULL);
1012 }
1013 EXPORT_SYMBOL(register_sysrq_key);
1014
1015 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1016 {
1017         return __sysrq_swap_key_ops(key, NULL, op_p);
1018 }
1019 EXPORT_SYMBOL(unregister_sysrq_key);
1020
1021 #ifdef CONFIG_PROC_FS
1022 /*
1023  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1024  */
1025 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1026                                    size_t count, loff_t *ppos)
1027 {
1028         if (count) {
1029                 char c;
1030
1031                 if (get_user(c, buf))
1032                         return -EFAULT;
1033                 __handle_sysrq(c, false);
1034         }
1035
1036         return count;
1037 }
1038
1039 static const struct file_operations proc_sysrq_trigger_operations = {
1040         .write          = write_sysrq_trigger,
1041         .llseek         = noop_llseek,
1042 };
1043
1044 static void sysrq_init_procfs(void)
1045 {
1046         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1047                          &proc_sysrq_trigger_operations))
1048                 pr_err("Failed to register proc interface\n");
1049 }
1050
1051 #else
1052
1053 static inline void sysrq_init_procfs(void)
1054 {
1055 }
1056
1057 #endif /* CONFIG_PROC_FS */
1058
1059 static int __init sysrq_init(void)
1060 {
1061         sysrq_init_procfs();
1062
1063         if (sysrq_on())
1064                 sysrq_register_handler();
1065
1066         return 0;
1067 }
1068 module_init(sysrq_init);