drivers/tty/sysrq.c

   1 /*
   2  *      Linux Magic System Request Key Hacks
   3  *
   4  *      (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   5  *      based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
   6  *
   7  *      (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
   8  *      overhauled to use key registration
   9  *      based upon discusions in irc://irc.openprojects.net/#kernelnewbies
  10  *
  11  *      Copyright (c) 2010 Dmitry Torokhov
  12  *      Input handler conversion
  13  */
  14
  15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  16
  17 #include <linux/sched.h>
  18 #include <linux/sched/rt.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/mm.h>
  21 #include <linux/fs.h>
  22 #include <linux/mount.h>
  23 #include <linux/kdev_t.h>
  24 #include <linux/major.h>
  25 #include <linux/reboot.h>
  26 #include <linux/sysrq.h>
  27 #include <linux/kbd_kern.h>
  28 #include <linux/proc_fs.h>
  29 #include <linux/nmi.h>
  30 #include <linux/quotaops.h>
  31 #include <linux/perf_event.h>
  32 #include <linux/kernel.h>
  33 #include <linux/module.h>
  34 #include <linux/suspend.h>
  35 #include <linux/writeback.h>
  36 #include <linux/swap.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/vt_kern.h>
  39 #include <linux/workqueue.h>
  40 #include <linux/hrtimer.h>
  41 #include <linux/oom.h>
  42 #include <linux/slab.h>
  43 #include <linux/input.h>
  44 #include <linux/uaccess.h>
  45 #include <linux/moduleparam.h>
  46 #include <linux/jiffies.h>
  47 #include <linux/syscalls.h>
  48 #include <linux/of.h>
  49 #include <linux/rcupdate.h>
  50
  51 #include <asm/ptrace.h>
  52 #include <asm/irq_regs.h>
  53
  54 /* Whether we react on sysrq keys or just ignore them */
  55 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
  56 static bool __read_mostly sysrq_always_enabled;
  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 = CONSOLE_LOGLEVEL_DEFAULT;
  90         pr_info("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         pr_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                         pr_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         show_workqueue_state();
 276 }
 277 static struct sysrq_key_op sysrq_showstate_op = {
 278         .handler        = sysrq_handle_showstate,
 279         .help_msg       = "show-task-states(t)",
 280         .action_msg     = "Show State",
 281         .enable_mask    = SYSRQ_ENABLE_DUMP,
 282 };
 283
 284 static void sysrq_handle_showstate_blocked(int key)
 285 {
 286         show_state_filter(TASK_UNINTERRUPTIBLE);
 287 }
 288 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 289         .handler        = sysrq_handle_showstate_blocked,
 290         .help_msg       = "show-blocked-tasks(w)",
 291         .action_msg     = "Show Blocked State",
 292         .enable_mask    = SYSRQ_ENABLE_DUMP,
 293 };
 294
 295 #ifdef CONFIG_TRACING
 296 #include <linux/ftrace.h>
 297
 298 static void sysrq_ftrace_dump(int key)
 299 {
 300         ftrace_dump(DUMP_ALL);
 301 }
 302 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 303         .handler        = sysrq_ftrace_dump,
 304         .help_msg       = "dump-ftrace-buffer(z)",
 305         .action_msg     = "Dump ftrace buffer",
 306         .enable_mask    = SYSRQ_ENABLE_DUMP,
 307 };
 308 #else
 309 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
 310 #endif
 311
 312 static void sysrq_handle_showmem(int key)
 313 {
 314         show_mem(0);
 315 }
 316 static struct sysrq_key_op sysrq_showmem_op = {
 317         .handler        = sysrq_handle_showmem,
 318         .help_msg       = "show-memory-usage(m)",
 319         .action_msg     = "Show Memory",
 320         .enable_mask    = SYSRQ_ENABLE_DUMP,
 321 };
 322
 323 /*
 324  * Signal sysrq helper function.  Sends a signal to all user processes.
 325  */
 326 static void send_sig_all(int sig)
 327 {
 328         struct task_struct *p;
 329
 330         read_lock(&tasklist_lock);
 331         for_each_process(p) {
 332                 if (p->flags & PF_KTHREAD)
 333                         continue;
 334                 if (is_global_init(p))
 335                         continue;
 336
 337                 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
 338         }
 339         read_unlock(&tasklist_lock);
 340 }
 341
 342 static void sysrq_handle_term(int key)
 343 {
 344         send_sig_all(SIGTERM);
 345         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 346 }
 347 static struct sysrq_key_op sysrq_term_op = {
 348         .handler        = sysrq_handle_term,
 349         .help_msg       = "terminate-all-tasks(e)",
 350         .action_msg     = "Terminate All Tasks",
 351         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 352 };
 353
 354 static void moom_callback(struct work_struct *ignored)
 355 {
 356         if (!out_of_memory(node_zonelist(first_memory_node, GFP_KERNEL),
 357                            GFP_KERNEL, 0, NULL, true))
 358                 pr_info("OOM request ignored because killer is disabled\n");
 359 }
 360
 361 static DECLARE_WORK(moom_work, moom_callback);
 362
 363 static void sysrq_handle_moom(int key)
 364 {
 365         schedule_work(&moom_work);
 366 }
 367 static struct sysrq_key_op sysrq_moom_op = {
 368         .handler        = sysrq_handle_moom,
 369         .help_msg       = "memory-full-oom-kill(f)",
 370         .action_msg     = "Manual OOM execution",
 371         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 372 };
 373
 374 #ifdef CONFIG_BLOCK
 375 static void sysrq_handle_thaw(int key)
 376 {
 377         emergency_thaw_all();
 378 }
 379 static struct sysrq_key_op sysrq_thaw_op = {
 380         .handler        = sysrq_handle_thaw,
 381         .help_msg       = "thaw-filesystems(j)",
 382         .action_msg     = "Emergency Thaw of all frozen filesystems",
 383         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 384 };
 385 #endif
 386
 387 static void sysrq_handle_kill(int key)
 388 {
 389         send_sig_all(SIGKILL);
 390         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 391 }
 392 static struct sysrq_key_op sysrq_kill_op = {
 393         .handler        = sysrq_handle_kill,
 394         .help_msg       = "kill-all-tasks(i)",
 395         .action_msg     = "Kill All Tasks",
 396         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 397 };
 398
 399 static void sysrq_handle_unrt(int key)
 400 {
 401         normalize_rt_tasks();
 402 }
 403 static struct sysrq_key_op sysrq_unrt_op = {
 404         .handler        = sysrq_handle_unrt,
 405         .help_msg       = "nice-all-RT-tasks(n)",
 406         .action_msg     = "Nice All RT Tasks",
 407         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 408 };
 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         NULL,                           /* x */
 466         /* y: May be registered on sparc64 for global register dump */
 467         NULL,                           /* y */
 468         &sysrq_ftrace_dump_op,          /* z */
 469 };
 470
 471 /* key2index calculation, -1 on invalid index */
 472 static int sysrq_key_table_key2index(int key)
 473 {
 474         int retval;
 475
 476         if ((key >= '0') && (key <= '9'))
 477                 retval = key - '0';
 478         else if ((key >= 'a') && (key <= 'z'))
 479                 retval = key + 10 - 'a';
 480         else
 481                 retval = -1;
 482         return retval;
 483 }
 484
 485 /*
 486  * get and put functions for the table, exposed to modules.
 487  */
 488 struct sysrq_key_op *__sysrq_get_key_op(int key)
 489 {
 490         struct sysrq_key_op *op_p = NULL;
 491         int i;
 492
 493         i = sysrq_key_table_key2index(key);
 494         if (i != -1)
 495                 op_p = sysrq_key_table[i];
 496
 497         return op_p;
 498 }
 499
 500 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 501 {
 502         int i = sysrq_key_table_key2index(key);
 503
 504         if (i != -1)
 505                 sysrq_key_table[i] = op_p;
 506 }
 507
 508 void __handle_sysrq(int key, bool check_mask)
 509 {
 510         struct sysrq_key_op *op_p;
 511         int orig_log_level;
 512         int i;
 513
 514         rcu_sysrq_start();
 515         rcu_read_lock();
 516         /*
 517          * Raise the apparent loglevel to maximum so that the sysrq header
 518          * is shown to provide the user with positive feedback.  We do not
 519          * simply emit this at KERN_EMERG as that would change message
 520          * routing in the consumers of /proc/kmsg.
 521          */
 522         orig_log_level = console_loglevel;
 523         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 524         pr_info("SysRq : ");
 525
 526         op_p = __sysrq_get_key_op(key);
 527         if (op_p) {
 528                 /*
 529                  * Should we check for enabled operations (/proc/sysrq-trigger
 530                  * should not) and is the invoked operation enabled?
 531                  */
 532                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 533                         pr_cont("%s\n", op_p->action_msg);
 534                         console_loglevel = orig_log_level;
 535                         op_p->handler(key);
 536                 } else {
 537                         pr_cont("This sysrq operation is disabled.\n");
 538                 }
 539         } else {
 540                 pr_cont("HELP : ");
 541                 /* Only print the help msg once per handler */
 542                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 543                         if (sysrq_key_table[i]) {
 544                                 int j;
 545
 546                                 for (j = 0; sysrq_key_table[i] !=
 547                                                 sysrq_key_table[j]; j++)
 548                                         ;
 549                                 if (j != i)
 550                                         continue;
 551                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 552                         }
 553                 }
 554                 pr_cont("\n");
 555                 console_loglevel = orig_log_level;
 556         }
 557         rcu_read_unlock();
 558         rcu_sysrq_end();
 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 static int sysrq_reset_downtime_ms;
 570
 571 /* Simple translation table for the SysRq keys */
 572 static const unsigned char sysrq_xlate[KEY_CNT] =
 573         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 574         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 575         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 576         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 577         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 578         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 579         "\r\000/";                                      /* 0x60 - 0x6f */
 580
 581 struct sysrq_state {
 582         struct input_handle handle;
 583         struct work_struct reinject_work;
 584         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 585         unsigned int alt;
 586         unsigned int alt_use;
 587         bool active;
 588         bool need_reinject;
 589         bool reinjecting;
 590
 591         /* reset sequence handling */
 592         bool reset_canceled;
 593         bool reset_requested;
 594         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 595         int reset_seq_len;
 596         int reset_seq_cnt;
 597         int reset_seq_version;
 598         struct timer_list keyreset_timer;
 599 };
 600
 601 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 602 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 603 static unsigned int sysrq_reset_seq_len;
 604 static unsigned int sysrq_reset_seq_version = 1;
 605
 606 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 607 {
 608         int i;
 609         unsigned short key;
 610
 611         state->reset_seq_cnt = 0;
 612
 613         for (i = 0; i < sysrq_reset_seq_len; i++) {
 614                 key = sysrq_reset_seq[i];
 615
 616                 if (key == KEY_RESERVED || key > KEY_MAX)
 617                         break;
 618
 619                 __set_bit(key, state->reset_keybit);
 620                 state->reset_seq_len++;
 621
 622                 if (test_bit(key, state->key_down))
 623                         state->reset_seq_cnt++;
 624         }
 625
 626         /* Disable reset until old keys are not released */
 627         state->reset_canceled = state->reset_seq_cnt != 0;
 628
 629         state->reset_seq_version = sysrq_reset_seq_version;
 630 }
 631
 632 static void sysrq_do_reset(unsigned long _state)
 633 {
 634         struct sysrq_state *state = (struct sysrq_state *) _state;
 635
 636         state->reset_requested = true;
 637
 638         sys_sync();
 639         kernel_restart(NULL);
 640 }
 641
 642 static void sysrq_handle_reset_request(struct sysrq_state *state)
 643 {
 644         if (state->reset_requested)
 645                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 646
 647         if (sysrq_reset_downtime_ms)
 648                 mod_timer(&state->keyreset_timer,
 649                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 650         else
 651                 sysrq_do_reset((unsigned long)state);
 652 }
 653
 654 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 655                                         unsigned int code, int value)
 656 {
 657         if (!test_bit(code, state->reset_keybit)) {
 658                 /*
 659                  * Pressing any key _not_ in reset sequence cancels
 660                  * the reset sequence.  Also cancelling the timer in
 661                  * case additional keys were pressed after a reset
 662                  * has been requested.
 663                  */
 664                 if (value && state->reset_seq_cnt) {
 665                         state->reset_canceled = true;
 666                         del_timer(&state->keyreset_timer);
 667                 }
 668         } else if (value == 0) {
 669                 /*
 670                  * Key release - all keys in the reset sequence need
 671                  * to be pressed and held for the reset timeout
 672                  * to hold.
 673                  */
 674                 del_timer(&state->keyreset_timer);
 675
 676                 if (--state->reset_seq_cnt == 0)
 677                         state->reset_canceled = false;
 678         } else if (value == 1) {
 679                 /* key press, not autorepeat */
 680                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 681                     !state->reset_canceled) {
 682                         sysrq_handle_reset_request(state);
 683                 }
 684         }
 685 }
 686
 687 #ifdef CONFIG_OF
 688 static void sysrq_of_get_keyreset_config(void)
 689 {
 690         u32 key;
 691         struct device_node *np;
 692         struct property *prop;
 693         const __be32 *p;
 694
 695         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 696         if (!np) {
 697                 pr_debug("No sysrq node found");
 698                 return;
 699         }
 700
 701         /* Reset in case a __weak definition was present */
 702         sysrq_reset_seq_len = 0;
 703
 704         of_property_for_each_u32(np, "keyset", prop, p, key) {
 705                 if (key == KEY_RESERVED || key > KEY_MAX ||
 706                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 707                         break;
 708
 709                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 710         }
 711
 712         /* Get reset timeout if any. */
 713         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 714 }
 715 #else
 716 static void sysrq_of_get_keyreset_config(void)
 717 {
 718 }
 719 #endif
 720
 721 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 722 {
 723         struct sysrq_state *sysrq =
 724                         container_of(work, struct sysrq_state, reinject_work);
 725         struct input_handle *handle = &sysrq->handle;
 726         unsigned int alt_code = sysrq->alt_use;
 727
 728         if (sysrq->need_reinject) {
 729                 /* we do not want the assignment to be reordered */
 730                 sysrq->reinjecting = true;
 731                 mb();
 732
 733                 /* Simulate press and release of Alt + SysRq */
 734                 input_inject_event(handle, EV_KEY, alt_code, 1);
 735                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 736                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 737
 738                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 739                 input_inject_event(handle, EV_KEY, alt_code, 0);
 740                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 741
 742                 mb();
 743                 sysrq->reinjecting = false;
 744         }
 745 }
 746
 747 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 748                                   unsigned int code, int value)
 749 {
 750         bool was_active = sysrq->active;
 751         bool suppress;
 752
 753         switch (code) {
 754
 755         case KEY_LEFTALT:
 756         case KEY_RIGHTALT:
 757                 if (!value) {
 758                         /* One of ALTs is being released */
 759                         if (sysrq->active && code == sysrq->alt_use)
 760                                 sysrq->active = false;
 761
 762                         sysrq->alt = KEY_RESERVED;
 763
 764                 } else if (value != 2) {
 765                         sysrq->alt = code;
 766                         sysrq->need_reinject = false;
 767                 }
 768                 break;
 769
 770         case KEY_SYSRQ:
 771                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 772                         sysrq->active = true;
 773                         sysrq->alt_use = sysrq->alt;
 774                         /*
 775                          * If nothing else will be pressed we'll need
 776                          * to re-inject Alt-SysRq keysroke.
 777                          */
 778                         sysrq->need_reinject = true;
 779                 }
 780
 781                 /*
 782                  * Pretend that sysrq was never pressed at all. This
 783                  * is needed to properly handle KGDB which will try
 784                  * to release all keys after exiting debugger. If we
 785                  * do not clear key bit it KGDB will end up sending
 786                  * release events for Alt and SysRq, potentially
 787                  * triggering print screen function.
 788                  */
 789                 if (sysrq->active)
 790                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 791
 792                 break;
 793
 794         default:
 795                 if (sysrq->active && value && value != 2) {
 796                         sysrq->need_reinject = false;
 797                         __handle_sysrq(sysrq_xlate[code], true);
 798                 }
 799                 break;
 800         }
 801
 802         suppress = sysrq->active;
 803
 804         if (!sysrq->active) {
 805
 806                 /*
 807                  * See if reset sequence has changed since the last time.
 808                  */
 809                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 810                         sysrq_parse_reset_sequence(sysrq);
 811
 812                 /*
 813                  * If we are not suppressing key presses keep track of
 814                  * keyboard state so we can release keys that have been
 815                  * pressed before entering SysRq mode.
 816                  */
 817                 if (value)
 818                         set_bit(code, sysrq->key_down);
 819                 else
 820                         clear_bit(code, sysrq->key_down);
 821
 822                 if (was_active)
 823                         schedule_work(&sysrq->reinject_work);
 824
 825                 /* Check for reset sequence */
 826                 sysrq_detect_reset_sequence(sysrq, code, value);
 827
 828         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 829                 /*
 830                  * Pass on release events for keys that was pressed before
 831                  * entering SysRq mode.
 832                  */
 833                 suppress = false;
 834         }
 835
 836         return suppress;
 837 }
 838
 839 static bool sysrq_filter(struct input_handle *handle,
 840                          unsigned int type, unsigned int code, int value)
 841 {
 842         struct sysrq_state *sysrq = handle->private;
 843         bool suppress;
 844
 845         /*
 846          * Do not filter anything if we are in the process of re-injecting
 847          * Alt+SysRq combination.
 848          */
 849         if (sysrq->reinjecting)
 850                 return false;
 851
 852         switch (type) {
 853
 854         case EV_SYN:
 855                 suppress = false;
 856                 break;
 857
 858         case EV_KEY:
 859                 suppress = sysrq_handle_keypress(sysrq, code, value);
 860                 break;
 861
 862         default:
 863                 suppress = sysrq->active;
 864                 break;
 865         }
 866
 867         return suppress;
 868 }
 869
 870 static int sysrq_connect(struct input_handler *handler,
 871                          struct input_dev *dev,
 872                          const struct input_device_id *id)
 873 {
 874         struct sysrq_state *sysrq;
 875         int error;
 876
 877         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 878         if (!sysrq)
 879                 return -ENOMEM;
 880
 881         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 882
 883         sysrq->handle.dev = dev;
 884         sysrq->handle.handler = handler;
 885         sysrq->handle.name = "sysrq";
 886         sysrq->handle.private = sysrq;
 887         setup_timer(&sysrq->keyreset_timer,
 888                     sysrq_do_reset, (unsigned long)sysrq);
 889
 890         error = input_register_handle(&sysrq->handle);
 891         if (error) {
 892                 pr_err("Failed to register input sysrq handler, error %d\n",
 893                         error);
 894                 goto err_free;
 895         }
 896
 897         error = input_open_device(&sysrq->handle);
 898         if (error) {
 899                 pr_err("Failed to open input device, error %d\n", error);
 900                 goto err_unregister;
 901         }
 902
 903         return 0;
 904
 905  err_unregister:
 906         input_unregister_handle(&sysrq->handle);
 907  err_free:
 908         kfree(sysrq);
 909         return error;
 910 }
 911
 912 static void sysrq_disconnect(struct input_handle *handle)
 913 {
 914         struct sysrq_state *sysrq = handle->private;
 915
 916         input_close_device(handle);
 917         cancel_work_sync(&sysrq->reinject_work);
 918         del_timer_sync(&sysrq->keyreset_timer);
 919         input_unregister_handle(handle);
 920         kfree(sysrq);
 921 }
 922
 923 /*
 924  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 925  * keyboards have SysRq key predefined and so user may add it to keymap
 926  * later, but we expect all such keyboards to have left alt.
 927  */
 928 static const struct input_device_id sysrq_ids[] = {
 929         {
 930                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 931                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 932                 .evbit = { BIT_MASK(EV_KEY) },
 933                 .keybit = { BIT_MASK(KEY_LEFTALT) },
 934         },
 935         { },
 936 };
 937
 938 static struct input_handler sysrq_handler = {
 939         .filter         = sysrq_filter,
 940         .connect        = sysrq_connect,
 941         .disconnect     = sysrq_disconnect,
 942         .name           = "sysrq",
 943         .id_table       = sysrq_ids,
 944 };
 945
 946 static bool sysrq_handler_registered;
 947
 948 static inline void sysrq_register_handler(void)
 949 {
 950         int error;
 951
 952         sysrq_of_get_keyreset_config();
 953
 954         error = input_register_handler(&sysrq_handler);
 955         if (error)
 956                 pr_err("Failed to register input handler, error %d", error);
 957         else
 958                 sysrq_handler_registered = true;
 959 }
 960
 961 static inline void sysrq_unregister_handler(void)
 962 {
 963         if (sysrq_handler_registered) {
 964                 input_unregister_handler(&sysrq_handler);
 965                 sysrq_handler_registered = false;
 966         }
 967 }
 968
 969 static int sysrq_reset_seq_param_set(const char *buffer,
 970                                      const struct kernel_param *kp)
 971 {
 972         unsigned long val;
 973         int error;
 974
 975         error = kstrtoul(buffer, 0, &val);
 976         if (error < 0)
 977                 return error;
 978
 979         if (val > KEY_MAX)
 980                 return -EINVAL;
 981
 982         *((unsigned short *)kp->arg) = val;
 983         sysrq_reset_seq_version++;
 984
 985         return 0;
 986 }
 987
 988 static struct kernel_param_ops param_ops_sysrq_reset_seq = {
 989         .get    = param_get_ushort,
 990         .set    = sysrq_reset_seq_param_set,
 991 };
 992
 993 #define param_check_sysrq_reset_seq(name, p)    \
 994         __param_check(name, p, unsigned short)
 995
 996 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
 997                          &sysrq_reset_seq_len, 0644);
 998
 999 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1000
1001 #else
1002
1003 static inline void sysrq_register_handler(void)
1004 {
1005 }
1006
1007 static inline void sysrq_unregister_handler(void)
1008 {
1009 }
1010
1011 #endif /* CONFIG_INPUT */
1012
1013 int sysrq_toggle_support(int enable_mask)
1014 {
1015         bool was_enabled = sysrq_on();
1016
1017         sysrq_enabled = enable_mask;
1018
1019         if (was_enabled != sysrq_on()) {
1020                 if (sysrq_on())
1021                         sysrq_register_handler();
1022                 else
1023                         sysrq_unregister_handler();
1024         }
1025
1026         return 0;
1027 }
1028
1029 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1030                                 struct sysrq_key_op *remove_op_p)
1031 {
1032         int retval;
1033
1034         spin_lock(&sysrq_key_table_lock);
1035         if (__sysrq_get_key_op(key) == remove_op_p) {
1036                 __sysrq_put_key_op(key, insert_op_p);
1037                 retval = 0;
1038         } else {
1039                 retval = -1;
1040         }
1041         spin_unlock(&sysrq_key_table_lock);
1042
1043         /*
1044          * A concurrent __handle_sysrq either got the old op or the new op.
1045          * Wait for it to go away before returning, so the code for an old
1046          * op is not freed (eg. on module unload) while it is in use.
1047          */
1048         synchronize_rcu();
1049
1050         return retval;
1051 }
1052
1053 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1054 {
1055         return __sysrq_swap_key_ops(key, op_p, NULL);
1056 }
1057 EXPORT_SYMBOL(register_sysrq_key);
1058
1059 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1060 {
1061         return __sysrq_swap_key_ops(key, NULL, op_p);
1062 }
1063 EXPORT_SYMBOL(unregister_sysrq_key);
1064
1065 #ifdef CONFIG_PROC_FS
1066 /*
1067  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1068  */
1069 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1070                                    size_t count, loff_t *ppos)
1071 {
1072         if (count) {
1073                 char c;
1074
1075                 if (get_user(c, buf))
1076                         return -EFAULT;
1077                 __handle_sysrq(c, false);
1078         }
1079
1080         return count;
1081 }
1082
1083 static const struct file_operations proc_sysrq_trigger_operations = {
1084         .write          = write_sysrq_trigger,
1085         .llseek         = noop_llseek,
1086 };
1087
1088 static void sysrq_init_procfs(void)
1089 {
1090         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1091                          &proc_sysrq_trigger_operations))
1092                 pr_err("Failed to register proc interface\n");
1093 }
1094
1095 #else
1096
1097 static inline void sysrq_init_procfs(void)
1098 {
1099 }
1100
1101 #endif /* CONFIG_PROC_FS */
1102
1103 static int __init sysrq_init(void)
1104 {
1105         sysrq_init_procfs();
1106
1107         if (sysrq_on())
1108                 sysrq_register_handler();
1109
1110         return 0;
1111 }
1112 module_init(sysrq_init);