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         /* we need to release the RCU read lock here,
 137          * otherwise we get an annoying
 138          * 'BUG: sleeping function called from invalid context'
 139          * complaint from the kernel before the panic.
 140          */
 141         rcu_read_unlock();
 142         panic_on_oops = 1;      /* force panic */
 143         wmb();
 144         *killer = 1;
 145 }
 146 static struct sysrq_key_op sysrq_crash_op = {
 147         .handler        = sysrq_handle_crash,
 148         .help_msg       = "crash(c)",
 149         .action_msg     = "Trigger a crash",
 150         .enable_mask    = SYSRQ_ENABLE_DUMP,
 151 };
 152
 153 static void sysrq_handle_reboot(int key)
 154 {
 155         lockdep_off();
 156         local_irq_enable();
 157         emergency_restart();
 158 }
 159 static struct sysrq_key_op sysrq_reboot_op = {
 160         .handler        = sysrq_handle_reboot,
 161         .help_msg       = "reboot(b)",
 162         .action_msg     = "Resetting",
 163         .enable_mask    = SYSRQ_ENABLE_BOOT,
 164 };
 165
 166 static void sysrq_handle_sync(int key)
 167 {
 168         emergency_sync();
 169 }
 170 static struct sysrq_key_op sysrq_sync_op = {
 171         .handler        = sysrq_handle_sync,
 172         .help_msg       = "sync(s)",
 173         .action_msg     = "Emergency Sync",
 174         .enable_mask    = SYSRQ_ENABLE_SYNC,
 175 };
 176
 177 static void sysrq_handle_show_timers(int key)
 178 {
 179         sysrq_timer_list_show();
 180 }
 181
 182 static struct sysrq_key_op sysrq_show_timers_op = {
 183         .handler        = sysrq_handle_show_timers,
 184         .help_msg       = "show-all-timers(q)",
 185         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 186 };
 187
 188 static void sysrq_handle_mountro(int key)
 189 {
 190         emergency_remount();
 191 }
 192 static struct sysrq_key_op sysrq_mountro_op = {
 193         .handler        = sysrq_handle_mountro,
 194         .help_msg       = "unmount(u)",
 195         .action_msg     = "Emergency Remount R/O",
 196         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 197 };
 198
 199 #ifdef CONFIG_LOCKDEP
 200 static void sysrq_handle_showlocks(int key)
 201 {
 202         debug_show_all_locks();
 203 }
 204
 205 static struct sysrq_key_op sysrq_showlocks_op = {
 206         .handler        = sysrq_handle_showlocks,
 207         .help_msg       = "show-all-locks(d)",
 208         .action_msg     = "Show Locks Held",
 209 };
 210 #else
 211 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
 212 #endif
 213
 214 #ifdef CONFIG_SMP
 215 static DEFINE_SPINLOCK(show_lock);
 216
 217 static void showacpu(void *dummy)
 218 {
 219         unsigned long flags;
 220
 221         /* Idle CPUs have no interesting backtrace. */
 222         if (idle_cpu(smp_processor_id()))
 223                 return;
 224
 225         spin_lock_irqsave(&show_lock, flags);
 226         pr_info("CPU%d:\n", smp_processor_id());
 227         show_stack(NULL, NULL);
 228         spin_unlock_irqrestore(&show_lock, flags);
 229 }
 230
 231 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 232 {
 233         smp_call_function(showacpu, NULL, 0);
 234 }
 235
 236 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 237
 238 static void sysrq_handle_showallcpus(int key)
 239 {
 240         /*
 241          * Fall back to the workqueue based printing if the
 242          * backtrace printing did not succeed or the
 243          * architecture has no support for it:
 244          */
 245         if (!trigger_all_cpu_backtrace()) {
 246                 struct pt_regs *regs = get_irq_regs();
 247
 248                 if (regs) {
 249                         pr_info("CPU%d:\n", smp_processor_id());
 250                         show_regs(regs);
 251                 }
 252                 schedule_work(&sysrq_showallcpus);
 253         }
 254 }
 255
 256 static struct sysrq_key_op sysrq_showallcpus_op = {
 257         .handler        = sysrq_handle_showallcpus,
 258         .help_msg       = "show-backtrace-all-active-cpus(l)",
 259         .action_msg     = "Show backtrace of all active CPUs",
 260         .enable_mask    = SYSRQ_ENABLE_DUMP,
 261 };
 262 #endif
 263
 264 static void sysrq_handle_showregs(int key)
 265 {
 266         struct pt_regs *regs = get_irq_regs();
 267         if (regs)
 268                 show_regs(regs);
 269         perf_event_print_debug();
 270 }
 271 static struct sysrq_key_op sysrq_showregs_op = {
 272         .handler        = sysrq_handle_showregs,
 273         .help_msg       = "show-registers(p)",
 274         .action_msg     = "Show Regs",
 275         .enable_mask    = SYSRQ_ENABLE_DUMP,
 276 };
 277
 278 static void sysrq_handle_showstate(int key)
 279 {
 280         show_state();
 281         show_workqueue_state();
 282 }
 283 static struct sysrq_key_op sysrq_showstate_op = {
 284         .handler        = sysrq_handle_showstate,
 285         .help_msg       = "show-task-states(t)",
 286         .action_msg     = "Show State",
 287         .enable_mask    = SYSRQ_ENABLE_DUMP,
 288 };
 289
 290 static void sysrq_handle_showstate_blocked(int key)
 291 {
 292         show_state_filter(TASK_UNINTERRUPTIBLE);
 293 }
 294 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 295         .handler        = sysrq_handle_showstate_blocked,
 296         .help_msg       = "show-blocked-tasks(w)",
 297         .action_msg     = "Show Blocked State",
 298         .enable_mask    = SYSRQ_ENABLE_DUMP,
 299 };
 300
 301 #ifdef CONFIG_TRACING
 302 #include <linux/ftrace.h>
 303
 304 static void sysrq_ftrace_dump(int key)
 305 {
 306         ftrace_dump(DUMP_ALL);
 307 }
 308 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 309         .handler        = sysrq_ftrace_dump,
 310         .help_msg       = "dump-ftrace-buffer(z)",
 311         .action_msg     = "Dump ftrace buffer",
 312         .enable_mask    = SYSRQ_ENABLE_DUMP,
 313 };
 314 #else
 315 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
 316 #endif
 317
 318 static void sysrq_handle_showmem(int key)
 319 {
 320         show_mem(0);
 321 }
 322 static struct sysrq_key_op sysrq_showmem_op = {
 323         .handler        = sysrq_handle_showmem,
 324         .help_msg       = "show-memory-usage(m)",
 325         .action_msg     = "Show Memory",
 326         .enable_mask    = SYSRQ_ENABLE_DUMP,
 327 };
 328
 329 /*
 330  * Signal sysrq helper function.  Sends a signal to all user processes.
 331  */
 332 static void send_sig_all(int sig)
 333 {
 334         struct task_struct *p;
 335
 336         read_lock(&tasklist_lock);
 337         for_each_process(p) {
 338                 if (p->flags & PF_KTHREAD)
 339                         continue;
 340                 if (is_global_init(p))
 341                         continue;
 342
 343                 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
 344         }
 345         read_unlock(&tasklist_lock);
 346 }
 347
 348 static void sysrq_handle_term(int key)
 349 {
 350         send_sig_all(SIGTERM);
 351         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 352 }
 353 static struct sysrq_key_op sysrq_term_op = {
 354         .handler        = sysrq_handle_term,
 355         .help_msg       = "terminate-all-tasks(e)",
 356         .action_msg     = "Terminate All Tasks",
 357         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 358 };
 359
 360 static void moom_callback(struct work_struct *ignored)
 361 {
 362         const gfp_t gfp_mask = GFP_KERNEL;
 363         struct oom_control oc = {
 364                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 365                 .nodemask = NULL,
 366                 .gfp_mask = gfp_mask,
 367                 .order = -1,
 368         };
 369
 370         mutex_lock(&oom_lock);
 371         if (!out_of_memory(&oc))
 372                 pr_info("OOM request ignored because killer is disabled\n");
 373         mutex_unlock(&oom_lock);
 374 }
 375
 376 static DECLARE_WORK(moom_work, moom_callback);
 377
 378 static void sysrq_handle_moom(int key)
 379 {
 380         schedule_work(&moom_work);
 381 }
 382 static struct sysrq_key_op sysrq_moom_op = {
 383         .handler        = sysrq_handle_moom,
 384         .help_msg       = "memory-full-oom-kill(f)",
 385         .action_msg     = "Manual OOM execution",
 386         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 387 };
 388
 389 #ifdef CONFIG_BLOCK
 390 static void sysrq_handle_thaw(int key)
 391 {
 392         emergency_thaw_all();
 393 }
 394 static struct sysrq_key_op sysrq_thaw_op = {
 395         .handler        = sysrq_handle_thaw,
 396         .help_msg       = "thaw-filesystems(j)",
 397         .action_msg     = "Emergency Thaw of all frozen filesystems",
 398         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 399 };
 400 #endif
 401
 402 static void sysrq_handle_kill(int key)
 403 {
 404         send_sig_all(SIGKILL);
 405         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 406 }
 407 static struct sysrq_key_op sysrq_kill_op = {
 408         .handler        = sysrq_handle_kill,
 409         .help_msg       = "kill-all-tasks(i)",
 410         .action_msg     = "Kill All Tasks",
 411         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 412 };
 413
 414 static void sysrq_handle_unrt(int key)
 415 {
 416         normalize_rt_tasks();
 417 }
 418 static struct sysrq_key_op sysrq_unrt_op = {
 419         .handler        = sysrq_handle_unrt,
 420         .help_msg       = "nice-all-RT-tasks(n)",
 421         .action_msg     = "Nice All RT Tasks",
 422         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 423 };
 424
 425 /* Key Operations table and lock */
 426 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 427
 428 static struct sysrq_key_op *sysrq_key_table[36] = {
 429         &sysrq_loglevel_op,             /* 0 */
 430         &sysrq_loglevel_op,             /* 1 */
 431         &sysrq_loglevel_op,             /* 2 */
 432         &sysrq_loglevel_op,             /* 3 */
 433         &sysrq_loglevel_op,             /* 4 */
 434         &sysrq_loglevel_op,             /* 5 */
 435         &sysrq_loglevel_op,             /* 6 */
 436         &sysrq_loglevel_op,             /* 7 */
 437         &sysrq_loglevel_op,             /* 8 */
 438         &sysrq_loglevel_op,             /* 9 */
 439
 440         /*
 441          * a: Don't use for system provided sysrqs, it is handled specially on
 442          * sparc and will never arrive.
 443          */
 444         NULL,                           /* a */
 445         &sysrq_reboot_op,               /* b */
 446         &sysrq_crash_op,                /* c & ibm_emac driver debug */
 447         &sysrq_showlocks_op,            /* d */
 448         &sysrq_term_op,                 /* e */
 449         &sysrq_moom_op,                 /* f */
 450         /* g: May be registered for the kernel debugger */
 451         NULL,                           /* g */
 452         NULL,                           /* h - reserved for help */
 453         &sysrq_kill_op,                 /* i */
 454 #ifdef CONFIG_BLOCK
 455         &sysrq_thaw_op,                 /* j */
 456 #else
 457         NULL,                           /* j */
 458 #endif
 459         &sysrq_SAK_op,                  /* k */
 460 #ifdef CONFIG_SMP
 461         &sysrq_showallcpus_op,          /* l */
 462 #else
 463         NULL,                           /* l */
 464 #endif
 465         &sysrq_showmem_op,              /* m */
 466         &sysrq_unrt_op,                 /* n */
 467         /* o: This will often be registered as 'Off' at init time */
 468         NULL,                           /* o */
 469         &sysrq_showregs_op,             /* p */
 470         &sysrq_show_timers_op,          /* q */
 471         &sysrq_unraw_op,                /* r */
 472         &sysrq_sync_op,                 /* s */
 473         &sysrq_showstate_op,            /* t */
 474         &sysrq_mountro_op,              /* u */
 475         /* v: May be registered for frame buffer console restore */
 476         NULL,                           /* v */
 477         &sysrq_showstate_blocked_op,    /* w */
 478         /* x: May be registered on mips for TLB dump */
 479         /* x: May be registered on ppc/powerpc for xmon */
 480         /* x: May be registered on sparc64 for global PMU dump */
 481         NULL,                           /* x */
 482         /* y: May be registered on sparc64 for global register dump */
 483         NULL,                           /* y */
 484         &sysrq_ftrace_dump_op,          /* z */
 485 };
 486
 487 /* key2index calculation, -1 on invalid index */
 488 static int sysrq_key_table_key2index(int key)
 489 {
 490         int retval;
 491
 492         if ((key >= '0') && (key <= '9'))
 493                 retval = key - '0';
 494         else if ((key >= 'a') && (key <= 'z'))
 495                 retval = key + 10 - 'a';
 496         else
 497                 retval = -1;
 498         return retval;
 499 }
 500
 501 /*
 502  * get and put functions for the table, exposed to modules.
 503  */
 504 struct sysrq_key_op *__sysrq_get_key_op(int key)
 505 {
 506         struct sysrq_key_op *op_p = NULL;
 507         int i;
 508
 509         i = sysrq_key_table_key2index(key);
 510         if (i != -1)
 511                 op_p = sysrq_key_table[i];
 512
 513         return op_p;
 514 }
 515
 516 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 517 {
 518         int i = sysrq_key_table_key2index(key);
 519
 520         if (i != -1)
 521                 sysrq_key_table[i] = op_p;
 522 }
 523
 524 void __handle_sysrq(int key, bool check_mask)
 525 {
 526         struct sysrq_key_op *op_p;
 527         int orig_log_level;
 528         int i;
 529
 530         rcu_sysrq_start();
 531         rcu_read_lock();
 532         /*
 533          * Raise the apparent loglevel to maximum so that the sysrq header
 534          * is shown to provide the user with positive feedback.  We do not
 535          * simply emit this at KERN_EMERG as that would change message
 536          * routing in the consumers of /proc/kmsg.
 537          */
 538         orig_log_level = console_loglevel;
 539         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 540         pr_info("SysRq : ");
 541
 542         op_p = __sysrq_get_key_op(key);
 543         if (op_p) {
 544                 /*
 545                  * Should we check for enabled operations (/proc/sysrq-trigger
 546                  * should not) and is the invoked operation enabled?
 547                  */
 548                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 549                         pr_cont("%s\n", op_p->action_msg);
 550                         console_loglevel = orig_log_level;
 551                         op_p->handler(key);
 552                 } else {
 553                         pr_cont("This sysrq operation is disabled.\n");
 554                 }
 555         } else {
 556                 pr_cont("HELP : ");
 557                 /* Only print the help msg once per handler */
 558                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 559                         if (sysrq_key_table[i]) {
 560                                 int j;
 561
 562                                 for (j = 0; sysrq_key_table[i] !=
 563                                                 sysrq_key_table[j]; j++)
 564                                         ;
 565                                 if (j != i)
 566                                         continue;
 567                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 568                         }
 569                 }
 570                 pr_cont("\n");
 571                 console_loglevel = orig_log_level;
 572         }
 573         rcu_read_unlock();
 574         rcu_sysrq_end();
 575 }
 576
 577 void handle_sysrq(int key)
 578 {
 579         if (sysrq_on())
 580                 __handle_sysrq(key, true);
 581 }
 582 EXPORT_SYMBOL(handle_sysrq);
 583
 584 #ifdef CONFIG_INPUT
 585 static int sysrq_reset_downtime_ms;
 586
 587 /* Simple translation table for the SysRq keys */
 588 static const unsigned char sysrq_xlate[KEY_CNT] =
 589         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 590         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 591         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 592         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 593         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 594         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 595         "\r\000/";                                      /* 0x60 - 0x6f */
 596
 597 struct sysrq_state {
 598         struct input_handle handle;
 599         struct work_struct reinject_work;
 600         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 601         unsigned int alt;
 602         unsigned int alt_use;
 603         bool active;
 604         bool need_reinject;
 605         bool reinjecting;
 606
 607         /* reset sequence handling */
 608         bool reset_canceled;
 609         bool reset_requested;
 610         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 611         int reset_seq_len;
 612         int reset_seq_cnt;
 613         int reset_seq_version;
 614         struct timer_list keyreset_timer;
 615 };
 616
 617 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 618 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 619 static unsigned int sysrq_reset_seq_len;
 620 static unsigned int sysrq_reset_seq_version = 1;
 621
 622 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 623 {
 624         int i;
 625         unsigned short key;
 626
 627         state->reset_seq_cnt = 0;
 628
 629         for (i = 0; i < sysrq_reset_seq_len; i++) {
 630                 key = sysrq_reset_seq[i];
 631
 632                 if (key == KEY_RESERVED || key > KEY_MAX)
 633                         break;
 634
 635                 __set_bit(key, state->reset_keybit);
 636                 state->reset_seq_len++;
 637
 638                 if (test_bit(key, state->key_down))
 639                         state->reset_seq_cnt++;
 640         }
 641
 642         /* Disable reset until old keys are not released */
 643         state->reset_canceled = state->reset_seq_cnt != 0;
 644
 645         state->reset_seq_version = sysrq_reset_seq_version;
 646 }
 647
 648 static void sysrq_do_reset(unsigned long _state)
 649 {
 650         struct sysrq_state *state = (struct sysrq_state *) _state;
 651
 652         state->reset_requested = true;
 653
 654         sys_sync();
 655         kernel_restart(NULL);
 656 }
 657
 658 static void sysrq_handle_reset_request(struct sysrq_state *state)
 659 {
 660         if (state->reset_requested)
 661                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 662
 663         if (sysrq_reset_downtime_ms)
 664                 mod_timer(&state->keyreset_timer,
 665                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 666         else
 667                 sysrq_do_reset((unsigned long)state);
 668 }
 669
 670 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 671                                         unsigned int code, int value)
 672 {
 673         if (!test_bit(code, state->reset_keybit)) {
 674                 /*
 675                  * Pressing any key _not_ in reset sequence cancels
 676                  * the reset sequence.  Also cancelling the timer in
 677                  * case additional keys were pressed after a reset
 678                  * has been requested.
 679                  */
 680                 if (value && state->reset_seq_cnt) {
 681                         state->reset_canceled = true;
 682                         del_timer(&state->keyreset_timer);
 683                 }
 684         } else if (value == 0) {
 685                 /*
 686                  * Key release - all keys in the reset sequence need
 687                  * to be pressed and held for the reset timeout
 688                  * to hold.
 689                  */
 690                 del_timer(&state->keyreset_timer);
 691
 692                 if (--state->reset_seq_cnt == 0)
 693                         state->reset_canceled = false;
 694         } else if (value == 1) {
 695                 /* key press, not autorepeat */
 696                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 697                     !state->reset_canceled) {
 698                         sysrq_handle_reset_request(state);
 699                 }
 700         }
 701 }
 702
 703 #ifdef CONFIG_OF
 704 static void sysrq_of_get_keyreset_config(void)
 705 {
 706         u32 key;
 707         struct device_node *np;
 708         struct property *prop;
 709         const __be32 *p;
 710
 711         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 712         if (!np) {
 713                 pr_debug("No sysrq node found");
 714                 return;
 715         }
 716
 717         /* Reset in case a __weak definition was present */
 718         sysrq_reset_seq_len = 0;
 719
 720         of_property_for_each_u32(np, "keyset", prop, p, key) {
 721                 if (key == KEY_RESERVED || key > KEY_MAX ||
 722                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 723                         break;
 724
 725                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 726         }
 727
 728         /* Get reset timeout if any. */
 729         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 730 }
 731 #else
 732 static void sysrq_of_get_keyreset_config(void)
 733 {
 734 }
 735 #endif
 736
 737 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 738 {
 739         struct sysrq_state *sysrq =
 740                         container_of(work, struct sysrq_state, reinject_work);
 741         struct input_handle *handle = &sysrq->handle;
 742         unsigned int alt_code = sysrq->alt_use;
 743
 744         if (sysrq->need_reinject) {
 745                 /* we do not want the assignment to be reordered */
 746                 sysrq->reinjecting = true;
 747                 mb();
 748
 749                 /* Simulate press and release of Alt + SysRq */
 750                 input_inject_event(handle, EV_KEY, alt_code, 1);
 751                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 752                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 753
 754                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 755                 input_inject_event(handle, EV_KEY, alt_code, 0);
 756                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 757
 758                 mb();
 759                 sysrq->reinjecting = false;
 760         }
 761 }
 762
 763 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 764                                   unsigned int code, int value)
 765 {
 766         bool was_active = sysrq->active;
 767         bool suppress;
 768
 769         switch (code) {
 770
 771         case KEY_LEFTALT:
 772         case KEY_RIGHTALT:
 773                 if (!value) {
 774                         /* One of ALTs is being released */
 775                         if (sysrq->active && code == sysrq->alt_use)
 776                                 sysrq->active = false;
 777
 778                         sysrq->alt = KEY_RESERVED;
 779
 780                 } else if (value != 2) {
 781                         sysrq->alt = code;
 782                         sysrq->need_reinject = false;
 783                 }
 784                 break;
 785
 786         case KEY_SYSRQ:
 787                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 788                         sysrq->active = true;
 789                         sysrq->alt_use = sysrq->alt;
 790                         /*
 791                          * If nothing else will be pressed we'll need
 792                          * to re-inject Alt-SysRq keysroke.
 793                          */
 794                         sysrq->need_reinject = true;
 795                 }
 796
 797                 /*
 798                  * Pretend that sysrq was never pressed at all. This
 799                  * is needed to properly handle KGDB which will try
 800                  * to release all keys after exiting debugger. If we
 801                  * do not clear key bit it KGDB will end up sending
 802                  * release events for Alt and SysRq, potentially
 803                  * triggering print screen function.
 804                  */
 805                 if (sysrq->active)
 806                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 807
 808                 break;
 809
 810         default:
 811                 if (sysrq->active && value && value != 2) {
 812                         sysrq->need_reinject = false;
 813                         __handle_sysrq(sysrq_xlate[code], true);
 814                 }
 815                 break;
 816         }
 817
 818         suppress = sysrq->active;
 819
 820         if (!sysrq->active) {
 821
 822                 /*
 823                  * See if reset sequence has changed since the last time.
 824                  */
 825                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 826                         sysrq_parse_reset_sequence(sysrq);
 827
 828                 /*
 829                  * If we are not suppressing key presses keep track of
 830                  * keyboard state so we can release keys that have been
 831                  * pressed before entering SysRq mode.
 832                  */
 833                 if (value)
 834                         set_bit(code, sysrq->key_down);
 835                 else
 836                         clear_bit(code, sysrq->key_down);
 837
 838                 if (was_active)
 839                         schedule_work(&sysrq->reinject_work);
 840
 841                 /* Check for reset sequence */
 842                 sysrq_detect_reset_sequence(sysrq, code, value);
 843
 844         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 845                 /*
 846                  * Pass on release events for keys that was pressed before
 847                  * entering SysRq mode.
 848                  */
 849                 suppress = false;
 850         }
 851
 852         return suppress;
 853 }
 854
 855 static bool sysrq_filter(struct input_handle *handle,
 856                          unsigned int type, unsigned int code, int value)
 857 {
 858         struct sysrq_state *sysrq = handle->private;
 859         bool suppress;
 860
 861         /*
 862          * Do not filter anything if we are in the process of re-injecting
 863          * Alt+SysRq combination.
 864          */
 865         if (sysrq->reinjecting)
 866                 return false;
 867
 868         switch (type) {
 869
 870         case EV_SYN:
 871                 suppress = false;
 872                 break;
 873
 874         case EV_KEY:
 875                 suppress = sysrq_handle_keypress(sysrq, code, value);
 876                 break;
 877
 878         default:
 879                 suppress = sysrq->active;
 880                 break;
 881         }
 882
 883         return suppress;
 884 }
 885
 886 static int sysrq_connect(struct input_handler *handler,
 887                          struct input_dev *dev,
 888                          const struct input_device_id *id)
 889 {
 890         struct sysrq_state *sysrq;
 891         int error;
 892
 893         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 894         if (!sysrq)
 895                 return -ENOMEM;
 896
 897         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 898
 899         sysrq->handle.dev = dev;
 900         sysrq->handle.handler = handler;
 901         sysrq->handle.name = "sysrq";
 902         sysrq->handle.private = sysrq;
 903         setup_timer(&sysrq->keyreset_timer,
 904                     sysrq_do_reset, (unsigned long)sysrq);
 905
 906         error = input_register_handle(&sysrq->handle);
 907         if (error) {
 908                 pr_err("Failed to register input sysrq handler, error %d\n",
 909                         error);
 910                 goto err_free;
 911         }
 912
 913         error = input_open_device(&sysrq->handle);
 914         if (error) {
 915                 pr_err("Failed to open input device, error %d\n", error);
 916                 goto err_unregister;
 917         }
 918
 919         return 0;
 920
 921  err_unregister:
 922         input_unregister_handle(&sysrq->handle);
 923  err_free:
 924         kfree(sysrq);
 925         return error;
 926 }
 927
 928 static void sysrq_disconnect(struct input_handle *handle)
 929 {
 930         struct sysrq_state *sysrq = handle->private;
 931
 932         input_close_device(handle);
 933         cancel_work_sync(&sysrq->reinject_work);
 934         del_timer_sync(&sysrq->keyreset_timer);
 935         input_unregister_handle(handle);
 936         kfree(sysrq);
 937 }
 938
 939 /*
 940  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 941  * keyboards have SysRq key predefined and so user may add it to keymap
 942  * later, but we expect all such keyboards to have left alt.
 943  */
 944 static const struct input_device_id sysrq_ids[] = {
 945         {
 946                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 947                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 948                 .evbit = { BIT_MASK(EV_KEY) },
 949                 .keybit = { BIT_MASK(KEY_LEFTALT) },
 950         },
 951         { },
 952 };
 953
 954 static struct input_handler sysrq_handler = {
 955         .filter         = sysrq_filter,
 956         .connect        = sysrq_connect,
 957         .disconnect     = sysrq_disconnect,
 958         .name           = "sysrq",
 959         .id_table       = sysrq_ids,
 960 };
 961
 962 static bool sysrq_handler_registered;
 963
 964 static inline void sysrq_register_handler(void)
 965 {
 966         int error;
 967
 968         sysrq_of_get_keyreset_config();
 969
 970         error = input_register_handler(&sysrq_handler);
 971         if (error)
 972                 pr_err("Failed to register input handler, error %d", error);
 973         else
 974                 sysrq_handler_registered = true;
 975 }
 976
 977 static inline void sysrq_unregister_handler(void)
 978 {
 979         if (sysrq_handler_registered) {
 980                 input_unregister_handler(&sysrq_handler);
 981                 sysrq_handler_registered = false;
 982         }
 983 }
 984
 985 static int sysrq_reset_seq_param_set(const char *buffer,
 986                                      const struct kernel_param *kp)
 987 {
 988         unsigned long val;
 989         int error;
 990
 991         error = kstrtoul(buffer, 0, &val);
 992         if (error < 0)
 993                 return error;
 994
 995         if (val > KEY_MAX)
 996                 return -EINVAL;
 997
 998         *((unsigned short *)kp->arg) = val;
 999         sysrq_reset_seq_version++;
1000
1001         return 0;
1002 }
1003
1004 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1005         .get    = param_get_ushort,
1006         .set    = sysrq_reset_seq_param_set,
1007 };
1008
1009 #define param_check_sysrq_reset_seq(name, p)    \
1010         __param_check(name, p, unsigned short)
1011
1012 /*
1013  * not really modular, but the easiest way to keep compat with existing
1014  * bootargs behaviour is to continue using module_param here.
1015  */
1016 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1017                          &sysrq_reset_seq_len, 0644);
1018
1019 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1020
1021 #else
1022
1023 static inline void sysrq_register_handler(void)
1024 {
1025 }
1026
1027 static inline void sysrq_unregister_handler(void)
1028 {
1029 }
1030
1031 #endif /* CONFIG_INPUT */
1032
1033 int sysrq_toggle_support(int enable_mask)
1034 {
1035         bool was_enabled = sysrq_on();
1036
1037         sysrq_enabled = enable_mask;
1038
1039         if (was_enabled != sysrq_on()) {
1040                 if (sysrq_on())
1041                         sysrq_register_handler();
1042                 else
1043                         sysrq_unregister_handler();
1044         }
1045
1046         return 0;
1047 }
1048
1049 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1050                                 struct sysrq_key_op *remove_op_p)
1051 {
1052         int retval;
1053
1054         spin_lock(&sysrq_key_table_lock);
1055         if (__sysrq_get_key_op(key) == remove_op_p) {
1056                 __sysrq_put_key_op(key, insert_op_p);
1057                 retval = 0;
1058         } else {
1059                 retval = -1;
1060         }
1061         spin_unlock(&sysrq_key_table_lock);
1062
1063         /*
1064          * A concurrent __handle_sysrq either got the old op or the new op.
1065          * Wait for it to go away before returning, so the code for an old
1066          * op is not freed (eg. on module unload) while it is in use.
1067          */
1068         synchronize_rcu();
1069
1070         return retval;
1071 }
1072
1073 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1074 {
1075         return __sysrq_swap_key_ops(key, op_p, NULL);
1076 }
1077 EXPORT_SYMBOL(register_sysrq_key);
1078
1079 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1080 {
1081         return __sysrq_swap_key_ops(key, NULL, op_p);
1082 }
1083 EXPORT_SYMBOL(unregister_sysrq_key);
1084
1085 #ifdef CONFIG_PROC_FS
1086 /*
1087  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1088  */
1089 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1090                                    size_t count, loff_t *ppos)
1091 {
1092         if (count) {
1093                 char c;
1094
1095                 if (get_user(c, buf))
1096                         return -EFAULT;
1097                 __handle_sysrq(c, false);
1098         }
1099
1100         return count;
1101 }
1102
1103 static const struct file_operations proc_sysrq_trigger_operations = {
1104         .write          = write_sysrq_trigger,
1105         .llseek         = noop_llseek,
1106 };
1107
1108 static void sysrq_init_procfs(void)
1109 {
1110         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1111                          &proc_sysrq_trigger_operations))
1112                 pr_err("Failed to register proc interface\n");
1113 }
1114
1115 #else
1116
1117 static inline void sysrq_init_procfs(void)
1118 {
1119 }
1120
1121 #endif /* CONFIG_PROC_FS */
1122
1123 static int __init sysrq_init(void)
1124 {
1125         sysrq_init_procfs();
1126
1127         if (sysrq_on())
1128                 sysrq_register_handler();
1129
1130         return 0;
1131 }
1132 device_initcall(sysrq_init);