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         const gfp_t gfp_mask = GFP_KERNEL;
 357         struct oom_control oc = {
 358                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 359                 .nodemask = NULL,
 360                 .gfp_mask = gfp_mask,
 361                 .order = 0,
 362                 .force_kill = true,
 363         };
 364
 365         mutex_lock(&oom_lock);
 366         if (!out_of_memory(&oc))
 367                 pr_info("OOM request ignored because killer is disabled\n");
 368         mutex_unlock(&oom_lock);
 369 }
 370
 371 static DECLARE_WORK(moom_work, moom_callback);
 372
 373 static void sysrq_handle_moom(int key)
 374 {
 375         schedule_work(&moom_work);
 376 }
 377 static struct sysrq_key_op sysrq_moom_op = {
 378         .handler        = sysrq_handle_moom,
 379         .help_msg       = "memory-full-oom-kill(f)",
 380         .action_msg     = "Manual OOM execution",
 381         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 382 };
 383
 384 #ifdef CONFIG_BLOCK
 385 static void sysrq_handle_thaw(int key)
 386 {
 387         emergency_thaw_all();
 388 }
 389 static struct sysrq_key_op sysrq_thaw_op = {
 390         .handler        = sysrq_handle_thaw,
 391         .help_msg       = "thaw-filesystems(j)",
 392         .action_msg     = "Emergency Thaw of all frozen filesystems",
 393         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 394 };
 395 #endif
 396
 397 static void sysrq_handle_kill(int key)
 398 {
 399         send_sig_all(SIGKILL);
 400         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 401 }
 402 static struct sysrq_key_op sysrq_kill_op = {
 403         .handler        = sysrq_handle_kill,
 404         .help_msg       = "kill-all-tasks(i)",
 405         .action_msg     = "Kill All Tasks",
 406         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 407 };
 408
 409 static void sysrq_handle_unrt(int key)
 410 {
 411         normalize_rt_tasks();
 412 }
 413 static struct sysrq_key_op sysrq_unrt_op = {
 414         .handler        = sysrq_handle_unrt,
 415         .help_msg       = "nice-all-RT-tasks(n)",
 416         .action_msg     = "Nice All RT Tasks",
 417         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 418 };
 419
 420 /* Key Operations table and lock */
 421 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 422
 423 static struct sysrq_key_op *sysrq_key_table[36] = {
 424         &sysrq_loglevel_op,             /* 0 */
 425         &sysrq_loglevel_op,             /* 1 */
 426         &sysrq_loglevel_op,             /* 2 */
 427         &sysrq_loglevel_op,             /* 3 */
 428         &sysrq_loglevel_op,             /* 4 */
 429         &sysrq_loglevel_op,             /* 5 */
 430         &sysrq_loglevel_op,             /* 6 */
 431         &sysrq_loglevel_op,             /* 7 */
 432         &sysrq_loglevel_op,             /* 8 */
 433         &sysrq_loglevel_op,             /* 9 */
 434
 435         /*
 436          * a: Don't use for system provided sysrqs, it is handled specially on
 437          * sparc and will never arrive.
 438          */
 439         NULL,                           /* a */
 440         &sysrq_reboot_op,               /* b */
 441         &sysrq_crash_op,                /* c & ibm_emac driver debug */
 442         &sysrq_showlocks_op,            /* d */
 443         &sysrq_term_op,                 /* e */
 444         &sysrq_moom_op,                 /* f */
 445         /* g: May be registered for the kernel debugger */
 446         NULL,                           /* g */
 447         NULL,                           /* h - reserved for help */
 448         &sysrq_kill_op,                 /* i */
 449 #ifdef CONFIG_BLOCK
 450         &sysrq_thaw_op,                 /* j */
 451 #else
 452         NULL,                           /* j */
 453 #endif
 454         &sysrq_SAK_op,                  /* k */
 455 #ifdef CONFIG_SMP
 456         &sysrq_showallcpus_op,          /* l */
 457 #else
 458         NULL,                           /* l */
 459 #endif
 460         &sysrq_showmem_op,              /* m */
 461         &sysrq_unrt_op,                 /* n */
 462         /* o: This will often be registered as 'Off' at init time */
 463         NULL,                           /* o */
 464         &sysrq_showregs_op,             /* p */
 465         &sysrq_show_timers_op,          /* q */
 466         &sysrq_unraw_op,                /* r */
 467         &sysrq_sync_op,                 /* s */
 468         &sysrq_showstate_op,            /* t */
 469         &sysrq_mountro_op,              /* u */
 470         /* v: May be registered for frame buffer console restore */
 471         NULL,                           /* v */
 472         &sysrq_showstate_blocked_op,    /* w */
 473         /* x: May be registered on mips for TLB dump */
 474         /* x: May be registered on ppc/powerpc for xmon */
 475         /* x: May be registered on sparc64 for global PMU dump */
 476         NULL,                           /* x */
 477         /* y: May be registered on sparc64 for global register dump */
 478         NULL,                           /* y */
 479         &sysrq_ftrace_dump_op,          /* z */
 480 };
 481
 482 /* key2index calculation, -1 on invalid index */
 483 static int sysrq_key_table_key2index(int key)
 484 {
 485         int retval;
 486
 487         if ((key >= '0') && (key <= '9'))
 488                 retval = key - '0';
 489         else if ((key >= 'a') && (key <= 'z'))
 490                 retval = key + 10 - 'a';
 491         else
 492                 retval = -1;
 493         return retval;
 494 }
 495
 496 /*
 497  * get and put functions for the table, exposed to modules.
 498  */
 499 struct sysrq_key_op *__sysrq_get_key_op(int key)
 500 {
 501         struct sysrq_key_op *op_p = NULL;
 502         int i;
 503
 504         i = sysrq_key_table_key2index(key);
 505         if (i != -1)
 506                 op_p = sysrq_key_table[i];
 507
 508         return op_p;
 509 }
 510
 511 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 512 {
 513         int i = sysrq_key_table_key2index(key);
 514
 515         if (i != -1)
 516                 sysrq_key_table[i] = op_p;
 517 }
 518
 519 void __handle_sysrq(int key, bool check_mask)
 520 {
 521         struct sysrq_key_op *op_p;
 522         int orig_log_level;
 523         int i;
 524
 525         rcu_sysrq_start();
 526         rcu_read_lock();
 527         /*
 528          * Raise the apparent loglevel to maximum so that the sysrq header
 529          * is shown to provide the user with positive feedback.  We do not
 530          * simply emit this at KERN_EMERG as that would change message
 531          * routing in the consumers of /proc/kmsg.
 532          */
 533         orig_log_level = console_loglevel;
 534         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 535         pr_info("SysRq : ");
 536
 537         op_p = __sysrq_get_key_op(key);
 538         if (op_p) {
 539                 /*
 540                  * Should we check for enabled operations (/proc/sysrq-trigger
 541                  * should not) and is the invoked operation enabled?
 542                  */
 543                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 544                         pr_cont("%s\n", op_p->action_msg);
 545                         console_loglevel = orig_log_level;
 546                         op_p->handler(key);
 547                 } else {
 548                         pr_cont("This sysrq operation is disabled.\n");
 549                 }
 550         } else {
 551                 pr_cont("HELP : ");
 552                 /* Only print the help msg once per handler */
 553                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 554                         if (sysrq_key_table[i]) {
 555                                 int j;
 556
 557                                 for (j = 0; sysrq_key_table[i] !=
 558                                                 sysrq_key_table[j]; j++)
 559                                         ;
 560                                 if (j != i)
 561                                         continue;
 562                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 563                         }
 564                 }
 565                 pr_cont("\n");
 566                 console_loglevel = orig_log_level;
 567         }
 568         rcu_read_unlock();
 569         rcu_sysrq_end();
 570 }
 571
 572 void handle_sysrq(int key)
 573 {
 574         if (sysrq_on())
 575                 __handle_sysrq(key, true);
 576 }
 577 EXPORT_SYMBOL(handle_sysrq);
 578
 579 #ifdef CONFIG_INPUT
 580 static int sysrq_reset_downtime_ms;
 581
 582 /* Simple translation table for the SysRq keys */
 583 static const unsigned char sysrq_xlate[KEY_CNT] =
 584         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 585         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 586         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 587         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 588         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 589         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 590         "\r\000/";                                      /* 0x60 - 0x6f */
 591
 592 struct sysrq_state {
 593         struct input_handle handle;
 594         struct work_struct reinject_work;
 595         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 596         unsigned int alt;
 597         unsigned int alt_use;
 598         bool active;
 599         bool need_reinject;
 600         bool reinjecting;
 601
 602         /* reset sequence handling */
 603         bool reset_canceled;
 604         bool reset_requested;
 605         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 606         int reset_seq_len;
 607         int reset_seq_cnt;
 608         int reset_seq_version;
 609         struct timer_list keyreset_timer;
 610 };
 611
 612 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 613 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 614 static unsigned int sysrq_reset_seq_len;
 615 static unsigned int sysrq_reset_seq_version = 1;
 616
 617 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 618 {
 619         int i;
 620         unsigned short key;
 621
 622         state->reset_seq_cnt = 0;
 623
 624         for (i = 0; i < sysrq_reset_seq_len; i++) {
 625                 key = sysrq_reset_seq[i];
 626
 627                 if (key == KEY_RESERVED || key > KEY_MAX)
 628                         break;
 629
 630                 __set_bit(key, state->reset_keybit);
 631                 state->reset_seq_len++;
 632
 633                 if (test_bit(key, state->key_down))
 634                         state->reset_seq_cnt++;
 635         }
 636
 637         /* Disable reset until old keys are not released */
 638         state->reset_canceled = state->reset_seq_cnt != 0;
 639
 640         state->reset_seq_version = sysrq_reset_seq_version;
 641 }
 642
 643 static void sysrq_do_reset(unsigned long _state)
 644 {
 645         struct sysrq_state *state = (struct sysrq_state *) _state;
 646
 647         state->reset_requested = true;
 648
 649         sys_sync();
 650         kernel_restart(NULL);
 651 }
 652
 653 static void sysrq_handle_reset_request(struct sysrq_state *state)
 654 {
 655         if (state->reset_requested)
 656                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 657
 658         if (sysrq_reset_downtime_ms)
 659                 mod_timer(&state->keyreset_timer,
 660                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 661         else
 662                 sysrq_do_reset((unsigned long)state);
 663 }
 664
 665 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 666                                         unsigned int code, int value)
 667 {
 668         if (!test_bit(code, state->reset_keybit)) {
 669                 /*
 670                  * Pressing any key _not_ in reset sequence cancels
 671                  * the reset sequence.  Also cancelling the timer in
 672                  * case additional keys were pressed after a reset
 673                  * has been requested.
 674                  */
 675                 if (value && state->reset_seq_cnt) {
 676                         state->reset_canceled = true;
 677                         del_timer(&state->keyreset_timer);
 678                 }
 679         } else if (value == 0) {
 680                 /*
 681                  * Key release - all keys in the reset sequence need
 682                  * to be pressed and held for the reset timeout
 683                  * to hold.
 684                  */
 685                 del_timer(&state->keyreset_timer);
 686
 687                 if (--state->reset_seq_cnt == 0)
 688                         state->reset_canceled = false;
 689         } else if (value == 1) {
 690                 /* key press, not autorepeat */
 691                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 692                     !state->reset_canceled) {
 693                         sysrq_handle_reset_request(state);
 694                 }
 695         }
 696 }
 697
 698 #ifdef CONFIG_OF
 699 static void sysrq_of_get_keyreset_config(void)
 700 {
 701         u32 key;
 702         struct device_node *np;
 703         struct property *prop;
 704         const __be32 *p;
 705
 706         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 707         if (!np) {
 708                 pr_debug("No sysrq node found");
 709                 return;
 710         }
 711
 712         /* Reset in case a __weak definition was present */
 713         sysrq_reset_seq_len = 0;
 714
 715         of_property_for_each_u32(np, "keyset", prop, p, key) {
 716                 if (key == KEY_RESERVED || key > KEY_MAX ||
 717                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 718                         break;
 719
 720                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 721         }
 722
 723         /* Get reset timeout if any. */
 724         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 725 }
 726 #else
 727 static void sysrq_of_get_keyreset_config(void)
 728 {
 729 }
 730 #endif
 731
 732 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 733 {
 734         struct sysrq_state *sysrq =
 735                         container_of(work, struct sysrq_state, reinject_work);
 736         struct input_handle *handle = &sysrq->handle;
 737         unsigned int alt_code = sysrq->alt_use;
 738
 739         if (sysrq->need_reinject) {
 740                 /* we do not want the assignment to be reordered */
 741                 sysrq->reinjecting = true;
 742                 mb();
 743
 744                 /* Simulate press and release of Alt + SysRq */
 745                 input_inject_event(handle, EV_KEY, alt_code, 1);
 746                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 747                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 748
 749                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 750                 input_inject_event(handle, EV_KEY, alt_code, 0);
 751                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 752
 753                 mb();
 754                 sysrq->reinjecting = false;
 755         }
 756 }
 757
 758 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 759                                   unsigned int code, int value)
 760 {
 761         bool was_active = sysrq->active;
 762         bool suppress;
 763
 764         switch (code) {
 765
 766         case KEY_LEFTALT:
 767         case KEY_RIGHTALT:
 768                 if (!value) {
 769                         /* One of ALTs is being released */
 770                         if (sysrq->active && code == sysrq->alt_use)
 771                                 sysrq->active = false;
 772
 773                         sysrq->alt = KEY_RESERVED;
 774
 775                 } else if (value != 2) {
 776                         sysrq->alt = code;
 777                         sysrq->need_reinject = false;
 778                 }
 779                 break;
 780
 781         case KEY_SYSRQ:
 782                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 783                         sysrq->active = true;
 784                         sysrq->alt_use = sysrq->alt;
 785                         /*
 786                          * If nothing else will be pressed we'll need
 787                          * to re-inject Alt-SysRq keysroke.
 788                          */
 789                         sysrq->need_reinject = true;
 790                 }
 791
 792                 /*
 793                  * Pretend that sysrq was never pressed at all. This
 794                  * is needed to properly handle KGDB which will try
 795                  * to release all keys after exiting debugger. If we
 796                  * do not clear key bit it KGDB will end up sending
 797                  * release events for Alt and SysRq, potentially
 798                  * triggering print screen function.
 799                  */
 800                 if (sysrq->active)
 801                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 802
 803                 break;
 804
 805         default:
 806                 if (sysrq->active && value && value != 2) {
 807                         sysrq->need_reinject = false;
 808                         __handle_sysrq(sysrq_xlate[code], true);
 809                 }
 810                 break;
 811         }
 812
 813         suppress = sysrq->active;
 814
 815         if (!sysrq->active) {
 816
 817                 /*
 818                  * See if reset sequence has changed since the last time.
 819                  */
 820                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 821                         sysrq_parse_reset_sequence(sysrq);
 822
 823                 /*
 824                  * If we are not suppressing key presses keep track of
 825                  * keyboard state so we can release keys that have been
 826                  * pressed before entering SysRq mode.
 827                  */
 828                 if (value)
 829                         set_bit(code, sysrq->key_down);
 830                 else
 831                         clear_bit(code, sysrq->key_down);
 832
 833                 if (was_active)
 834                         schedule_work(&sysrq->reinject_work);
 835
 836                 /* Check for reset sequence */
 837                 sysrq_detect_reset_sequence(sysrq, code, value);
 838
 839         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 840                 /*
 841                  * Pass on release events for keys that was pressed before
 842                  * entering SysRq mode.
 843                  */
 844                 suppress = false;
 845         }
 846
 847         return suppress;
 848 }
 849
 850 static bool sysrq_filter(struct input_handle *handle,
 851                          unsigned int type, unsigned int code, int value)
 852 {
 853         struct sysrq_state *sysrq = handle->private;
 854         bool suppress;
 855
 856         /*
 857          * Do not filter anything if we are in the process of re-injecting
 858          * Alt+SysRq combination.
 859          */
 860         if (sysrq->reinjecting)
 861                 return false;
 862
 863         switch (type) {
 864
 865         case EV_SYN:
 866                 suppress = false;
 867                 break;
 868
 869         case EV_KEY:
 870                 suppress = sysrq_handle_keypress(sysrq, code, value);
 871                 break;
 872
 873         default:
 874                 suppress = sysrq->active;
 875                 break;
 876         }
 877
 878         return suppress;
 879 }
 880
 881 static int sysrq_connect(struct input_handler *handler,
 882                          struct input_dev *dev,
 883                          const struct input_device_id *id)
 884 {
 885         struct sysrq_state *sysrq;
 886         int error;
 887
 888         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 889         if (!sysrq)
 890                 return -ENOMEM;
 891
 892         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 893
 894         sysrq->handle.dev = dev;
 895         sysrq->handle.handler = handler;
 896         sysrq->handle.name = "sysrq";
 897         sysrq->handle.private = sysrq;
 898         setup_timer(&sysrq->keyreset_timer,
 899                     sysrq_do_reset, (unsigned long)sysrq);
 900
 901         error = input_register_handle(&sysrq->handle);
 902         if (error) {
 903                 pr_err("Failed to register input sysrq handler, error %d\n",
 904                         error);
 905                 goto err_free;
 906         }
 907
 908         error = input_open_device(&sysrq->handle);
 909         if (error) {
 910                 pr_err("Failed to open input device, error %d\n", error);
 911                 goto err_unregister;
 912         }
 913
 914         return 0;
 915
 916  err_unregister:
 917         input_unregister_handle(&sysrq->handle);
 918  err_free:
 919         kfree(sysrq);
 920         return error;
 921 }
 922
 923 static void sysrq_disconnect(struct input_handle *handle)
 924 {
 925         struct sysrq_state *sysrq = handle->private;
 926
 927         input_close_device(handle);
 928         cancel_work_sync(&sysrq->reinject_work);
 929         del_timer_sync(&sysrq->keyreset_timer);
 930         input_unregister_handle(handle);
 931         kfree(sysrq);
 932 }
 933
 934 /*
 935  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 936  * keyboards have SysRq key predefined and so user may add it to keymap
 937  * later, but we expect all such keyboards to have left alt.
 938  */
 939 static const struct input_device_id sysrq_ids[] = {
 940         {
 941                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 942                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 943                 .evbit = { BIT_MASK(EV_KEY) },
 944                 .keybit = { BIT_MASK(KEY_LEFTALT) },
 945         },
 946         { },
 947 };
 948
 949 static struct input_handler sysrq_handler = {
 950         .filter         = sysrq_filter,
 951         .connect        = sysrq_connect,
 952         .disconnect     = sysrq_disconnect,
 953         .name           = "sysrq",
 954         .id_table       = sysrq_ids,
 955 };
 956
 957 static bool sysrq_handler_registered;
 958
 959 static inline void sysrq_register_handler(void)
 960 {
 961         int error;
 962
 963         sysrq_of_get_keyreset_config();
 964
 965         error = input_register_handler(&sysrq_handler);
 966         if (error)
 967                 pr_err("Failed to register input handler, error %d", error);
 968         else
 969                 sysrq_handler_registered = true;
 970 }
 971
 972 static inline void sysrq_unregister_handler(void)
 973 {
 974         if (sysrq_handler_registered) {
 975                 input_unregister_handler(&sysrq_handler);
 976                 sysrq_handler_registered = false;
 977         }
 978 }
 979
 980 static int sysrq_reset_seq_param_set(const char *buffer,
 981                                      const struct kernel_param *kp)
 982 {
 983         unsigned long val;
 984         int error;
 985
 986         error = kstrtoul(buffer, 0, &val);
 987         if (error < 0)
 988                 return error;
 989
 990         if (val > KEY_MAX)
 991                 return -EINVAL;
 992
 993         *((unsigned short *)kp->arg) = val;
 994         sysrq_reset_seq_version++;
 995
 996         return 0;
 997 }
 998
 999 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1000         .get    = param_get_ushort,
1001         .set    = sysrq_reset_seq_param_set,
1002 };
1003
1004 #define param_check_sysrq_reset_seq(name, p)    \
1005         __param_check(name, p, unsigned short)
1006
1007 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1008                          &sysrq_reset_seq_len, 0644);
1009
1010 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1011
1012 #else
1013
1014 static inline void sysrq_register_handler(void)
1015 {
1016 }
1017
1018 static inline void sysrq_unregister_handler(void)
1019 {
1020 }
1021
1022 #endif /* CONFIG_INPUT */
1023
1024 int sysrq_toggle_support(int enable_mask)
1025 {
1026         bool was_enabled = sysrq_on();
1027
1028         sysrq_enabled = enable_mask;
1029
1030         if (was_enabled != sysrq_on()) {
1031                 if (sysrq_on())
1032                         sysrq_register_handler();
1033                 else
1034                         sysrq_unregister_handler();
1035         }
1036
1037         return 0;
1038 }
1039
1040 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1041                                 struct sysrq_key_op *remove_op_p)
1042 {
1043         int retval;
1044
1045         spin_lock(&sysrq_key_table_lock);
1046         if (__sysrq_get_key_op(key) == remove_op_p) {
1047                 __sysrq_put_key_op(key, insert_op_p);
1048                 retval = 0;
1049         } else {
1050                 retval = -1;
1051         }
1052         spin_unlock(&sysrq_key_table_lock);
1053
1054         /*
1055          * A concurrent __handle_sysrq either got the old op or the new op.
1056          * Wait for it to go away before returning, so the code for an old
1057          * op is not freed (eg. on module unload) while it is in use.
1058          */
1059         synchronize_rcu();
1060
1061         return retval;
1062 }
1063
1064 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1065 {
1066         return __sysrq_swap_key_ops(key, op_p, NULL);
1067 }
1068 EXPORT_SYMBOL(register_sysrq_key);
1069
1070 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1071 {
1072         return __sysrq_swap_key_ops(key, NULL, op_p);
1073 }
1074 EXPORT_SYMBOL(unregister_sysrq_key);
1075
1076 #ifdef CONFIG_PROC_FS
1077 /*
1078  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1079  */
1080 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1081                                    size_t count, loff_t *ppos)
1082 {
1083         if (count) {
1084                 char c;
1085
1086                 if (get_user(c, buf))
1087                         return -EFAULT;
1088                 __handle_sysrq(c, false);
1089         }
1090
1091         return count;
1092 }
1093
1094 static const struct file_operations proc_sysrq_trigger_operations = {
1095         .write          = write_sysrq_trigger,
1096         .llseek         = noop_llseek,
1097 };
1098
1099 static void sysrq_init_procfs(void)
1100 {
1101         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1102                          &proc_sysrq_trigger_operations))
1103                 pr_err("Failed to register proc interface\n");
1104 }
1105
1106 #else
1107
1108 static inline void sysrq_init_procfs(void)
1109 {
1110 }
1111
1112 #endif /* CONFIG_PROC_FS */
1113
1114 static int __init sysrq_init(void)
1115 {
1116         sysrq_init_procfs();
1117
1118         if (sysrq_on())
1119                 sysrq_register_handler();
1120
1121         return 0;
1122 }
1123 module_init(sysrq_init);