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 unsigned short platform_sysrq_reset_seq[] __weak = { KEY_RESERVED };
  59 int sysrq_reset_downtime_ms __weak;
  60
  61 static bool sysrq_on(void)
  62 {
  63         return sysrq_enabled || sysrq_always_enabled;
  64 }
  65
  66 /*
  67  * A value of 1 means 'all', other nonzero values are an op mask:
  68  */
  69 static bool sysrq_on_mask(int mask)
  70 {
  71         return sysrq_always_enabled ||
  72                sysrq_enabled == 1 ||
  73                (sysrq_enabled & mask);
  74 }
  75
  76 static int __init sysrq_always_enabled_setup(char *str)
  77 {
  78         sysrq_always_enabled = true;
  79         pr_info("sysrq always enabled.\n");
  80
  81         return 1;
  82 }
  83
  84 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  85
  86
  87 static void sysrq_handle_loglevel(int key)
  88 {
  89         int i;
  90
  91         i = key - '0';
  92         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
  93         printk("Loglevel set to %d\n", i);
  94         console_loglevel = i;
  95 }
  96 static struct sysrq_key_op sysrq_loglevel_op = {
  97         .handler        = sysrq_handle_loglevel,
  98         .help_msg       = "loglevel(0-9)",
  99         .action_msg     = "Changing Loglevel",
 100         .enable_mask    = SYSRQ_ENABLE_LOG,
 101 };
 102
 103 #ifdef CONFIG_VT
 104 static void sysrq_handle_SAK(int key)
 105 {
 106         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 107         schedule_work(SAK_work);
 108 }
 109 static struct sysrq_key_op sysrq_SAK_op = {
 110         .handler        = sysrq_handle_SAK,
 111         .help_msg       = "sak(k)",
 112         .action_msg     = "SAK",
 113         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 114 };
 115 #else
 116 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
 117 #endif
 118
 119 #ifdef CONFIG_VT
 120 static void sysrq_handle_unraw(int key)
 121 {
 122         vt_reset_unicode(fg_console);
 123 }
 124
 125 static struct sysrq_key_op sysrq_unraw_op = {
 126         .handler        = sysrq_handle_unraw,
 127         .help_msg       = "unraw(r)",
 128         .action_msg     = "Keyboard mode set to system default",
 129         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 130 };
 131 #else
 132 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
 133 #endif /* CONFIG_VT */
 134
 135 static void sysrq_handle_crash(int key)
 136 {
 137         char *killer = NULL;
 138
 139         panic_on_oops = 1;      /* force panic */
 140         wmb();
 141         *killer = 1;
 142 }
 143 static struct sysrq_key_op sysrq_crash_op = {
 144         .handler        = sysrq_handle_crash,
 145         .help_msg       = "crash(c)",
 146         .action_msg     = "Trigger a crash",
 147         .enable_mask    = SYSRQ_ENABLE_DUMP,
 148 };
 149
 150 static void sysrq_handle_reboot(int key)
 151 {
 152         lockdep_off();
 153         local_irq_enable();
 154         emergency_restart();
 155 }
 156 static struct sysrq_key_op sysrq_reboot_op = {
 157         .handler        = sysrq_handle_reboot,
 158         .help_msg       = "reboot(b)",
 159         .action_msg     = "Resetting",
 160         .enable_mask    = SYSRQ_ENABLE_BOOT,
 161 };
 162
 163 static void sysrq_handle_sync(int key)
 164 {
 165         emergency_sync();
 166 }
 167 static struct sysrq_key_op sysrq_sync_op = {
 168         .handler        = sysrq_handle_sync,
 169         .help_msg       = "sync(s)",
 170         .action_msg     = "Emergency Sync",
 171         .enable_mask    = SYSRQ_ENABLE_SYNC,
 172 };
 173
 174 static void sysrq_handle_show_timers(int key)
 175 {
 176         sysrq_timer_list_show();
 177 }
 178
 179 static struct sysrq_key_op sysrq_show_timers_op = {
 180         .handler        = sysrq_handle_show_timers,
 181         .help_msg       = "show-all-timers(q)",
 182         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 183 };
 184
 185 static void sysrq_handle_mountro(int key)
 186 {
 187         emergency_remount();
 188 }
 189 static struct sysrq_key_op sysrq_mountro_op = {
 190         .handler        = sysrq_handle_mountro,
 191         .help_msg       = "unmount(u)",
 192         .action_msg     = "Emergency Remount R/O",
 193         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 194 };
 195
 196 #ifdef CONFIG_LOCKDEP
 197 static void sysrq_handle_showlocks(int key)
 198 {
 199         debug_show_all_locks();
 200 }
 201
 202 static struct sysrq_key_op sysrq_showlocks_op = {
 203         .handler        = sysrq_handle_showlocks,
 204         .help_msg       = "show-all-locks(d)",
 205         .action_msg     = "Show Locks Held",
 206 };
 207 #else
 208 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
 209 #endif
 210
 211 #ifdef CONFIG_SMP
 212 static DEFINE_SPINLOCK(show_lock);
 213
 214 static void showacpu(void *dummy)
 215 {
 216         unsigned long flags;
 217
 218         /* Idle CPUs have no interesting backtrace. */
 219         if (idle_cpu(smp_processor_id()))
 220                 return;
 221
 222         spin_lock_irqsave(&show_lock, flags);
 223         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 224         show_stack(NULL, NULL);
 225         spin_unlock_irqrestore(&show_lock, flags);
 226 }
 227
 228 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 229 {
 230         smp_call_function(showacpu, NULL, 0);
 231 }
 232
 233 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 234
 235 static void sysrq_handle_showallcpus(int key)
 236 {
 237         /*
 238          * Fall back to the workqueue based printing if the
 239          * backtrace printing did not succeed or the
 240          * architecture has no support for it:
 241          */
 242         if (!trigger_all_cpu_backtrace()) {
 243                 struct pt_regs *regs = get_irq_regs();
 244
 245                 if (regs) {
 246                         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 247                         show_regs(regs);
 248                 }
 249                 schedule_work(&sysrq_showallcpus);
 250         }
 251 }
 252
 253 static struct sysrq_key_op sysrq_showallcpus_op = {
 254         .handler        = sysrq_handle_showallcpus,
 255         .help_msg       = "show-backtrace-all-active-cpus(l)",
 256         .action_msg     = "Show backtrace of all active CPUs",
 257         .enable_mask    = SYSRQ_ENABLE_DUMP,
 258 };
 259 #endif
 260
 261 static void sysrq_handle_showregs(int key)
 262 {
 263         struct pt_regs *regs = get_irq_regs();
 264         if (regs)
 265                 show_regs(regs);
 266         perf_event_print_debug();
 267 }
 268 static struct sysrq_key_op sysrq_showregs_op = {
 269         .handler        = sysrq_handle_showregs,
 270         .help_msg       = "show-registers(p)",
 271         .action_msg     = "Show Regs",
 272         .enable_mask    = SYSRQ_ENABLE_DUMP,
 273 };
 274
 275 static void sysrq_handle_showstate(int key)
 276 {
 277         show_state();
 278 }
 279 static struct sysrq_key_op sysrq_showstate_op = {
 280         .handler        = sysrq_handle_showstate,
 281         .help_msg       = "show-task-states(t)",
 282         .action_msg     = "Show State",
 283         .enable_mask    = SYSRQ_ENABLE_DUMP,
 284 };
 285
 286 static void sysrq_handle_showstate_blocked(int key)
 287 {
 288         show_state_filter(TASK_UNINTERRUPTIBLE);
 289 }
 290 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 291         .handler        = sysrq_handle_showstate_blocked,
 292         .help_msg       = "show-blocked-tasks(w)",
 293         .action_msg     = "Show Blocked State",
 294         .enable_mask    = SYSRQ_ENABLE_DUMP,
 295 };
 296
 297 #ifdef CONFIG_TRACING
 298 #include <linux/ftrace.h>
 299
 300 static void sysrq_ftrace_dump(int key)
 301 {
 302         ftrace_dump(DUMP_ALL);
 303 }
 304 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 305         .handler        = sysrq_ftrace_dump,
 306         .help_msg       = "dump-ftrace-buffer(z)",
 307         .action_msg     = "Dump ftrace buffer",
 308         .enable_mask    = SYSRQ_ENABLE_DUMP,
 309 };
 310 #else
 311 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
 312 #endif
 313
 314 static void sysrq_handle_showmem(int key)
 315 {
 316         show_mem(0);
 317 }
 318 static struct sysrq_key_op sysrq_showmem_op = {
 319         .handler        = sysrq_handle_showmem,
 320         .help_msg       = "show-memory-usage(m)",
 321         .action_msg     = "Show Memory",
 322         .enable_mask    = SYSRQ_ENABLE_DUMP,
 323 };
 324
 325 /*
 326  * Signal sysrq helper function.  Sends a signal to all user processes.
 327  */
 328 static void send_sig_all(int sig)
 329 {
 330         struct task_struct *p;
 331
 332         read_lock(&tasklist_lock);
 333         for_each_process(p) {
 334                 if (p->flags & PF_KTHREAD)
 335                         continue;
 336                 if (is_global_init(p))
 337                         continue;
 338
 339                 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
 340         }
 341         read_unlock(&tasklist_lock);
 342 }
 343
 344 static void sysrq_handle_term(int key)
 345 {
 346         send_sig_all(SIGTERM);
 347         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 348 }
 349 static struct sysrq_key_op sysrq_term_op = {
 350         .handler        = sysrq_handle_term,
 351         .help_msg       = "terminate-all-tasks(e)",
 352         .action_msg     = "Terminate All Tasks",
 353         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 354 };
 355
 356 static void moom_callback(struct work_struct *ignored)
 357 {
 358         out_of_memory(node_zonelist(first_memory_node, GFP_KERNEL), GFP_KERNEL,
 359                       0, NULL, true);
 360 }
 361
 362 static DECLARE_WORK(moom_work, moom_callback);
 363
 364 static void sysrq_handle_moom(int key)
 365 {
 366         schedule_work(&moom_work);
 367 }
 368 static struct sysrq_key_op sysrq_moom_op = {
 369         .handler        = sysrq_handle_moom,
 370         .help_msg       = "memory-full-oom-kill(f)",
 371         .action_msg     = "Manual OOM execution",
 372         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 373 };
 374
 375 #ifdef CONFIG_BLOCK
 376 static void sysrq_handle_thaw(int key)
 377 {
 378         emergency_thaw_all();
 379 }
 380 static struct sysrq_key_op sysrq_thaw_op = {
 381         .handler        = sysrq_handle_thaw,
 382         .help_msg       = "thaw-filesystems(j)",
 383         .action_msg     = "Emergency Thaw of all frozen filesystems",
 384         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 385 };
 386 #endif
 387
 388 static void sysrq_handle_kill(int key)
 389 {
 390         send_sig_all(SIGKILL);
 391         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 392 }
 393 static struct sysrq_key_op sysrq_kill_op = {
 394         .handler        = sysrq_handle_kill,
 395         .help_msg       = "kill-all-tasks(i)",
 396         .action_msg     = "Kill All Tasks",
 397         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 398 };
 399
 400 static void sysrq_handle_unrt(int key)
 401 {
 402         normalize_rt_tasks();
 403 }
 404 static struct sysrq_key_op sysrq_unrt_op = {
 405         .handler        = sysrq_handle_unrt,
 406         .help_msg       = "nice-all-RT-tasks(n)",
 407         .action_msg     = "Nice All RT Tasks",
 408         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 409 };
 410
 411 /* Key Operations table and lock */
 412 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 413
 414 static struct sysrq_key_op *sysrq_key_table[36] = {
 415         &sysrq_loglevel_op,             /* 0 */
 416         &sysrq_loglevel_op,             /* 1 */
 417         &sysrq_loglevel_op,             /* 2 */
 418         &sysrq_loglevel_op,             /* 3 */
 419         &sysrq_loglevel_op,             /* 4 */
 420         &sysrq_loglevel_op,             /* 5 */
 421         &sysrq_loglevel_op,             /* 6 */
 422         &sysrq_loglevel_op,             /* 7 */
 423         &sysrq_loglevel_op,             /* 8 */
 424         &sysrq_loglevel_op,             /* 9 */
 425
 426         /*
 427          * a: Don't use for system provided sysrqs, it is handled specially on
 428          * sparc and will never arrive.
 429          */
 430         NULL,                           /* a */
 431         &sysrq_reboot_op,               /* b */
 432         &sysrq_crash_op,                /* c & ibm_emac driver debug */
 433         &sysrq_showlocks_op,            /* d */
 434         &sysrq_term_op,                 /* e */
 435         &sysrq_moom_op,                 /* f */
 436         /* g: May be registered for the kernel debugger */
 437         NULL,                           /* g */
 438         NULL,                           /* h - reserved for help */
 439         &sysrq_kill_op,                 /* i */
 440 #ifdef CONFIG_BLOCK
 441         &sysrq_thaw_op,                 /* j */
 442 #else
 443         NULL,                           /* j */
 444 #endif
 445         &sysrq_SAK_op,                  /* k */
 446 #ifdef CONFIG_SMP
 447         &sysrq_showallcpus_op,          /* l */
 448 #else
 449         NULL,                           /* l */
 450 #endif
 451         &sysrq_showmem_op,              /* m */
 452         &sysrq_unrt_op,                 /* n */
 453         /* o: This will often be registered as 'Off' at init time */
 454         NULL,                           /* o */
 455         &sysrq_showregs_op,             /* p */
 456         &sysrq_show_timers_op,          /* q */
 457         &sysrq_unraw_op,                /* r */
 458         &sysrq_sync_op,                 /* s */
 459         &sysrq_showstate_op,            /* t */
 460         &sysrq_mountro_op,              /* u */
 461         /* v: May be registered for frame buffer console restore */
 462         NULL,                           /* v */
 463         &sysrq_showstate_blocked_op,    /* w */
 464         /* x: May be registered on ppc/powerpc for xmon */
 465         /* x: May be registered on sparc64 for global PMU dump */
 466         NULL,                           /* x */
 467         /* y: May be registered on sparc64 for global register dump */
 468         NULL,                           /* y */
 469         &sysrq_ftrace_dump_op,          /* z */
 470 };
 471
 472 /* key2index calculation, -1 on invalid index */
 473 static int sysrq_key_table_key2index(int key)
 474 {
 475         int retval;
 476
 477         if ((key >= '0') && (key <= '9'))
 478                 retval = key - '0';
 479         else if ((key >= 'a') && (key <= 'z'))
 480                 retval = key + 10 - 'a';
 481         else
 482                 retval = -1;
 483         return retval;
 484 }
 485
 486 /*
 487  * get and put functions for the table, exposed to modules.
 488  */
 489 struct sysrq_key_op *__sysrq_get_key_op(int key)
 490 {
 491         struct sysrq_key_op *op_p = NULL;
 492         int i;
 493
 494         i = sysrq_key_table_key2index(key);
 495         if (i != -1)
 496                 op_p = sysrq_key_table[i];
 497
 498         return op_p;
 499 }
 500
 501 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 502 {
 503         int i = sysrq_key_table_key2index(key);
 504
 505         if (i != -1)
 506                 sysrq_key_table[i] = op_p;
 507 }
 508
 509 void __handle_sysrq(int key, bool check_mask)
 510 {
 511         struct sysrq_key_op *op_p;
 512         int orig_log_level;
 513         int i;
 514
 515         rcu_sysrq_start();
 516         rcu_read_lock();
 517         /*
 518          * Raise the apparent loglevel to maximum so that the sysrq header
 519          * is shown to provide the user with positive feedback.  We do not
 520          * simply emit this at KERN_EMERG as that would change message
 521          * routing in the consumers of /proc/kmsg.
 522          */
 523         orig_log_level = console_loglevel;
 524         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 525         printk(KERN_INFO "SysRq : ");
 526
 527         op_p = __sysrq_get_key_op(key);
 528         if (op_p) {
 529                 /*
 530                  * Should we check for enabled operations (/proc/sysrq-trigger
 531                  * should not) and is the invoked operation enabled?
 532                  */
 533                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 534                         printk("%s\n", op_p->action_msg);
 535                         console_loglevel = orig_log_level;
 536                         op_p->handler(key);
 537                 } else {
 538                         printk("This sysrq operation is disabled.\n");
 539                 }
 540         } else {
 541                 printk("HELP : ");
 542                 /* Only print the help msg once per handler */
 543                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 544                         if (sysrq_key_table[i]) {
 545                                 int j;
 546
 547                                 for (j = 0; sysrq_key_table[i] !=
 548                                                 sysrq_key_table[j]; j++)
 549                                         ;
 550                                 if (j != i)
 551                                         continue;
 552                                 printk("%s ", sysrq_key_table[i]->help_msg);
 553                         }
 554                 }
 555                 printk("\n");
 556                 console_loglevel = orig_log_level;
 557         }
 558         rcu_read_unlock();
 559         rcu_sysrq_end();
 560 }
 561
 562 void handle_sysrq(int key)
 563 {
 564         if (sysrq_on())
 565                 __handle_sysrq(key, true);
 566 }
 567 EXPORT_SYMBOL(handle_sysrq);
 568
 569 #ifdef CONFIG_INPUT
 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         unsigned short key;
 951         int error;
 952         int i;
 953
 954         /* First check if a __weak interface was instantiated. */
 955         for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
 956                 key = platform_sysrq_reset_seq[i];
 957                 if (key == KEY_RESERVED || key > KEY_MAX)
 958                         break;
 959
 960                 sysrq_reset_seq[sysrq_reset_seq_len++] = key;
 961         }
 962
 963         /*
 964          * DT configuration takes precedence over anything that would
 965          * have been defined via the __weak interface.
 966          */
 967         sysrq_of_get_keyreset_config();
 968
 969         error = input_register_handler(&sysrq_handler);
 970         if (error)
 971                 pr_err("Failed to register input handler, error %d", error);
 972         else
 973                 sysrq_handler_registered = true;
 974 }
 975
 976 static inline void sysrq_unregister_handler(void)
 977 {
 978         if (sysrq_handler_registered) {
 979                 input_unregister_handler(&sysrq_handler);
 980                 sysrq_handler_registered = false;
 981         }
 982 }
 983
 984 static int sysrq_reset_seq_param_set(const char *buffer,
 985                                      const struct kernel_param *kp)
 986 {
 987         unsigned long val;
 988         int error;
 989
 990         error = kstrtoul(buffer, 0, &val);
 991         if (error < 0)
 992                 return error;
 993
 994         if (val > KEY_MAX)
 995                 return -EINVAL;
 996
 997         *((unsigned short *)kp->arg) = val;
 998         sysrq_reset_seq_version++;
 999
1000         return 0;
1001 }
1002
1003 static struct kernel_param_ops param_ops_sysrq_reset_seq = {
1004         .get    = param_get_ushort,
1005         .set    = sysrq_reset_seq_param_set,
1006 };
1007
1008 #define param_check_sysrq_reset_seq(name, p)    \
1009         __param_check(name, p, unsigned short)
1010
1011 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1012                          &sysrq_reset_seq_len, 0644);
1013
1014 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1015
1016 #else
1017
1018 static inline void sysrq_register_handler(void)
1019 {
1020 }
1021
1022 static inline void sysrq_unregister_handler(void)
1023 {
1024 }
1025
1026 #endif /* CONFIG_INPUT */
1027
1028 int sysrq_toggle_support(int enable_mask)
1029 {
1030         bool was_enabled = sysrq_on();
1031
1032         sysrq_enabled = enable_mask;
1033
1034         if (was_enabled != sysrq_on()) {
1035                 if (sysrq_on())
1036                         sysrq_register_handler();
1037                 else
1038                         sysrq_unregister_handler();
1039         }
1040
1041         return 0;
1042 }
1043
1044 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1045                                 struct sysrq_key_op *remove_op_p)
1046 {
1047         int retval;
1048
1049         spin_lock(&sysrq_key_table_lock);
1050         if (__sysrq_get_key_op(key) == remove_op_p) {
1051                 __sysrq_put_key_op(key, insert_op_p);
1052                 retval = 0;
1053         } else {
1054                 retval = -1;
1055         }
1056         spin_unlock(&sysrq_key_table_lock);
1057
1058         /*
1059          * A concurrent __handle_sysrq either got the old op or the new op.
1060          * Wait for it to go away before returning, so the code for an old
1061          * op is not freed (eg. on module unload) while it is in use.
1062          */
1063         synchronize_rcu();
1064
1065         return retval;
1066 }
1067
1068 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1069 {
1070         return __sysrq_swap_key_ops(key, op_p, NULL);
1071 }
1072 EXPORT_SYMBOL(register_sysrq_key);
1073
1074 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1075 {
1076         return __sysrq_swap_key_ops(key, NULL, op_p);
1077 }
1078 EXPORT_SYMBOL(unregister_sysrq_key);
1079
1080 #ifdef CONFIG_PROC_FS
1081 /*
1082  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1083  */
1084 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1085                                    size_t count, loff_t *ppos)
1086 {
1087         if (count) {
1088                 char c;
1089
1090                 if (get_user(c, buf))
1091                         return -EFAULT;
1092                 __handle_sysrq(c, false);
1093         }
1094
1095         return count;
1096 }
1097
1098 static const struct file_operations proc_sysrq_trigger_operations = {
1099         .write          = write_sysrq_trigger,
1100         .llseek         = noop_llseek,
1101 };
1102
1103 static void sysrq_init_procfs(void)
1104 {
1105         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1106                          &proc_sysrq_trigger_operations))
1107                 pr_err("Failed to register proc interface\n");
1108 }
1109
1110 #else
1111
1112 static inline void sysrq_init_procfs(void)
1113 {
1114 }
1115
1116 #endif /* CONFIG_PROC_FS */
1117
1118 static int __init sysrq_init(void)
1119 {
1120         sysrq_init_procfs();
1121
1122         if (sysrq_on())
1123                 sysrq_register_handler();
1124
1125         return 0;
1126 }
1127 module_init(sysrq_init);