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