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 mips for TLB dump */
 467         /* x: May be registered on ppc/powerpc for xmon */
 468         /* x: May be registered on sparc64 for global PMU dump */
 469         NULL,                           /* x */
 470         /* y: May be registered on sparc64 for global register dump */
 471         NULL,                           /* y */
 472         &sysrq_ftrace_dump_op,          /* z */
 473 };
 474
 475 /* key2index calculation, -1 on invalid index */
 476 static int sysrq_key_table_key2index(int key)
 477 {
 478         int retval;
 479
 480         if ((key >= '0') && (key <= '9'))
 481                 retval = key - '0';
 482         else if ((key >= 'a') && (key <= 'z'))
 483                 retval = key + 10 - 'a';
 484         else
 485                 retval = -1;
 486         return retval;
 487 }
 488
 489 /*
 490  * get and put functions for the table, exposed to modules.
 491  */
 492 struct sysrq_key_op *__sysrq_get_key_op(int key)
 493 {
 494         struct sysrq_key_op *op_p = NULL;
 495         int i;
 496
 497         i = sysrq_key_table_key2index(key);
 498         if (i != -1)
 499                 op_p = sysrq_key_table[i];
 500
 501         return op_p;
 502 }
 503
 504 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 505 {
 506         int i = sysrq_key_table_key2index(key);
 507
 508         if (i != -1)
 509                 sysrq_key_table[i] = op_p;
 510 }
 511
 512 void __handle_sysrq(int key, bool check_mask)
 513 {
 514         struct sysrq_key_op *op_p;
 515         int orig_log_level;
 516         int i;
 517
 518         rcu_sysrq_start();
 519         rcu_read_lock();
 520         /*
 521          * Raise the apparent loglevel to maximum so that the sysrq header
 522          * is shown to provide the user with positive feedback.  We do not
 523          * simply emit this at KERN_EMERG as that would change message
 524          * routing in the consumers of /proc/kmsg.
 525          */
 526         orig_log_level = console_loglevel;
 527         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 528         pr_info("SysRq : ");
 529
 530         op_p = __sysrq_get_key_op(key);
 531         if (op_p) {
 532                 /*
 533                  * Should we check for enabled operations (/proc/sysrq-trigger
 534                  * should not) and is the invoked operation enabled?
 535                  */
 536                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 537                         pr_cont("%s\n", op_p->action_msg);
 538                         console_loglevel = orig_log_level;
 539                         op_p->handler(key);
 540                 } else {
 541                         pr_cont("This sysrq operation is disabled.\n");
 542                 }
 543         } else {
 544                 pr_cont("HELP : ");
 545                 /* Only print the help msg once per handler */
 546                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 547                         if (sysrq_key_table[i]) {
 548                                 int j;
 549
 550                                 for (j = 0; sysrq_key_table[i] !=
 551                                                 sysrq_key_table[j]; j++)
 552                                         ;
 553                                 if (j != i)
 554                                         continue;
 555                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 556                         }
 557                 }
 558                 pr_cont("\n");
 559                 console_loglevel = orig_log_level;
 560         }
 561         rcu_read_unlock();
 562         rcu_sysrq_end();
 563 }
 564
 565 void handle_sysrq(int key)
 566 {
 567         if (sysrq_on())
 568                 __handle_sysrq(key, true);
 569 }
 570 EXPORT_SYMBOL(handle_sysrq);
 571
 572 #ifdef CONFIG_INPUT
 573
 574 /* Simple translation table for the SysRq keys */
 575 static const unsigned char sysrq_xlate[KEY_CNT] =
 576         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 577         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 578         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 579         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 580         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 581         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 582         "\r\000/";                                      /* 0x60 - 0x6f */
 583
 584 struct sysrq_state {
 585         struct input_handle handle;
 586         struct work_struct reinject_work;
 587         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 588         unsigned int alt;
 589         unsigned int alt_use;
 590         bool active;
 591         bool need_reinject;
 592         bool reinjecting;
 593
 594         /* reset sequence handling */
 595         bool reset_canceled;
 596         bool reset_requested;
 597         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 598         int reset_seq_len;
 599         int reset_seq_cnt;
 600         int reset_seq_version;
 601         struct timer_list keyreset_timer;
 602 };
 603
 604 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 605 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 606 static unsigned int sysrq_reset_seq_len;
 607 static unsigned int sysrq_reset_seq_version = 1;
 608
 609 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 610 {
 611         int i;
 612         unsigned short key;
 613
 614         state->reset_seq_cnt = 0;
 615
 616         for (i = 0; i < sysrq_reset_seq_len; i++) {
 617                 key = sysrq_reset_seq[i];
 618
 619                 if (key == KEY_RESERVED || key > KEY_MAX)
 620                         break;
 621
 622                 __set_bit(key, state->reset_keybit);
 623                 state->reset_seq_len++;
 624
 625                 if (test_bit(key, state->key_down))
 626                         state->reset_seq_cnt++;
 627         }
 628
 629         /* Disable reset until old keys are not released */
 630         state->reset_canceled = state->reset_seq_cnt != 0;
 631
 632         state->reset_seq_version = sysrq_reset_seq_version;
 633 }
 634
 635 static void sysrq_do_reset(unsigned long _state)
 636 {
 637         struct sysrq_state *state = (struct sysrq_state *) _state;
 638
 639         state->reset_requested = true;
 640
 641         sys_sync();
 642         kernel_restart(NULL);
 643 }
 644
 645 static void sysrq_handle_reset_request(struct sysrq_state *state)
 646 {
 647         if (state->reset_requested)
 648                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 649
 650         if (sysrq_reset_downtime_ms)
 651                 mod_timer(&state->keyreset_timer,
 652                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 653         else
 654                 sysrq_do_reset((unsigned long)state);
 655 }
 656
 657 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 658                                         unsigned int code, int value)
 659 {
 660         if (!test_bit(code, state->reset_keybit)) {
 661                 /*
 662                  * Pressing any key _not_ in reset sequence cancels
 663                  * the reset sequence.  Also cancelling the timer in
 664                  * case additional keys were pressed after a reset
 665                  * has been requested.
 666                  */
 667                 if (value && state->reset_seq_cnt) {
 668                         state->reset_canceled = true;
 669                         del_timer(&state->keyreset_timer);
 670                 }
 671         } else if (value == 0) {
 672                 /*
 673                  * Key release - all keys in the reset sequence need
 674                  * to be pressed and held for the reset timeout
 675                  * to hold.
 676                  */
 677                 del_timer(&state->keyreset_timer);
 678
 679                 if (--state->reset_seq_cnt == 0)
 680                         state->reset_canceled = false;
 681         } else if (value == 1) {
 682                 /* key press, not autorepeat */
 683                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 684                     !state->reset_canceled) {
 685                         sysrq_handle_reset_request(state);
 686                 }
 687         }
 688 }
 689
 690 #ifdef CONFIG_OF
 691 static void sysrq_of_get_keyreset_config(void)
 692 {
 693         u32 key;
 694         struct device_node *np;
 695         struct property *prop;
 696         const __be32 *p;
 697
 698         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 699         if (!np) {
 700                 pr_debug("No sysrq node found");
 701                 return;
 702         }
 703
 704         /* Reset in case a __weak definition was present */
 705         sysrq_reset_seq_len = 0;
 706
 707         of_property_for_each_u32(np, "keyset", prop, p, key) {
 708                 if (key == KEY_RESERVED || key > KEY_MAX ||
 709                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 710                         break;
 711
 712                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 713         }
 714
 715         /* Get reset timeout if any. */
 716         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 717 }
 718 #else
 719 static void sysrq_of_get_keyreset_config(void)
 720 {
 721 }
 722 #endif
 723
 724 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 725 {
 726         struct sysrq_state *sysrq =
 727                         container_of(work, struct sysrq_state, reinject_work);
 728         struct input_handle *handle = &sysrq->handle;
 729         unsigned int alt_code = sysrq->alt_use;
 730
 731         if (sysrq->need_reinject) {
 732                 /* we do not want the assignment to be reordered */
 733                 sysrq->reinjecting = true;
 734                 mb();
 735
 736                 /* Simulate press and release of Alt + SysRq */
 737                 input_inject_event(handle, EV_KEY, alt_code, 1);
 738                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 739                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 740
 741                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 742                 input_inject_event(handle, EV_KEY, alt_code, 0);
 743                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 744
 745                 mb();
 746                 sysrq->reinjecting = false;
 747         }
 748 }
 749
 750 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 751                                   unsigned int code, int value)
 752 {
 753         bool was_active = sysrq->active;
 754         bool suppress;
 755
 756         switch (code) {
 757
 758         case KEY_LEFTALT:
 759         case KEY_RIGHTALT:
 760                 if (!value) {
 761                         /* One of ALTs is being released */
 762                         if (sysrq->active && code == sysrq->alt_use)
 763                                 sysrq->active = false;
 764
 765                         sysrq->alt = KEY_RESERVED;
 766
 767                 } else if (value != 2) {
 768                         sysrq->alt = code;
 769                         sysrq->need_reinject = false;
 770                 }
 771                 break;
 772
 773         case KEY_SYSRQ:
 774                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 775                         sysrq->active = true;
 776                         sysrq->alt_use = sysrq->alt;
 777                         /*
 778                          * If nothing else will be pressed we'll need
 779                          * to re-inject Alt-SysRq keysroke.
 780                          */
 781                         sysrq->need_reinject = true;
 782                 }
 783
 784                 /*
 785                  * Pretend that sysrq was never pressed at all. This
 786                  * is needed to properly handle KGDB which will try
 787                  * to release all keys after exiting debugger. If we
 788                  * do not clear key bit it KGDB will end up sending
 789                  * release events for Alt and SysRq, potentially
 790                  * triggering print screen function.
 791                  */
 792                 if (sysrq->active)
 793                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 794
 795                 break;
 796
 797         default:
 798                 if (sysrq->active && value && value != 2) {
 799                         sysrq->need_reinject = false;
 800                         __handle_sysrq(sysrq_xlate[code], true);
 801                 }
 802                 break;
 803         }
 804
 805         suppress = sysrq->active;
 806
 807         if (!sysrq->active) {
 808
 809                 /*
 810                  * See if reset sequence has changed since the last time.
 811                  */
 812                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 813                         sysrq_parse_reset_sequence(sysrq);
 814
 815                 /*
 816                  * If we are not suppressing key presses keep track of
 817                  * keyboard state so we can release keys that have been
 818                  * pressed before entering SysRq mode.
 819                  */
 820                 if (value)
 821                         set_bit(code, sysrq->key_down);
 822                 else
 823                         clear_bit(code, sysrq->key_down);
 824
 825                 if (was_active)
 826                         schedule_work(&sysrq->reinject_work);
 827
 828                 /* Check for reset sequence */
 829                 sysrq_detect_reset_sequence(sysrq, code, value);
 830
 831         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 832                 /*
 833                  * Pass on release events for keys that was pressed before
 834                  * entering SysRq mode.
 835                  */
 836                 suppress = false;
 837         }
 838
 839         return suppress;
 840 }
 841
 842 static bool sysrq_filter(struct input_handle *handle,
 843                          unsigned int type, unsigned int code, int value)
 844 {
 845         struct sysrq_state *sysrq = handle->private;
 846         bool suppress;
 847
 848         /*
 849          * Do not filter anything if we are in the process of re-injecting
 850          * Alt+SysRq combination.
 851          */
 852         if (sysrq->reinjecting)
 853                 return false;
 854
 855         switch (type) {
 856
 857         case EV_SYN:
 858                 suppress = false;
 859                 break;
 860
 861         case EV_KEY:
 862                 suppress = sysrq_handle_keypress(sysrq, code, value);
 863                 break;
 864
 865         default:
 866                 suppress = sysrq->active;
 867                 break;
 868         }
 869
 870         return suppress;
 871 }
 872
 873 static int sysrq_connect(struct input_handler *handler,
 874                          struct input_dev *dev,
 875                          const struct input_device_id *id)
 876 {
 877         struct sysrq_state *sysrq;
 878         int error;
 879
 880         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 881         if (!sysrq)
 882                 return -ENOMEM;
 883
 884         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 885
 886         sysrq->handle.dev = dev;
 887         sysrq->handle.handler = handler;
 888         sysrq->handle.name = "sysrq";
 889         sysrq->handle.private = sysrq;
 890         setup_timer(&sysrq->keyreset_timer,
 891                     sysrq_do_reset, (unsigned long)sysrq);
 892
 893         error = input_register_handle(&sysrq->handle);
 894         if (error) {
 895                 pr_err("Failed to register input sysrq handler, error %d\n",
 896                         error);
 897                 goto err_free;
 898         }
 899
 900         error = input_open_device(&sysrq->handle);
 901         if (error) {
 902                 pr_err("Failed to open input device, error %d\n", error);
 903                 goto err_unregister;
 904         }
 905
 906         return 0;
 907
 908  err_unregister:
 909         input_unregister_handle(&sysrq->handle);
 910  err_free:
 911         kfree(sysrq);
 912         return error;
 913 }
 914
 915 static void sysrq_disconnect(struct input_handle *handle)
 916 {
 917         struct sysrq_state *sysrq = handle->private;
 918
 919         input_close_device(handle);
 920         cancel_work_sync(&sysrq->reinject_work);
 921         del_timer_sync(&sysrq->keyreset_timer);
 922         input_unregister_handle(handle);
 923         kfree(sysrq);
 924 }
 925
 926 /*
 927  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 928  * keyboards have SysRq key predefined and so user may add it to keymap
 929  * later, but we expect all such keyboards to have left alt.
 930  */
 931 static const struct input_device_id sysrq_ids[] = {
 932         {
 933                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 934                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 935                 .evbit = { BIT_MASK(EV_KEY) },
 936                 .keybit = { BIT_MASK(KEY_LEFTALT) },
 937         },
 938         { },
 939 };
 940
 941 static struct input_handler sysrq_handler = {
 942         .filter         = sysrq_filter,
 943         .connect        = sysrq_connect,
 944         .disconnect     = sysrq_disconnect,
 945         .name           = "sysrq",
 946         .id_table       = sysrq_ids,
 947 };
 948
 949 static bool sysrq_handler_registered;
 950
 951 static inline void sysrq_register_handler(void)
 952 {
 953         unsigned short key;
 954         int error;
 955         int i;
 956
 957         /* First check if a __weak interface was instantiated. */
 958         for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
 959                 key = platform_sysrq_reset_seq[i];
 960                 if (key == KEY_RESERVED || key > KEY_MAX)
 961                         break;
 962
 963                 sysrq_reset_seq[sysrq_reset_seq_len++] = key;
 964         }
 965
 966         /*
 967          * DT configuration takes precedence over anything that would
 968          * have been defined via the __weak interface.
 969          */
 970         sysrq_of_get_keyreset_config();
 971
 972         error = input_register_handler(&sysrq_handler);
 973         if (error)
 974                 pr_err("Failed to register input handler, error %d", error);
 975         else
 976                 sysrq_handler_registered = true;
 977 }
 978
 979 static inline void sysrq_unregister_handler(void)
 980 {
 981         if (sysrq_handler_registered) {
 982                 input_unregister_handler(&sysrq_handler);
 983                 sysrq_handler_registered = false;
 984         }
 985 }
 986
 987 static int sysrq_reset_seq_param_set(const char *buffer,
 988                                      const struct kernel_param *kp)
 989 {
 990         unsigned long val;
 991         int error;
 992
 993         error = kstrtoul(buffer, 0, &val);
 994         if (error < 0)
 995                 return error;
 996
 997         if (val > KEY_MAX)
 998                 return -EINVAL;
 999
1000         *((unsigned short *)kp->arg) = val;
1001         sysrq_reset_seq_version++;
1002
1003         return 0;
1004 }
1005
1006 static struct kernel_param_ops param_ops_sysrq_reset_seq = {
1007         .get    = param_get_ushort,
1008         .set    = sysrq_reset_seq_param_set,
1009 };
1010
1011 #define param_check_sysrq_reset_seq(name, p)    \
1012         __param_check(name, p, unsigned short)
1013
1014 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1015                          &sysrq_reset_seq_len, 0644);
1016
1017 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1018
1019 #else
1020
1021 static inline void sysrq_register_handler(void)
1022 {
1023 }
1024
1025 static inline void sysrq_unregister_handler(void)
1026 {
1027 }
1028
1029 #endif /* CONFIG_INPUT */
1030
1031 int sysrq_toggle_support(int enable_mask)
1032 {
1033         bool was_enabled = sysrq_on();
1034
1035         sysrq_enabled = enable_mask;
1036
1037         if (was_enabled != sysrq_on()) {
1038                 if (sysrq_on())
1039                         sysrq_register_handler();
1040                 else
1041                         sysrq_unregister_handler();
1042         }
1043
1044         return 0;
1045 }
1046
1047 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1048                                 struct sysrq_key_op *remove_op_p)
1049 {
1050         int retval;
1051
1052         spin_lock(&sysrq_key_table_lock);
1053         if (__sysrq_get_key_op(key) == remove_op_p) {
1054                 __sysrq_put_key_op(key, insert_op_p);
1055                 retval = 0;
1056         } else {
1057                 retval = -1;
1058         }
1059         spin_unlock(&sysrq_key_table_lock);
1060
1061         /*
1062          * A concurrent __handle_sysrq either got the old op or the new op.
1063          * Wait for it to go away before returning, so the code for an old
1064          * op is not freed (eg. on module unload) while it is in use.
1065          */
1066         synchronize_rcu();
1067
1068         return retval;
1069 }
1070
1071 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1072 {
1073         return __sysrq_swap_key_ops(key, op_p, NULL);
1074 }
1075 EXPORT_SYMBOL(register_sysrq_key);
1076
1077 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1078 {
1079         return __sysrq_swap_key_ops(key, NULL, op_p);
1080 }
1081 EXPORT_SYMBOL(unregister_sysrq_key);
1082
1083 #ifdef CONFIG_PROC_FS
1084 /*
1085  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1086  */
1087 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1088                                    size_t count, loff_t *ppos)
1089 {
1090         if (count) {
1091                 char c;
1092
1093                 if (get_user(c, buf))
1094                         return -EFAULT;
1095                 __handle_sysrq(c, false);
1096         }
1097
1098         return count;
1099 }
1100
1101 static const struct file_operations proc_sysrq_trigger_operations = {
1102         .write          = write_sysrq_trigger,
1103         .llseek         = noop_llseek,
1104 };
1105
1106 static void sysrq_init_procfs(void)
1107 {
1108         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1109                          &proc_sysrq_trigger_operations))
1110                 pr_err("Failed to register proc interface\n");
1111 }
1112
1113 #else
1114
1115 static inline void sysrq_init_procfs(void)
1116 {
1117 }
1118
1119 #endif /* CONFIG_PROC_FS */
1120
1121 static int __init sysrq_init(void)
1122 {
1123         sysrq_init_procfs();
1124
1125         if (sysrq_on())
1126                 sysrq_register_handler();
1127
1128         return 0;
1129 }
1130 module_init(sysrq_init);