drivers/tty/sysrq.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      Linux Magic System Request Key Hacks
   4  *
   5  *      (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   6  *      based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
   7  *
   8  *      (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
   9  *      overhauled to use key registration
  10  *      based upon discusions in irc://irc.openprojects.net/#kernelnewbies
  11  *
  12  *      Copyright (c) 2010 Dmitry Torokhov
  13  *      Input handler conversion
  14  */
  15
  16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18 #include <linux/sched/signal.h>
  19 #include <linux/sched/rt.h>
  20 #include <linux/sched/debug.h>
  21 #include <linux/sched/task.h>
  22 #include <linux/interrupt.h>
  23 #include <linux/mm.h>
  24 #include <linux/fs.h>
  25 #include <linux/mount.h>
  26 #include <linux/kdev_t.h>
  27 #include <linux/major.h>
  28 #include <linux/reboot.h>
  29 #include <linux/sysrq.h>
  30 #include <linux/kbd_kern.h>
  31 #include <linux/proc_fs.h>
  32 #include <linux/nmi.h>
  33 #include <linux/quotaops.h>
  34 #include <linux/perf_event.h>
  35 #include <linux/kernel.h>
  36 #include <linux/module.h>
  37 #include <linux/suspend.h>
  38 #include <linux/writeback.h>
  39 #include <linux/swap.h>
  40 #include <linux/spinlock.h>
  41 #include <linux/vt_kern.h>
  42 #include <linux/workqueue.h>
  43 #include <linux/hrtimer.h>
  44 #include <linux/oom.h>
  45 #include <linux/slab.h>
  46 #include <linux/input.h>
  47 #include <linux/uaccess.h>
  48 #include <linux/moduleparam.h>
  49 #include <linux/jiffies.h>
  50 #include <linux/syscalls.h>
  51 #include <linux/of.h>
  52 #include <linux/rcupdate.h>
  53
  54 #include <asm/ptrace.h>
  55 #include <asm/irq_regs.h>
  56
  57 /* Whether we react on sysrq keys or just ignore them */
  58 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
  59 static bool __read_mostly sysrq_always_enabled;
  60
  61 static bool sysrq_on(void)
  62 {
  63         return sysrq_enabled || sysrq_always_enabled;
  64 }
  65
  66 /**
  67  * sysrq_mask - Getter for sysrq_enabled mask.
  68  *
  69  * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
  70  */
  71 int sysrq_mask(void)
  72 {
  73         if (sysrq_always_enabled)
  74                 return 1;
  75         return sysrq_enabled;
  76 }
  77 EXPORT_SYMBOL_GPL(sysrq_mask);
  78
  79 /*
  80  * A value of 1 means 'all', other nonzero values are an op mask:
  81  */
  82 static bool sysrq_on_mask(int mask)
  83 {
  84         return sysrq_always_enabled ||
  85                sysrq_enabled == 1 ||
  86                (sysrq_enabled & mask);
  87 }
  88
  89 static int __init sysrq_always_enabled_setup(char *str)
  90 {
  91         sysrq_always_enabled = true;
  92         pr_info("sysrq always enabled.\n");
  93
  94         return 1;
  95 }
  96
  97 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  98
  99
 100 static void sysrq_handle_loglevel(int key)
 101 {
 102         int i;
 103
 104         i = key - '0';
 105         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 106         pr_info("Loglevel set to %d\n", i);
 107         console_loglevel = i;
 108 }
 109 static const struct sysrq_key_op sysrq_loglevel_op = {
 110         .handler        = sysrq_handle_loglevel,
 111         .help_msg       = "loglevel(0-9)",
 112         .action_msg     = "Changing Loglevel",
 113         .enable_mask    = SYSRQ_ENABLE_LOG,
 114 };
 115
 116 #ifdef CONFIG_VT
 117 static void sysrq_handle_SAK(int key)
 118 {
 119         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 120         schedule_work(SAK_work);
 121 }
 122 static const struct sysrq_key_op sysrq_SAK_op = {
 123         .handler        = sysrq_handle_SAK,
 124         .help_msg       = "sak(k)",
 125         .action_msg     = "SAK",
 126         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 127 };
 128 #else
 129 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
 130 #endif
 131
 132 #ifdef CONFIG_VT
 133 static void sysrq_handle_unraw(int key)
 134 {
 135         vt_reset_unicode(fg_console);
 136 }
 137
 138 static const struct sysrq_key_op sysrq_unraw_op = {
 139         .handler        = sysrq_handle_unraw,
 140         .help_msg       = "unraw(r)",
 141         .action_msg     = "Keyboard mode set to system default",
 142         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 143 };
 144 #else
 145 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
 146 #endif /* CONFIG_VT */
 147
 148 static void sysrq_handle_crash(int key)
 149 {
 150         /* release the RCU read lock before crashing */
 151         rcu_read_unlock();
 152
 153         panic("sysrq triggered crash\n");
 154 }
 155 static const struct sysrq_key_op sysrq_crash_op = {
 156         .handler        = sysrq_handle_crash,
 157         .help_msg       = "crash(c)",
 158         .action_msg     = "Trigger a crash",
 159         .enable_mask    = SYSRQ_ENABLE_DUMP,
 160 };
 161
 162 static void sysrq_handle_reboot(int key)
 163 {
 164         lockdep_off();
 165         local_irq_enable();
 166         emergency_restart();
 167 }
 168 static const struct sysrq_key_op sysrq_reboot_op = {
 169         .handler        = sysrq_handle_reboot,
 170         .help_msg       = "reboot(b)",
 171         .action_msg     = "Resetting",
 172         .enable_mask    = SYSRQ_ENABLE_BOOT,
 173 };
 174
 175 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
 176
 177 static void sysrq_handle_sync(int key)
 178 {
 179         emergency_sync();
 180 }
 181 static const struct sysrq_key_op sysrq_sync_op = {
 182         .handler        = sysrq_handle_sync,
 183         .help_msg       = "sync(s)",
 184         .action_msg     = "Emergency Sync",
 185         .enable_mask    = SYSRQ_ENABLE_SYNC,
 186 };
 187
 188 static void sysrq_handle_show_timers(int key)
 189 {
 190         sysrq_timer_list_show();
 191 }
 192
 193 static const struct sysrq_key_op sysrq_show_timers_op = {
 194         .handler        = sysrq_handle_show_timers,
 195         .help_msg       = "show-all-timers(q)",
 196         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 197 };
 198
 199 static void sysrq_handle_mountro(int key)
 200 {
 201         emergency_remount();
 202 }
 203 static const struct sysrq_key_op sysrq_mountro_op = {
 204         .handler        = sysrq_handle_mountro,
 205         .help_msg       = "unmount(u)",
 206         .action_msg     = "Emergency Remount R/O",
 207         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 208 };
 209
 210 #ifdef CONFIG_LOCKDEP
 211 static void sysrq_handle_showlocks(int key)
 212 {
 213         debug_show_all_locks();
 214 }
 215
 216 static const struct sysrq_key_op sysrq_showlocks_op = {
 217         .handler        = sysrq_handle_showlocks,
 218         .help_msg       = "show-all-locks(d)",
 219         .action_msg     = "Show Locks Held",
 220 };
 221 #else
 222 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
 223 #endif
 224
 225 #ifdef CONFIG_SMP
 226 static DEFINE_RAW_SPINLOCK(show_lock);
 227
 228 static void showacpu(void *dummy)
 229 {
 230         unsigned long flags;
 231
 232         /* Idle CPUs have no interesting backtrace. */
 233         if (idle_cpu(smp_processor_id()))
 234                 return;
 235
 236         raw_spin_lock_irqsave(&show_lock, flags);
 237         pr_info("CPU%d:\n", smp_processor_id());
 238         show_stack(NULL, NULL, KERN_INFO);
 239         raw_spin_unlock_irqrestore(&show_lock, flags);
 240 }
 241
 242 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 243 {
 244         smp_call_function(showacpu, NULL, 0);
 245 }
 246
 247 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 248
 249 static void sysrq_handle_showallcpus(int key)
 250 {
 251         /*
 252          * Fall back to the workqueue based printing if the
 253          * backtrace printing did not succeed or the
 254          * architecture has no support for it:
 255          */
 256         if (!trigger_all_cpu_backtrace()) {
 257                 struct pt_regs *regs = NULL;
 258
 259                 if (in_irq())
 260                         regs = get_irq_regs();
 261                 if (regs) {
 262                         pr_info("CPU%d:\n", smp_processor_id());
 263                         show_regs(regs);
 264                 }
 265                 schedule_work(&sysrq_showallcpus);
 266         }
 267 }
 268
 269 static const struct sysrq_key_op sysrq_showallcpus_op = {
 270         .handler        = sysrq_handle_showallcpus,
 271         .help_msg       = "show-backtrace-all-active-cpus(l)",
 272         .action_msg     = "Show backtrace of all active CPUs",
 273         .enable_mask    = SYSRQ_ENABLE_DUMP,
 274 };
 275 #endif
 276
 277 static void sysrq_handle_showregs(int key)
 278 {
 279         struct pt_regs *regs = NULL;
 280
 281         if (in_irq())
 282                 regs = get_irq_regs();
 283         if (regs)
 284                 show_regs(regs);
 285         perf_event_print_debug();
 286 }
 287 static const struct sysrq_key_op sysrq_showregs_op = {
 288         .handler        = sysrq_handle_showregs,
 289         .help_msg       = "show-registers(p)",
 290         .action_msg     = "Show Regs",
 291         .enable_mask    = SYSRQ_ENABLE_DUMP,
 292 };
 293
 294 static void sysrq_handle_showstate(int key)
 295 {
 296         show_state();
 297         show_workqueue_state();
 298 }
 299 static const struct sysrq_key_op sysrq_showstate_op = {
 300         .handler        = sysrq_handle_showstate,
 301         .help_msg       = "show-task-states(t)",
 302         .action_msg     = "Show State",
 303         .enable_mask    = SYSRQ_ENABLE_DUMP,
 304 };
 305
 306 static void sysrq_handle_showstate_blocked(int key)
 307 {
 308         show_state_filter(TASK_UNINTERRUPTIBLE);
 309 }
 310 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
 311         .handler        = sysrq_handle_showstate_blocked,
 312         .help_msg       = "show-blocked-tasks(w)",
 313         .action_msg     = "Show Blocked State",
 314         .enable_mask    = SYSRQ_ENABLE_DUMP,
 315 };
 316
 317 #ifdef CONFIG_TRACING
 318 #include <linux/ftrace.h>
 319
 320 static void sysrq_ftrace_dump(int key)
 321 {
 322         ftrace_dump(DUMP_ALL);
 323 }
 324 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
 325         .handler        = sysrq_ftrace_dump,
 326         .help_msg       = "dump-ftrace-buffer(z)",
 327         .action_msg     = "Dump ftrace buffer",
 328         .enable_mask    = SYSRQ_ENABLE_DUMP,
 329 };
 330 #else
 331 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
 332 #endif
 333
 334 static void sysrq_handle_showmem(int key)
 335 {
 336         show_mem(0, NULL);
 337 }
 338 static const struct sysrq_key_op sysrq_showmem_op = {
 339         .handler        = sysrq_handle_showmem,
 340         .help_msg       = "show-memory-usage(m)",
 341         .action_msg     = "Show Memory",
 342         .enable_mask    = SYSRQ_ENABLE_DUMP,
 343 };
 344
 345 /*
 346  * Signal sysrq helper function.  Sends a signal to all user processes.
 347  */
 348 static void send_sig_all(int sig)
 349 {
 350         struct task_struct *p;
 351
 352         read_lock(&tasklist_lock);
 353         for_each_process(p) {
 354                 if (p->flags & PF_KTHREAD)
 355                         continue;
 356                 if (is_global_init(p))
 357                         continue;
 358
 359                 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
 360         }
 361         read_unlock(&tasklist_lock);
 362 }
 363
 364 static void sysrq_handle_term(int key)
 365 {
 366         send_sig_all(SIGTERM);
 367         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 368 }
 369 static const struct sysrq_key_op sysrq_term_op = {
 370         .handler        = sysrq_handle_term,
 371         .help_msg       = "terminate-all-tasks(e)",
 372         .action_msg     = "Terminate All Tasks",
 373         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 374 };
 375
 376 static void moom_callback(struct work_struct *ignored)
 377 {
 378         const gfp_t gfp_mask = GFP_KERNEL;
 379         struct oom_control oc = {
 380                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 381                 .nodemask = NULL,
 382                 .memcg = NULL,
 383                 .gfp_mask = gfp_mask,
 384                 .order = -1,
 385         };
 386
 387         mutex_lock(&oom_lock);
 388         if (!out_of_memory(&oc))
 389                 pr_info("OOM request ignored. No task eligible\n");
 390         mutex_unlock(&oom_lock);
 391 }
 392
 393 static DECLARE_WORK(moom_work, moom_callback);
 394
 395 static void sysrq_handle_moom(int key)
 396 {
 397         schedule_work(&moom_work);
 398 }
 399 static const struct sysrq_key_op sysrq_moom_op = {
 400         .handler        = sysrq_handle_moom,
 401         .help_msg       = "memory-full-oom-kill(f)",
 402         .action_msg     = "Manual OOM execution",
 403         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 404 };
 405
 406 #ifdef CONFIG_BLOCK
 407 static void sysrq_handle_thaw(int key)
 408 {
 409         emergency_thaw_all();
 410 }
 411 static const struct sysrq_key_op sysrq_thaw_op = {
 412         .handler        = sysrq_handle_thaw,
 413         .help_msg       = "thaw-filesystems(j)",
 414         .action_msg     = "Emergency Thaw of all frozen filesystems",
 415         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 416 };
 417 #endif
 418
 419 static void sysrq_handle_kill(int key)
 420 {
 421         send_sig_all(SIGKILL);
 422         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 423 }
 424 static const struct sysrq_key_op sysrq_kill_op = {
 425         .handler        = sysrq_handle_kill,
 426         .help_msg       = "kill-all-tasks(i)",
 427         .action_msg     = "Kill All Tasks",
 428         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 429 };
 430
 431 static void sysrq_handle_unrt(int key)
 432 {
 433         normalize_rt_tasks();
 434 }
 435 static const struct sysrq_key_op sysrq_unrt_op = {
 436         .handler        = sysrq_handle_unrt,
 437         .help_msg       = "nice-all-RT-tasks(n)",
 438         .action_msg     = "Nice All RT Tasks",
 439         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 440 };
 441
 442 /* Key Operations table and lock */
 443 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 444
 445 static const struct sysrq_key_op *sysrq_key_table[36] = {
 446         &sysrq_loglevel_op,             /* 0 */
 447         &sysrq_loglevel_op,             /* 1 */
 448         &sysrq_loglevel_op,             /* 2 */
 449         &sysrq_loglevel_op,             /* 3 */
 450         &sysrq_loglevel_op,             /* 4 */
 451         &sysrq_loglevel_op,             /* 5 */
 452         &sysrq_loglevel_op,             /* 6 */
 453         &sysrq_loglevel_op,             /* 7 */
 454         &sysrq_loglevel_op,             /* 8 */
 455         &sysrq_loglevel_op,             /* 9 */
 456
 457         /*
 458          * a: Don't use for system provided sysrqs, it is handled specially on
 459          * sparc and will never arrive.
 460          */
 461         NULL,                           /* a */
 462         &sysrq_reboot_op,               /* b */
 463         &sysrq_crash_op,                /* c */
 464         &sysrq_showlocks_op,            /* d */
 465         &sysrq_term_op,                 /* e */
 466         &sysrq_moom_op,                 /* f */
 467         /* g: May be registered for the kernel debugger */
 468         NULL,                           /* g */
 469         NULL,                           /* h - reserved for help */
 470         &sysrq_kill_op,                 /* i */
 471 #ifdef CONFIG_BLOCK
 472         &sysrq_thaw_op,                 /* j */
 473 #else
 474         NULL,                           /* j */
 475 #endif
 476         &sysrq_SAK_op,                  /* k */
 477 #ifdef CONFIG_SMP
 478         &sysrq_showallcpus_op,          /* l */
 479 #else
 480         NULL,                           /* l */
 481 #endif
 482         &sysrq_showmem_op,              /* m */
 483         &sysrq_unrt_op,                 /* n */
 484         /* o: This will often be registered as 'Off' at init time */
 485         NULL,                           /* o */
 486         &sysrq_showregs_op,             /* p */
 487         &sysrq_show_timers_op,          /* q */
 488         &sysrq_unraw_op,                /* r */
 489         &sysrq_sync_op,                 /* s */
 490         &sysrq_showstate_op,            /* t */
 491         &sysrq_mountro_op,              /* u */
 492         /* v: May be registered for frame buffer console restore */
 493         NULL,                           /* v */
 494         &sysrq_showstate_blocked_op,    /* w */
 495         /* x: May be registered on mips for TLB dump */
 496         /* x: May be registered on ppc/powerpc for xmon */
 497         /* x: May be registered on sparc64 for global PMU dump */
 498         NULL,                           /* x */
 499         /* y: May be registered on sparc64 for global register dump */
 500         NULL,                           /* y */
 501         &sysrq_ftrace_dump_op,          /* z */
 502 };
 503
 504 /* key2index calculation, -1 on invalid index */
 505 static int sysrq_key_table_key2index(int key)
 506 {
 507         int retval;
 508
 509         if ((key >= '0') && (key <= '9'))
 510                 retval = key - '0';
 511         else if ((key >= 'a') && (key <= 'z'))
 512                 retval = key + 10 - 'a';
 513         else
 514                 retval = -1;
 515         return retval;
 516 }
 517
 518 /*
 519  * get and put functions for the table, exposed to modules.
 520  */
 521 static const struct sysrq_key_op *__sysrq_get_key_op(int key)
 522 {
 523         const struct sysrq_key_op *op_p = NULL;
 524         int i;
 525
 526         i = sysrq_key_table_key2index(key);
 527         if (i != -1)
 528                 op_p = sysrq_key_table[i];
 529
 530         return op_p;
 531 }
 532
 533 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p)
 534 {
 535         int i = sysrq_key_table_key2index(key);
 536
 537         if (i != -1)
 538                 sysrq_key_table[i] = op_p;
 539 }
 540
 541 void __handle_sysrq(int key, bool check_mask)
 542 {
 543         const struct sysrq_key_op *op_p;
 544         int orig_log_level;
 545         int orig_suppress_printk;
 546         int i;
 547
 548         orig_suppress_printk = suppress_printk;
 549         suppress_printk = 0;
 550
 551         rcu_sysrq_start();
 552         rcu_read_lock();
 553         /*
 554          * Raise the apparent loglevel to maximum so that the sysrq header
 555          * is shown to provide the user with positive feedback.  We do not
 556          * simply emit this at KERN_EMERG as that would change message
 557          * routing in the consumers of /proc/kmsg.
 558          */
 559         orig_log_level = console_loglevel;
 560         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 561
 562         op_p = __sysrq_get_key_op(key);
 563         if (op_p) {
 564                 /*
 565                  * Should we check for enabled operations (/proc/sysrq-trigger
 566                  * should not) and is the invoked operation enabled?
 567                  */
 568                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 569                         pr_info("%s\n", op_p->action_msg);
 570                         console_loglevel = orig_log_level;
 571                         op_p->handler(key);
 572                 } else {
 573                         pr_info("This sysrq operation is disabled.\n");
 574                         console_loglevel = orig_log_level;
 575                 }
 576         } else {
 577                 pr_info("HELP : ");
 578                 /* Only print the help msg once per handler */
 579                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 580                         if (sysrq_key_table[i]) {
 581                                 int j;
 582
 583                                 for (j = 0; sysrq_key_table[i] !=
 584                                                 sysrq_key_table[j]; j++)
 585                                         ;
 586                                 if (j != i)
 587                                         continue;
 588                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 589                         }
 590                 }
 591                 pr_cont("\n");
 592                 console_loglevel = orig_log_level;
 593         }
 594         rcu_read_unlock();
 595         rcu_sysrq_end();
 596
 597         suppress_printk = orig_suppress_printk;
 598 }
 599
 600 void handle_sysrq(int key)
 601 {
 602         if (sysrq_on())
 603                 __handle_sysrq(key, true);
 604 }
 605 EXPORT_SYMBOL(handle_sysrq);
 606
 607 #ifdef CONFIG_INPUT
 608 static int sysrq_reset_downtime_ms;
 609
 610 /* Simple translation table for the SysRq keys */
 611 static const unsigned char sysrq_xlate[KEY_CNT] =
 612         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 613         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 614         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 615         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 616         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 617         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 618         "\r\000/";                                      /* 0x60 - 0x6f */
 619
 620 struct sysrq_state {
 621         struct input_handle handle;
 622         struct work_struct reinject_work;
 623         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 624         unsigned int alt;
 625         unsigned int alt_use;
 626         bool active;
 627         bool need_reinject;
 628         bool reinjecting;
 629
 630         /* reset sequence handling */
 631         bool reset_canceled;
 632         bool reset_requested;
 633         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 634         int reset_seq_len;
 635         int reset_seq_cnt;
 636         int reset_seq_version;
 637         struct timer_list keyreset_timer;
 638 };
 639
 640 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 641 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 642 static unsigned int sysrq_reset_seq_len;
 643 static unsigned int sysrq_reset_seq_version = 1;
 644
 645 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 646 {
 647         int i;
 648         unsigned short key;
 649
 650         state->reset_seq_cnt = 0;
 651
 652         for (i = 0; i < sysrq_reset_seq_len; i++) {
 653                 key = sysrq_reset_seq[i];
 654
 655                 if (key == KEY_RESERVED || key > KEY_MAX)
 656                         break;
 657
 658                 __set_bit(key, state->reset_keybit);
 659                 state->reset_seq_len++;
 660
 661                 if (test_bit(key, state->key_down))
 662                         state->reset_seq_cnt++;
 663         }
 664
 665         /* Disable reset until old keys are not released */
 666         state->reset_canceled = state->reset_seq_cnt != 0;
 667
 668         state->reset_seq_version = sysrq_reset_seq_version;
 669 }
 670
 671 static void sysrq_do_reset(struct timer_list *t)
 672 {
 673         struct sysrq_state *state = from_timer(state, t, keyreset_timer);
 674
 675         state->reset_requested = true;
 676
 677         orderly_reboot();
 678 }
 679
 680 static void sysrq_handle_reset_request(struct sysrq_state *state)
 681 {
 682         if (state->reset_requested)
 683                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 684
 685         if (sysrq_reset_downtime_ms)
 686                 mod_timer(&state->keyreset_timer,
 687                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 688         else
 689                 sysrq_do_reset(&state->keyreset_timer);
 690 }
 691
 692 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 693                                         unsigned int code, int value)
 694 {
 695         if (!test_bit(code, state->reset_keybit)) {
 696                 /*
 697                  * Pressing any key _not_ in reset sequence cancels
 698                  * the reset sequence.  Also cancelling the timer in
 699                  * case additional keys were pressed after a reset
 700                  * has been requested.
 701                  */
 702                 if (value && state->reset_seq_cnt) {
 703                         state->reset_canceled = true;
 704                         del_timer(&state->keyreset_timer);
 705                 }
 706         } else if (value == 0) {
 707                 /*
 708                  * Key release - all keys in the reset sequence need
 709                  * to be pressed and held for the reset timeout
 710                  * to hold.
 711                  */
 712                 del_timer(&state->keyreset_timer);
 713
 714                 if (--state->reset_seq_cnt == 0)
 715                         state->reset_canceled = false;
 716         } else if (value == 1) {
 717                 /* key press, not autorepeat */
 718                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 719                     !state->reset_canceled) {
 720                         sysrq_handle_reset_request(state);
 721                 }
 722         }
 723 }
 724
 725 #ifdef CONFIG_OF
 726 static void sysrq_of_get_keyreset_config(void)
 727 {
 728         u32 key;
 729         struct device_node *np;
 730         struct property *prop;
 731         const __be32 *p;
 732
 733         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 734         if (!np) {
 735                 pr_debug("No sysrq node found");
 736                 return;
 737         }
 738
 739         /* Reset in case a __weak definition was present */
 740         sysrq_reset_seq_len = 0;
 741
 742         of_property_for_each_u32(np, "keyset", prop, p, key) {
 743                 if (key == KEY_RESERVED || key > KEY_MAX ||
 744                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 745                         break;
 746
 747                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 748         }
 749
 750         /* Get reset timeout if any. */
 751         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 752
 753         of_node_put(np);
 754 }
 755 #else
 756 static void sysrq_of_get_keyreset_config(void)
 757 {
 758 }
 759 #endif
 760
 761 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 762 {
 763         struct sysrq_state *sysrq =
 764                         container_of(work, struct sysrq_state, reinject_work);
 765         struct input_handle *handle = &sysrq->handle;
 766         unsigned int alt_code = sysrq->alt_use;
 767
 768         if (sysrq->need_reinject) {
 769                 /* we do not want the assignment to be reordered */
 770                 sysrq->reinjecting = true;
 771                 mb();
 772
 773                 /* Simulate press and release of Alt + SysRq */
 774                 input_inject_event(handle, EV_KEY, alt_code, 1);
 775                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 776                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 777
 778                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 779                 input_inject_event(handle, EV_KEY, alt_code, 0);
 780                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 781
 782                 mb();
 783                 sysrq->reinjecting = false;
 784         }
 785 }
 786
 787 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 788                                   unsigned int code, int value)
 789 {
 790         bool was_active = sysrq->active;
 791         bool suppress;
 792
 793         switch (code) {
 794
 795         case KEY_LEFTALT:
 796         case KEY_RIGHTALT:
 797                 if (!value) {
 798                         /* One of ALTs is being released */
 799                         if (sysrq->active && code == sysrq->alt_use)
 800                                 sysrq->active = false;
 801
 802                         sysrq->alt = KEY_RESERVED;
 803
 804                 } else if (value != 2) {
 805                         sysrq->alt = code;
 806                         sysrq->need_reinject = false;
 807                 }
 808                 break;
 809
 810         case KEY_SYSRQ:
 811                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 812                         sysrq->active = true;
 813                         sysrq->alt_use = sysrq->alt;
 814                         /*
 815                          * If nothing else will be pressed we'll need
 816                          * to re-inject Alt-SysRq keysroke.
 817                          */
 818                         sysrq->need_reinject = true;
 819                 }
 820
 821                 /*
 822                  * Pretend that sysrq was never pressed at all. This
 823                  * is needed to properly handle KGDB which will try
 824                  * to release all keys after exiting debugger. If we
 825                  * do not clear key bit it KGDB will end up sending
 826                  * release events for Alt and SysRq, potentially
 827                  * triggering print screen function.
 828                  */
 829                 if (sysrq->active)
 830                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 831
 832                 break;
 833
 834         default:
 835                 if (sysrq->active && value && value != 2) {
 836                         sysrq->need_reinject = false;
 837                         __handle_sysrq(sysrq_xlate[code], true);
 838                 }
 839                 break;
 840         }
 841
 842         suppress = sysrq->active;
 843
 844         if (!sysrq->active) {
 845
 846                 /*
 847                  * See if reset sequence has changed since the last time.
 848                  */
 849                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 850                         sysrq_parse_reset_sequence(sysrq);
 851
 852                 /*
 853                  * If we are not suppressing key presses keep track of
 854                  * keyboard state so we can release keys that have been
 855                  * pressed before entering SysRq mode.
 856                  */
 857                 if (value)
 858                         set_bit(code, sysrq->key_down);
 859                 else
 860                         clear_bit(code, sysrq->key_down);
 861
 862                 if (was_active)
 863                         schedule_work(&sysrq->reinject_work);
 864
 865                 /* Check for reset sequence */
 866                 sysrq_detect_reset_sequence(sysrq, code, value);
 867
 868         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 869                 /*
 870                  * Pass on release events for keys that was pressed before
 871                  * entering SysRq mode.
 872                  */
 873                 suppress = false;
 874         }
 875
 876         return suppress;
 877 }
 878
 879 static bool sysrq_filter(struct input_handle *handle,
 880                          unsigned int type, unsigned int code, int value)
 881 {
 882         struct sysrq_state *sysrq = handle->private;
 883         bool suppress;
 884
 885         /*
 886          * Do not filter anything if we are in the process of re-injecting
 887          * Alt+SysRq combination.
 888          */
 889         if (sysrq->reinjecting)
 890                 return false;
 891
 892         switch (type) {
 893
 894         case EV_SYN:
 895                 suppress = false;
 896                 break;
 897
 898         case EV_KEY:
 899                 suppress = sysrq_handle_keypress(sysrq, code, value);
 900                 break;
 901
 902         default:
 903                 suppress = sysrq->active;
 904                 break;
 905         }
 906
 907         return suppress;
 908 }
 909
 910 static int sysrq_connect(struct input_handler *handler,
 911                          struct input_dev *dev,
 912                          const struct input_device_id *id)
 913 {
 914         struct sysrq_state *sysrq;
 915         int error;
 916
 917         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 918         if (!sysrq)
 919                 return -ENOMEM;
 920
 921         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 922
 923         sysrq->handle.dev = dev;
 924         sysrq->handle.handler = handler;
 925         sysrq->handle.name = "sysrq";
 926         sysrq->handle.private = sysrq;
 927         timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 928
 929         error = input_register_handle(&sysrq->handle);
 930         if (error) {
 931                 pr_err("Failed to register input sysrq handler, error %d\n",
 932                         error);
 933                 goto err_free;
 934         }
 935
 936         error = input_open_device(&sysrq->handle);
 937         if (error) {
 938                 pr_err("Failed to open input device, error %d\n", error);
 939                 goto err_unregister;
 940         }
 941
 942         return 0;
 943
 944  err_unregister:
 945         input_unregister_handle(&sysrq->handle);
 946  err_free:
 947         kfree(sysrq);
 948         return error;
 949 }
 950
 951 static void sysrq_disconnect(struct input_handle *handle)
 952 {
 953         struct sysrq_state *sysrq = handle->private;
 954
 955         input_close_device(handle);
 956         cancel_work_sync(&sysrq->reinject_work);
 957         del_timer_sync(&sysrq->keyreset_timer);
 958         input_unregister_handle(handle);
 959         kfree(sysrq);
 960 }
 961
 962 /*
 963  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 964  * keyboards have SysRq key predefined and so user may add it to keymap
 965  * later, but we expect all such keyboards to have left alt.
 966  */
 967 static const struct input_device_id sysrq_ids[] = {
 968         {
 969                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 970                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 971                 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
 972                 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
 973         },
 974         { },
 975 };
 976
 977 static struct input_handler sysrq_handler = {
 978         .filter         = sysrq_filter,
 979         .connect        = sysrq_connect,
 980         .disconnect     = sysrq_disconnect,
 981         .name           = "sysrq",
 982         .id_table       = sysrq_ids,
 983 };
 984
 985 static inline void sysrq_register_handler(void)
 986 {
 987         int error;
 988
 989         sysrq_of_get_keyreset_config();
 990
 991         error = input_register_handler(&sysrq_handler);
 992         if (error)
 993                 pr_err("Failed to register input handler, error %d", error);
 994 }
 995
 996 static inline void sysrq_unregister_handler(void)
 997 {
 998         input_unregister_handler(&sysrq_handler);
 999 }
1000
1001 static int sysrq_reset_seq_param_set(const char *buffer,
1002                                      const struct kernel_param *kp)
1003 {
1004         unsigned long val;
1005         int error;
1006
1007         error = kstrtoul(buffer, 0, &val);
1008         if (error < 0)
1009                 return error;
1010
1011         if (val > KEY_MAX)
1012                 return -EINVAL;
1013
1014         *((unsigned short *)kp->arg) = val;
1015         sysrq_reset_seq_version++;
1016
1017         return 0;
1018 }
1019
1020 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1021         .get    = param_get_ushort,
1022         .set    = sysrq_reset_seq_param_set,
1023 };
1024
1025 #define param_check_sysrq_reset_seq(name, p)    \
1026         __param_check(name, p, unsigned short)
1027
1028 /*
1029  * not really modular, but the easiest way to keep compat with existing
1030  * bootargs behaviour is to continue using module_param here.
1031  */
1032 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1033                          &sysrq_reset_seq_len, 0644);
1034
1035 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1036
1037 #else
1038
1039 static inline void sysrq_register_handler(void)
1040 {
1041 }
1042
1043 static inline void sysrq_unregister_handler(void)
1044 {
1045 }
1046
1047 #endif /* CONFIG_INPUT */
1048
1049 int sysrq_toggle_support(int enable_mask)
1050 {
1051         bool was_enabled = sysrq_on();
1052
1053         sysrq_enabled = enable_mask;
1054
1055         if (was_enabled != sysrq_on()) {
1056                 if (sysrq_on())
1057                         sysrq_register_handler();
1058                 else
1059                         sysrq_unregister_handler();
1060         }
1061
1062         return 0;
1063 }
1064 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1065
1066 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p,
1067                                 const struct sysrq_key_op *remove_op_p)
1068 {
1069         int retval;
1070
1071         spin_lock(&sysrq_key_table_lock);
1072         if (__sysrq_get_key_op(key) == remove_op_p) {
1073                 __sysrq_put_key_op(key, insert_op_p);
1074                 retval = 0;
1075         } else {
1076                 retval = -1;
1077         }
1078         spin_unlock(&sysrq_key_table_lock);
1079
1080         /*
1081          * A concurrent __handle_sysrq either got the old op or the new op.
1082          * Wait for it to go away before returning, so the code for an old
1083          * op is not freed (eg. on module unload) while it is in use.
1084          */
1085         synchronize_rcu();
1086
1087         return retval;
1088 }
1089
1090 int register_sysrq_key(int key, const struct sysrq_key_op *op_p)
1091 {
1092         return __sysrq_swap_key_ops(key, op_p, NULL);
1093 }
1094 EXPORT_SYMBOL(register_sysrq_key);
1095
1096 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)
1097 {
1098         return __sysrq_swap_key_ops(key, NULL, op_p);
1099 }
1100 EXPORT_SYMBOL(unregister_sysrq_key);
1101
1102 #ifdef CONFIG_PROC_FS
1103 /*
1104  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1105  */
1106 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1107                                    size_t count, loff_t *ppos)
1108 {
1109         if (count) {
1110                 char c;
1111
1112                 if (get_user(c, buf))
1113                         return -EFAULT;
1114                 __handle_sysrq(c, false);
1115         }
1116
1117         return count;
1118 }
1119
1120 static const struct proc_ops sysrq_trigger_proc_ops = {
1121         .proc_write     = write_sysrq_trigger,
1122         .proc_lseek     = noop_llseek,
1123 };
1124
1125 static void sysrq_init_procfs(void)
1126 {
1127         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1128                          &sysrq_trigger_proc_ops))
1129                 pr_err("Failed to register proc interface\n");
1130 }
1131
1132 #else
1133
1134 static inline void sysrq_init_procfs(void)
1135 {
1136 }
1137
1138 #endif /* CONFIG_PROC_FS */
1139
1140 static int __init sysrq_init(void)
1141 {
1142         sysrq_init_procfs();
1143
1144         if (sysrq_on())
1145                 sysrq_register_handler();
1146
1147         return 0;
1148 }
1149 device_initcall(sysrq_init);