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/ctype.h>
  23 #include <linux/interrupt.h>
  24 #include <linux/mm.h>
  25 #include <linux/fs.h>
  26 #include <linux/mount.h>
  27 #include <linux/kdev_t.h>
  28 #include <linux/major.h>
  29 #include <linux/reboot.h>
  30 #include <linux/sysrq.h>
  31 #include <linux/kbd_kern.h>
  32 #include <linux/proc_fs.h>
  33 #include <linux/nmi.h>
  34 #include <linux/quotaops.h>
  35 #include <linux/perf_event.h>
  36 #include <linux/kernel.h>
  37 #include <linux/module.h>
  38 #include <linux/suspend.h>
  39 #include <linux/writeback.h>
  40 #include <linux/swap.h>
  41 #include <linux/spinlock.h>
  42 #include <linux/vt_kern.h>
  43 #include <linux/workqueue.h>
  44 #include <linux/hrtimer.h>
  45 #include <linux/oom.h>
  46 #include <linux/slab.h>
  47 #include <linux/input.h>
  48 #include <linux/uaccess.h>
  49 #include <linux/moduleparam.h>
  50 #include <linux/jiffies.h>
  51 #include <linux/syscalls.h>
  52 #include <linux/of.h>
  53 #include <linux/rcupdate.h>
  54
  55 #include <asm/ptrace.h>
  56 #include <asm/irq_regs.h>
  57
  58 /* Whether we react on sysrq keys or just ignore them */
  59 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
  60 static bool __read_mostly sysrq_always_enabled;
  61
  62 static bool sysrq_on(void)
  63 {
  64         return sysrq_enabled || sysrq_always_enabled;
  65 }
  66
  67 /**
  68  * sysrq_mask - Getter for sysrq_enabled mask.
  69  *
  70  * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
  71  */
  72 int sysrq_mask(void)
  73 {
  74         if (sysrq_always_enabled)
  75                 return 1;
  76         return sysrq_enabled;
  77 }
  78 EXPORT_SYMBOL_GPL(sysrq_mask);
  79
  80 /*
  81  * A value of 1 means 'all', other nonzero values are an op mask:
  82  */
  83 static bool sysrq_on_mask(int mask)
  84 {
  85         return sysrq_always_enabled ||
  86                sysrq_enabled == 1 ||
  87                (sysrq_enabled & mask);
  88 }
  89
  90 static int __init sysrq_always_enabled_setup(char *str)
  91 {
  92         sysrq_always_enabled = true;
  93         pr_info("sysrq always enabled.\n");
  94
  95         return 1;
  96 }
  97
  98 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  99
 100
 101 static void sysrq_handle_loglevel(u8 key)
 102 {
 103         u8 loglevel = key - '0';
 104
 105         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 106         pr_info("Loglevel set to %u\n", loglevel);
 107         console_loglevel = loglevel;
 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(u8 key)
 118 {
 119         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 120
 121         schedule_work(SAK_work);
 122 }
 123 static const struct sysrq_key_op sysrq_SAK_op = {
 124         .handler        = sysrq_handle_SAK,
 125         .help_msg       = "sak(k)",
 126         .action_msg     = "SAK",
 127         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 128 };
 129 #else
 130 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
 131 #endif
 132
 133 #ifdef CONFIG_VT
 134 static void sysrq_handle_unraw(u8 key)
 135 {
 136         vt_reset_unicode(fg_console);
 137 }
 138
 139 static const struct sysrq_key_op sysrq_unraw_op = {
 140         .handler        = sysrq_handle_unraw,
 141         .help_msg       = "unraw(r)",
 142         .action_msg     = "Keyboard mode set to system default",
 143         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 144 };
 145 #else
 146 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
 147 #endif /* CONFIG_VT */
 148
 149 static void sysrq_handle_crash(u8 key)
 150 {
 151         /* release the RCU read lock before crashing */
 152         rcu_read_unlock();
 153
 154         panic("sysrq triggered crash\n");
 155 }
 156 static const struct sysrq_key_op sysrq_crash_op = {
 157         .handler        = sysrq_handle_crash,
 158         .help_msg       = "crash(c)",
 159         .action_msg     = "Trigger a crash",
 160         .enable_mask    = SYSRQ_ENABLE_DUMP,
 161 };
 162
 163 static void sysrq_handle_reboot(u8 key)
 164 {
 165         lockdep_off();
 166         local_irq_enable();
 167         emergency_restart();
 168 }
 169 static const struct sysrq_key_op sysrq_reboot_op = {
 170         .handler        = sysrq_handle_reboot,
 171         .help_msg       = "reboot(b)",
 172         .action_msg     = "Resetting",
 173         .enable_mask    = SYSRQ_ENABLE_BOOT,
 174 };
 175
 176 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
 177
 178 static void sysrq_handle_sync(u8 key)
 179 {
 180         emergency_sync();
 181 }
 182 static const struct sysrq_key_op sysrq_sync_op = {
 183         .handler        = sysrq_handle_sync,
 184         .help_msg       = "sync(s)",
 185         .action_msg     = "Emergency Sync",
 186         .enable_mask    = SYSRQ_ENABLE_SYNC,
 187 };
 188
 189 static void sysrq_handle_show_timers(u8 key)
 190 {
 191         sysrq_timer_list_show();
 192 }
 193
 194 static const struct sysrq_key_op sysrq_show_timers_op = {
 195         .handler        = sysrq_handle_show_timers,
 196         .help_msg       = "show-all-timers(q)",
 197         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 198 };
 199
 200 static void sysrq_handle_mountro(u8 key)
 201 {
 202         emergency_remount();
 203 }
 204 static const struct sysrq_key_op sysrq_mountro_op = {
 205         .handler        = sysrq_handle_mountro,
 206         .help_msg       = "unmount(u)",
 207         .action_msg     = "Emergency Remount R/O",
 208         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 209 };
 210
 211 #ifdef CONFIG_LOCKDEP
 212 static void sysrq_handle_showlocks(u8 key)
 213 {
 214         debug_show_all_locks();
 215 }
 216
 217 static const struct sysrq_key_op sysrq_showlocks_op = {
 218         .handler        = sysrq_handle_showlocks,
 219         .help_msg       = "show-all-locks(d)",
 220         .action_msg     = "Show Locks Held",
 221 };
 222 #else
 223 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
 224 #endif
 225
 226 #ifdef CONFIG_SMP
 227 static DEFINE_RAW_SPINLOCK(show_lock);
 228
 229 static void showacpu(void *dummy)
 230 {
 231         unsigned long flags;
 232
 233         /* Idle CPUs have no interesting backtrace. */
 234         if (idle_cpu(smp_processor_id())) {
 235                 pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
 236                 return;
 237         }
 238
 239         raw_spin_lock_irqsave(&show_lock, flags);
 240         pr_info("CPU%d:\n", smp_processor_id());
 241         show_stack(NULL, NULL, KERN_INFO);
 242         raw_spin_unlock_irqrestore(&show_lock, flags);
 243 }
 244
 245 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 246 {
 247         smp_call_function(showacpu, NULL, 0);
 248 }
 249
 250 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 251
 252 static void sysrq_handle_showallcpus(u8 key)
 253 {
 254         /*
 255          * Fall back to the workqueue based printing if the
 256          * backtrace printing did not succeed or the
 257          * architecture has no support for it:
 258          */
 259         if (!trigger_all_cpu_backtrace()) {
 260                 struct pt_regs *regs = NULL;
 261
 262                 if (in_hardirq())
 263                         regs = get_irq_regs();
 264
 265                 pr_info("CPU%d:\n", smp_processor_id());
 266                 if (regs)
 267                         show_regs(regs);
 268                 else
 269                         show_stack(NULL, NULL, KERN_INFO);
 270
 271                 schedule_work(&sysrq_showallcpus);
 272         }
 273 }
 274
 275 static const struct sysrq_key_op sysrq_showallcpus_op = {
 276         .handler        = sysrq_handle_showallcpus,
 277         .help_msg       = "show-backtrace-all-active-cpus(l)",
 278         .action_msg     = "Show backtrace of all active CPUs",
 279         .enable_mask    = SYSRQ_ENABLE_DUMP,
 280 };
 281 #else
 282 #define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL)
 283 #endif
 284
 285 static void sysrq_handle_showregs(u8 key)
 286 {
 287         struct pt_regs *regs = NULL;
 288
 289         if (in_hardirq())
 290                 regs = get_irq_regs();
 291         if (regs)
 292                 show_regs(regs);
 293         perf_event_print_debug();
 294 }
 295 static const struct sysrq_key_op sysrq_showregs_op = {
 296         .handler        = sysrq_handle_showregs,
 297         .help_msg       = "show-registers(p)",
 298         .action_msg     = "Show Regs",
 299         .enable_mask    = SYSRQ_ENABLE_DUMP,
 300 };
 301
 302 static void sysrq_handle_showstate(u8 key)
 303 {
 304         show_state();
 305         show_all_workqueues();
 306 }
 307 static const struct sysrq_key_op sysrq_showstate_op = {
 308         .handler        = sysrq_handle_showstate,
 309         .help_msg       = "show-task-states(t)",
 310         .action_msg     = "Show State",
 311         .enable_mask    = SYSRQ_ENABLE_DUMP,
 312 };
 313
 314 static void sysrq_handle_showstate_blocked(u8 key)
 315 {
 316         show_state_filter(TASK_UNINTERRUPTIBLE);
 317 }
 318 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
 319         .handler        = sysrq_handle_showstate_blocked,
 320         .help_msg       = "show-blocked-tasks(w)",
 321         .action_msg     = "Show Blocked State",
 322         .enable_mask    = SYSRQ_ENABLE_DUMP,
 323 };
 324
 325 #ifdef CONFIG_TRACING
 326 #include <linux/ftrace.h>
 327
 328 static void sysrq_ftrace_dump(u8 key)
 329 {
 330         ftrace_dump(DUMP_ALL);
 331 }
 332 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
 333         .handler        = sysrq_ftrace_dump,
 334         .help_msg       = "dump-ftrace-buffer(z)",
 335         .action_msg     = "Dump ftrace buffer",
 336         .enable_mask    = SYSRQ_ENABLE_DUMP,
 337 };
 338 #else
 339 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
 340 #endif
 341
 342 static void sysrq_handle_showmem(u8 key)
 343 {
 344         show_mem();
 345 }
 346 static const struct sysrq_key_op sysrq_showmem_op = {
 347         .handler        = sysrq_handle_showmem,
 348         .help_msg       = "show-memory-usage(m)",
 349         .action_msg     = "Show Memory",
 350         .enable_mask    = SYSRQ_ENABLE_DUMP,
 351 };
 352
 353 /*
 354  * Signal sysrq helper function.  Sends a signal to all user processes.
 355  */
 356 static void send_sig_all(int sig)
 357 {
 358         struct task_struct *p;
 359
 360         read_lock(&tasklist_lock);
 361         for_each_process(p) {
 362                 if (p->flags & PF_KTHREAD)
 363                         continue;
 364                 if (is_global_init(p))
 365                         continue;
 366
 367                 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
 368         }
 369         read_unlock(&tasklist_lock);
 370 }
 371
 372 static void sysrq_handle_term(u8 key)
 373 {
 374         send_sig_all(SIGTERM);
 375         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 376 }
 377 static const struct sysrq_key_op sysrq_term_op = {
 378         .handler        = sysrq_handle_term,
 379         .help_msg       = "terminate-all-tasks(e)",
 380         .action_msg     = "Terminate All Tasks",
 381         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 382 };
 383
 384 static void moom_callback(struct work_struct *ignored)
 385 {
 386         const gfp_t gfp_mask = GFP_KERNEL;
 387         struct oom_control oc = {
 388                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 389                 .nodemask = NULL,
 390                 .memcg = NULL,
 391                 .gfp_mask = gfp_mask,
 392                 .order = -1,
 393         };
 394
 395         mutex_lock(&oom_lock);
 396         if (!out_of_memory(&oc))
 397                 pr_info("OOM request ignored. No task eligible\n");
 398         mutex_unlock(&oom_lock);
 399 }
 400
 401 static DECLARE_WORK(moom_work, moom_callback);
 402
 403 static void sysrq_handle_moom(u8 key)
 404 {
 405         schedule_work(&moom_work);
 406 }
 407 static const struct sysrq_key_op sysrq_moom_op = {
 408         .handler        = sysrq_handle_moom,
 409         .help_msg       = "memory-full-oom-kill(f)",
 410         .action_msg     = "Manual OOM execution",
 411         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 412 };
 413
 414 #ifdef CONFIG_BLOCK
 415 static void sysrq_handle_thaw(u8 key)
 416 {
 417         emergency_thaw_all();
 418 }
 419 static const struct sysrq_key_op sysrq_thaw_op = {
 420         .handler        = sysrq_handle_thaw,
 421         .help_msg       = "thaw-filesystems(j)",
 422         .action_msg     = "Emergency Thaw of all frozen filesystems",
 423         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 424 };
 425 #else
 426 #define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL)
 427 #endif
 428
 429 static void sysrq_handle_kill(u8 key)
 430 {
 431         send_sig_all(SIGKILL);
 432         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 433 }
 434 static const struct sysrq_key_op sysrq_kill_op = {
 435         .handler        = sysrq_handle_kill,
 436         .help_msg       = "kill-all-tasks(i)",
 437         .action_msg     = "Kill All Tasks",
 438         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 439 };
 440
 441 static void sysrq_handle_unrt(u8 key)
 442 {
 443         normalize_rt_tasks();
 444 }
 445 static const struct sysrq_key_op sysrq_unrt_op = {
 446         .handler        = sysrq_handle_unrt,
 447         .help_msg       = "nice-all-RT-tasks(n)",
 448         .action_msg     = "Nice All RT Tasks",
 449         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 450 };
 451
 452 /* Key Operations table and lock */
 453 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 454
 455 static const struct sysrq_key_op *sysrq_key_table[62] = {
 456         &sysrq_loglevel_op,             /* 0 */
 457         &sysrq_loglevel_op,             /* 1 */
 458         &sysrq_loglevel_op,             /* 2 */
 459         &sysrq_loglevel_op,             /* 3 */
 460         &sysrq_loglevel_op,             /* 4 */
 461         &sysrq_loglevel_op,             /* 5 */
 462         &sysrq_loglevel_op,             /* 6 */
 463         &sysrq_loglevel_op,             /* 7 */
 464         &sysrq_loglevel_op,             /* 8 */
 465         &sysrq_loglevel_op,             /* 9 */
 466
 467         /*
 468          * a: Don't use for system provided sysrqs, it is handled specially on
 469          * sparc and will never arrive.
 470          */
 471         NULL,                           /* a */
 472         &sysrq_reboot_op,               /* b */
 473         &sysrq_crash_op,                /* c */
 474         &sysrq_showlocks_op,            /* d */
 475         &sysrq_term_op,                 /* e */
 476         &sysrq_moom_op,                 /* f */
 477         /* g: May be registered for the kernel debugger */
 478         NULL,                           /* g */
 479         NULL,                           /* h - reserved for help */
 480         &sysrq_kill_op,                 /* i */
 481         &sysrq_thaw_op,                 /* j */
 482         &sysrq_SAK_op,                  /* k */
 483         &sysrq_showallcpus_op,          /* l */
 484         &sysrq_showmem_op,              /* m */
 485         &sysrq_unrt_op,                 /* n */
 486         /* o: This will often be registered as 'Off' at init time */
 487         NULL,                           /* o */
 488         &sysrq_showregs_op,             /* p */
 489         &sysrq_show_timers_op,          /* q */
 490         &sysrq_unraw_op,                /* r */
 491         &sysrq_sync_op,                 /* s */
 492         &sysrq_showstate_op,            /* t */
 493         &sysrq_mountro_op,              /* u */
 494         /* v: May be registered for frame buffer console restore */
 495         NULL,                           /* v */
 496         &sysrq_showstate_blocked_op,    /* w */
 497         /* x: May be registered on mips for TLB dump */
 498         /* x: May be registered on ppc/powerpc for xmon */
 499         /* x: May be registered on sparc64 for global PMU dump */
 500         NULL,                           /* x */
 501         /* y: May be registered on sparc64 for global register dump */
 502         NULL,                           /* y */
 503         &sysrq_ftrace_dump_op,          /* z */
 504         NULL,                           /* A */
 505         NULL,                           /* B */
 506         NULL,                           /* C */
 507         NULL,                           /* D */
 508         NULL,                           /* E */
 509         NULL,                           /* F */
 510         NULL,                           /* G */
 511         NULL,                           /* H */
 512         NULL,                           /* I */
 513         NULL,                           /* J */
 514         NULL,                           /* K */
 515         NULL,                           /* L */
 516         NULL,                           /* M */
 517         NULL,                           /* N */
 518         NULL,                           /* O */
 519         NULL,                           /* P */
 520         NULL,                           /* Q */
 521         NULL,                           /* R */
 522         NULL,                           /* S */
 523         NULL,                           /* T */
 524         NULL,                           /* U */
 525         NULL,                           /* V */
 526         NULL,                           /* W */
 527         NULL,                           /* X */
 528         NULL,                           /* Y */
 529         NULL,                           /* Z */
 530 };
 531
 532 /* key2index calculation, -1 on invalid index */
 533 static int sysrq_key_table_key2index(u8 key)
 534 {
 535         switch (key) {
 536         case '0' ... '9':
 537                 return key - '0';
 538         case 'a' ... 'z':
 539                 return key - 'a' + 10;
 540         case 'A' ... 'Z':
 541                 return key - 'A' + 10 + 26;
 542         default:
 543                 return -1;
 544         }
 545 }
 546
 547 /*
 548  * get and put functions for the table, exposed to modules.
 549  */
 550 static const struct sysrq_key_op *__sysrq_get_key_op(u8 key)
 551 {
 552         const struct sysrq_key_op *op_p = NULL;
 553         int i;
 554
 555         i = sysrq_key_table_key2index(key);
 556         if (i != -1)
 557                 op_p = sysrq_key_table[i];
 558
 559         return op_p;
 560 }
 561
 562 static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p)
 563 {
 564         int i = sysrq_key_table_key2index(key);
 565
 566         if (i != -1)
 567                 sysrq_key_table[i] = op_p;
 568 }
 569
 570 void __handle_sysrq(u8 key, bool check_mask)
 571 {
 572         const struct sysrq_key_op *op_p;
 573         int orig_log_level;
 574         int orig_suppress_printk;
 575         int i;
 576
 577         orig_suppress_printk = suppress_printk;
 578         suppress_printk = 0;
 579
 580         rcu_sysrq_start();
 581         rcu_read_lock();
 582         /*
 583          * Raise the apparent loglevel to maximum so that the sysrq header
 584          * is shown to provide the user with positive feedback.  We do not
 585          * simply emit this at KERN_EMERG as that would change message
 586          * routing in the consumers of /proc/kmsg.
 587          */
 588         orig_log_level = console_loglevel;
 589         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 590
 591         op_p = __sysrq_get_key_op(key);
 592         if (op_p) {
 593                 /*
 594                  * Should we check for enabled operations (/proc/sysrq-trigger
 595                  * should not) and is the invoked operation enabled?
 596                  */
 597                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 598                         pr_info("%s\n", op_p->action_msg);
 599                         console_loglevel = orig_log_level;
 600                         op_p->handler(key);
 601                 } else {
 602                         pr_info("This sysrq operation is disabled.\n");
 603                         console_loglevel = orig_log_level;
 604                 }
 605         } else {
 606                 pr_info("HELP : ");
 607                 /* Only print the help msg once per handler */
 608                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 609                         if (sysrq_key_table[i]) {
 610                                 int j;
 611
 612                                 for (j = 0; sysrq_key_table[i] !=
 613                                                 sysrq_key_table[j]; j++)
 614                                         ;
 615                                 if (j != i)
 616                                         continue;
 617                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 618                         }
 619                 }
 620                 pr_cont("\n");
 621                 console_loglevel = orig_log_level;
 622         }
 623         rcu_read_unlock();
 624         rcu_sysrq_end();
 625
 626         suppress_printk = orig_suppress_printk;
 627 }
 628
 629 void handle_sysrq(u8 key)
 630 {
 631         if (sysrq_on())
 632                 __handle_sysrq(key, true);
 633 }
 634 EXPORT_SYMBOL(handle_sysrq);
 635
 636 #ifdef CONFIG_INPUT
 637 static int sysrq_reset_downtime_ms;
 638
 639 /* Simple translation table for the SysRq keys */
 640 static const unsigned char sysrq_xlate[KEY_CNT] =
 641         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 642         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 643         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 644         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 645         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 646         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 647         "\r\000/";                                      /* 0x60 - 0x6f */
 648
 649 struct sysrq_state {
 650         struct input_handle handle;
 651         struct work_struct reinject_work;
 652         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 653         unsigned int alt;
 654         unsigned int alt_use;
 655         unsigned int shift;
 656         unsigned int shift_use;
 657         bool active;
 658         bool need_reinject;
 659         bool reinjecting;
 660
 661         /* reset sequence handling */
 662         bool reset_canceled;
 663         bool reset_requested;
 664         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 665         int reset_seq_len;
 666         int reset_seq_cnt;
 667         int reset_seq_version;
 668         struct timer_list keyreset_timer;
 669 };
 670
 671 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 672 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 673 static unsigned int sysrq_reset_seq_len;
 674 static unsigned int sysrq_reset_seq_version = 1;
 675
 676 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 677 {
 678         int i;
 679         unsigned short key;
 680
 681         state->reset_seq_cnt = 0;
 682
 683         for (i = 0; i < sysrq_reset_seq_len; i++) {
 684                 key = sysrq_reset_seq[i];
 685
 686                 if (key == KEY_RESERVED || key > KEY_MAX)
 687                         break;
 688
 689                 __set_bit(key, state->reset_keybit);
 690                 state->reset_seq_len++;
 691
 692                 if (test_bit(key, state->key_down))
 693                         state->reset_seq_cnt++;
 694         }
 695
 696         /* Disable reset until old keys are not released */
 697         state->reset_canceled = state->reset_seq_cnt != 0;
 698
 699         state->reset_seq_version = sysrq_reset_seq_version;
 700 }
 701
 702 static void sysrq_do_reset(struct timer_list *t)
 703 {
 704         struct sysrq_state *state = from_timer(state, t, keyreset_timer);
 705
 706         state->reset_requested = true;
 707
 708         orderly_reboot();
 709 }
 710
 711 static void sysrq_handle_reset_request(struct sysrq_state *state)
 712 {
 713         if (state->reset_requested)
 714                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 715
 716         if (sysrq_reset_downtime_ms)
 717                 mod_timer(&state->keyreset_timer,
 718                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 719         else
 720                 sysrq_do_reset(&state->keyreset_timer);
 721 }
 722
 723 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 724                                         unsigned int code, int value)
 725 {
 726         if (!test_bit(code, state->reset_keybit)) {
 727                 /*
 728                  * Pressing any key _not_ in reset sequence cancels
 729                  * the reset sequence.  Also cancelling the timer in
 730                  * case additional keys were pressed after a reset
 731                  * has been requested.
 732                  */
 733                 if (value && state->reset_seq_cnt) {
 734                         state->reset_canceled = true;
 735                         del_timer(&state->keyreset_timer);
 736                 }
 737         } else if (value == 0) {
 738                 /*
 739                  * Key release - all keys in the reset sequence need
 740                  * to be pressed and held for the reset timeout
 741                  * to hold.
 742                  */
 743                 del_timer(&state->keyreset_timer);
 744
 745                 if (--state->reset_seq_cnt == 0)
 746                         state->reset_canceled = false;
 747         } else if (value == 1) {
 748                 /* key press, not autorepeat */
 749                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 750                     !state->reset_canceled) {
 751                         sysrq_handle_reset_request(state);
 752                 }
 753         }
 754 }
 755
 756 #ifdef CONFIG_OF
 757 static void sysrq_of_get_keyreset_config(void)
 758 {
 759         u32 key;
 760         struct device_node *np;
 761         struct property *prop;
 762         const __be32 *p;
 763
 764         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 765         if (!np) {
 766                 pr_debug("No sysrq node found");
 767                 return;
 768         }
 769
 770         /* Reset in case a __weak definition was present */
 771         sysrq_reset_seq_len = 0;
 772
 773         of_property_for_each_u32(np, "keyset", prop, p, key) {
 774                 if (key == KEY_RESERVED || key > KEY_MAX ||
 775                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 776                         break;
 777
 778                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 779         }
 780
 781         /* Get reset timeout if any. */
 782         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 783
 784         of_node_put(np);
 785 }
 786 #else
 787 static void sysrq_of_get_keyreset_config(void)
 788 {
 789 }
 790 #endif
 791
 792 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 793 {
 794         struct sysrq_state *sysrq =
 795                         container_of(work, struct sysrq_state, reinject_work);
 796         struct input_handle *handle = &sysrq->handle;
 797         unsigned int alt_code = sysrq->alt_use;
 798
 799         if (sysrq->need_reinject) {
 800                 /* we do not want the assignment to be reordered */
 801                 sysrq->reinjecting = true;
 802                 mb();
 803
 804                 /* Simulate press and release of Alt + SysRq */
 805                 input_inject_event(handle, EV_KEY, alt_code, 1);
 806                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 807                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 808
 809                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 810                 input_inject_event(handle, EV_KEY, alt_code, 0);
 811                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 812
 813                 mb();
 814                 sysrq->reinjecting = false;
 815         }
 816 }
 817
 818 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 819                                   unsigned int code, int value)
 820 {
 821         bool was_active = sysrq->active;
 822         bool suppress;
 823
 824         switch (code) {
 825
 826         case KEY_LEFTALT:
 827         case KEY_RIGHTALT:
 828                 if (!value) {
 829                         /* One of ALTs is being released */
 830                         if (sysrq->active && code == sysrq->alt_use)
 831                                 sysrq->active = false;
 832
 833                         sysrq->alt = KEY_RESERVED;
 834
 835                 } else if (value != 2) {
 836                         sysrq->alt = code;
 837                         sysrq->need_reinject = false;
 838                 }
 839                 break;
 840
 841         case KEY_LEFTSHIFT:
 842         case KEY_RIGHTSHIFT:
 843                 if (!value)
 844                         sysrq->shift = KEY_RESERVED;
 845                 else if (value != 2)
 846                         sysrq->shift = code;
 847                 if (sysrq->active)
 848                         sysrq->shift_use = sysrq->shift;
 849                 break;
 850
 851         case KEY_SYSRQ:
 852                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 853                         sysrq->active = true;
 854                         sysrq->alt_use = sysrq->alt;
 855                         /* either RESERVED (for released) or actual code */
 856                         sysrq->shift_use = sysrq->shift;
 857                         /*
 858                          * If nothing else will be pressed we'll need
 859                          * to re-inject Alt-SysRq keysroke.
 860                          */
 861                         sysrq->need_reinject = true;
 862                 }
 863
 864                 /*
 865                  * Pretend that sysrq was never pressed at all. This
 866                  * is needed to properly handle KGDB which will try
 867                  * to release all keys after exiting debugger. If we
 868                  * do not clear key bit it KGDB will end up sending
 869                  * release events for Alt and SysRq, potentially
 870                  * triggering print screen function.
 871                  */
 872                 if (sysrq->active)
 873                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 874
 875                 break;
 876
 877         default:
 878                 if (sysrq->active && value && value != 2) {
 879                         unsigned char c = sysrq_xlate[code];
 880
 881                         sysrq->need_reinject = false;
 882                         if (sysrq->shift_use != KEY_RESERVED)
 883                                 c = toupper(c);
 884                         __handle_sysrq(c, true);
 885                 }
 886                 break;
 887         }
 888
 889         suppress = sysrq->active;
 890
 891         if (!sysrq->active) {
 892
 893                 /*
 894                  * See if reset sequence has changed since the last time.
 895                  */
 896                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 897                         sysrq_parse_reset_sequence(sysrq);
 898
 899                 /*
 900                  * If we are not suppressing key presses keep track of
 901                  * keyboard state so we can release keys that have been
 902                  * pressed before entering SysRq mode.
 903                  */
 904                 if (value)
 905                         set_bit(code, sysrq->key_down);
 906                 else
 907                         clear_bit(code, sysrq->key_down);
 908
 909                 if (was_active)
 910                         schedule_work(&sysrq->reinject_work);
 911
 912                 /* Check for reset sequence */
 913                 sysrq_detect_reset_sequence(sysrq, code, value);
 914
 915         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 916                 /*
 917                  * Pass on release events for keys that was pressed before
 918                  * entering SysRq mode.
 919                  */
 920                 suppress = false;
 921         }
 922
 923         return suppress;
 924 }
 925
 926 static bool sysrq_filter(struct input_handle *handle,
 927                          unsigned int type, unsigned int code, int value)
 928 {
 929         struct sysrq_state *sysrq = handle->private;
 930         bool suppress;
 931
 932         /*
 933          * Do not filter anything if we are in the process of re-injecting
 934          * Alt+SysRq combination.
 935          */
 936         if (sysrq->reinjecting)
 937                 return false;
 938
 939         switch (type) {
 940
 941         case EV_SYN:
 942                 suppress = false;
 943                 break;
 944
 945         case EV_KEY:
 946                 suppress = sysrq_handle_keypress(sysrq, code, value);
 947                 break;
 948
 949         default:
 950                 suppress = sysrq->active;
 951                 break;
 952         }
 953
 954         return suppress;
 955 }
 956
 957 static int sysrq_connect(struct input_handler *handler,
 958                          struct input_dev *dev,
 959                          const struct input_device_id *id)
 960 {
 961         struct sysrq_state *sysrq;
 962         int error;
 963
 964         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 965         if (!sysrq)
 966                 return -ENOMEM;
 967
 968         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 969
 970         sysrq->handle.dev = dev;
 971         sysrq->handle.handler = handler;
 972         sysrq->handle.name = "sysrq";
 973         sysrq->handle.private = sysrq;
 974         timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 975
 976         error = input_register_handle(&sysrq->handle);
 977         if (error) {
 978                 pr_err("Failed to register input sysrq handler, error %d\n",
 979                         error);
 980                 goto err_free;
 981         }
 982
 983         error = input_open_device(&sysrq->handle);
 984         if (error) {
 985                 pr_err("Failed to open input device, error %d\n", error);
 986                 goto err_unregister;
 987         }
 988
 989         return 0;
 990
 991  err_unregister:
 992         input_unregister_handle(&sysrq->handle);
 993  err_free:
 994         kfree(sysrq);
 995         return error;
 996 }
 997
 998 static void sysrq_disconnect(struct input_handle *handle)
 999 {
1000         struct sysrq_state *sysrq = handle->private;
1001
1002         input_close_device(handle);
1003         cancel_work_sync(&sysrq->reinject_work);
1004         timer_shutdown_sync(&sysrq->keyreset_timer);
1005         input_unregister_handle(handle);
1006         kfree(sysrq);
1007 }
1008
1009 /*
1010  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1011  * keyboards have SysRq key predefined and so user may add it to keymap
1012  * later, but we expect all such keyboards to have left alt.
1013  */
1014 static const struct input_device_id sysrq_ids[] = {
1015         {
1016                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1017                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
1018                 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1019                 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1020         },
1021         { },
1022 };
1023
1024 static struct input_handler sysrq_handler = {
1025         .filter         = sysrq_filter,
1026         .connect        = sysrq_connect,
1027         .disconnect     = sysrq_disconnect,
1028         .name           = "sysrq",
1029         .id_table       = sysrq_ids,
1030 };
1031
1032 static inline void sysrq_register_handler(void)
1033 {
1034         int error;
1035
1036         sysrq_of_get_keyreset_config();
1037
1038         error = input_register_handler(&sysrq_handler);
1039         if (error)
1040                 pr_err("Failed to register input handler, error %d", error);
1041 }
1042
1043 static inline void sysrq_unregister_handler(void)
1044 {
1045         input_unregister_handler(&sysrq_handler);
1046 }
1047
1048 static int sysrq_reset_seq_param_set(const char *buffer,
1049                                      const struct kernel_param *kp)
1050 {
1051         unsigned long val;
1052         int error;
1053
1054         error = kstrtoul(buffer, 0, &val);
1055         if (error < 0)
1056                 return error;
1057
1058         if (val > KEY_MAX)
1059                 return -EINVAL;
1060
1061         *((unsigned short *)kp->arg) = val;
1062         sysrq_reset_seq_version++;
1063
1064         return 0;
1065 }
1066
1067 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1068         .get    = param_get_ushort,
1069         .set    = sysrq_reset_seq_param_set,
1070 };
1071
1072 #define param_check_sysrq_reset_seq(name, p)    \
1073         __param_check(name, p, unsigned short)
1074
1075 /*
1076  * not really modular, but the easiest way to keep compat with existing
1077  * bootargs behaviour is to continue using module_param here.
1078  */
1079 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1080                          &sysrq_reset_seq_len, 0644);
1081
1082 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1083
1084 #else
1085
1086 static inline void sysrq_register_handler(void)
1087 {
1088 }
1089
1090 static inline void sysrq_unregister_handler(void)
1091 {
1092 }
1093
1094 #endif /* CONFIG_INPUT */
1095
1096 int sysrq_toggle_support(int enable_mask)
1097 {
1098         bool was_enabled = sysrq_on();
1099
1100         sysrq_enabled = enable_mask;
1101
1102         if (was_enabled != sysrq_on()) {
1103                 if (sysrq_on())
1104                         sysrq_register_handler();
1105                 else
1106                         sysrq_unregister_handler();
1107         }
1108
1109         return 0;
1110 }
1111 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1112
1113 static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p,
1114                                 const struct sysrq_key_op *remove_op_p)
1115 {
1116         int retval;
1117
1118         spin_lock(&sysrq_key_table_lock);
1119         if (__sysrq_get_key_op(key) == remove_op_p) {
1120                 __sysrq_put_key_op(key, insert_op_p);
1121                 retval = 0;
1122         } else {
1123                 retval = -1;
1124         }
1125         spin_unlock(&sysrq_key_table_lock);
1126
1127         /*
1128          * A concurrent __handle_sysrq either got the old op or the new op.
1129          * Wait for it to go away before returning, so the code for an old
1130          * op is not freed (eg. on module unload) while it is in use.
1131          */
1132         synchronize_rcu();
1133
1134         return retval;
1135 }
1136
1137 int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1138 {
1139         return __sysrq_swap_key_ops(key, op_p, NULL);
1140 }
1141 EXPORT_SYMBOL(register_sysrq_key);
1142
1143 int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1144 {
1145         return __sysrq_swap_key_ops(key, NULL, op_p);
1146 }
1147 EXPORT_SYMBOL(unregister_sysrq_key);
1148
1149 #ifdef CONFIG_PROC_FS
1150 /*
1151  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1152  */
1153 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1154                                    size_t count, loff_t *ppos)
1155 {
1156         if (count) {
1157                 char c;
1158
1159                 if (get_user(c, buf))
1160                         return -EFAULT;
1161                 __handle_sysrq(c, false);
1162         }
1163
1164         return count;
1165 }
1166
1167 static const struct proc_ops sysrq_trigger_proc_ops = {
1168         .proc_write     = write_sysrq_trigger,
1169         .proc_lseek     = noop_llseek,
1170 };
1171
1172 static void sysrq_init_procfs(void)
1173 {
1174         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1175                          &sysrq_trigger_proc_ops))
1176                 pr_err("Failed to register proc interface\n");
1177 }
1178
1179 #else
1180
1181 static inline void sysrq_init_procfs(void)
1182 {
1183 }
1184
1185 #endif /* CONFIG_PROC_FS */
1186
1187 static int __init sysrq_init(void)
1188 {
1189         sysrq_init_procfs();
1190
1191         if (sysrq_on())
1192                 sysrq_register_handler();
1193
1194         return 0;
1195 }
1196 device_initcall(sysrq_init);