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(int key)
 102 {
 103         int i;
 104
 105         i = key - '0';
 106         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 107         pr_info("Loglevel set to %d\n", i);
 108         console_loglevel = i;
 109 }
 110 static const struct sysrq_key_op sysrq_loglevel_op = {
 111         .handler        = sysrq_handle_loglevel,
 112         .help_msg       = "loglevel(0-9)",
 113         .action_msg     = "Changing Loglevel",
 114         .enable_mask    = SYSRQ_ENABLE_LOG,
 115 };
 116
 117 #ifdef CONFIG_VT
 118 static void sysrq_handle_SAK(int key)
 119 {
 120         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 121
 122         schedule_work(SAK_work);
 123 }
 124 static const struct sysrq_key_op sysrq_SAK_op = {
 125         .handler        = sysrq_handle_SAK,
 126         .help_msg       = "sak(k)",
 127         .action_msg     = "SAK",
 128         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 129 };
 130 #else
 131 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
 132 #endif
 133
 134 #ifdef CONFIG_VT
 135 static void sysrq_handle_unraw(int key)
 136 {
 137         vt_reset_unicode(fg_console);
 138 }
 139
 140 static const struct sysrq_key_op sysrq_unraw_op = {
 141         .handler        = sysrq_handle_unraw,
 142         .help_msg       = "unraw(r)",
 143         .action_msg     = "Keyboard mode set to system default",
 144         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 145 };
 146 #else
 147 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
 148 #endif /* CONFIG_VT */
 149
 150 static void sysrq_handle_crash(int key)
 151 {
 152         /* release the RCU read lock before crashing */
 153         rcu_read_unlock();
 154
 155         panic("sysrq triggered crash\n");
 156 }
 157 static const struct sysrq_key_op sysrq_crash_op = {
 158         .handler        = sysrq_handle_crash,
 159         .help_msg       = "crash(c)",
 160         .action_msg     = "Trigger a crash",
 161         .enable_mask    = SYSRQ_ENABLE_DUMP,
 162 };
 163
 164 static void sysrq_handle_reboot(int key)
 165 {
 166         lockdep_off();
 167         local_irq_enable();
 168         emergency_restart();
 169 }
 170 static const struct sysrq_key_op sysrq_reboot_op = {
 171         .handler        = sysrq_handle_reboot,
 172         .help_msg       = "reboot(b)",
 173         .action_msg     = "Resetting",
 174         .enable_mask    = SYSRQ_ENABLE_BOOT,
 175 };
 176
 177 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
 178
 179 static void sysrq_handle_sync(int key)
 180 {
 181         emergency_sync();
 182 }
 183 static const struct sysrq_key_op sysrq_sync_op = {
 184         .handler        = sysrq_handle_sync,
 185         .help_msg       = "sync(s)",
 186         .action_msg     = "Emergency Sync",
 187         .enable_mask    = SYSRQ_ENABLE_SYNC,
 188 };
 189
 190 static void sysrq_handle_show_timers(int key)
 191 {
 192         sysrq_timer_list_show();
 193 }
 194
 195 static const struct sysrq_key_op sysrq_show_timers_op = {
 196         .handler        = sysrq_handle_show_timers,
 197         .help_msg       = "show-all-timers(q)",
 198         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 199 };
 200
 201 static void sysrq_handle_mountro(int key)
 202 {
 203         emergency_remount();
 204 }
 205 static const struct sysrq_key_op sysrq_mountro_op = {
 206         .handler        = sysrq_handle_mountro,
 207         .help_msg       = "unmount(u)",
 208         .action_msg     = "Emergency Remount R/O",
 209         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 210 };
 211
 212 #ifdef CONFIG_LOCKDEP
 213 static void sysrq_handle_showlocks(int key)
 214 {
 215         debug_show_all_locks();
 216 }
 217
 218 static const struct sysrq_key_op sysrq_showlocks_op = {
 219         .handler        = sysrq_handle_showlocks,
 220         .help_msg       = "show-all-locks(d)",
 221         .action_msg     = "Show Locks Held",
 222 };
 223 #else
 224 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
 225 #endif
 226
 227 #ifdef CONFIG_SMP
 228 static DEFINE_RAW_SPINLOCK(show_lock);
 229
 230 static void showacpu(void *dummy)
 231 {
 232         unsigned long flags;
 233
 234         /* Idle CPUs have no interesting backtrace. */
 235         if (idle_cpu(smp_processor_id()))
 236                 return;
 237
 238         raw_spin_lock_irqsave(&show_lock, flags);
 239         pr_info("CPU%d:\n", smp_processor_id());
 240         show_stack(NULL, NULL, KERN_INFO);
 241         raw_spin_unlock_irqrestore(&show_lock, flags);
 242 }
 243
 244 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 245 {
 246         smp_call_function(showacpu, NULL, 0);
 247 }
 248
 249 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 250
 251 static void sysrq_handle_showallcpus(int key)
 252 {
 253         /*
 254          * Fall back to the workqueue based printing if the
 255          * backtrace printing did not succeed or the
 256          * architecture has no support for it:
 257          */
 258         if (!trigger_all_cpu_backtrace()) {
 259                 struct pt_regs *regs = NULL;
 260
 261                 if (in_hardirq())
 262                         regs = get_irq_regs();
 263                 if (regs) {
 264                         pr_info("CPU%d:\n", smp_processor_id());
 265                         show_regs(regs);
 266                 }
 267                 schedule_work(&sysrq_showallcpus);
 268         }
 269 }
 270
 271 static const struct sysrq_key_op sysrq_showallcpus_op = {
 272         .handler        = sysrq_handle_showallcpus,
 273         .help_msg       = "show-backtrace-all-active-cpus(l)",
 274         .action_msg     = "Show backtrace of all active CPUs",
 275         .enable_mask    = SYSRQ_ENABLE_DUMP,
 276 };
 277 #endif
 278
 279 static void sysrq_handle_showregs(int key)
 280 {
 281         struct pt_regs *regs = NULL;
 282
 283         if (in_hardirq())
 284                 regs = get_irq_regs();
 285         if (regs)
 286                 show_regs(regs);
 287         perf_event_print_debug();
 288 }
 289 static const struct sysrq_key_op sysrq_showregs_op = {
 290         .handler        = sysrq_handle_showregs,
 291         .help_msg       = "show-registers(p)",
 292         .action_msg     = "Show Regs",
 293         .enable_mask    = SYSRQ_ENABLE_DUMP,
 294 };
 295
 296 static void sysrq_handle_showstate(int key)
 297 {
 298         show_state();
 299         show_all_workqueues();
 300 }
 301 static const struct sysrq_key_op sysrq_showstate_op = {
 302         .handler        = sysrq_handle_showstate,
 303         .help_msg       = "show-task-states(t)",
 304         .action_msg     = "Show State",
 305         .enable_mask    = SYSRQ_ENABLE_DUMP,
 306 };
 307
 308 static void sysrq_handle_showstate_blocked(int key)
 309 {
 310         show_state_filter(TASK_UNINTERRUPTIBLE);
 311 }
 312 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
 313         .handler        = sysrq_handle_showstate_blocked,
 314         .help_msg       = "show-blocked-tasks(w)",
 315         .action_msg     = "Show Blocked State",
 316         .enable_mask    = SYSRQ_ENABLE_DUMP,
 317 };
 318
 319 #ifdef CONFIG_TRACING
 320 #include <linux/ftrace.h>
 321
 322 static void sysrq_ftrace_dump(int key)
 323 {
 324         ftrace_dump(DUMP_ALL);
 325 }
 326 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
 327         .handler        = sysrq_ftrace_dump,
 328         .help_msg       = "dump-ftrace-buffer(z)",
 329         .action_msg     = "Dump ftrace buffer",
 330         .enable_mask    = SYSRQ_ENABLE_DUMP,
 331 };
 332 #else
 333 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
 334 #endif
 335
 336 static void sysrq_handle_showmem(int key)
 337 {
 338         show_mem(0, NULL);
 339 }
 340 static const struct sysrq_key_op sysrq_showmem_op = {
 341         .handler        = sysrq_handle_showmem,
 342         .help_msg       = "show-memory-usage(m)",
 343         .action_msg     = "Show Memory",
 344         .enable_mask    = SYSRQ_ENABLE_DUMP,
 345 };
 346
 347 /*
 348  * Signal sysrq helper function.  Sends a signal to all user processes.
 349  */
 350 static void send_sig_all(int sig)
 351 {
 352         struct task_struct *p;
 353
 354         read_lock(&tasklist_lock);
 355         for_each_process(p) {
 356                 if (p->flags & PF_KTHREAD)
 357                         continue;
 358                 if (is_global_init(p))
 359                         continue;
 360
 361                 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
 362         }
 363         read_unlock(&tasklist_lock);
 364 }
 365
 366 static void sysrq_handle_term(int key)
 367 {
 368         send_sig_all(SIGTERM);
 369         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 370 }
 371 static const struct sysrq_key_op sysrq_term_op = {
 372         .handler        = sysrq_handle_term,
 373         .help_msg       = "terminate-all-tasks(e)",
 374         .action_msg     = "Terminate All Tasks",
 375         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 376 };
 377
 378 static void moom_callback(struct work_struct *ignored)
 379 {
 380         const gfp_t gfp_mask = GFP_KERNEL;
 381         struct oom_control oc = {
 382                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 383                 .nodemask = NULL,
 384                 .memcg = NULL,
 385                 .gfp_mask = gfp_mask,
 386                 .order = -1,
 387         };
 388
 389         mutex_lock(&oom_lock);
 390         if (!out_of_memory(&oc))
 391                 pr_info("OOM request ignored. No task eligible\n");
 392         mutex_unlock(&oom_lock);
 393 }
 394
 395 static DECLARE_WORK(moom_work, moom_callback);
 396
 397 static void sysrq_handle_moom(int key)
 398 {
 399         schedule_work(&moom_work);
 400 }
 401 static const struct sysrq_key_op sysrq_moom_op = {
 402         .handler        = sysrq_handle_moom,
 403         .help_msg       = "memory-full-oom-kill(f)",
 404         .action_msg     = "Manual OOM execution",
 405         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 406 };
 407
 408 static void sysrq_handle_thaw(int key)
 409 {
 410         emergency_thaw_all();
 411 }
 412 static const struct sysrq_key_op sysrq_thaw_op = {
 413         .handler        = sysrq_handle_thaw,
 414         .help_msg       = "thaw-filesystems(j)",
 415         .action_msg     = "Emergency Thaw of all frozen filesystems",
 416         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 417 };
 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[62] = {
 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         NULL,                           /* A */
 503         NULL,                           /* B */
 504         NULL,                           /* C */
 505         NULL,                           /* D */
 506         NULL,                           /* E */
 507         NULL,                           /* F */
 508         NULL,                           /* G */
 509         NULL,                           /* H */
 510         NULL,                           /* I */
 511         NULL,                           /* J */
 512         NULL,                           /* K */
 513         NULL,                           /* L */
 514         NULL,                           /* M */
 515         NULL,                           /* N */
 516         NULL,                           /* O */
 517         NULL,                           /* P */
 518         NULL,                           /* Q */
 519         NULL,                           /* R */
 520         NULL,                           /* S */
 521         NULL,                           /* T */
 522         NULL,                           /* U */
 523         NULL,                           /* V */
 524         NULL,                           /* W */
 525         NULL,                           /* X */
 526         NULL,                           /* Y */
 527         NULL,                           /* Z */
 528 };
 529
 530 /* key2index calculation, -1 on invalid index */
 531 static int sysrq_key_table_key2index(int key)
 532 {
 533         int retval;
 534
 535         if ((key >= '0') && (key <= '9'))
 536                 retval = key - '0';
 537         else if ((key >= 'a') && (key <= 'z'))
 538                 retval = key + 10 - 'a';
 539         else if ((key >= 'A') && (key <= 'Z'))
 540                 retval = key + 36 - 'A';
 541         else
 542                 retval = -1;
 543         return retval;
 544 }
 545
 546 /*
 547  * get and put functions for the table, exposed to modules.
 548  */
 549 static const struct sysrq_key_op *__sysrq_get_key_op(int key)
 550 {
 551         const struct sysrq_key_op *op_p = NULL;
 552         int i;
 553
 554         i = sysrq_key_table_key2index(key);
 555         if (i != -1)
 556                 op_p = sysrq_key_table[i];
 557
 558         return op_p;
 559 }
 560
 561 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p)
 562 {
 563         int i = sysrq_key_table_key2index(key);
 564
 565         if (i != -1)
 566                 sysrq_key_table[i] = op_p;
 567 }
 568
 569 void __handle_sysrq(int key, bool check_mask)
 570 {
 571         const struct sysrq_key_op *op_p;
 572         int orig_log_level;
 573         int orig_suppress_printk;
 574         int i;
 575
 576         orig_suppress_printk = suppress_printk;
 577         suppress_printk = 0;
 578
 579         rcu_sysrq_start();
 580         rcu_read_lock();
 581         printk_prefer_direct_enter();
 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         printk_prefer_direct_exit();
 624         rcu_read_unlock();
 625         rcu_sysrq_end();
 626
 627         suppress_printk = orig_suppress_printk;
 628 }
 629
 630 void handle_sysrq(int key)
 631 {
 632         if (sysrq_on())
 633                 __handle_sysrq(key, true);
 634 }
 635 EXPORT_SYMBOL(handle_sysrq);
 636
 637 #ifdef CONFIG_INPUT
 638 static int sysrq_reset_downtime_ms;
 639
 640 /* Simple translation table for the SysRq keys */
 641 static const unsigned char sysrq_xlate[KEY_CNT] =
 642         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 643         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 644         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 645         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 646         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 647         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 648         "\r\000/";                                      /* 0x60 - 0x6f */
 649
 650 struct sysrq_state {
 651         struct input_handle handle;
 652         struct work_struct reinject_work;
 653         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 654         unsigned int alt;
 655         unsigned int alt_use;
 656         unsigned int shift;
 657         unsigned int shift_use;
 658         bool active;
 659         bool need_reinject;
 660         bool reinjecting;
 661
 662         /* reset sequence handling */
 663         bool reset_canceled;
 664         bool reset_requested;
 665         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 666         int reset_seq_len;
 667         int reset_seq_cnt;
 668         int reset_seq_version;
 669         struct timer_list keyreset_timer;
 670 };
 671
 672 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 673 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 674 static unsigned int sysrq_reset_seq_len;
 675 static unsigned int sysrq_reset_seq_version = 1;
 676
 677 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 678 {
 679         int i;
 680         unsigned short key;
 681
 682         state->reset_seq_cnt = 0;
 683
 684         for (i = 0; i < sysrq_reset_seq_len; i++) {
 685                 key = sysrq_reset_seq[i];
 686
 687                 if (key == KEY_RESERVED || key > KEY_MAX)
 688                         break;
 689
 690                 __set_bit(key, state->reset_keybit);
 691                 state->reset_seq_len++;
 692
 693                 if (test_bit(key, state->key_down))
 694                         state->reset_seq_cnt++;
 695         }
 696
 697         /* Disable reset until old keys are not released */
 698         state->reset_canceled = state->reset_seq_cnt != 0;
 699
 700         state->reset_seq_version = sysrq_reset_seq_version;
 701 }
 702
 703 static void sysrq_do_reset(struct timer_list *t)
 704 {
 705         struct sysrq_state *state = from_timer(state, t, keyreset_timer);
 706
 707         state->reset_requested = true;
 708
 709         orderly_reboot();
 710 }
 711
 712 static void sysrq_handle_reset_request(struct sysrq_state *state)
 713 {
 714         if (state->reset_requested)
 715                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 716
 717         if (sysrq_reset_downtime_ms)
 718                 mod_timer(&state->keyreset_timer,
 719                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 720         else
 721                 sysrq_do_reset(&state->keyreset_timer);
 722 }
 723
 724 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 725                                         unsigned int code, int value)
 726 {
 727         if (!test_bit(code, state->reset_keybit)) {
 728                 /*
 729                  * Pressing any key _not_ in reset sequence cancels
 730                  * the reset sequence.  Also cancelling the timer in
 731                  * case additional keys were pressed after a reset
 732                  * has been requested.
 733                  */
 734                 if (value && state->reset_seq_cnt) {
 735                         state->reset_canceled = true;
 736                         del_timer(&state->keyreset_timer);
 737                 }
 738         } else if (value == 0) {
 739                 /*
 740                  * Key release - all keys in the reset sequence need
 741                  * to be pressed and held for the reset timeout
 742                  * to hold.
 743                  */
 744                 del_timer(&state->keyreset_timer);
 745
 746                 if (--state->reset_seq_cnt == 0)
 747                         state->reset_canceled = false;
 748         } else if (value == 1) {
 749                 /* key press, not autorepeat */
 750                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 751                     !state->reset_canceled) {
 752                         sysrq_handle_reset_request(state);
 753                 }
 754         }
 755 }
 756
 757 #ifdef CONFIG_OF
 758 static void sysrq_of_get_keyreset_config(void)
 759 {
 760         u32 key;
 761         struct device_node *np;
 762         struct property *prop;
 763         const __be32 *p;
 764
 765         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 766         if (!np) {
 767                 pr_debug("No sysrq node found");
 768                 return;
 769         }
 770
 771         /* Reset in case a __weak definition was present */
 772         sysrq_reset_seq_len = 0;
 773
 774         of_property_for_each_u32(np, "keyset", prop, p, key) {
 775                 if (key == KEY_RESERVED || key > KEY_MAX ||
 776                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 777                         break;
 778
 779                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 780         }
 781
 782         /* Get reset timeout if any. */
 783         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 784
 785         of_node_put(np);
 786 }
 787 #else
 788 static void sysrq_of_get_keyreset_config(void)
 789 {
 790 }
 791 #endif
 792
 793 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 794 {
 795         struct sysrq_state *sysrq =
 796                         container_of(work, struct sysrq_state, reinject_work);
 797         struct input_handle *handle = &sysrq->handle;
 798         unsigned int alt_code = sysrq->alt_use;
 799
 800         if (sysrq->need_reinject) {
 801                 /* we do not want the assignment to be reordered */
 802                 sysrq->reinjecting = true;
 803                 mb();
 804
 805                 /* Simulate press and release of Alt + SysRq */
 806                 input_inject_event(handle, EV_KEY, alt_code, 1);
 807                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 808                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 809
 810                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 811                 input_inject_event(handle, EV_KEY, alt_code, 0);
 812                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 813
 814                 mb();
 815                 sysrq->reinjecting = false;
 816         }
 817 }
 818
 819 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 820                                   unsigned int code, int value)
 821 {
 822         bool was_active = sysrq->active;
 823         bool suppress;
 824
 825         switch (code) {
 826
 827         case KEY_LEFTALT:
 828         case KEY_RIGHTALT:
 829                 if (!value) {
 830                         /* One of ALTs is being released */
 831                         if (sysrq->active && code == sysrq->alt_use)
 832                                 sysrq->active = false;
 833
 834                         sysrq->alt = KEY_RESERVED;
 835
 836                 } else if (value != 2) {
 837                         sysrq->alt = code;
 838                         sysrq->need_reinject = false;
 839                 }
 840                 break;
 841
 842         case KEY_LEFTSHIFT:
 843         case KEY_RIGHTSHIFT:
 844                 if (!value)
 845                         sysrq->shift = KEY_RESERVED;
 846                 else if (value != 2)
 847                         sysrq->shift = code;
 848                 if (sysrq->active)
 849                         sysrq->shift_use = sysrq->shift;
 850                 break;
 851
 852         case KEY_SYSRQ:
 853                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 854                         sysrq->active = true;
 855                         sysrq->alt_use = sysrq->alt;
 856                         /* either RESERVED (for released) or actual code */
 857                         sysrq->shift_use = sysrq->shift;
 858                         /*
 859                          * If nothing else will be pressed we'll need
 860                          * to re-inject Alt-SysRq keysroke.
 861                          */
 862                         sysrq->need_reinject = true;
 863                 }
 864
 865                 /*
 866                  * Pretend that sysrq was never pressed at all. This
 867                  * is needed to properly handle KGDB which will try
 868                  * to release all keys after exiting debugger. If we
 869                  * do not clear key bit it KGDB will end up sending
 870                  * release events for Alt and SysRq, potentially
 871                  * triggering print screen function.
 872                  */
 873                 if (sysrq->active)
 874                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 875
 876                 break;
 877
 878         default:
 879                 if (sysrq->active && value && value != 2) {
 880                         unsigned char c = sysrq_xlate[code];
 881
 882                         sysrq->need_reinject = false;
 883                         if (sysrq->shift_use != KEY_RESERVED)
 884                                 c = toupper(c);
 885                         __handle_sysrq(c, true);
 886                 }
 887                 break;
 888         }
 889
 890         suppress = sysrq->active;
 891
 892         if (!sysrq->active) {
 893
 894                 /*
 895                  * See if reset sequence has changed since the last time.
 896                  */
 897                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 898                         sysrq_parse_reset_sequence(sysrq);
 899
 900                 /*
 901                  * If we are not suppressing key presses keep track of
 902                  * keyboard state so we can release keys that have been
 903                  * pressed before entering SysRq mode.
 904                  */
 905                 if (value)
 906                         set_bit(code, sysrq->key_down);
 907                 else
 908                         clear_bit(code, sysrq->key_down);
 909
 910                 if (was_active)
 911                         schedule_work(&sysrq->reinject_work);
 912
 913                 /* Check for reset sequence */
 914                 sysrq_detect_reset_sequence(sysrq, code, value);
 915
 916         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 917                 /*
 918                  * Pass on release events for keys that was pressed before
 919                  * entering SysRq mode.
 920                  */
 921                 suppress = false;
 922         }
 923
 924         return suppress;
 925 }
 926
 927 static bool sysrq_filter(struct input_handle *handle,
 928                          unsigned int type, unsigned int code, int value)
 929 {
 930         struct sysrq_state *sysrq = handle->private;
 931         bool suppress;
 932
 933         /*
 934          * Do not filter anything if we are in the process of re-injecting
 935          * Alt+SysRq combination.
 936          */
 937         if (sysrq->reinjecting)
 938                 return false;
 939
 940         switch (type) {
 941
 942         case EV_SYN:
 943                 suppress = false;
 944                 break;
 945
 946         case EV_KEY:
 947                 suppress = sysrq_handle_keypress(sysrq, code, value);
 948                 break;
 949
 950         default:
 951                 suppress = sysrq->active;
 952                 break;
 953         }
 954
 955         return suppress;
 956 }
 957
 958 static int sysrq_connect(struct input_handler *handler,
 959                          struct input_dev *dev,
 960                          const struct input_device_id *id)
 961 {
 962         struct sysrq_state *sysrq;
 963         int error;
 964
 965         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 966         if (!sysrq)
 967                 return -ENOMEM;
 968
 969         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 970
 971         sysrq->handle.dev = dev;
 972         sysrq->handle.handler = handler;
 973         sysrq->handle.name = "sysrq";
 974         sysrq->handle.private = sysrq;
 975         timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 976
 977         error = input_register_handle(&sysrq->handle);
 978         if (error) {
 979                 pr_err("Failed to register input sysrq handler, error %d\n",
 980                         error);
 981                 goto err_free;
 982         }
 983
 984         error = input_open_device(&sysrq->handle);
 985         if (error) {
 986                 pr_err("Failed to open input device, error %d\n", error);
 987                 goto err_unregister;
 988         }
 989
 990         return 0;
 991
 992  err_unregister:
 993         input_unregister_handle(&sysrq->handle);
 994  err_free:
 995         kfree(sysrq);
 996         return error;
 997 }
 998
 999 static void sysrq_disconnect(struct input_handle *handle)
1000 {
1001         struct sysrq_state *sysrq = handle->private;
1002
1003         input_close_device(handle);
1004         cancel_work_sync(&sysrq->reinject_work);
1005         del_timer_sync(&sysrq->keyreset_timer);
1006         input_unregister_handle(handle);
1007         kfree(sysrq);
1008 }
1009
1010 /*
1011  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1012  * keyboards have SysRq key predefined and so user may add it to keymap
1013  * later, but we expect all such keyboards to have left alt.
1014  */
1015 static const struct input_device_id sysrq_ids[] = {
1016         {
1017                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1018                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
1019                 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1020                 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1021         },
1022         { },
1023 };
1024
1025 static struct input_handler sysrq_handler = {
1026         .filter         = sysrq_filter,
1027         .connect        = sysrq_connect,
1028         .disconnect     = sysrq_disconnect,
1029         .name           = "sysrq",
1030         .id_table       = sysrq_ids,
1031 };
1032
1033 static inline void sysrq_register_handler(void)
1034 {
1035         int error;
1036
1037         sysrq_of_get_keyreset_config();
1038
1039         error = input_register_handler(&sysrq_handler);
1040         if (error)
1041                 pr_err("Failed to register input handler, error %d", error);
1042 }
1043
1044 static inline void sysrq_unregister_handler(void)
1045 {
1046         input_unregister_handler(&sysrq_handler);
1047 }
1048
1049 static int sysrq_reset_seq_param_set(const char *buffer,
1050                                      const struct kernel_param *kp)
1051 {
1052         unsigned long val;
1053         int error;
1054
1055         error = kstrtoul(buffer, 0, &val);
1056         if (error < 0)
1057                 return error;
1058
1059         if (val > KEY_MAX)
1060                 return -EINVAL;
1061
1062         *((unsigned short *)kp->arg) = val;
1063         sysrq_reset_seq_version++;
1064
1065         return 0;
1066 }
1067
1068 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1069         .get    = param_get_ushort,
1070         .set    = sysrq_reset_seq_param_set,
1071 };
1072
1073 #define param_check_sysrq_reset_seq(name, p)    \
1074         __param_check(name, p, unsigned short)
1075
1076 /*
1077  * not really modular, but the easiest way to keep compat with existing
1078  * bootargs behaviour is to continue using module_param here.
1079  */
1080 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1081                          &sysrq_reset_seq_len, 0644);
1082
1083 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1084
1085 #else
1086
1087 static inline void sysrq_register_handler(void)
1088 {
1089 }
1090
1091 static inline void sysrq_unregister_handler(void)
1092 {
1093 }
1094
1095 #endif /* CONFIG_INPUT */
1096
1097 int sysrq_toggle_support(int enable_mask)
1098 {
1099         bool was_enabled = sysrq_on();
1100
1101         sysrq_enabled = enable_mask;
1102
1103         if (was_enabled != sysrq_on()) {
1104                 if (sysrq_on())
1105                         sysrq_register_handler();
1106                 else
1107                         sysrq_unregister_handler();
1108         }
1109
1110         return 0;
1111 }
1112 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1113
1114 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p,
1115                                 const struct sysrq_key_op *remove_op_p)
1116 {
1117         int retval;
1118
1119         spin_lock(&sysrq_key_table_lock);
1120         if (__sysrq_get_key_op(key) == remove_op_p) {
1121                 __sysrq_put_key_op(key, insert_op_p);
1122                 retval = 0;
1123         } else {
1124                 retval = -1;
1125         }
1126         spin_unlock(&sysrq_key_table_lock);
1127
1128         /*
1129          * A concurrent __handle_sysrq either got the old op or the new op.
1130          * Wait for it to go away before returning, so the code for an old
1131          * op is not freed (eg. on module unload) while it is in use.
1132          */
1133         synchronize_rcu();
1134
1135         return retval;
1136 }
1137
1138 int register_sysrq_key(int key, const struct sysrq_key_op *op_p)
1139 {
1140         return __sysrq_swap_key_ops(key, op_p, NULL);
1141 }
1142 EXPORT_SYMBOL(register_sysrq_key);
1143
1144 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)
1145 {
1146         return __sysrq_swap_key_ops(key, NULL, op_p);
1147 }
1148 EXPORT_SYMBOL(unregister_sysrq_key);
1149
1150 #ifdef CONFIG_PROC_FS
1151 /*
1152  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1153  */
1154 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1155                                    size_t count, loff_t *ppos)
1156 {
1157         if (count) {
1158                 char c;
1159
1160                 if (get_user(c, buf))
1161                         return -EFAULT;
1162                 __handle_sysrq(c, false);
1163         }
1164
1165         return count;
1166 }
1167
1168 static const struct proc_ops sysrq_trigger_proc_ops = {
1169         .proc_write     = write_sysrq_trigger,
1170         .proc_lseek     = noop_llseek,
1171 };
1172
1173 static void sysrq_init_procfs(void)
1174 {
1175         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1176                          &sysrq_trigger_proc_ops))
1177                 pr_err("Failed to register proc interface\n");
1178 }
1179
1180 #else
1181
1182 static inline void sysrq_init_procfs(void)
1183 {
1184 }
1185
1186 #endif /* CONFIG_PROC_FS */
1187
1188 static int __init sysrq_init(void)
1189 {
1190         sysrq_init_procfs();
1191
1192         if (sysrq_on())
1193                 sysrq_register_handler();
1194
1195         return 0;
1196 }
1197 device_initcall(sysrq_init);