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         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(int 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(int 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(int 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(int 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(int 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(int 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(int 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(int 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_irq())
 263                         regs = get_irq_regs();
 264
 265                 pr_info("CPU%d:\n", get_cpu());
 266                 if (regs)
 267                         show_regs(regs);
 268                 else
 269                         show_stack(NULL, NULL, KERN_INFO);
 270
 271                 schedule_work(&sysrq_showallcpus);
 272                 put_cpu();
 273         }
 274 }
 275
 276 static const struct sysrq_key_op sysrq_showallcpus_op = {
 277         .handler        = sysrq_handle_showallcpus,
 278         .help_msg       = "show-backtrace-all-active-cpus(l)",
 279         .action_msg     = "Show backtrace of all active CPUs",
 280         .enable_mask    = SYSRQ_ENABLE_DUMP,
 281 };
 282 #endif
 283
 284 static void sysrq_handle_showregs(int key)
 285 {
 286         struct pt_regs *regs = NULL;
 287
 288         if (in_irq())
 289                 regs = get_irq_regs();
 290         if (regs)
 291                 show_regs(regs);
 292         perf_event_print_debug();
 293 }
 294 static const struct sysrq_key_op sysrq_showregs_op = {
 295         .handler        = sysrq_handle_showregs,
 296         .help_msg       = "show-registers(p)",
 297         .action_msg     = "Show Regs",
 298         .enable_mask    = SYSRQ_ENABLE_DUMP,
 299 };
 300
 301 static void sysrq_handle_showstate(int key)
 302 {
 303         show_state();
 304         show_workqueue_state();
 305 }
 306 static const struct sysrq_key_op sysrq_showstate_op = {
 307         .handler        = sysrq_handle_showstate,
 308         .help_msg       = "show-task-states(t)",
 309         .action_msg     = "Show State",
 310         .enable_mask    = SYSRQ_ENABLE_DUMP,
 311 };
 312
 313 static void sysrq_handle_showstate_blocked(int key)
 314 {
 315         show_state_filter(TASK_UNINTERRUPTIBLE);
 316 }
 317 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
 318         .handler        = sysrq_handle_showstate_blocked,
 319         .help_msg       = "show-blocked-tasks(w)",
 320         .action_msg     = "Show Blocked State",
 321         .enable_mask    = SYSRQ_ENABLE_DUMP,
 322 };
 323
 324 #ifdef CONFIG_TRACING
 325 #include <linux/ftrace.h>
 326
 327 static void sysrq_ftrace_dump(int key)
 328 {
 329         ftrace_dump(DUMP_ALL);
 330 }
 331 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
 332         .handler        = sysrq_ftrace_dump,
 333         .help_msg       = "dump-ftrace-buffer(z)",
 334         .action_msg     = "Dump ftrace buffer",
 335         .enable_mask    = SYSRQ_ENABLE_DUMP,
 336 };
 337 #else
 338 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
 339 #endif
 340
 341 static void sysrq_handle_showmem(int key)
 342 {
 343         show_mem(0, NULL);
 344 }
 345 static const struct sysrq_key_op sysrq_showmem_op = {
 346         .handler        = sysrq_handle_showmem,
 347         .help_msg       = "show-memory-usage(m)",
 348         .action_msg     = "Show Memory",
 349         .enable_mask    = SYSRQ_ENABLE_DUMP,
 350 };
 351
 352 /*
 353  * Signal sysrq helper function.  Sends a signal to all user processes.
 354  */
 355 static void send_sig_all(int sig)
 356 {
 357         struct task_struct *p;
 358
 359         read_lock(&tasklist_lock);
 360         for_each_process(p) {
 361                 if (p->flags & PF_KTHREAD)
 362                         continue;
 363                 if (is_global_init(p))
 364                         continue;
 365
 366                 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
 367         }
 368         read_unlock(&tasklist_lock);
 369 }
 370
 371 static void sysrq_handle_term(int key)
 372 {
 373         send_sig_all(SIGTERM);
 374         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 375 }
 376 static const struct sysrq_key_op sysrq_term_op = {
 377         .handler        = sysrq_handle_term,
 378         .help_msg       = "terminate-all-tasks(e)",
 379         .action_msg     = "Terminate All Tasks",
 380         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 381 };
 382
 383 static void moom_callback(struct work_struct *ignored)
 384 {
 385         const gfp_t gfp_mask = GFP_KERNEL;
 386         struct oom_control oc = {
 387                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 388                 .nodemask = NULL,
 389                 .memcg = NULL,
 390                 .gfp_mask = gfp_mask,
 391                 .order = -1,
 392         };
 393
 394         mutex_lock(&oom_lock);
 395         if (!out_of_memory(&oc))
 396                 pr_info("OOM request ignored. No task eligible\n");
 397         mutex_unlock(&oom_lock);
 398 }
 399
 400 static DECLARE_WORK(moom_work, moom_callback);
 401
 402 static void sysrq_handle_moom(int key)
 403 {
 404         schedule_work(&moom_work);
 405 }
 406 static const struct sysrq_key_op sysrq_moom_op = {
 407         .handler        = sysrq_handle_moom,
 408         .help_msg       = "memory-full-oom-kill(f)",
 409         .action_msg     = "Manual OOM execution",
 410         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 411 };
 412
 413 static void sysrq_handle_thaw(int key)
 414 {
 415         emergency_thaw_all();
 416 }
 417 static const struct sysrq_key_op sysrq_thaw_op = {
 418         .handler        = sysrq_handle_thaw,
 419         .help_msg       = "thaw-filesystems(j)",
 420         .action_msg     = "Emergency Thaw of all frozen filesystems",
 421         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 422 };
 423
 424 static void sysrq_handle_kill(int key)
 425 {
 426         send_sig_all(SIGKILL);
 427         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 428 }
 429 static const struct sysrq_key_op sysrq_kill_op = {
 430         .handler        = sysrq_handle_kill,
 431         .help_msg       = "kill-all-tasks(i)",
 432         .action_msg     = "Kill All Tasks",
 433         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 434 };
 435
 436 static void sysrq_handle_unrt(int key)
 437 {
 438         normalize_rt_tasks();
 439 }
 440 static const struct sysrq_key_op sysrq_unrt_op = {
 441         .handler        = sysrq_handle_unrt,
 442         .help_msg       = "nice-all-RT-tasks(n)",
 443         .action_msg     = "Nice All RT Tasks",
 444         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 445 };
 446
 447 /* Key Operations table and lock */
 448 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 449
 450 static const struct sysrq_key_op *sysrq_key_table[62] = {
 451         &sysrq_loglevel_op,             /* 0 */
 452         &sysrq_loglevel_op,             /* 1 */
 453         &sysrq_loglevel_op,             /* 2 */
 454         &sysrq_loglevel_op,             /* 3 */
 455         &sysrq_loglevel_op,             /* 4 */
 456         &sysrq_loglevel_op,             /* 5 */
 457         &sysrq_loglevel_op,             /* 6 */
 458         &sysrq_loglevel_op,             /* 7 */
 459         &sysrq_loglevel_op,             /* 8 */
 460         &sysrq_loglevel_op,             /* 9 */
 461
 462         /*
 463          * a: Don't use for system provided sysrqs, it is handled specially on
 464          * sparc and will never arrive.
 465          */
 466         NULL,                           /* a */
 467         &sysrq_reboot_op,               /* b */
 468         &sysrq_crash_op,                /* c */
 469         &sysrq_showlocks_op,            /* d */
 470         &sysrq_term_op,                 /* e */
 471         &sysrq_moom_op,                 /* f */
 472         /* g: May be registered for the kernel debugger */
 473         NULL,                           /* g */
 474         NULL,                           /* h - reserved for help */
 475         &sysrq_kill_op,                 /* i */
 476 #ifdef CONFIG_BLOCK
 477         &sysrq_thaw_op,                 /* j */
 478 #else
 479         NULL,                           /* j */
 480 #endif
 481         &sysrq_SAK_op,                  /* k */
 482 #ifdef CONFIG_SMP
 483         &sysrq_showallcpus_op,          /* l */
 484 #else
 485         NULL,                           /* l */
 486 #endif
 487         &sysrq_showmem_op,              /* m */
 488         &sysrq_unrt_op,                 /* n */
 489         /* o: This will often be registered as 'Off' at init time */
 490         NULL,                           /* o */
 491         &sysrq_showregs_op,             /* p */
 492         &sysrq_show_timers_op,          /* q */
 493         &sysrq_unraw_op,                /* r */
 494         &sysrq_sync_op,                 /* s */
 495         &sysrq_showstate_op,            /* t */
 496         &sysrq_mountro_op,              /* u */
 497         /* v: May be registered for frame buffer console restore */
 498         NULL,                           /* v */
 499         &sysrq_showstate_blocked_op,    /* w */
 500         /* x: May be registered on mips for TLB dump */
 501         /* x: May be registered on ppc/powerpc for xmon */
 502         /* x: May be registered on sparc64 for global PMU dump */
 503         NULL,                           /* x */
 504         /* y: May be registered on sparc64 for global register dump */
 505         NULL,                           /* y */
 506         &sysrq_ftrace_dump_op,          /* z */
 507         NULL,                           /* A */
 508         NULL,                           /* B */
 509         NULL,                           /* C */
 510         NULL,                           /* D */
 511         NULL,                           /* E */
 512         NULL,                           /* F */
 513         NULL,                           /* G */
 514         NULL,                           /* H */
 515         NULL,                           /* I */
 516         NULL,                           /* J */
 517         NULL,                           /* K */
 518         NULL,                           /* L */
 519         NULL,                           /* M */
 520         NULL,                           /* N */
 521         NULL,                           /* O */
 522         NULL,                           /* P */
 523         NULL,                           /* Q */
 524         NULL,                           /* R */
 525         NULL,                           /* S */
 526         NULL,                           /* T */
 527         NULL,                           /* U */
 528         NULL,                           /* V */
 529         NULL,                           /* W */
 530         NULL,                           /* X */
 531         NULL,                           /* Y */
 532         NULL,                           /* Z */
 533 };
 534
 535 /* key2index calculation, -1 on invalid index */
 536 static int sysrq_key_table_key2index(int key)
 537 {
 538         int retval;
 539
 540         if ((key >= '0') && (key <= '9'))
 541                 retval = key - '0';
 542         else if ((key >= 'a') && (key <= 'z'))
 543                 retval = key + 10 - 'a';
 544         else if ((key >= 'A') && (key <= 'Z'))
 545                 retval = key + 36 - 'A';
 546         else
 547                 retval = -1;
 548         return retval;
 549 }
 550
 551 /*
 552  * get and put functions for the table, exposed to modules.
 553  */
 554 static const struct sysrq_key_op *__sysrq_get_key_op(int key)
 555 {
 556         const struct sysrq_key_op *op_p = NULL;
 557         int i;
 558
 559         i = sysrq_key_table_key2index(key);
 560         if (i != -1)
 561                 op_p = sysrq_key_table[i];
 562
 563         return op_p;
 564 }
 565
 566 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p)
 567 {
 568         int i = sysrq_key_table_key2index(key);
 569
 570         if (i != -1)
 571                 sysrq_key_table[i] = op_p;
 572 }
 573
 574 void __handle_sysrq(int key, bool check_mask)
 575 {
 576         const struct sysrq_key_op *op_p;
 577         int orig_log_level;
 578         int orig_suppress_printk;
 579         int i;
 580
 581         orig_suppress_printk = suppress_printk;
 582         suppress_printk = 0;
 583
 584         rcu_sysrq_start();
 585         rcu_read_lock();
 586         /*
 587          * Raise the apparent loglevel to maximum so that the sysrq header
 588          * is shown to provide the user with positive feedback.  We do not
 589          * simply emit this at KERN_EMERG as that would change message
 590          * routing in the consumers of /proc/kmsg.
 591          */
 592         orig_log_level = console_loglevel;
 593         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 594
 595         op_p = __sysrq_get_key_op(key);
 596         if (op_p) {
 597                 /*
 598                  * Should we check for enabled operations (/proc/sysrq-trigger
 599                  * should not) and is the invoked operation enabled?
 600                  */
 601                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 602                         pr_info("%s\n", op_p->action_msg);
 603                         console_loglevel = orig_log_level;
 604                         op_p->handler(key);
 605                 } else {
 606                         pr_info("This sysrq operation is disabled.\n");
 607                         console_loglevel = orig_log_level;
 608                 }
 609         } else {
 610                 pr_info("HELP : ");
 611                 /* Only print the help msg once per handler */
 612                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 613                         if (sysrq_key_table[i]) {
 614                                 int j;
 615
 616                                 for (j = 0; sysrq_key_table[i] !=
 617                                                 sysrq_key_table[j]; j++)
 618                                         ;
 619                                 if (j != i)
 620                                         continue;
 621                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 622                         }
 623                 }
 624                 pr_cont("\n");
 625                 console_loglevel = orig_log_level;
 626         }
 627         rcu_read_unlock();
 628         rcu_sysrq_end();
 629
 630         suppress_printk = orig_suppress_printk;
 631 }
 632
 633 void handle_sysrq(int key)
 634 {
 635         if (sysrq_on())
 636                 __handle_sysrq(key, true);
 637 }
 638 EXPORT_SYMBOL(handle_sysrq);
 639
 640 #ifdef CONFIG_INPUT
 641 static int sysrq_reset_downtime_ms;
 642
 643 /* Simple translation table for the SysRq keys */
 644 static const unsigned char sysrq_xlate[KEY_CNT] =
 645         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 646         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 647         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 648         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 649         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 650         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 651         "\r\000/";                                      /* 0x60 - 0x6f */
 652
 653 struct sysrq_state {
 654         struct input_handle handle;
 655         struct work_struct reinject_work;
 656         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 657         unsigned int alt;
 658         unsigned int alt_use;
 659         unsigned int shift;
 660         unsigned int shift_use;
 661         bool active;
 662         bool need_reinject;
 663         bool reinjecting;
 664
 665         /* reset sequence handling */
 666         bool reset_canceled;
 667         bool reset_requested;
 668         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 669         int reset_seq_len;
 670         int reset_seq_cnt;
 671         int reset_seq_version;
 672         struct timer_list keyreset_timer;
 673 };
 674
 675 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 676 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 677 static unsigned int sysrq_reset_seq_len;
 678 static unsigned int sysrq_reset_seq_version = 1;
 679
 680 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 681 {
 682         int i;
 683         unsigned short key;
 684
 685         state->reset_seq_cnt = 0;
 686
 687         for (i = 0; i < sysrq_reset_seq_len; i++) {
 688                 key = sysrq_reset_seq[i];
 689
 690                 if (key == KEY_RESERVED || key > KEY_MAX)
 691                         break;
 692
 693                 __set_bit(key, state->reset_keybit);
 694                 state->reset_seq_len++;
 695
 696                 if (test_bit(key, state->key_down))
 697                         state->reset_seq_cnt++;
 698         }
 699
 700         /* Disable reset until old keys are not released */
 701         state->reset_canceled = state->reset_seq_cnt != 0;
 702
 703         state->reset_seq_version = sysrq_reset_seq_version;
 704 }
 705
 706 static void sysrq_do_reset(struct timer_list *t)
 707 {
 708         struct sysrq_state *state = from_timer(state, t, keyreset_timer);
 709
 710         state->reset_requested = true;
 711
 712         orderly_reboot();
 713 }
 714
 715 static void sysrq_handle_reset_request(struct sysrq_state *state)
 716 {
 717         if (state->reset_requested)
 718                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 719
 720         if (sysrq_reset_downtime_ms)
 721                 mod_timer(&state->keyreset_timer,
 722                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 723         else
 724                 sysrq_do_reset(&state->keyreset_timer);
 725 }
 726
 727 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 728                                         unsigned int code, int value)
 729 {
 730         if (!test_bit(code, state->reset_keybit)) {
 731                 /*
 732                  * Pressing any key _not_ in reset sequence cancels
 733                  * the reset sequence.  Also cancelling the timer in
 734                  * case additional keys were pressed after a reset
 735                  * has been requested.
 736                  */
 737                 if (value && state->reset_seq_cnt) {
 738                         state->reset_canceled = true;
 739                         del_timer(&state->keyreset_timer);
 740                 }
 741         } else if (value == 0) {
 742                 /*
 743                  * Key release - all keys in the reset sequence need
 744                  * to be pressed and held for the reset timeout
 745                  * to hold.
 746                  */
 747                 del_timer(&state->keyreset_timer);
 748
 749                 if (--state->reset_seq_cnt == 0)
 750                         state->reset_canceled = false;
 751         } else if (value == 1) {
 752                 /* key press, not autorepeat */
 753                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 754                     !state->reset_canceled) {
 755                         sysrq_handle_reset_request(state);
 756                 }
 757         }
 758 }
 759
 760 #ifdef CONFIG_OF
 761 static void sysrq_of_get_keyreset_config(void)
 762 {
 763         u32 key;
 764         struct device_node *np;
 765         struct property *prop;
 766         const __be32 *p;
 767
 768         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 769         if (!np) {
 770                 pr_debug("No sysrq node found");
 771                 return;
 772         }
 773
 774         /* Reset in case a __weak definition was present */
 775         sysrq_reset_seq_len = 0;
 776
 777         of_property_for_each_u32(np, "keyset", prop, p, key) {
 778                 if (key == KEY_RESERVED || key > KEY_MAX ||
 779                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 780                         break;
 781
 782                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 783         }
 784
 785         /* Get reset timeout if any. */
 786         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 787
 788         of_node_put(np);
 789 }
 790 #else
 791 static void sysrq_of_get_keyreset_config(void)
 792 {
 793 }
 794 #endif
 795
 796 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 797 {
 798         struct sysrq_state *sysrq =
 799                         container_of(work, struct sysrq_state, reinject_work);
 800         struct input_handle *handle = &sysrq->handle;
 801         unsigned int alt_code = sysrq->alt_use;
 802
 803         if (sysrq->need_reinject) {
 804                 /* we do not want the assignment to be reordered */
 805                 sysrq->reinjecting = true;
 806                 mb();
 807
 808                 /* Simulate press and release of Alt + SysRq */
 809                 input_inject_event(handle, EV_KEY, alt_code, 1);
 810                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 811                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 812
 813                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 814                 input_inject_event(handle, EV_KEY, alt_code, 0);
 815                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 816
 817                 mb();
 818                 sysrq->reinjecting = false;
 819         }
 820 }
 821
 822 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 823                                   unsigned int code, int value)
 824 {
 825         bool was_active = sysrq->active;
 826         bool suppress;
 827
 828         switch (code) {
 829
 830         case KEY_LEFTALT:
 831         case KEY_RIGHTALT:
 832                 if (!value) {
 833                         /* One of ALTs is being released */
 834                         if (sysrq->active && code == sysrq->alt_use)
 835                                 sysrq->active = false;
 836
 837                         sysrq->alt = KEY_RESERVED;
 838
 839                 } else if (value != 2) {
 840                         sysrq->alt = code;
 841                         sysrq->need_reinject = false;
 842                 }
 843                 break;
 844
 845         case KEY_LEFTSHIFT:
 846         case KEY_RIGHTSHIFT:
 847                 if (!value)
 848                         sysrq->shift = KEY_RESERVED;
 849                 else if (value != 2)
 850                         sysrq->shift = code;
 851                 break;
 852
 853         case KEY_SYSRQ:
 854                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 855                         sysrq->active = true;
 856                         sysrq->alt_use = sysrq->alt;
 857                         /* either RESERVED (for released) or actual code */
 858                         sysrq->shift_use = sysrq->shift;
 859                         /*
 860                          * If nothing else will be pressed we'll need
 861                          * to re-inject Alt-SysRq keysroke.
 862                          */
 863                         sysrq->need_reinject = true;
 864                 }
 865
 866                 /*
 867                  * Pretend that sysrq was never pressed at all. This
 868                  * is needed to properly handle KGDB which will try
 869                  * to release all keys after exiting debugger. If we
 870                  * do not clear key bit it KGDB will end up sending
 871                  * release events for Alt and SysRq, potentially
 872                  * triggering print screen function.
 873                  */
 874                 if (sysrq->active)
 875                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 876
 877                 break;
 878
 879         default:
 880                 if (sysrq->active && value && value != 2) {
 881                         unsigned char c = sysrq_xlate[code];
 882
 883                         sysrq->need_reinject = false;
 884                         if (sysrq->shift_use != KEY_RESERVED)
 885                                 c = toupper(c);
 886                         __handle_sysrq(c, true);
 887                 }
 888                 break;
 889         }
 890
 891         suppress = sysrq->active;
 892
 893         if (!sysrq->active) {
 894
 895                 /*
 896                  * See if reset sequence has changed since the last time.
 897                  */
 898                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 899                         sysrq_parse_reset_sequence(sysrq);
 900
 901                 /*
 902                  * If we are not suppressing key presses keep track of
 903                  * keyboard state so we can release keys that have been
 904                  * pressed before entering SysRq mode.
 905                  */
 906                 if (value)
 907                         set_bit(code, sysrq->key_down);
 908                 else
 909                         clear_bit(code, sysrq->key_down);
 910
 911                 if (was_active)
 912                         schedule_work(&sysrq->reinject_work);
 913
 914                 /* Check for reset sequence */
 915                 sysrq_detect_reset_sequence(sysrq, code, value);
 916
 917         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 918                 /*
 919                  * Pass on release events for keys that was pressed before
 920                  * entering SysRq mode.
 921                  */
 922                 suppress = false;
 923         }
 924
 925         return suppress;
 926 }
 927
 928 static bool sysrq_filter(struct input_handle *handle,
 929                          unsigned int type, unsigned int code, int value)
 930 {
 931         struct sysrq_state *sysrq = handle->private;
 932         bool suppress;
 933
 934         /*
 935          * Do not filter anything if we are in the process of re-injecting
 936          * Alt+SysRq combination.
 937          */
 938         if (sysrq->reinjecting)
 939                 return false;
 940
 941         switch (type) {
 942
 943         case EV_SYN:
 944                 suppress = false;
 945                 break;
 946
 947         case EV_KEY:
 948                 suppress = sysrq_handle_keypress(sysrq, code, value);
 949                 break;
 950
 951         default:
 952                 suppress = sysrq->active;
 953                 break;
 954         }
 955
 956         return suppress;
 957 }
 958
 959 static int sysrq_connect(struct input_handler *handler,
 960                          struct input_dev *dev,
 961                          const struct input_device_id *id)
 962 {
 963         struct sysrq_state *sysrq;
 964         int error;
 965
 966         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 967         if (!sysrq)
 968                 return -ENOMEM;
 969
 970         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 971
 972         sysrq->handle.dev = dev;
 973         sysrq->handle.handler = handler;
 974         sysrq->handle.name = "sysrq";
 975         sysrq->handle.private = sysrq;
 976         timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 977
 978         error = input_register_handle(&sysrq->handle);
 979         if (error) {
 980                 pr_err("Failed to register input sysrq handler, error %d\n",
 981                         error);
 982                 goto err_free;
 983         }
 984
 985         error = input_open_device(&sysrq->handle);
 986         if (error) {
 987                 pr_err("Failed to open input device, error %d\n", error);
 988                 goto err_unregister;
 989         }
 990
 991         return 0;
 992
 993  err_unregister:
 994         input_unregister_handle(&sysrq->handle);
 995  err_free:
 996         kfree(sysrq);
 997         return error;
 998 }
 999
1000 static void sysrq_disconnect(struct input_handle *handle)
1001 {
1002         struct sysrq_state *sysrq = handle->private;
1003
1004         input_close_device(handle);
1005         cancel_work_sync(&sysrq->reinject_work);
1006         del_timer_sync(&sysrq->keyreset_timer);
1007         input_unregister_handle(handle);
1008         kfree(sysrq);
1009 }
1010
1011 /*
1012  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1013  * keyboards have SysRq key predefined and so user may add it to keymap
1014  * later, but we expect all such keyboards to have left alt.
1015  */
1016 static const struct input_device_id sysrq_ids[] = {
1017         {
1018                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1019                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
1020                 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1021                 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1022         },
1023         { },
1024 };
1025
1026 static struct input_handler sysrq_handler = {
1027         .filter         = sysrq_filter,
1028         .connect        = sysrq_connect,
1029         .disconnect     = sysrq_disconnect,
1030         .name           = "sysrq",
1031         .id_table       = sysrq_ids,
1032 };
1033
1034 static inline void sysrq_register_handler(void)
1035 {
1036         int error;
1037
1038         sysrq_of_get_keyreset_config();
1039
1040         error = input_register_handler(&sysrq_handler);
1041         if (error)
1042                 pr_err("Failed to register input handler, error %d", error);
1043 }
1044
1045 static inline void sysrq_unregister_handler(void)
1046 {
1047         input_unregister_handler(&sysrq_handler);
1048 }
1049
1050 static int sysrq_reset_seq_param_set(const char *buffer,
1051                                      const struct kernel_param *kp)
1052 {
1053         unsigned long val;
1054         int error;
1055
1056         error = kstrtoul(buffer, 0, &val);
1057         if (error < 0)
1058                 return error;
1059
1060         if (val > KEY_MAX)
1061                 return -EINVAL;
1062
1063         *((unsigned short *)kp->arg) = val;
1064         sysrq_reset_seq_version++;
1065
1066         return 0;
1067 }
1068
1069 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1070         .get    = param_get_ushort,
1071         .set    = sysrq_reset_seq_param_set,
1072 };
1073
1074 #define param_check_sysrq_reset_seq(name, p)    \
1075         __param_check(name, p, unsigned short)
1076
1077 /*
1078  * not really modular, but the easiest way to keep compat with existing
1079  * bootargs behaviour is to continue using module_param here.
1080  */
1081 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1082                          &sysrq_reset_seq_len, 0644);
1083
1084 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1085
1086 #else
1087
1088 static inline void sysrq_register_handler(void)
1089 {
1090 }
1091
1092 static inline void sysrq_unregister_handler(void)
1093 {
1094 }
1095
1096 #endif /* CONFIG_INPUT */
1097
1098 int sysrq_toggle_support(int enable_mask)
1099 {
1100         bool was_enabled = sysrq_on();
1101
1102         sysrq_enabled = enable_mask;
1103
1104         if (was_enabled != sysrq_on()) {
1105                 if (sysrq_on())
1106                         sysrq_register_handler();
1107                 else
1108                         sysrq_unregister_handler();
1109         }
1110
1111         return 0;
1112 }
1113 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1114
1115 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p,
1116                                 const struct sysrq_key_op *remove_op_p)
1117 {
1118         int retval;
1119
1120         spin_lock(&sysrq_key_table_lock);
1121         if (__sysrq_get_key_op(key) == remove_op_p) {
1122                 __sysrq_put_key_op(key, insert_op_p);
1123                 retval = 0;
1124         } else {
1125                 retval = -1;
1126         }
1127         spin_unlock(&sysrq_key_table_lock);
1128
1129         /*
1130          * A concurrent __handle_sysrq either got the old op or the new op.
1131          * Wait for it to go away before returning, so the code for an old
1132          * op is not freed (eg. on module unload) while it is in use.
1133          */
1134         synchronize_rcu();
1135
1136         return retval;
1137 }
1138
1139 int register_sysrq_key(int key, const struct sysrq_key_op *op_p)
1140 {
1141         return __sysrq_swap_key_ops(key, op_p, NULL);
1142 }
1143 EXPORT_SYMBOL(register_sysrq_key);
1144
1145 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)
1146 {
1147         return __sysrq_swap_key_ops(key, NULL, op_p);
1148 }
1149 EXPORT_SYMBOL(unregister_sysrq_key);
1150
1151 #ifdef CONFIG_PROC_FS
1152 /*
1153  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1154  */
1155 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1156                                    size_t count, loff_t *ppos)
1157 {
1158         if (count) {
1159                 char c;
1160
1161                 if (get_user(c, buf))
1162                         return -EFAULT;
1163                 __handle_sysrq(c, false);
1164         }
1165
1166         return count;
1167 }
1168
1169 static const struct proc_ops sysrq_trigger_proc_ops = {
1170         .proc_write     = write_sysrq_trigger,
1171         .proc_lseek     = noop_llseek,
1172 };
1173
1174 static void sysrq_init_procfs(void)
1175 {
1176         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1177                          &sysrq_trigger_proc_ops))
1178                 pr_err("Failed to register proc interface\n");
1179 }
1180
1181 #else
1182
1183 static inline void sysrq_init_procfs(void)
1184 {
1185 }
1186
1187 #endif /* CONFIG_PROC_FS */
1188
1189 static int __init sysrq_init(void)
1190 {
1191         sysrq_init_procfs();
1192
1193         if (sysrq_on())
1194                 sysrq_register_handler();
1195
1196         return 0;
1197 }
1198 device_initcall(sysrq_init);