drivers/tty/sysrq.c

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