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