drivers/tty/sysrq.c

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