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