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