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