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/signal.h>
  18 #include <linux/sched/rt.h>
  19 #include <linux/sched/debug.h>
  20 #include <linux/sched/task.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/mm.h>
  23 #include <linux/fs.h>
  24 #include <linux/mount.h>
  25 #include <linux/kdev_t.h>
  26 #include <linux/major.h>
  27 #include <linux/reboot.h>
  28 #include <linux/sysrq.h>
  29 #include <linux/kbd_kern.h>
  30 #include <linux/proc_fs.h>
  31 #include <linux/nmi.h>
  32 #include <linux/quotaops.h>
  33 #include <linux/perf_event.h>
  34 #include <linux/kernel.h>
  35 #include <linux/module.h>
  36 #include <linux/suspend.h>
  37 #include <linux/writeback.h>
  38 #include <linux/swap.h>
  39 #include <linux/spinlock.h>
  40 #include <linux/vt_kern.h>
  41 #include <linux/workqueue.h>
  42 #include <linux/hrtimer.h>
  43 #include <linux/oom.h>
  44 #include <linux/slab.h>
  45 #include <linux/input.h>
  46 #include <linux/uaccess.h>
  47 #include <linux/moduleparam.h>
  48 #include <linux/jiffies.h>
  49 #include <linux/syscalls.h>
  50 #include <linux/of.h>
  51 #include <linux/rcupdate.h>
  52
  53 #include <asm/ptrace.h>
  54 #include <asm/irq_regs.h>
  55
  56 /* Whether we react on sysrq keys or just ignore them */
  57 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
  58 static bool __read_mostly sysrq_always_enabled;
  59
  60 static bool sysrq_on(void)
  61 {
  62         return sysrq_enabled || sysrq_always_enabled;
  63 }
  64
  65 /*
  66  * A value of 1 means 'all', other nonzero values are an op mask:
  67  */
  68 static bool sysrq_on_mask(int mask)
  69 {
  70         return sysrq_always_enabled ||
  71                sysrq_enabled == 1 ||
  72                (sysrq_enabled & mask);
  73 }
  74
  75 static int __init sysrq_always_enabled_setup(char *str)
  76 {
  77         sysrq_always_enabled = true;
  78         pr_info("sysrq always enabled.\n");
  79
  80         return 1;
  81 }
  82
  83 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  84
  85
  86 static void sysrq_handle_loglevel(int key)
  87 {
  88         int i;
  89
  90         i = key - '0';
  91         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
  92         pr_info("Loglevel set to %d\n", i);
  93         console_loglevel = i;
  94 }
  95 static struct sysrq_key_op sysrq_loglevel_op = {
  96         .handler        = sysrq_handle_loglevel,
  97         .help_msg       = "loglevel(0-9)",
  98         .action_msg     = "Changing Loglevel",
  99         .enable_mask    = SYSRQ_ENABLE_LOG,
 100 };
 101
 102 #ifdef CONFIG_VT
 103 static void sysrq_handle_SAK(int key)
 104 {
 105         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 106         schedule_work(SAK_work);
 107 }
 108 static struct sysrq_key_op sysrq_SAK_op = {
 109         .handler        = sysrq_handle_SAK,
 110         .help_msg       = "sak(k)",
 111         .action_msg     = "SAK",
 112         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 113 };
 114 #else
 115 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
 116 #endif
 117
 118 #ifdef CONFIG_VT
 119 static void sysrq_handle_unraw(int key)
 120 {
 121         vt_reset_unicode(fg_console);
 122 }
 123
 124 static struct sysrq_key_op sysrq_unraw_op = {
 125         .handler        = sysrq_handle_unraw,
 126         .help_msg       = "unraw(r)",
 127         .action_msg     = "Keyboard mode set to system default",
 128         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 129 };
 130 #else
 131 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
 132 #endif /* CONFIG_VT */
 133
 134 static void sysrq_handle_crash(int key)
 135 {
 136         char *killer = NULL;
 137
 138         /* we need to release the RCU read lock here,
 139          * otherwise we get an annoying
 140          * 'BUG: sleeping function called from invalid context'
 141          * complaint from the kernel before the panic.
 142          */
 143         rcu_read_unlock();
 144         panic_on_oops = 1;      /* force panic */
 145         wmb();
 146         *killer = 1;
 147 }
 148 static struct sysrq_key_op sysrq_crash_op = {
 149         .handler        = sysrq_handle_crash,
 150         .help_msg       = "crash(c)",
 151         .action_msg     = "Trigger a crash",
 152         .enable_mask    = SYSRQ_ENABLE_DUMP,
 153 };
 154
 155 static void sysrq_handle_reboot(int key)
 156 {
 157         lockdep_off();
 158         local_irq_enable();
 159         emergency_restart();
 160 }
 161 static struct sysrq_key_op sysrq_reboot_op = {
 162         .handler        = sysrq_handle_reboot,
 163         .help_msg       = "reboot(b)",
 164         .action_msg     = "Resetting",
 165         .enable_mask    = SYSRQ_ENABLE_BOOT,
 166 };
 167
 168 static void sysrq_handle_sync(int key)
 169 {
 170         emergency_sync();
 171 }
 172 static struct sysrq_key_op sysrq_sync_op = {
 173         .handler        = sysrq_handle_sync,
 174         .help_msg       = "sync(s)",
 175         .action_msg     = "Emergency Sync",
 176         .enable_mask    = SYSRQ_ENABLE_SYNC,
 177 };
 178
 179 static void sysrq_handle_show_timers(int key)
 180 {
 181         sysrq_timer_list_show();
 182 }
 183
 184 static struct sysrq_key_op sysrq_show_timers_op = {
 185         .handler        = sysrq_handle_show_timers,
 186         .help_msg       = "show-all-timers(q)",
 187         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 188 };
 189
 190 static void sysrq_handle_mountro(int key)
 191 {
 192         emergency_remount();
 193 }
 194 static struct sysrq_key_op sysrq_mountro_op = {
 195         .handler        = sysrq_handle_mountro,
 196         .help_msg       = "unmount(u)",
 197         .action_msg     = "Emergency Remount R/O",
 198         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 199 };
 200
 201 #ifdef CONFIG_LOCKDEP
 202 static void sysrq_handle_showlocks(int key)
 203 {
 204         debug_show_all_locks();
 205 }
 206
 207 static struct sysrq_key_op sysrq_showlocks_op = {
 208         .handler        = sysrq_handle_showlocks,
 209         .help_msg       = "show-all-locks(d)",
 210         .action_msg     = "Show Locks Held",
 211 };
 212 #else
 213 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
 214 #endif
 215
 216 #ifdef CONFIG_SMP
 217 static DEFINE_SPINLOCK(show_lock);
 218
 219 static void showacpu(void *dummy)
 220 {
 221         unsigned long flags;
 222
 223         /* Idle CPUs have no interesting backtrace. */
 224         if (idle_cpu(smp_processor_id()))
 225                 return;
 226
 227         spin_lock_irqsave(&show_lock, flags);
 228         pr_info("CPU%d:\n", smp_processor_id());
 229         show_stack(NULL, NULL);
 230         spin_unlock_irqrestore(&show_lock, flags);
 231 }
 232
 233 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 234 {
 235         smp_call_function(showacpu, NULL, 0);
 236 }
 237
 238 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 239
 240 static void sysrq_handle_showallcpus(int key)
 241 {
 242         /*
 243          * Fall back to the workqueue based printing if the
 244          * backtrace printing did not succeed or the
 245          * architecture has no support for it:
 246          */
 247         if (!trigger_all_cpu_backtrace()) {
 248                 struct pt_regs *regs = get_irq_regs();
 249
 250                 if (regs) {
 251                         pr_info("CPU%d:\n", smp_processor_id());
 252                         show_regs(regs);
 253                 }
 254                 schedule_work(&sysrq_showallcpus);
 255         }
 256 }
 257
 258 static struct sysrq_key_op sysrq_showallcpus_op = {
 259         .handler        = sysrq_handle_showallcpus,
 260         .help_msg       = "show-backtrace-all-active-cpus(l)",
 261         .action_msg     = "Show backtrace of all active CPUs",
 262         .enable_mask    = SYSRQ_ENABLE_DUMP,
 263 };
 264 #endif
 265
 266 static void sysrq_handle_showregs(int key)
 267 {
 268         struct pt_regs *regs = get_irq_regs();
 269         if (regs)
 270                 show_regs(regs);
 271         perf_event_print_debug();
 272 }
 273 static struct sysrq_key_op sysrq_showregs_op = {
 274         .handler        = sysrq_handle_showregs,
 275         .help_msg       = "show-registers(p)",
 276         .action_msg     = "Show Regs",
 277         .enable_mask    = SYSRQ_ENABLE_DUMP,
 278 };
 279
 280 static void sysrq_handle_showstate(int key)
 281 {
 282         show_state();
 283         show_workqueue_state();
 284 }
 285 static struct sysrq_key_op sysrq_showstate_op = {
 286         .handler        = sysrq_handle_showstate,
 287         .help_msg       = "show-task-states(t)",
 288         .action_msg     = "Show State",
 289         .enable_mask    = SYSRQ_ENABLE_DUMP,
 290 };
 291
 292 static void sysrq_handle_showstate_blocked(int key)
 293 {
 294         show_state_filter(TASK_UNINTERRUPTIBLE);
 295 }
 296 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 297         .handler        = sysrq_handle_showstate_blocked,
 298         .help_msg       = "show-blocked-tasks(w)",
 299         .action_msg     = "Show Blocked State",
 300         .enable_mask    = SYSRQ_ENABLE_DUMP,
 301 };
 302
 303 #ifdef CONFIG_TRACING
 304 #include <linux/ftrace.h>
 305
 306 static void sysrq_ftrace_dump(int key)
 307 {
 308         ftrace_dump(DUMP_ALL);
 309 }
 310 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 311         .handler        = sysrq_ftrace_dump,
 312         .help_msg       = "dump-ftrace-buffer(z)",
 313         .action_msg     = "Dump ftrace buffer",
 314         .enable_mask    = SYSRQ_ENABLE_DUMP,
 315 };
 316 #else
 317 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
 318 #endif
 319
 320 static void sysrq_handle_showmem(int key)
 321 {
 322         show_mem(0, NULL);
 323 }
 324 static struct sysrq_key_op sysrq_showmem_op = {
 325         .handler        = sysrq_handle_showmem,
 326         .help_msg       = "show-memory-usage(m)",
 327         .action_msg     = "Show Memory",
 328         .enable_mask    = SYSRQ_ENABLE_DUMP,
 329 };
 330
 331 /*
 332  * Signal sysrq helper function.  Sends a signal to all user processes.
 333  */
 334 static void send_sig_all(int sig)
 335 {
 336         struct task_struct *p;
 337
 338         read_lock(&tasklist_lock);
 339         for_each_process(p) {
 340                 if (p->flags & PF_KTHREAD)
 341                         continue;
 342                 if (is_global_init(p))
 343                         continue;
 344
 345                 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
 346         }
 347         read_unlock(&tasklist_lock);
 348 }
 349
 350 static void sysrq_handle_term(int key)
 351 {
 352         send_sig_all(SIGTERM);
 353         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 354 }
 355 static struct sysrq_key_op sysrq_term_op = {
 356         .handler        = sysrq_handle_term,
 357         .help_msg       = "terminate-all-tasks(e)",
 358         .action_msg     = "Terminate All Tasks",
 359         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 360 };
 361
 362 static void moom_callback(struct work_struct *ignored)
 363 {
 364         const gfp_t gfp_mask = GFP_KERNEL;
 365         struct oom_control oc = {
 366                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 367                 .nodemask = NULL,
 368                 .memcg = NULL,
 369                 .gfp_mask = gfp_mask,
 370                 .order = -1,
 371         };
 372
 373         mutex_lock(&oom_lock);
 374         if (!out_of_memory(&oc))
 375                 pr_info("OOM request ignored. No task eligible\n");
 376         mutex_unlock(&oom_lock);
 377 }
 378
 379 static DECLARE_WORK(moom_work, moom_callback);
 380
 381 static void sysrq_handle_moom(int key)
 382 {
 383         schedule_work(&moom_work);
 384 }
 385 static struct sysrq_key_op sysrq_moom_op = {
 386         .handler        = sysrq_handle_moom,
 387         .help_msg       = "memory-full-oom-kill(f)",
 388         .action_msg     = "Manual OOM execution",
 389         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 390 };
 391
 392 #ifdef CONFIG_BLOCK
 393 static void sysrq_handle_thaw(int key)
 394 {
 395         emergency_thaw_all();
 396 }
 397 static struct sysrq_key_op sysrq_thaw_op = {
 398         .handler        = sysrq_handle_thaw,
 399         .help_msg       = "thaw-filesystems(j)",
 400         .action_msg     = "Emergency Thaw of all frozen filesystems",
 401         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 402 };
 403 #endif
 404
 405 static void sysrq_handle_kill(int key)
 406 {
 407         send_sig_all(SIGKILL);
 408         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 409 }
 410 static struct sysrq_key_op sysrq_kill_op = {
 411         .handler        = sysrq_handle_kill,
 412         .help_msg       = "kill-all-tasks(i)",
 413         .action_msg     = "Kill All Tasks",
 414         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 415 };
 416
 417 static void sysrq_handle_unrt(int key)
 418 {
 419         normalize_rt_tasks();
 420 }
 421 static struct sysrq_key_op sysrq_unrt_op = {
 422         .handler        = sysrq_handle_unrt,
 423         .help_msg       = "nice-all-RT-tasks(n)",
 424         .action_msg     = "Nice All RT Tasks",
 425         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 426 };
 427
 428 /* Key Operations table and lock */
 429 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 430
 431 static struct sysrq_key_op *sysrq_key_table[36] = {
 432         &sysrq_loglevel_op,             /* 0 */
 433         &sysrq_loglevel_op,             /* 1 */
 434         &sysrq_loglevel_op,             /* 2 */
 435         &sysrq_loglevel_op,             /* 3 */
 436         &sysrq_loglevel_op,             /* 4 */
 437         &sysrq_loglevel_op,             /* 5 */
 438         &sysrq_loglevel_op,             /* 6 */
 439         &sysrq_loglevel_op,             /* 7 */
 440         &sysrq_loglevel_op,             /* 8 */
 441         &sysrq_loglevel_op,             /* 9 */
 442
 443         /*
 444          * a: Don't use for system provided sysrqs, it is handled specially on
 445          * sparc and will never arrive.
 446          */
 447         NULL,                           /* a */
 448         &sysrq_reboot_op,               /* b */
 449         &sysrq_crash_op,                /* c */
 450         &sysrq_showlocks_op,            /* d */
 451         &sysrq_term_op,                 /* e */
 452         &sysrq_moom_op,                 /* f */
 453         /* g: May be registered for the kernel debugger */
 454         NULL,                           /* g */
 455         NULL,                           /* h - reserved for help */
 456         &sysrq_kill_op,                 /* i */
 457 #ifdef CONFIG_BLOCK
 458         &sysrq_thaw_op,                 /* j */
 459 #else
 460         NULL,                           /* j */
 461 #endif
 462         &sysrq_SAK_op,                  /* k */
 463 #ifdef CONFIG_SMP
 464         &sysrq_showallcpus_op,          /* l */
 465 #else
 466         NULL,                           /* l */
 467 #endif
 468         &sysrq_showmem_op,              /* m */
 469         &sysrq_unrt_op,                 /* n */
 470         /* o: This will often be registered as 'Off' at init time */
 471         NULL,                           /* o */
 472         &sysrq_showregs_op,             /* p */
 473         &sysrq_show_timers_op,          /* q */
 474         &sysrq_unraw_op,                /* r */
 475         &sysrq_sync_op,                 /* s */
 476         &sysrq_showstate_op,            /* t */
 477         &sysrq_mountro_op,              /* u */
 478         /* v: May be registered for frame buffer console restore */
 479         NULL,                           /* v */
 480         &sysrq_showstate_blocked_op,    /* w */
 481         /* x: May be registered on mips for TLB dump */
 482         /* x: May be registered on ppc/powerpc for xmon */
 483         /* x: May be registered on sparc64 for global PMU dump */
 484         /* x: May be registered on x86_64 for disabling secure boot */
 485         NULL,                           /* x */
 486         /* y: May be registered on sparc64 for global register dump */
 487         NULL,                           /* y */
 488         &sysrq_ftrace_dump_op,          /* z */
 489 };
 490
 491 /* key2index calculation, -1 on invalid index */
 492 static int sysrq_key_table_key2index(int key)
 493 {
 494         int retval;
 495
 496         if ((key >= '0') && (key <= '9'))
 497                 retval = key - '0';
 498         else if ((key >= 'a') && (key <= 'z'))
 499                 retval = key + 10 - 'a';
 500         else
 501                 retval = -1;
 502         return retval;
 503 }
 504
 505 /*
 506  * get and put functions for the table, exposed to modules.
 507  */
 508 struct sysrq_key_op *__sysrq_get_key_op(int key)
 509 {
 510         struct sysrq_key_op *op_p = NULL;
 511         int i;
 512
 513         i = sysrq_key_table_key2index(key);
 514         if (i != -1)
 515                 op_p = sysrq_key_table[i];
 516
 517         return op_p;
 518 }
 519
 520 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 521 {
 522         int i = sysrq_key_table_key2index(key);
 523
 524         if (i != -1)
 525                 sysrq_key_table[i] = op_p;
 526 }
 527
 528 void __handle_sysrq(int key, unsigned int from)
 529 {
 530         struct sysrq_key_op *op_p;
 531         int orig_log_level;
 532         int i;
 533
 534         rcu_sysrq_start();
 535         rcu_read_lock();
 536         /*
 537          * Raise the apparent loglevel to maximum so that the sysrq header
 538          * is shown to provide the user with positive feedback.  We do not
 539          * simply emit this at KERN_EMERG as that would change message
 540          * routing in the consumers of /proc/kmsg.
 541          */
 542         orig_log_level = console_loglevel;
 543         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 544         pr_info("SysRq : ");
 545
 546         op_p = __sysrq_get_key_op(key);
 547         if (op_p) {
 548                 /* Ban synthetic events from some sysrq functionality */
 549                 if ((from == SYSRQ_FROM_PROC || from == SYSRQ_FROM_SYNTHETIC) &&
 550                     op_p->enable_mask & SYSRQ_DISABLE_USERSPACE)
 551                         printk("This sysrq operation is disabled from userspace.\n");
 552                 /*
 553                  * Should we check for enabled operations (/proc/sysrq-trigger
 554                  * should not) and is the invoked operation enabled?
 555                  */
 556                 if (from == SYSRQ_FROM_KERNEL || sysrq_on_mask(op_p->enable_mask)) {
 557                         pr_cont("%s\n", op_p->action_msg);
 558                         console_loglevel = orig_log_level;
 559                         op_p->handler(key);
 560                 } else {
 561                         pr_cont("This sysrq operation is disabled.\n");
 562                 }
 563         } else {
 564                 pr_cont("HELP : ");
 565                 /* Only print the help msg once per handler */
 566                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 567                         if (sysrq_key_table[i]) {
 568                                 int j;
 569
 570                                 for (j = 0; sysrq_key_table[i] !=
 571                                                 sysrq_key_table[j]; j++)
 572                                         ;
 573                                 if (j != i)
 574                                         continue;
 575                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 576                         }
 577                 }
 578                 pr_cont("\n");
 579                 console_loglevel = orig_log_level;
 580         }
 581         rcu_read_unlock();
 582         rcu_sysrq_end();
 583 }
 584
 585 void handle_sysrq(int key)
 586 {
 587         if (sysrq_on())
 588                 __handle_sysrq(key, SYSRQ_FROM_KERNEL);
 589 }
 590 EXPORT_SYMBOL(handle_sysrq);
 591
 592 #ifdef CONFIG_INPUT
 593 static int sysrq_reset_downtime_ms;
 594
 595 /* Simple translation table for the SysRq keys */
 596 static const unsigned char sysrq_xlate[KEY_CNT] =
 597         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 598         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 599         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 600         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 601         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 602         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 603         "\r\000/";                                      /* 0x60 - 0x6f */
 604
 605 struct sysrq_state {
 606         struct input_handle handle;
 607         struct work_struct reinject_work;
 608         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 609         unsigned int alt;
 610         unsigned int alt_use;
 611         bool active;
 612         bool need_reinject;
 613         bool reinjecting;
 614
 615         /* reset sequence handling */
 616         bool reset_canceled;
 617         bool reset_requested;
 618         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 619         int reset_seq_len;
 620         int reset_seq_cnt;
 621         int reset_seq_version;
 622         struct timer_list keyreset_timer;
 623 };
 624
 625 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 626 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 627 static unsigned int sysrq_reset_seq_len;
 628 static unsigned int sysrq_reset_seq_version = 1;
 629
 630 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 631 {
 632         int i;
 633         unsigned short key;
 634
 635         state->reset_seq_cnt = 0;
 636
 637         for (i = 0; i < sysrq_reset_seq_len; i++) {
 638                 key = sysrq_reset_seq[i];
 639
 640                 if (key == KEY_RESERVED || key > KEY_MAX)
 641                         break;
 642
 643                 __set_bit(key, state->reset_keybit);
 644                 state->reset_seq_len++;
 645
 646                 if (test_bit(key, state->key_down))
 647                         state->reset_seq_cnt++;
 648         }
 649
 650         /* Disable reset until old keys are not released */
 651         state->reset_canceled = state->reset_seq_cnt != 0;
 652
 653         state->reset_seq_version = sysrq_reset_seq_version;
 654 }
 655
 656 static void sysrq_do_reset(unsigned long _state)
 657 {
 658         struct sysrq_state *state = (struct sysrq_state *) _state;
 659
 660         state->reset_requested = true;
 661
 662         sys_sync();
 663         kernel_restart(NULL);
 664 }
 665
 666 static void sysrq_handle_reset_request(struct sysrq_state *state)
 667 {
 668         if (state->reset_requested)
 669                 __handle_sysrq(sysrq_xlate[KEY_B], SYSRQ_FROM_KERNEL);
 670
 671         if (sysrq_reset_downtime_ms)
 672                 mod_timer(&state->keyreset_timer,
 673                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 674         else
 675                 sysrq_do_reset((unsigned long)state);
 676 }
 677
 678 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 679                                         unsigned int code, int value)
 680 {
 681         if (!test_bit(code, state->reset_keybit)) {
 682                 /*
 683                  * Pressing any key _not_ in reset sequence cancels
 684                  * the reset sequence.  Also cancelling the timer in
 685                  * case additional keys were pressed after a reset
 686                  * has been requested.
 687                  */
 688                 if (value && state->reset_seq_cnt) {
 689                         state->reset_canceled = true;
 690                         del_timer(&state->keyreset_timer);
 691                 }
 692         } else if (value == 0) {
 693                 /*
 694                  * Key release - all keys in the reset sequence need
 695                  * to be pressed and held for the reset timeout
 696                  * to hold.
 697                  */
 698                 del_timer(&state->keyreset_timer);
 699
 700                 if (--state->reset_seq_cnt == 0)
 701                         state->reset_canceled = false;
 702         } else if (value == 1) {
 703                 /* key press, not autorepeat */
 704                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 705                     !state->reset_canceled) {
 706                         sysrq_handle_reset_request(state);
 707                 }
 708         }
 709 }
 710
 711 #ifdef CONFIG_OF
 712 static void sysrq_of_get_keyreset_config(void)
 713 {
 714         u32 key;
 715         struct device_node *np;
 716         struct property *prop;
 717         const __be32 *p;
 718
 719         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 720         if (!np) {
 721                 pr_debug("No sysrq node found");
 722                 return;
 723         }
 724
 725         /* Reset in case a __weak definition was present */
 726         sysrq_reset_seq_len = 0;
 727
 728         of_property_for_each_u32(np, "keyset", prop, p, key) {
 729                 if (key == KEY_RESERVED || key > KEY_MAX ||
 730                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 731                         break;
 732
 733                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 734         }
 735
 736         /* Get reset timeout if any. */
 737         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 738 }
 739 #else
 740 static void sysrq_of_get_keyreset_config(void)
 741 {
 742 }
 743 #endif
 744
 745 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 746 {
 747         struct sysrq_state *sysrq =
 748                         container_of(work, struct sysrq_state, reinject_work);
 749         struct input_handle *handle = &sysrq->handle;
 750         unsigned int alt_code = sysrq->alt_use;
 751
 752         if (sysrq->need_reinject) {
 753                 /* we do not want the assignment to be reordered */
 754                 sysrq->reinjecting = true;
 755                 mb();
 756
 757                 /* Simulate press and release of Alt + SysRq */
 758                 input_inject_event(handle, EV_KEY, alt_code, 1);
 759                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 760                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 761
 762                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 763                 input_inject_event(handle, EV_KEY, alt_code, 0);
 764                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 765
 766                 mb();
 767                 sysrq->reinjecting = false;
 768         }
 769 }
 770
 771 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 772                                   unsigned int code, int value)
 773 {
 774         bool was_active = sysrq->active;
 775         bool suppress;
 776
 777         switch (code) {
 778
 779         case KEY_LEFTALT:
 780         case KEY_RIGHTALT:
 781                 if (!value) {
 782                         /* One of ALTs is being released */
 783                         if (sysrq->active && code == sysrq->alt_use)
 784                                 sysrq->active = false;
 785
 786                         sysrq->alt = KEY_RESERVED;
 787
 788                 } else if (value != 2) {
 789                         sysrq->alt = code;
 790                         sysrq->need_reinject = false;
 791                 }
 792                 break;
 793
 794         case KEY_SYSRQ:
 795                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 796                         sysrq->active = true;
 797                         sysrq->alt_use = sysrq->alt;
 798                         /*
 799                          * If nothing else will be pressed we'll need
 800                          * to re-inject Alt-SysRq keysroke.
 801                          */
 802                         sysrq->need_reinject = true;
 803                 }
 804
 805                 /*
 806                  * Pretend that sysrq was never pressed at all. This
 807                  * is needed to properly handle KGDB which will try
 808                  * to release all keys after exiting debugger. If we
 809                  * do not clear key bit it KGDB will end up sending
 810                  * release events for Alt and SysRq, potentially
 811                  * triggering print screen function.
 812                  */
 813                 if (sysrq->active)
 814                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 815
 816                 break;
 817
 818         default:
 819                 if (sysrq->active && value && value != 2) {
 820                         int from = sysrq->handle.dev->flags & INPUTDEV_FLAGS_SYNTHETIC ?
 821                                         SYSRQ_FROM_SYNTHETIC : 0;
 822                         sysrq->need_reinject = false;
 823                         __handle_sysrq(sysrq_xlate[code], from);
 824                 }
 825                 break;
 826         }
 827
 828         suppress = sysrq->active;
 829
 830         if (!sysrq->active) {
 831
 832                 /*
 833                  * See if reset sequence has changed since the last time.
 834                  */
 835                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 836                         sysrq_parse_reset_sequence(sysrq);
 837
 838                 /*
 839                  * If we are not suppressing key presses keep track of
 840                  * keyboard state so we can release keys that have been
 841                  * pressed before entering SysRq mode.
 842                  */
 843                 if (value)
 844                         set_bit(code, sysrq->key_down);
 845                 else
 846                         clear_bit(code, sysrq->key_down);
 847
 848                 if (was_active)
 849                         schedule_work(&sysrq->reinject_work);
 850
 851                 /* Check for reset sequence */
 852                 sysrq_detect_reset_sequence(sysrq, code, value);
 853
 854         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 855                 /*
 856                  * Pass on release events for keys that was pressed before
 857                  * entering SysRq mode.
 858                  */
 859                 suppress = false;
 860         }
 861
 862         return suppress;
 863 }
 864
 865 static bool sysrq_filter(struct input_handle *handle,
 866                          unsigned int type, unsigned int code, int value)
 867 {
 868         struct sysrq_state *sysrq = handle->private;
 869         bool suppress;
 870
 871         /*
 872          * Do not filter anything if we are in the process of re-injecting
 873          * Alt+SysRq combination.
 874          */
 875         if (sysrq->reinjecting)
 876                 return false;
 877
 878         switch (type) {
 879
 880         case EV_SYN:
 881                 suppress = false;
 882                 break;
 883
 884         case EV_KEY:
 885                 suppress = sysrq_handle_keypress(sysrq, code, value);
 886                 break;
 887
 888         default:
 889                 suppress = sysrq->active;
 890                 break;
 891         }
 892
 893         return suppress;
 894 }
 895
 896 static int sysrq_connect(struct input_handler *handler,
 897                          struct input_dev *dev,
 898                          const struct input_device_id *id)
 899 {
 900         struct sysrq_state *sysrq;
 901         int error;
 902
 903         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 904         if (!sysrq)
 905                 return -ENOMEM;
 906
 907         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 908
 909         sysrq->handle.dev = dev;
 910         sysrq->handle.handler = handler;
 911         sysrq->handle.name = "sysrq";
 912         sysrq->handle.private = sysrq;
 913         setup_timer(&sysrq->keyreset_timer,
 914                     sysrq_do_reset, (unsigned long)sysrq);
 915
 916         error = input_register_handle(&sysrq->handle);
 917         if (error) {
 918                 pr_err("Failed to register input sysrq handler, error %d\n",
 919                         error);
 920                 goto err_free;
 921         }
 922
 923         error = input_open_device(&sysrq->handle);
 924         if (error) {
 925                 pr_err("Failed to open input device, error %d\n", error);
 926                 goto err_unregister;
 927         }
 928
 929         return 0;
 930
 931  err_unregister:
 932         input_unregister_handle(&sysrq->handle);
 933  err_free:
 934         kfree(sysrq);
 935         return error;
 936 }
 937
 938 static void sysrq_disconnect(struct input_handle *handle)
 939 {
 940         struct sysrq_state *sysrq = handle->private;
 941
 942         input_close_device(handle);
 943         cancel_work_sync(&sysrq->reinject_work);
 944         del_timer_sync(&sysrq->keyreset_timer);
 945         input_unregister_handle(handle);
 946         kfree(sysrq);
 947 }
 948
 949 /*
 950  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 951  * keyboards have SysRq key predefined and so user may add it to keymap
 952  * later, but we expect all such keyboards to have left alt.
 953  */
 954 static const struct input_device_id sysrq_ids[] = {
 955         {
 956                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 957                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 958                 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
 959                 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
 960         },
 961         { },
 962 };
 963
 964 static struct input_handler sysrq_handler = {
 965         .filter         = sysrq_filter,
 966         .connect        = sysrq_connect,
 967         .disconnect     = sysrq_disconnect,
 968         .name           = "sysrq",
 969         .id_table       = sysrq_ids,
 970 };
 971
 972 static bool sysrq_handler_registered;
 973
 974 static inline void sysrq_register_handler(void)
 975 {
 976         int error;
 977
 978         sysrq_of_get_keyreset_config();
 979
 980         error = input_register_handler(&sysrq_handler);
 981         if (error)
 982                 pr_err("Failed to register input handler, error %d", error);
 983         else
 984                 sysrq_handler_registered = true;
 985 }
 986
 987 static inline void sysrq_unregister_handler(void)
 988 {
 989         if (sysrq_handler_registered) {
 990                 input_unregister_handler(&sysrq_handler);
 991                 sysrq_handler_registered = false;
 992         }
 993 }
 994
 995 static int sysrq_reset_seq_param_set(const char *buffer,
 996                                      const struct kernel_param *kp)
 997 {
 998         unsigned long val;
 999         int error;
1000
1001         error = kstrtoul(buffer, 0, &val);
1002         if (error < 0)
1003                 return error;
1004
1005         if (val > KEY_MAX)
1006                 return -EINVAL;
1007
1008         *((unsigned short *)kp->arg) = val;
1009         sysrq_reset_seq_version++;
1010
1011         return 0;
1012 }
1013
1014 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1015         .get    = param_get_ushort,
1016         .set    = sysrq_reset_seq_param_set,
1017 };
1018
1019 #define param_check_sysrq_reset_seq(name, p)    \
1020         __param_check(name, p, unsigned short)
1021
1022 /*
1023  * not really modular, but the easiest way to keep compat with existing
1024  * bootargs behaviour is to continue using module_param here.
1025  */
1026 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1027                          &sysrq_reset_seq_len, 0644);
1028
1029 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1030
1031 #else
1032
1033 static inline void sysrq_register_handler(void)
1034 {
1035 }
1036
1037 static inline void sysrq_unregister_handler(void)
1038 {
1039 }
1040
1041 #endif /* CONFIG_INPUT */
1042
1043 int sysrq_toggle_support(int enable_mask)
1044 {
1045         bool was_enabled = sysrq_on();
1046
1047         sysrq_enabled = enable_mask;
1048
1049         if (was_enabled != sysrq_on()) {
1050                 if (sysrq_on())
1051                         sysrq_register_handler();
1052                 else
1053                         sysrq_unregister_handler();
1054         }
1055
1056         return 0;
1057 }
1058
1059 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1060                                 struct sysrq_key_op *remove_op_p)
1061 {
1062         int retval;
1063
1064         spin_lock(&sysrq_key_table_lock);
1065         if (__sysrq_get_key_op(key) == remove_op_p) {
1066                 __sysrq_put_key_op(key, insert_op_p);
1067                 retval = 0;
1068         } else {
1069                 retval = -1;
1070         }
1071         spin_unlock(&sysrq_key_table_lock);
1072
1073         /*
1074          * A concurrent __handle_sysrq either got the old op or the new op.
1075          * Wait for it to go away before returning, so the code for an old
1076          * op is not freed (eg. on module unload) while it is in use.
1077          */
1078         synchronize_rcu();
1079
1080         return retval;
1081 }
1082
1083 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1084 {
1085         return __sysrq_swap_key_ops(key, op_p, NULL);
1086 }
1087 EXPORT_SYMBOL(register_sysrq_key);
1088
1089 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1090 {
1091         return __sysrq_swap_key_ops(key, NULL, op_p);
1092 }
1093 EXPORT_SYMBOL(unregister_sysrq_key);
1094
1095 #ifdef CONFIG_PROC_FS
1096 /*
1097  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1098  */
1099 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1100                                    size_t count, loff_t *ppos)
1101 {
1102         if (count) {
1103                 char c;
1104
1105                 if (get_user(c, buf))
1106                         return -EFAULT;
1107                 __handle_sysrq(c, SYSRQ_FROM_PROC);
1108         }
1109
1110         return count;
1111 }
1112
1113 static const struct file_operations proc_sysrq_trigger_operations = {
1114         .write          = write_sysrq_trigger,
1115         .llseek         = noop_llseek,
1116 };
1117
1118 static void sysrq_init_procfs(void)
1119 {
1120         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1121                          &proc_sysrq_trigger_operations))
1122                 pr_err("Failed to register proc interface\n");
1123 }
1124
1125 #else
1126
1127 static inline void sysrq_init_procfs(void)
1128 {
1129 }
1130
1131 #endif /* CONFIG_PROC_FS */
1132
1133 static int __init sysrq_init(void)
1134 {
1135         sysrq_init_procfs();
1136
1137         if (sysrq_on())
1138                 sysrq_register_handler();
1139
1140         return 0;
1141 }
1142 device_initcall(sysrq_init);