drivers/tty/sysrq.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      Linux Magic System Request Key Hacks
   4  *
   5  *      (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   6  *      based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
   7  *
   8  *      (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
   9  *      overhauled to use key registration
  10  *      based upon discusions in irc://irc.openprojects.net/#kernelnewbies
  11  *
  12  *      Copyright (c) 2010 Dmitry Torokhov
  13  *      Input handler conversion
  14  */
  15
  16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18 #include <linux/sched/signal.h>
  19 #include <linux/sched/rt.h>
  20 #include <linux/sched/debug.h>
  21 #include <linux/sched/task.h>
  22 #include <linux/interrupt.h>
  23 #include <linux/mm.h>
  24 #include <linux/fs.h>
  25 #include <linux/mount.h>
  26 #include <linux/kdev_t.h>
  27 #include <linux/major.h>
  28 #include <linux/reboot.h>
  29 #include <linux/sysrq.h>
  30 #include <linux/kbd_kern.h>
  31 #include <linux/proc_fs.h>
  32 #include <linux/nmi.h>
  33 #include <linux/quotaops.h>
  34 #include <linux/perf_event.h>
  35 #include <linux/kernel.h>
  36 #include <linux/module.h>
  37 #include <linux/suspend.h>
  38 #include <linux/writeback.h>
  39 #include <linux/swap.h>
  40 #include <linux/spinlock.h>
  41 #include <linux/vt_kern.h>
  42 #include <linux/workqueue.h>
  43 #include <linux/hrtimer.h>
  44 #include <linux/oom.h>
  45 #include <linux/slab.h>
  46 #include <linux/input.h>
  47 #include <linux/uaccess.h>
  48 #include <linux/moduleparam.h>
  49 #include <linux/jiffies.h>
  50 #include <linux/syscalls.h>
  51 #include <linux/of.h>
  52 #include <linux/rcupdate.h>
  53
  54 #include <asm/ptrace.h>
  55 #include <asm/irq_regs.h>
  56
  57 /* Whether we react on sysrq keys or just ignore them */
  58 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
  59 static bool __read_mostly sysrq_always_enabled;
  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         /* we need to release the RCU read lock here,
 140          * otherwise we get an annoying
 141          * 'BUG: sleeping function called from invalid context'
 142          * complaint from the kernel before the panic.
 143          */
 144         rcu_read_unlock();
 145         panic_on_oops = 1;      /* force panic */
 146         wmb();
 147         *killer = 1;
 148 }
 149 static struct sysrq_key_op sysrq_crash_op = {
 150         .handler        = sysrq_handle_crash,
 151         .help_msg       = "crash(c)",
 152         .action_msg     = "Trigger a crash",
 153         .enable_mask    = SYSRQ_ENABLE_DUMP,
 154 };
 155
 156 static void sysrq_handle_reboot(int key)
 157 {
 158         lockdep_off();
 159         local_irq_enable();
 160         emergency_restart();
 161 }
 162 static struct sysrq_key_op sysrq_reboot_op = {
 163         .handler        = sysrq_handle_reboot,
 164         .help_msg       = "reboot(b)",
 165         .action_msg     = "Resetting",
 166         .enable_mask    = SYSRQ_ENABLE_BOOT,
 167 };
 168
 169 static void sysrq_handle_sync(int key)
 170 {
 171         emergency_sync();
 172 }
 173 static struct sysrq_key_op sysrq_sync_op = {
 174         .handler        = sysrq_handle_sync,
 175         .help_msg       = "sync(s)",
 176         .action_msg     = "Emergency Sync",
 177         .enable_mask    = SYSRQ_ENABLE_SYNC,
 178 };
 179
 180 static void sysrq_handle_show_timers(int key)
 181 {
 182         sysrq_timer_list_show();
 183 }
 184
 185 static struct sysrq_key_op sysrq_show_timers_op = {
 186         .handler        = sysrq_handle_show_timers,
 187         .help_msg       = "show-all-timers(q)",
 188         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 189 };
 190
 191 static void sysrq_handle_mountro(int key)
 192 {
 193         emergency_remount();
 194 }
 195 static struct sysrq_key_op sysrq_mountro_op = {
 196         .handler        = sysrq_handle_mountro,
 197         .help_msg       = "unmount(u)",
 198         .action_msg     = "Emergency Remount R/O",
 199         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 200 };
 201
 202 #ifdef CONFIG_LOCKDEP
 203 static void sysrq_handle_showlocks(int key)
 204 {
 205         debug_show_all_locks();
 206 }
 207
 208 static struct sysrq_key_op sysrq_showlocks_op = {
 209         .handler        = sysrq_handle_showlocks,
 210         .help_msg       = "show-all-locks(d)",
 211         .action_msg     = "Show Locks Held",
 212 };
 213 #else
 214 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
 215 #endif
 216
 217 #ifdef CONFIG_SMP
 218 static DEFINE_SPINLOCK(show_lock);
 219
 220 static void showacpu(void *dummy)
 221 {
 222         unsigned long flags;
 223
 224         /* Idle CPUs have no interesting backtrace. */
 225         if (idle_cpu(smp_processor_id()))
 226                 return;
 227
 228         spin_lock_irqsave(&show_lock, flags);
 229         pr_info("CPU%d:\n", smp_processor_id());
 230         show_stack(NULL, NULL);
 231         spin_unlock_irqrestore(&show_lock, flags);
 232 }
 233
 234 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 235 {
 236         smp_call_function(showacpu, NULL, 0);
 237 }
 238
 239 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 240
 241 static void sysrq_handle_showallcpus(int key)
 242 {
 243         /*
 244          * Fall back to the workqueue based printing if the
 245          * backtrace printing did not succeed or the
 246          * architecture has no support for it:
 247          */
 248         if (!trigger_all_cpu_backtrace()) {
 249                 struct pt_regs *regs = NULL;
 250
 251                 if (in_irq())
 252                         regs = get_irq_regs();
 253                 if (regs) {
 254                         pr_info("CPU%d:\n", smp_processor_id());
 255                         show_regs(regs);
 256                 }
 257                 schedule_work(&sysrq_showallcpus);
 258         }
 259 }
 260
 261 static struct sysrq_key_op sysrq_showallcpus_op = {
 262         .handler        = sysrq_handle_showallcpus,
 263         .help_msg       = "show-backtrace-all-active-cpus(l)",
 264         .action_msg     = "Show backtrace of all active CPUs",
 265         .enable_mask    = SYSRQ_ENABLE_DUMP,
 266 };
 267 #endif
 268
 269 static void sysrq_handle_showregs(int key)
 270 {
 271         struct pt_regs *regs = NULL;
 272
 273         if (in_irq())
 274                 regs = get_irq_regs();
 275         if (regs)
 276                 show_regs(regs);
 277         perf_event_print_debug();
 278 }
 279 static struct sysrq_key_op sysrq_showregs_op = {
 280         .handler        = sysrq_handle_showregs,
 281         .help_msg       = "show-registers(p)",
 282         .action_msg     = "Show Regs",
 283         .enable_mask    = SYSRQ_ENABLE_DUMP,
 284 };
 285
 286 static void sysrq_handle_showstate(int key)
 287 {
 288         show_state();
 289         show_workqueue_state();
 290 }
 291 static struct sysrq_key_op sysrq_showstate_op = {
 292         .handler        = sysrq_handle_showstate,
 293         .help_msg       = "show-task-states(t)",
 294         .action_msg     = "Show State",
 295         .enable_mask    = SYSRQ_ENABLE_DUMP,
 296 };
 297
 298 static void sysrq_handle_showstate_blocked(int key)
 299 {
 300         show_state_filter(TASK_UNINTERRUPTIBLE);
 301 }
 302 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 303         .handler        = sysrq_handle_showstate_blocked,
 304         .help_msg       = "show-blocked-tasks(w)",
 305         .action_msg     = "Show Blocked State",
 306         .enable_mask    = SYSRQ_ENABLE_DUMP,
 307 };
 308
 309 #ifdef CONFIG_TRACING
 310 #include <linux/ftrace.h>
 311
 312 static void sysrq_ftrace_dump(int key)
 313 {
 314         ftrace_dump(DUMP_ALL);
 315 }
 316 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 317         .handler        = sysrq_ftrace_dump,
 318         .help_msg       = "dump-ftrace-buffer(z)",
 319         .action_msg     = "Dump ftrace buffer",
 320         .enable_mask    = SYSRQ_ENABLE_DUMP,
 321 };
 322 #else
 323 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
 324 #endif
 325
 326 static void sysrq_handle_showmem(int key)
 327 {
 328         show_mem(0, NULL);
 329 }
 330 static struct sysrq_key_op sysrq_showmem_op = {
 331         .handler        = sysrq_handle_showmem,
 332         .help_msg       = "show-memory-usage(m)",
 333         .action_msg     = "Show Memory",
 334         .enable_mask    = SYSRQ_ENABLE_DUMP,
 335 };
 336
 337 /*
 338  * Signal sysrq helper function.  Sends a signal to all user processes.
 339  */
 340 static void send_sig_all(int sig)
 341 {
 342         struct task_struct *p;
 343
 344         read_lock(&tasklist_lock);
 345         for_each_process(p) {
 346                 if (p->flags & PF_KTHREAD)
 347                         continue;
 348                 if (is_global_init(p))
 349                         continue;
 350
 351                 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
 352         }
 353         read_unlock(&tasklist_lock);
 354 }
 355
 356 static void sysrq_handle_term(int key)
 357 {
 358         send_sig_all(SIGTERM);
 359         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 360 }
 361 static struct sysrq_key_op sysrq_term_op = {
 362         .handler        = sysrq_handle_term,
 363         .help_msg       = "terminate-all-tasks(e)",
 364         .action_msg     = "Terminate All Tasks",
 365         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 366 };
 367
 368 static void moom_callback(struct work_struct *ignored)
 369 {
 370         const gfp_t gfp_mask = GFP_KERNEL;
 371         struct oom_control oc = {
 372                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 373                 .nodemask = NULL,
 374                 .memcg = NULL,
 375                 .gfp_mask = gfp_mask,
 376                 .order = -1,
 377         };
 378
 379         mutex_lock(&oom_lock);
 380         if (!out_of_memory(&oc))
 381                 pr_info("OOM request ignored. No task eligible\n");
 382         mutex_unlock(&oom_lock);
 383 }
 384
 385 static DECLARE_WORK(moom_work, moom_callback);
 386
 387 static void sysrq_handle_moom(int key)
 388 {
 389         schedule_work(&moom_work);
 390 }
 391 static struct sysrq_key_op sysrq_moom_op = {
 392         .handler        = sysrq_handle_moom,
 393         .help_msg       = "memory-full-oom-kill(f)",
 394         .action_msg     = "Manual OOM execution",
 395         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 396 };
 397
 398 #ifdef CONFIG_BLOCK
 399 static void sysrq_handle_thaw(int key)
 400 {
 401         emergency_thaw_all();
 402 }
 403 static struct sysrq_key_op sysrq_thaw_op = {
 404         .handler        = sysrq_handle_thaw,
 405         .help_msg       = "thaw-filesystems(j)",
 406         .action_msg     = "Emergency Thaw of all frozen filesystems",
 407         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 408 };
 409 #endif
 410
 411 static void sysrq_handle_kill(int key)
 412 {
 413         send_sig_all(SIGKILL);
 414         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 415 }
 416 static struct sysrq_key_op sysrq_kill_op = {
 417         .handler        = sysrq_handle_kill,
 418         .help_msg       = "kill-all-tasks(i)",
 419         .action_msg     = "Kill All Tasks",
 420         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 421 };
 422
 423 static void sysrq_handle_unrt(int key)
 424 {
 425         normalize_rt_tasks();
 426 }
 427 static struct sysrq_key_op sysrq_unrt_op = {
 428         .handler        = sysrq_handle_unrt,
 429         .help_msg       = "nice-all-RT-tasks(n)",
 430         .action_msg     = "Nice All RT Tasks",
 431         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 432 };
 433
 434 /* Key Operations table and lock */
 435 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 436
 437 static struct sysrq_key_op *sysrq_key_table[36] = {
 438         &sysrq_loglevel_op,             /* 0 */
 439         &sysrq_loglevel_op,             /* 1 */
 440         &sysrq_loglevel_op,             /* 2 */
 441         &sysrq_loglevel_op,             /* 3 */
 442         &sysrq_loglevel_op,             /* 4 */
 443         &sysrq_loglevel_op,             /* 5 */
 444         &sysrq_loglevel_op,             /* 6 */
 445         &sysrq_loglevel_op,             /* 7 */
 446         &sysrq_loglevel_op,             /* 8 */
 447         &sysrq_loglevel_op,             /* 9 */
 448
 449         /*
 450          * a: Don't use for system provided sysrqs, it is handled specially on
 451          * sparc and will never arrive.
 452          */
 453         NULL,                           /* a */
 454         &sysrq_reboot_op,               /* b */
 455         &sysrq_crash_op,                /* c */
 456         &sysrq_showlocks_op,            /* d */
 457         &sysrq_term_op,                 /* e */
 458         &sysrq_moom_op,                 /* f */
 459         /* g: May be registered for the kernel debugger */
 460         NULL,                           /* g */
 461         NULL,                           /* h - reserved for help */
 462         &sysrq_kill_op,                 /* i */
 463 #ifdef CONFIG_BLOCK
 464         &sysrq_thaw_op,                 /* j */
 465 #else
 466         NULL,                           /* j */
 467 #endif
 468         &sysrq_SAK_op,                  /* k */
 469 #ifdef CONFIG_SMP
 470         &sysrq_showallcpus_op,          /* l */
 471 #else
 472         NULL,                           /* l */
 473 #endif
 474         &sysrq_showmem_op,              /* m */
 475         &sysrq_unrt_op,                 /* n */
 476         /* o: This will often be registered as 'Off' at init time */
 477         NULL,                           /* o */
 478         &sysrq_showregs_op,             /* p */
 479         &sysrq_show_timers_op,          /* q */
 480         &sysrq_unraw_op,                /* r */
 481         &sysrq_sync_op,                 /* s */
 482         &sysrq_showstate_op,            /* t */
 483         &sysrq_mountro_op,              /* u */
 484         /* v: May be registered for frame buffer console restore */
 485         NULL,                           /* v */
 486         &sysrq_showstate_blocked_op,    /* w */
 487         /* x: May be registered on mips for TLB dump */
 488         /* x: May be registered on ppc/powerpc for xmon */
 489         /* x: May be registered on sparc64 for global PMU dump */
 490         /* x: May be registered on x86_64 for disabling secure boot */
 491         NULL,                           /* x */
 492         /* y: May be registered on sparc64 for global register dump */
 493         NULL,                           /* y */
 494         &sysrq_ftrace_dump_op,          /* z */
 495 };
 496
 497 /* key2index calculation, -1 on invalid index */
 498 static int sysrq_key_table_key2index(int key)
 499 {
 500         int retval;
 501
 502         if ((key >= '0') && (key <= '9'))
 503                 retval = key - '0';
 504         else if ((key >= 'a') && (key <= 'z'))
 505                 retval = key + 10 - 'a';
 506         else
 507                 retval = -1;
 508         return retval;
 509 }
 510
 511 /*
 512  * get and put functions for the table, exposed to modules.
 513  */
 514 struct sysrq_key_op *__sysrq_get_key_op(int key)
 515 {
 516         struct sysrq_key_op *op_p = NULL;
 517         int i;
 518
 519         i = sysrq_key_table_key2index(key);
 520         if (i != -1)
 521                 op_p = sysrq_key_table[i];
 522
 523         return op_p;
 524 }
 525
 526 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 527 {
 528         int i = sysrq_key_table_key2index(key);
 529
 530         if (i != -1)
 531                 sysrq_key_table[i] = op_p;
 532 }
 533
 534 void __handle_sysrq(int key, unsigned int from)
 535 {
 536         struct sysrq_key_op *op_p;
 537         int orig_log_level;
 538         int i;
 539
 540         rcu_sysrq_start();
 541         rcu_read_lock();
 542         /*
 543          * Raise the apparent loglevel to maximum so that the sysrq header
 544          * is shown to provide the user with positive feedback.  We do not
 545          * simply emit this at KERN_EMERG as that would change message
 546          * routing in the consumers of /proc/kmsg.
 547          */
 548         orig_log_level = console_loglevel;
 549         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 550         pr_info("SysRq : ");
 551
 552         op_p = __sysrq_get_key_op(key);
 553         if (op_p) {
 554                 /* Ban synthetic events from some sysrq functionality */
 555                 if ((from == SYSRQ_FROM_PROC || from == SYSRQ_FROM_SYNTHETIC) &&
 556                     op_p->enable_mask & SYSRQ_DISABLE_USERSPACE)
 557                         printk("This sysrq operation is disabled from userspace.\n");
 558                 /*
 559                  * Should we check for enabled operations (/proc/sysrq-trigger
 560                  * should not) and is the invoked operation enabled?
 561                  */
 562                 if (from == SYSRQ_FROM_KERNEL || sysrq_on_mask(op_p->enable_mask)) {
 563                         pr_cont("%s\n", op_p->action_msg);
 564                         console_loglevel = orig_log_level;
 565                         op_p->handler(key);
 566                 } else {
 567                         pr_cont("This sysrq operation is disabled.\n");
 568                 }
 569         } else {
 570                 pr_cont("HELP : ");
 571                 /* Only print the help msg once per handler */
 572                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 573                         if (sysrq_key_table[i]) {
 574                                 int j;
 575
 576                                 for (j = 0; sysrq_key_table[i] !=
 577                                                 sysrq_key_table[j]; j++)
 578                                         ;
 579                                 if (j != i)
 580                                         continue;
 581                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 582                         }
 583                 }
 584                 pr_cont("\n");
 585                 console_loglevel = orig_log_level;
 586         }
 587         rcu_read_unlock();
 588         rcu_sysrq_end();
 589 }
 590
 591 void handle_sysrq(int key)
 592 {
 593         if (sysrq_on())
 594                 __handle_sysrq(key, SYSRQ_FROM_KERNEL);
 595 }
 596 EXPORT_SYMBOL(handle_sysrq);
 597
 598 #ifdef CONFIG_INPUT
 599 static int sysrq_reset_downtime_ms;
 600
 601 /* Simple translation table for the SysRq keys */
 602 static const unsigned char sysrq_xlate[KEY_CNT] =
 603         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 604         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 605         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 606         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 607         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 608         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 609         "\r\000/";                                      /* 0x60 - 0x6f */
 610
 611 struct sysrq_state {
 612         struct input_handle handle;
 613         struct work_struct reinject_work;
 614         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 615         unsigned int alt;
 616         unsigned int alt_use;
 617         bool active;
 618         bool need_reinject;
 619         bool reinjecting;
 620
 621         /* reset sequence handling */
 622         bool reset_canceled;
 623         bool reset_requested;
 624         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 625         int reset_seq_len;
 626         int reset_seq_cnt;
 627         int reset_seq_version;
 628         struct timer_list keyreset_timer;
 629 };
 630
 631 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 632 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 633 static unsigned int sysrq_reset_seq_len;
 634 static unsigned int sysrq_reset_seq_version = 1;
 635
 636 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 637 {
 638         int i;
 639         unsigned short key;
 640
 641         state->reset_seq_cnt = 0;
 642
 643         for (i = 0; i < sysrq_reset_seq_len; i++) {
 644                 key = sysrq_reset_seq[i];
 645
 646                 if (key == KEY_RESERVED || key > KEY_MAX)
 647                         break;
 648
 649                 __set_bit(key, state->reset_keybit);
 650                 state->reset_seq_len++;
 651
 652                 if (test_bit(key, state->key_down))
 653                         state->reset_seq_cnt++;
 654         }
 655
 656         /* Disable reset until old keys are not released */
 657         state->reset_canceled = state->reset_seq_cnt != 0;
 658
 659         state->reset_seq_version = sysrq_reset_seq_version;
 660 }
 661
 662 static void sysrq_do_reset(struct timer_list *t)
 663 {
 664         struct sysrq_state *state = from_timer(state, t, keyreset_timer);
 665
 666         state->reset_requested = true;
 667
 668         sys_sync();
 669         kernel_restart(NULL);
 670 }
 671
 672 static void sysrq_handle_reset_request(struct sysrq_state *state)
 673 {
 674         if (state->reset_requested)
 675                 __handle_sysrq(sysrq_xlate[KEY_B], SYSRQ_FROM_KERNEL);
 676
 677         if (sysrq_reset_downtime_ms)
 678                 mod_timer(&state->keyreset_timer,
 679                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 680         else
 681                 sysrq_do_reset(&state->keyreset_timer);
 682 }
 683
 684 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 685                                         unsigned int code, int value)
 686 {
 687         if (!test_bit(code, state->reset_keybit)) {
 688                 /*
 689                  * Pressing any key _not_ in reset sequence cancels
 690                  * the reset sequence.  Also cancelling the timer in
 691                  * case additional keys were pressed after a reset
 692                  * has been requested.
 693                  */
 694                 if (value && state->reset_seq_cnt) {
 695                         state->reset_canceled = true;
 696                         del_timer(&state->keyreset_timer);
 697                 }
 698         } else if (value == 0) {
 699                 /*
 700                  * Key release - all keys in the reset sequence need
 701                  * to be pressed and held for the reset timeout
 702                  * to hold.
 703                  */
 704                 del_timer(&state->keyreset_timer);
 705
 706                 if (--state->reset_seq_cnt == 0)
 707                         state->reset_canceled = false;
 708         } else if (value == 1) {
 709                 /* key press, not autorepeat */
 710                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 711                     !state->reset_canceled) {
 712                         sysrq_handle_reset_request(state);
 713                 }
 714         }
 715 }
 716
 717 #ifdef CONFIG_OF
 718 static void sysrq_of_get_keyreset_config(void)
 719 {
 720         u32 key;
 721         struct device_node *np;
 722         struct property *prop;
 723         const __be32 *p;
 724
 725         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 726         if (!np) {
 727                 pr_debug("No sysrq node found");
 728                 return;
 729         }
 730
 731         /* Reset in case a __weak definition was present */
 732         sysrq_reset_seq_len = 0;
 733
 734         of_property_for_each_u32(np, "keyset", prop, p, key) {
 735                 if (key == KEY_RESERVED || key > KEY_MAX ||
 736                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 737                         break;
 738
 739                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 740         }
 741
 742         /* Get reset timeout if any. */
 743         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 744 }
 745 #else
 746 static void sysrq_of_get_keyreset_config(void)
 747 {
 748 }
 749 #endif
 750
 751 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 752 {
 753         struct sysrq_state *sysrq =
 754                         container_of(work, struct sysrq_state, reinject_work);
 755         struct input_handle *handle = &sysrq->handle;
 756         unsigned int alt_code = sysrq->alt_use;
 757
 758         if (sysrq->need_reinject) {
 759                 /* we do not want the assignment to be reordered */
 760                 sysrq->reinjecting = true;
 761                 mb();
 762
 763                 /* Simulate press and release of Alt + SysRq */
 764                 input_inject_event(handle, EV_KEY, alt_code, 1);
 765                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 766                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 767
 768                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 769                 input_inject_event(handle, EV_KEY, alt_code, 0);
 770                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 771
 772                 mb();
 773                 sysrq->reinjecting = false;
 774         }
 775 }
 776
 777 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 778                                   unsigned int code, int value)
 779 {
 780         bool was_active = sysrq->active;
 781         bool suppress;
 782
 783         switch (code) {
 784
 785         case KEY_LEFTALT:
 786         case KEY_RIGHTALT:
 787                 if (!value) {
 788                         /* One of ALTs is being released */
 789                         if (sysrq->active && code == sysrq->alt_use)
 790                                 sysrq->active = false;
 791
 792                         sysrq->alt = KEY_RESERVED;
 793
 794                 } else if (value != 2) {
 795                         sysrq->alt = code;
 796                         sysrq->need_reinject = false;
 797                 }
 798                 break;
 799
 800         case KEY_SYSRQ:
 801                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 802                         sysrq->active = true;
 803                         sysrq->alt_use = sysrq->alt;
 804                         /*
 805                          * If nothing else will be pressed we'll need
 806                          * to re-inject Alt-SysRq keysroke.
 807                          */
 808                         sysrq->need_reinject = true;
 809                 }
 810
 811                 /*
 812                  * Pretend that sysrq was never pressed at all. This
 813                  * is needed to properly handle KGDB which will try
 814                  * to release all keys after exiting debugger. If we
 815                  * do not clear key bit it KGDB will end up sending
 816                  * release events for Alt and SysRq, potentially
 817                  * triggering print screen function.
 818                  */
 819                 if (sysrq->active)
 820                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 821
 822                 break;
 823
 824         default:
 825                 if (sysrq->active && value && value != 2) {
 826                         int from = sysrq->handle.dev->flags & INPUTDEV_FLAGS_SYNTHETIC ?
 827                                         SYSRQ_FROM_SYNTHETIC : 0;
 828                         sysrq->need_reinject = false;
 829                         __handle_sysrq(sysrq_xlate[code], from);
 830                 }
 831                 break;
 832         }
 833
 834         suppress = sysrq->active;
 835
 836         if (!sysrq->active) {
 837
 838                 /*
 839                  * See if reset sequence has changed since the last time.
 840                  */
 841                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 842                         sysrq_parse_reset_sequence(sysrq);
 843
 844                 /*
 845                  * If we are not suppressing key presses keep track of
 846                  * keyboard state so we can release keys that have been
 847                  * pressed before entering SysRq mode.
 848                  */
 849                 if (value)
 850                         set_bit(code, sysrq->key_down);
 851                 else
 852                         clear_bit(code, sysrq->key_down);
 853
 854                 if (was_active)
 855                         schedule_work(&sysrq->reinject_work);
 856
 857                 /* Check for reset sequence */
 858                 sysrq_detect_reset_sequence(sysrq, code, value);
 859
 860         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 861                 /*
 862                  * Pass on release events for keys that was pressed before
 863                  * entering SysRq mode.
 864                  */
 865                 suppress = false;
 866         }
 867
 868         return suppress;
 869 }
 870
 871 static bool sysrq_filter(struct input_handle *handle,
 872                          unsigned int type, unsigned int code, int value)
 873 {
 874         struct sysrq_state *sysrq = handle->private;
 875         bool suppress;
 876
 877         /*
 878          * Do not filter anything if we are in the process of re-injecting
 879          * Alt+SysRq combination.
 880          */
 881         if (sysrq->reinjecting)
 882                 return false;
 883
 884         switch (type) {
 885
 886         case EV_SYN:
 887                 suppress = false;
 888                 break;
 889
 890         case EV_KEY:
 891                 suppress = sysrq_handle_keypress(sysrq, code, value);
 892                 break;
 893
 894         default:
 895                 suppress = sysrq->active;
 896                 break;
 897         }
 898
 899         return suppress;
 900 }
 901
 902 static int sysrq_connect(struct input_handler *handler,
 903                          struct input_dev *dev,
 904                          const struct input_device_id *id)
 905 {
 906         struct sysrq_state *sysrq;
 907         int error;
 908
 909         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 910         if (!sysrq)
 911                 return -ENOMEM;
 912
 913         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 914
 915         sysrq->handle.dev = dev;
 916         sysrq->handle.handler = handler;
 917         sysrq->handle.name = "sysrq";
 918         sysrq->handle.private = sysrq;
 919         timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 920
 921         error = input_register_handle(&sysrq->handle);
 922         if (error) {
 923                 pr_err("Failed to register input sysrq handler, error %d\n",
 924                         error);
 925                 goto err_free;
 926         }
 927
 928         error = input_open_device(&sysrq->handle);
 929         if (error) {
 930                 pr_err("Failed to open input device, error %d\n", error);
 931                 goto err_unregister;
 932         }
 933
 934         return 0;
 935
 936  err_unregister:
 937         input_unregister_handle(&sysrq->handle);
 938  err_free:
 939         kfree(sysrq);
 940         return error;
 941 }
 942
 943 static void sysrq_disconnect(struct input_handle *handle)
 944 {
 945         struct sysrq_state *sysrq = handle->private;
 946
 947         input_close_device(handle);
 948         cancel_work_sync(&sysrq->reinject_work);
 949         del_timer_sync(&sysrq->keyreset_timer);
 950         input_unregister_handle(handle);
 951         kfree(sysrq);
 952 }
 953
 954 /*
 955  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 956  * keyboards have SysRq key predefined and so user may add it to keymap
 957  * later, but we expect all such keyboards to have left alt.
 958  */
 959 static const struct input_device_id sysrq_ids[] = {
 960         {
 961                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 962                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 963                 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
 964                 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
 965         },
 966         { },
 967 };
 968
 969 static struct input_handler sysrq_handler = {
 970         .filter         = sysrq_filter,
 971         .connect        = sysrq_connect,
 972         .disconnect     = sysrq_disconnect,
 973         .name           = "sysrq",
 974         .id_table       = sysrq_ids,
 975 };
 976
 977 static bool sysrq_handler_registered;
 978
 979 static inline void sysrq_register_handler(void)
 980 {
 981         int error;
 982
 983         sysrq_of_get_keyreset_config();
 984
 985         error = input_register_handler(&sysrq_handler);
 986         if (error)
 987                 pr_err("Failed to register input handler, error %d", error);
 988         else
 989                 sysrq_handler_registered = true;
 990 }
 991
 992 static inline void sysrq_unregister_handler(void)
 993 {
 994         if (sysrq_handler_registered) {
 995                 input_unregister_handler(&sysrq_handler);
 996                 sysrq_handler_registered = false;
 997         }
 998 }
 999
1000 static int sysrq_reset_seq_param_set(const char *buffer,
1001                                      const struct kernel_param *kp)
1002 {
1003         unsigned long val;
1004         int error;
1005
1006         error = kstrtoul(buffer, 0, &val);
1007         if (error < 0)
1008                 return error;
1009
1010         if (val > KEY_MAX)
1011                 return -EINVAL;
1012
1013         *((unsigned short *)kp->arg) = val;
1014         sysrq_reset_seq_version++;
1015
1016         return 0;
1017 }
1018
1019 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1020         .get    = param_get_ushort,
1021         .set    = sysrq_reset_seq_param_set,
1022 };
1023
1024 #define param_check_sysrq_reset_seq(name, p)    \
1025         __param_check(name, p, unsigned short)
1026
1027 /*
1028  * not really modular, but the easiest way to keep compat with existing
1029  * bootargs behaviour is to continue using module_param here.
1030  */
1031 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1032                          &sysrq_reset_seq_len, 0644);
1033
1034 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1035
1036 #else
1037
1038 static inline void sysrq_register_handler(void)
1039 {
1040 }
1041
1042 static inline void sysrq_unregister_handler(void)
1043 {
1044 }
1045
1046 #endif /* CONFIG_INPUT */
1047
1048 int sysrq_toggle_support(int enable_mask)
1049 {
1050         bool was_enabled = sysrq_on();
1051
1052         sysrq_enabled = enable_mask;
1053
1054         if (was_enabled != sysrq_on()) {
1055                 if (sysrq_on())
1056                         sysrq_register_handler();
1057                 else
1058                         sysrq_unregister_handler();
1059         }
1060
1061         return 0;
1062 }
1063
1064 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1065                                 struct sysrq_key_op *remove_op_p)
1066 {
1067         int retval;
1068
1069         spin_lock(&sysrq_key_table_lock);
1070         if (__sysrq_get_key_op(key) == remove_op_p) {
1071                 __sysrq_put_key_op(key, insert_op_p);
1072                 retval = 0;
1073         } else {
1074                 retval = -1;
1075         }
1076         spin_unlock(&sysrq_key_table_lock);
1077
1078         /*
1079          * A concurrent __handle_sysrq either got the old op or the new op.
1080          * Wait for it to go away before returning, so the code for an old
1081          * op is not freed (eg. on module unload) while it is in use.
1082          */
1083         synchronize_rcu();
1084
1085         return retval;
1086 }
1087
1088 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1089 {
1090         return __sysrq_swap_key_ops(key, op_p, NULL);
1091 }
1092 EXPORT_SYMBOL(register_sysrq_key);
1093
1094 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1095 {
1096         return __sysrq_swap_key_ops(key, NULL, op_p);
1097 }
1098 EXPORT_SYMBOL(unregister_sysrq_key);
1099
1100 #ifdef CONFIG_PROC_FS
1101 /*
1102  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1103  */
1104 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1105                                    size_t count, loff_t *ppos)
1106 {
1107         if (count) {
1108                 char c;
1109
1110                 if (get_user(c, buf))
1111                         return -EFAULT;
1112                 __handle_sysrq(c, SYSRQ_FROM_PROC);
1113         }
1114
1115         return count;
1116 }
1117
1118 static const struct file_operations proc_sysrq_trigger_operations = {
1119         .write          = write_sysrq_trigger,
1120         .llseek         = noop_llseek,
1121 };
1122
1123 static void sysrq_init_procfs(void)
1124 {
1125         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1126                          &proc_sysrq_trigger_operations))
1127                 pr_err("Failed to register proc interface\n");
1128 }
1129
1130 #else
1131
1132 static inline void sysrq_init_procfs(void)
1133 {
1134 }
1135
1136 #endif /* CONFIG_PROC_FS */
1137
1138 static int __init sysrq_init(void)
1139 {
1140         sysrq_init_procfs();
1141
1142         if (sysrq_on())
1143                 sysrq_register_handler();
1144
1145         return 0;
1146 }
1147 device_initcall(sysrq_init);