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 = get_irq_regs();
 250
 251                 if (regs) {
 252                         pr_info("CPU%d:\n", smp_processor_id());
 253                         show_regs(regs);
 254                 }
 255                 schedule_work(&sysrq_showallcpus);
 256         }
 257 }
 258
 259 static struct sysrq_key_op sysrq_showallcpus_op = {
 260         .handler        = sysrq_handle_showallcpus,
 261         .help_msg       = "show-backtrace-all-active-cpus(l)",
 262         .action_msg     = "Show backtrace of all active CPUs",
 263         .enable_mask    = SYSRQ_ENABLE_DUMP,
 264 };
 265 #endif
 266
 267 static void sysrq_handle_showregs(int key)
 268 {
 269         struct pt_regs *regs = get_irq_regs();
 270         if (regs)
 271                 show_regs(regs);
 272         perf_event_print_debug();
 273 }
 274 static struct sysrq_key_op sysrq_showregs_op = {
 275         .handler        = sysrq_handle_showregs,
 276         .help_msg       = "show-registers(p)",
 277         .action_msg     = "Show Regs",
 278         .enable_mask    = SYSRQ_ENABLE_DUMP,
 279 };
 280
 281 static void sysrq_handle_showstate(int key)
 282 {
 283         show_state();
 284         show_workqueue_state();
 285 }
 286 static struct sysrq_key_op sysrq_showstate_op = {
 287         .handler        = sysrq_handle_showstate,
 288         .help_msg       = "show-task-states(t)",
 289         .action_msg     = "Show State",
 290         .enable_mask    = SYSRQ_ENABLE_DUMP,
 291 };
 292
 293 static void sysrq_handle_showstate_blocked(int key)
 294 {
 295         show_state_filter(TASK_UNINTERRUPTIBLE);
 296 }
 297 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 298         .handler        = sysrq_handle_showstate_blocked,
 299         .help_msg       = "show-blocked-tasks(w)",
 300         .action_msg     = "Show Blocked State",
 301         .enable_mask    = SYSRQ_ENABLE_DUMP,
 302 };
 303
 304 #ifdef CONFIG_TRACING
 305 #include <linux/ftrace.h>
 306
 307 static void sysrq_ftrace_dump(int key)
 308 {
 309         ftrace_dump(DUMP_ALL);
 310 }
 311 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 312         .handler        = sysrq_ftrace_dump,
 313         .help_msg       = "dump-ftrace-buffer(z)",
 314         .action_msg     = "Dump ftrace buffer",
 315         .enable_mask    = SYSRQ_ENABLE_DUMP,
 316 };
 317 #else
 318 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
 319 #endif
 320
 321 static void sysrq_handle_showmem(int key)
 322 {
 323         show_mem(0, NULL);
 324 }
 325 static struct sysrq_key_op sysrq_showmem_op = {
 326         .handler        = sysrq_handle_showmem,
 327         .help_msg       = "show-memory-usage(m)",
 328         .action_msg     = "Show Memory",
 329         .enable_mask    = SYSRQ_ENABLE_DUMP,
 330 };
 331
 332 /*
 333  * Signal sysrq helper function.  Sends a signal to all user processes.
 334  */
 335 static void send_sig_all(int sig)
 336 {
 337         struct task_struct *p;
 338
 339         read_lock(&tasklist_lock);
 340         for_each_process(p) {
 341                 if (p->flags & PF_KTHREAD)
 342                         continue;
 343                 if (is_global_init(p))
 344                         continue;
 345
 346                 do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
 347         }
 348         read_unlock(&tasklist_lock);
 349 }
 350
 351 static void sysrq_handle_term(int key)
 352 {
 353         send_sig_all(SIGTERM);
 354         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 355 }
 356 static struct sysrq_key_op sysrq_term_op = {
 357         .handler        = sysrq_handle_term,
 358         .help_msg       = "terminate-all-tasks(e)",
 359         .action_msg     = "Terminate All Tasks",
 360         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 361 };
 362
 363 static void moom_callback(struct work_struct *ignored)
 364 {
 365         const gfp_t gfp_mask = GFP_KERNEL;
 366         struct oom_control oc = {
 367                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 368                 .nodemask = NULL,
 369                 .memcg = NULL,
 370                 .gfp_mask = gfp_mask,
 371                 .order = -1,
 372         };
 373
 374         mutex_lock(&oom_lock);
 375         if (!out_of_memory(&oc))
 376                 pr_info("OOM request ignored. No task eligible\n");
 377         mutex_unlock(&oom_lock);
 378 }
 379
 380 static DECLARE_WORK(moom_work, moom_callback);
 381
 382 static void sysrq_handle_moom(int key)
 383 {
 384         schedule_work(&moom_work);
 385 }
 386 static struct sysrq_key_op sysrq_moom_op = {
 387         .handler        = sysrq_handle_moom,
 388         .help_msg       = "memory-full-oom-kill(f)",
 389         .action_msg     = "Manual OOM execution",
 390         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 391 };
 392
 393 #ifdef CONFIG_BLOCK
 394 static void sysrq_handle_thaw(int key)
 395 {
 396         emergency_thaw_all();
 397 }
 398 static struct sysrq_key_op sysrq_thaw_op = {
 399         .handler        = sysrq_handle_thaw,
 400         .help_msg       = "thaw-filesystems(j)",
 401         .action_msg     = "Emergency Thaw of all frozen filesystems",
 402         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 403 };
 404 #endif
 405
 406 static void sysrq_handle_kill(int key)
 407 {
 408         send_sig_all(SIGKILL);
 409         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 410 }
 411 static struct sysrq_key_op sysrq_kill_op = {
 412         .handler        = sysrq_handle_kill,
 413         .help_msg       = "kill-all-tasks(i)",
 414         .action_msg     = "Kill All Tasks",
 415         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 416 };
 417
 418 static void sysrq_handle_unrt(int key)
 419 {
 420         normalize_rt_tasks();
 421 }
 422 static struct sysrq_key_op sysrq_unrt_op = {
 423         .handler        = sysrq_handle_unrt,
 424         .help_msg       = "nice-all-RT-tasks(n)",
 425         .action_msg     = "Nice All RT Tasks",
 426         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 427 };
 428
 429 /* Key Operations table and lock */
 430 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 431
 432 static struct sysrq_key_op *sysrq_key_table[36] = {
 433         &sysrq_loglevel_op,             /* 0 */
 434         &sysrq_loglevel_op,             /* 1 */
 435         &sysrq_loglevel_op,             /* 2 */
 436         &sysrq_loglevel_op,             /* 3 */
 437         &sysrq_loglevel_op,             /* 4 */
 438         &sysrq_loglevel_op,             /* 5 */
 439         &sysrq_loglevel_op,             /* 6 */
 440         &sysrq_loglevel_op,             /* 7 */
 441         &sysrq_loglevel_op,             /* 8 */
 442         &sysrq_loglevel_op,             /* 9 */
 443
 444         /*
 445          * a: Don't use for system provided sysrqs, it is handled specially on
 446          * sparc and will never arrive.
 447          */
 448         NULL,                           /* a */
 449         &sysrq_reboot_op,               /* b */
 450         &sysrq_crash_op,                /* c */
 451         &sysrq_showlocks_op,            /* d */
 452         &sysrq_term_op,                 /* e */
 453         &sysrq_moom_op,                 /* f */
 454         /* g: May be registered for the kernel debugger */
 455         NULL,                           /* g */
 456         NULL,                           /* h - reserved for help */
 457         &sysrq_kill_op,                 /* i */
 458 #ifdef CONFIG_BLOCK
 459         &sysrq_thaw_op,                 /* j */
 460 #else
 461         NULL,                           /* j */
 462 #endif
 463         &sysrq_SAK_op,                  /* k */
 464 #ifdef CONFIG_SMP
 465         &sysrq_showallcpus_op,          /* l */
 466 #else
 467         NULL,                           /* l */
 468 #endif
 469         &sysrq_showmem_op,              /* m */
 470         &sysrq_unrt_op,                 /* n */
 471         /* o: This will often be registered as 'Off' at init time */
 472         NULL,                           /* o */
 473         &sysrq_showregs_op,             /* p */
 474         &sysrq_show_timers_op,          /* q */
 475         &sysrq_unraw_op,                /* r */
 476         &sysrq_sync_op,                 /* s */
 477         &sysrq_showstate_op,            /* t */
 478         &sysrq_mountro_op,              /* u */
 479         /* v: May be registered for frame buffer console restore */
 480         NULL,                           /* v */
 481         &sysrq_showstate_blocked_op,    /* w */
 482         /* x: May be registered on mips for TLB dump */
 483         /* x: May be registered on ppc/powerpc for xmon */
 484         /* x: May be registered on sparc64 for global PMU dump */
 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, bool check_mask)
 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                 /*
 549                  * Should we check for enabled operations (/proc/sysrq-trigger
 550                  * should not) and is the invoked operation enabled?
 551                  */
 552                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 553                         pr_cont("%s\n", op_p->action_msg);
 554                         console_loglevel = orig_log_level;
 555                         op_p->handler(key);
 556                 } else {
 557                         pr_cont("This sysrq operation is disabled.\n");
 558                 }
 559         } else {
 560                 pr_cont("HELP : ");
 561                 /* Only print the help msg once per handler */
 562                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 563                         if (sysrq_key_table[i]) {
 564                                 int j;
 565
 566                                 for (j = 0; sysrq_key_table[i] !=
 567                                                 sysrq_key_table[j]; j++)
 568                                         ;
 569                                 if (j != i)
 570                                         continue;
 571                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 572                         }
 573                 }
 574                 pr_cont("\n");
 575                 console_loglevel = orig_log_level;
 576         }
 577         rcu_read_unlock();
 578         rcu_sysrq_end();
 579 }
 580
 581 void handle_sysrq(int key)
 582 {
 583         if (sysrq_on())
 584                 __handle_sysrq(key, true);
 585 }
 586 EXPORT_SYMBOL(handle_sysrq);
 587
 588 #ifdef CONFIG_INPUT
 589 static int sysrq_reset_downtime_ms;
 590
 591 /* Simple translation table for the SysRq keys */
 592 static const unsigned char sysrq_xlate[KEY_CNT] =
 593         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 594         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 595         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 596         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 597         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 598         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 599         "\r\000/";                                      /* 0x60 - 0x6f */
 600
 601 struct sysrq_state {
 602         struct input_handle handle;
 603         struct work_struct reinject_work;
 604         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 605         unsigned int alt;
 606         unsigned int alt_use;
 607         bool active;
 608         bool need_reinject;
 609         bool reinjecting;
 610
 611         /* reset sequence handling */
 612         bool reset_canceled;
 613         bool reset_requested;
 614         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 615         int reset_seq_len;
 616         int reset_seq_cnt;
 617         int reset_seq_version;
 618         struct timer_list keyreset_timer;
 619 };
 620
 621 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 622 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 623 static unsigned int sysrq_reset_seq_len;
 624 static unsigned int sysrq_reset_seq_version = 1;
 625
 626 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 627 {
 628         int i;
 629         unsigned short key;
 630
 631         state->reset_seq_cnt = 0;
 632
 633         for (i = 0; i < sysrq_reset_seq_len; i++) {
 634                 key = sysrq_reset_seq[i];
 635
 636                 if (key == KEY_RESERVED || key > KEY_MAX)
 637                         break;
 638
 639                 __set_bit(key, state->reset_keybit);
 640                 state->reset_seq_len++;
 641
 642                 if (test_bit(key, state->key_down))
 643                         state->reset_seq_cnt++;
 644         }
 645
 646         /* Disable reset until old keys are not released */
 647         state->reset_canceled = state->reset_seq_cnt != 0;
 648
 649         state->reset_seq_version = sysrq_reset_seq_version;
 650 }
 651
 652 static void sysrq_do_reset(unsigned long _state)
 653 {
 654         struct sysrq_state *state = (struct sysrq_state *) _state;
 655
 656         state->reset_requested = true;
 657
 658         sys_sync();
 659         kernel_restart(NULL);
 660 }
 661
 662 static void sysrq_handle_reset_request(struct sysrq_state *state)
 663 {
 664         if (state->reset_requested)
 665                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 666
 667         if (sysrq_reset_downtime_ms)
 668                 mod_timer(&state->keyreset_timer,
 669                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 670         else
 671                 sysrq_do_reset((unsigned long)state);
 672 }
 673
 674 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 675                                         unsigned int code, int value)
 676 {
 677         if (!test_bit(code, state->reset_keybit)) {
 678                 /*
 679                  * Pressing any key _not_ in reset sequence cancels
 680                  * the reset sequence.  Also cancelling the timer in
 681                  * case additional keys were pressed after a reset
 682                  * has been requested.
 683                  */
 684                 if (value && state->reset_seq_cnt) {
 685                         state->reset_canceled = true;
 686                         del_timer(&state->keyreset_timer);
 687                 }
 688         } else if (value == 0) {
 689                 /*
 690                  * Key release - all keys in the reset sequence need
 691                  * to be pressed and held for the reset timeout
 692                  * to hold.
 693                  */
 694                 del_timer(&state->keyreset_timer);
 695
 696                 if (--state->reset_seq_cnt == 0)
 697                         state->reset_canceled = false;
 698         } else if (value == 1) {
 699                 /* key press, not autorepeat */
 700                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 701                     !state->reset_canceled) {
 702                         sysrq_handle_reset_request(state);
 703                 }
 704         }
 705 }
 706
 707 #ifdef CONFIG_OF
 708 static void sysrq_of_get_keyreset_config(void)
 709 {
 710         u32 key;
 711         struct device_node *np;
 712         struct property *prop;
 713         const __be32 *p;
 714
 715         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 716         if (!np) {
 717                 pr_debug("No sysrq node found");
 718                 return;
 719         }
 720
 721         /* Reset in case a __weak definition was present */
 722         sysrq_reset_seq_len = 0;
 723
 724         of_property_for_each_u32(np, "keyset", prop, p, key) {
 725                 if (key == KEY_RESERVED || key > KEY_MAX ||
 726                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 727                         break;
 728
 729                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 730         }
 731
 732         /* Get reset timeout if any. */
 733         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 734 }
 735 #else
 736 static void sysrq_of_get_keyreset_config(void)
 737 {
 738 }
 739 #endif
 740
 741 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 742 {
 743         struct sysrq_state *sysrq =
 744                         container_of(work, struct sysrq_state, reinject_work);
 745         struct input_handle *handle = &sysrq->handle;
 746         unsigned int alt_code = sysrq->alt_use;
 747
 748         if (sysrq->need_reinject) {
 749                 /* we do not want the assignment to be reordered */
 750                 sysrq->reinjecting = true;
 751                 mb();
 752
 753                 /* Simulate press and release of Alt + SysRq */
 754                 input_inject_event(handle, EV_KEY, alt_code, 1);
 755                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 756                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 757
 758                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 759                 input_inject_event(handle, EV_KEY, alt_code, 0);
 760                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 761
 762                 mb();
 763                 sysrq->reinjecting = false;
 764         }
 765 }
 766
 767 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 768                                   unsigned int code, int value)
 769 {
 770         bool was_active = sysrq->active;
 771         bool suppress;
 772
 773         switch (code) {
 774
 775         case KEY_LEFTALT:
 776         case KEY_RIGHTALT:
 777                 if (!value) {
 778                         /* One of ALTs is being released */
 779                         if (sysrq->active && code == sysrq->alt_use)
 780                                 sysrq->active = false;
 781
 782                         sysrq->alt = KEY_RESERVED;
 783
 784                 } else if (value != 2) {
 785                         sysrq->alt = code;
 786                         sysrq->need_reinject = false;
 787                 }
 788                 break;
 789
 790         case KEY_SYSRQ:
 791                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 792                         sysrq->active = true;
 793                         sysrq->alt_use = sysrq->alt;
 794                         /*
 795                          * If nothing else will be pressed we'll need
 796                          * to re-inject Alt-SysRq keysroke.
 797                          */
 798                         sysrq->need_reinject = true;
 799                 }
 800
 801                 /*
 802                  * Pretend that sysrq was never pressed at all. This
 803                  * is needed to properly handle KGDB which will try
 804                  * to release all keys after exiting debugger. If we
 805                  * do not clear key bit it KGDB will end up sending
 806                  * release events for Alt and SysRq, potentially
 807                  * triggering print screen function.
 808                  */
 809                 if (sysrq->active)
 810                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 811
 812                 break;
 813
 814         default:
 815                 if (sysrq->active && value && value != 2) {
 816                         sysrq->need_reinject = false;
 817                         __handle_sysrq(sysrq_xlate[code], true);
 818                 }
 819                 break;
 820         }
 821
 822         suppress = sysrq->active;
 823
 824         if (!sysrq->active) {
 825
 826                 /*
 827                  * See if reset sequence has changed since the last time.
 828                  */
 829                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 830                         sysrq_parse_reset_sequence(sysrq);
 831
 832                 /*
 833                  * If we are not suppressing key presses keep track of
 834                  * keyboard state so we can release keys that have been
 835                  * pressed before entering SysRq mode.
 836                  */
 837                 if (value)
 838                         set_bit(code, sysrq->key_down);
 839                 else
 840                         clear_bit(code, sysrq->key_down);
 841
 842                 if (was_active)
 843                         schedule_work(&sysrq->reinject_work);
 844
 845                 /* Check for reset sequence */
 846                 sysrq_detect_reset_sequence(sysrq, code, value);
 847
 848         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 849                 /*
 850                  * Pass on release events for keys that was pressed before
 851                  * entering SysRq mode.
 852                  */
 853                 suppress = false;
 854         }
 855
 856         return suppress;
 857 }
 858
 859 static bool sysrq_filter(struct input_handle *handle,
 860                          unsigned int type, unsigned int code, int value)
 861 {
 862         struct sysrq_state *sysrq = handle->private;
 863         bool suppress;
 864
 865         /*
 866          * Do not filter anything if we are in the process of re-injecting
 867          * Alt+SysRq combination.
 868          */
 869         if (sysrq->reinjecting)
 870                 return false;
 871
 872         switch (type) {
 873
 874         case EV_SYN:
 875                 suppress = false;
 876                 break;
 877
 878         case EV_KEY:
 879                 suppress = sysrq_handle_keypress(sysrq, code, value);
 880                 break;
 881
 882         default:
 883                 suppress = sysrq->active;
 884                 break;
 885         }
 886
 887         return suppress;
 888 }
 889
 890 static int sysrq_connect(struct input_handler *handler,
 891                          struct input_dev *dev,
 892                          const struct input_device_id *id)
 893 {
 894         struct sysrq_state *sysrq;
 895         int error;
 896
 897         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 898         if (!sysrq)
 899                 return -ENOMEM;
 900
 901         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 902
 903         sysrq->handle.dev = dev;
 904         sysrq->handle.handler = handler;
 905         sysrq->handle.name = "sysrq";
 906         sysrq->handle.private = sysrq;
 907         setup_timer(&sysrq->keyreset_timer,
 908                     sysrq_do_reset, (unsigned long)sysrq);
 909
 910         error = input_register_handle(&sysrq->handle);
 911         if (error) {
 912                 pr_err("Failed to register input sysrq handler, error %d\n",
 913                         error);
 914                 goto err_free;
 915         }
 916
 917         error = input_open_device(&sysrq->handle);
 918         if (error) {
 919                 pr_err("Failed to open input device, error %d\n", error);
 920                 goto err_unregister;
 921         }
 922
 923         return 0;
 924
 925  err_unregister:
 926         input_unregister_handle(&sysrq->handle);
 927  err_free:
 928         kfree(sysrq);
 929         return error;
 930 }
 931
 932 static void sysrq_disconnect(struct input_handle *handle)
 933 {
 934         struct sysrq_state *sysrq = handle->private;
 935
 936         input_close_device(handle);
 937         cancel_work_sync(&sysrq->reinject_work);
 938         del_timer_sync(&sysrq->keyreset_timer);
 939         input_unregister_handle(handle);
 940         kfree(sysrq);
 941 }
 942
 943 /*
 944  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 945  * keyboards have SysRq key predefined and so user may add it to keymap
 946  * later, but we expect all such keyboards to have left alt.
 947  */
 948 static const struct input_device_id sysrq_ids[] = {
 949         {
 950                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 951                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
 952                 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
 953                 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
 954         },
 955         { },
 956 };
 957
 958 static struct input_handler sysrq_handler = {
 959         .filter         = sysrq_filter,
 960         .connect        = sysrq_connect,
 961         .disconnect     = sysrq_disconnect,
 962         .name           = "sysrq",
 963         .id_table       = sysrq_ids,
 964 };
 965
 966 static bool sysrq_handler_registered;
 967
 968 static inline void sysrq_register_handler(void)
 969 {
 970         int error;
 971
 972         sysrq_of_get_keyreset_config();
 973
 974         error = input_register_handler(&sysrq_handler);
 975         if (error)
 976                 pr_err("Failed to register input handler, error %d", error);
 977         else
 978                 sysrq_handler_registered = true;
 979 }
 980
 981 static inline void sysrq_unregister_handler(void)
 982 {
 983         if (sysrq_handler_registered) {
 984                 input_unregister_handler(&sysrq_handler);
 985                 sysrq_handler_registered = false;
 986         }
 987 }
 988
 989 static int sysrq_reset_seq_param_set(const char *buffer,
 990                                      const struct kernel_param *kp)
 991 {
 992         unsigned long val;
 993         int error;
 994
 995         error = kstrtoul(buffer, 0, &val);
 996         if (error < 0)
 997                 return error;
 998
 999         if (val > KEY_MAX)
1000                 return -EINVAL;
1001
1002         *((unsigned short *)kp->arg) = val;
1003         sysrq_reset_seq_version++;
1004
1005         return 0;
1006 }
1007
1008 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1009         .get    = param_get_ushort,
1010         .set    = sysrq_reset_seq_param_set,
1011 };
1012
1013 #define param_check_sysrq_reset_seq(name, p)    \
1014         __param_check(name, p, unsigned short)
1015
1016 /*
1017  * not really modular, but the easiest way to keep compat with existing
1018  * bootargs behaviour is to continue using module_param here.
1019  */
1020 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1021                          &sysrq_reset_seq_len, 0644);
1022
1023 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1024
1025 #else
1026
1027 static inline void sysrq_register_handler(void)
1028 {
1029 }
1030
1031 static inline void sysrq_unregister_handler(void)
1032 {
1033 }
1034
1035 #endif /* CONFIG_INPUT */
1036
1037 int sysrq_toggle_support(int enable_mask)
1038 {
1039         bool was_enabled = sysrq_on();
1040
1041         sysrq_enabled = enable_mask;
1042
1043         if (was_enabled != sysrq_on()) {
1044                 if (sysrq_on())
1045                         sysrq_register_handler();
1046                 else
1047                         sysrq_unregister_handler();
1048         }
1049
1050         return 0;
1051 }
1052
1053 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1054                                 struct sysrq_key_op *remove_op_p)
1055 {
1056         int retval;
1057
1058         spin_lock(&sysrq_key_table_lock);
1059         if (__sysrq_get_key_op(key) == remove_op_p) {
1060                 __sysrq_put_key_op(key, insert_op_p);
1061                 retval = 0;
1062         } else {
1063                 retval = -1;
1064         }
1065         spin_unlock(&sysrq_key_table_lock);
1066
1067         /*
1068          * A concurrent __handle_sysrq either got the old op or the new op.
1069          * Wait for it to go away before returning, so the code for an old
1070          * op is not freed (eg. on module unload) while it is in use.
1071          */
1072         synchronize_rcu();
1073
1074         return retval;
1075 }
1076
1077 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1078 {
1079         return __sysrq_swap_key_ops(key, op_p, NULL);
1080 }
1081 EXPORT_SYMBOL(register_sysrq_key);
1082
1083 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1084 {
1085         return __sysrq_swap_key_ops(key, NULL, op_p);
1086 }
1087 EXPORT_SYMBOL(unregister_sysrq_key);
1088
1089 #ifdef CONFIG_PROC_FS
1090 /*
1091  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1092  */
1093 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1094                                    size_t count, loff_t *ppos)
1095 {
1096         if (count) {
1097                 char c;
1098
1099                 if (get_user(c, buf))
1100                         return -EFAULT;
1101                 __handle_sysrq(c, false);
1102         }
1103
1104         return count;
1105 }
1106
1107 static const struct file_operations proc_sysrq_trigger_operations = {
1108         .write          = write_sysrq_trigger,
1109         .llseek         = noop_llseek,
1110 };
1111
1112 static void sysrq_init_procfs(void)
1113 {
1114         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1115                          &proc_sysrq_trigger_operations))
1116                 pr_err("Failed to register proc interface\n");
1117 }
1118
1119 #else
1120
1121 static inline void sysrq_init_procfs(void)
1122 {
1123 }
1124
1125 #endif /* CONFIG_PROC_FS */
1126
1127 static int __init sysrq_init(void)
1128 {
1129         sysrq_init_procfs();
1130
1131         if (sysrq_on())
1132                 sysrq_register_handler();
1133
1134         return 0;
1135 }
1136 device_initcall(sysrq_init);