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