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/ctype.h>
  23 #include <linux/interrupt.h>
  24 #include <linux/mm.h>
  25 #include <linux/fs.h>
  26 #include <linux/mount.h>
  27 #include <linux/kdev_t.h>
  28 #include <linux/major.h>
  29 #include <linux/reboot.h>
  30 #include <linux/sysrq.h>
  31 #include <linux/kbd_kern.h>
  32 #include <linux/proc_fs.h>
  33 #include <linux/nmi.h>
  34 #include <linux/quotaops.h>
  35 #include <linux/perf_event.h>
  36 #include <linux/kernel.h>
  37 #include <linux/module.h>
  38 #include <linux/suspend.h>
  39 #include <linux/writeback.h>
  40 #include <linux/swap.h>
  41 #include <linux/spinlock.h>
  42 #include <linux/vt_kern.h>
  43 #include <linux/workqueue.h>
  44 #include <linux/hrtimer.h>
  45 #include <linux/oom.h>
  46 #include <linux/slab.h>
  47 #include <linux/input.h>
  48 #include <linux/uaccess.h>
  49 #include <linux/moduleparam.h>
  50 #include <linux/jiffies.h>
  51 #include <linux/syscalls.h>
  52 #include <linux/of.h>
  53 #include <linux/rcupdate.h>
  54
  55 #include <asm/ptrace.h>
  56 #include <asm/irq_regs.h>
  57
  58 /* Whether we react on sysrq keys or just ignore them */
  59 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
  60 static bool __read_mostly sysrq_always_enabled;
  61
  62 static bool sysrq_on(void)
  63 {
  64         return sysrq_enabled || sysrq_always_enabled;
  65 }
  66
  67 /**
  68  * sysrq_mask - Getter for sysrq_enabled mask.
  69  *
  70  * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
  71  */
  72 int sysrq_mask(void)
  73 {
  74         if (sysrq_always_enabled)
  75                 return 1;
  76         return sysrq_enabled;
  77 }
  78 EXPORT_SYMBOL_GPL(sysrq_mask);
  79
  80 /*
  81  * A value of 1 means 'all', other nonzero values are an op mask:
  82  */
  83 static bool sysrq_on_mask(int mask)
  84 {
  85         return sysrq_always_enabled ||
  86                sysrq_enabled == 1 ||
  87                (sysrq_enabled & mask);
  88 }
  89
  90 static int __init sysrq_always_enabled_setup(char *str)
  91 {
  92         sysrq_always_enabled = true;
  93         pr_info("sysrq always enabled.\n");
  94
  95         return 1;
  96 }
  97
  98 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  99
 100
 101 static void sysrq_handle_loglevel(int key)
 102 {
 103         int i;
 104
 105         i = key - '0';
 106         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 107         pr_info("Loglevel set to %d\n", i);
 108         console_loglevel = i;
 109 }
 110 static const struct sysrq_key_op sysrq_loglevel_op = {
 111         .handler        = sysrq_handle_loglevel,
 112         .help_msg       = "loglevel(0-9)",
 113         .action_msg     = "Changing Loglevel",
 114         .enable_mask    = SYSRQ_ENABLE_LOG,
 115 };
 116
 117 #ifdef CONFIG_VT
 118 static void sysrq_handle_SAK(int key)
 119 {
 120         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 121         schedule_work(SAK_work);
 122 }
 123 static const struct sysrq_key_op sysrq_SAK_op = {
 124         .handler        = sysrq_handle_SAK,
 125         .help_msg       = "sak(k)",
 126         .action_msg     = "SAK",
 127         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 128 };
 129 #else
 130 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
 131 #endif
 132
 133 #ifdef CONFIG_VT
 134 static void sysrq_handle_unraw(int key)
 135 {
 136         vt_reset_unicode(fg_console);
 137 }
 138
 139 static const struct sysrq_key_op sysrq_unraw_op = {
 140         .handler        = sysrq_handle_unraw,
 141         .help_msg       = "unraw(r)",
 142         .action_msg     = "Keyboard mode set to system default",
 143         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 144 };
 145 #else
 146 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
 147 #endif /* CONFIG_VT */
 148
 149 static void sysrq_handle_crash(int key)
 150 {
 151         /* release the RCU read lock before crashing */
 152         rcu_read_unlock();
 153
 154         panic("sysrq triggered crash\n");
 155 }
 156 static const struct sysrq_key_op sysrq_crash_op = {
 157         .handler        = sysrq_handle_crash,
 158         .help_msg       = "crash(c)",
 159         .action_msg     = "Trigger a crash",
 160         .enable_mask    = SYSRQ_ENABLE_DUMP,
 161 };
 162
 163 static void sysrq_handle_reboot(int key)
 164 {
 165         lockdep_off();
 166         local_irq_enable();
 167         emergency_restart();
 168 }
 169 static const struct sysrq_key_op sysrq_reboot_op = {
 170         .handler        = sysrq_handle_reboot,
 171         .help_msg       = "reboot(b)",
 172         .action_msg     = "Resetting",
 173         .enable_mask    = SYSRQ_ENABLE_BOOT,
 174 };
 175
 176 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
 177
 178 static void sysrq_handle_sync(int key)
 179 {
 180         emergency_sync();
 181 }
 182 static const struct sysrq_key_op sysrq_sync_op = {
 183         .handler        = sysrq_handle_sync,
 184         .help_msg       = "sync(s)",
 185         .action_msg     = "Emergency Sync",
 186         .enable_mask    = SYSRQ_ENABLE_SYNC,
 187 };
 188
 189 static void sysrq_handle_show_timers(int key)
 190 {
 191         sysrq_timer_list_show();
 192 }
 193
 194 static const struct sysrq_key_op sysrq_show_timers_op = {
 195         .handler        = sysrq_handle_show_timers,
 196         .help_msg       = "show-all-timers(q)",
 197         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 198 };
 199
 200 static void sysrq_handle_mountro(int key)
 201 {
 202         emergency_remount();
 203 }
 204 static const struct sysrq_key_op sysrq_mountro_op = {
 205         .handler        = sysrq_handle_mountro,
 206         .help_msg       = "unmount(u)",
 207         .action_msg     = "Emergency Remount R/O",
 208         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 209 };
 210
 211 #ifdef CONFIG_LOCKDEP
 212 static void sysrq_handle_showlocks(int key)
 213 {
 214         debug_show_all_locks();
 215 }
 216
 217 static const struct sysrq_key_op sysrq_showlocks_op = {
 218         .handler        = sysrq_handle_showlocks,
 219         .help_msg       = "show-all-locks(d)",
 220         .action_msg     = "Show Locks Held",
 221 };
 222 #else
 223 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
 224 #endif
 225
 226 #ifdef CONFIG_SMP
 227 static DEFINE_RAW_SPINLOCK(show_lock);
 228
 229 static void showacpu(void *dummy)
 230 {
 231         unsigned long flags;
 232
 233         /* Idle CPUs have no interesting backtrace. */
 234         if (idle_cpu(smp_processor_id()))
 235                 return;
 236
 237         raw_spin_lock_irqsave(&show_lock, flags);
 238         pr_info("CPU%d:\n", smp_processor_id());
 239         show_stack(NULL, NULL, KERN_INFO);
 240         raw_spin_unlock_irqrestore(&show_lock, flags);
 241 }
 242
 243 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 244 {
 245         smp_call_function(showacpu, NULL, 0);
 246 }
 247
 248 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 249
 250 static void sysrq_handle_showallcpus(int key)
 251 {
 252         /*
 253          * Fall back to the workqueue based printing if the
 254          * backtrace printing did not succeed or the
 255          * architecture has no support for it:
 256          */
 257         if (!trigger_all_cpu_backtrace()) {
 258                 struct pt_regs *regs = NULL;
 259
 260                 if (in_irq())
 261                         regs = get_irq_regs();
 262                 if (regs) {
 263                         pr_info("CPU%d:\n", smp_processor_id());
 264                         show_regs(regs);
 265                 }
 266                 schedule_work(&sysrq_showallcpus);
 267         }
 268 }
 269
 270 static const struct sysrq_key_op sysrq_showallcpus_op = {
 271         .handler        = sysrq_handle_showallcpus,
 272         .help_msg       = "show-backtrace-all-active-cpus(l)",
 273         .action_msg     = "Show backtrace of all active CPUs",
 274         .enable_mask    = SYSRQ_ENABLE_DUMP,
 275 };
 276 #endif
 277
 278 static void sysrq_handle_showregs(int key)
 279 {
 280         struct pt_regs *regs = NULL;
 281
 282         if (in_irq())
 283                 regs = get_irq_regs();
 284         if (regs)
 285                 show_regs(regs);
 286         perf_event_print_debug();
 287 }
 288 static const struct sysrq_key_op sysrq_showregs_op = {
 289         .handler        = sysrq_handle_showregs,
 290         .help_msg       = "show-registers(p)",
 291         .action_msg     = "Show Regs",
 292         .enable_mask    = SYSRQ_ENABLE_DUMP,
 293 };
 294
 295 static void sysrq_handle_showstate(int key)
 296 {
 297         show_state();
 298         show_workqueue_state();
 299 }
 300 static const struct sysrq_key_op sysrq_showstate_op = {
 301         .handler        = sysrq_handle_showstate,
 302         .help_msg       = "show-task-states(t)",
 303         .action_msg     = "Show State",
 304         .enable_mask    = SYSRQ_ENABLE_DUMP,
 305 };
 306
 307 static void sysrq_handle_showstate_blocked(int key)
 308 {
 309         show_state_filter(TASK_UNINTERRUPTIBLE);
 310 }
 311 static const struct sysrq_key_op sysrq_showstate_blocked_op = {
 312         .handler        = sysrq_handle_showstate_blocked,
 313         .help_msg       = "show-blocked-tasks(w)",
 314         .action_msg     = "Show Blocked State",
 315         .enable_mask    = SYSRQ_ENABLE_DUMP,
 316 };
 317
 318 #ifdef CONFIG_TRACING
 319 #include <linux/ftrace.h>
 320
 321 static void sysrq_ftrace_dump(int key)
 322 {
 323         ftrace_dump(DUMP_ALL);
 324 }
 325 static const struct sysrq_key_op sysrq_ftrace_dump_op = {
 326         .handler        = sysrq_ftrace_dump,
 327         .help_msg       = "dump-ftrace-buffer(z)",
 328         .action_msg     = "Dump ftrace buffer",
 329         .enable_mask    = SYSRQ_ENABLE_DUMP,
 330 };
 331 #else
 332 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
 333 #endif
 334
 335 static void sysrq_handle_showmem(int key)
 336 {
 337         show_mem(0, NULL);
 338 }
 339 static const struct sysrq_key_op sysrq_showmem_op = {
 340         .handler        = sysrq_handle_showmem,
 341         .help_msg       = "show-memory-usage(m)",
 342         .action_msg     = "Show Memory",
 343         .enable_mask    = SYSRQ_ENABLE_DUMP,
 344 };
 345
 346 /*
 347  * Signal sysrq helper function.  Sends a signal to all user processes.
 348  */
 349 static void send_sig_all(int sig)
 350 {
 351         struct task_struct *p;
 352
 353         read_lock(&tasklist_lock);
 354         for_each_process(p) {
 355                 if (p->flags & PF_KTHREAD)
 356                         continue;
 357                 if (is_global_init(p))
 358                         continue;
 359
 360                 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
 361         }
 362         read_unlock(&tasklist_lock);
 363 }
 364
 365 static void sysrq_handle_term(int key)
 366 {
 367         send_sig_all(SIGTERM);
 368         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 369 }
 370 static const struct sysrq_key_op sysrq_term_op = {
 371         .handler        = sysrq_handle_term,
 372         .help_msg       = "terminate-all-tasks(e)",
 373         .action_msg     = "Terminate All Tasks",
 374         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 375 };
 376
 377 static void moom_callback(struct work_struct *ignored)
 378 {
 379         const gfp_t gfp_mask = GFP_KERNEL;
 380         struct oom_control oc = {
 381                 .zonelist = node_zonelist(first_memory_node, gfp_mask),
 382                 .nodemask = NULL,
 383                 .memcg = NULL,
 384                 .gfp_mask = gfp_mask,
 385                 .order = -1,
 386         };
 387
 388         mutex_lock(&oom_lock);
 389         if (!out_of_memory(&oc))
 390                 pr_info("OOM request ignored. No task eligible\n");
 391         mutex_unlock(&oom_lock);
 392 }
 393
 394 static DECLARE_WORK(moom_work, moom_callback);
 395
 396 static void sysrq_handle_moom(int key)
 397 {
 398         schedule_work(&moom_work);
 399 }
 400 static const struct sysrq_key_op sysrq_moom_op = {
 401         .handler        = sysrq_handle_moom,
 402         .help_msg       = "memory-full-oom-kill(f)",
 403         .action_msg     = "Manual OOM execution",
 404         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 405 };
 406
 407 static void sysrq_handle_thaw(int key)
 408 {
 409         emergency_thaw_all();
 410 }
 411 static const struct sysrq_key_op sysrq_thaw_op = {
 412         .handler        = sysrq_handle_thaw,
 413         .help_msg       = "thaw-filesystems(j)",
 414         .action_msg     = "Emergency Thaw of all frozen filesystems",
 415         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 416 };
 417
 418 static void sysrq_handle_kill(int key)
 419 {
 420         send_sig_all(SIGKILL);
 421         console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 422 }
 423 static const struct sysrq_key_op sysrq_kill_op = {
 424         .handler        = sysrq_handle_kill,
 425         .help_msg       = "kill-all-tasks(i)",
 426         .action_msg     = "Kill All Tasks",
 427         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 428 };
 429
 430 static void sysrq_handle_unrt(int key)
 431 {
 432         normalize_rt_tasks();
 433 }
 434 static const struct sysrq_key_op sysrq_unrt_op = {
 435         .handler        = sysrq_handle_unrt,
 436         .help_msg       = "nice-all-RT-tasks(n)",
 437         .action_msg     = "Nice All RT Tasks",
 438         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 439 };
 440
 441 /* Key Operations table and lock */
 442 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 443
 444 static const struct sysrq_key_op *sysrq_key_table[62] = {
 445         &sysrq_loglevel_op,             /* 0 */
 446         &sysrq_loglevel_op,             /* 1 */
 447         &sysrq_loglevel_op,             /* 2 */
 448         &sysrq_loglevel_op,             /* 3 */
 449         &sysrq_loglevel_op,             /* 4 */
 450         &sysrq_loglevel_op,             /* 5 */
 451         &sysrq_loglevel_op,             /* 6 */
 452         &sysrq_loglevel_op,             /* 7 */
 453         &sysrq_loglevel_op,             /* 8 */
 454         &sysrq_loglevel_op,             /* 9 */
 455
 456         /*
 457          * a: Don't use for system provided sysrqs, it is handled specially on
 458          * sparc and will never arrive.
 459          */
 460         NULL,                           /* a */
 461         &sysrq_reboot_op,               /* b */
 462         &sysrq_crash_op,                /* c */
 463         &sysrq_showlocks_op,            /* d */
 464         &sysrq_term_op,                 /* e */
 465         &sysrq_moom_op,                 /* f */
 466         /* g: May be registered for the kernel debugger */
 467         NULL,                           /* g */
 468         NULL,                           /* h - reserved for help */
 469         &sysrq_kill_op,                 /* i */
 470 #ifdef CONFIG_BLOCK
 471         &sysrq_thaw_op,                 /* j */
 472 #else
 473         NULL,                           /* j */
 474 #endif
 475         &sysrq_SAK_op,                  /* k */
 476 #ifdef CONFIG_SMP
 477         &sysrq_showallcpus_op,          /* l */
 478 #else
 479         NULL,                           /* l */
 480 #endif
 481         &sysrq_showmem_op,              /* m */
 482         &sysrq_unrt_op,                 /* n */
 483         /* o: This will often be registered as 'Off' at init time */
 484         NULL,                           /* o */
 485         &sysrq_showregs_op,             /* p */
 486         &sysrq_show_timers_op,          /* q */
 487         &sysrq_unraw_op,                /* r */
 488         &sysrq_sync_op,                 /* s */
 489         &sysrq_showstate_op,            /* t */
 490         &sysrq_mountro_op,              /* u */
 491         /* v: May be registered for frame buffer console restore */
 492         NULL,                           /* v */
 493         &sysrq_showstate_blocked_op,    /* w */
 494         /* x: May be registered on mips for TLB dump */
 495         /* x: May be registered on ppc/powerpc for xmon */
 496         /* x: May be registered on sparc64 for global PMU dump */
 497         NULL,                           /* x */
 498         /* y: May be registered on sparc64 for global register dump */
 499         NULL,                           /* y */
 500         &sysrq_ftrace_dump_op,          /* z */
 501         NULL,                           /* A */
 502         NULL,                           /* B */
 503         NULL,                           /* C */
 504         NULL,                           /* D */
 505         NULL,                           /* E */
 506         NULL,                           /* F */
 507         NULL,                           /* G */
 508         NULL,                           /* H */
 509         NULL,                           /* I */
 510         NULL,                           /* J */
 511         NULL,                           /* K */
 512         NULL,                           /* L */
 513         NULL,                           /* M */
 514         NULL,                           /* N */
 515         NULL,                           /* O */
 516         NULL,                           /* P */
 517         NULL,                           /* Q */
 518         NULL,                           /* R */
 519         NULL,                           /* S */
 520         NULL,                           /* T */
 521         NULL,                           /* U */
 522         NULL,                           /* V */
 523         NULL,                           /* W */
 524         NULL,                           /* X */
 525         NULL,                           /* Y */
 526         NULL,                           /* Z */
 527 };
 528
 529 /* key2index calculation, -1 on invalid index */
 530 static int sysrq_key_table_key2index(int key)
 531 {
 532         int retval;
 533
 534         if ((key >= '0') && (key <= '9'))
 535                 retval = key - '0';
 536         else if ((key >= 'a') && (key <= 'z'))
 537                 retval = key + 10 - 'a';
 538         else if ((key >= 'A') && (key <= 'Z'))
 539                 retval = key + 36 - 'A';
 540         else
 541                 retval = -1;
 542         return retval;
 543 }
 544
 545 /*
 546  * get and put functions for the table, exposed to modules.
 547  */
 548 static const struct sysrq_key_op *__sysrq_get_key_op(int key)
 549 {
 550         const struct sysrq_key_op *op_p = NULL;
 551         int i;
 552
 553         i = sysrq_key_table_key2index(key);
 554         if (i != -1)
 555                 op_p = sysrq_key_table[i];
 556
 557         return op_p;
 558 }
 559
 560 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p)
 561 {
 562         int i = sysrq_key_table_key2index(key);
 563
 564         if (i != -1)
 565                 sysrq_key_table[i] = op_p;
 566 }
 567
 568 void __handle_sysrq(int key, bool check_mask)
 569 {
 570         const struct sysrq_key_op *op_p;
 571         int orig_log_level;
 572         int orig_suppress_printk;
 573         int i;
 574
 575         orig_suppress_printk = suppress_printk;
 576         suppress_printk = 0;
 577
 578         rcu_sysrq_start();
 579         rcu_read_lock();
 580         /*
 581          * Raise the apparent loglevel to maximum so that the sysrq header
 582          * is shown to provide the user with positive feedback.  We do not
 583          * simply emit this at KERN_EMERG as that would change message
 584          * routing in the consumers of /proc/kmsg.
 585          */
 586         orig_log_level = console_loglevel;
 587         console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 588
 589         op_p = __sysrq_get_key_op(key);
 590         if (op_p) {
 591                 /*
 592                  * Should we check for enabled operations (/proc/sysrq-trigger
 593                  * should not) and is the invoked operation enabled?
 594                  */
 595                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 596                         pr_info("%s\n", op_p->action_msg);
 597                         console_loglevel = orig_log_level;
 598                         op_p->handler(key);
 599                 } else {
 600                         pr_info("This sysrq operation is disabled.\n");
 601                         console_loglevel = orig_log_level;
 602                 }
 603         } else {
 604                 pr_info("HELP : ");
 605                 /* Only print the help msg once per handler */
 606                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 607                         if (sysrq_key_table[i]) {
 608                                 int j;
 609
 610                                 for (j = 0; sysrq_key_table[i] !=
 611                                                 sysrq_key_table[j]; j++)
 612                                         ;
 613                                 if (j != i)
 614                                         continue;
 615                                 pr_cont("%s ", sysrq_key_table[i]->help_msg);
 616                         }
 617                 }
 618                 pr_cont("\n");
 619                 console_loglevel = orig_log_level;
 620         }
 621         rcu_read_unlock();
 622         rcu_sysrq_end();
 623
 624         suppress_printk = orig_suppress_printk;
 625 }
 626
 627 void handle_sysrq(int key)
 628 {
 629         if (sysrq_on())
 630                 __handle_sysrq(key, true);
 631 }
 632 EXPORT_SYMBOL(handle_sysrq);
 633
 634 #ifdef CONFIG_INPUT
 635 static int sysrq_reset_downtime_ms;
 636
 637 /* Simple translation table for the SysRq keys */
 638 static const unsigned char sysrq_xlate[KEY_CNT] =
 639         "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 640         "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 641         "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 642         "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 643         "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 644         "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 645         "\r\000/";                                      /* 0x60 - 0x6f */
 646
 647 struct sysrq_state {
 648         struct input_handle handle;
 649         struct work_struct reinject_work;
 650         unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 651         unsigned int alt;
 652         unsigned int alt_use;
 653         unsigned int shift;
 654         unsigned int shift_use;
 655         bool active;
 656         bool need_reinject;
 657         bool reinjecting;
 658
 659         /* reset sequence handling */
 660         bool reset_canceled;
 661         bool reset_requested;
 662         unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 663         int reset_seq_len;
 664         int reset_seq_cnt;
 665         int reset_seq_version;
 666         struct timer_list keyreset_timer;
 667 };
 668
 669 #define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 670 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 671 static unsigned int sysrq_reset_seq_len;
 672 static unsigned int sysrq_reset_seq_version = 1;
 673
 674 static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 675 {
 676         int i;
 677         unsigned short key;
 678
 679         state->reset_seq_cnt = 0;
 680
 681         for (i = 0; i < sysrq_reset_seq_len; i++) {
 682                 key = sysrq_reset_seq[i];
 683
 684                 if (key == KEY_RESERVED || key > KEY_MAX)
 685                         break;
 686
 687                 __set_bit(key, state->reset_keybit);
 688                 state->reset_seq_len++;
 689
 690                 if (test_bit(key, state->key_down))
 691                         state->reset_seq_cnt++;
 692         }
 693
 694         /* Disable reset until old keys are not released */
 695         state->reset_canceled = state->reset_seq_cnt != 0;
 696
 697         state->reset_seq_version = sysrq_reset_seq_version;
 698 }
 699
 700 static void sysrq_do_reset(struct timer_list *t)
 701 {
 702         struct sysrq_state *state = from_timer(state, t, keyreset_timer);
 703
 704         state->reset_requested = true;
 705
 706         orderly_reboot();
 707 }
 708
 709 static void sysrq_handle_reset_request(struct sysrq_state *state)
 710 {
 711         if (state->reset_requested)
 712                 __handle_sysrq(sysrq_xlate[KEY_B], false);
 713
 714         if (sysrq_reset_downtime_ms)
 715                 mod_timer(&state->keyreset_timer,
 716                         jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 717         else
 718                 sysrq_do_reset(&state->keyreset_timer);
 719 }
 720
 721 static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 722                                         unsigned int code, int value)
 723 {
 724         if (!test_bit(code, state->reset_keybit)) {
 725                 /*
 726                  * Pressing any key _not_ in reset sequence cancels
 727                  * the reset sequence.  Also cancelling the timer in
 728                  * case additional keys were pressed after a reset
 729                  * has been requested.
 730                  */
 731                 if (value && state->reset_seq_cnt) {
 732                         state->reset_canceled = true;
 733                         del_timer(&state->keyreset_timer);
 734                 }
 735         } else if (value == 0) {
 736                 /*
 737                  * Key release - all keys in the reset sequence need
 738                  * to be pressed and held for the reset timeout
 739                  * to hold.
 740                  */
 741                 del_timer(&state->keyreset_timer);
 742
 743                 if (--state->reset_seq_cnt == 0)
 744                         state->reset_canceled = false;
 745         } else if (value == 1) {
 746                 /* key press, not autorepeat */
 747                 if (++state->reset_seq_cnt == state->reset_seq_len &&
 748                     !state->reset_canceled) {
 749                         sysrq_handle_reset_request(state);
 750                 }
 751         }
 752 }
 753
 754 #ifdef CONFIG_OF
 755 static void sysrq_of_get_keyreset_config(void)
 756 {
 757         u32 key;
 758         struct device_node *np;
 759         struct property *prop;
 760         const __be32 *p;
 761
 762         np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 763         if (!np) {
 764                 pr_debug("No sysrq node found");
 765                 return;
 766         }
 767
 768         /* Reset in case a __weak definition was present */
 769         sysrq_reset_seq_len = 0;
 770
 771         of_property_for_each_u32(np, "keyset", prop, p, key) {
 772                 if (key == KEY_RESERVED || key > KEY_MAX ||
 773                     sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 774                         break;
 775
 776                 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 777         }
 778
 779         /* Get reset timeout if any. */
 780         of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 781
 782         of_node_put(np);
 783 }
 784 #else
 785 static void sysrq_of_get_keyreset_config(void)
 786 {
 787 }
 788 #endif
 789
 790 static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 791 {
 792         struct sysrq_state *sysrq =
 793                         container_of(work, struct sysrq_state, reinject_work);
 794         struct input_handle *handle = &sysrq->handle;
 795         unsigned int alt_code = sysrq->alt_use;
 796
 797         if (sysrq->need_reinject) {
 798                 /* we do not want the assignment to be reordered */
 799                 sysrq->reinjecting = true;
 800                 mb();
 801
 802                 /* Simulate press and release of Alt + SysRq */
 803                 input_inject_event(handle, EV_KEY, alt_code, 1);
 804                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 805                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 806
 807                 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 808                 input_inject_event(handle, EV_KEY, alt_code, 0);
 809                 input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 810
 811                 mb();
 812                 sysrq->reinjecting = false;
 813         }
 814 }
 815
 816 static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 817                                   unsigned int code, int value)
 818 {
 819         bool was_active = sysrq->active;
 820         bool suppress;
 821
 822         switch (code) {
 823
 824         case KEY_LEFTALT:
 825         case KEY_RIGHTALT:
 826                 if (!value) {
 827                         /* One of ALTs is being released */
 828                         if (sysrq->active && code == sysrq->alt_use)
 829                                 sysrq->active = false;
 830
 831                         sysrq->alt = KEY_RESERVED;
 832
 833                 } else if (value != 2) {
 834                         sysrq->alt = code;
 835                         sysrq->need_reinject = false;
 836                 }
 837                 break;
 838
 839         case KEY_LEFTSHIFT:
 840         case KEY_RIGHTSHIFT:
 841                 if (!value)
 842                         sysrq->shift = KEY_RESERVED;
 843                 else if (value != 2)
 844                         sysrq->shift = code;
 845                 break;
 846
 847         case KEY_SYSRQ:
 848                 if (value == 1 && sysrq->alt != KEY_RESERVED) {
 849                         sysrq->active = true;
 850                         sysrq->alt_use = sysrq->alt;
 851                         /* either RESERVED (for released) or actual code */
 852                         sysrq->shift_use = sysrq->shift;
 853                         /*
 854                          * If nothing else will be pressed we'll need
 855                          * to re-inject Alt-SysRq keysroke.
 856                          */
 857                         sysrq->need_reinject = true;
 858                 }
 859
 860                 /*
 861                  * Pretend that sysrq was never pressed at all. This
 862                  * is needed to properly handle KGDB which will try
 863                  * to release all keys after exiting debugger. If we
 864                  * do not clear key bit it KGDB will end up sending
 865                  * release events for Alt and SysRq, potentially
 866                  * triggering print screen function.
 867                  */
 868                 if (sysrq->active)
 869                         clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 870
 871                 break;
 872
 873         default:
 874                 if (sysrq->active && value && value != 2) {
 875                         unsigned char c = sysrq_xlate[code];
 876
 877                         sysrq->need_reinject = false;
 878                         if (sysrq->shift_use != KEY_RESERVED)
 879                                 c = toupper(c);
 880                         __handle_sysrq(c, true);
 881                 }
 882                 break;
 883         }
 884
 885         suppress = sysrq->active;
 886
 887         if (!sysrq->active) {
 888
 889                 /*
 890                  * See if reset sequence has changed since the last time.
 891                  */
 892                 if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 893                         sysrq_parse_reset_sequence(sysrq);
 894
 895                 /*
 896                  * If we are not suppressing key presses keep track of
 897                  * keyboard state so we can release keys that have been
 898                  * pressed before entering SysRq mode.
 899                  */
 900                 if (value)
 901                         set_bit(code, sysrq->key_down);
 902                 else
 903                         clear_bit(code, sysrq->key_down);
 904
 905                 if (was_active)
 906                         schedule_work(&sysrq->reinject_work);
 907
 908                 /* Check for reset sequence */
 909                 sysrq_detect_reset_sequence(sysrq, code, value);
 910
 911         } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 912                 /*
 913                  * Pass on release events for keys that was pressed before
 914                  * entering SysRq mode.
 915                  */
 916                 suppress = false;
 917         }
 918
 919         return suppress;
 920 }
 921
 922 static bool sysrq_filter(struct input_handle *handle,
 923                          unsigned int type, unsigned int code, int value)
 924 {
 925         struct sysrq_state *sysrq = handle->private;
 926         bool suppress;
 927
 928         /*
 929          * Do not filter anything if we are in the process of re-injecting
 930          * Alt+SysRq combination.
 931          */
 932         if (sysrq->reinjecting)
 933                 return false;
 934
 935         switch (type) {
 936
 937         case EV_SYN:
 938                 suppress = false;
 939                 break;
 940
 941         case EV_KEY:
 942                 suppress = sysrq_handle_keypress(sysrq, code, value);
 943                 break;
 944
 945         default:
 946                 suppress = sysrq->active;
 947                 break;
 948         }
 949
 950         return suppress;
 951 }
 952
 953 static int sysrq_connect(struct input_handler *handler,
 954                          struct input_dev *dev,
 955                          const struct input_device_id *id)
 956 {
 957         struct sysrq_state *sysrq;
 958         int error;
 959
 960         sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 961         if (!sysrq)
 962                 return -ENOMEM;
 963
 964         INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 965
 966         sysrq->handle.dev = dev;
 967         sysrq->handle.handler = handler;
 968         sysrq->handle.name = "sysrq";
 969         sysrq->handle.private = sysrq;
 970         timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 971
 972         error = input_register_handle(&sysrq->handle);
 973         if (error) {
 974                 pr_err("Failed to register input sysrq handler, error %d\n",
 975                         error);
 976                 goto err_free;
 977         }
 978
 979         error = input_open_device(&sysrq->handle);
 980         if (error) {
 981                 pr_err("Failed to open input device, error %d\n", error);
 982                 goto err_unregister;
 983         }
 984
 985         return 0;
 986
 987  err_unregister:
 988         input_unregister_handle(&sysrq->handle);
 989  err_free:
 990         kfree(sysrq);
 991         return error;
 992 }
 993
 994 static void sysrq_disconnect(struct input_handle *handle)
 995 {
 996         struct sysrq_state *sysrq = handle->private;
 997
 998         input_close_device(handle);
 999         cancel_work_sync(&sysrq->reinject_work);
1000         del_timer_sync(&sysrq->keyreset_timer);
1001         input_unregister_handle(handle);
1002         kfree(sysrq);
1003 }
1004
1005 /*
1006  * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1007  * keyboards have SysRq key predefined and so user may add it to keymap
1008  * later, but we expect all such keyboards to have left alt.
1009  */
1010 static const struct input_device_id sysrq_ids[] = {
1011         {
1012                 .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1013                                 INPUT_DEVICE_ID_MATCH_KEYBIT,
1014                 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1015                 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1016         },
1017         { },
1018 };
1019
1020 static struct input_handler sysrq_handler = {
1021         .filter         = sysrq_filter,
1022         .connect        = sysrq_connect,
1023         .disconnect     = sysrq_disconnect,
1024         .name           = "sysrq",
1025         .id_table       = sysrq_ids,
1026 };
1027
1028 static inline void sysrq_register_handler(void)
1029 {
1030         int error;
1031
1032         sysrq_of_get_keyreset_config();
1033
1034         error = input_register_handler(&sysrq_handler);
1035         if (error)
1036                 pr_err("Failed to register input handler, error %d", error);
1037 }
1038
1039 static inline void sysrq_unregister_handler(void)
1040 {
1041         input_unregister_handler(&sysrq_handler);
1042 }
1043
1044 static int sysrq_reset_seq_param_set(const char *buffer,
1045                                      const struct kernel_param *kp)
1046 {
1047         unsigned long val;
1048         int error;
1049
1050         error = kstrtoul(buffer, 0, &val);
1051         if (error < 0)
1052                 return error;
1053
1054         if (val > KEY_MAX)
1055                 return -EINVAL;
1056
1057         *((unsigned short *)kp->arg) = val;
1058         sysrq_reset_seq_version++;
1059
1060         return 0;
1061 }
1062
1063 static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1064         .get    = param_get_ushort,
1065         .set    = sysrq_reset_seq_param_set,
1066 };
1067
1068 #define param_check_sysrq_reset_seq(name, p)    \
1069         __param_check(name, p, unsigned short)
1070
1071 /*
1072  * not really modular, but the easiest way to keep compat with existing
1073  * bootargs behaviour is to continue using module_param here.
1074  */
1075 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1076                          &sysrq_reset_seq_len, 0644);
1077
1078 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1079
1080 #else
1081
1082 static inline void sysrq_register_handler(void)
1083 {
1084 }
1085
1086 static inline void sysrq_unregister_handler(void)
1087 {
1088 }
1089
1090 #endif /* CONFIG_INPUT */
1091
1092 int sysrq_toggle_support(int enable_mask)
1093 {
1094         bool was_enabled = sysrq_on();
1095
1096         sysrq_enabled = enable_mask;
1097
1098         if (was_enabled != sysrq_on()) {
1099                 if (sysrq_on())
1100                         sysrq_register_handler();
1101                 else
1102                         sysrq_unregister_handler();
1103         }
1104
1105         return 0;
1106 }
1107 EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1108
1109 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p,
1110                                 const struct sysrq_key_op *remove_op_p)
1111 {
1112         int retval;
1113
1114         spin_lock(&sysrq_key_table_lock);
1115         if (__sysrq_get_key_op(key) == remove_op_p) {
1116                 __sysrq_put_key_op(key, insert_op_p);
1117                 retval = 0;
1118         } else {
1119                 retval = -1;
1120         }
1121         spin_unlock(&sysrq_key_table_lock);
1122
1123         /*
1124          * A concurrent __handle_sysrq either got the old op or the new op.
1125          * Wait for it to go away before returning, so the code for an old
1126          * op is not freed (eg. on module unload) while it is in use.
1127          */
1128         synchronize_rcu();
1129
1130         return retval;
1131 }
1132
1133 int register_sysrq_key(int key, const struct sysrq_key_op *op_p)
1134 {
1135         return __sysrq_swap_key_ops(key, op_p, NULL);
1136 }
1137 EXPORT_SYMBOL(register_sysrq_key);
1138
1139 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p)
1140 {
1141         return __sysrq_swap_key_ops(key, NULL, op_p);
1142 }
1143 EXPORT_SYMBOL(unregister_sysrq_key);
1144
1145 #ifdef CONFIG_PROC_FS
1146 /*
1147  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1148  */
1149 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1150                                    size_t count, loff_t *ppos)
1151 {
1152         if (count) {
1153                 char c;
1154
1155                 if (get_user(c, buf))
1156                         return -EFAULT;
1157                 __handle_sysrq(c, false);
1158         }
1159
1160         return count;
1161 }
1162
1163 static const struct proc_ops sysrq_trigger_proc_ops = {
1164         .proc_write     = write_sysrq_trigger,
1165         .proc_lseek     = noop_llseek,
1166 };
1167
1168 static void sysrq_init_procfs(void)
1169 {
1170         if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1171                          &sysrq_trigger_proc_ops))
1172                 pr_err("Failed to register proc interface\n");
1173 }
1174
1175 #else
1176
1177 static inline void sysrq_init_procfs(void)
1178 {
1179 }
1180
1181 #endif /* CONFIG_PROC_FS */
1182
1183 static int __init sysrq_init(void)
1184 {
1185         sysrq_init_procfs();
1186
1187         if (sysrq_on())
1188                 sysrq_register_handler();
1189
1190         return 0;
1191 }
1192 device_initcall(sysrq_init);