linux/drivers/tty/sysrq.c
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   1/*
   2 *      Linux Magic System Request Key Hacks
   3 *
   4 *      (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   5 *      based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
   6 *
   7 *      (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
   8 *      overhauled to use key registration
   9 *      based upon discusions in irc://irc.openprojects.net/#kernelnewbies
  10 *
  11 *      Copyright (c) 2010 Dmitry Torokhov
  12 *      Input handler conversion
  13 */
  14
  15#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  16
  17#include <linux/sched.h>
  18#include <linux/sched/rt.h>
  19#include <linux/interrupt.h>
  20#include <linux/mm.h>
  21#include <linux/fs.h>
  22#include <linux/mount.h>
  23#include <linux/kdev_t.h>
  24#include <linux/major.h>
  25#include <linux/reboot.h>
  26#include <linux/sysrq.h>
  27#include <linux/kbd_kern.h>
  28#include <linux/proc_fs.h>
  29#include <linux/nmi.h>
  30#include <linux/quotaops.h>
  31#include <linux/perf_event.h>
  32#include <linux/kernel.h>
  33#include <linux/module.h>
  34#include <linux/suspend.h>
  35#include <linux/writeback.h>
  36#include <linux/swap.h>
  37#include <linux/spinlock.h>
  38#include <linux/vt_kern.h>
  39#include <linux/workqueue.h>
  40#include <linux/hrtimer.h>
  41#include <linux/oom.h>
  42#include <linux/slab.h>
  43#include <linux/input.h>
  44#include <linux/uaccess.h>
  45#include <linux/moduleparam.h>
  46#include <linux/jiffies.h>
  47
  48#include <asm/ptrace.h>
  49#include <asm/irq_regs.h>
  50
  51/* Whether we react on sysrq keys or just ignore them */
  52static int __read_mostly sysrq_enabled = SYSRQ_DEFAULT_ENABLE;
  53static bool __read_mostly sysrq_always_enabled;
  54
  55unsigned short platform_sysrq_reset_seq[] __weak = { KEY_RESERVED };
  56int sysrq_reset_downtime_ms __weak;
  57
  58static bool sysrq_on(void)
  59{
  60        return sysrq_enabled || sysrq_always_enabled;
  61}
  62
  63/*
  64 * A value of 1 means 'all', other nonzero values are an op mask:
  65 */
  66static bool sysrq_on_mask(int mask)
  67{
  68        return sysrq_always_enabled ||
  69               sysrq_enabled == 1 ||
  70               (sysrq_enabled & mask);
  71}
  72
  73static int __init sysrq_always_enabled_setup(char *str)
  74{
  75        sysrq_always_enabled = true;
  76        pr_info("sysrq always enabled.\n");
  77
  78        return 1;
  79}
  80
  81__setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  82
  83
  84static void sysrq_handle_loglevel(int key)
  85{
  86        int i;
  87
  88        i = key - '0';
  89        console_loglevel = 7;
  90        printk("Loglevel set to %d\n", i);
  91        console_loglevel = i;
  92}
  93static struct sysrq_key_op sysrq_loglevel_op = {
  94        .handler        = sysrq_handle_loglevel,
  95        .help_msg       = "loglevel(0-9)",
  96        .action_msg     = "Changing Loglevel",
  97        .enable_mask    = SYSRQ_ENABLE_LOG,
  98};
  99
 100#ifdef CONFIG_VT
 101static void sysrq_handle_SAK(int key)
 102{
 103        struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 104        schedule_work(SAK_work);
 105}
 106static struct sysrq_key_op sysrq_SAK_op = {
 107        .handler        = sysrq_handle_SAK,
 108        .help_msg       = "sak(k)",
 109        .action_msg     = "SAK",
 110        .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 111};
 112#else
 113#define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
 114#endif
 115
 116#ifdef CONFIG_VT
 117static void sysrq_handle_unraw(int key)
 118{
 119        vt_reset_unicode(fg_console);
 120}
 121
 122static struct sysrq_key_op sysrq_unraw_op = {
 123        .handler        = sysrq_handle_unraw,
 124        .help_msg       = "unraw(r)",
 125        .action_msg     = "Keyboard mode set to system default",
 126        .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 127};
 128#else
 129#define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
 130#endif /* CONFIG_VT */
 131
 132static void sysrq_handle_crash(int key)
 133{
 134        char *killer = NULL;
 135
 136        panic_on_oops = 1;      /* force panic */
 137        wmb();
 138        *killer = 1;
 139}
 140static struct sysrq_key_op sysrq_crash_op = {
 141        .handler        = sysrq_handle_crash,
 142        .help_msg       = "crash(c)",
 143        .action_msg     = "Trigger a crash",
 144        .enable_mask    = SYSRQ_ENABLE_DUMP,
 145};
 146
 147static void sysrq_handle_reboot(int key)
 148{
 149        lockdep_off();
 150        local_irq_enable();
 151        emergency_restart();
 152}
 153static struct sysrq_key_op sysrq_reboot_op = {
 154        .handler        = sysrq_handle_reboot,
 155        .help_msg       = "reboot(b)",
 156        .action_msg     = "Resetting",
 157        .enable_mask    = SYSRQ_ENABLE_BOOT,
 158};
 159
 160static void sysrq_handle_sync(int key)
 161{
 162        emergency_sync();
 163}
 164static struct sysrq_key_op sysrq_sync_op = {
 165        .handler        = sysrq_handle_sync,
 166        .help_msg       = "sync(s)",
 167        .action_msg     = "Emergency Sync",
 168        .enable_mask    = SYSRQ_ENABLE_SYNC,
 169};
 170
 171static void sysrq_handle_show_timers(int key)
 172{
 173        sysrq_timer_list_show();
 174}
 175
 176static struct sysrq_key_op sysrq_show_timers_op = {
 177        .handler        = sysrq_handle_show_timers,
 178        .help_msg       = "show-all-timers(q)",
 179        .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 180};
 181
 182static void sysrq_handle_mountro(int key)
 183{
 184        emergency_remount();
 185}
 186static struct sysrq_key_op sysrq_mountro_op = {
 187        .handler        = sysrq_handle_mountro,
 188        .help_msg       = "unmount(u)",
 189        .action_msg     = "Emergency Remount R/O",
 190        .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 191};
 192
 193#ifdef CONFIG_LOCKDEP
 194static void sysrq_handle_showlocks(int key)
 195{
 196        debug_show_all_locks();
 197}
 198
 199static struct sysrq_key_op sysrq_showlocks_op = {
 200        .handler        = sysrq_handle_showlocks,
 201        .help_msg       = "show-all-locks(d)",
 202        .action_msg     = "Show Locks Held",
 203};
 204#else
 205#define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL)
 206#endif
 207
 208#ifdef CONFIG_SMP
 209static DEFINE_SPINLOCK(show_lock);
 210
 211static void showacpu(void *dummy)
 212{
 213        unsigned long flags;
 214
 215        /* Idle CPUs have no interesting backtrace. */
 216        if (idle_cpu(smp_processor_id()))
 217                return;
 218
 219        spin_lock_irqsave(&show_lock, flags);
 220        printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 221        show_stack(NULL, NULL);
 222        spin_unlock_irqrestore(&show_lock, flags);
 223}
 224
 225static void sysrq_showregs_othercpus(struct work_struct *dummy)
 226{
 227        smp_call_function(showacpu, NULL, 0);
 228}
 229
 230static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 231
 232static void sysrq_handle_showallcpus(int key)
 233{
 234        /*
 235         * Fall back to the workqueue based printing if the
 236         * backtrace printing did not succeed or the
 237         * architecture has no support for it:
 238         */
 239        if (!trigger_all_cpu_backtrace()) {
 240                struct pt_regs *regs = get_irq_regs();
 241
 242                if (regs) {
 243                        printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 244                        show_regs(regs);
 245                }
 246                schedule_work(&sysrq_showallcpus);
 247        }
 248}
 249
 250static struct sysrq_key_op sysrq_showallcpus_op = {
 251        .handler        = sysrq_handle_showallcpus,
 252        .help_msg       = "show-backtrace-all-active-cpus(l)",
 253        .action_msg     = "Show backtrace of all active CPUs",
 254        .enable_mask    = SYSRQ_ENABLE_DUMP,
 255};
 256#endif
 257
 258static void sysrq_handle_showregs(int key)
 259{
 260        struct pt_regs *regs = get_irq_regs();
 261        if (regs)
 262                show_regs(regs);
 263        perf_event_print_debug();
 264}
 265static struct sysrq_key_op sysrq_showregs_op = {
 266        .handler        = sysrq_handle_showregs,
 267        .help_msg       = "show-registers(p)",
 268        .action_msg     = "Show Regs",
 269        .enable_mask    = SYSRQ_ENABLE_DUMP,
 270};
 271
 272static void sysrq_handle_showstate(int key)
 273{
 274        show_state();
 275}
 276static struct sysrq_key_op sysrq_showstate_op = {
 277        .handler        = sysrq_handle_showstate,
 278        .help_msg       = "show-task-states(t)",
 279        .action_msg     = "Show State",
 280        .enable_mask    = SYSRQ_ENABLE_DUMP,
 281};
 282
 283static void sysrq_handle_showstate_blocked(int key)
 284{
 285        show_state_filter(TASK_UNINTERRUPTIBLE);
 286}
 287static struct sysrq_key_op sysrq_showstate_blocked_op = {
 288        .handler        = sysrq_handle_showstate_blocked,
 289        .help_msg       = "show-blocked-tasks(w)",
 290        .action_msg     = "Show Blocked State",
 291        .enable_mask    = SYSRQ_ENABLE_DUMP,
 292};
 293
 294#ifdef CONFIG_TRACING
 295#include <linux/ftrace.h>
 296
 297static void sysrq_ftrace_dump(int key)
 298{
 299        ftrace_dump(DUMP_ALL);
 300}
 301static struct sysrq_key_op sysrq_ftrace_dump_op = {
 302        .handler        = sysrq_ftrace_dump,
 303        .help_msg       = "dump-ftrace-buffer(z)",
 304        .action_msg     = "Dump ftrace buffer",
 305        .enable_mask    = SYSRQ_ENABLE_DUMP,
 306};
 307#else
 308#define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
 309#endif
 310
 311static void sysrq_handle_showmem(int key)
 312{
 313        show_mem(0);
 314}
 315static struct sysrq_key_op sysrq_showmem_op = {
 316        .handler        = sysrq_handle_showmem,
 317        .help_msg       = "show-memory-usage(m)",
 318        .action_msg     = "Show Memory",
 319        .enable_mask    = SYSRQ_ENABLE_DUMP,
 320};
 321
 322/*
 323 * Signal sysrq helper function.  Sends a signal to all user processes.
 324 */
 325static void send_sig_all(int sig)
 326{
 327        struct task_struct *p;
 328
 329        read_lock(&tasklist_lock);
 330        for_each_process(p) {
 331                if (p->flags & PF_KTHREAD)
 332                        continue;
 333                if (is_global_init(p))
 334                        continue;
 335
 336                do_send_sig_info(sig, SEND_SIG_FORCED, p, true);
 337        }
 338        read_unlock(&tasklist_lock);
 339}
 340
 341static void sysrq_handle_term(int key)
 342{
 343        send_sig_all(SIGTERM);
 344        console_loglevel = 8;
 345}
 346static struct sysrq_key_op sysrq_term_op = {
 347        .handler        = sysrq_handle_term,
 348        .help_msg       = "terminate-all-tasks(e)",
 349        .action_msg     = "Terminate All Tasks",
 350        .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 351};
 352
 353static void moom_callback(struct work_struct *ignored)
 354{
 355        out_of_memory(node_zonelist(first_online_node, GFP_KERNEL), GFP_KERNEL,
 356                      0, NULL, true);
 357}
 358
 359static DECLARE_WORK(moom_work, moom_callback);
 360
 361static void sysrq_handle_moom(int key)
 362{
 363        schedule_work(&moom_work);
 364}
 365static struct sysrq_key_op sysrq_moom_op = {
 366        .handler        = sysrq_handle_moom,
 367        .help_msg       = "memory-full-oom-kill(f)",
 368        .action_msg     = "Manual OOM execution",
 369        .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 370};
 371
 372#ifdef CONFIG_BLOCK
 373static void sysrq_handle_thaw(int key)
 374{
 375        emergency_thaw_all();
 376}
 377static struct sysrq_key_op sysrq_thaw_op = {
 378        .handler        = sysrq_handle_thaw,
 379        .help_msg       = "thaw-filesystems(j)",
 380        .action_msg     = "Emergency Thaw of all frozen filesystems",
 381        .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 382};
 383#endif
 384
 385static void sysrq_handle_kill(int key)
 386{
 387        send_sig_all(SIGKILL);
 388        console_loglevel = 8;
 389}
 390static struct sysrq_key_op sysrq_kill_op = {
 391        .handler        = sysrq_handle_kill,
 392        .help_msg       = "kill-all-tasks(i)",
 393        .action_msg     = "Kill All Tasks",
 394        .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 395};
 396
 397static void sysrq_handle_unrt(int key)
 398{
 399        normalize_rt_tasks();
 400}
 401static struct sysrq_key_op sysrq_unrt_op = {
 402        .handler        = sysrq_handle_unrt,
 403        .help_msg       = "nice-all-RT-tasks(n)",
 404        .action_msg     = "Nice All RT Tasks",
 405        .enable_mask    = SYSRQ_ENABLE_RTNICE,
 406};
 407
 408/* Key Operations table and lock */
 409static DEFINE_SPINLOCK(sysrq_key_table_lock);
 410
 411static struct sysrq_key_op *sysrq_key_table[36] = {
 412        &sysrq_loglevel_op,             /* 0 */
 413        &sysrq_loglevel_op,             /* 1 */
 414        &sysrq_loglevel_op,             /* 2 */
 415        &sysrq_loglevel_op,             /* 3 */
 416        &sysrq_loglevel_op,             /* 4 */
 417        &sysrq_loglevel_op,             /* 5 */
 418        &sysrq_loglevel_op,             /* 6 */
 419        &sysrq_loglevel_op,             /* 7 */
 420        &sysrq_loglevel_op,             /* 8 */
 421        &sysrq_loglevel_op,             /* 9 */
 422
 423        /*
 424         * a: Don't use for system provided sysrqs, it is handled specially on
 425         * sparc and will never arrive.
 426         */
 427        NULL,                           /* a */
 428        &sysrq_reboot_op,               /* b */
 429        &sysrq_crash_op,                /* c & ibm_emac driver debug */
 430        &sysrq_showlocks_op,            /* d */
 431        &sysrq_term_op,                 /* e */
 432        &sysrq_moom_op,                 /* f */
 433        /* g: May be registered for the kernel debugger */
 434        NULL,                           /* g */
 435        NULL,                           /* h - reserved for help */
 436        &sysrq_kill_op,                 /* i */
 437#ifdef CONFIG_BLOCK
 438        &sysrq_thaw_op,                 /* j */
 439#else
 440        NULL,                           /* j */
 441#endif
 442        &sysrq_SAK_op,                  /* k */
 443#ifdef CONFIG_SMP
 444        &sysrq_showallcpus_op,          /* l */
 445#else
 446        NULL,                           /* l */
 447#endif
 448        &sysrq_showmem_op,              /* m */
 449        &sysrq_unrt_op,                 /* n */
 450        /* o: This will often be registered as 'Off' at init time */
 451        NULL,                           /* o */
 452        &sysrq_showregs_op,             /* p */
 453        &sysrq_show_timers_op,          /* q */
 454        &sysrq_unraw_op,                /* r */
 455        &sysrq_sync_op,                 /* s */
 456        &sysrq_showstate_op,            /* t */
 457        &sysrq_mountro_op,              /* u */
 458        /* v: May be registered for frame buffer console restore */
 459        NULL,                           /* v */
 460        &sysrq_showstate_blocked_op,    /* w */
 461        /* x: May be registered on ppc/powerpc for xmon */
 462        /* x: May be registered on sparc64 for global PMU dump */
 463        NULL,                           /* x */
 464        /* y: May be registered on sparc64 for global register dump */
 465        NULL,                           /* y */
 466        &sysrq_ftrace_dump_op,          /* z */
 467};
 468
 469/* key2index calculation, -1 on invalid index */
 470static int sysrq_key_table_key2index(int key)
 471{
 472        int retval;
 473
 474        if ((key >= '0') && (key <= '9'))
 475                retval = key - '0';
 476        else if ((key >= 'a') && (key <= 'z'))
 477                retval = key + 10 - 'a';
 478        else
 479                retval = -1;
 480        return retval;
 481}
 482
 483/*
 484 * get and put functions for the table, exposed to modules.
 485 */
 486struct sysrq_key_op *__sysrq_get_key_op(int key)
 487{
 488        struct sysrq_key_op *op_p = NULL;
 489        int i;
 490
 491        i = sysrq_key_table_key2index(key);
 492        if (i != -1)
 493                op_p = sysrq_key_table[i];
 494
 495        return op_p;
 496}
 497
 498static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 499{
 500        int i = sysrq_key_table_key2index(key);
 501
 502        if (i != -1)
 503                sysrq_key_table[i] = op_p;
 504}
 505
 506void __handle_sysrq(int key, bool check_mask)
 507{
 508        struct sysrq_key_op *op_p;
 509        int orig_log_level;
 510        int i;
 511        unsigned long flags;
 512
 513        spin_lock_irqsave(&sysrq_key_table_lock, flags);
 514        /*
 515         * Raise the apparent loglevel to maximum so that the sysrq header
 516         * is shown to provide the user with positive feedback.  We do not
 517         * simply emit this at KERN_EMERG as that would change message
 518         * routing in the consumers of /proc/kmsg.
 519         */
 520        orig_log_level = console_loglevel;
 521        console_loglevel = 7;
 522        printk(KERN_INFO "SysRq : ");
 523
 524        op_p = __sysrq_get_key_op(key);
 525        if (op_p) {
 526                /*
 527                 * Should we check for enabled operations (/proc/sysrq-trigger
 528                 * should not) and is the invoked operation enabled?
 529                 */
 530                if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 531                        printk("%s\n", op_p->action_msg);
 532                        console_loglevel = orig_log_level;
 533                        op_p->handler(key);
 534                } else {
 535                        printk("This sysrq operation is disabled.\n");
 536                }
 537        } else {
 538                printk("HELP : ");
 539                /* Only print the help msg once per handler */
 540                for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 541                        if (sysrq_key_table[i]) {
 542                                int j;
 543
 544                                for (j = 0; sysrq_key_table[i] !=
 545                                                sysrq_key_table[j]; j++)
 546                                        ;
 547                                if (j != i)
 548                                        continue;
 549                                printk("%s ", sysrq_key_table[i]->help_msg);
 550                        }
 551                }
 552                printk("\n");
 553                console_loglevel = orig_log_level;
 554        }
 555        spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 556}
 557
 558void handle_sysrq(int key)
 559{
 560        if (sysrq_on())
 561                __handle_sysrq(key, true);
 562}
 563EXPORT_SYMBOL(handle_sysrq);
 564
 565#ifdef CONFIG_INPUT
 566
 567/* Simple translation table for the SysRq keys */
 568static const unsigned char sysrq_xlate[KEY_CNT] =
 569        "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 570        "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 571        "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 572        "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 573        "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 574        "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 575        "\r\000/";                                      /* 0x60 - 0x6f */
 576
 577struct sysrq_state {
 578        struct input_handle handle;
 579        struct work_struct reinject_work;
 580        unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 581        unsigned int alt;
 582        unsigned int alt_use;
 583        bool active;
 584        bool need_reinject;
 585        bool reinjecting;
 586
 587        /* reset sequence handling */
 588        bool reset_canceled;
 589        unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 590        int reset_seq_len;
 591        int reset_seq_cnt;
 592        int reset_seq_version;
 593        struct timer_list keyreset_timer;
 594};
 595
 596#define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 597static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 598static unsigned int sysrq_reset_seq_len;
 599static unsigned int sysrq_reset_seq_version = 1;
 600
 601static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 602{
 603        int i;
 604        unsigned short key;
 605
 606        state->reset_seq_cnt = 0;
 607
 608        for (i = 0; i < sysrq_reset_seq_len; i++) {
 609                key = sysrq_reset_seq[i];
 610
 611                if (key == KEY_RESERVED || key > KEY_MAX)
 612                        break;
 613
 614                __set_bit(key, state->reset_keybit);
 615                state->reset_seq_len++;
 616
 617                if (test_bit(key, state->key_down))
 618                        state->reset_seq_cnt++;
 619        }
 620
 621        /* Disable reset until old keys are not released */
 622        state->reset_canceled = state->reset_seq_cnt != 0;
 623
 624        state->reset_seq_version = sysrq_reset_seq_version;
 625}
 626
 627static void sysrq_do_reset(unsigned long dummy)
 628{
 629        __handle_sysrq(sysrq_xlate[KEY_B], false);
 630}
 631
 632static void sysrq_handle_reset_request(struct sysrq_state *state)
 633{
 634        if (sysrq_reset_downtime_ms)
 635                mod_timer(&state->keyreset_timer,
 636                        jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 637        else
 638                sysrq_do_reset(0);
 639}
 640
 641static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 642                                        unsigned int code, int value)
 643{
 644        if (!test_bit(code, state->reset_keybit)) {
 645                /*
 646                 * Pressing any key _not_ in reset sequence cancels
 647                 * the reset sequence.  Also cancelling the timer in
 648                 * case additional keys were pressed after a reset
 649                 * has been requested.
 650                 */
 651                if (value && state->reset_seq_cnt) {
 652                        state->reset_canceled = true;
 653                        del_timer(&state->keyreset_timer);
 654                }
 655        } else if (value == 0) {
 656                /*
 657                 * Key release - all keys in the reset sequence need
 658                 * to be pressed and held for the reset timeout
 659                 * to hold.
 660                 */
 661                del_timer(&state->keyreset_timer);
 662
 663                if (--state->reset_seq_cnt == 0)
 664                        state->reset_canceled = false;
 665        } else if (value == 1) {
 666                /* key press, not autorepeat */
 667                if (++state->reset_seq_cnt == state->reset_seq_len &&
 668                    !state->reset_canceled) {
 669                        sysrq_handle_reset_request(state);
 670                }
 671        }
 672}
 673
 674static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 675{
 676        struct sysrq_state *sysrq =
 677                        container_of(work, struct sysrq_state, reinject_work);
 678        struct input_handle *handle = &sysrq->handle;
 679        unsigned int alt_code = sysrq->alt_use;
 680
 681        if (sysrq->need_reinject) {
 682                /* we do not want the assignment to be reordered */
 683                sysrq->reinjecting = true;
 684                mb();
 685
 686                /* Simulate press and release of Alt + SysRq */
 687                input_inject_event(handle, EV_KEY, alt_code, 1);
 688                input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 689                input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 690
 691                input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 692                input_inject_event(handle, EV_KEY, alt_code, 0);
 693                input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 694
 695                mb();
 696                sysrq->reinjecting = false;
 697        }
 698}
 699
 700static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 701                                  unsigned int code, int value)
 702{
 703        bool was_active = sysrq->active;
 704        bool suppress;
 705
 706        switch (code) {
 707
 708        case KEY_LEFTALT:
 709        case KEY_RIGHTALT:
 710                if (!value) {
 711                        /* One of ALTs is being released */
 712                        if (sysrq->active && code == sysrq->alt_use)
 713                                sysrq->active = false;
 714
 715                        sysrq->alt = KEY_RESERVED;
 716
 717                } else if (value != 2) {
 718                        sysrq->alt = code;
 719                        sysrq->need_reinject = false;
 720                }
 721                break;
 722
 723        case KEY_SYSRQ:
 724                if (value == 1 && sysrq->alt != KEY_RESERVED) {
 725                        sysrq->active = true;
 726                        sysrq->alt_use = sysrq->alt;
 727                        /*
 728                         * If nothing else will be pressed we'll need
 729                         * to re-inject Alt-SysRq keysroke.
 730                         */
 731                        sysrq->need_reinject = true;
 732                }
 733
 734                /*
 735                 * Pretend that sysrq was never pressed at all. This
 736                 * is needed to properly handle KGDB which will try
 737                 * to release all keys after exiting debugger. If we
 738                 * do not clear key bit it KGDB will end up sending
 739                 * release events for Alt and SysRq, potentially
 740                 * triggering print screen function.
 741                 */
 742                if (sysrq->active)
 743                        clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 744
 745                break;
 746
 747        default:
 748                if (sysrq->active && value && value != 2) {
 749                        sysrq->need_reinject = false;
 750                        __handle_sysrq(sysrq_xlate[code], true);
 751                }
 752                break;
 753        }
 754
 755        suppress = sysrq->active;
 756
 757        if (!sysrq->active) {
 758
 759                /*
 760                 * See if reset sequence has changed since the last time.
 761                 */
 762                if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 763                        sysrq_parse_reset_sequence(sysrq);
 764
 765                /*
 766                 * If we are not suppressing key presses keep track of
 767                 * keyboard state so we can release keys that have been
 768                 * pressed before entering SysRq mode.
 769                 */
 770                if (value)
 771                        set_bit(code, sysrq->key_down);
 772                else
 773                        clear_bit(code, sysrq->key_down);
 774
 775                if (was_active)
 776                        schedule_work(&sysrq->reinject_work);
 777
 778                /* Check for reset sequence */
 779                sysrq_detect_reset_sequence(sysrq, code, value);
 780
 781        } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 782                /*
 783                 * Pass on release events for keys that was pressed before
 784                 * entering SysRq mode.
 785                 */
 786                suppress = false;
 787        }
 788
 789        return suppress;
 790}
 791
 792static bool sysrq_filter(struct input_handle *handle,
 793                         unsigned int type, unsigned int code, int value)
 794{
 795        struct sysrq_state *sysrq = handle->private;
 796        bool suppress;
 797
 798        /*
 799         * Do not filter anything if we are in the process of re-injecting
 800         * Alt+SysRq combination.
 801         */
 802        if (sysrq->reinjecting)
 803                return false;
 804
 805        switch (type) {
 806
 807        case EV_SYN:
 808                suppress = false;
 809                break;
 810
 811        case EV_KEY:
 812                suppress = sysrq_handle_keypress(sysrq, code, value);
 813                break;
 814
 815        default:
 816                suppress = sysrq->active;
 817                break;
 818        }
 819
 820        return suppress;
 821}
 822
 823static int sysrq_connect(struct input_handler *handler,
 824                         struct input_dev *dev,
 825                         const struct input_device_id *id)
 826{
 827        struct sysrq_state *sysrq;
 828        int error;
 829
 830        sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 831        if (!sysrq)
 832                return -ENOMEM;
 833
 834        INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 835
 836        sysrq->handle.dev = dev;
 837        sysrq->handle.handler = handler;
 838        sysrq->handle.name = "sysrq";
 839        sysrq->handle.private = sysrq;
 840        setup_timer(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 841
 842        error = input_register_handle(&sysrq->handle);
 843        if (error) {
 844                pr_err("Failed to register input sysrq handler, error %d\n",
 845                        error);
 846                goto err_free;
 847        }
 848
 849        error = input_open_device(&sysrq->handle);
 850        if (error) {
 851                pr_err("Failed to open input device, error %d\n", error);
 852                goto err_unregister;
 853        }
 854
 855        return 0;
 856
 857 err_unregister:
 858        input_unregister_handle(&sysrq->handle);
 859 err_free:
 860        kfree(sysrq);
 861        return error;
 862}
 863
 864static void sysrq_disconnect(struct input_handle *handle)
 865{
 866        struct sysrq_state *sysrq = handle->private;
 867
 868        input_close_device(handle);
 869        cancel_work_sync(&sysrq->reinject_work);
 870        del_timer_sync(&sysrq->keyreset_timer);
 871        input_unregister_handle(handle);
 872        kfree(sysrq);
 873}
 874
 875/*
 876 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 877 * keyboards have SysRq key predefined and so user may add it to keymap
 878 * later, but we expect all such keyboards to have left alt.
 879 */
 880static const struct input_device_id sysrq_ids[] = {
 881        {
 882                .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 883                                INPUT_DEVICE_ID_MATCH_KEYBIT,
 884                .evbit = { BIT_MASK(EV_KEY) },
 885                .keybit = { BIT_MASK(KEY_LEFTALT) },
 886        },
 887        { },
 888};
 889
 890static struct input_handler sysrq_handler = {
 891        .filter         = sysrq_filter,
 892        .connect        = sysrq_connect,
 893        .disconnect     = sysrq_disconnect,
 894        .name           = "sysrq",
 895        .id_table       = sysrq_ids,
 896};
 897
 898static bool sysrq_handler_registered;
 899
 900static inline void sysrq_register_handler(void)
 901{
 902        unsigned short key;
 903        int error;
 904        int i;
 905
 906        for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) {
 907                key = platform_sysrq_reset_seq[i];
 908                if (key == KEY_RESERVED || key > KEY_MAX)
 909                        break;
 910
 911                sysrq_reset_seq[sysrq_reset_seq_len++] = key;
 912        }
 913
 914        error = input_register_handler(&sysrq_handler);
 915        if (error)
 916                pr_err("Failed to register input handler, error %d", error);
 917        else
 918                sysrq_handler_registered = true;
 919}
 920
 921static inline void sysrq_unregister_handler(void)
 922{
 923        if (sysrq_handler_registered) {
 924                input_unregister_handler(&sysrq_handler);
 925                sysrq_handler_registered = false;
 926        }
 927}
 928
 929static int sysrq_reset_seq_param_set(const char *buffer,
 930                                     const struct kernel_param *kp)
 931{
 932        unsigned long val;
 933        int error;
 934
 935        error = strict_strtoul(buffer, 0, &val);
 936        if (error < 0)
 937                return error;
 938
 939        if (val > KEY_MAX)
 940                return -EINVAL;
 941
 942        *((unsigned short *)kp->arg) = val;
 943        sysrq_reset_seq_version++;
 944
 945        return 0;
 946}
 947
 948static struct kernel_param_ops param_ops_sysrq_reset_seq = {
 949        .get    = param_get_ushort,
 950        .set    = sysrq_reset_seq_param_set,
 951};
 952
 953#define param_check_sysrq_reset_seq(name, p)    \
 954        __param_check(name, p, unsigned short)
 955
 956module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
 957                         &sysrq_reset_seq_len, 0644);
 958
 959module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
 960
 961#else
 962
 963static inline void sysrq_register_handler(void)
 964{
 965}
 966
 967static inline void sysrq_unregister_handler(void)
 968{
 969}
 970
 971#endif /* CONFIG_INPUT */
 972
 973int sysrq_toggle_support(int enable_mask)
 974{
 975        bool was_enabled = sysrq_on();
 976
 977        sysrq_enabled = enable_mask;
 978
 979        if (was_enabled != sysrq_on()) {
 980                if (sysrq_on())
 981                        sysrq_register_handler();
 982                else
 983                        sysrq_unregister_handler();
 984        }
 985
 986        return 0;
 987}
 988
 989static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
 990                                struct sysrq_key_op *remove_op_p)
 991{
 992        int retval;
 993        unsigned long flags;
 994
 995        spin_lock_irqsave(&sysrq_key_table_lock, flags);
 996        if (__sysrq_get_key_op(key) == remove_op_p) {
 997                __sysrq_put_key_op(key, insert_op_p);
 998                retval = 0;
 999        } else {
1000                retval = -1;
1001        }
1002        spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
1003        return retval;
1004}
1005
1006int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1007{
1008        return __sysrq_swap_key_ops(key, op_p, NULL);
1009}
1010EXPORT_SYMBOL(register_sysrq_key);
1011
1012int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1013{
1014        return __sysrq_swap_key_ops(key, NULL, op_p);
1015}
1016EXPORT_SYMBOL(unregister_sysrq_key);
1017
1018#ifdef CONFIG_PROC_FS
1019/*
1020 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1021 */
1022static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1023                                   size_t count, loff_t *ppos)
1024{
1025        if (count) {
1026                char c;
1027
1028                if (get_user(c, buf))
1029                        return -EFAULT;
1030                __handle_sysrq(c, false);
1031        }
1032
1033        return count;
1034}
1035
1036static const struct file_operations proc_sysrq_trigger_operations = {
1037        .write          = write_sysrq_trigger,
1038        .llseek         = noop_llseek,
1039};
1040
1041static void sysrq_init_procfs(void)
1042{
1043        if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1044                         &proc_sysrq_trigger_operations))
1045                pr_err("Failed to register proc interface\n");
1046}
1047
1048#else
1049
1050static inline void sysrq_init_procfs(void)
1051{
1052}
1053
1054#endif /* CONFIG_PROC_FS */
1055
1056static int __init sysrq_init(void)
1057{
1058        sysrq_init_procfs();
1059
1060        if (sysrq_on())
1061                sysrq_register_handler();
1062
1063        return 0;
1064}
1065module_init(sysrq_init);
1066
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