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