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