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