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