linux/drivers/tty/sysrq.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *      Linux Magic System Request Key Hacks
   4 *
   5 *      (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   6 *      based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
   7 *
   8 *      (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
   9 *      overhauled to use key registration
  10 *      based upon discusions in irc://irc.openprojects.net/#kernelnewbies
  11 *
  12 *      Copyright (c) 2010 Dmitry Torokhov
  13 *      Input handler conversion
  14 */
  15
  16#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18#include <linux/sched/signal.h>
  19#include <linux/sched/rt.h>
  20#include <linux/sched/debug.h>
  21#include <linux/sched/task.h>
  22#include <linux/interrupt.h>
  23#include <linux/mm.h>
  24#include <linux/fs.h>
  25#include <linux/mount.h>
  26#include <linux/kdev_t.h>
  27#include <linux/major.h>
  28#include <linux/reboot.h>
  29#include <linux/sysrq.h>
  30#include <linux/kbd_kern.h>
  31#include <linux/proc_fs.h>
  32#include <linux/nmi.h>
  33#include <linux/quotaops.h>
  34#include <linux/perf_event.h>
  35#include <linux/kernel.h>
  36#include <linux/module.h>
  37#include <linux/suspend.h>
  38#include <linux/writeback.h>
  39#include <linux/swap.h>
  40#include <linux/spinlock.h>
  41#include <linux/vt_kern.h>
  42#include <linux/workqueue.h>
  43#include <linux/hrtimer.h>
  44#include <linux/oom.h>
  45#include <linux/slab.h>
  46#include <linux/input.h>
  47#include <linux/uaccess.h>
  48#include <linux/moduleparam.h>
  49#include <linux/jiffies.h>
  50#include <linux/syscalls.h>
  51#include <linux/of.h>
  52#include <linux/rcupdate.h>
  53
  54#include <asm/ptrace.h>
  55#include <asm/irq_regs.h>
  56
  57/* Whether we react on sysrq keys or just ignore them */
  58static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
  59static bool __read_mostly sysrq_always_enabled;
  60
  61static bool sysrq_on(void)
  62{
  63        return sysrq_enabled || sysrq_always_enabled;
  64}
  65
  66/*
  67 * A value of 1 means 'all', other nonzero values are an op mask:
  68 */
  69static bool sysrq_on_mask(int mask)
  70{
  71        return sysrq_always_enabled ||
  72               sysrq_enabled == 1 ||
  73               (sysrq_enabled & mask);
  74}
  75
  76static int __init sysrq_always_enabled_setup(char *str)
  77{
  78        sysrq_always_enabled = true;
  79        pr_info("sysrq always enabled.\n");
  80
  81        return 1;
  82}
  83
  84__setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  85
  86
  87static void sysrq_handle_loglevel(int key)
  88{
  89        int i;
  90
  91        i = key - '0';
  92        console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
  93        pr_info("Loglevel set to %d\n", i);
  94        console_loglevel = i;
  95}
  96static struct sysrq_key_op sysrq_loglevel_op = {
  97        .handler        = sysrq_handle_loglevel,
  98        .help_msg       = "loglevel(0-9)",
  99        .action_msg     = "Changing Loglevel",
 100        .enable_mask    = SYSRQ_ENABLE_LOG,
 101};
 102
 103#ifdef CONFIG_VT
 104static void sysrq_handle_SAK(int key)
 105{
 106        struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 107        schedule_work(SAK_work);
 108}
 109static struct sysrq_key_op sysrq_SAK_op = {
 110        .handler        = sysrq_handle_SAK,
 111        .help_msg       = "sak(k)",
 112        .action_msg     = "SAK",
 113        .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 114};
 115#else
 116#define sysrq_SAK_op (*(struct sysrq_key_op *)NULL)
 117#endif
 118
 119#ifdef CONFIG_VT
 120static void sysrq_handle_unraw(int key)
 121{
 122        vt_reset_unicode(fg_console);
 123}
 124
 125static struct sysrq_key_op sysrq_unraw_op = {
 126        .handler        = sysrq_handle_unraw,
 127        .help_msg       = "unraw(r)",
 128        .action_msg     = "Keyboard mode set to system default",
 129        .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 130};
 131#else
 132#define sysrq_unraw_op (*(struct sysrq_key_op *)NULL)
 133#endif /* CONFIG_VT */
 134
 135static void sysrq_handle_crash(int key)
 136{
 137        /* release the RCU read lock before crashing */
 138        rcu_read_unlock();
 139
 140        panic("sysrq triggered crash\n");
 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_RAW_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        raw_spin_lock_irqsave(&show_lock, flags);
 222        pr_info("CPU%d:\n", smp_processor_id());
 223        show_stack(NULL, NULL);
 224        raw_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 = NULL;
 243
 244                if (in_irq())
 245                        regs = get_irq_regs();
 246                if (regs) {
 247                        pr_info("CPU%d:\n", smp_processor_id());
 248                        show_regs(regs);
 249                }
 250                schedule_work(&sysrq_showallcpus);
 251        }
 252}
 253
 254static struct sysrq_key_op sysrq_showallcpus_op = {
 255        .handler        = sysrq_handle_showallcpus,
 256        .help_msg       = "show-backtrace-all-active-cpus(l)",
 257        .action_msg     = "Show backtrace of all active CPUs",
 258        .enable_mask    = SYSRQ_ENABLE_DUMP,
 259};
 260#endif
 261
 262static void sysrq_handle_showregs(int key)
 263{
 264        struct pt_regs *regs = NULL;
 265
 266        if (in_irq())
 267                regs = get_irq_regs();
 268        if (regs)
 269                show_regs(regs);
 270        perf_event_print_debug();
 271}
 272static struct sysrq_key_op sysrq_showregs_op = {
 273        .handler        = sysrq_handle_showregs,
 274        .help_msg       = "show-registers(p)",
 275        .action_msg     = "Show Regs",
 276        .enable_mask    = SYSRQ_ENABLE_DUMP,
 277};
 278
 279static void sysrq_handle_showstate(int key)
 280{
 281        show_state();
 282        show_workqueue_state();
 283}
 284static struct sysrq_key_op sysrq_showstate_op = {
 285        .handler        = sysrq_handle_showstate,
 286        .help_msg       = "show-task-states(t)",
 287        .action_msg     = "Show State",
 288        .enable_mask    = SYSRQ_ENABLE_DUMP,
 289};
 290
 291static void sysrq_handle_showstate_blocked(int key)
 292{
 293        show_state_filter(TASK_UNINTERRUPTIBLE);
 294}
 295static struct sysrq_key_op sysrq_showstate_blocked_op = {
 296        .handler        = sysrq_handle_showstate_blocked,
 297        .help_msg       = "show-blocked-tasks(w)",
 298        .action_msg     = "Show Blocked State",
 299        .enable_mask    = SYSRQ_ENABLE_DUMP,
 300};
 301
 302#ifdef CONFIG_TRACING
 303#include <linux/ftrace.h>
 304
 305static void sysrq_ftrace_dump(int key)
 306{
 307        ftrace_dump(DUMP_ALL);
 308}
 309static struct sysrq_key_op sysrq_ftrace_dump_op = {
 310        .handler        = sysrq_ftrace_dump,
 311        .help_msg       = "dump-ftrace-buffer(z)",
 312        .action_msg     = "Dump ftrace buffer",
 313        .enable_mask    = SYSRQ_ENABLE_DUMP,
 314};
 315#else
 316#define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL)
 317#endif
 318
 319static void sysrq_handle_showmem(int key)
 320{
 321        show_mem(0, NULL);
 322}
 323static struct sysrq_key_op sysrq_showmem_op = {
 324        .handler        = sysrq_handle_showmem,
 325        .help_msg       = "show-memory-usage(m)",
 326        .action_msg     = "Show Memory",
 327        .enable_mask    = SYSRQ_ENABLE_DUMP,
 328};
 329
 330/*
 331 * Signal sysrq helper function.  Sends a signal to all user processes.
 332 */
 333static void send_sig_all(int sig)
 334{
 335        struct task_struct *p;
 336
 337        read_lock(&tasklist_lock);
 338        for_each_process(p) {
 339                if (p->flags & PF_KTHREAD)
 340                        continue;
 341                if (is_global_init(p))
 342                        continue;
 343
 344                do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
 345        }
 346        read_unlock(&tasklist_lock);
 347}
 348
 349static void sysrq_handle_term(int key)
 350{
 351        send_sig_all(SIGTERM);
 352        console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 353}
 354static struct sysrq_key_op sysrq_term_op = {
 355        .handler        = sysrq_handle_term,
 356        .help_msg       = "terminate-all-tasks(e)",
 357        .action_msg     = "Terminate All Tasks",
 358        .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 359};
 360
 361static void moom_callback(struct work_struct *ignored)
 362{
 363        const gfp_t gfp_mask = GFP_KERNEL;
 364        struct oom_control oc = {
 365                .zonelist = node_zonelist(first_memory_node, gfp_mask),
 366                .nodemask = NULL,
 367                .memcg = NULL,
 368                .gfp_mask = gfp_mask,
 369                .order = -1,
 370        };
 371
 372        mutex_lock(&oom_lock);
 373        if (!out_of_memory(&oc))
 374                pr_info("OOM request ignored. No task eligible\n");
 375        mutex_unlock(&oom_lock);
 376}
 377
 378static DECLARE_WORK(moom_work, moom_callback);
 379
 380static void sysrq_handle_moom(int key)
 381{
 382        schedule_work(&moom_work);
 383}
 384static struct sysrq_key_op sysrq_moom_op = {
 385        .handler        = sysrq_handle_moom,
 386        .help_msg       = "memory-full-oom-kill(f)",
 387        .action_msg     = "Manual OOM execution",
 388        .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 389};
 390
 391#ifdef CONFIG_BLOCK
 392static void sysrq_handle_thaw(int key)
 393{
 394        emergency_thaw_all();
 395}
 396static struct sysrq_key_op sysrq_thaw_op = {
 397        .handler        = sysrq_handle_thaw,
 398        .help_msg       = "thaw-filesystems(j)",
 399        .action_msg     = "Emergency Thaw of all frozen filesystems",
 400        .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 401};
 402#endif
 403
 404static void sysrq_handle_kill(int key)
 405{
 406        send_sig_all(SIGKILL);
 407        console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 408}
 409static struct sysrq_key_op sysrq_kill_op = {
 410        .handler        = sysrq_handle_kill,
 411        .help_msg       = "kill-all-tasks(i)",
 412        .action_msg     = "Kill All Tasks",
 413        .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 414};
 415
 416static void sysrq_handle_unrt(int key)
 417{
 418        normalize_rt_tasks();
 419}
 420static struct sysrq_key_op sysrq_unrt_op = {
 421        .handler        = sysrq_handle_unrt,
 422        .help_msg       = "nice-all-RT-tasks(n)",
 423        .action_msg     = "Nice All RT Tasks",
 424        .enable_mask    = SYSRQ_ENABLE_RTNICE,
 425};
 426
 427/* Key Operations table and lock */
 428static DEFINE_SPINLOCK(sysrq_key_table_lock);
 429
 430static struct sysrq_key_op *sysrq_key_table[36] = {
 431        &sysrq_loglevel_op,             /* 0 */
 432        &sysrq_loglevel_op,             /* 1 */
 433        &sysrq_loglevel_op,             /* 2 */
 434        &sysrq_loglevel_op,             /* 3 */
 435        &sysrq_loglevel_op,             /* 4 */
 436        &sysrq_loglevel_op,             /* 5 */
 437        &sysrq_loglevel_op,             /* 6 */
 438        &sysrq_loglevel_op,             /* 7 */
 439        &sysrq_loglevel_op,             /* 8 */
 440        &sysrq_loglevel_op,             /* 9 */
 441
 442        /*
 443         * a: Don't use for system provided sysrqs, it is handled specially on
 444         * sparc and will never arrive.
 445         */
 446        NULL,                           /* a */
 447        &sysrq_reboot_op,               /* b */
 448        &sysrq_crash_op,                /* c */
 449        &sysrq_showlocks_op,            /* d */
 450        &sysrq_term_op,                 /* e */
 451        &sysrq_moom_op,                 /* f */
 452        /* g: May be registered for the kernel debugger */
 453        NULL,                           /* g */
 454        NULL,                           /* h - reserved for help */
 455        &sysrq_kill_op,                 /* i */
 456#ifdef CONFIG_BLOCK
 457        &sysrq_thaw_op,                 /* j */
 458#else
 459        NULL,                           /* j */
 460#endif
 461        &sysrq_SAK_op,                  /* k */
 462#ifdef CONFIG_SMP
 463        &sysrq_showallcpus_op,          /* l */
 464#else
 465        NULL,                           /* l */
 466#endif
 467        &sysrq_showmem_op,              /* m */
 468        &sysrq_unrt_op,                 /* n */
 469        /* o: This will often be registered as 'Off' at init time */
 470        NULL,                           /* o */
 471        &sysrq_showregs_op,             /* p */
 472        &sysrq_show_timers_op,          /* q */
 473        &sysrq_unraw_op,                /* r */
 474        &sysrq_sync_op,                 /* s */
 475        &sysrq_showstate_op,            /* t */
 476        &sysrq_mountro_op,              /* u */
 477        /* v: May be registered for frame buffer console restore */
 478        NULL,                           /* v */
 479        &sysrq_showstate_blocked_op,    /* w */
 480        /* x: May be registered on mips for TLB dump */
 481        /* x: May be registered on ppc/powerpc for xmon */
 482        /* x: May be registered on sparc64 for global PMU dump */
 483        NULL,                           /* x */
 484        /* y: May be registered on sparc64 for global register dump */
 485        NULL,                           /* y */
 486        &sysrq_ftrace_dump_op,          /* z */
 487};
 488
 489/* key2index calculation, -1 on invalid index */
 490static int sysrq_key_table_key2index(int key)
 491{
 492        int retval;
 493
 494        if ((key >= '0') && (key <= '9'))
 495                retval = key - '0';
 496        else if ((key >= 'a') && (key <= 'z'))
 497                retval = key + 10 - 'a';
 498        else
 499                retval = -1;
 500        return retval;
 501}
 502
 503/*
 504 * get and put functions for the table, exposed to modules.
 505 */
 506struct sysrq_key_op *__sysrq_get_key_op(int key)
 507{
 508        struct sysrq_key_op *op_p = NULL;
 509        int i;
 510
 511        i = sysrq_key_table_key2index(key);
 512        if (i != -1)
 513                op_p = sysrq_key_table[i];
 514
 515        return op_p;
 516}
 517
 518static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 519{
 520        int i = sysrq_key_table_key2index(key);
 521
 522        if (i != -1)
 523                sysrq_key_table[i] = op_p;
 524}
 525
 526void __handle_sysrq(int key, bool check_mask)
 527{
 528        struct sysrq_key_op *op_p;
 529        int orig_log_level;
 530        int orig_suppress_printk;
 531        int i;
 532
 533        orig_suppress_printk = suppress_printk;
 534        suppress_printk = 0;
 535
 536        rcu_sysrq_start();
 537        rcu_read_lock();
 538        /*
 539         * Raise the apparent loglevel to maximum so that the sysrq header
 540         * is shown to provide the user with positive feedback.  We do not
 541         * simply emit this at KERN_EMERG as that would change message
 542         * routing in the consumers of /proc/kmsg.
 543         */
 544        orig_log_level = console_loglevel;
 545        console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 546
 547        op_p = __sysrq_get_key_op(key);
 548        if (op_p) {
 549                /*
 550                 * Should we check for enabled operations (/proc/sysrq-trigger
 551                 * should not) and is the invoked operation enabled?
 552                 */
 553                if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 554                        pr_info("%s\n", op_p->action_msg);
 555                        console_loglevel = orig_log_level;
 556                        op_p->handler(key);
 557                } else {
 558                        pr_info("This sysrq operation is disabled.\n");
 559                        console_loglevel = orig_log_level;
 560                }
 561        } else {
 562                pr_info("HELP : ");
 563                /* Only print the help msg once per handler */
 564                for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 565                        if (sysrq_key_table[i]) {
 566                                int j;
 567
 568                                for (j = 0; sysrq_key_table[i] !=
 569                                                sysrq_key_table[j]; j++)
 570                                        ;
 571                                if (j != i)
 572                                        continue;
 573                                pr_cont("%s ", sysrq_key_table[i]->help_msg);
 574                        }
 575                }
 576                pr_cont("\n");
 577                console_loglevel = orig_log_level;
 578        }
 579        rcu_read_unlock();
 580        rcu_sysrq_end();
 581
 582        suppress_printk = orig_suppress_printk;
 583}
 584
 585void handle_sysrq(int key)
 586{
 587        if (sysrq_on())
 588                __handle_sysrq(key, true);
 589}
 590EXPORT_SYMBOL(handle_sysrq);
 591
 592#ifdef CONFIG_INPUT
 593static int sysrq_reset_downtime_ms;
 594
 595/* Simple translation table for the SysRq keys */
 596static const unsigned char sysrq_xlate[KEY_CNT] =
 597        "\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 598        "qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 599        "dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 600        "bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 601        "\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 602        "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 603        "\r\000/";                                      /* 0x60 - 0x6f */
 604
 605struct sysrq_state {
 606        struct input_handle handle;
 607        struct work_struct reinject_work;
 608        unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 609        unsigned int alt;
 610        unsigned int alt_use;
 611        bool active;
 612        bool need_reinject;
 613        bool reinjecting;
 614
 615        /* reset sequence handling */
 616        bool reset_canceled;
 617        bool reset_requested;
 618        unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 619        int reset_seq_len;
 620        int reset_seq_cnt;
 621        int reset_seq_version;
 622        struct timer_list keyreset_timer;
 623};
 624
 625#define SYSRQ_KEY_RESET_MAX     20 /* Should be plenty */
 626static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 627static unsigned int sysrq_reset_seq_len;
 628static unsigned int sysrq_reset_seq_version = 1;
 629
 630static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 631{
 632        int i;
 633        unsigned short key;
 634
 635        state->reset_seq_cnt = 0;
 636
 637        for (i = 0; i < sysrq_reset_seq_len; i++) {
 638                key = sysrq_reset_seq[i];
 639
 640                if (key == KEY_RESERVED || key > KEY_MAX)
 641                        break;
 642
 643                __set_bit(key, state->reset_keybit);
 644                state->reset_seq_len++;
 645
 646                if (test_bit(key, state->key_down))
 647                        state->reset_seq_cnt++;
 648        }
 649
 650        /* Disable reset until old keys are not released */
 651        state->reset_canceled = state->reset_seq_cnt != 0;
 652
 653        state->reset_seq_version = sysrq_reset_seq_version;
 654}
 655
 656static void sysrq_do_reset(struct timer_list *t)
 657{
 658        struct sysrq_state *state = from_timer(state, t, keyreset_timer);
 659
 660        state->reset_requested = true;
 661
 662        orderly_reboot();
 663}
 664
 665static void sysrq_handle_reset_request(struct sysrq_state *state)
 666{
 667        if (state->reset_requested)
 668                __handle_sysrq(sysrq_xlate[KEY_B], false);
 669
 670        if (sysrq_reset_downtime_ms)
 671                mod_timer(&state->keyreset_timer,
 672                        jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 673        else
 674                sysrq_do_reset(&state->keyreset_timer);
 675}
 676
 677static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 678                                        unsigned int code, int value)
 679{
 680        if (!test_bit(code, state->reset_keybit)) {
 681                /*
 682                 * Pressing any key _not_ in reset sequence cancels
 683                 * the reset sequence.  Also cancelling the timer in
 684                 * case additional keys were pressed after a reset
 685                 * has been requested.
 686                 */
 687                if (value && state->reset_seq_cnt) {
 688                        state->reset_canceled = true;
 689                        del_timer(&state->keyreset_timer);
 690                }
 691        } else if (value == 0) {
 692                /*
 693                 * Key release - all keys in the reset sequence need
 694                 * to be pressed and held for the reset timeout
 695                 * to hold.
 696                 */
 697                del_timer(&state->keyreset_timer);
 698
 699                if (--state->reset_seq_cnt == 0)
 700                        state->reset_canceled = false;
 701        } else if (value == 1) {
 702                /* key press, not autorepeat */
 703                if (++state->reset_seq_cnt == state->reset_seq_len &&
 704                    !state->reset_canceled) {
 705                        sysrq_handle_reset_request(state);
 706                }
 707        }
 708}
 709
 710#ifdef CONFIG_OF
 711static void sysrq_of_get_keyreset_config(void)
 712{
 713        u32 key;
 714        struct device_node *np;
 715        struct property *prop;
 716        const __be32 *p;
 717
 718        np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 719        if (!np) {
 720                pr_debug("No sysrq node found");
 721                return;
 722        }
 723
 724        /* Reset in case a __weak definition was present */
 725        sysrq_reset_seq_len = 0;
 726
 727        of_property_for_each_u32(np, "keyset", prop, p, key) {
 728                if (key == KEY_RESERVED || key > KEY_MAX ||
 729                    sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 730                        break;
 731
 732                sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 733        }
 734
 735        /* Get reset timeout if any. */
 736        of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 737
 738        of_node_put(np);
 739}
 740#else
 741static void sysrq_of_get_keyreset_config(void)
 742{
 743}
 744#endif
 745
 746static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 747{
 748        struct sysrq_state *sysrq =
 749                        container_of(work, struct sysrq_state, reinject_work);
 750        struct input_handle *handle = &sysrq->handle;
 751        unsigned int alt_code = sysrq->alt_use;
 752
 753        if (sysrq->need_reinject) {
 754                /* we do not want the assignment to be reordered */
 755                sysrq->reinjecting = true;
 756                mb();
 757
 758                /* Simulate press and release of Alt + SysRq */
 759                input_inject_event(handle, EV_KEY, alt_code, 1);
 760                input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 761                input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 762
 763                input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 764                input_inject_event(handle, EV_KEY, alt_code, 0);
 765                input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 766
 767                mb();
 768                sysrq->reinjecting = false;
 769        }
 770}
 771
 772static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 773                                  unsigned int code, int value)
 774{
 775        bool was_active = sysrq->active;
 776        bool suppress;
 777
 778        switch (code) {
 779
 780        case KEY_LEFTALT:
 781        case KEY_RIGHTALT:
 782                if (!value) {
 783                        /* One of ALTs is being released */
 784                        if (sysrq->active && code == sysrq->alt_use)
 785                                sysrq->active = false;
 786
 787                        sysrq->alt = KEY_RESERVED;
 788
 789                } else if (value != 2) {
 790                        sysrq->alt = code;
 791                        sysrq->need_reinject = false;
 792                }
 793                break;
 794
 795        case KEY_SYSRQ:
 796                if (value == 1 && sysrq->alt != KEY_RESERVED) {
 797                        sysrq->active = true;
 798                        sysrq->alt_use = sysrq->alt;
 799                        /*
 800                         * If nothing else will be pressed we'll need
 801                         * to re-inject Alt-SysRq keysroke.
 802                         */
 803                        sysrq->need_reinject = true;
 804                }
 805
 806                /*
 807                 * Pretend that sysrq was never pressed at all. This
 808                 * is needed to properly handle KGDB which will try
 809                 * to release all keys after exiting debugger. If we
 810                 * do not clear key bit it KGDB will end up sending
 811                 * release events for Alt and SysRq, potentially
 812                 * triggering print screen function.
 813                 */
 814                if (sysrq->active)
 815                        clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 816
 817                break;
 818
 819        default:
 820                if (sysrq->active && value && value != 2) {
 821                        sysrq->need_reinject = false;
 822                        __handle_sysrq(sysrq_xlate[code], true);
 823                }
 824                break;
 825        }
 826
 827        suppress = sysrq->active;
 828
 829        if (!sysrq->active) {
 830
 831                /*
 832                 * See if reset sequence has changed since the last time.
 833                 */
 834                if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 835                        sysrq_parse_reset_sequence(sysrq);
 836
 837                /*
 838                 * If we are not suppressing key presses keep track of
 839                 * keyboard state so we can release keys that have been
 840                 * pressed before entering SysRq mode.
 841                 */
 842                if (value)
 843                        set_bit(code, sysrq->key_down);
 844                else
 845                        clear_bit(code, sysrq->key_down);
 846
 847                if (was_active)
 848                        schedule_work(&sysrq->reinject_work);
 849
 850                /* Check for reset sequence */
 851                sysrq_detect_reset_sequence(sysrq, code, value);
 852
 853        } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 854                /*
 855                 * Pass on release events for keys that was pressed before
 856                 * entering SysRq mode.
 857                 */
 858                suppress = false;
 859        }
 860
 861        return suppress;
 862}
 863
 864static bool sysrq_filter(struct input_handle *handle,
 865                         unsigned int type, unsigned int code, int value)
 866{
 867        struct sysrq_state *sysrq = handle->private;
 868        bool suppress;
 869
 870        /*
 871         * Do not filter anything if we are in the process of re-injecting
 872         * Alt+SysRq combination.
 873         */
 874        if (sysrq->reinjecting)
 875                return false;
 876
 877        switch (type) {
 878
 879        case EV_SYN:
 880                suppress = false;
 881                break;
 882
 883        case EV_KEY:
 884                suppress = sysrq_handle_keypress(sysrq, code, value);
 885                break;
 886
 887        default:
 888                suppress = sysrq->active;
 889                break;
 890        }
 891
 892        return suppress;
 893}
 894
 895static int sysrq_connect(struct input_handler *handler,
 896                         struct input_dev *dev,
 897                         const struct input_device_id *id)
 898{
 899        struct sysrq_state *sysrq;
 900        int error;
 901
 902        sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 903        if (!sysrq)
 904                return -ENOMEM;
 905
 906        INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 907
 908        sysrq->handle.dev = dev;
 909        sysrq->handle.handler = handler;
 910        sysrq->handle.name = "sysrq";
 911        sysrq->handle.private = sysrq;
 912        timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 913
 914        error = input_register_handle(&sysrq->handle);
 915        if (error) {
 916                pr_err("Failed to register input sysrq handler, error %d\n",
 917                        error);
 918                goto err_free;
 919        }
 920
 921        error = input_open_device(&sysrq->handle);
 922        if (error) {
 923                pr_err("Failed to open input device, error %d\n", error);
 924                goto err_unregister;
 925        }
 926
 927        return 0;
 928
 929 err_unregister:
 930        input_unregister_handle(&sysrq->handle);
 931 err_free:
 932        kfree(sysrq);
 933        return error;
 934}
 935
 936static void sysrq_disconnect(struct input_handle *handle)
 937{
 938        struct sysrq_state *sysrq = handle->private;
 939
 940        input_close_device(handle);
 941        cancel_work_sync(&sysrq->reinject_work);
 942        del_timer_sync(&sysrq->keyreset_timer);
 943        input_unregister_handle(handle);
 944        kfree(sysrq);
 945}
 946
 947/*
 948 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
 949 * keyboards have SysRq key predefined and so user may add it to keymap
 950 * later, but we expect all such keyboards to have left alt.
 951 */
 952static const struct input_device_id sysrq_ids[] = {
 953        {
 954                .flags = INPUT_DEVICE_ID_MATCH_EVBIT |
 955                                INPUT_DEVICE_ID_MATCH_KEYBIT,
 956                .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
 957                .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
 958        },
 959        { },
 960};
 961
 962static struct input_handler sysrq_handler = {
 963        .filter         = sysrq_filter,
 964        .connect        = sysrq_connect,
 965        .disconnect     = sysrq_disconnect,
 966        .name           = "sysrq",
 967        .id_table       = sysrq_ids,
 968};
 969
 970static bool sysrq_handler_registered;
 971
 972static inline void sysrq_register_handler(void)
 973{
 974        int error;
 975
 976        sysrq_of_get_keyreset_config();
 977
 978        error = input_register_handler(&sysrq_handler);
 979        if (error)
 980                pr_err("Failed to register input handler, error %d", error);
 981        else
 982                sysrq_handler_registered = true;
 983}
 984
 985static inline void sysrq_unregister_handler(void)
 986{
 987        if (sysrq_handler_registered) {
 988                input_unregister_handler(&sysrq_handler);
 989                sysrq_handler_registered = false;
 990        }
 991}
 992
 993static int sysrq_reset_seq_param_set(const char *buffer,
 994                                     const struct kernel_param *kp)
 995{
 996        unsigned long val;
 997        int error;
 998
 999        error = kstrtoul(buffer, 0, &val);
1000        if (error < 0)
1001                return error;
1002
1003        if (val > KEY_MAX)
1004                return -EINVAL;
1005
1006        *((unsigned short *)kp->arg) = val;
1007        sysrq_reset_seq_version++;
1008
1009        return 0;
1010}
1011
1012static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1013        .get    = param_get_ushort,
1014        .set    = sysrq_reset_seq_param_set,
1015};
1016
1017#define param_check_sysrq_reset_seq(name, p)    \
1018        __param_check(name, p, unsigned short)
1019
1020/*
1021 * not really modular, but the easiest way to keep compat with existing
1022 * bootargs behaviour is to continue using module_param here.
1023 */
1024module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1025                         &sysrq_reset_seq_len, 0644);
1026
1027module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1028
1029#else
1030
1031static inline void sysrq_register_handler(void)
1032{
1033}
1034
1035static inline void sysrq_unregister_handler(void)
1036{
1037}
1038
1039#endif /* CONFIG_INPUT */
1040
1041int sysrq_toggle_support(int enable_mask)
1042{
1043        bool was_enabled = sysrq_on();
1044
1045        sysrq_enabled = enable_mask;
1046
1047        if (was_enabled != sysrq_on()) {
1048                if (sysrq_on())
1049                        sysrq_register_handler();
1050                else
1051                        sysrq_unregister_handler();
1052        }
1053
1054        return 0;
1055}
1056
1057static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
1058                                struct sysrq_key_op *remove_op_p)
1059{
1060        int retval;
1061
1062        spin_lock(&sysrq_key_table_lock);
1063        if (__sysrq_get_key_op(key) == remove_op_p) {
1064                __sysrq_put_key_op(key, insert_op_p);
1065                retval = 0;
1066        } else {
1067                retval = -1;
1068        }
1069        spin_unlock(&sysrq_key_table_lock);
1070
1071        /*
1072         * A concurrent __handle_sysrq either got the old op or the new op.
1073         * Wait for it to go away before returning, so the code for an old
1074         * op is not freed (eg. on module unload) while it is in use.
1075         */
1076        synchronize_rcu();
1077
1078        return retval;
1079}
1080
1081int register_sysrq_key(int key, struct sysrq_key_op *op_p)
1082{
1083        return __sysrq_swap_key_ops(key, op_p, NULL);
1084}
1085EXPORT_SYMBOL(register_sysrq_key);
1086
1087int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
1088{
1089        return __sysrq_swap_key_ops(key, NULL, op_p);
1090}
1091EXPORT_SYMBOL(unregister_sysrq_key);
1092
1093#ifdef CONFIG_PROC_FS
1094/*
1095 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1096 */
1097static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1098                                   size_t count, loff_t *ppos)
1099{
1100        if (count) {
1101                char c;
1102
1103                if (get_user(c, buf))
1104                        return -EFAULT;
1105                __handle_sysrq(c, false);
1106        }
1107
1108        return count;
1109}
1110
1111static const struct file_operations proc_sysrq_trigger_operations = {
1112        .write          = write_sysrq_trigger,
1113        .llseek         = noop_llseek,
1114};
1115
1116static void sysrq_init_procfs(void)
1117{
1118        if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1119                         &proc_sysrq_trigger_operations))
1120                pr_err("Failed to register proc interface\n");
1121}
1122
1123#else
1124
1125static inline void sysrq_init_procfs(void)
1126{
1127}
1128
1129#endif /* CONFIG_PROC_FS */
1130
1131static int __init sysrq_init(void)
1132{
1133        sysrq_init_procfs();
1134
1135        if (sysrq_on())
1136                sysrq_register_handler();
1137
1138        return 0;
1139}
1140device_initcall(sysrq_init);
1141