sysrq.c

   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/ctype.h>
  23#include <linux/interrupt.h>
  24#include <linux/mm.h>
  25#include <linux/fs.h>
  26#include <linux/mount.h>
  27#include <linux/kdev_t.h>
  28#include <linux/major.h>
  29#include <linux/reboot.h>
  30#include <linux/sysrq.h>
  31#include <linux/kbd_kern.h>
  32#include <linux/proc_fs.h>
  33#include <linux/nmi.h>
  34#include <linux/quotaops.h>
  35#include <linux/perf_event.h>
  36#include <linux/kernel.h>
  37#include <linux/module.h>
  38#include <linux/suspend.h>
  39#include <linux/writeback.h>
  40#include <linux/swap.h>
  41#include <linux/spinlock.h>
  42#include <linux/vt_kern.h>
  43#include <linux/workqueue.h>
  44#include <linux/hrtimer.h>
  45#include <linux/oom.h>
  46#include <linux/slab.h>
  47#include <linux/input.h>
  48#include <linux/uaccess.h>
  49#include <linux/moduleparam.h>
  50#include <linux/jiffies.h>
  51#include <linux/syscalls.h>
  52#include <linux/of.h>
  53#include <linux/rcupdate.h>
  54
  55#include <asm/ptrace.h>
  56#include <asm/irq_regs.h>
  57
  58/* Whether we react on sysrq keys or just ignore them */
  59static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE;
  60static bool __read_mostly sysrq_always_enabled;
  61
  62static bool sysrq_on(void)
  63{
  64	return sysrq_enabled || sysrq_always_enabled;
  65}
  66
  67/**
  68 * sysrq_mask - Getter for sysrq_enabled mask.
  69 *
  70 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise.
  71 */
  72int sysrq_mask(void)
  73{
  74	if (sysrq_always_enabled)
  75		return 1;
  76	return sysrq_enabled;
  77}
  78EXPORT_SYMBOL_GPL(sysrq_mask);
  79
  80/*
  81 * A value of 1 means 'all', other nonzero values are an op mask:
  82 */
  83static bool sysrq_on_mask(int mask)
  84{
  85	return sysrq_always_enabled ||
  86	       sysrq_enabled == 1 ||
  87	       (sysrq_enabled & mask);
  88}
  89
  90static int __init sysrq_always_enabled_setup(char *str)
  91{
  92	sysrq_always_enabled = true;
  93	pr_info("sysrq always enabled.\n");
  94
  95	return 1;
  96}
  97
  98__setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  99
 100
 101static void sysrq_handle_loglevel(u8 key)
 102{
 103	u8 loglevel = key - '0';
 104
 105	console_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
 106	pr_info("Loglevel set to %u\n", loglevel);
 107	console_loglevel = loglevel;
 108}
 109static const struct sysrq_key_op sysrq_loglevel_op = {
 110	.handler	= sysrq_handle_loglevel,
 111	.help_msg	= "loglevel(0-9)",
 112	.action_msg	= "Changing Loglevel",
 113	.enable_mask	= SYSRQ_ENABLE_LOG,
 114};
 115
 116#ifdef CONFIG_VT
 117static void sysrq_handle_SAK(u8 key)
 118{
 119	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
 120
 121	schedule_work(SAK_work);
 122}
 123static const struct sysrq_key_op sysrq_SAK_op = {
 124	.handler	= sysrq_handle_SAK,
 125	.help_msg	= "sak(k)",
 126	.action_msg	= "SAK",
 127	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
 128};
 129#else
 130#define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
 131#endif
 132
 133#ifdef CONFIG_VT
 134static void sysrq_handle_unraw(u8 key)
 135{
 136	vt_reset_unicode(fg_console);
 137}
 138
 139static const struct sysrq_key_op sysrq_unraw_op = {
 140	.handler	= sysrq_handle_unraw,
 141	.help_msg	= "unraw(r)",
 142	.action_msg	= "Keyboard mode set to system default",
 143	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
 144};
 145#else
 146#define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL)
 147#endif /* CONFIG_VT */
 148
 149static void sysrq_handle_crash(u8 key)
 150{
 151	/* release the RCU read lock before crashing */
 152	rcu_read_unlock();
 153
 154	panic("sysrq triggered crash\n");
 155}
 156static const struct sysrq_key_op sysrq_crash_op = {
 157	.handler	= sysrq_handle_crash,
 158	.help_msg	= "crash(c)",
 159	.action_msg	= "Trigger a crash",
 160	.enable_mask	= SYSRQ_ENABLE_DUMP,
 161};
 162
 163static void sysrq_handle_reboot(u8 key)
 164{
 165	lockdep_off();
 166	local_irq_enable();
 167	emergency_restart();
 168}
 169static const struct sysrq_key_op sysrq_reboot_op = {
 170	.handler	= sysrq_handle_reboot,
 171	.help_msg	= "reboot(b)",
 172	.action_msg	= "Resetting",
 173	.enable_mask	= SYSRQ_ENABLE_BOOT,
 174};
 175
 176const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op;
 177
 178static void sysrq_handle_sync(u8 key)
 179{
 180	emergency_sync();
 181}
 182static const struct sysrq_key_op sysrq_sync_op = {
 183	.handler	= sysrq_handle_sync,
 184	.help_msg	= "sync(s)",
 185	.action_msg	= "Emergency Sync",
 186	.enable_mask	= SYSRQ_ENABLE_SYNC,
 187};
 188
 189static void sysrq_handle_show_timers(u8 key)
 190{
 191	sysrq_timer_list_show();
 192}
 193
 194static const struct sysrq_key_op sysrq_show_timers_op = {
 195	.handler	= sysrq_handle_show_timers,
 196	.help_msg	= "show-all-timers(q)",
 197	.action_msg	= "Show clockevent devices & pending hrtimers (no others)",
 198};
 199
 200static void sysrq_handle_mountro(u8 key)
 201{
 202	emergency_remount();
 203}
 204static const struct sysrq_key_op sysrq_mountro_op = {
 205	.handler	= sysrq_handle_mountro,
 206	.help_msg	= "unmount(u)",
 207	.action_msg	= "Emergency Remount R/O",
 208	.enable_mask	= SYSRQ_ENABLE_REMOUNT,
 209};
 210
 211#ifdef CONFIG_LOCKDEP
 212static void sysrq_handle_showlocks(u8 key)
 213{
 214	debug_show_all_locks();
 215}
 216
 217static const struct sysrq_key_op sysrq_showlocks_op = {
 218	.handler	= sysrq_handle_showlocks,
 219	.help_msg	= "show-all-locks(d)",
 220	.action_msg	= "Show Locks Held",
 221};
 222#else
 223#define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL)
 224#endif
 225
 226#ifdef CONFIG_SMP
 227static DEFINE_RAW_SPINLOCK(show_lock);
 228
 229static void showacpu(void *dummy)
 230{
 231	unsigned long flags;
 232
 233	/* Idle CPUs have no interesting backtrace. */
 234	if (idle_cpu(smp_processor_id())) {
 235		pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
 236		return;
 237	}
 238
 239	raw_spin_lock_irqsave(&show_lock, flags);
 240	pr_info("CPU%d:\n", smp_processor_id());
 241	show_stack(NULL, NULL, KERN_INFO);
 242	raw_spin_unlock_irqrestore(&show_lock, flags);
 243}
 244
 245static void sysrq_showregs_othercpus(struct work_struct *dummy)
 246{
 247	smp_call_function(showacpu, NULL, 0);
 248}
 249
 250static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 251
 252static void sysrq_handle_showallcpus(u8 key)
 253{
 254	/*
 255	 * Fall back to the workqueue based printing if the
 256	 * backtrace printing did not succeed or the
 257	 * architecture has no support for it:
 258	 */
 259	if (!trigger_all_cpu_backtrace()) {
 260		struct pt_regs *regs = NULL;
 261
 262		if (in_hardirq())
 263			regs = get_irq_regs();
 264
 265		pr_info("CPU%d:\n", get_cpu());
 266		if (regs)
 267			show_regs(regs);
 268		else
 269			show_stack(NULL, NULL, KERN_INFO);
 270
 271		schedule_work(&sysrq_showallcpus);
 272		put_cpu();
 273	}
 274}
 275
 276static const struct sysrq_key_op sysrq_showallcpus_op = {
 277	.handler	= sysrq_handle_showallcpus,
 278	.help_msg	= "show-backtrace-all-active-cpus(l)",
 279	.action_msg	= "Show backtrace of all active CPUs",
 280	.enable_mask	= SYSRQ_ENABLE_DUMP,
 281};
 282#else
 283#define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL)
 284#endif
 285
 286static void sysrq_handle_showregs(u8 key)
 287{
 288	struct pt_regs *regs = NULL;
 289
 290	if (in_hardirq())
 291		regs = get_irq_regs();
 292	if (regs)
 293		show_regs(regs);
 294	perf_event_print_debug();
 295}
 296static const struct sysrq_key_op sysrq_showregs_op = {
 297	.handler	= sysrq_handle_showregs,
 298	.help_msg	= "show-registers(p)",
 299	.action_msg	= "Show Regs",
 300	.enable_mask	= SYSRQ_ENABLE_DUMP,
 301};
 302
 303static void sysrq_handle_showstate(u8 key)
 304{
 305	show_state();
 306	show_all_workqueues();
 307}
 308static const struct sysrq_key_op sysrq_showstate_op = {
 309	.handler	= sysrq_handle_showstate,
 310	.help_msg	= "show-task-states(t)",
 311	.action_msg	= "Show State",
 312	.enable_mask	= SYSRQ_ENABLE_DUMP,
 313};
 314
 315static void sysrq_handle_showstate_blocked(u8 key)
 316{
 317	show_state_filter(TASK_UNINTERRUPTIBLE);
 318}
 319static const struct sysrq_key_op sysrq_showstate_blocked_op = {
 320	.handler	= sysrq_handle_showstate_blocked,
 321	.help_msg	= "show-blocked-tasks(w)",
 322	.action_msg	= "Show Blocked State",
 323	.enable_mask	= SYSRQ_ENABLE_DUMP,
 324};
 325
 326#ifdef CONFIG_TRACING
 327#include <linux/ftrace.h>
 328
 329static void sysrq_ftrace_dump(u8 key)
 330{
 331	ftrace_dump(DUMP_ALL);
 332}
 333static const struct sysrq_key_op sysrq_ftrace_dump_op = {
 334	.handler	= sysrq_ftrace_dump,
 335	.help_msg	= "dump-ftrace-buffer(z)",
 336	.action_msg	= "Dump ftrace buffer",
 337	.enable_mask	= SYSRQ_ENABLE_DUMP,
 338};
 339#else
 340#define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL)
 341#endif
 342
 343static void sysrq_handle_showmem(u8 key)
 344{
 345	show_mem();
 346}
 347static const struct sysrq_key_op sysrq_showmem_op = {
 348	.handler	= sysrq_handle_showmem,
 349	.help_msg	= "show-memory-usage(m)",
 350	.action_msg	= "Show Memory",
 351	.enable_mask	= SYSRQ_ENABLE_DUMP,
 352};
 353
 354/*
 355 * Signal sysrq helper function.  Sends a signal to all user processes.
 356 */
 357static void send_sig_all(int sig)
 358{
 359	struct task_struct *p;
 360
 361	read_lock(&tasklist_lock);
 362	for_each_process(p) {
 363		if (p->flags & PF_KTHREAD)
 364			continue;
 365		if (is_global_init(p))
 366			continue;
 367
 368		do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX);
 369	}
 370	read_unlock(&tasklist_lock);
 371}
 372
 373static void sysrq_handle_term(u8 key)
 374{
 375	send_sig_all(SIGTERM);
 376	console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 377}
 378static const struct sysrq_key_op sysrq_term_op = {
 379	.handler	= sysrq_handle_term,
 380	.help_msg	= "terminate-all-tasks(e)",
 381	.action_msg	= "Terminate All Tasks",
 382	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
 383};
 384
 385static void moom_callback(struct work_struct *ignored)
 386{
 387	const gfp_t gfp_mask = GFP_KERNEL;
 388	struct oom_control oc = {
 389		.zonelist = node_zonelist(first_memory_node, gfp_mask),
 390		.nodemask = NULL,
 391		.memcg = NULL,
 392		.gfp_mask = gfp_mask,
 393		.order = -1,
 394	};
 395
 396	mutex_lock(&oom_lock);
 397	if (!out_of_memory(&oc))
 398		pr_info("OOM request ignored. No task eligible\n");
 399	mutex_unlock(&oom_lock);
 400}
 401
 402static DECLARE_WORK(moom_work, moom_callback);
 403
 404static void sysrq_handle_moom(u8 key)
 405{
 406	schedule_work(&moom_work);
 407}
 408static const struct sysrq_key_op sysrq_moom_op = {
 409	.handler	= sysrq_handle_moom,
 410	.help_msg	= "memory-full-oom-kill(f)",
 411	.action_msg	= "Manual OOM execution",
 412	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
 413};
 414
 415#ifdef CONFIG_BLOCK
 416static void sysrq_handle_thaw(u8 key)
 417{
 418	emergency_thaw_all();
 419}
 420static const struct sysrq_key_op sysrq_thaw_op = {
 421	.handler	= sysrq_handle_thaw,
 422	.help_msg	= "thaw-filesystems(j)",
 423	.action_msg	= "Emergency Thaw of all frozen filesystems",
 424	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
 425};
 426#else
 427#define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL)
 428#endif
 429
 430static void sysrq_handle_kill(u8 key)
 431{
 432	send_sig_all(SIGKILL);
 433	console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 434}
 435static const struct sysrq_key_op sysrq_kill_op = {
 436	.handler	= sysrq_handle_kill,
 437	.help_msg	= "kill-all-tasks(i)",
 438	.action_msg	= "Kill All Tasks",
 439	.enable_mask	= SYSRQ_ENABLE_SIGNAL,
 440};
 441
 442static void sysrq_handle_unrt(u8 key)
 443{
 444	normalize_rt_tasks();
 445}
 446static const struct sysrq_key_op sysrq_unrt_op = {
 447	.handler	= sysrq_handle_unrt,
 448	.help_msg	= "nice-all-RT-tasks(n)",
 449	.action_msg	= "Nice All RT Tasks",
 450	.enable_mask	= SYSRQ_ENABLE_RTNICE,
 451};
 452
 453static void sysrq_handle_replay_logs(u8 key)
 454{
 455	console_try_replay_all();
 456}
 457static struct sysrq_key_op sysrq_replay_logs_op = {
 458	.handler        = sysrq_handle_replay_logs,
 459	.help_msg       = "replay-kernel-logs(R)",
 460	.action_msg     = "Replay kernel logs on consoles",
 461	.enable_mask    = SYSRQ_ENABLE_DUMP,
 462};
 463
 464/* Key Operations table and lock */
 465static DEFINE_SPINLOCK(sysrq_key_table_lock);
 466
 467static const struct sysrq_key_op *sysrq_key_table[62] = {
 468	&sysrq_loglevel_op,		/* 0 */
 469	&sysrq_loglevel_op,		/* 1 */
 470	&sysrq_loglevel_op,		/* 2 */
 471	&sysrq_loglevel_op,		/* 3 */
 472	&sysrq_loglevel_op,		/* 4 */
 473	&sysrq_loglevel_op,		/* 5 */
 474	&sysrq_loglevel_op,		/* 6 */
 475	&sysrq_loglevel_op,		/* 7 */
 476	&sysrq_loglevel_op,		/* 8 */
 477	&sysrq_loglevel_op,		/* 9 */
 478
 479	/*
 480	 * a: Don't use for system provided sysrqs, it is handled specially on
 481	 * sparc and will never arrive.
 482	 */
 483	NULL,				/* a */
 484	&sysrq_reboot_op,		/* b */
 485	&sysrq_crash_op,		/* c */
 486	&sysrq_showlocks_op,		/* d */
 487	&sysrq_term_op,			/* e */
 488	&sysrq_moom_op,			/* f */
 489	/* g: May be registered for the kernel debugger */
 490	NULL,				/* g */
 491	NULL,				/* h - reserved for help */
 492	&sysrq_kill_op,			/* i */
 493	&sysrq_thaw_op,			/* j */
 494	&sysrq_SAK_op,			/* k */
 495	&sysrq_showallcpus_op,		/* l */
 496	&sysrq_showmem_op,		/* m */
 497	&sysrq_unrt_op,			/* n */
 498	/* o: This will often be registered as 'Off' at init time */
 499	NULL,				/* o */
 500	&sysrq_showregs_op,		/* p */
 501	&sysrq_show_timers_op,		/* q */
 502	&sysrq_unraw_op,		/* r */
 503	&sysrq_sync_op,			/* s */
 504	&sysrq_showstate_op,		/* t */
 505	&sysrq_mountro_op,		/* u */
 506	/* v: May be registered for frame buffer console restore */
 507	NULL,				/* v */
 508	&sysrq_showstate_blocked_op,	/* w */
 509	/* x: May be registered on mips for TLB dump */
 510	/* x: May be registered on ppc/powerpc for xmon */
 511	/* x: May be registered on sparc64 for global PMU dump */
 512	NULL,				/* x */
 513	/* y: May be registered on sparc64 for global register dump */
 514	NULL,				/* y */
 515	&sysrq_ftrace_dump_op,		/* z */
 516	NULL,				/* A */
 517	NULL,				/* B */
 518	NULL,				/* C */
 519	NULL,				/* D */
 520	NULL,				/* E */
 521	NULL,				/* F */
 522	NULL,				/* G */
 523	NULL,				/* H */
 524	NULL,				/* I */
 525	NULL,				/* J */
 526	NULL,				/* K */
 527	NULL,				/* L */
 528	NULL,				/* M */
 529	NULL,				/* N */
 530	NULL,				/* O */
 531	NULL,				/* P */
 532	NULL,				/* Q */
 533	&sysrq_replay_logs_op,		/* R */
 534	/* S: May be registered by sched_ext for resetting */
 535	NULL,				/* S */
 536	NULL,				/* T */
 537	NULL,				/* U */
 538	NULL,				/* V */
 539	NULL,				/* W */
 540	NULL,				/* X */
 541	NULL,				/* Y */
 542	NULL,				/* Z */
 543};
 544
 545/* key2index calculation, -1 on invalid index */
 546static int sysrq_key_table_key2index(u8 key)
 547{
 548	switch (key) {
 549	case '0' ... '9':
 550		return key - '0';
 551	case 'a' ... 'z':
 552		return key - 'a' + 10;
 553	case 'A' ... 'Z':
 554		return key - 'A' + 10 + 26;
 555	default:
 556		return -1;
 557	}
 558}
 559
 560/*
 561 * get and put functions for the table, exposed to modules.
 562 */
 563static const struct sysrq_key_op *__sysrq_get_key_op(u8 key)
 564{
 565	const struct sysrq_key_op *op_p = NULL;
 566	int i;
 567
 568	i = sysrq_key_table_key2index(key);
 569	if (i != -1)
 570		op_p = sysrq_key_table[i];
 571
 572	return op_p;
 573}
 574
 575static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p)
 576{
 577	int i = sysrq_key_table_key2index(key);
 578
 579	if (i != -1)
 580		sysrq_key_table[i] = op_p;
 581}
 582
 583void __handle_sysrq(u8 key, bool check_mask)
 584{
 585	const struct sysrq_key_op *op_p;
 586	int orig_suppress_printk;
 587	int i;
 588
 589	orig_suppress_printk = suppress_printk;
 590	suppress_printk = 0;
 591
 592	rcu_sysrq_start();
 593	rcu_read_lock();
 594	/*
 595	 * Enter in the force_console context so that sysrq header is shown to
 596	 * provide the user with positive feedback.  We do not simply emit this
 597	 * at KERN_EMERG as that would change message routing in the consumers
 598	 * of /proc/kmsg.
 599	 */
 600	printk_force_console_enter();
 601
 602	op_p = __sysrq_get_key_op(key);
 603	if (op_p) {
 604		/*
 605		 * Should we check for enabled operations (/proc/sysrq-trigger
 606		 * should not) and is the invoked operation enabled?
 607		 */
 608		if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 609			pr_info("%s\n", op_p->action_msg);
 610			printk_force_console_exit();
 611			op_p->handler(key);
 612		} else {
 613			pr_info("This sysrq operation is disabled.\n");
 614			printk_force_console_exit();
 615		}
 616	} else {
 617		pr_info("HELP : ");
 618		/* Only print the help msg once per handler */
 619		for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 620			if (sysrq_key_table[i]) {
 621				int j;
 622
 623				for (j = 0; sysrq_key_table[i] !=
 624						sysrq_key_table[j]; j++)
 625					;
 626				if (j != i)
 627					continue;
 628				pr_cont("%s ", sysrq_key_table[i]->help_msg);
 629			}
 630		}
 631		pr_cont("\n");
 632		printk_force_console_exit();
 633	}
 634	rcu_read_unlock();
 635	rcu_sysrq_end();
 636
 637	suppress_printk = orig_suppress_printk;
 638}
 639
 640void handle_sysrq(u8 key)
 641{
 642	if (sysrq_on())
 643		__handle_sysrq(key, true);
 644}
 645EXPORT_SYMBOL(handle_sysrq);
 646
 647#ifdef CONFIG_INPUT
 648static int sysrq_reset_downtime_ms;
 649
 650/* Simple translation table for the SysRq keys */
 651static const unsigned char sysrq_xlate[KEY_CNT] =
 652	"\000\0331234567890-=\177\t"                    /* 0x00 - 0x0f */
 653	"qwertyuiop[]\r\000as"                          /* 0x10 - 0x1f */
 654	"dfghjkl;'`\000\\zxcv"                          /* 0x20 - 0x2f */
 655	"bnm,./\000*\000 \000\201\202\203\204\205"      /* 0x30 - 0x3f */
 656	"\206\207\210\211\212\000\000789-456+1"         /* 0x40 - 0x4f */
 657	"230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */
 658	"\r\000/";                                      /* 0x60 - 0x6f */
 659
 660struct sysrq_state {
 661	struct input_handle handle;
 662	struct work_struct reinject_work;
 663	unsigned long key_down[BITS_TO_LONGS(KEY_CNT)];
 664	unsigned int alt;
 665	unsigned int alt_use;
 666	unsigned int shift;
 667	unsigned int shift_use;
 668	bool active;
 669	bool need_reinject;
 670	bool reinjecting;
 671
 672	/* reset sequence handling */
 673	bool reset_canceled;
 674	bool reset_requested;
 675	unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)];
 676	int reset_seq_len;
 677	int reset_seq_cnt;
 678	int reset_seq_version;
 679	struct timer_list keyreset_timer;
 680};
 681
 682#define SYSRQ_KEY_RESET_MAX	20 /* Should be plenty */
 683static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX];
 684static unsigned int sysrq_reset_seq_len;
 685static unsigned int sysrq_reset_seq_version = 1;
 686
 687static void sysrq_parse_reset_sequence(struct sysrq_state *state)
 688{
 689	int i;
 690	unsigned short key;
 691
 692	state->reset_seq_cnt = 0;
 693
 694	for (i = 0; i < sysrq_reset_seq_len; i++) {
 695		key = sysrq_reset_seq[i];
 696
 697		if (key == KEY_RESERVED || key > KEY_MAX)
 698			break;
 699
 700		__set_bit(key, state->reset_keybit);
 701		state->reset_seq_len++;
 702
 703		if (test_bit(key, state->key_down))
 704			state->reset_seq_cnt++;
 705	}
 706
 707	/* Disable reset until old keys are not released */
 708	state->reset_canceled = state->reset_seq_cnt != 0;
 709
 710	state->reset_seq_version = sysrq_reset_seq_version;
 711}
 712
 713static void sysrq_do_reset(struct timer_list *t)
 714{
 715	struct sysrq_state *state = timer_container_of(state, t,
 716						       keyreset_timer);
 717
 718	state->reset_requested = true;
 719
 720	orderly_reboot();
 721}
 722
 723static void sysrq_handle_reset_request(struct sysrq_state *state)
 724{
 725	if (state->reset_requested)
 726		__handle_sysrq(sysrq_xlate[KEY_B], false);
 727
 728	if (sysrq_reset_downtime_ms)
 729		mod_timer(&state->keyreset_timer,
 730			jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms));
 731	else
 732		sysrq_do_reset(&state->keyreset_timer);
 733}
 734
 735static void sysrq_detect_reset_sequence(struct sysrq_state *state,
 736					unsigned int code, int value)
 737{
 738	if (!test_bit(code, state->reset_keybit)) {
 739		/*
 740		 * Pressing any key _not_ in reset sequence cancels
 741		 * the reset sequence.  Also cancelling the timer in
 742		 * case additional keys were pressed after a reset
 743		 * has been requested.
 744		 */
 745		if (value && state->reset_seq_cnt) {
 746			state->reset_canceled = true;
 747			timer_delete(&state->keyreset_timer);
 748		}
 749	} else if (value == 0) {
 750		/*
 751		 * Key release - all keys in the reset sequence need
 752		 * to be pressed and held for the reset timeout
 753		 * to hold.
 754		 */
 755		timer_delete(&state->keyreset_timer);
 756
 757		if (--state->reset_seq_cnt == 0)
 758			state->reset_canceled = false;
 759	} else if (value == 1) {
 760		/* key press, not autorepeat */
 761		if (++state->reset_seq_cnt == state->reset_seq_len &&
 762		    !state->reset_canceled) {
 763			sysrq_handle_reset_request(state);
 764		}
 765	}
 766}
 767
 768#ifdef CONFIG_OF
 769static void sysrq_of_get_keyreset_config(void)
 770{
 771	u32 key;
 772	struct device_node *np;
 773
 774	np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq");
 775	if (!np) {
 776		pr_debug("No sysrq node found");
 777		return;
 778	}
 779
 780	/* Reset in case a __weak definition was present */
 781	sysrq_reset_seq_len = 0;
 782
 783	of_property_for_each_u32(np, "keyset", key) {
 784		if (key == KEY_RESERVED || key > KEY_MAX ||
 785		    sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX)
 786			break;
 787
 788		sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key;
 789	}
 790
 791	/* Get reset timeout if any. */
 792	of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms);
 793
 794	of_node_put(np);
 795}
 796#else
 797static void sysrq_of_get_keyreset_config(void)
 798{
 799}
 800#endif
 801
 802static void sysrq_reinject_alt_sysrq(struct work_struct *work)
 803{
 804	struct sysrq_state *sysrq =
 805			container_of(work, struct sysrq_state, reinject_work);
 806	struct input_handle *handle = &sysrq->handle;
 807	unsigned int alt_code = sysrq->alt_use;
 808
 809	if (sysrq->need_reinject) {
 810		/* we do not want the assignment to be reordered */
 811		sysrq->reinjecting = true;
 812		mb();
 813
 814		/* Simulate press and release of Alt + SysRq */
 815		input_inject_event(handle, EV_KEY, alt_code, 1);
 816		input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1);
 817		input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 818
 819		input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0);
 820		input_inject_event(handle, EV_KEY, alt_code, 0);
 821		input_inject_event(handle, EV_SYN, SYN_REPORT, 1);
 822
 823		mb();
 824		sysrq->reinjecting = false;
 825	}
 826}
 827
 828static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
 829				  unsigned int code, int value)
 830{
 831	bool was_active = sysrq->active;
 832	bool suppress;
 833
 834	switch (code) {
 835
 836	case KEY_LEFTALT:
 837	case KEY_RIGHTALT:
 838		if (!value) {
 839			/* One of ALTs is being released */
 840			if (sysrq->active && code == sysrq->alt_use)
 841				sysrq->active = false;
 842
 843			sysrq->alt = KEY_RESERVED;
 844
 845		} else if (value != 2) {
 846			sysrq->alt = code;
 847			sysrq->need_reinject = false;
 848		}
 849		break;
 850
 851	case KEY_LEFTSHIFT:
 852	case KEY_RIGHTSHIFT:
 853		if (!value)
 854			sysrq->shift = KEY_RESERVED;
 855		else if (value != 2)
 856			sysrq->shift = code;
 857		if (sysrq->active)
 858			sysrq->shift_use = sysrq->shift;
 859		break;
 860
 861	case KEY_SYSRQ:
 862		if (value == 1 && sysrq->alt != KEY_RESERVED) {
 863			sysrq->active = true;
 864			sysrq->alt_use = sysrq->alt;
 865			/* either RESERVED (for released) or actual code */
 866			sysrq->shift_use = sysrq->shift;
 867			/*
 868			 * If nothing else will be pressed we'll need
 869			 * to re-inject Alt-SysRq keysroke.
 870			 */
 871			sysrq->need_reinject = true;
 872		}
 873
 874		/*
 875		 * Pretend that sysrq was never pressed at all. This
 876		 * is needed to properly handle KGDB which will try
 877		 * to release all keys after exiting debugger. If we
 878		 * do not clear key bit it KGDB will end up sending
 879		 * release events for Alt and SysRq, potentially
 880		 * triggering print screen function.
 881		 */
 882		if (sysrq->active)
 883			clear_bit(KEY_SYSRQ, sysrq->handle.dev->key);
 884
 885		break;
 886
 887	default:
 888		if (sysrq->active && value && value != 2) {
 889			unsigned char c = sysrq_xlate[code];
 890
 891			sysrq->need_reinject = false;
 892			if (sysrq->shift_use != KEY_RESERVED)
 893				c = toupper(c);
 894			__handle_sysrq(c, true);
 895		}
 896		break;
 897	}
 898
 899	suppress = sysrq->active;
 900
 901	if (!sysrq->active) {
 902
 903		/*
 904		 * See if reset sequence has changed since the last time.
 905		 */
 906		if (sysrq->reset_seq_version != sysrq_reset_seq_version)
 907			sysrq_parse_reset_sequence(sysrq);
 908
 909		/*
 910		 * If we are not suppressing key presses keep track of
 911		 * keyboard state so we can release keys that have been
 912		 * pressed before entering SysRq mode.
 913		 */
 914		if (value)
 915			set_bit(code, sysrq->key_down);
 916		else
 917			clear_bit(code, sysrq->key_down);
 918
 919		if (was_active)
 920			schedule_work(&sysrq->reinject_work);
 921
 922		/* Check for reset sequence */
 923		sysrq_detect_reset_sequence(sysrq, code, value);
 924
 925	} else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) {
 926		/*
 927		 * Pass on release events for keys that was pressed before
 928		 * entering SysRq mode.
 929		 */
 930		suppress = false;
 931	}
 932
 933	return suppress;
 934}
 935
 936static bool sysrq_filter(struct input_handle *handle,
 937			 unsigned int type, unsigned int code, int value)
 938{
 939	struct sysrq_state *sysrq = handle->private;
 940	bool suppress;
 941
 942	/*
 943	 * Do not filter anything if we are in the process of re-injecting
 944	 * Alt+SysRq combination.
 945	 */
 946	if (sysrq->reinjecting)
 947		return false;
 948
 949	switch (type) {
 950
 951	case EV_SYN:
 952		suppress = false;
 953		break;
 954
 955	case EV_KEY:
 956		suppress = sysrq_handle_keypress(sysrq, code, value);
 957		break;
 958
 959	default:
 960		suppress = sysrq->active;
 961		break;
 962	}
 963
 964	return suppress;
 965}
 966
 967static int sysrq_connect(struct input_handler *handler,
 968			 struct input_dev *dev,
 969			 const struct input_device_id *id)
 970{
 971	struct sysrq_state *sysrq;
 972	int error;
 973
 974	sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL);
 975	if (!sysrq)
 976		return -ENOMEM;
 977
 978	INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq);
 979
 980	sysrq->handle.dev = dev;
 981	sysrq->handle.handler = handler;
 982	sysrq->handle.name = "sysrq";
 983	sysrq->handle.private = sysrq;
 984	timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0);
 985
 986	error = input_register_handle(&sysrq->handle);
 987	if (error) {
 988		pr_err("Failed to register input sysrq handler, error %d\n",
 989			error);
 990		goto err_free;
 991	}
 992
 993	error = input_open_device(&sysrq->handle);
 994	if (error) {
 995		pr_err("Failed to open input device, error %d\n", error);
 996		goto err_unregister;
 997	}
 998
 999	return 0;
1000
1001 err_unregister:
1002	input_unregister_handle(&sysrq->handle);
1003 err_free:
1004	kfree(sysrq);
1005	return error;
1006}
1007
1008static void sysrq_disconnect(struct input_handle *handle)
1009{
1010	struct sysrq_state *sysrq = handle->private;
1011
1012	input_close_device(handle);
1013	cancel_work_sync(&sysrq->reinject_work);
1014	timer_shutdown_sync(&sysrq->keyreset_timer);
1015	input_unregister_handle(handle);
1016	kfree(sysrq);
1017}
1018
1019/*
1020 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
1021 * keyboards have SysRq key predefined and so user may add it to keymap
1022 * later, but we expect all such keyboards to have left alt.
1023 */
1024static const struct input_device_id sysrq_ids[] = {
1025	{
1026		.flags = INPUT_DEVICE_ID_MATCH_EVBIT |
1027				INPUT_DEVICE_ID_MATCH_KEYBIT,
1028		.evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) },
1029		.keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) },
1030	},
1031	{ },
1032};
1033
1034static struct input_handler sysrq_handler = {
1035	.filter		= sysrq_filter,
1036	.connect	= sysrq_connect,
1037	.disconnect	= sysrq_disconnect,
1038	.name		= "sysrq",
1039	.id_table	= sysrq_ids,
1040};
1041
1042static inline void sysrq_register_handler(void)
1043{
1044	int error;
1045
1046	sysrq_of_get_keyreset_config();
1047
1048	error = input_register_handler(&sysrq_handler);
1049	if (error)
1050		pr_err("Failed to register input handler, error %d", error);
1051}
1052
1053static inline void sysrq_unregister_handler(void)
1054{
1055	input_unregister_handler(&sysrq_handler);
1056}
1057
1058static int sysrq_reset_seq_param_set(const char *buffer,
1059				     const struct kernel_param *kp)
1060{
1061	unsigned long val;
1062	int error;
1063
1064	error = kstrtoul(buffer, 0, &val);
1065	if (error < 0)
1066		return error;
1067
1068	if (val > KEY_MAX)
1069		return -EINVAL;
1070
1071	*((unsigned short *)kp->arg) = val;
1072	sysrq_reset_seq_version++;
1073
1074	return 0;
1075}
1076
1077static const struct kernel_param_ops param_ops_sysrq_reset_seq = {
1078	.get	= param_get_ushort,
1079	.set	= sysrq_reset_seq_param_set,
1080};
1081
1082#define param_check_sysrq_reset_seq(name, p)	\
1083	__param_check(name, p, unsigned short)
1084
1085/*
1086 * not really modular, but the easiest way to keep compat with existing
1087 * bootargs behaviour is to continue using module_param here.
1088 */
1089module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq,
1090			 &sysrq_reset_seq_len, 0644);
1091
1092module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644);
1093
1094#else
1095
1096static inline void sysrq_register_handler(void)
1097{
1098}
1099
1100static inline void sysrq_unregister_handler(void)
1101{
1102}
1103
1104#endif /* CONFIG_INPUT */
1105
1106int sysrq_toggle_support(int enable_mask)
1107{
1108	bool was_enabled = sysrq_on();
1109
1110	sysrq_enabled = enable_mask;
1111
1112	if (was_enabled != sysrq_on()) {
1113		if (sysrq_on())
1114			sysrq_register_handler();
1115		else
1116			sysrq_unregister_handler();
1117	}
1118
1119	return 0;
1120}
1121EXPORT_SYMBOL_GPL(sysrq_toggle_support);
1122
1123static int sysrq_sysctl_handler(const struct ctl_table *table, int write,
1124				void *buffer, size_t *lenp, loff_t *ppos)
1125{
1126	int tmp, ret;
1127	struct ctl_table t = *table;
1128
1129	tmp = sysrq_mask();
1130	t.data = &tmp;
1131
1132	/*
1133	 * Behaves like do_proc_dointvec as t does not have min nor max.
1134	 */
1135	ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
1136	if (ret)
1137		return ret;
1138
1139	if (write)
1140		sysrq_toggle_support(tmp);
1141
1142	return 0;
1143}
1144
1145static const struct ctl_table sysrq_sysctl_table[] = {
1146	{
1147		.procname	= "sysrq",
1148		.data		= NULL,
1149		.maxlen		= sizeof(int),
1150		.mode		= 0644,
1151		.proc_handler	= sysrq_sysctl_handler,
1152	},
1153};
1154
1155static int __init init_sysrq_sysctl(void)
1156{
1157	register_sysctl_init("kernel", sysrq_sysctl_table);
1158	return 0;
1159}
1160
1161subsys_initcall(init_sysrq_sysctl);
1162
1163static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p,
1164				const struct sysrq_key_op *remove_op_p)
1165{
1166	int retval;
1167
1168	spin_lock(&sysrq_key_table_lock);
1169	if (__sysrq_get_key_op(key) == remove_op_p) {
1170		__sysrq_put_key_op(key, insert_op_p);
1171		retval = 0;
1172	} else {
1173		retval = -1;
1174	}
1175	spin_unlock(&sysrq_key_table_lock);
1176
1177	/*
1178	 * A concurrent __handle_sysrq either got the old op or the new op.
1179	 * Wait for it to go away before returning, so the code for an old
1180	 * op is not freed (eg. on module unload) while it is in use.
1181	 */
1182	synchronize_rcu();
1183
1184	return retval;
1185}
1186
1187int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1188{
1189	return __sysrq_swap_key_ops(key, op_p, NULL);
1190}
1191EXPORT_SYMBOL(register_sysrq_key);
1192
1193int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p)
1194{
1195	return __sysrq_swap_key_ops(key, NULL, op_p);
1196}
1197EXPORT_SYMBOL(unregister_sysrq_key);
1198
1199#ifdef CONFIG_PROC_FS
1200/*
1201 * writing 'C' to /proc/sysrq-trigger is like sysrq-C
1202 * Normally, only the first character written is processed.
1203 * However, if the first character is an underscore,
1204 * all characters are processed.
1205 */
1206static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
1207				   size_t count, loff_t *ppos)
1208{
1209	bool bulk = false;
1210	size_t i;
1211
1212	for (i = 0; i < count; i++) {
1213		char c;
1214
1215		if (get_user(c, buf + i))
1216			return -EFAULT;
1217
1218		if (c == '_')
1219			bulk = true;
1220		else
1221			__handle_sysrq(c, false);
1222
1223		if (!bulk)
1224			break;
1225	}
1226
1227	return count;
1228}
1229
1230static const struct proc_ops sysrq_trigger_proc_ops = {
1231	.proc_write	= write_sysrq_trigger,
1232	.proc_lseek	= noop_llseek,
1233};
1234
1235static void sysrq_init_procfs(void)
1236{
1237	if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
1238			 &sysrq_trigger_proc_ops))
1239		pr_err("Failed to register proc interface\n");
1240}
1241
1242#else
1243
1244static inline void sysrq_init_procfs(void)
1245{
1246}
1247
1248#endif /* CONFIG_PROC_FS */
1249
1250static int __init sysrq_init(void)
1251{
1252	sysrq_init_procfs();
1253
1254	if (sysrq_on())
1255		sysrq_register_handler();
1256
1257	return 0;
1258}
1259device_initcall(sysrq_init);