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(int key) 102{ 103 int i; 104 105 i = key - '0'; 106 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 107 pr_info("Loglevel set to %d\n", i); 108 console_loglevel = i; 109} 110static const struct sysrq_key_op sysrq_loglevel_op = { 111 .handler = sysrq_handle_loglevel, 112 .help_msg = "loglevel(0-9)", 113 .action_msg = "Changing Loglevel", 114 .enable_mask = SYSRQ_ENABLE_LOG, 115}; 116 117#ifdef CONFIG_VT 118static void sysrq_handle_SAK(int key) 119{ 120 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 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(int 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(int 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(int 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(int 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(int 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(int 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(int 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(int 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_irq()) 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#endif 283 284static void sysrq_handle_showregs(int key) 285{ 286 struct pt_regs *regs = NULL; 287 288 if (in_irq()) 289 regs = get_irq_regs(); 290 if (regs) 291 show_regs(regs); 292 perf_event_print_debug(); 293} 294static const struct sysrq_key_op sysrq_showregs_op = { 295 .handler = sysrq_handle_showregs, 296 .help_msg = "show-registers(p)", 297 .action_msg = "Show Regs", 298 .enable_mask = SYSRQ_ENABLE_DUMP, 299}; 300 301static void sysrq_handle_showstate(int key) 302{ 303 show_state(); 304 show_workqueue_state(); 305} 306static const struct sysrq_key_op sysrq_showstate_op = { 307 .handler = sysrq_handle_showstate, 308 .help_msg = "show-task-states(t)", 309 .action_msg = "Show State", 310 .enable_mask = SYSRQ_ENABLE_DUMP, 311}; 312 313static void sysrq_handle_showstate_blocked(int key) 314{ 315 show_state_filter(TASK_UNINTERRUPTIBLE); 316} 317static const struct sysrq_key_op sysrq_showstate_blocked_op = { 318 .handler = sysrq_handle_showstate_blocked, 319 .help_msg = "show-blocked-tasks(w)", 320 .action_msg = "Show Blocked State", 321 .enable_mask = SYSRQ_ENABLE_DUMP, 322}; 323 324#ifdef CONFIG_TRACING 325#include <linux/ftrace.h> 326 327static void sysrq_ftrace_dump(int key) 328{ 329 ftrace_dump(DUMP_ALL); 330} 331static const struct sysrq_key_op sysrq_ftrace_dump_op = { 332 .handler = sysrq_ftrace_dump, 333 .help_msg = "dump-ftrace-buffer(z)", 334 .action_msg = "Dump ftrace buffer", 335 .enable_mask = SYSRQ_ENABLE_DUMP, 336}; 337#else 338#define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL) 339#endif 340 341static void sysrq_handle_showmem(int key) 342{ 343 show_mem(0, NULL); 344} 345static const struct sysrq_key_op sysrq_showmem_op = { 346 .handler = sysrq_handle_showmem, 347 .help_msg = "show-memory-usage(m)", 348 .action_msg = "Show Memory", 349 .enable_mask = SYSRQ_ENABLE_DUMP, 350}; 351 352/* 353 * Signal sysrq helper function. Sends a signal to all user processes. 354 */ 355static void send_sig_all(int sig) 356{ 357 struct task_struct *p; 358 359 read_lock(&tasklist_lock); 360 for_each_process(p) { 361 if (p->flags & PF_KTHREAD) 362 continue; 363 if (is_global_init(p)) 364 continue; 365 366 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX); 367 } 368 read_unlock(&tasklist_lock); 369} 370 371static void sysrq_handle_term(int key) 372{ 373 send_sig_all(SIGTERM); 374 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 375} 376static const struct sysrq_key_op sysrq_term_op = { 377 .handler = sysrq_handle_term, 378 .help_msg = "terminate-all-tasks(e)", 379 .action_msg = "Terminate All Tasks", 380 .enable_mask = SYSRQ_ENABLE_SIGNAL, 381}; 382 383static void moom_callback(struct work_struct *ignored) 384{ 385 const gfp_t gfp_mask = GFP_KERNEL; 386 struct oom_control oc = { 387 .zonelist = node_zonelist(first_memory_node, gfp_mask), 388 .nodemask = NULL, 389 .memcg = NULL, 390 .gfp_mask = gfp_mask, 391 .order = -1, 392 }; 393 394 mutex_lock(&oom_lock); 395 if (!out_of_memory(&oc)) 396 pr_info("OOM request ignored. No task eligible\n"); 397 mutex_unlock(&oom_lock); 398} 399 400static DECLARE_WORK(moom_work, moom_callback); 401 402static void sysrq_handle_moom(int key) 403{ 404 schedule_work(&moom_work); 405} 406static const struct sysrq_key_op sysrq_moom_op = { 407 .handler = sysrq_handle_moom, 408 .help_msg = "memory-full-oom-kill(f)", 409 .action_msg = "Manual OOM execution", 410 .enable_mask = SYSRQ_ENABLE_SIGNAL, 411}; 412 413static void sysrq_handle_thaw(int key) 414{ 415 emergency_thaw_all(); 416} 417static const struct sysrq_key_op sysrq_thaw_op = { 418 .handler = sysrq_handle_thaw, 419 .help_msg = "thaw-filesystems(j)", 420 .action_msg = "Emergency Thaw of all frozen filesystems", 421 .enable_mask = SYSRQ_ENABLE_SIGNAL, 422}; 423 424static void sysrq_handle_kill(int key) 425{ 426 send_sig_all(SIGKILL); 427 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 428} 429static const struct sysrq_key_op sysrq_kill_op = { 430 .handler = sysrq_handle_kill, 431 .help_msg = "kill-all-tasks(i)", 432 .action_msg = "Kill All Tasks", 433 .enable_mask = SYSRQ_ENABLE_SIGNAL, 434}; 435 436static void sysrq_handle_unrt(int key) 437{ 438 normalize_rt_tasks(); 439} 440static const struct sysrq_key_op sysrq_unrt_op = { 441 .handler = sysrq_handle_unrt, 442 .help_msg = "nice-all-RT-tasks(n)", 443 .action_msg = "Nice All RT Tasks", 444 .enable_mask = SYSRQ_ENABLE_RTNICE, 445}; 446 447/* Key Operations table and lock */ 448static DEFINE_SPINLOCK(sysrq_key_table_lock); 449 450static const struct sysrq_key_op *sysrq_key_table[62] = { 451 &sysrq_loglevel_op, /* 0 */ 452 &sysrq_loglevel_op, /* 1 */ 453 &sysrq_loglevel_op, /* 2 */ 454 &sysrq_loglevel_op, /* 3 */ 455 &sysrq_loglevel_op, /* 4 */ 456 &sysrq_loglevel_op, /* 5 */ 457 &sysrq_loglevel_op, /* 6 */ 458 &sysrq_loglevel_op, /* 7 */ 459 &sysrq_loglevel_op, /* 8 */ 460 &sysrq_loglevel_op, /* 9 */ 461 462 /* 463 * a: Don't use for system provided sysrqs, it is handled specially on 464 * sparc and will never arrive. 465 */ 466 NULL, /* a */ 467 &sysrq_reboot_op, /* b */ 468 &sysrq_crash_op, /* c */ 469 &sysrq_showlocks_op, /* d */ 470 &sysrq_term_op, /* e */ 471 &sysrq_moom_op, /* f */ 472 /* g: May be registered for the kernel debugger */ 473 NULL, /* g */ 474 NULL, /* h - reserved for help */ 475 &sysrq_kill_op, /* i */ 476#ifdef CONFIG_BLOCK 477 &sysrq_thaw_op, /* j */ 478#else 479 NULL, /* j */ 480#endif 481 &sysrq_SAK_op, /* k */ 482#ifdef CONFIG_SMP 483 &sysrq_showallcpus_op, /* l */ 484#else 485 NULL, /* l */ 486#endif 487 &sysrq_showmem_op, /* m */ 488 &sysrq_unrt_op, /* n */ 489 /* o: This will often be registered as 'Off' at init time */ 490 NULL, /* o */ 491 &sysrq_showregs_op, /* p */ 492 &sysrq_show_timers_op, /* q */ 493 &sysrq_unraw_op, /* r */ 494 &sysrq_sync_op, /* s */ 495 &sysrq_showstate_op, /* t */ 496 &sysrq_mountro_op, /* u */ 497 /* v: May be registered for frame buffer console restore */ 498 NULL, /* v */ 499 &sysrq_showstate_blocked_op, /* w */ 500 /* x: May be registered on mips for TLB dump */ 501 /* x: May be registered on ppc/powerpc for xmon */ 502 /* x: May be registered on sparc64 for global PMU dump */ 503 NULL, /* x */ 504 /* y: May be registered on sparc64 for global register dump */ 505 NULL, /* y */ 506 &sysrq_ftrace_dump_op, /* z */ 507 NULL, /* A */ 508 NULL, /* B */ 509 NULL, /* C */ 510 NULL, /* D */ 511 NULL, /* E */ 512 NULL, /* F */ 513 NULL, /* G */ 514 NULL, /* H */ 515 NULL, /* I */ 516 NULL, /* J */ 517 NULL, /* K */ 518 NULL, /* L */ 519 NULL, /* M */ 520 NULL, /* N */ 521 NULL, /* O */ 522 NULL, /* P */ 523 NULL, /* Q */ 524 NULL, /* R */ 525 NULL, /* S */ 526 NULL, /* T */ 527 NULL, /* U */ 528 NULL, /* V */ 529 NULL, /* W */ 530 NULL, /* X */ 531 NULL, /* Y */ 532 NULL, /* Z */ 533}; 534 535/* key2index calculation, -1 on invalid index */ 536static int sysrq_key_table_key2index(int key) 537{ 538 int retval; 539 540 if ((key >= '0') && (key <= '9')) 541 retval = key - '0'; 542 else if ((key >= 'a') && (key <= 'z')) 543 retval = key + 10 - 'a'; 544 else if ((key >= 'A') && (key <= 'Z')) 545 retval = key + 36 - 'A'; 546 else 547 retval = -1; 548 return retval; 549} 550 551/* 552 * get and put functions for the table, exposed to modules. 553 */ 554static const struct sysrq_key_op *__sysrq_get_key_op(int key) 555{ 556 const struct sysrq_key_op *op_p = NULL; 557 int i; 558 559 i = sysrq_key_table_key2index(key); 560 if (i != -1) 561 op_p = sysrq_key_table[i]; 562 563 return op_p; 564} 565 566static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p) 567{ 568 int i = sysrq_key_table_key2index(key); 569 570 if (i != -1) 571 sysrq_key_table[i] = op_p; 572} 573 574void __handle_sysrq(int key, bool check_mask) 575{ 576 const struct sysrq_key_op *op_p; 577 int orig_log_level; 578 int orig_suppress_printk; 579 int i; 580 581 orig_suppress_printk = suppress_printk; 582 suppress_printk = 0; 583 584 rcu_sysrq_start(); 585 rcu_read_lock(); 586 /* 587 * Raise the apparent loglevel to maximum so that the sysrq header 588 * is shown to provide the user with positive feedback. We do not 589 * simply emit this at KERN_EMERG as that would change message 590 * routing in the consumers of /proc/kmsg. 591 */ 592 orig_log_level = console_loglevel; 593 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 594 595 op_p = __sysrq_get_key_op(key); 596 if (op_p) { 597 /* 598 * Should we check for enabled operations (/proc/sysrq-trigger 599 * should not) and is the invoked operation enabled? 600 */ 601 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 602 pr_info("%s\n", op_p->action_msg); 603 console_loglevel = orig_log_level; 604 op_p->handler(key); 605 } else { 606 pr_info("This sysrq operation is disabled.\n"); 607 console_loglevel = orig_log_level; 608 } 609 } else { 610 pr_info("HELP : "); 611 /* Only print the help msg once per handler */ 612 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 613 if (sysrq_key_table[i]) { 614 int j; 615 616 for (j = 0; sysrq_key_table[i] != 617 sysrq_key_table[j]; j++) 618 ; 619 if (j != i) 620 continue; 621 pr_cont("%s ", sysrq_key_table[i]->help_msg); 622 } 623 } 624 pr_cont("\n"); 625 console_loglevel = orig_log_level; 626 } 627 rcu_read_unlock(); 628 rcu_sysrq_end(); 629 630 suppress_printk = orig_suppress_printk; 631} 632 633void handle_sysrq(int key) 634{ 635 if (sysrq_on()) 636 __handle_sysrq(key, true); 637} 638EXPORT_SYMBOL(handle_sysrq); 639 640#ifdef CONFIG_INPUT 641static int sysrq_reset_downtime_ms; 642 643/* Simple translation table for the SysRq keys */ 644static const unsigned char sysrq_xlate[KEY_CNT] = 645 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 646 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 647 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 648 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 649 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 650 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 651 "\r\000/"; /* 0x60 - 0x6f */ 652 653struct sysrq_state { 654 struct input_handle handle; 655 struct work_struct reinject_work; 656 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 657 unsigned int alt; 658 unsigned int alt_use; 659 unsigned int shift; 660 unsigned int shift_use; 661 bool active; 662 bool need_reinject; 663 bool reinjecting; 664 665 /* reset sequence handling */ 666 bool reset_canceled; 667 bool reset_requested; 668 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 669 int reset_seq_len; 670 int reset_seq_cnt; 671 int reset_seq_version; 672 struct timer_list keyreset_timer; 673}; 674 675#define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 676static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 677static unsigned int sysrq_reset_seq_len; 678static unsigned int sysrq_reset_seq_version = 1; 679 680static void sysrq_parse_reset_sequence(struct sysrq_state *state) 681{ 682 int i; 683 unsigned short key; 684 685 state->reset_seq_cnt = 0; 686 687 for (i = 0; i < sysrq_reset_seq_len; i++) { 688 key = sysrq_reset_seq[i]; 689 690 if (key == KEY_RESERVED || key > KEY_MAX) 691 break; 692 693 __set_bit(key, state->reset_keybit); 694 state->reset_seq_len++; 695 696 if (test_bit(key, state->key_down)) 697 state->reset_seq_cnt++; 698 } 699 700 /* Disable reset until old keys are not released */ 701 state->reset_canceled = state->reset_seq_cnt != 0; 702 703 state->reset_seq_version = sysrq_reset_seq_version; 704} 705 706static void sysrq_do_reset(struct timer_list *t) 707{ 708 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 709 710 state->reset_requested = true; 711 712 orderly_reboot(); 713} 714 715static void sysrq_handle_reset_request(struct sysrq_state *state) 716{ 717 if (state->reset_requested) 718 __handle_sysrq(sysrq_xlate[KEY_B], false); 719 720 if (sysrq_reset_downtime_ms) 721 mod_timer(&state->keyreset_timer, 722 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 723 else 724 sysrq_do_reset(&state->keyreset_timer); 725} 726 727static void sysrq_detect_reset_sequence(struct sysrq_state *state, 728 unsigned int code, int value) 729{ 730 if (!test_bit(code, state->reset_keybit)) { 731 /* 732 * Pressing any key _not_ in reset sequence cancels 733 * the reset sequence. Also cancelling the timer in 734 * case additional keys were pressed after a reset 735 * has been requested. 736 */ 737 if (value && state->reset_seq_cnt) { 738 state->reset_canceled = true; 739 del_timer(&state->keyreset_timer); 740 } 741 } else if (value == 0) { 742 /* 743 * Key release - all keys in the reset sequence need 744 * to be pressed and held for the reset timeout 745 * to hold. 746 */ 747 del_timer(&state->keyreset_timer); 748 749 if (--state->reset_seq_cnt == 0) 750 state->reset_canceled = false; 751 } else if (value == 1) { 752 /* key press, not autorepeat */ 753 if (++state->reset_seq_cnt == state->reset_seq_len && 754 !state->reset_canceled) { 755 sysrq_handle_reset_request(state); 756 } 757 } 758} 759 760#ifdef CONFIG_OF 761static void sysrq_of_get_keyreset_config(void) 762{ 763 u32 key; 764 struct device_node *np; 765 struct property *prop; 766 const __be32 *p; 767 768 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 769 if (!np) { 770 pr_debug("No sysrq node found"); 771 return; 772 } 773 774 /* Reset in case a __weak definition was present */ 775 sysrq_reset_seq_len = 0; 776 777 of_property_for_each_u32(np, "keyset", prop, p, key) { 778 if (key == KEY_RESERVED || key > KEY_MAX || 779 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 780 break; 781 782 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 783 } 784 785 /* Get reset timeout if any. */ 786 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 787 788 of_node_put(np); 789} 790#else 791static void sysrq_of_get_keyreset_config(void) 792{ 793} 794#endif 795 796static void sysrq_reinject_alt_sysrq(struct work_struct *work) 797{ 798 struct sysrq_state *sysrq = 799 container_of(work, struct sysrq_state, reinject_work); 800 struct input_handle *handle = &sysrq->handle; 801 unsigned int alt_code = sysrq->alt_use; 802 803 if (sysrq->need_reinject) { 804 /* we do not want the assignment to be reordered */ 805 sysrq->reinjecting = true; 806 mb(); 807 808 /* Simulate press and release of Alt + SysRq */ 809 input_inject_event(handle, EV_KEY, alt_code, 1); 810 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 811 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 812 813 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 814 input_inject_event(handle, EV_KEY, alt_code, 0); 815 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 816 817 mb(); 818 sysrq->reinjecting = false; 819 } 820} 821 822static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 823 unsigned int code, int value) 824{ 825 bool was_active = sysrq->active; 826 bool suppress; 827 828 switch (code) { 829 830 case KEY_LEFTALT: 831 case KEY_RIGHTALT: 832 if (!value) { 833 /* One of ALTs is being released */ 834 if (sysrq->active && code == sysrq->alt_use) 835 sysrq->active = false; 836 837 sysrq->alt = KEY_RESERVED; 838 839 } else if (value != 2) { 840 sysrq->alt = code; 841 sysrq->need_reinject = false; 842 } 843 break; 844 845 case KEY_LEFTSHIFT: 846 case KEY_RIGHTSHIFT: 847 if (!value) 848 sysrq->shift = KEY_RESERVED; 849 else if (value != 2) 850 sysrq->shift = code; 851 break; 852 853 case KEY_SYSRQ: 854 if (value == 1 && sysrq->alt != KEY_RESERVED) { 855 sysrq->active = true; 856 sysrq->alt_use = sysrq->alt; 857 /* either RESERVED (for released) or actual code */ 858 sysrq->shift_use = sysrq->shift; 859 /* 860 * If nothing else will be pressed we'll need 861 * to re-inject Alt-SysRq keysroke. 862 */ 863 sysrq->need_reinject = true; 864 } 865 866 /* 867 * Pretend that sysrq was never pressed at all. This 868 * is needed to properly handle KGDB which will try 869 * to release all keys after exiting debugger. If we 870 * do not clear key bit it KGDB will end up sending 871 * release events for Alt and SysRq, potentially 872 * triggering print screen function. 873 */ 874 if (sysrq->active) 875 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 876 877 break; 878 879 default: 880 if (sysrq->active && value && value != 2) { 881 unsigned char c = sysrq_xlate[code]; 882 883 sysrq->need_reinject = false; 884 if (sysrq->shift_use != KEY_RESERVED) 885 c = toupper(c); 886 __handle_sysrq(c, true); 887 } 888 break; 889 } 890 891 suppress = sysrq->active; 892 893 if (!sysrq->active) { 894 895 /* 896 * See if reset sequence has changed since the last time. 897 */ 898 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 899 sysrq_parse_reset_sequence(sysrq); 900 901 /* 902 * If we are not suppressing key presses keep track of 903 * keyboard state so we can release keys that have been 904 * pressed before entering SysRq mode. 905 */ 906 if (value) 907 set_bit(code, sysrq->key_down); 908 else 909 clear_bit(code, sysrq->key_down); 910 911 if (was_active) 912 schedule_work(&sysrq->reinject_work); 913 914 /* Check for reset sequence */ 915 sysrq_detect_reset_sequence(sysrq, code, value); 916 917 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 918 /* 919 * Pass on release events for keys that was pressed before 920 * entering SysRq mode. 921 */ 922 suppress = false; 923 } 924 925 return suppress; 926} 927 928static bool sysrq_filter(struct input_handle *handle, 929 unsigned int type, unsigned int code, int value) 930{ 931 struct sysrq_state *sysrq = handle->private; 932 bool suppress; 933 934 /* 935 * Do not filter anything if we are in the process of re-injecting 936 * Alt+SysRq combination. 937 */ 938 if (sysrq->reinjecting) 939 return false; 940 941 switch (type) { 942 943 case EV_SYN: 944 suppress = false; 945 break; 946 947 case EV_KEY: 948 suppress = sysrq_handle_keypress(sysrq, code, value); 949 break; 950 951 default: 952 suppress = sysrq->active; 953 break; 954 } 955 956 return suppress; 957} 958 959static int sysrq_connect(struct input_handler *handler, 960 struct input_dev *dev, 961 const struct input_device_id *id) 962{ 963 struct sysrq_state *sysrq; 964 int error; 965 966 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 967 if (!sysrq) 968 return -ENOMEM; 969 970 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 971 972 sysrq->handle.dev = dev; 973 sysrq->handle.handler = handler; 974 sysrq->handle.name = "sysrq"; 975 sysrq->handle.private = sysrq; 976 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 977 978 error = input_register_handle(&sysrq->handle); 979 if (error) { 980 pr_err("Failed to register input sysrq handler, error %d\n", 981 error); 982 goto err_free; 983 } 984 985 error = input_open_device(&sysrq->handle); 986 if (error) { 987 pr_err("Failed to open input device, error %d\n", error); 988 goto err_unregister; 989 } 990 991 return 0; 992 993 err_unregister: 994 input_unregister_handle(&sysrq->handle); 995 err_free: 996 kfree(sysrq); 997 return error; 998} 999 1000static void sysrq_disconnect(struct input_handle *handle) 1001{ 1002 struct sysrq_state *sysrq = handle->private; 1003 1004 input_close_device(handle); 1005 cancel_work_sync(&sysrq->reinject_work); 1006 del_timer_sync(&sysrq->keyreset_timer); 1007 input_unregister_handle(handle); 1008 kfree(sysrq); 1009} 1010 1011/* 1012 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 1013 * keyboards have SysRq key predefined and so user may add it to keymap 1014 * later, but we expect all such keyboards to have left alt. 1015 */ 1016static const struct input_device_id sysrq_ids[] = { 1017 { 1018 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 1019 INPUT_DEVICE_ID_MATCH_KEYBIT, 1020 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 1021 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 1022 }, 1023 { }, 1024}; 1025 1026static struct input_handler sysrq_handler = { 1027 .filter = sysrq_filter, 1028 .connect = sysrq_connect, 1029 .disconnect = sysrq_disconnect, 1030 .name = "sysrq", 1031 .id_table = sysrq_ids, 1032}; 1033 1034static inline void sysrq_register_handler(void) 1035{ 1036 int error; 1037 1038 sysrq_of_get_keyreset_config(); 1039 1040 error = input_register_handler(&sysrq_handler); 1041 if (error) 1042 pr_err("Failed to register input handler, error %d", error); 1043} 1044 1045static inline void sysrq_unregister_handler(void) 1046{ 1047 input_unregister_handler(&sysrq_handler); 1048} 1049 1050static int sysrq_reset_seq_param_set(const char *buffer, 1051 const struct kernel_param *kp) 1052{ 1053 unsigned long val; 1054 int error; 1055 1056 error = kstrtoul(buffer, 0, &val); 1057 if (error < 0) 1058 return error; 1059 1060 if (val > KEY_MAX) 1061 return -EINVAL; 1062 1063 *((unsigned short *)kp->arg) = val; 1064 sysrq_reset_seq_version++; 1065 1066 return 0; 1067} 1068 1069static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1070 .get = param_get_ushort, 1071 .set = sysrq_reset_seq_param_set, 1072}; 1073 1074#define param_check_sysrq_reset_seq(name, p) \ 1075 __param_check(name, p, unsigned short) 1076 1077/* 1078 * not really modular, but the easiest way to keep compat with existing 1079 * bootargs behaviour is to continue using module_param here. 1080 */ 1081module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1082 &sysrq_reset_seq_len, 0644); 1083 1084module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1085 1086#else 1087 1088static inline void sysrq_register_handler(void) 1089{ 1090} 1091 1092static inline void sysrq_unregister_handler(void) 1093{ 1094} 1095 1096#endif /* CONFIG_INPUT */ 1097 1098int sysrq_toggle_support(int enable_mask) 1099{ 1100 bool was_enabled = sysrq_on(); 1101 1102 sysrq_enabled = enable_mask; 1103 1104 if (was_enabled != sysrq_on()) { 1105 if (sysrq_on()) 1106 sysrq_register_handler(); 1107 else 1108 sysrq_unregister_handler(); 1109 } 1110 1111 return 0; 1112} 1113EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1114 1115static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p, 1116 const struct sysrq_key_op *remove_op_p) 1117{ 1118 int retval; 1119 1120 spin_lock(&sysrq_key_table_lock); 1121 if (__sysrq_get_key_op(key) == remove_op_p) { 1122 __sysrq_put_key_op(key, insert_op_p); 1123 retval = 0; 1124 } else { 1125 retval = -1; 1126 } 1127 spin_unlock(&sysrq_key_table_lock); 1128 1129 /* 1130 * A concurrent __handle_sysrq either got the old op or the new op. 1131 * Wait for it to go away before returning, so the code for an old 1132 * op is not freed (eg. on module unload) while it is in use. 1133 */ 1134 synchronize_rcu(); 1135 1136 return retval; 1137} 1138 1139int register_sysrq_key(int key, const struct sysrq_key_op *op_p) 1140{ 1141 return __sysrq_swap_key_ops(key, op_p, NULL); 1142} 1143EXPORT_SYMBOL(register_sysrq_key); 1144 1145int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p) 1146{ 1147 return __sysrq_swap_key_ops(key, NULL, op_p); 1148} 1149EXPORT_SYMBOL(unregister_sysrq_key); 1150 1151#ifdef CONFIG_PROC_FS 1152 1153static DEFINE_MUTEX(sysrq_mutex); 1154 1155/* 1156 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1157 */ 1158static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1159 size_t count, loff_t *ppos) 1160{ 1161 if (count) { 1162 char c; 1163 1164 if (get_user(c, buf)) 1165 return -EFAULT; 1166 1167 mutex_lock(&sysrq_mutex); 1168 __handle_sysrq(c, false); 1169 mutex_unlock(&sysrq_mutex); 1170 } 1171 1172 return count; 1173} 1174 1175static const struct proc_ops sysrq_trigger_proc_ops = { 1176 .proc_write = write_sysrq_trigger, 1177 .proc_lseek = noop_llseek, 1178}; 1179 1180static void sysrq_init_procfs(void) 1181{ 1182 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1183 &sysrq_trigger_proc_ops)) 1184 pr_err("Failed to register proc interface\n"); 1185} 1186 1187#else 1188 1189static inline void sysrq_init_procfs(void) 1190{ 1191} 1192 1193#endif /* CONFIG_PROC_FS */ 1194 1195static int __init sysrq_init(void) 1196{ 1197 sysrq_init_procfs(); 1198 1199 if (sysrq_on()) 1200 sysrq_register_handler(); 1201 1202 return 0; 1203} 1204device_initcall(sysrq_init); 1205