1/* 2 * Linux Magic System Request Key Hacks 3 * 4 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz> 5 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz> 6 * 7 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com> 8 * overhauled to use key registration 9 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies 10 * 11 * Copyright (c) 2010 Dmitry Torokhov 12 * Input handler conversion 13 */ 14 15#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 16 17#include <linux/sched.h> 18#include <linux/sched/rt.h> 19#include <linux/interrupt.h> 20#include <linux/mm.h> 21#include <linux/fs.h> 22#include <linux/mount.h> 23#include <linux/kdev_t.h> 24#include <linux/major.h> 25#include <linux/reboot.h> 26#include <linux/sysrq.h> 27#include <linux/kbd_kern.h> 28#include <linux/proc_fs.h> 29#include <linux/nmi.h> 30#include <linux/quotaops.h> 31#include <linux/perf_event.h> 32#include <linux/kernel.h> 33#include <linux/module.h> 34#include <linux/suspend.h> 35#include <linux/writeback.h> 36#include <linux/swap.h> 37#include <linux/spinlock.h> 38#include <linux/vt_kern.h> 39#include <linux/workqueue.h> 40#include <linux/hrtimer.h> 41#include <linux/oom.h> 42#include <linux/slab.h> 43#include <linux/input.h> 44#include <linux/uaccess.h> 45#include <linux/moduleparam.h> 46#include <linux/jiffies.h> 47#include <linux/syscalls.h> 48#include <linux/of.h> 49#include <linux/rcupdate.h> 50 51#include <asm/ptrace.h> 52#include <asm/irq_regs.h> 53 54/* Whether we react on sysrq keys or just ignore them */ 55static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; 56static bool __read_mostly sysrq_always_enabled; 57 58static bool sysrq_on(void) 59{ 60 return sysrq_enabled || sysrq_always_enabled; 61} 62 63/* 64 * A value of 1 means 'all', other nonzero values are an op mask: 65 */ 66static bool sysrq_on_mask(int mask) 67{ 68 return sysrq_always_enabled || 69 sysrq_enabled == 1 || 70 (sysrq_enabled & mask); 71} 72 73static int __init sysrq_always_enabled_setup(char *str) 74{ 75 sysrq_always_enabled = true; 76 pr_info("sysrq always enabled.\n"); 77 78 return 1; 79} 80 81__setup("sysrq_always_enabled", sysrq_always_enabled_setup); 82 83 84static void sysrq_handle_loglevel(int key) 85{ 86 int i; 87 88 i = key - '0'; 89 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 90 pr_info("Loglevel set to %d\n", i); 91 console_loglevel = i; 92} 93static struct sysrq_key_op sysrq_loglevel_op = { 94 .handler = sysrq_handle_loglevel, 95 .help_msg = "loglevel(0-9)", 96 .action_msg = "Changing Loglevel", 97 .enable_mask = SYSRQ_ENABLE_LOG, 98}; 99 100#ifdef CONFIG_VT 101static void sysrq_handle_SAK(int key) 102{ 103 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 104 schedule_work(SAK_work); 105} 106static struct sysrq_key_op sysrq_SAK_op = { 107 .handler = sysrq_handle_SAK, 108 .help_msg = "sak(k)", 109 .action_msg = "SAK", 110 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 111}; 112#else 113#define sysrq_SAK_op (*(struct sysrq_key_op *)NULL) 114#endif 115 116#ifdef CONFIG_VT 117static void sysrq_handle_unraw(int key) 118{ 119 vt_reset_unicode(fg_console); 120} 121 122static struct sysrq_key_op sysrq_unraw_op = { 123 .handler = sysrq_handle_unraw, 124 .help_msg = "unraw(r)", 125 .action_msg = "Keyboard mode set to system default", 126 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 127}; 128#else 129#define sysrq_unraw_op (*(struct sysrq_key_op *)NULL) 130#endif /* CONFIG_VT */ 131 132static void sysrq_handle_crash(int key) 133{ 134 char *killer = NULL; 135 136 panic_on_oops = 1; /* force panic */ 137 wmb(); 138 *killer = 1; 139} 140static struct sysrq_key_op sysrq_crash_op = { 141 .handler = sysrq_handle_crash, 142 .help_msg = "crash(c)", 143 .action_msg = "Trigger a crash", 144 .enable_mask = SYSRQ_ENABLE_DUMP, 145}; 146 147static void sysrq_handle_reboot(int key) 148{ 149 lockdep_off(); 150 local_irq_enable(); 151 emergency_restart(); 152} 153static struct sysrq_key_op sysrq_reboot_op = { 154 .handler = sysrq_handle_reboot, 155 .help_msg = "reboot(b)", 156 .action_msg = "Resetting", 157 .enable_mask = SYSRQ_ENABLE_BOOT, 158}; 159 160static void sysrq_handle_sync(int key) 161{ 162 emergency_sync(); 163} 164static struct sysrq_key_op sysrq_sync_op = { 165 .handler = sysrq_handle_sync, 166 .help_msg = "sync(s)", 167 .action_msg = "Emergency Sync", 168 .enable_mask = SYSRQ_ENABLE_SYNC, 169}; 170 171static void sysrq_handle_show_timers(int key) 172{ 173 sysrq_timer_list_show(); 174} 175 176static struct sysrq_key_op sysrq_show_timers_op = { 177 .handler = sysrq_handle_show_timers, 178 .help_msg = "show-all-timers(q)", 179 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 180}; 181 182static void sysrq_handle_mountro(int key) 183{ 184 emergency_remount(); 185} 186static struct sysrq_key_op sysrq_mountro_op = { 187 .handler = sysrq_handle_mountro, 188 .help_msg = "unmount(u)", 189 .action_msg = "Emergency Remount R/O", 190 .enable_mask = SYSRQ_ENABLE_REMOUNT, 191}; 192 193#ifdef CONFIG_LOCKDEP 194static void sysrq_handle_showlocks(int key) 195{ 196 debug_show_all_locks(); 197} 198 199static struct sysrq_key_op sysrq_showlocks_op = { 200 .handler = sysrq_handle_showlocks, 201 .help_msg = "show-all-locks(d)", 202 .action_msg = "Show Locks Held", 203}; 204#else 205#define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 206#endif 207 208#ifdef CONFIG_SMP 209static DEFINE_SPINLOCK(show_lock); 210 211static void showacpu(void *dummy) 212{ 213 unsigned long flags; 214 215 /* Idle CPUs have no interesting backtrace. */ 216 if (idle_cpu(smp_processor_id())) 217 return; 218 219 spin_lock_irqsave(&show_lock, flags); 220 pr_info("CPU%d:\n", smp_processor_id()); 221 show_stack(NULL, NULL); 222 spin_unlock_irqrestore(&show_lock, flags); 223} 224 225static void sysrq_showregs_othercpus(struct work_struct *dummy) 226{ 227 smp_call_function(showacpu, NULL, 0); 228} 229 230static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 231 232static void sysrq_handle_showallcpus(int key) 233{ 234 /* 235 * Fall back to the workqueue based printing if the 236 * backtrace printing did not succeed or the 237 * architecture has no support for it: 238 */ 239 if (!trigger_all_cpu_backtrace()) { 240 struct pt_regs *regs = get_irq_regs(); 241 242 if (regs) { 243 pr_info("CPU%d:\n", smp_processor_id()); 244 show_regs(regs); 245 } 246 schedule_work(&sysrq_showallcpus); 247 } 248} 249 250static struct sysrq_key_op sysrq_showallcpus_op = { 251 .handler = sysrq_handle_showallcpus, 252 .help_msg = "show-backtrace-all-active-cpus(l)", 253 .action_msg = "Show backtrace of all active CPUs", 254 .enable_mask = SYSRQ_ENABLE_DUMP, 255}; 256#endif 257 258static void sysrq_handle_showregs(int key) 259{ 260 struct pt_regs *regs = get_irq_regs(); 261 if (regs) 262 show_regs(regs); 263 perf_event_print_debug(); 264} 265static struct sysrq_key_op sysrq_showregs_op = { 266 .handler = sysrq_handle_showregs, 267 .help_msg = "show-registers(p)", 268 .action_msg = "Show Regs", 269 .enable_mask = SYSRQ_ENABLE_DUMP, 270}; 271 272static void sysrq_handle_showstate(int key) 273{ 274 show_state(); 275 show_workqueue_state(); 276} 277static struct sysrq_key_op sysrq_showstate_op = { 278 .handler = sysrq_handle_showstate, 279 .help_msg = "show-task-states(t)", 280 .action_msg = "Show State", 281 .enable_mask = SYSRQ_ENABLE_DUMP, 282}; 283 284static void sysrq_handle_showstate_blocked(int key) 285{ 286 show_state_filter(TASK_UNINTERRUPTIBLE); 287} 288static struct sysrq_key_op sysrq_showstate_blocked_op = { 289 .handler = sysrq_handle_showstate_blocked, 290 .help_msg = "show-blocked-tasks(w)", 291 .action_msg = "Show Blocked State", 292 .enable_mask = SYSRQ_ENABLE_DUMP, 293}; 294 295#ifdef CONFIG_TRACING 296#include <linux/ftrace.h> 297 298static void sysrq_ftrace_dump(int key) 299{ 300 ftrace_dump(DUMP_ALL); 301} 302static struct sysrq_key_op sysrq_ftrace_dump_op = { 303 .handler = sysrq_ftrace_dump, 304 .help_msg = "dump-ftrace-buffer(z)", 305 .action_msg = "Dump ftrace buffer", 306 .enable_mask = SYSRQ_ENABLE_DUMP, 307}; 308#else 309#define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 310#endif 311 312static void sysrq_handle_showmem(int key) 313{ 314 show_mem(0); 315} 316static struct sysrq_key_op sysrq_showmem_op = { 317 .handler = sysrq_handle_showmem, 318 .help_msg = "show-memory-usage(m)", 319 .action_msg = "Show Memory", 320 .enable_mask = SYSRQ_ENABLE_DUMP, 321}; 322 323/* 324 * Signal sysrq helper function. Sends a signal to all user processes. 325 */ 326static void send_sig_all(int sig) 327{ 328 struct task_struct *p; 329 330 read_lock(&tasklist_lock); 331 for_each_process(p) { 332 if (p->flags & PF_KTHREAD) 333 continue; 334 if (is_global_init(p)) 335 continue; 336 337 do_send_sig_info(sig, SEND_SIG_FORCED, p, true); 338 } 339 read_unlock(&tasklist_lock); 340} 341 342static void sysrq_handle_term(int key) 343{ 344 send_sig_all(SIGTERM); 345 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 346} 347static struct sysrq_key_op sysrq_term_op = { 348 .handler = sysrq_handle_term, 349 .help_msg = "terminate-all-tasks(e)", 350 .action_msg = "Terminate All Tasks", 351 .enable_mask = SYSRQ_ENABLE_SIGNAL, 352}; 353 354static void moom_callback(struct work_struct *ignored) 355{ 356 if (!out_of_memory(node_zonelist(first_memory_node, GFP_KERNEL), 357 GFP_KERNEL, 0, NULL, true)) 358 pr_info("OOM request ignored because killer is disabled\n"); 359} 360 361static DECLARE_WORK(moom_work, moom_callback); 362 363static void sysrq_handle_moom(int key) 364{ 365 schedule_work(&moom_work); 366} 367static struct sysrq_key_op sysrq_moom_op = { 368 .handler = sysrq_handle_moom, 369 .help_msg = "memory-full-oom-kill(f)", 370 .action_msg = "Manual OOM execution", 371 .enable_mask = SYSRQ_ENABLE_SIGNAL, 372}; 373 374#ifdef CONFIG_BLOCK 375static void sysrq_handle_thaw(int key) 376{ 377 emergency_thaw_all(); 378} 379static struct sysrq_key_op sysrq_thaw_op = { 380 .handler = sysrq_handle_thaw, 381 .help_msg = "thaw-filesystems(j)", 382 .action_msg = "Emergency Thaw of all frozen filesystems", 383 .enable_mask = SYSRQ_ENABLE_SIGNAL, 384}; 385#endif 386 387static void sysrq_handle_kill(int key) 388{ 389 send_sig_all(SIGKILL); 390 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 391} 392static struct sysrq_key_op sysrq_kill_op = { 393 .handler = sysrq_handle_kill, 394 .help_msg = "kill-all-tasks(i)", 395 .action_msg = "Kill All Tasks", 396 .enable_mask = SYSRQ_ENABLE_SIGNAL, 397}; 398 399static void sysrq_handle_unrt(int key) 400{ 401 normalize_rt_tasks(); 402} 403static struct sysrq_key_op sysrq_unrt_op = { 404 .handler = sysrq_handle_unrt, 405 .help_msg = "nice-all-RT-tasks(n)", 406 .action_msg = "Nice All RT Tasks", 407 .enable_mask = SYSRQ_ENABLE_RTNICE, 408}; 409 410/* Key Operations table and lock */ 411static DEFINE_SPINLOCK(sysrq_key_table_lock); 412 413static struct sysrq_key_op *sysrq_key_table[36] = { 414 &sysrq_loglevel_op, /* 0 */ 415 &sysrq_loglevel_op, /* 1 */ 416 &sysrq_loglevel_op, /* 2 */ 417 &sysrq_loglevel_op, /* 3 */ 418 &sysrq_loglevel_op, /* 4 */ 419 &sysrq_loglevel_op, /* 5 */ 420 &sysrq_loglevel_op, /* 6 */ 421 &sysrq_loglevel_op, /* 7 */ 422 &sysrq_loglevel_op, /* 8 */ 423 &sysrq_loglevel_op, /* 9 */ 424 425 /* 426 * a: Don't use for system provided sysrqs, it is handled specially on 427 * sparc and will never arrive. 428 */ 429 NULL, /* a */ 430 &sysrq_reboot_op, /* b */ 431 &sysrq_crash_op, /* c & ibm_emac driver debug */ 432 &sysrq_showlocks_op, /* d */ 433 &sysrq_term_op, /* e */ 434 &sysrq_moom_op, /* f */ 435 /* g: May be registered for the kernel debugger */ 436 NULL, /* g */ 437 NULL, /* h - reserved for help */ 438 &sysrq_kill_op, /* i */ 439#ifdef CONFIG_BLOCK 440 &sysrq_thaw_op, /* j */ 441#else 442 NULL, /* j */ 443#endif 444 &sysrq_SAK_op, /* k */ 445#ifdef CONFIG_SMP 446 &sysrq_showallcpus_op, /* l */ 447#else 448 NULL, /* l */ 449#endif 450 &sysrq_showmem_op, /* m */ 451 &sysrq_unrt_op, /* n */ 452 /* o: This will often be registered as 'Off' at init time */ 453 NULL, /* o */ 454 &sysrq_showregs_op, /* p */ 455 &sysrq_show_timers_op, /* q */ 456 &sysrq_unraw_op, /* r */ 457 &sysrq_sync_op, /* s */ 458 &sysrq_showstate_op, /* t */ 459 &sysrq_mountro_op, /* u */ 460 /* v: May be registered for frame buffer console restore */ 461 NULL, /* v */ 462 &sysrq_showstate_blocked_op, /* w */ 463 /* x: May be registered on ppc/powerpc for xmon */ 464 /* x: May be registered on sparc64 for global PMU dump */ 465 NULL, /* x */ 466 /* y: May be registered on sparc64 for global register dump */ 467 NULL, /* y */ 468 &sysrq_ftrace_dump_op, /* z */ 469}; 470 471/* key2index calculation, -1 on invalid index */ 472static int sysrq_key_table_key2index(int key) 473{ 474 int retval; 475 476 if ((key >= '0') && (key <= '9')) 477 retval = key - '0'; 478 else if ((key >= 'a') && (key <= 'z')) 479 retval = key + 10 - 'a'; 480 else 481 retval = -1; 482 return retval; 483} 484 485/* 486 * get and put functions for the table, exposed to modules. 487 */ 488struct sysrq_key_op *__sysrq_get_key_op(int key) 489{ 490 struct sysrq_key_op *op_p = NULL; 491 int i; 492 493 i = sysrq_key_table_key2index(key); 494 if (i != -1) 495 op_p = sysrq_key_table[i]; 496 497 return op_p; 498} 499 500static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 501{ 502 int i = sysrq_key_table_key2index(key); 503 504 if (i != -1) 505 sysrq_key_table[i] = op_p; 506} 507 508void __handle_sysrq(int key, bool check_mask) 509{ 510 struct sysrq_key_op *op_p; 511 int orig_log_level; 512 int i; 513 514 rcu_sysrq_start(); 515 rcu_read_lock(); 516 /* 517 * Raise the apparent loglevel to maximum so that the sysrq header 518 * is shown to provide the user with positive feedback. We do not 519 * simply emit this at KERN_EMERG as that would change message 520 * routing in the consumers of /proc/kmsg. 521 */ 522 orig_log_level = console_loglevel; 523 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 524 pr_info("SysRq : "); 525 526 op_p = __sysrq_get_key_op(key); 527 if (op_p) { 528 /* 529 * Should we check for enabled operations (/proc/sysrq-trigger 530 * should not) and is the invoked operation enabled? 531 */ 532 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 533 pr_cont("%s\n", op_p->action_msg); 534 console_loglevel = orig_log_level; 535 op_p->handler(key); 536 } else { 537 pr_cont("This sysrq operation is disabled.\n"); 538 } 539 } else { 540 pr_cont("HELP : "); 541 /* Only print the help msg once per handler */ 542 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 543 if (sysrq_key_table[i]) { 544 int j; 545 546 for (j = 0; sysrq_key_table[i] != 547 sysrq_key_table[j]; j++) 548 ; 549 if (j != i) 550 continue; 551 pr_cont("%s ", sysrq_key_table[i]->help_msg); 552 } 553 } 554 pr_cont("\n"); 555 console_loglevel = orig_log_level; 556 } 557 rcu_read_unlock(); 558 rcu_sysrq_end(); 559} 560 561void handle_sysrq(int key) 562{ 563 if (sysrq_on()) 564 __handle_sysrq(key, true); 565} 566EXPORT_SYMBOL(handle_sysrq); 567 568#ifdef CONFIG_INPUT 569static int sysrq_reset_downtime_ms; 570 571/* Simple translation table for the SysRq keys */ 572static const unsigned char sysrq_xlate[KEY_CNT] = 573 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 574 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 575 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 576 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 577 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 578 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 579 "\r\000/"; /* 0x60 - 0x6f */ 580 581struct sysrq_state { 582 struct input_handle handle; 583 struct work_struct reinject_work; 584 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 585 unsigned int alt; 586 unsigned int alt_use; 587 bool active; 588 bool need_reinject; 589 bool reinjecting; 590 591 /* reset sequence handling */ 592 bool reset_canceled; 593 bool reset_requested; 594 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 595 int reset_seq_len; 596 int reset_seq_cnt; 597 int reset_seq_version; 598 struct timer_list keyreset_timer; 599}; 600 601#define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 602static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 603static unsigned int sysrq_reset_seq_len; 604static unsigned int sysrq_reset_seq_version = 1; 605 606static void sysrq_parse_reset_sequence(struct sysrq_state *state) 607{ 608 int i; 609 unsigned short key; 610 611 state->reset_seq_cnt = 0; 612 613 for (i = 0; i < sysrq_reset_seq_len; i++) { 614 key = sysrq_reset_seq[i]; 615 616 if (key == KEY_RESERVED || key > KEY_MAX) 617 break; 618 619 __set_bit(key, state->reset_keybit); 620 state->reset_seq_len++; 621 622 if (test_bit(key, state->key_down)) 623 state->reset_seq_cnt++; 624 } 625 626 /* Disable reset until old keys are not released */ 627 state->reset_canceled = state->reset_seq_cnt != 0; 628 629 state->reset_seq_version = sysrq_reset_seq_version; 630} 631 632static void sysrq_do_reset(unsigned long _state) 633{ 634 struct sysrq_state *state = (struct sysrq_state *) _state; 635 636 state->reset_requested = true; 637 638 sys_sync(); 639 kernel_restart(NULL); 640} 641 642static void sysrq_handle_reset_request(struct sysrq_state *state) 643{ 644 if (state->reset_requested) 645 __handle_sysrq(sysrq_xlate[KEY_B], false); 646 647 if (sysrq_reset_downtime_ms) 648 mod_timer(&state->keyreset_timer, 649 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 650 else 651 sysrq_do_reset((unsigned long)state); 652} 653 654static void sysrq_detect_reset_sequence(struct sysrq_state *state, 655 unsigned int code, int value) 656{ 657 if (!test_bit(code, state->reset_keybit)) { 658 /* 659 * Pressing any key _not_ in reset sequence cancels 660 * the reset sequence. Also cancelling the timer in 661 * case additional keys were pressed after a reset 662 * has been requested. 663 */ 664 if (value && state->reset_seq_cnt) { 665 state->reset_canceled = true; 666 del_timer(&state->keyreset_timer); 667 } 668 } else if (value == 0) { 669 /* 670 * Key release - all keys in the reset sequence need 671 * to be pressed and held for the reset timeout 672 * to hold. 673 */ 674 del_timer(&state->keyreset_timer); 675 676 if (--state->reset_seq_cnt == 0) 677 state->reset_canceled = false; 678 } else if (value == 1) { 679 /* key press, not autorepeat */ 680 if (++state->reset_seq_cnt == state->reset_seq_len && 681 !state->reset_canceled) { 682 sysrq_handle_reset_request(state); 683 } 684 } 685} 686 687#ifdef CONFIG_OF 688static void sysrq_of_get_keyreset_config(void) 689{ 690 u32 key; 691 struct device_node *np; 692 struct property *prop; 693 const __be32 *p; 694 695 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 696 if (!np) { 697 pr_debug("No sysrq node found"); 698 return; 699 } 700 701 /* Reset in case a __weak definition was present */ 702 sysrq_reset_seq_len = 0; 703 704 of_property_for_each_u32(np, "keyset", prop, p, key) { 705 if (key == KEY_RESERVED || key > KEY_MAX || 706 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 707 break; 708 709 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 710 } 711 712 /* Get reset timeout if any. */ 713 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 714} 715#else 716static void sysrq_of_get_keyreset_config(void) 717{ 718} 719#endif 720 721static void sysrq_reinject_alt_sysrq(struct work_struct *work) 722{ 723 struct sysrq_state *sysrq = 724 container_of(work, struct sysrq_state, reinject_work); 725 struct input_handle *handle = &sysrq->handle; 726 unsigned int alt_code = sysrq->alt_use; 727 728 if (sysrq->need_reinject) { 729 /* we do not want the assignment to be reordered */ 730 sysrq->reinjecting = true; 731 mb(); 732 733 /* Simulate press and release of Alt + SysRq */ 734 input_inject_event(handle, EV_KEY, alt_code, 1); 735 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 736 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 737 738 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 739 input_inject_event(handle, EV_KEY, alt_code, 0); 740 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 741 742 mb(); 743 sysrq->reinjecting = false; 744 } 745} 746 747static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 748 unsigned int code, int value) 749{ 750 bool was_active = sysrq->active; 751 bool suppress; 752 753 switch (code) { 754 755 case KEY_LEFTALT: 756 case KEY_RIGHTALT: 757 if (!value) { 758 /* One of ALTs is being released */ 759 if (sysrq->active && code == sysrq->alt_use) 760 sysrq->active = false; 761 762 sysrq->alt = KEY_RESERVED; 763 764 } else if (value != 2) { 765 sysrq->alt = code; 766 sysrq->need_reinject = false; 767 } 768 break; 769 770 case KEY_SYSRQ: 771 if (value == 1 && sysrq->alt != KEY_RESERVED) { 772 sysrq->active = true; 773 sysrq->alt_use = sysrq->alt; 774 /* 775 * If nothing else will be pressed we'll need 776 * to re-inject Alt-SysRq keysroke. 777 */ 778 sysrq->need_reinject = true; 779 } 780 781 /* 782 * Pretend that sysrq was never pressed at all. This 783 * is needed to properly handle KGDB which will try 784 * to release all keys after exiting debugger. If we 785 * do not clear key bit it KGDB will end up sending 786 * release events for Alt and SysRq, potentially 787 * triggering print screen function. 788 */ 789 if (sysrq->active) 790 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 791 792 break; 793 794 default: 795 if (sysrq->active && value && value != 2) { 796 sysrq->need_reinject = false; 797 __handle_sysrq(sysrq_xlate[code], true); 798 } 799 break; 800 } 801 802 suppress = sysrq->active; 803 804 if (!sysrq->active) { 805 806 /* 807 * See if reset sequence has changed since the last time. 808 */ 809 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 810 sysrq_parse_reset_sequence(sysrq); 811 812 /* 813 * If we are not suppressing key presses keep track of 814 * keyboard state so we can release keys that have been 815 * pressed before entering SysRq mode. 816 */ 817 if (value) 818 set_bit(code, sysrq->key_down); 819 else 820 clear_bit(code, sysrq->key_down); 821 822 if (was_active) 823 schedule_work(&sysrq->reinject_work); 824 825 /* Check for reset sequence */ 826 sysrq_detect_reset_sequence(sysrq, code, value); 827 828 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 829 /* 830 * Pass on release events for keys that was pressed before 831 * entering SysRq mode. 832 */ 833 suppress = false; 834 } 835 836 return suppress; 837} 838 839static bool sysrq_filter(struct input_handle *handle, 840 unsigned int type, unsigned int code, int value) 841{ 842 struct sysrq_state *sysrq = handle->private; 843 bool suppress; 844 845 /* 846 * Do not filter anything if we are in the process of re-injecting 847 * Alt+SysRq combination. 848 */ 849 if (sysrq->reinjecting) 850 return false; 851 852 switch (type) { 853 854 case EV_SYN: 855 suppress = false; 856 break; 857 858 case EV_KEY: 859 suppress = sysrq_handle_keypress(sysrq, code, value); 860 break; 861 862 default: 863 suppress = sysrq->active; 864 break; 865 } 866 867 return suppress; 868} 869 870static int sysrq_connect(struct input_handler *handler, 871 struct input_dev *dev, 872 const struct input_device_id *id) 873{ 874 struct sysrq_state *sysrq; 875 int error; 876 877 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 878 if (!sysrq) 879 return -ENOMEM; 880 881 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 882 883 sysrq->handle.dev = dev; 884 sysrq->handle.handler = handler; 885 sysrq->handle.name = "sysrq"; 886 sysrq->handle.private = sysrq; 887 setup_timer(&sysrq->keyreset_timer, 888 sysrq_do_reset, (unsigned long)sysrq); 889 890 error = input_register_handle(&sysrq->handle); 891 if (error) { 892 pr_err("Failed to register input sysrq handler, error %d\n", 893 error); 894 goto err_free; 895 } 896 897 error = input_open_device(&sysrq->handle); 898 if (error) { 899 pr_err("Failed to open input device, error %d\n", error); 900 goto err_unregister; 901 } 902 903 return 0; 904 905 err_unregister: 906 input_unregister_handle(&sysrq->handle); 907 err_free: 908 kfree(sysrq); 909 return error; 910} 911 912static void sysrq_disconnect(struct input_handle *handle) 913{ 914 struct sysrq_state *sysrq = handle->private; 915 916 input_close_device(handle); 917 cancel_work_sync(&sysrq->reinject_work); 918 del_timer_sync(&sysrq->keyreset_timer); 919 input_unregister_handle(handle); 920 kfree(sysrq); 921} 922 923/* 924 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 925 * keyboards have SysRq key predefined and so user may add it to keymap 926 * later, but we expect all such keyboards to have left alt. 927 */ 928static const struct input_device_id sysrq_ids[] = { 929 { 930 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 931 INPUT_DEVICE_ID_MATCH_KEYBIT, 932 .evbit = { BIT_MASK(EV_KEY) }, 933 .keybit = { BIT_MASK(KEY_LEFTALT) }, 934 }, 935 { }, 936}; 937 938static struct input_handler sysrq_handler = { 939 .filter = sysrq_filter, 940 .connect = sysrq_connect, 941 .disconnect = sysrq_disconnect, 942 .name = "sysrq", 943 .id_table = sysrq_ids, 944}; 945 946static bool sysrq_handler_registered; 947 948static inline void sysrq_register_handler(void) 949{ 950 int error; 951 952 sysrq_of_get_keyreset_config(); 953 954 error = input_register_handler(&sysrq_handler); 955 if (error) 956 pr_err("Failed to register input handler, error %d", error); 957 else 958 sysrq_handler_registered = true; 959} 960 961static inline void sysrq_unregister_handler(void) 962{ 963 if (sysrq_handler_registered) { 964 input_unregister_handler(&sysrq_handler); 965 sysrq_handler_registered = false; 966 } 967} 968 969static int sysrq_reset_seq_param_set(const char *buffer, 970 const struct kernel_param *kp) 971{ 972 unsigned long val; 973 int error; 974 975 error = kstrtoul(buffer, 0, &val); 976 if (error < 0) 977 return error; 978 979 if (val > KEY_MAX) 980 return -EINVAL; 981 982 *((unsigned short *)kp->arg) = val; 983 sysrq_reset_seq_version++; 984 985 return 0; 986} 987 988static struct kernel_param_ops param_ops_sysrq_reset_seq = { 989 .get = param_get_ushort, 990 .set = sysrq_reset_seq_param_set, 991}; 992 993#define param_check_sysrq_reset_seq(name, p) \ 994 __param_check(name, p, unsigned short) 995 996module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 997 &sysrq_reset_seq_len, 0644); 998 999module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1000 1001#else 1002 1003static inline void sysrq_register_handler(void) 1004{ 1005} 1006 1007static inline void sysrq_unregister_handler(void) 1008{ 1009} 1010 1011#endif /* CONFIG_INPUT */ 1012 1013int sysrq_toggle_support(int enable_mask) 1014{ 1015 bool was_enabled = sysrq_on(); 1016 1017 sysrq_enabled = enable_mask; 1018 1019 if (was_enabled != sysrq_on()) { 1020 if (sysrq_on()) 1021 sysrq_register_handler(); 1022 else 1023 sysrq_unregister_handler(); 1024 } 1025 1026 return 0; 1027} 1028 1029static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1030 struct sysrq_key_op *remove_op_p) 1031{ 1032 int retval; 1033 1034 spin_lock(&sysrq_key_table_lock); 1035 if (__sysrq_get_key_op(key) == remove_op_p) { 1036 __sysrq_put_key_op(key, insert_op_p); 1037 retval = 0; 1038 } else { 1039 retval = -1; 1040 } 1041 spin_unlock(&sysrq_key_table_lock); 1042 1043 /* 1044 * A concurrent __handle_sysrq either got the old op or the new op. 1045 * Wait for it to go away before returning, so the code for an old 1046 * op is not freed (eg. on module unload) while it is in use. 1047 */ 1048 synchronize_rcu(); 1049 1050 return retval; 1051} 1052 1053int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1054{ 1055 return __sysrq_swap_key_ops(key, op_p, NULL); 1056} 1057EXPORT_SYMBOL(register_sysrq_key); 1058 1059int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1060{ 1061 return __sysrq_swap_key_ops(key, NULL, op_p); 1062} 1063EXPORT_SYMBOL(unregister_sysrq_key); 1064 1065#ifdef CONFIG_PROC_FS 1066/* 1067 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1068 */ 1069static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1070 size_t count, loff_t *ppos) 1071{ 1072 if (count) { 1073 char c; 1074 1075 if (get_user(c, buf)) 1076 return -EFAULT; 1077 __handle_sysrq(c, false); 1078 } 1079 1080 return count; 1081} 1082 1083static const struct file_operations proc_sysrq_trigger_operations = { 1084 .write = write_sysrq_trigger, 1085 .llseek = noop_llseek, 1086}; 1087 1088static void sysrq_init_procfs(void) 1089{ 1090 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1091 &proc_sysrq_trigger_operations)) 1092 pr_err("Failed to register proc interface\n"); 1093} 1094 1095#else 1096 1097static inline void sysrq_init_procfs(void) 1098{ 1099} 1100 1101#endif /* CONFIG_PROC_FS */ 1102 1103static int __init sysrq_init(void) 1104{ 1105 sysrq_init_procfs(); 1106 1107 if (sysrq_on()) 1108 sysrq_register_handler(); 1109 1110 return 0; 1111} 1112module_init(sysrq_init); 1113