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}; 452 453/* Key Operations table and lock */ 454static DEFINE_SPINLOCK(sysrq_key_table_lock); 455 456static const struct sysrq_key_op *sysrq_key_table[62] = { 457 &sysrq_loglevel_op, /* 0 */ 458 &sysrq_loglevel_op, /* 1 */ 459 &sysrq_loglevel_op, /* 2 */ 460 &sysrq_loglevel_op, /* 3 */ 461 &sysrq_loglevel_op, /* 4 */ 462 &sysrq_loglevel_op, /* 5 */ 463 &sysrq_loglevel_op, /* 6 */ 464 &sysrq_loglevel_op, /* 7 */ 465 &sysrq_loglevel_op, /* 8 */ 466 &sysrq_loglevel_op, /* 9 */ 467 468 /* 469 * a: Don't use for system provided sysrqs, it is handled specially on 470 * sparc and will never arrive. 471 */ 472 NULL, /* a */ 473 &sysrq_reboot_op, /* b */ 474 &sysrq_crash_op, /* c */ 475 &sysrq_showlocks_op, /* d */ 476 &sysrq_term_op, /* e */ 477 &sysrq_moom_op, /* f */ 478 /* g: May be registered for the kernel debugger */ 479 NULL, /* g */ 480 NULL, /* h - reserved for help */ 481 &sysrq_kill_op, /* i */ 482 &sysrq_thaw_op, /* j */ 483 &sysrq_SAK_op, /* k */ 484 &sysrq_showallcpus_op, /* l */ 485 &sysrq_showmem_op, /* m */ 486 &sysrq_unrt_op, /* n */ 487 /* o: This will often be registered as 'Off' at init time */ 488 NULL, /* o */ 489 &sysrq_showregs_op, /* p */ 490 &sysrq_show_timers_op, /* q */ 491 &sysrq_unraw_op, /* r */ 492 &sysrq_sync_op, /* s */ 493 &sysrq_showstate_op, /* t */ 494 &sysrq_mountro_op, /* u */ 495 /* v: May be registered for frame buffer console restore */ 496 NULL, /* v */ 497 &sysrq_showstate_blocked_op, /* w */ 498 /* x: May be registered on mips for TLB dump */ 499 /* x: May be registered on ppc/powerpc for xmon */ 500 /* x: May be registered on sparc64 for global PMU dump */ 501 NULL, /* x */ 502 /* y: May be registered on sparc64 for global register dump */ 503 NULL, /* y */ 504 &sysrq_ftrace_dump_op, /* z */ 505 NULL, /* A */ 506 NULL, /* B */ 507 NULL, /* C */ 508 NULL, /* D */ 509 NULL, /* E */ 510 NULL, /* F */ 511 NULL, /* G */ 512 NULL, /* H */ 513 NULL, /* I */ 514 NULL, /* J */ 515 NULL, /* K */ 516 NULL, /* L */ 517 NULL, /* M */ 518 NULL, /* N */ 519 NULL, /* O */ 520 NULL, /* P */ 521 NULL, /* Q */ 522 NULL, /* R */ 523 NULL, /* S */ 524 NULL, /* T */ 525 NULL, /* U */ 526 NULL, /* V */ 527 NULL, /* W */ 528 NULL, /* X */ 529 NULL, /* Y */ 530 NULL, /* Z */ 531}; 532 533/* key2index calculation, -1 on invalid index */ 534static int sysrq_key_table_key2index(u8 key) 535{ 536 switch (key) { 537 case '0' ... '9': 538 return key - '0'; 539 case 'a' ... 'z': 540 return key - 'a' + 10; 541 case 'A' ... 'Z': 542 return key - 'A' + 10 + 26; 543 default: 544 return -1; 545 } 546} 547 548/* 549 * get and put functions for the table, exposed to modules. 550 */ 551static const struct sysrq_key_op *__sysrq_get_key_op(u8 key) 552{ 553 const struct sysrq_key_op *op_p = NULL; 554 int i; 555 556 i = sysrq_key_table_key2index(key); 557 if (i != -1) 558 op_p = sysrq_key_table[i]; 559 560 return op_p; 561} 562 563static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p) 564{ 565 int i = sysrq_key_table_key2index(key); 566 567 if (i != -1) 568 sysrq_key_table[i] = op_p; 569} 570 571void __handle_sysrq(u8 key, bool check_mask) 572{ 573 const struct sysrq_key_op *op_p; 574 int orig_log_level; 575 int orig_suppress_printk; 576 int i; 577 578 orig_suppress_printk = suppress_printk; 579 suppress_printk = 0; 580 581 rcu_sysrq_start(); 582 rcu_read_lock(); 583 /* 584 * Raise the apparent loglevel to maximum so that the sysrq header 585 * is shown to provide the user with positive feedback. We do not 586 * simply emit this at KERN_EMERG as that would change message 587 * routing in the consumers of /proc/kmsg. 588 */ 589 orig_log_level = console_loglevel; 590 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 591 592 op_p = __sysrq_get_key_op(key); 593 if (op_p) { 594 /* 595 * Should we check for enabled operations (/proc/sysrq-trigger 596 * should not) and is the invoked operation enabled? 597 */ 598 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 599 pr_info("%s\n", op_p->action_msg); 600 console_loglevel = orig_log_level; 601 op_p->handler(key); 602 } else { 603 pr_info("This sysrq operation is disabled.\n"); 604 console_loglevel = orig_log_level; 605 } 606 } else { 607 pr_info("HELP : "); 608 /* Only print the help msg once per handler */ 609 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 610 if (sysrq_key_table[i]) { 611 int j; 612 613 for (j = 0; sysrq_key_table[i] != 614 sysrq_key_table[j]; j++) 615 ; 616 if (j != i) 617 continue; 618 pr_cont("%s ", sysrq_key_table[i]->help_msg); 619 } 620 } 621 pr_cont("\n"); 622 console_loglevel = orig_log_level; 623 } 624 rcu_read_unlock(); 625 rcu_sysrq_end(); 626 627 suppress_printk = orig_suppress_printk; 628} 629 630void handle_sysrq(u8 key) 631{ 632 if (sysrq_on()) 633 __handle_sysrq(key, true); 634} 635EXPORT_SYMBOL(handle_sysrq); 636 637#ifdef CONFIG_INPUT 638static int sysrq_reset_downtime_ms; 639 640/* Simple translation table for the SysRq keys */ 641static const unsigned char sysrq_xlate[KEY_CNT] = 642 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 643 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 644 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 645 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 646 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 647 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 648 "\r\000/"; /* 0x60 - 0x6f */ 649 650struct sysrq_state { 651 struct input_handle handle; 652 struct work_struct reinject_work; 653 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 654 unsigned int alt; 655 unsigned int alt_use; 656 unsigned int shift; 657 unsigned int shift_use; 658 bool active; 659 bool need_reinject; 660 bool reinjecting; 661 662 /* reset sequence handling */ 663 bool reset_canceled; 664 bool reset_requested; 665 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 666 int reset_seq_len; 667 int reset_seq_cnt; 668 int reset_seq_version; 669 struct timer_list keyreset_timer; 670}; 671 672#define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 673static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 674static unsigned int sysrq_reset_seq_len; 675static unsigned int sysrq_reset_seq_version = 1; 676 677static void sysrq_parse_reset_sequence(struct sysrq_state *state) 678{ 679 int i; 680 unsigned short key; 681 682 state->reset_seq_cnt = 0; 683 684 for (i = 0; i < sysrq_reset_seq_len; i++) { 685 key = sysrq_reset_seq[i]; 686 687 if (key == KEY_RESERVED || key > KEY_MAX) 688 break; 689 690 __set_bit(key, state->reset_keybit); 691 state->reset_seq_len++; 692 693 if (test_bit(key, state->key_down)) 694 state->reset_seq_cnt++; 695 } 696 697 /* Disable reset until old keys are not released */ 698 state->reset_canceled = state->reset_seq_cnt != 0; 699 700 state->reset_seq_version = sysrq_reset_seq_version; 701} 702 703static void sysrq_do_reset(struct timer_list *t) 704{ 705 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 706 707 state->reset_requested = true; 708 709 orderly_reboot(); 710} 711 712static void sysrq_handle_reset_request(struct sysrq_state *state) 713{ 714 if (state->reset_requested) 715 __handle_sysrq(sysrq_xlate[KEY_B], false); 716 717 if (sysrq_reset_downtime_ms) 718 mod_timer(&state->keyreset_timer, 719 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 720 else 721 sysrq_do_reset(&state->keyreset_timer); 722} 723 724static void sysrq_detect_reset_sequence(struct sysrq_state *state, 725 unsigned int code, int value) 726{ 727 if (!test_bit(code, state->reset_keybit)) { 728 /* 729 * Pressing any key _not_ in reset sequence cancels 730 * the reset sequence. Also cancelling the timer in 731 * case additional keys were pressed after a reset 732 * has been requested. 733 */ 734 if (value && state->reset_seq_cnt) { 735 state->reset_canceled = true; 736 del_timer(&state->keyreset_timer); 737 } 738 } else if (value == 0) { 739 /* 740 * Key release - all keys in the reset sequence need 741 * to be pressed and held for the reset timeout 742 * to hold. 743 */ 744 del_timer(&state->keyreset_timer); 745 746 if (--state->reset_seq_cnt == 0) 747 state->reset_canceled = false; 748 } else if (value == 1) { 749 /* key press, not autorepeat */ 750 if (++state->reset_seq_cnt == state->reset_seq_len && 751 !state->reset_canceled) { 752 sysrq_handle_reset_request(state); 753 } 754 } 755} 756 757#ifdef CONFIG_OF 758static void sysrq_of_get_keyreset_config(void) 759{ 760 u32 key; 761 struct device_node *np; 762 struct property *prop; 763 const __be32 *p; 764 765 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 766 if (!np) { 767 pr_debug("No sysrq node found"); 768 return; 769 } 770 771 /* Reset in case a __weak definition was present */ 772 sysrq_reset_seq_len = 0; 773 774 of_property_for_each_u32(np, "keyset", prop, p, key) { 775 if (key == KEY_RESERVED || key > KEY_MAX || 776 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 777 break; 778 779 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 780 } 781 782 /* Get reset timeout if any. */ 783 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 784 785 of_node_put(np); 786} 787#else 788static void sysrq_of_get_keyreset_config(void) 789{ 790} 791#endif 792 793static void sysrq_reinject_alt_sysrq(struct work_struct *work) 794{ 795 struct sysrq_state *sysrq = 796 container_of(work, struct sysrq_state, reinject_work); 797 struct input_handle *handle = &sysrq->handle; 798 unsigned int alt_code = sysrq->alt_use; 799 800 if (sysrq->need_reinject) { 801 /* we do not want the assignment to be reordered */ 802 sysrq->reinjecting = true; 803 mb(); 804 805 /* Simulate press and release of Alt + SysRq */ 806 input_inject_event(handle, EV_KEY, alt_code, 1); 807 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 808 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 809 810 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 811 input_inject_event(handle, EV_KEY, alt_code, 0); 812 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 813 814 mb(); 815 sysrq->reinjecting = false; 816 } 817} 818 819static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 820 unsigned int code, int value) 821{ 822 bool was_active = sysrq->active; 823 bool suppress; 824 825 switch (code) { 826 827 case KEY_LEFTALT: 828 case KEY_RIGHTALT: 829 if (!value) { 830 /* One of ALTs is being released */ 831 if (sysrq->active && code == sysrq->alt_use) 832 sysrq->active = false; 833 834 sysrq->alt = KEY_RESERVED; 835 836 } else if (value != 2) { 837 sysrq->alt = code; 838 sysrq->need_reinject = false; 839 } 840 break; 841 842 case KEY_LEFTSHIFT: 843 case KEY_RIGHTSHIFT: 844 if (!value) 845 sysrq->shift = KEY_RESERVED; 846 else if (value != 2) 847 sysrq->shift = code; 848 if (sysrq->active) 849 sysrq->shift_use = sysrq->shift; 850 break; 851 852 case KEY_SYSRQ: 853 if (value == 1 && sysrq->alt != KEY_RESERVED) { 854 sysrq->active = true; 855 sysrq->alt_use = sysrq->alt; 856 /* either RESERVED (for released) or actual code */ 857 sysrq->shift_use = sysrq->shift; 858 /* 859 * If nothing else will be pressed we'll need 860 * to re-inject Alt-SysRq keysroke. 861 */ 862 sysrq->need_reinject = true; 863 } 864 865 /* 866 * Pretend that sysrq was never pressed at all. This 867 * is needed to properly handle KGDB which will try 868 * to release all keys after exiting debugger. If we 869 * do not clear key bit it KGDB will end up sending 870 * release events for Alt and SysRq, potentially 871 * triggering print screen function. 872 */ 873 if (sysrq->active) 874 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 875 876 break; 877 878 default: 879 if (sysrq->active && value && value != 2) { 880 unsigned char c = sysrq_xlate[code]; 881 882 sysrq->need_reinject = false; 883 if (sysrq->shift_use != KEY_RESERVED) 884 c = toupper(c); 885 __handle_sysrq(c, true); 886 } 887 break; 888 } 889 890 suppress = sysrq->active; 891 892 if (!sysrq->active) { 893 894 /* 895 * See if reset sequence has changed since the last time. 896 */ 897 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 898 sysrq_parse_reset_sequence(sysrq); 899 900 /* 901 * If we are not suppressing key presses keep track of 902 * keyboard state so we can release keys that have been 903 * pressed before entering SysRq mode. 904 */ 905 if (value) 906 set_bit(code, sysrq->key_down); 907 else 908 clear_bit(code, sysrq->key_down); 909 910 if (was_active) 911 schedule_work(&sysrq->reinject_work); 912 913 /* Check for reset sequence */ 914 sysrq_detect_reset_sequence(sysrq, code, value); 915 916 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 917 /* 918 * Pass on release events for keys that was pressed before 919 * entering SysRq mode. 920 */ 921 suppress = false; 922 } 923 924 return suppress; 925} 926 927static bool sysrq_filter(struct input_handle *handle, 928 unsigned int type, unsigned int code, int value) 929{ 930 struct sysrq_state *sysrq = handle->private; 931 bool suppress; 932 933 /* 934 * Do not filter anything if we are in the process of re-injecting 935 * Alt+SysRq combination. 936 */ 937 if (sysrq->reinjecting) 938 return false; 939 940 switch (type) { 941 942 case EV_SYN: 943 suppress = false; 944 break; 945 946 case EV_KEY: 947 suppress = sysrq_handle_keypress(sysrq, code, value); 948 break; 949 950 default: 951 suppress = sysrq->active; 952 break; 953 } 954 955 return suppress; 956} 957 958static int sysrq_connect(struct input_handler *handler, 959 struct input_dev *dev, 960 const struct input_device_id *id) 961{ 962 struct sysrq_state *sysrq; 963 int error; 964 965 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 966 if (!sysrq) 967 return -ENOMEM; 968 969 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 970 971 sysrq->handle.dev = dev; 972 sysrq->handle.handler = handler; 973 sysrq->handle.name = "sysrq"; 974 sysrq->handle.private = sysrq; 975 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 976 977 error = input_register_handle(&sysrq->handle); 978 if (error) { 979 pr_err("Failed to register input sysrq handler, error %d\n", 980 error); 981 goto err_free; 982 } 983 984 error = input_open_device(&sysrq->handle); 985 if (error) { 986 pr_err("Failed to open input device, error %d\n", error); 987 goto err_unregister; 988 } 989 990 return 0; 991 992 err_unregister: 993 input_unregister_handle(&sysrq->handle); 994 err_free: 995 kfree(sysrq); 996 return error; 997} 998 999static void sysrq_disconnect(struct input_handle *handle) 1000{ 1001 struct sysrq_state *sysrq = handle->private; 1002 1003 input_close_device(handle); 1004 cancel_work_sync(&sysrq->reinject_work); 1005 timer_shutdown_sync(&sysrq->keyreset_timer); 1006 input_unregister_handle(handle); 1007 kfree(sysrq); 1008} 1009 1010/* 1011 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 1012 * keyboards have SysRq key predefined and so user may add it to keymap 1013 * later, but we expect all such keyboards to have left alt. 1014 */ 1015static const struct input_device_id sysrq_ids[] = { 1016 { 1017 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 1018 INPUT_DEVICE_ID_MATCH_KEYBIT, 1019 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 1020 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 1021 }, 1022 { }, 1023}; 1024 1025static struct input_handler sysrq_handler = { 1026 .filter = sysrq_filter, 1027 .connect = sysrq_connect, 1028 .disconnect = sysrq_disconnect, 1029 .name = "sysrq", 1030 .id_table = sysrq_ids, 1031}; 1032 1033static inline void sysrq_register_handler(void) 1034{ 1035 int error; 1036 1037 sysrq_of_get_keyreset_config(); 1038 1039 error = input_register_handler(&sysrq_handler); 1040 if (error) 1041 pr_err("Failed to register input handler, error %d", error); 1042} 1043 1044static inline void sysrq_unregister_handler(void) 1045{ 1046 input_unregister_handler(&sysrq_handler); 1047} 1048 1049static int sysrq_reset_seq_param_set(const char *buffer, 1050 const struct kernel_param *kp) 1051{ 1052 unsigned long val; 1053 int error; 1054 1055 error = kstrtoul(buffer, 0, &val); 1056 if (error < 0) 1057 return error; 1058 1059 if (val > KEY_MAX) 1060 return -EINVAL; 1061 1062 *((unsigned short *)kp->arg) = val; 1063 sysrq_reset_seq_version++; 1064 1065 return 0; 1066} 1067 1068static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1069 .get = param_get_ushort, 1070 .set = sysrq_reset_seq_param_set, 1071}; 1072 1073#define param_check_sysrq_reset_seq(name, p) \ 1074 __param_check(name, p, unsigned short) 1075 1076/* 1077 * not really modular, but the easiest way to keep compat with existing 1078 * bootargs behaviour is to continue using module_param here. 1079 */ 1080module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1081 &sysrq_reset_seq_len, 0644); 1082 1083module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1084 1085#else 1086 1087static inline void sysrq_register_handler(void) 1088{ 1089} 1090 1091static inline void sysrq_unregister_handler(void) 1092{ 1093} 1094 1095#endif /* CONFIG_INPUT */ 1096 1097int sysrq_toggle_support(int enable_mask) 1098{ 1099 bool was_enabled = sysrq_on(); 1100 1101 sysrq_enabled = enable_mask; 1102 1103 if (was_enabled != sysrq_on()) { 1104 if (sysrq_on()) 1105 sysrq_register_handler(); 1106 else 1107 sysrq_unregister_handler(); 1108 } 1109 1110 return 0; 1111} 1112EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1113 1114static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p, 1115 const struct sysrq_key_op *remove_op_p) 1116{ 1117 int retval; 1118 1119 spin_lock(&sysrq_key_table_lock); 1120 if (__sysrq_get_key_op(key) == remove_op_p) { 1121 __sysrq_put_key_op(key, insert_op_p); 1122 retval = 0; 1123 } else { 1124 retval = -1; 1125 } 1126 spin_unlock(&sysrq_key_table_lock); 1127 1128 /* 1129 * A concurrent __handle_sysrq either got the old op or the new op. 1130 * Wait for it to go away before returning, so the code for an old 1131 * op is not freed (eg. on module unload) while it is in use. 1132 */ 1133 synchronize_rcu(); 1134 1135 return retval; 1136} 1137 1138int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p) 1139{ 1140 return __sysrq_swap_key_ops(key, op_p, NULL); 1141} 1142EXPORT_SYMBOL(register_sysrq_key); 1143 1144int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p) 1145{ 1146 return __sysrq_swap_key_ops(key, NULL, op_p); 1147} 1148EXPORT_SYMBOL(unregister_sysrq_key); 1149 1150#ifdef CONFIG_PROC_FS 1151/* 1152 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1153 * Normally, only the first character written is processed. 1154 * However, if the first character is an underscore, 1155 * all characters are processed. 1156 */ 1157static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1158 size_t count, loff_t *ppos) 1159{ 1160 bool bulk = false; 1161 size_t i; 1162 1163 for (i = 0; i < count; i++) { 1164 char c; 1165 1166 if (get_user(c, buf + i)) 1167 return -EFAULT; 1168 1169 if (c == '_') 1170 bulk = true; 1171 else 1172 __handle_sysrq(c, false); 1173 1174 if (!bulk) 1175 break; 1176 } 1177 1178 return count; 1179} 1180 1181static const struct proc_ops sysrq_trigger_proc_ops = { 1182 .proc_write = write_sysrq_trigger, 1183 .proc_lseek = noop_llseek, 1184}; 1185 1186static void sysrq_init_procfs(void) 1187{ 1188 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1189 &sysrq_trigger_proc_ops)) 1190 pr_err("Failed to register proc interface\n"); 1191} 1192 1193#else 1194 1195static inline void sysrq_init_procfs(void) 1196{ 1197} 1198 1199#endif /* CONFIG_PROC_FS */ 1200 1201static int __init sysrq_init(void) 1202{ 1203 sysrq_init_procfs(); 1204 1205 if (sysrq_on()) 1206 sysrq_register_handler(); 1207 1208 return 0; 1209} 1210device_initcall(sysrq_init); 1211