1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Linux Magic System Request Key Hacks 4 * 5 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz> 6 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz> 7 * 8 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com> 9 * overhauled to use key registration 10 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies 11 * 12 * Copyright (c) 2010 Dmitry Torokhov 13 * Input handler conversion 14 */ 15 16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 17 18 #include <linux/sched/signal.h> 19 #include <linux/sched/rt.h> 20 #include <linux/sched/debug.h> 21 #include <linux/sched/task.h> 22 #include <linux/interrupt.h> 23 #include <linux/mm.h> 24 #include <linux/fs.h> 25 #include <linux/mount.h> 26 #include <linux/kdev_t.h> 27 #include <linux/major.h> 28 #include <linux/reboot.h> 29 #include <linux/sysrq.h> 30 #include <linux/kbd_kern.h> 31 #include <linux/proc_fs.h> 32 #include <linux/nmi.h> 33 #include <linux/quotaops.h> 34 #include <linux/perf_event.h> 35 #include <linux/kernel.h> 36 #include <linux/module.h> 37 #include <linux/suspend.h> 38 #include <linux/writeback.h> 39 #include <linux/swap.h> 40 #include <linux/spinlock.h> 41 #include <linux/vt_kern.h> 42 #include <linux/workqueue.h> 43 #include <linux/hrtimer.h> 44 #include <linux/oom.h> 45 #include <linux/slab.h> 46 #include <linux/input.h> 47 #include <linux/uaccess.h> 48 #include <linux/moduleparam.h> 49 #include <linux/jiffies.h> 50 #include <linux/syscalls.h> 51 #include <linux/of.h> 52 #include <linux/rcupdate.h> 53 54 #include <asm/ptrace.h> 55 #include <asm/irq_regs.h> 56 57 /* Whether we react on sysrq keys or just ignore them */ 58 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; 59 static bool __read_mostly sysrq_always_enabled; 60 61 static bool sysrq_on(void) 62 { 63 return sysrq_enabled || sysrq_always_enabled; 64 } 65 66 /** 67 * sysrq_mask - Getter for sysrq_enabled mask. 68 * 69 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise. 70 */ 71 int sysrq_mask(void) 72 { 73 if (sysrq_always_enabled) 74 return 1; 75 return sysrq_enabled; 76 } 77 EXPORT_SYMBOL_GPL(sysrq_mask); 78 79 /* 80 * A value of 1 means 'all', other nonzero values are an op mask: 81 */ 82 static bool sysrq_on_mask(int mask) 83 { 84 return sysrq_always_enabled || 85 sysrq_enabled == 1 || 86 (sysrq_enabled & mask); 87 } 88 89 static int __init sysrq_always_enabled_setup(char *str) 90 { 91 sysrq_always_enabled = true; 92 pr_info("sysrq always enabled.\n"); 93 94 return 1; 95 } 96 97 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 98 99 100 static void sysrq_handle_loglevel(int key) 101 { 102 int i; 103 104 i = key - '0'; 105 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 106 pr_info("Loglevel set to %d\n", i); 107 console_loglevel = i; 108 } 109 static 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 117 static void sysrq_handle_SAK(int key) 118 { 119 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 120 schedule_work(SAK_work); 121 } 122 static const struct sysrq_key_op sysrq_SAK_op = { 123 .handler = sysrq_handle_SAK, 124 .help_msg = "sak(k)", 125 .action_msg = "SAK", 126 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 127 }; 128 #else 129 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL) 130 #endif 131 132 #ifdef CONFIG_VT 133 static void sysrq_handle_unraw(int key) 134 { 135 vt_reset_unicode(fg_console); 136 } 137 138 static const struct sysrq_key_op sysrq_unraw_op = { 139 .handler = sysrq_handle_unraw, 140 .help_msg = "unraw(r)", 141 .action_msg = "Keyboard mode set to system default", 142 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 143 }; 144 #else 145 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL) 146 #endif /* CONFIG_VT */ 147 148 static void sysrq_handle_crash(int key) 149 { 150 /* release the RCU read lock before crashing */ 151 rcu_read_unlock(); 152 153 panic("sysrq triggered crash\n"); 154 } 155 static const struct sysrq_key_op sysrq_crash_op = { 156 .handler = sysrq_handle_crash, 157 .help_msg = "crash(c)", 158 .action_msg = "Trigger a crash", 159 .enable_mask = SYSRQ_ENABLE_DUMP, 160 }; 161 162 static void sysrq_handle_reboot(int key) 163 { 164 lockdep_off(); 165 local_irq_enable(); 166 emergency_restart(); 167 } 168 static const struct sysrq_key_op sysrq_reboot_op = { 169 .handler = sysrq_handle_reboot, 170 .help_msg = "reboot(b)", 171 .action_msg = "Resetting", 172 .enable_mask = SYSRQ_ENABLE_BOOT, 173 }; 174 175 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op; 176 177 static void sysrq_handle_sync(int key) 178 { 179 emergency_sync(); 180 } 181 static const struct sysrq_key_op sysrq_sync_op = { 182 .handler = sysrq_handle_sync, 183 .help_msg = "sync(s)", 184 .action_msg = "Emergency Sync", 185 .enable_mask = SYSRQ_ENABLE_SYNC, 186 }; 187 188 static void sysrq_handle_show_timers(int key) 189 { 190 sysrq_timer_list_show(); 191 } 192 193 static const struct sysrq_key_op sysrq_show_timers_op = { 194 .handler = sysrq_handle_show_timers, 195 .help_msg = "show-all-timers(q)", 196 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 197 }; 198 199 static void sysrq_handle_mountro(int key) 200 { 201 emergency_remount(); 202 } 203 static const struct sysrq_key_op sysrq_mountro_op = { 204 .handler = sysrq_handle_mountro, 205 .help_msg = "unmount(u)", 206 .action_msg = "Emergency Remount R/O", 207 .enable_mask = SYSRQ_ENABLE_REMOUNT, 208 }; 209 210 #ifdef CONFIG_LOCKDEP 211 static void sysrq_handle_showlocks(int key) 212 { 213 debug_show_all_locks(); 214 } 215 216 static const struct sysrq_key_op sysrq_showlocks_op = { 217 .handler = sysrq_handle_showlocks, 218 .help_msg = "show-all-locks(d)", 219 .action_msg = "Show Locks Held", 220 }; 221 #else 222 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL) 223 #endif 224 225 #ifdef CONFIG_SMP 226 static DEFINE_RAW_SPINLOCK(show_lock); 227 228 static void showacpu(void *dummy) 229 { 230 unsigned long flags; 231 232 /* Idle CPUs have no interesting backtrace. */ 233 if (idle_cpu(smp_processor_id())) 234 return; 235 236 raw_spin_lock_irqsave(&show_lock, flags); 237 pr_info("CPU%d:\n", smp_processor_id()); 238 show_stack(NULL, NULL, KERN_INFO); 239 raw_spin_unlock_irqrestore(&show_lock, flags); 240 } 241 242 static void sysrq_showregs_othercpus(struct work_struct *dummy) 243 { 244 smp_call_function(showacpu, NULL, 0); 245 } 246 247 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 248 249 static void sysrq_handle_showallcpus(int key) 250 { 251 /* 252 * Fall back to the workqueue based printing if the 253 * backtrace printing did not succeed or the 254 * architecture has no support for it: 255 */ 256 if (!trigger_all_cpu_backtrace()) { 257 struct pt_regs *regs = NULL; 258 259 if (in_irq()) 260 regs = get_irq_regs(); 261 if (regs) { 262 pr_info("CPU%d:\n", smp_processor_id()); 263 show_regs(regs); 264 } 265 schedule_work(&sysrq_showallcpus); 266 } 267 } 268 269 static const struct sysrq_key_op sysrq_showallcpus_op = { 270 .handler = sysrq_handle_showallcpus, 271 .help_msg = "show-backtrace-all-active-cpus(l)", 272 .action_msg = "Show backtrace of all active CPUs", 273 .enable_mask = SYSRQ_ENABLE_DUMP, 274 }; 275 #endif 276 277 static void sysrq_handle_showregs(int key) 278 { 279 struct pt_regs *regs = NULL; 280 281 if (in_irq()) 282 regs = get_irq_regs(); 283 if (regs) 284 show_regs(regs); 285 perf_event_print_debug(); 286 } 287 static const struct sysrq_key_op sysrq_showregs_op = { 288 .handler = sysrq_handle_showregs, 289 .help_msg = "show-registers(p)", 290 .action_msg = "Show Regs", 291 .enable_mask = SYSRQ_ENABLE_DUMP, 292 }; 293 294 static void sysrq_handle_showstate(int key) 295 { 296 show_state(); 297 show_workqueue_state(); 298 } 299 static const struct sysrq_key_op sysrq_showstate_op = { 300 .handler = sysrq_handle_showstate, 301 .help_msg = "show-task-states(t)", 302 .action_msg = "Show State", 303 .enable_mask = SYSRQ_ENABLE_DUMP, 304 }; 305 306 static void sysrq_handle_showstate_blocked(int key) 307 { 308 show_state_filter(TASK_UNINTERRUPTIBLE); 309 } 310 static const struct sysrq_key_op sysrq_showstate_blocked_op = { 311 .handler = sysrq_handle_showstate_blocked, 312 .help_msg = "show-blocked-tasks(w)", 313 .action_msg = "Show Blocked State", 314 .enable_mask = SYSRQ_ENABLE_DUMP, 315 }; 316 317 #ifdef CONFIG_TRACING 318 #include <linux/ftrace.h> 319 320 static void sysrq_ftrace_dump(int key) 321 { 322 ftrace_dump(DUMP_ALL); 323 } 324 static const struct sysrq_key_op sysrq_ftrace_dump_op = { 325 .handler = sysrq_ftrace_dump, 326 .help_msg = "dump-ftrace-buffer(z)", 327 .action_msg = "Dump ftrace buffer", 328 .enable_mask = SYSRQ_ENABLE_DUMP, 329 }; 330 #else 331 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL) 332 #endif 333 334 static void sysrq_handle_showmem(int key) 335 { 336 show_mem(0, NULL); 337 } 338 static const struct sysrq_key_op sysrq_showmem_op = { 339 .handler = sysrq_handle_showmem, 340 .help_msg = "show-memory-usage(m)", 341 .action_msg = "Show Memory", 342 .enable_mask = SYSRQ_ENABLE_DUMP, 343 }; 344 345 /* 346 * Signal sysrq helper function. Sends a signal to all user processes. 347 */ 348 static void send_sig_all(int sig) 349 { 350 struct task_struct *p; 351 352 read_lock(&tasklist_lock); 353 for_each_process(p) { 354 if (p->flags & PF_KTHREAD) 355 continue; 356 if (is_global_init(p)) 357 continue; 358 359 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX); 360 } 361 read_unlock(&tasklist_lock); 362 } 363 364 static void sysrq_handle_term(int key) 365 { 366 send_sig_all(SIGTERM); 367 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 368 } 369 static const struct sysrq_key_op sysrq_term_op = { 370 .handler = sysrq_handle_term, 371 .help_msg = "terminate-all-tasks(e)", 372 .action_msg = "Terminate All Tasks", 373 .enable_mask = SYSRQ_ENABLE_SIGNAL, 374 }; 375 376 static void moom_callback(struct work_struct *ignored) 377 { 378 const gfp_t gfp_mask = GFP_KERNEL; 379 struct oom_control oc = { 380 .zonelist = node_zonelist(first_memory_node, gfp_mask), 381 .nodemask = NULL, 382 .memcg = NULL, 383 .gfp_mask = gfp_mask, 384 .order = -1, 385 }; 386 387 mutex_lock(&oom_lock); 388 if (!out_of_memory(&oc)) 389 pr_info("OOM request ignored. No task eligible\n"); 390 mutex_unlock(&oom_lock); 391 } 392 393 static DECLARE_WORK(moom_work, moom_callback); 394 395 static void sysrq_handle_moom(int key) 396 { 397 schedule_work(&moom_work); 398 } 399 static const struct sysrq_key_op sysrq_moom_op = { 400 .handler = sysrq_handle_moom, 401 .help_msg = "memory-full-oom-kill(f)", 402 .action_msg = "Manual OOM execution", 403 .enable_mask = SYSRQ_ENABLE_SIGNAL, 404 }; 405 406 #ifdef CONFIG_BLOCK 407 static void sysrq_handle_thaw(int key) 408 { 409 emergency_thaw_all(); 410 } 411 static const struct sysrq_key_op sysrq_thaw_op = { 412 .handler = sysrq_handle_thaw, 413 .help_msg = "thaw-filesystems(j)", 414 .action_msg = "Emergency Thaw of all frozen filesystems", 415 .enable_mask = SYSRQ_ENABLE_SIGNAL, 416 }; 417 #endif 418 419 static void sysrq_handle_kill(int key) 420 { 421 send_sig_all(SIGKILL); 422 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 423 } 424 static const struct sysrq_key_op sysrq_kill_op = { 425 .handler = sysrq_handle_kill, 426 .help_msg = "kill-all-tasks(i)", 427 .action_msg = "Kill All Tasks", 428 .enable_mask = SYSRQ_ENABLE_SIGNAL, 429 }; 430 431 static void sysrq_handle_unrt(int key) 432 { 433 normalize_rt_tasks(); 434 } 435 static const struct sysrq_key_op sysrq_unrt_op = { 436 .handler = sysrq_handle_unrt, 437 .help_msg = "nice-all-RT-tasks(n)", 438 .action_msg = "Nice All RT Tasks", 439 .enable_mask = SYSRQ_ENABLE_RTNICE, 440 }; 441 442 /* Key Operations table and lock */ 443 static DEFINE_SPINLOCK(sysrq_key_table_lock); 444 445 static const struct sysrq_key_op *sysrq_key_table[36] = { 446 &sysrq_loglevel_op, /* 0 */ 447 &sysrq_loglevel_op, /* 1 */ 448 &sysrq_loglevel_op, /* 2 */ 449 &sysrq_loglevel_op, /* 3 */ 450 &sysrq_loglevel_op, /* 4 */ 451 &sysrq_loglevel_op, /* 5 */ 452 &sysrq_loglevel_op, /* 6 */ 453 &sysrq_loglevel_op, /* 7 */ 454 &sysrq_loglevel_op, /* 8 */ 455 &sysrq_loglevel_op, /* 9 */ 456 457 /* 458 * a: Don't use for system provided sysrqs, it is handled specially on 459 * sparc and will never arrive. 460 */ 461 NULL, /* a */ 462 &sysrq_reboot_op, /* b */ 463 &sysrq_crash_op, /* c */ 464 &sysrq_showlocks_op, /* d */ 465 &sysrq_term_op, /* e */ 466 &sysrq_moom_op, /* f */ 467 /* g: May be registered for the kernel debugger */ 468 NULL, /* g */ 469 NULL, /* h - reserved for help */ 470 &sysrq_kill_op, /* i */ 471 #ifdef CONFIG_BLOCK 472 &sysrq_thaw_op, /* j */ 473 #else 474 NULL, /* j */ 475 #endif 476 &sysrq_SAK_op, /* k */ 477 #ifdef CONFIG_SMP 478 &sysrq_showallcpus_op, /* l */ 479 #else 480 NULL, /* l */ 481 #endif 482 &sysrq_showmem_op, /* m */ 483 &sysrq_unrt_op, /* n */ 484 /* o: This will often be registered as 'Off' at init time */ 485 NULL, /* o */ 486 &sysrq_showregs_op, /* p */ 487 &sysrq_show_timers_op, /* q */ 488 &sysrq_unraw_op, /* r */ 489 &sysrq_sync_op, /* s */ 490 &sysrq_showstate_op, /* t */ 491 &sysrq_mountro_op, /* u */ 492 /* v: May be registered for frame buffer console restore */ 493 NULL, /* v */ 494 &sysrq_showstate_blocked_op, /* w */ 495 /* x: May be registered on mips for TLB dump */ 496 /* x: May be registered on ppc/powerpc for xmon */ 497 /* x: May be registered on sparc64 for global PMU dump */ 498 NULL, /* x */ 499 /* y: May be registered on sparc64 for global register dump */ 500 NULL, /* y */ 501 &sysrq_ftrace_dump_op, /* z */ 502 }; 503 504 /* key2index calculation, -1 on invalid index */ 505 static int sysrq_key_table_key2index(int key) 506 { 507 int retval; 508 509 if ((key >= '0') && (key <= '9')) 510 retval = key - '0'; 511 else if ((key >= 'a') && (key <= 'z')) 512 retval = key + 10 - 'a'; 513 else 514 retval = -1; 515 return retval; 516 } 517 518 /* 519 * get and put functions for the table, exposed to modules. 520 */ 521 static const struct sysrq_key_op *__sysrq_get_key_op(int key) 522 { 523 const struct sysrq_key_op *op_p = NULL; 524 int i; 525 526 i = sysrq_key_table_key2index(key); 527 if (i != -1) 528 op_p = sysrq_key_table[i]; 529 530 return op_p; 531 } 532 533 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p) 534 { 535 int i = sysrq_key_table_key2index(key); 536 537 if (i != -1) 538 sysrq_key_table[i] = op_p; 539 } 540 541 void __handle_sysrq(int key, bool check_mask) 542 { 543 const struct sysrq_key_op *op_p; 544 int orig_log_level; 545 int orig_suppress_printk; 546 int i; 547 548 orig_suppress_printk = suppress_printk; 549 suppress_printk = 0; 550 551 rcu_sysrq_start(); 552 rcu_read_lock(); 553 /* 554 * Raise the apparent loglevel to maximum so that the sysrq header 555 * is shown to provide the user with positive feedback. We do not 556 * simply emit this at KERN_EMERG as that would change message 557 * routing in the consumers of /proc/kmsg. 558 */ 559 orig_log_level = console_loglevel; 560 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 561 562 op_p = __sysrq_get_key_op(key); 563 if (op_p) { 564 /* 565 * Should we check for enabled operations (/proc/sysrq-trigger 566 * should not) and is the invoked operation enabled? 567 */ 568 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 569 pr_info("%s\n", op_p->action_msg); 570 console_loglevel = orig_log_level; 571 op_p->handler(key); 572 } else { 573 pr_info("This sysrq operation is disabled.\n"); 574 console_loglevel = orig_log_level; 575 } 576 } else { 577 pr_info("HELP : "); 578 /* Only print the help msg once per handler */ 579 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 580 if (sysrq_key_table[i]) { 581 int j; 582 583 for (j = 0; sysrq_key_table[i] != 584 sysrq_key_table[j]; j++) 585 ; 586 if (j != i) 587 continue; 588 pr_cont("%s ", sysrq_key_table[i]->help_msg); 589 } 590 } 591 pr_cont("\n"); 592 console_loglevel = orig_log_level; 593 } 594 rcu_read_unlock(); 595 rcu_sysrq_end(); 596 597 suppress_printk = orig_suppress_printk; 598 } 599 600 void handle_sysrq(int key) 601 { 602 if (sysrq_on()) 603 __handle_sysrq(key, true); 604 } 605 EXPORT_SYMBOL(handle_sysrq); 606 607 #ifdef CONFIG_INPUT 608 static int sysrq_reset_downtime_ms; 609 610 /* Simple translation table for the SysRq keys */ 611 static const unsigned char sysrq_xlate[KEY_CNT] = 612 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 613 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 614 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 615 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 616 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 617 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 618 "\r\000/"; /* 0x60 - 0x6f */ 619 620 struct sysrq_state { 621 struct input_handle handle; 622 struct work_struct reinject_work; 623 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 624 unsigned int alt; 625 unsigned int alt_use; 626 bool active; 627 bool need_reinject; 628 bool reinjecting; 629 630 /* reset sequence handling */ 631 bool reset_canceled; 632 bool reset_requested; 633 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 634 int reset_seq_len; 635 int reset_seq_cnt; 636 int reset_seq_version; 637 struct timer_list keyreset_timer; 638 }; 639 640 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 641 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 642 static unsigned int sysrq_reset_seq_len; 643 static unsigned int sysrq_reset_seq_version = 1; 644 645 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 646 { 647 int i; 648 unsigned short key; 649 650 state->reset_seq_cnt = 0; 651 652 for (i = 0; i < sysrq_reset_seq_len; i++) { 653 key = sysrq_reset_seq[i]; 654 655 if (key == KEY_RESERVED || key > KEY_MAX) 656 break; 657 658 __set_bit(key, state->reset_keybit); 659 state->reset_seq_len++; 660 661 if (test_bit(key, state->key_down)) 662 state->reset_seq_cnt++; 663 } 664 665 /* Disable reset until old keys are not released */ 666 state->reset_canceled = state->reset_seq_cnt != 0; 667 668 state->reset_seq_version = sysrq_reset_seq_version; 669 } 670 671 static void sysrq_do_reset(struct timer_list *t) 672 { 673 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 674 675 state->reset_requested = true; 676 677 orderly_reboot(); 678 } 679 680 static void sysrq_handle_reset_request(struct sysrq_state *state) 681 { 682 if (state->reset_requested) 683 __handle_sysrq(sysrq_xlate[KEY_B], false); 684 685 if (sysrq_reset_downtime_ms) 686 mod_timer(&state->keyreset_timer, 687 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 688 else 689 sysrq_do_reset(&state->keyreset_timer); 690 } 691 692 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 693 unsigned int code, int value) 694 { 695 if (!test_bit(code, state->reset_keybit)) { 696 /* 697 * Pressing any key _not_ in reset sequence cancels 698 * the reset sequence. Also cancelling the timer in 699 * case additional keys were pressed after a reset 700 * has been requested. 701 */ 702 if (value && state->reset_seq_cnt) { 703 state->reset_canceled = true; 704 del_timer(&state->keyreset_timer); 705 } 706 } else if (value == 0) { 707 /* 708 * Key release - all keys in the reset sequence need 709 * to be pressed and held for the reset timeout 710 * to hold. 711 */ 712 del_timer(&state->keyreset_timer); 713 714 if (--state->reset_seq_cnt == 0) 715 state->reset_canceled = false; 716 } else if (value == 1) { 717 /* key press, not autorepeat */ 718 if (++state->reset_seq_cnt == state->reset_seq_len && 719 !state->reset_canceled) { 720 sysrq_handle_reset_request(state); 721 } 722 } 723 } 724 725 #ifdef CONFIG_OF 726 static void sysrq_of_get_keyreset_config(void) 727 { 728 u32 key; 729 struct device_node *np; 730 struct property *prop; 731 const __be32 *p; 732 733 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 734 if (!np) { 735 pr_debug("No sysrq node found"); 736 return; 737 } 738 739 /* Reset in case a __weak definition was present */ 740 sysrq_reset_seq_len = 0; 741 742 of_property_for_each_u32(np, "keyset", prop, p, key) { 743 if (key == KEY_RESERVED || key > KEY_MAX || 744 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 745 break; 746 747 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 748 } 749 750 /* Get reset timeout if any. */ 751 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 752 753 of_node_put(np); 754 } 755 #else 756 static void sysrq_of_get_keyreset_config(void) 757 { 758 } 759 #endif 760 761 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 762 { 763 struct sysrq_state *sysrq = 764 container_of(work, struct sysrq_state, reinject_work); 765 struct input_handle *handle = &sysrq->handle; 766 unsigned int alt_code = sysrq->alt_use; 767 768 if (sysrq->need_reinject) { 769 /* we do not want the assignment to be reordered */ 770 sysrq->reinjecting = true; 771 mb(); 772 773 /* Simulate press and release of Alt + SysRq */ 774 input_inject_event(handle, EV_KEY, alt_code, 1); 775 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 776 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 777 778 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 779 input_inject_event(handle, EV_KEY, alt_code, 0); 780 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 781 782 mb(); 783 sysrq->reinjecting = false; 784 } 785 } 786 787 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 788 unsigned int code, int value) 789 { 790 bool was_active = sysrq->active; 791 bool suppress; 792 793 switch (code) { 794 795 case KEY_LEFTALT: 796 case KEY_RIGHTALT: 797 if (!value) { 798 /* One of ALTs is being released */ 799 if (sysrq->active && code == sysrq->alt_use) 800 sysrq->active = false; 801 802 sysrq->alt = KEY_RESERVED; 803 804 } else if (value != 2) { 805 sysrq->alt = code; 806 sysrq->need_reinject = false; 807 } 808 break; 809 810 case KEY_SYSRQ: 811 if (value == 1 && sysrq->alt != KEY_RESERVED) { 812 sysrq->active = true; 813 sysrq->alt_use = sysrq->alt; 814 /* 815 * If nothing else will be pressed we'll need 816 * to re-inject Alt-SysRq keysroke. 817 */ 818 sysrq->need_reinject = true; 819 } 820 821 /* 822 * Pretend that sysrq was never pressed at all. This 823 * is needed to properly handle KGDB which will try 824 * to release all keys after exiting debugger. If we 825 * do not clear key bit it KGDB will end up sending 826 * release events for Alt and SysRq, potentially 827 * triggering print screen function. 828 */ 829 if (sysrq->active) 830 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 831 832 break; 833 834 default: 835 if (sysrq->active && value && value != 2) { 836 sysrq->need_reinject = false; 837 __handle_sysrq(sysrq_xlate[code], true); 838 } 839 break; 840 } 841 842 suppress = sysrq->active; 843 844 if (!sysrq->active) { 845 846 /* 847 * See if reset sequence has changed since the last time. 848 */ 849 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 850 sysrq_parse_reset_sequence(sysrq); 851 852 /* 853 * If we are not suppressing key presses keep track of 854 * keyboard state so we can release keys that have been 855 * pressed before entering SysRq mode. 856 */ 857 if (value) 858 set_bit(code, sysrq->key_down); 859 else 860 clear_bit(code, sysrq->key_down); 861 862 if (was_active) 863 schedule_work(&sysrq->reinject_work); 864 865 /* Check for reset sequence */ 866 sysrq_detect_reset_sequence(sysrq, code, value); 867 868 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 869 /* 870 * Pass on release events for keys that was pressed before 871 * entering SysRq mode. 872 */ 873 suppress = false; 874 } 875 876 return suppress; 877 } 878 879 static bool sysrq_filter(struct input_handle *handle, 880 unsigned int type, unsigned int code, int value) 881 { 882 struct sysrq_state *sysrq = handle->private; 883 bool suppress; 884 885 /* 886 * Do not filter anything if we are in the process of re-injecting 887 * Alt+SysRq combination. 888 */ 889 if (sysrq->reinjecting) 890 return false; 891 892 switch (type) { 893 894 case EV_SYN: 895 suppress = false; 896 break; 897 898 case EV_KEY: 899 suppress = sysrq_handle_keypress(sysrq, code, value); 900 break; 901 902 default: 903 suppress = sysrq->active; 904 break; 905 } 906 907 return suppress; 908 } 909 910 static int sysrq_connect(struct input_handler *handler, 911 struct input_dev *dev, 912 const struct input_device_id *id) 913 { 914 struct sysrq_state *sysrq; 915 int error; 916 917 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 918 if (!sysrq) 919 return -ENOMEM; 920 921 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 922 923 sysrq->handle.dev = dev; 924 sysrq->handle.handler = handler; 925 sysrq->handle.name = "sysrq"; 926 sysrq->handle.private = sysrq; 927 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 928 929 error = input_register_handle(&sysrq->handle); 930 if (error) { 931 pr_err("Failed to register input sysrq handler, error %d\n", 932 error); 933 goto err_free; 934 } 935 936 error = input_open_device(&sysrq->handle); 937 if (error) { 938 pr_err("Failed to open input device, error %d\n", error); 939 goto err_unregister; 940 } 941 942 return 0; 943 944 err_unregister: 945 input_unregister_handle(&sysrq->handle); 946 err_free: 947 kfree(sysrq); 948 return error; 949 } 950 951 static void sysrq_disconnect(struct input_handle *handle) 952 { 953 struct sysrq_state *sysrq = handle->private; 954 955 input_close_device(handle); 956 cancel_work_sync(&sysrq->reinject_work); 957 del_timer_sync(&sysrq->keyreset_timer); 958 input_unregister_handle(handle); 959 kfree(sysrq); 960 } 961 962 /* 963 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 964 * keyboards have SysRq key predefined and so user may add it to keymap 965 * later, but we expect all such keyboards to have left alt. 966 */ 967 static const struct input_device_id sysrq_ids[] = { 968 { 969 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 970 INPUT_DEVICE_ID_MATCH_KEYBIT, 971 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 972 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 973 }, 974 { }, 975 }; 976 977 static struct input_handler sysrq_handler = { 978 .filter = sysrq_filter, 979 .connect = sysrq_connect, 980 .disconnect = sysrq_disconnect, 981 .name = "sysrq", 982 .id_table = sysrq_ids, 983 }; 984 985 static inline void sysrq_register_handler(void) 986 { 987 int error; 988 989 sysrq_of_get_keyreset_config(); 990 991 error = input_register_handler(&sysrq_handler); 992 if (error) 993 pr_err("Failed to register input handler, error %d", error); 994 } 995 996 static inline void sysrq_unregister_handler(void) 997 { 998 input_unregister_handler(&sysrq_handler); 999 } 1000 1001 static int sysrq_reset_seq_param_set(const char *buffer, 1002 const struct kernel_param *kp) 1003 { 1004 unsigned long val; 1005 int error; 1006 1007 error = kstrtoul(buffer, 0, &val); 1008 if (error < 0) 1009 return error; 1010 1011 if (val > KEY_MAX) 1012 return -EINVAL; 1013 1014 *((unsigned short *)kp->arg) = val; 1015 sysrq_reset_seq_version++; 1016 1017 return 0; 1018 } 1019 1020 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1021 .get = param_get_ushort, 1022 .set = sysrq_reset_seq_param_set, 1023 }; 1024 1025 #define param_check_sysrq_reset_seq(name, p) \ 1026 __param_check(name, p, unsigned short) 1027 1028 /* 1029 * not really modular, but the easiest way to keep compat with existing 1030 * bootargs behaviour is to continue using module_param here. 1031 */ 1032 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1033 &sysrq_reset_seq_len, 0644); 1034 1035 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1036 1037 #else 1038 1039 static inline void sysrq_register_handler(void) 1040 { 1041 } 1042 1043 static inline void sysrq_unregister_handler(void) 1044 { 1045 } 1046 1047 #endif /* CONFIG_INPUT */ 1048 1049 int sysrq_toggle_support(int enable_mask) 1050 { 1051 bool was_enabled = sysrq_on(); 1052 1053 sysrq_enabled = enable_mask; 1054 1055 if (was_enabled != sysrq_on()) { 1056 if (sysrq_on()) 1057 sysrq_register_handler(); 1058 else 1059 sysrq_unregister_handler(); 1060 } 1061 1062 return 0; 1063 } 1064 EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1065 1066 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p, 1067 const struct sysrq_key_op *remove_op_p) 1068 { 1069 int retval; 1070 1071 spin_lock(&sysrq_key_table_lock); 1072 if (__sysrq_get_key_op(key) == remove_op_p) { 1073 __sysrq_put_key_op(key, insert_op_p); 1074 retval = 0; 1075 } else { 1076 retval = -1; 1077 } 1078 spin_unlock(&sysrq_key_table_lock); 1079 1080 /* 1081 * A concurrent __handle_sysrq either got the old op or the new op. 1082 * Wait for it to go away before returning, so the code for an old 1083 * op is not freed (eg. on module unload) while it is in use. 1084 */ 1085 synchronize_rcu(); 1086 1087 return retval; 1088 } 1089 1090 int register_sysrq_key(int key, const struct sysrq_key_op *op_p) 1091 { 1092 return __sysrq_swap_key_ops(key, op_p, NULL); 1093 } 1094 EXPORT_SYMBOL(register_sysrq_key); 1095 1096 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p) 1097 { 1098 return __sysrq_swap_key_ops(key, NULL, op_p); 1099 } 1100 EXPORT_SYMBOL(unregister_sysrq_key); 1101 1102 #ifdef CONFIG_PROC_FS 1103 /* 1104 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1105 */ 1106 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1107 size_t count, loff_t *ppos) 1108 { 1109 if (count) { 1110 char c; 1111 1112 if (get_user(c, buf)) 1113 return -EFAULT; 1114 __handle_sysrq(c, false); 1115 } 1116 1117 return count; 1118 } 1119 1120 static const struct proc_ops sysrq_trigger_proc_ops = { 1121 .proc_write = write_sysrq_trigger, 1122 .proc_lseek = noop_llseek, 1123 }; 1124 1125 static void sysrq_init_procfs(void) 1126 { 1127 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1128 &sysrq_trigger_proc_ops)) 1129 pr_err("Failed to register proc interface\n"); 1130 } 1131 1132 #else 1133 1134 static inline void sysrq_init_procfs(void) 1135 { 1136 } 1137 1138 #endif /* CONFIG_PROC_FS */ 1139 1140 static int __init sysrq_init(void) 1141 { 1142 sysrq_init_procfs(); 1143 1144 if (sysrq_on()) 1145 sysrq_register_handler(); 1146 1147 return 0; 1148 } 1149 device_initcall(sysrq_init); 1150