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/interrupt.h> 19 #include <linux/mm.h> 20 #include <linux/fs.h> 21 #include <linux/mount.h> 22 #include <linux/kdev_t.h> 23 #include <linux/major.h> 24 #include <linux/reboot.h> 25 #include <linux/sysrq.h> 26 #include <linux/kbd_kern.h> 27 #include <linux/proc_fs.h> 28 #include <linux/nmi.h> 29 #include <linux/quotaops.h> 30 #include <linux/perf_event.h> 31 #include <linux/kernel.h> 32 #include <linux/module.h> 33 #include <linux/suspend.h> 34 #include <linux/writeback.h> 35 #include <linux/buffer_head.h> /* for fsync_bdev() */ 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 45 #include <asm/ptrace.h> 46 #include <asm/irq_regs.h> 47 48 /* Whether we react on sysrq keys or just ignore them */ 49 static int __read_mostly sysrq_enabled = 1; 50 static bool __read_mostly sysrq_always_enabled; 51 52 static bool sysrq_on(void) 53 { 54 return sysrq_enabled || sysrq_always_enabled; 55 } 56 57 /* 58 * A value of 1 means 'all', other nonzero values are an op mask: 59 */ 60 static bool sysrq_on_mask(int mask) 61 { 62 return sysrq_always_enabled || 63 sysrq_enabled == 1 || 64 (sysrq_enabled & mask); 65 } 66 67 static int __init sysrq_always_enabled_setup(char *str) 68 { 69 sysrq_always_enabled = true; 70 pr_info("sysrq always enabled.\n"); 71 72 return 1; 73 } 74 75 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 76 77 78 static void sysrq_handle_loglevel(int key) 79 { 80 int i; 81 82 i = key - '0'; 83 console_loglevel = 7; 84 printk("Loglevel set to %d\n", i); 85 console_loglevel = i; 86 } 87 static struct sysrq_key_op sysrq_loglevel_op = { 88 .handler = sysrq_handle_loglevel, 89 .help_msg = "loglevel(0-9)", 90 .action_msg = "Changing Loglevel", 91 .enable_mask = SYSRQ_ENABLE_LOG, 92 }; 93 94 #ifdef CONFIG_VT 95 static void sysrq_handle_SAK(int key) 96 { 97 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 98 schedule_work(SAK_work); 99 } 100 static struct sysrq_key_op sysrq_SAK_op = { 101 .handler = sysrq_handle_SAK, 102 .help_msg = "saK", 103 .action_msg = "SAK", 104 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 105 }; 106 #else 107 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL) 108 #endif 109 110 #ifdef CONFIG_VT 111 static void sysrq_handle_unraw(int key) 112 { 113 struct kbd_struct *kbd = &kbd_table[fg_console]; 114 115 if (kbd) 116 kbd->kbdmode = default_utf8 ? VC_UNICODE : VC_XLATE; 117 } 118 static struct sysrq_key_op sysrq_unraw_op = { 119 .handler = sysrq_handle_unraw, 120 .help_msg = "unRaw", 121 .action_msg = "Keyboard mode set to system default", 122 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 123 }; 124 #else 125 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL) 126 #endif /* CONFIG_VT */ 127 128 static void sysrq_handle_crash(int key) 129 { 130 char *killer = NULL; 131 132 panic_on_oops = 1; /* force panic */ 133 wmb(); 134 *killer = 1; 135 } 136 static struct sysrq_key_op sysrq_crash_op = { 137 .handler = sysrq_handle_crash, 138 .help_msg = "Crash", 139 .action_msg = "Trigger a crash", 140 .enable_mask = SYSRQ_ENABLE_DUMP, 141 }; 142 143 static void sysrq_handle_reboot(int key) 144 { 145 lockdep_off(); 146 local_irq_enable(); 147 emergency_restart(); 148 } 149 static struct sysrq_key_op sysrq_reboot_op = { 150 .handler = sysrq_handle_reboot, 151 .help_msg = "reBoot", 152 .action_msg = "Resetting", 153 .enable_mask = SYSRQ_ENABLE_BOOT, 154 }; 155 156 static void sysrq_handle_sync(int key) 157 { 158 emergency_sync(); 159 } 160 static struct sysrq_key_op sysrq_sync_op = { 161 .handler = sysrq_handle_sync, 162 .help_msg = "Sync", 163 .action_msg = "Emergency Sync", 164 .enable_mask = SYSRQ_ENABLE_SYNC, 165 }; 166 167 static void sysrq_handle_show_timers(int key) 168 { 169 sysrq_timer_list_show(); 170 } 171 172 static struct sysrq_key_op sysrq_show_timers_op = { 173 .handler = sysrq_handle_show_timers, 174 .help_msg = "show-all-timers(Q)", 175 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 176 }; 177 178 static void sysrq_handle_mountro(int key) 179 { 180 emergency_remount(); 181 } 182 static struct sysrq_key_op sysrq_mountro_op = { 183 .handler = sysrq_handle_mountro, 184 .help_msg = "Unmount", 185 .action_msg = "Emergency Remount R/O", 186 .enable_mask = SYSRQ_ENABLE_REMOUNT, 187 }; 188 189 #ifdef CONFIG_LOCKDEP 190 static void sysrq_handle_showlocks(int key) 191 { 192 debug_show_all_locks(); 193 } 194 195 static struct sysrq_key_op sysrq_showlocks_op = { 196 .handler = sysrq_handle_showlocks, 197 .help_msg = "show-all-locks(D)", 198 .action_msg = "Show Locks Held", 199 }; 200 #else 201 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 202 #endif 203 204 #ifdef CONFIG_SMP 205 static DEFINE_SPINLOCK(show_lock); 206 207 static void showacpu(void *dummy) 208 { 209 unsigned long flags; 210 211 /* Idle CPUs have no interesting backtrace. */ 212 if (idle_cpu(smp_processor_id())) 213 return; 214 215 spin_lock_irqsave(&show_lock, flags); 216 printk(KERN_INFO "CPU%d:\n", smp_processor_id()); 217 show_stack(NULL, NULL); 218 spin_unlock_irqrestore(&show_lock, flags); 219 } 220 221 static void sysrq_showregs_othercpus(struct work_struct *dummy) 222 { 223 smp_call_function(showacpu, NULL, 0); 224 } 225 226 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 227 228 static void sysrq_handle_showallcpus(int key) 229 { 230 /* 231 * Fall back to the workqueue based printing if the 232 * backtrace printing did not succeed or the 233 * architecture has no support for it: 234 */ 235 if (!trigger_all_cpu_backtrace()) { 236 struct pt_regs *regs = get_irq_regs(); 237 238 if (regs) { 239 printk(KERN_INFO "CPU%d:\n", smp_processor_id()); 240 show_regs(regs); 241 } 242 schedule_work(&sysrq_showallcpus); 243 } 244 } 245 246 static struct sysrq_key_op sysrq_showallcpus_op = { 247 .handler = sysrq_handle_showallcpus, 248 .help_msg = "show-backtrace-all-active-cpus(L)", 249 .action_msg = "Show backtrace of all active CPUs", 250 .enable_mask = SYSRQ_ENABLE_DUMP, 251 }; 252 #endif 253 254 static void sysrq_handle_showregs(int key) 255 { 256 struct pt_regs *regs = get_irq_regs(); 257 if (regs) 258 show_regs(regs); 259 perf_event_print_debug(); 260 } 261 static struct sysrq_key_op sysrq_showregs_op = { 262 .handler = sysrq_handle_showregs, 263 .help_msg = "show-registers(P)", 264 .action_msg = "Show Regs", 265 .enable_mask = SYSRQ_ENABLE_DUMP, 266 }; 267 268 static void sysrq_handle_showstate(int key) 269 { 270 show_state(); 271 } 272 static struct sysrq_key_op sysrq_showstate_op = { 273 .handler = sysrq_handle_showstate, 274 .help_msg = "show-task-states(T)", 275 .action_msg = "Show State", 276 .enable_mask = SYSRQ_ENABLE_DUMP, 277 }; 278 279 static void sysrq_handle_showstate_blocked(int key) 280 { 281 show_state_filter(TASK_UNINTERRUPTIBLE); 282 } 283 static struct sysrq_key_op sysrq_showstate_blocked_op = { 284 .handler = sysrq_handle_showstate_blocked, 285 .help_msg = "show-blocked-tasks(W)", 286 .action_msg = "Show Blocked State", 287 .enable_mask = SYSRQ_ENABLE_DUMP, 288 }; 289 290 #ifdef CONFIG_TRACING 291 #include <linux/ftrace.h> 292 293 static void sysrq_ftrace_dump(int key) 294 { 295 ftrace_dump(DUMP_ALL); 296 } 297 static struct sysrq_key_op sysrq_ftrace_dump_op = { 298 .handler = sysrq_ftrace_dump, 299 .help_msg = "dump-ftrace-buffer(Z)", 300 .action_msg = "Dump ftrace buffer", 301 .enable_mask = SYSRQ_ENABLE_DUMP, 302 }; 303 #else 304 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 305 #endif 306 307 static void sysrq_handle_showmem(int key) 308 { 309 show_mem(); 310 } 311 static struct sysrq_key_op sysrq_showmem_op = { 312 .handler = sysrq_handle_showmem, 313 .help_msg = "show-memory-usage(M)", 314 .action_msg = "Show Memory", 315 .enable_mask = SYSRQ_ENABLE_DUMP, 316 }; 317 318 /* 319 * Signal sysrq helper function. Sends a signal to all user processes. 320 */ 321 static void send_sig_all(int sig) 322 { 323 struct task_struct *p; 324 325 for_each_process(p) { 326 if (p->mm && !is_global_init(p)) 327 /* Not swapper, init nor kernel thread */ 328 force_sig(sig, p); 329 } 330 } 331 332 static void sysrq_handle_term(int key) 333 { 334 send_sig_all(SIGTERM); 335 console_loglevel = 8; 336 } 337 static struct sysrq_key_op sysrq_term_op = { 338 .handler = sysrq_handle_term, 339 .help_msg = "terminate-all-tasks(E)", 340 .action_msg = "Terminate All Tasks", 341 .enable_mask = SYSRQ_ENABLE_SIGNAL, 342 }; 343 344 static void moom_callback(struct work_struct *ignored) 345 { 346 out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0, NULL); 347 } 348 349 static DECLARE_WORK(moom_work, moom_callback); 350 351 static void sysrq_handle_moom(int key) 352 { 353 schedule_work(&moom_work); 354 } 355 static struct sysrq_key_op sysrq_moom_op = { 356 .handler = sysrq_handle_moom, 357 .help_msg = "memory-full-oom-kill(F)", 358 .action_msg = "Manual OOM execution", 359 .enable_mask = SYSRQ_ENABLE_SIGNAL, 360 }; 361 362 #ifdef CONFIG_BLOCK 363 static void sysrq_handle_thaw(int key) 364 { 365 emergency_thaw_all(); 366 } 367 static struct sysrq_key_op sysrq_thaw_op = { 368 .handler = sysrq_handle_thaw, 369 .help_msg = "thaw-filesystems(J)", 370 .action_msg = "Emergency Thaw of all frozen filesystems", 371 .enable_mask = SYSRQ_ENABLE_SIGNAL, 372 }; 373 #endif 374 375 static void sysrq_handle_kill(int key) 376 { 377 send_sig_all(SIGKILL); 378 console_loglevel = 8; 379 } 380 static struct sysrq_key_op sysrq_kill_op = { 381 .handler = sysrq_handle_kill, 382 .help_msg = "kill-all-tasks(I)", 383 .action_msg = "Kill All Tasks", 384 .enable_mask = SYSRQ_ENABLE_SIGNAL, 385 }; 386 387 static void sysrq_handle_unrt(int key) 388 { 389 normalize_rt_tasks(); 390 } 391 static struct sysrq_key_op sysrq_unrt_op = { 392 .handler = sysrq_handle_unrt, 393 .help_msg = "nice-all-RT-tasks(N)", 394 .action_msg = "Nice All RT Tasks", 395 .enable_mask = SYSRQ_ENABLE_RTNICE, 396 }; 397 398 /* Key Operations table and lock */ 399 static DEFINE_SPINLOCK(sysrq_key_table_lock); 400 401 static struct sysrq_key_op *sysrq_key_table[36] = { 402 &sysrq_loglevel_op, /* 0 */ 403 &sysrq_loglevel_op, /* 1 */ 404 &sysrq_loglevel_op, /* 2 */ 405 &sysrq_loglevel_op, /* 3 */ 406 &sysrq_loglevel_op, /* 4 */ 407 &sysrq_loglevel_op, /* 5 */ 408 &sysrq_loglevel_op, /* 6 */ 409 &sysrq_loglevel_op, /* 7 */ 410 &sysrq_loglevel_op, /* 8 */ 411 &sysrq_loglevel_op, /* 9 */ 412 413 /* 414 * a: Don't use for system provided sysrqs, it is handled specially on 415 * sparc and will never arrive. 416 */ 417 NULL, /* a */ 418 &sysrq_reboot_op, /* b */ 419 &sysrq_crash_op, /* c & ibm_emac driver debug */ 420 &sysrq_showlocks_op, /* d */ 421 &sysrq_term_op, /* e */ 422 &sysrq_moom_op, /* f */ 423 /* g: May be registered for the kernel debugger */ 424 NULL, /* g */ 425 NULL, /* h - reserved for help */ 426 &sysrq_kill_op, /* i */ 427 #ifdef CONFIG_BLOCK 428 &sysrq_thaw_op, /* j */ 429 #else 430 NULL, /* j */ 431 #endif 432 &sysrq_SAK_op, /* k */ 433 #ifdef CONFIG_SMP 434 &sysrq_showallcpus_op, /* l */ 435 #else 436 NULL, /* l */ 437 #endif 438 &sysrq_showmem_op, /* m */ 439 &sysrq_unrt_op, /* n */ 440 /* o: This will often be registered as 'Off' at init time */ 441 NULL, /* o */ 442 &sysrq_showregs_op, /* p */ 443 &sysrq_show_timers_op, /* q */ 444 &sysrq_unraw_op, /* r */ 445 &sysrq_sync_op, /* s */ 446 &sysrq_showstate_op, /* t */ 447 &sysrq_mountro_op, /* u */ 448 /* v: May be registered for frame buffer console restore */ 449 NULL, /* v */ 450 &sysrq_showstate_blocked_op, /* w */ 451 /* x: May be registered on ppc/powerpc for xmon */ 452 NULL, /* x */ 453 /* y: May be registered on sparc64 for global register dump */ 454 NULL, /* y */ 455 &sysrq_ftrace_dump_op, /* z */ 456 }; 457 458 /* key2index calculation, -1 on invalid index */ 459 static int sysrq_key_table_key2index(int key) 460 { 461 int retval; 462 463 if ((key >= '0') && (key <= '9')) 464 retval = key - '0'; 465 else if ((key >= 'a') && (key <= 'z')) 466 retval = key + 10 - 'a'; 467 else 468 retval = -1; 469 return retval; 470 } 471 472 /* 473 * get and put functions for the table, exposed to modules. 474 */ 475 struct sysrq_key_op *__sysrq_get_key_op(int key) 476 { 477 struct sysrq_key_op *op_p = NULL; 478 int i; 479 480 i = sysrq_key_table_key2index(key); 481 if (i != -1) 482 op_p = sysrq_key_table[i]; 483 484 return op_p; 485 } 486 487 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 488 { 489 int i = sysrq_key_table_key2index(key); 490 491 if (i != -1) 492 sysrq_key_table[i] = op_p; 493 } 494 495 void __handle_sysrq(int key, bool check_mask) 496 { 497 struct sysrq_key_op *op_p; 498 int orig_log_level; 499 int i; 500 unsigned long flags; 501 502 spin_lock_irqsave(&sysrq_key_table_lock, flags); 503 /* 504 * Raise the apparent loglevel to maximum so that the sysrq header 505 * is shown to provide the user with positive feedback. We do not 506 * simply emit this at KERN_EMERG as that would change message 507 * routing in the consumers of /proc/kmsg. 508 */ 509 orig_log_level = console_loglevel; 510 console_loglevel = 7; 511 printk(KERN_INFO "SysRq : "); 512 513 op_p = __sysrq_get_key_op(key); 514 if (op_p) { 515 /* 516 * Should we check for enabled operations (/proc/sysrq-trigger 517 * should not) and is the invoked operation enabled? 518 */ 519 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 520 printk("%s\n", op_p->action_msg); 521 console_loglevel = orig_log_level; 522 op_p->handler(key); 523 } else { 524 printk("This sysrq operation is disabled.\n"); 525 } 526 } else { 527 printk("HELP : "); 528 /* Only print the help msg once per handler */ 529 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 530 if (sysrq_key_table[i]) { 531 int j; 532 533 for (j = 0; sysrq_key_table[i] != 534 sysrq_key_table[j]; j++) 535 ; 536 if (j != i) 537 continue; 538 printk("%s ", sysrq_key_table[i]->help_msg); 539 } 540 } 541 printk("\n"); 542 console_loglevel = orig_log_level; 543 } 544 spin_unlock_irqrestore(&sysrq_key_table_lock, flags); 545 } 546 547 void handle_sysrq(int key) 548 { 549 if (sysrq_on()) 550 __handle_sysrq(key, true); 551 } 552 EXPORT_SYMBOL(handle_sysrq); 553 554 #ifdef CONFIG_INPUT 555 556 /* Simple translation table for the SysRq keys */ 557 static const unsigned char sysrq_xlate[KEY_MAX + 1] = 558 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 559 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 560 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 561 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 562 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 563 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 564 "\r\000/"; /* 0x60 - 0x6f */ 565 566 static bool sysrq_down; 567 static int sysrq_alt_use; 568 static int sysrq_alt; 569 static DEFINE_SPINLOCK(sysrq_event_lock); 570 571 static bool sysrq_filter(struct input_handle *handle, unsigned int type, 572 unsigned int code, int value) 573 { 574 bool suppress; 575 576 /* We are called with interrupts disabled, just take the lock */ 577 spin_lock(&sysrq_event_lock); 578 579 if (type != EV_KEY) 580 goto out; 581 582 switch (code) { 583 584 case KEY_LEFTALT: 585 case KEY_RIGHTALT: 586 if (value) 587 sysrq_alt = code; 588 else { 589 if (sysrq_down && code == sysrq_alt_use) 590 sysrq_down = false; 591 592 sysrq_alt = 0; 593 } 594 break; 595 596 case KEY_SYSRQ: 597 if (value == 1 && sysrq_alt) { 598 sysrq_down = true; 599 sysrq_alt_use = sysrq_alt; 600 } 601 break; 602 603 default: 604 if (sysrq_down && value && value != 2) 605 __handle_sysrq(sysrq_xlate[code], true); 606 break; 607 } 608 609 out: 610 suppress = sysrq_down; 611 spin_unlock(&sysrq_event_lock); 612 613 return suppress; 614 } 615 616 static int sysrq_connect(struct input_handler *handler, 617 struct input_dev *dev, 618 const struct input_device_id *id) 619 { 620 struct input_handle *handle; 621 int error; 622 623 sysrq_down = false; 624 sysrq_alt = 0; 625 626 handle = kzalloc(sizeof(struct input_handle), GFP_KERNEL); 627 if (!handle) 628 return -ENOMEM; 629 630 handle->dev = dev; 631 handle->handler = handler; 632 handle->name = "sysrq"; 633 634 error = input_register_handle(handle); 635 if (error) { 636 pr_err("Failed to register input sysrq handler, error %d\n", 637 error); 638 goto err_free; 639 } 640 641 error = input_open_device(handle); 642 if (error) { 643 pr_err("Failed to open input device, error %d\n", error); 644 goto err_unregister; 645 } 646 647 return 0; 648 649 err_unregister: 650 input_unregister_handle(handle); 651 err_free: 652 kfree(handle); 653 return error; 654 } 655 656 static void sysrq_disconnect(struct input_handle *handle) 657 { 658 input_close_device(handle); 659 input_unregister_handle(handle); 660 kfree(handle); 661 } 662 663 /* 664 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 665 * keyboards have SysRq key predefined and so user may add it to keymap 666 * later, but we expect all such keyboards to have left alt. 667 */ 668 static const struct input_device_id sysrq_ids[] = { 669 { 670 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 671 INPUT_DEVICE_ID_MATCH_KEYBIT, 672 .evbit = { BIT_MASK(EV_KEY) }, 673 .keybit = { BIT_MASK(KEY_LEFTALT) }, 674 }, 675 { }, 676 }; 677 678 static struct input_handler sysrq_handler = { 679 .filter = sysrq_filter, 680 .connect = sysrq_connect, 681 .disconnect = sysrq_disconnect, 682 .name = "sysrq", 683 .id_table = sysrq_ids, 684 }; 685 686 static bool sysrq_handler_registered; 687 688 static inline void sysrq_register_handler(void) 689 { 690 int error; 691 692 error = input_register_handler(&sysrq_handler); 693 if (error) 694 pr_err("Failed to register input handler, error %d", error); 695 else 696 sysrq_handler_registered = true; 697 } 698 699 static inline void sysrq_unregister_handler(void) 700 { 701 if (sysrq_handler_registered) { 702 input_unregister_handler(&sysrq_handler); 703 sysrq_handler_registered = false; 704 } 705 } 706 707 #else 708 709 static inline void sysrq_register_handler(void) 710 { 711 } 712 713 static inline void sysrq_unregister_handler(void) 714 { 715 } 716 717 #endif /* CONFIG_INPUT */ 718 719 int sysrq_toggle_support(int enable_mask) 720 { 721 bool was_enabled = sysrq_on(); 722 723 sysrq_enabled = enable_mask; 724 725 if (was_enabled != sysrq_on()) { 726 if (sysrq_on()) 727 sysrq_register_handler(); 728 else 729 sysrq_unregister_handler(); 730 } 731 732 return 0; 733 } 734 735 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 736 struct sysrq_key_op *remove_op_p) 737 { 738 int retval; 739 unsigned long flags; 740 741 spin_lock_irqsave(&sysrq_key_table_lock, flags); 742 if (__sysrq_get_key_op(key) == remove_op_p) { 743 __sysrq_put_key_op(key, insert_op_p); 744 retval = 0; 745 } else { 746 retval = -1; 747 } 748 spin_unlock_irqrestore(&sysrq_key_table_lock, flags); 749 return retval; 750 } 751 752 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 753 { 754 return __sysrq_swap_key_ops(key, op_p, NULL); 755 } 756 EXPORT_SYMBOL(register_sysrq_key); 757 758 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 759 { 760 return __sysrq_swap_key_ops(key, NULL, op_p); 761 } 762 EXPORT_SYMBOL(unregister_sysrq_key); 763 764 #ifdef CONFIG_PROC_FS 765 /* 766 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 767 */ 768 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 769 size_t count, loff_t *ppos) 770 { 771 if (count) { 772 char c; 773 774 if (get_user(c, buf)) 775 return -EFAULT; 776 __handle_sysrq(c, false); 777 } 778 779 return count; 780 } 781 782 static const struct file_operations proc_sysrq_trigger_operations = { 783 .write = write_sysrq_trigger, 784 .llseek = noop_llseek, 785 }; 786 787 static void sysrq_init_procfs(void) 788 { 789 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 790 &proc_sysrq_trigger_operations)) 791 pr_err("Failed to register proc interface\n"); 792 } 793 794 #else 795 796 static inline void sysrq_init_procfs(void) 797 { 798 } 799 800 #endif /* CONFIG_PROC_FS */ 801 802 static int __init sysrq_init(void) 803 { 804 sysrq_init_procfs(); 805 806 if (sysrq_on()) 807 sysrq_register_handler(); 808 809 return 0; 810 } 811 module_init(sysrq_init); 812