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 47 #include <asm/ptrace.h> 48 #include <asm/irq_regs.h> 49 50 /* Whether we react on sysrq keys or just ignore them */ 51 static int __read_mostly sysrq_enabled = SYSRQ_DEFAULT_ENABLE; 52 static bool __read_mostly sysrq_always_enabled; 53 54 static bool sysrq_on(void) 55 { 56 return sysrq_enabled || sysrq_always_enabled; 57 } 58 59 /* 60 * A value of 1 means 'all', other nonzero values are an op mask: 61 */ 62 static bool sysrq_on_mask(int mask) 63 { 64 return sysrq_always_enabled || 65 sysrq_enabled == 1 || 66 (sysrq_enabled & mask); 67 } 68 69 static int __init sysrq_always_enabled_setup(char *str) 70 { 71 sysrq_always_enabled = true; 72 pr_info("sysrq always enabled.\n"); 73 74 return 1; 75 } 76 77 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 78 79 80 static void sysrq_handle_loglevel(int key) 81 { 82 int i; 83 84 i = key - '0'; 85 console_loglevel = 7; 86 printk("Loglevel set to %d\n", i); 87 console_loglevel = i; 88 } 89 static struct sysrq_key_op sysrq_loglevel_op = { 90 .handler = sysrq_handle_loglevel, 91 .help_msg = "loglevel(0-9)", 92 .action_msg = "Changing Loglevel", 93 .enable_mask = SYSRQ_ENABLE_LOG, 94 }; 95 96 #ifdef CONFIG_VT 97 static void sysrq_handle_SAK(int key) 98 { 99 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 100 schedule_work(SAK_work); 101 } 102 static struct sysrq_key_op sysrq_SAK_op = { 103 .handler = sysrq_handle_SAK, 104 .help_msg = "saK", 105 .action_msg = "SAK", 106 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 107 }; 108 #else 109 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL) 110 #endif 111 112 #ifdef CONFIG_VT 113 static void sysrq_handle_unraw(int key) 114 { 115 vt_reset_unicode(fg_console); 116 } 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(0); 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 read_lock(&tasklist_lock); 326 for_each_process(p) { 327 if (p->flags & PF_KTHREAD) 328 continue; 329 if (is_global_init(p)) 330 continue; 331 332 do_send_sig_info(sig, SEND_SIG_FORCED, p, true); 333 } 334 read_unlock(&tasklist_lock); 335 } 336 337 static void sysrq_handle_term(int key) 338 { 339 send_sig_all(SIGTERM); 340 console_loglevel = 8; 341 } 342 static struct sysrq_key_op sysrq_term_op = { 343 .handler = sysrq_handle_term, 344 .help_msg = "terminate-all-tasks(E)", 345 .action_msg = "Terminate All Tasks", 346 .enable_mask = SYSRQ_ENABLE_SIGNAL, 347 }; 348 349 static void moom_callback(struct work_struct *ignored) 350 { 351 out_of_memory(node_zonelist(first_online_node, GFP_KERNEL), GFP_KERNEL, 352 0, NULL, true); 353 } 354 355 static DECLARE_WORK(moom_work, moom_callback); 356 357 static void sysrq_handle_moom(int key) 358 { 359 schedule_work(&moom_work); 360 } 361 static struct sysrq_key_op sysrq_moom_op = { 362 .handler = sysrq_handle_moom, 363 .help_msg = "memory-full-oom-kill(F)", 364 .action_msg = "Manual OOM execution", 365 .enable_mask = SYSRQ_ENABLE_SIGNAL, 366 }; 367 368 #ifdef CONFIG_BLOCK 369 static void sysrq_handle_thaw(int key) 370 { 371 emergency_thaw_all(); 372 } 373 static struct sysrq_key_op sysrq_thaw_op = { 374 .handler = sysrq_handle_thaw, 375 .help_msg = "thaw-filesystems(J)", 376 .action_msg = "Emergency Thaw of all frozen filesystems", 377 .enable_mask = SYSRQ_ENABLE_SIGNAL, 378 }; 379 #endif 380 381 static void sysrq_handle_kill(int key) 382 { 383 send_sig_all(SIGKILL); 384 console_loglevel = 8; 385 } 386 static struct sysrq_key_op sysrq_kill_op = { 387 .handler = sysrq_handle_kill, 388 .help_msg = "kill-all-tasks(I)", 389 .action_msg = "Kill All Tasks", 390 .enable_mask = SYSRQ_ENABLE_SIGNAL, 391 }; 392 393 static void sysrq_handle_unrt(int key) 394 { 395 normalize_rt_tasks(); 396 } 397 static struct sysrq_key_op sysrq_unrt_op = { 398 .handler = sysrq_handle_unrt, 399 .help_msg = "nice-all-RT-tasks(N)", 400 .action_msg = "Nice All RT Tasks", 401 .enable_mask = SYSRQ_ENABLE_RTNICE, 402 }; 403 404 /* Key Operations table and lock */ 405 static DEFINE_SPINLOCK(sysrq_key_table_lock); 406 407 static struct sysrq_key_op *sysrq_key_table[36] = { 408 &sysrq_loglevel_op, /* 0 */ 409 &sysrq_loglevel_op, /* 1 */ 410 &sysrq_loglevel_op, /* 2 */ 411 &sysrq_loglevel_op, /* 3 */ 412 &sysrq_loglevel_op, /* 4 */ 413 &sysrq_loglevel_op, /* 5 */ 414 &sysrq_loglevel_op, /* 6 */ 415 &sysrq_loglevel_op, /* 7 */ 416 &sysrq_loglevel_op, /* 8 */ 417 &sysrq_loglevel_op, /* 9 */ 418 419 /* 420 * a: Don't use for system provided sysrqs, it is handled specially on 421 * sparc and will never arrive. 422 */ 423 NULL, /* a */ 424 &sysrq_reboot_op, /* b */ 425 &sysrq_crash_op, /* c & ibm_emac driver debug */ 426 &sysrq_showlocks_op, /* d */ 427 &sysrq_term_op, /* e */ 428 &sysrq_moom_op, /* f */ 429 /* g: May be registered for the kernel debugger */ 430 NULL, /* g */ 431 NULL, /* h - reserved for help */ 432 &sysrq_kill_op, /* i */ 433 #ifdef CONFIG_BLOCK 434 &sysrq_thaw_op, /* j */ 435 #else 436 NULL, /* j */ 437 #endif 438 &sysrq_SAK_op, /* k */ 439 #ifdef CONFIG_SMP 440 &sysrq_showallcpus_op, /* l */ 441 #else 442 NULL, /* l */ 443 #endif 444 &sysrq_showmem_op, /* m */ 445 &sysrq_unrt_op, /* n */ 446 /* o: This will often be registered as 'Off' at init time */ 447 NULL, /* o */ 448 &sysrq_showregs_op, /* p */ 449 &sysrq_show_timers_op, /* q */ 450 &sysrq_unraw_op, /* r */ 451 &sysrq_sync_op, /* s */ 452 &sysrq_showstate_op, /* t */ 453 &sysrq_mountro_op, /* u */ 454 /* v: May be registered for frame buffer console restore */ 455 NULL, /* v */ 456 &sysrq_showstate_blocked_op, /* w */ 457 /* x: May be registered on ppc/powerpc for xmon */ 458 /* x: May be registered on sparc64 for global PMU dump */ 459 NULL, /* x */ 460 /* y: May be registered on sparc64 for global register dump */ 461 NULL, /* y */ 462 &sysrq_ftrace_dump_op, /* z */ 463 }; 464 465 /* key2index calculation, -1 on invalid index */ 466 static int sysrq_key_table_key2index(int key) 467 { 468 int retval; 469 470 if ((key >= '0') && (key <= '9')) 471 retval = key - '0'; 472 else if ((key >= 'a') && (key <= 'z')) 473 retval = key + 10 - 'a'; 474 else 475 retval = -1; 476 return retval; 477 } 478 479 /* 480 * get and put functions for the table, exposed to modules. 481 */ 482 struct sysrq_key_op *__sysrq_get_key_op(int key) 483 { 484 struct sysrq_key_op *op_p = NULL; 485 int i; 486 487 i = sysrq_key_table_key2index(key); 488 if (i != -1) 489 op_p = sysrq_key_table[i]; 490 491 return op_p; 492 } 493 494 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 495 { 496 int i = sysrq_key_table_key2index(key); 497 498 if (i != -1) 499 sysrq_key_table[i] = op_p; 500 } 501 502 void __handle_sysrq(int key, bool check_mask) 503 { 504 struct sysrq_key_op *op_p; 505 int orig_log_level; 506 int i; 507 unsigned long flags; 508 509 spin_lock_irqsave(&sysrq_key_table_lock, flags); 510 /* 511 * Raise the apparent loglevel to maximum so that the sysrq header 512 * is shown to provide the user with positive feedback. We do not 513 * simply emit this at KERN_EMERG as that would change message 514 * routing in the consumers of /proc/kmsg. 515 */ 516 orig_log_level = console_loglevel; 517 console_loglevel = 7; 518 printk(KERN_INFO "SysRq : "); 519 520 op_p = __sysrq_get_key_op(key); 521 if (op_p) { 522 /* 523 * Should we check for enabled operations (/proc/sysrq-trigger 524 * should not) and is the invoked operation enabled? 525 */ 526 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 527 printk("%s\n", op_p->action_msg); 528 console_loglevel = orig_log_level; 529 op_p->handler(key); 530 } else { 531 printk("This sysrq operation is disabled.\n"); 532 } 533 } else { 534 printk("HELP : "); 535 /* Only print the help msg once per handler */ 536 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 537 if (sysrq_key_table[i]) { 538 int j; 539 540 for (j = 0; sysrq_key_table[i] != 541 sysrq_key_table[j]; j++) 542 ; 543 if (j != i) 544 continue; 545 printk("%s ", sysrq_key_table[i]->help_msg); 546 } 547 } 548 printk("\n"); 549 console_loglevel = orig_log_level; 550 } 551 spin_unlock_irqrestore(&sysrq_key_table_lock, flags); 552 } 553 554 void handle_sysrq(int key) 555 { 556 if (sysrq_on()) 557 __handle_sysrq(key, true); 558 } 559 EXPORT_SYMBOL(handle_sysrq); 560 561 #ifdef CONFIG_INPUT 562 563 /* Simple translation table for the SysRq keys */ 564 static const unsigned char sysrq_xlate[KEY_CNT] = 565 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 566 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 567 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 568 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 569 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 570 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 571 "\r\000/"; /* 0x60 - 0x6f */ 572 573 struct sysrq_state { 574 struct input_handle handle; 575 struct work_struct reinject_work; 576 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 577 unsigned int alt; 578 unsigned int alt_use; 579 bool active; 580 bool need_reinject; 581 bool reinjecting; 582 583 /* reset sequence handling */ 584 bool reset_canceled; 585 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 586 int reset_seq_len; 587 int reset_seq_cnt; 588 int reset_seq_version; 589 }; 590 591 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 592 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 593 static unsigned int sysrq_reset_seq_len; 594 static unsigned int sysrq_reset_seq_version = 1; 595 596 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 597 { 598 int i; 599 unsigned short key; 600 601 state->reset_seq_cnt = 0; 602 603 for (i = 0; i < sysrq_reset_seq_len; i++) { 604 key = sysrq_reset_seq[i]; 605 606 if (key == KEY_RESERVED || key > KEY_MAX) 607 break; 608 609 __set_bit(key, state->reset_keybit); 610 state->reset_seq_len++; 611 612 if (test_bit(key, state->key_down)) 613 state->reset_seq_cnt++; 614 } 615 616 /* Disable reset until old keys are not released */ 617 state->reset_canceled = state->reset_seq_cnt != 0; 618 619 state->reset_seq_version = sysrq_reset_seq_version; 620 } 621 622 static bool sysrq_detect_reset_sequence(struct sysrq_state *state, 623 unsigned int code, int value) 624 { 625 if (!test_bit(code, state->reset_keybit)) { 626 /* 627 * Pressing any key _not_ in reset sequence cancels 628 * the reset sequence. 629 */ 630 if (value && state->reset_seq_cnt) 631 state->reset_canceled = true; 632 } else if (value == 0) { 633 /* key release */ 634 if (--state->reset_seq_cnt == 0) 635 state->reset_canceled = false; 636 } else if (value == 1) { 637 /* key press, not autorepeat */ 638 if (++state->reset_seq_cnt == state->reset_seq_len && 639 !state->reset_canceled) { 640 return true; 641 } 642 } 643 644 return false; 645 } 646 647 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 648 { 649 struct sysrq_state *sysrq = 650 container_of(work, struct sysrq_state, reinject_work); 651 struct input_handle *handle = &sysrq->handle; 652 unsigned int alt_code = sysrq->alt_use; 653 654 if (sysrq->need_reinject) { 655 /* we do not want the assignment to be reordered */ 656 sysrq->reinjecting = true; 657 mb(); 658 659 /* Simulate press and release of Alt + SysRq */ 660 input_inject_event(handle, EV_KEY, alt_code, 1); 661 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 662 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 663 664 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 665 input_inject_event(handle, EV_KEY, alt_code, 0); 666 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 667 668 mb(); 669 sysrq->reinjecting = false; 670 } 671 } 672 673 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 674 unsigned int code, int value) 675 { 676 bool was_active = sysrq->active; 677 bool suppress; 678 679 switch (code) { 680 681 case KEY_LEFTALT: 682 case KEY_RIGHTALT: 683 if (!value) { 684 /* One of ALTs is being released */ 685 if (sysrq->active && code == sysrq->alt_use) 686 sysrq->active = false; 687 688 sysrq->alt = KEY_RESERVED; 689 690 } else if (value != 2) { 691 sysrq->alt = code; 692 sysrq->need_reinject = false; 693 } 694 break; 695 696 case KEY_SYSRQ: 697 if (value == 1 && sysrq->alt != KEY_RESERVED) { 698 sysrq->active = true; 699 sysrq->alt_use = sysrq->alt; 700 /* 701 * If nothing else will be pressed we'll need 702 * to re-inject Alt-SysRq keysroke. 703 */ 704 sysrq->need_reinject = true; 705 } 706 707 /* 708 * Pretend that sysrq was never pressed at all. This 709 * is needed to properly handle KGDB which will try 710 * to release all keys after exiting debugger. If we 711 * do not clear key bit it KGDB will end up sending 712 * release events for Alt and SysRq, potentially 713 * triggering print screen function. 714 */ 715 if (sysrq->active) 716 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 717 718 break; 719 720 default: 721 if (sysrq->active && value && value != 2) { 722 sysrq->need_reinject = false; 723 __handle_sysrq(sysrq_xlate[code], true); 724 } 725 break; 726 } 727 728 suppress = sysrq->active; 729 730 if (!sysrq->active) { 731 732 /* 733 * See if reset sequence has changed since the last time. 734 */ 735 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 736 sysrq_parse_reset_sequence(sysrq); 737 738 /* 739 * If we are not suppressing key presses keep track of 740 * keyboard state so we can release keys that have been 741 * pressed before entering SysRq mode. 742 */ 743 if (value) 744 set_bit(code, sysrq->key_down); 745 else 746 clear_bit(code, sysrq->key_down); 747 748 if (was_active) 749 schedule_work(&sysrq->reinject_work); 750 751 if (sysrq_detect_reset_sequence(sysrq, code, value)) { 752 /* Force emergency reboot */ 753 __handle_sysrq(sysrq_xlate[KEY_B], false); 754 } 755 756 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 757 /* 758 * Pass on release events for keys that was pressed before 759 * entering SysRq mode. 760 */ 761 suppress = false; 762 } 763 764 return suppress; 765 } 766 767 static bool sysrq_filter(struct input_handle *handle, 768 unsigned int type, unsigned int code, int value) 769 { 770 struct sysrq_state *sysrq = handle->private; 771 bool suppress; 772 773 /* 774 * Do not filter anything if we are in the process of re-injecting 775 * Alt+SysRq combination. 776 */ 777 if (sysrq->reinjecting) 778 return false; 779 780 switch (type) { 781 782 case EV_SYN: 783 suppress = false; 784 break; 785 786 case EV_KEY: 787 suppress = sysrq_handle_keypress(sysrq, code, value); 788 break; 789 790 default: 791 suppress = sysrq->active; 792 break; 793 } 794 795 return suppress; 796 } 797 798 static int sysrq_connect(struct input_handler *handler, 799 struct input_dev *dev, 800 const struct input_device_id *id) 801 { 802 struct sysrq_state *sysrq; 803 int error; 804 805 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 806 if (!sysrq) 807 return -ENOMEM; 808 809 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 810 811 sysrq->handle.dev = dev; 812 sysrq->handle.handler = handler; 813 sysrq->handle.name = "sysrq"; 814 sysrq->handle.private = sysrq; 815 816 error = input_register_handle(&sysrq->handle); 817 if (error) { 818 pr_err("Failed to register input sysrq handler, error %d\n", 819 error); 820 goto err_free; 821 } 822 823 error = input_open_device(&sysrq->handle); 824 if (error) { 825 pr_err("Failed to open input device, error %d\n", error); 826 goto err_unregister; 827 } 828 829 return 0; 830 831 err_unregister: 832 input_unregister_handle(&sysrq->handle); 833 err_free: 834 kfree(sysrq); 835 return error; 836 } 837 838 static void sysrq_disconnect(struct input_handle *handle) 839 { 840 struct sysrq_state *sysrq = handle->private; 841 842 input_close_device(handle); 843 cancel_work_sync(&sysrq->reinject_work); 844 input_unregister_handle(handle); 845 kfree(sysrq); 846 } 847 848 /* 849 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 850 * keyboards have SysRq key predefined and so user may add it to keymap 851 * later, but we expect all such keyboards to have left alt. 852 */ 853 static const struct input_device_id sysrq_ids[] = { 854 { 855 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 856 INPUT_DEVICE_ID_MATCH_KEYBIT, 857 .evbit = { BIT_MASK(EV_KEY) }, 858 .keybit = { BIT_MASK(KEY_LEFTALT) }, 859 }, 860 { }, 861 }; 862 863 static struct input_handler sysrq_handler = { 864 .filter = sysrq_filter, 865 .connect = sysrq_connect, 866 .disconnect = sysrq_disconnect, 867 .name = "sysrq", 868 .id_table = sysrq_ids, 869 }; 870 871 static bool sysrq_handler_registered; 872 873 unsigned short platform_sysrq_reset_seq[] __weak = { KEY_RESERVED }; 874 875 static inline void sysrq_register_handler(void) 876 { 877 unsigned short key; 878 int error; 879 int i; 880 881 for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) { 882 key = platform_sysrq_reset_seq[i]; 883 if (key == KEY_RESERVED || key > KEY_MAX) 884 break; 885 886 sysrq_reset_seq[sysrq_reset_seq_len++] = key; 887 } 888 889 error = input_register_handler(&sysrq_handler); 890 if (error) 891 pr_err("Failed to register input handler, error %d", error); 892 else 893 sysrq_handler_registered = true; 894 } 895 896 static inline void sysrq_unregister_handler(void) 897 { 898 if (sysrq_handler_registered) { 899 input_unregister_handler(&sysrq_handler); 900 sysrq_handler_registered = false; 901 } 902 } 903 904 static int sysrq_reset_seq_param_set(const char *buffer, 905 const struct kernel_param *kp) 906 { 907 unsigned long val; 908 int error; 909 910 error = strict_strtoul(buffer, 0, &val); 911 if (error < 0) 912 return error; 913 914 if (val > KEY_MAX) 915 return -EINVAL; 916 917 *((unsigned short *)kp->arg) = val; 918 sysrq_reset_seq_version++; 919 920 return 0; 921 } 922 923 static struct kernel_param_ops param_ops_sysrq_reset_seq = { 924 .get = param_get_ushort, 925 .set = sysrq_reset_seq_param_set, 926 }; 927 928 #define param_check_sysrq_reset_seq(name, p) \ 929 __param_check(name, p, unsigned short) 930 931 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 932 &sysrq_reset_seq_len, 0644); 933 934 #else 935 936 static inline void sysrq_register_handler(void) 937 { 938 } 939 940 static inline void sysrq_unregister_handler(void) 941 { 942 } 943 944 #endif /* CONFIG_INPUT */ 945 946 int sysrq_toggle_support(int enable_mask) 947 { 948 bool was_enabled = sysrq_on(); 949 950 sysrq_enabled = enable_mask; 951 952 if (was_enabled != sysrq_on()) { 953 if (sysrq_on()) 954 sysrq_register_handler(); 955 else 956 sysrq_unregister_handler(); 957 } 958 959 return 0; 960 } 961 962 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 963 struct sysrq_key_op *remove_op_p) 964 { 965 int retval; 966 unsigned long flags; 967 968 spin_lock_irqsave(&sysrq_key_table_lock, flags); 969 if (__sysrq_get_key_op(key) == remove_op_p) { 970 __sysrq_put_key_op(key, insert_op_p); 971 retval = 0; 972 } else { 973 retval = -1; 974 } 975 spin_unlock_irqrestore(&sysrq_key_table_lock, flags); 976 return retval; 977 } 978 979 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 980 { 981 return __sysrq_swap_key_ops(key, op_p, NULL); 982 } 983 EXPORT_SYMBOL(register_sysrq_key); 984 985 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 986 { 987 return __sysrq_swap_key_ops(key, NULL, op_p); 988 } 989 EXPORT_SYMBOL(unregister_sysrq_key); 990 991 #ifdef CONFIG_PROC_FS 992 /* 993 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 994 */ 995 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 996 size_t count, loff_t *ppos) 997 { 998 if (count) { 999 char c; 1000 1001 if (get_user(c, buf)) 1002 return -EFAULT; 1003 __handle_sysrq(c, false); 1004 } 1005 1006 return count; 1007 } 1008 1009 static const struct file_operations proc_sysrq_trigger_operations = { 1010 .write = write_sysrq_trigger, 1011 .llseek = noop_llseek, 1012 }; 1013 1014 static void sysrq_init_procfs(void) 1015 { 1016 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1017 &proc_sysrq_trigger_operations)) 1018 pr_err("Failed to register proc interface\n"); 1019 } 1020 1021 #else 1022 1023 static inline void sysrq_init_procfs(void) 1024 { 1025 } 1026 1027 #endif /* CONFIG_PROC_FS */ 1028 1029 static int __init sysrq_init(void) 1030 { 1031 sysrq_init_procfs(); 1032 1033 if (sysrq_on()) 1034 sysrq_register_handler(); 1035 1036 return 0; 1037 } 1038 module_init(sysrq_init); 1039