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