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 #include <linux/of.h> 49 #include <linux/rcupdate.h> 50 51 #include <asm/ptrace.h> 52 #include <asm/irq_regs.h> 53 54 /* Whether we react on sysrq keys or just ignore them */ 55 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; 56 static bool __read_mostly sysrq_always_enabled; 57 58 static bool sysrq_on(void) 59 { 60 return sysrq_enabled || sysrq_always_enabled; 61 } 62 63 /* 64 * A value of 1 means 'all', other nonzero values are an op mask: 65 */ 66 static bool sysrq_on_mask(int mask) 67 { 68 return sysrq_always_enabled || 69 sysrq_enabled == 1 || 70 (sysrq_enabled & mask); 71 } 72 73 static int __init sysrq_always_enabled_setup(char *str) 74 { 75 sysrq_always_enabled = true; 76 pr_info("sysrq always enabled.\n"); 77 78 return 1; 79 } 80 81 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 82 83 84 static void sysrq_handle_loglevel(int key) 85 { 86 int i; 87 88 i = key - '0'; 89 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 90 pr_info("Loglevel set to %d\n", i); 91 console_loglevel = i; 92 } 93 static struct sysrq_key_op sysrq_loglevel_op = { 94 .handler = sysrq_handle_loglevel, 95 .help_msg = "loglevel(0-9)", 96 .action_msg = "Changing Loglevel", 97 .enable_mask = SYSRQ_ENABLE_LOG, 98 }; 99 100 #ifdef CONFIG_VT 101 static void sysrq_handle_SAK(int key) 102 { 103 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 104 schedule_work(SAK_work); 105 } 106 static struct sysrq_key_op sysrq_SAK_op = { 107 .handler = sysrq_handle_SAK, 108 .help_msg = "sak(k)", 109 .action_msg = "SAK", 110 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 111 }; 112 #else 113 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL) 114 #endif 115 116 #ifdef CONFIG_VT 117 static void sysrq_handle_unraw(int key) 118 { 119 vt_reset_unicode(fg_console); 120 } 121 122 static struct sysrq_key_op sysrq_unraw_op = { 123 .handler = sysrq_handle_unraw, 124 .help_msg = "unraw(r)", 125 .action_msg = "Keyboard mode set to system default", 126 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 127 }; 128 #else 129 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL) 130 #endif /* CONFIG_VT */ 131 132 static void sysrq_handle_crash(int key) 133 { 134 char *killer = NULL; 135 136 panic_on_oops = 1; /* force panic */ 137 wmb(); 138 *killer = 1; 139 } 140 static struct sysrq_key_op sysrq_crash_op = { 141 .handler = sysrq_handle_crash, 142 .help_msg = "crash(c)", 143 .action_msg = "Trigger a crash", 144 .enable_mask = SYSRQ_ENABLE_DUMP, 145 }; 146 147 static void sysrq_handle_reboot(int key) 148 { 149 lockdep_off(); 150 local_irq_enable(); 151 emergency_restart(); 152 } 153 static struct sysrq_key_op sysrq_reboot_op = { 154 .handler = sysrq_handle_reboot, 155 .help_msg = "reboot(b)", 156 .action_msg = "Resetting", 157 .enable_mask = SYSRQ_ENABLE_BOOT, 158 }; 159 160 static void sysrq_handle_sync(int key) 161 { 162 emergency_sync(); 163 } 164 static struct sysrq_key_op sysrq_sync_op = { 165 .handler = sysrq_handle_sync, 166 .help_msg = "sync(s)", 167 .action_msg = "Emergency Sync", 168 .enable_mask = SYSRQ_ENABLE_SYNC, 169 }; 170 171 static void sysrq_handle_show_timers(int key) 172 { 173 sysrq_timer_list_show(); 174 } 175 176 static struct sysrq_key_op sysrq_show_timers_op = { 177 .handler = sysrq_handle_show_timers, 178 .help_msg = "show-all-timers(q)", 179 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 180 }; 181 182 static void sysrq_handle_mountro(int key) 183 { 184 emergency_remount(); 185 } 186 static struct sysrq_key_op sysrq_mountro_op = { 187 .handler = sysrq_handle_mountro, 188 .help_msg = "unmount(u)", 189 .action_msg = "Emergency Remount R/O", 190 .enable_mask = SYSRQ_ENABLE_REMOUNT, 191 }; 192 193 #ifdef CONFIG_LOCKDEP 194 static void sysrq_handle_showlocks(int key) 195 { 196 debug_show_all_locks(); 197 } 198 199 static struct sysrq_key_op sysrq_showlocks_op = { 200 .handler = sysrq_handle_showlocks, 201 .help_msg = "show-all-locks(d)", 202 .action_msg = "Show Locks Held", 203 }; 204 #else 205 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 206 #endif 207 208 #ifdef CONFIG_SMP 209 static DEFINE_SPINLOCK(show_lock); 210 211 static void showacpu(void *dummy) 212 { 213 unsigned long flags; 214 215 /* Idle CPUs have no interesting backtrace. */ 216 if (idle_cpu(smp_processor_id())) 217 return; 218 219 spin_lock_irqsave(&show_lock, flags); 220 pr_info("CPU%d:\n", smp_processor_id()); 221 show_stack(NULL, NULL); 222 spin_unlock_irqrestore(&show_lock, flags); 223 } 224 225 static void sysrq_showregs_othercpus(struct work_struct *dummy) 226 { 227 smp_call_function(showacpu, NULL, 0); 228 } 229 230 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 231 232 static void sysrq_handle_showallcpus(int key) 233 { 234 /* 235 * Fall back to the workqueue based printing if the 236 * backtrace printing did not succeed or the 237 * architecture has no support for it: 238 */ 239 if (!trigger_all_cpu_backtrace()) { 240 struct pt_regs *regs = get_irq_regs(); 241 242 if (regs) { 243 pr_info("CPU%d:\n", smp_processor_id()); 244 show_regs(regs); 245 } 246 schedule_work(&sysrq_showallcpus); 247 } 248 } 249 250 static struct sysrq_key_op sysrq_showallcpus_op = { 251 .handler = sysrq_handle_showallcpus, 252 .help_msg = "show-backtrace-all-active-cpus(l)", 253 .action_msg = "Show backtrace of all active CPUs", 254 .enable_mask = SYSRQ_ENABLE_DUMP, 255 }; 256 #endif 257 258 static void sysrq_handle_showregs(int key) 259 { 260 struct pt_regs *regs = get_irq_regs(); 261 if (regs) 262 show_regs(regs); 263 perf_event_print_debug(); 264 } 265 static struct sysrq_key_op sysrq_showregs_op = { 266 .handler = sysrq_handle_showregs, 267 .help_msg = "show-registers(p)", 268 .action_msg = "Show Regs", 269 .enable_mask = SYSRQ_ENABLE_DUMP, 270 }; 271 272 static void sysrq_handle_showstate(int key) 273 { 274 show_state(); 275 show_workqueue_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 = CONSOLE_LOGLEVEL_DEBUG; 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 const gfp_t gfp_mask = GFP_KERNEL; 357 struct oom_control oc = { 358 .zonelist = node_zonelist(first_memory_node, gfp_mask), 359 .nodemask = NULL, 360 .gfp_mask = gfp_mask, 361 .order = -1, 362 }; 363 364 mutex_lock(&oom_lock); 365 if (!out_of_memory(&oc)) 366 pr_info("OOM request ignored because killer is disabled\n"); 367 mutex_unlock(&oom_lock); 368 } 369 370 static DECLARE_WORK(moom_work, moom_callback); 371 372 static void sysrq_handle_moom(int key) 373 { 374 schedule_work(&moom_work); 375 } 376 static struct sysrq_key_op sysrq_moom_op = { 377 .handler = sysrq_handle_moom, 378 .help_msg = "memory-full-oom-kill(f)", 379 .action_msg = "Manual OOM execution", 380 .enable_mask = SYSRQ_ENABLE_SIGNAL, 381 }; 382 383 #ifdef CONFIG_BLOCK 384 static void sysrq_handle_thaw(int key) 385 { 386 emergency_thaw_all(); 387 } 388 static struct sysrq_key_op sysrq_thaw_op = { 389 .handler = sysrq_handle_thaw, 390 .help_msg = "thaw-filesystems(j)", 391 .action_msg = "Emergency Thaw of all frozen filesystems", 392 .enable_mask = SYSRQ_ENABLE_SIGNAL, 393 }; 394 #endif 395 396 static void sysrq_handle_kill(int key) 397 { 398 send_sig_all(SIGKILL); 399 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 400 } 401 static struct sysrq_key_op sysrq_kill_op = { 402 .handler = sysrq_handle_kill, 403 .help_msg = "kill-all-tasks(i)", 404 .action_msg = "Kill All Tasks", 405 .enable_mask = SYSRQ_ENABLE_SIGNAL, 406 }; 407 408 static void sysrq_handle_unrt(int key) 409 { 410 normalize_rt_tasks(); 411 } 412 static struct sysrq_key_op sysrq_unrt_op = { 413 .handler = sysrq_handle_unrt, 414 .help_msg = "nice-all-RT-tasks(n)", 415 .action_msg = "Nice All RT Tasks", 416 .enable_mask = SYSRQ_ENABLE_RTNICE, 417 }; 418 419 /* Key Operations table and lock */ 420 static DEFINE_SPINLOCK(sysrq_key_table_lock); 421 422 static struct sysrq_key_op *sysrq_key_table[36] = { 423 &sysrq_loglevel_op, /* 0 */ 424 &sysrq_loglevel_op, /* 1 */ 425 &sysrq_loglevel_op, /* 2 */ 426 &sysrq_loglevel_op, /* 3 */ 427 &sysrq_loglevel_op, /* 4 */ 428 &sysrq_loglevel_op, /* 5 */ 429 &sysrq_loglevel_op, /* 6 */ 430 &sysrq_loglevel_op, /* 7 */ 431 &sysrq_loglevel_op, /* 8 */ 432 &sysrq_loglevel_op, /* 9 */ 433 434 /* 435 * a: Don't use for system provided sysrqs, it is handled specially on 436 * sparc and will never arrive. 437 */ 438 NULL, /* a */ 439 &sysrq_reboot_op, /* b */ 440 &sysrq_crash_op, /* c & ibm_emac driver debug */ 441 &sysrq_showlocks_op, /* d */ 442 &sysrq_term_op, /* e */ 443 &sysrq_moom_op, /* f */ 444 /* g: May be registered for the kernel debugger */ 445 NULL, /* g */ 446 NULL, /* h - reserved for help */ 447 &sysrq_kill_op, /* i */ 448 #ifdef CONFIG_BLOCK 449 &sysrq_thaw_op, /* j */ 450 #else 451 NULL, /* j */ 452 #endif 453 &sysrq_SAK_op, /* k */ 454 #ifdef CONFIG_SMP 455 &sysrq_showallcpus_op, /* l */ 456 #else 457 NULL, /* l */ 458 #endif 459 &sysrq_showmem_op, /* m */ 460 &sysrq_unrt_op, /* n */ 461 /* o: This will often be registered as 'Off' at init time */ 462 NULL, /* o */ 463 &sysrq_showregs_op, /* p */ 464 &sysrq_show_timers_op, /* q */ 465 &sysrq_unraw_op, /* r */ 466 &sysrq_sync_op, /* s */ 467 &sysrq_showstate_op, /* t */ 468 &sysrq_mountro_op, /* u */ 469 /* v: May be registered for frame buffer console restore */ 470 NULL, /* v */ 471 &sysrq_showstate_blocked_op, /* w */ 472 /* x: May be registered on mips for TLB dump */ 473 /* x: May be registered on ppc/powerpc for xmon */ 474 /* x: May be registered on sparc64 for global PMU dump */ 475 NULL, /* x */ 476 /* y: May be registered on sparc64 for global register dump */ 477 NULL, /* y */ 478 &sysrq_ftrace_dump_op, /* z */ 479 }; 480 481 /* key2index calculation, -1 on invalid index */ 482 static int sysrq_key_table_key2index(int key) 483 { 484 int retval; 485 486 if ((key >= '0') && (key <= '9')) 487 retval = key - '0'; 488 else if ((key >= 'a') && (key <= 'z')) 489 retval = key + 10 - 'a'; 490 else 491 retval = -1; 492 return retval; 493 } 494 495 /* 496 * get and put functions for the table, exposed to modules. 497 */ 498 struct sysrq_key_op *__sysrq_get_key_op(int key) 499 { 500 struct sysrq_key_op *op_p = NULL; 501 int i; 502 503 i = sysrq_key_table_key2index(key); 504 if (i != -1) 505 op_p = sysrq_key_table[i]; 506 507 return op_p; 508 } 509 510 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 511 { 512 int i = sysrq_key_table_key2index(key); 513 514 if (i != -1) 515 sysrq_key_table[i] = op_p; 516 } 517 518 void __handle_sysrq(int key, bool check_mask) 519 { 520 struct sysrq_key_op *op_p; 521 int orig_log_level; 522 int i; 523 524 rcu_sysrq_start(); 525 rcu_read_lock(); 526 /* 527 * Raise the apparent loglevel to maximum so that the sysrq header 528 * is shown to provide the user with positive feedback. We do not 529 * simply emit this at KERN_EMERG as that would change message 530 * routing in the consumers of /proc/kmsg. 531 */ 532 orig_log_level = console_loglevel; 533 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 534 pr_info("SysRq : "); 535 536 op_p = __sysrq_get_key_op(key); 537 if (op_p) { 538 /* 539 * Should we check for enabled operations (/proc/sysrq-trigger 540 * should not) and is the invoked operation enabled? 541 */ 542 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 543 pr_cont("%s\n", op_p->action_msg); 544 console_loglevel = orig_log_level; 545 op_p->handler(key); 546 } else { 547 pr_cont("This sysrq operation is disabled.\n"); 548 } 549 } else { 550 pr_cont("HELP : "); 551 /* Only print the help msg once per handler */ 552 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 553 if (sysrq_key_table[i]) { 554 int j; 555 556 for (j = 0; sysrq_key_table[i] != 557 sysrq_key_table[j]; j++) 558 ; 559 if (j != i) 560 continue; 561 pr_cont("%s ", sysrq_key_table[i]->help_msg); 562 } 563 } 564 pr_cont("\n"); 565 console_loglevel = orig_log_level; 566 } 567 rcu_read_unlock(); 568 rcu_sysrq_end(); 569 } 570 571 void handle_sysrq(int key) 572 { 573 if (sysrq_on()) 574 __handle_sysrq(key, true); 575 } 576 EXPORT_SYMBOL(handle_sysrq); 577 578 #ifdef CONFIG_INPUT 579 static int sysrq_reset_downtime_ms; 580 581 /* Simple translation table for the SysRq keys */ 582 static const unsigned char sysrq_xlate[KEY_CNT] = 583 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 584 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 585 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 586 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 587 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 588 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 589 "\r\000/"; /* 0x60 - 0x6f */ 590 591 struct sysrq_state { 592 struct input_handle handle; 593 struct work_struct reinject_work; 594 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 595 unsigned int alt; 596 unsigned int alt_use; 597 bool active; 598 bool need_reinject; 599 bool reinjecting; 600 601 /* reset sequence handling */ 602 bool reset_canceled; 603 bool reset_requested; 604 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 605 int reset_seq_len; 606 int reset_seq_cnt; 607 int reset_seq_version; 608 struct timer_list keyreset_timer; 609 }; 610 611 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 612 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 613 static unsigned int sysrq_reset_seq_len; 614 static unsigned int sysrq_reset_seq_version = 1; 615 616 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 617 { 618 int i; 619 unsigned short key; 620 621 state->reset_seq_cnt = 0; 622 623 for (i = 0; i < sysrq_reset_seq_len; i++) { 624 key = sysrq_reset_seq[i]; 625 626 if (key == KEY_RESERVED || key > KEY_MAX) 627 break; 628 629 __set_bit(key, state->reset_keybit); 630 state->reset_seq_len++; 631 632 if (test_bit(key, state->key_down)) 633 state->reset_seq_cnt++; 634 } 635 636 /* Disable reset until old keys are not released */ 637 state->reset_canceled = state->reset_seq_cnt != 0; 638 639 state->reset_seq_version = sysrq_reset_seq_version; 640 } 641 642 static void sysrq_do_reset(unsigned long _state) 643 { 644 struct sysrq_state *state = (struct sysrq_state *) _state; 645 646 state->reset_requested = true; 647 648 sys_sync(); 649 kernel_restart(NULL); 650 } 651 652 static void sysrq_handle_reset_request(struct sysrq_state *state) 653 { 654 if (state->reset_requested) 655 __handle_sysrq(sysrq_xlate[KEY_B], false); 656 657 if (sysrq_reset_downtime_ms) 658 mod_timer(&state->keyreset_timer, 659 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 660 else 661 sysrq_do_reset((unsigned long)state); 662 } 663 664 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 665 unsigned int code, int value) 666 { 667 if (!test_bit(code, state->reset_keybit)) { 668 /* 669 * Pressing any key _not_ in reset sequence cancels 670 * the reset sequence. Also cancelling the timer in 671 * case additional keys were pressed after a reset 672 * has been requested. 673 */ 674 if (value && state->reset_seq_cnt) { 675 state->reset_canceled = true; 676 del_timer(&state->keyreset_timer); 677 } 678 } else if (value == 0) { 679 /* 680 * Key release - all keys in the reset sequence need 681 * to be pressed and held for the reset timeout 682 * to hold. 683 */ 684 del_timer(&state->keyreset_timer); 685 686 if (--state->reset_seq_cnt == 0) 687 state->reset_canceled = false; 688 } else if (value == 1) { 689 /* key press, not autorepeat */ 690 if (++state->reset_seq_cnt == state->reset_seq_len && 691 !state->reset_canceled) { 692 sysrq_handle_reset_request(state); 693 } 694 } 695 } 696 697 #ifdef CONFIG_OF 698 static void sysrq_of_get_keyreset_config(void) 699 { 700 u32 key; 701 struct device_node *np; 702 struct property *prop; 703 const __be32 *p; 704 705 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 706 if (!np) { 707 pr_debug("No sysrq node found"); 708 return; 709 } 710 711 /* Reset in case a __weak definition was present */ 712 sysrq_reset_seq_len = 0; 713 714 of_property_for_each_u32(np, "keyset", prop, p, key) { 715 if (key == KEY_RESERVED || key > KEY_MAX || 716 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 717 break; 718 719 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 720 } 721 722 /* Get reset timeout if any. */ 723 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 724 } 725 #else 726 static void sysrq_of_get_keyreset_config(void) 727 { 728 } 729 #endif 730 731 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 732 { 733 struct sysrq_state *sysrq = 734 container_of(work, struct sysrq_state, reinject_work); 735 struct input_handle *handle = &sysrq->handle; 736 unsigned int alt_code = sysrq->alt_use; 737 738 if (sysrq->need_reinject) { 739 /* we do not want the assignment to be reordered */ 740 sysrq->reinjecting = true; 741 mb(); 742 743 /* Simulate press and release of Alt + SysRq */ 744 input_inject_event(handle, EV_KEY, alt_code, 1); 745 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 746 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 747 748 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 749 input_inject_event(handle, EV_KEY, alt_code, 0); 750 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 751 752 mb(); 753 sysrq->reinjecting = false; 754 } 755 } 756 757 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 758 unsigned int code, int value) 759 { 760 bool was_active = sysrq->active; 761 bool suppress; 762 763 switch (code) { 764 765 case KEY_LEFTALT: 766 case KEY_RIGHTALT: 767 if (!value) { 768 /* One of ALTs is being released */ 769 if (sysrq->active && code == sysrq->alt_use) 770 sysrq->active = false; 771 772 sysrq->alt = KEY_RESERVED; 773 774 } else if (value != 2) { 775 sysrq->alt = code; 776 sysrq->need_reinject = false; 777 } 778 break; 779 780 case KEY_SYSRQ: 781 if (value == 1 && sysrq->alt != KEY_RESERVED) { 782 sysrq->active = true; 783 sysrq->alt_use = sysrq->alt; 784 /* 785 * If nothing else will be pressed we'll need 786 * to re-inject Alt-SysRq keysroke. 787 */ 788 sysrq->need_reinject = true; 789 } 790 791 /* 792 * Pretend that sysrq was never pressed at all. This 793 * is needed to properly handle KGDB which will try 794 * to release all keys after exiting debugger. If we 795 * do not clear key bit it KGDB will end up sending 796 * release events for Alt and SysRq, potentially 797 * triggering print screen function. 798 */ 799 if (sysrq->active) 800 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 801 802 break; 803 804 default: 805 if (sysrq->active && value && value != 2) { 806 sysrq->need_reinject = false; 807 __handle_sysrq(sysrq_xlate[code], true); 808 } 809 break; 810 } 811 812 suppress = sysrq->active; 813 814 if (!sysrq->active) { 815 816 /* 817 * See if reset sequence has changed since the last time. 818 */ 819 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 820 sysrq_parse_reset_sequence(sysrq); 821 822 /* 823 * If we are not suppressing key presses keep track of 824 * keyboard state so we can release keys that have been 825 * pressed before entering SysRq mode. 826 */ 827 if (value) 828 set_bit(code, sysrq->key_down); 829 else 830 clear_bit(code, sysrq->key_down); 831 832 if (was_active) 833 schedule_work(&sysrq->reinject_work); 834 835 /* Check for reset sequence */ 836 sysrq_detect_reset_sequence(sysrq, code, value); 837 838 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 839 /* 840 * Pass on release events for keys that was pressed before 841 * entering SysRq mode. 842 */ 843 suppress = false; 844 } 845 846 return suppress; 847 } 848 849 static bool sysrq_filter(struct input_handle *handle, 850 unsigned int type, unsigned int code, int value) 851 { 852 struct sysrq_state *sysrq = handle->private; 853 bool suppress; 854 855 /* 856 * Do not filter anything if we are in the process of re-injecting 857 * Alt+SysRq combination. 858 */ 859 if (sysrq->reinjecting) 860 return false; 861 862 switch (type) { 863 864 case EV_SYN: 865 suppress = false; 866 break; 867 868 case EV_KEY: 869 suppress = sysrq_handle_keypress(sysrq, code, value); 870 break; 871 872 default: 873 suppress = sysrq->active; 874 break; 875 } 876 877 return suppress; 878 } 879 880 static int sysrq_connect(struct input_handler *handler, 881 struct input_dev *dev, 882 const struct input_device_id *id) 883 { 884 struct sysrq_state *sysrq; 885 int error; 886 887 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 888 if (!sysrq) 889 return -ENOMEM; 890 891 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 892 893 sysrq->handle.dev = dev; 894 sysrq->handle.handler = handler; 895 sysrq->handle.name = "sysrq"; 896 sysrq->handle.private = sysrq; 897 setup_timer(&sysrq->keyreset_timer, 898 sysrq_do_reset, (unsigned long)sysrq); 899 900 error = input_register_handle(&sysrq->handle); 901 if (error) { 902 pr_err("Failed to register input sysrq handler, error %d\n", 903 error); 904 goto err_free; 905 } 906 907 error = input_open_device(&sysrq->handle); 908 if (error) { 909 pr_err("Failed to open input device, error %d\n", error); 910 goto err_unregister; 911 } 912 913 return 0; 914 915 err_unregister: 916 input_unregister_handle(&sysrq->handle); 917 err_free: 918 kfree(sysrq); 919 return error; 920 } 921 922 static void sysrq_disconnect(struct input_handle *handle) 923 { 924 struct sysrq_state *sysrq = handle->private; 925 926 input_close_device(handle); 927 cancel_work_sync(&sysrq->reinject_work); 928 del_timer_sync(&sysrq->keyreset_timer); 929 input_unregister_handle(handle); 930 kfree(sysrq); 931 } 932 933 /* 934 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 935 * keyboards have SysRq key predefined and so user may add it to keymap 936 * later, but we expect all such keyboards to have left alt. 937 */ 938 static const struct input_device_id sysrq_ids[] = { 939 { 940 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 941 INPUT_DEVICE_ID_MATCH_KEYBIT, 942 .evbit = { BIT_MASK(EV_KEY) }, 943 .keybit = { BIT_MASK(KEY_LEFTALT) }, 944 }, 945 { }, 946 }; 947 948 static struct input_handler sysrq_handler = { 949 .filter = sysrq_filter, 950 .connect = sysrq_connect, 951 .disconnect = sysrq_disconnect, 952 .name = "sysrq", 953 .id_table = sysrq_ids, 954 }; 955 956 static bool sysrq_handler_registered; 957 958 static inline void sysrq_register_handler(void) 959 { 960 int error; 961 962 sysrq_of_get_keyreset_config(); 963 964 error = input_register_handler(&sysrq_handler); 965 if (error) 966 pr_err("Failed to register input handler, error %d", error); 967 else 968 sysrq_handler_registered = true; 969 } 970 971 static inline void sysrq_unregister_handler(void) 972 { 973 if (sysrq_handler_registered) { 974 input_unregister_handler(&sysrq_handler); 975 sysrq_handler_registered = false; 976 } 977 } 978 979 static int sysrq_reset_seq_param_set(const char *buffer, 980 const struct kernel_param *kp) 981 { 982 unsigned long val; 983 int error; 984 985 error = kstrtoul(buffer, 0, &val); 986 if (error < 0) 987 return error; 988 989 if (val > KEY_MAX) 990 return -EINVAL; 991 992 *((unsigned short *)kp->arg) = val; 993 sysrq_reset_seq_version++; 994 995 return 0; 996 } 997 998 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 999 .get = param_get_ushort, 1000 .set = sysrq_reset_seq_param_set, 1001 }; 1002 1003 #define param_check_sysrq_reset_seq(name, p) \ 1004 __param_check(name, p, unsigned short) 1005 1006 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1007 &sysrq_reset_seq_len, 0644); 1008 1009 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1010 1011 #else 1012 1013 static inline void sysrq_register_handler(void) 1014 { 1015 } 1016 1017 static inline void sysrq_unregister_handler(void) 1018 { 1019 } 1020 1021 #endif /* CONFIG_INPUT */ 1022 1023 int sysrq_toggle_support(int enable_mask) 1024 { 1025 bool was_enabled = sysrq_on(); 1026 1027 sysrq_enabled = enable_mask; 1028 1029 if (was_enabled != sysrq_on()) { 1030 if (sysrq_on()) 1031 sysrq_register_handler(); 1032 else 1033 sysrq_unregister_handler(); 1034 } 1035 1036 return 0; 1037 } 1038 1039 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1040 struct sysrq_key_op *remove_op_p) 1041 { 1042 int retval; 1043 1044 spin_lock(&sysrq_key_table_lock); 1045 if (__sysrq_get_key_op(key) == remove_op_p) { 1046 __sysrq_put_key_op(key, insert_op_p); 1047 retval = 0; 1048 } else { 1049 retval = -1; 1050 } 1051 spin_unlock(&sysrq_key_table_lock); 1052 1053 /* 1054 * A concurrent __handle_sysrq either got the old op or the new op. 1055 * Wait for it to go away before returning, so the code for an old 1056 * op is not freed (eg. on module unload) while it is in use. 1057 */ 1058 synchronize_rcu(); 1059 1060 return retval; 1061 } 1062 1063 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1064 { 1065 return __sysrq_swap_key_ops(key, op_p, NULL); 1066 } 1067 EXPORT_SYMBOL(register_sysrq_key); 1068 1069 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1070 { 1071 return __sysrq_swap_key_ops(key, NULL, op_p); 1072 } 1073 EXPORT_SYMBOL(unregister_sysrq_key); 1074 1075 #ifdef CONFIG_PROC_FS 1076 /* 1077 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1078 */ 1079 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1080 size_t count, loff_t *ppos) 1081 { 1082 if (count) { 1083 char c; 1084 1085 if (get_user(c, buf)) 1086 return -EFAULT; 1087 __handle_sysrq(c, false); 1088 } 1089 1090 return count; 1091 } 1092 1093 static const struct file_operations proc_sysrq_trigger_operations = { 1094 .write = write_sysrq_trigger, 1095 .llseek = noop_llseek, 1096 }; 1097 1098 static void sysrq_init_procfs(void) 1099 { 1100 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1101 &proc_sysrq_trigger_operations)) 1102 pr_err("Failed to register proc interface\n"); 1103 } 1104 1105 #else 1106 1107 static inline void sysrq_init_procfs(void) 1108 { 1109 } 1110 1111 #endif /* CONFIG_PROC_FS */ 1112 1113 static int __init sysrq_init(void) 1114 { 1115 sysrq_init_procfs(); 1116 1117 if (sysrq_on()) 1118 sysrq_register_handler(); 1119 1120 return 0; 1121 } 1122 module_init(sysrq_init); 1123