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 mutex_lock(&oom_lock); 357 if (!out_of_memory(node_zonelist(first_memory_node, GFP_KERNEL), 358 GFP_KERNEL, 0, NULL, true)) 359 pr_info("OOM request ignored because killer is disabled\n"); 360 mutex_unlock(&oom_lock); 361 } 362 363 static DECLARE_WORK(moom_work, moom_callback); 364 365 static void sysrq_handle_moom(int key) 366 { 367 schedule_work(&moom_work); 368 } 369 static struct sysrq_key_op sysrq_moom_op = { 370 .handler = sysrq_handle_moom, 371 .help_msg = "memory-full-oom-kill(f)", 372 .action_msg = "Manual OOM execution", 373 .enable_mask = SYSRQ_ENABLE_SIGNAL, 374 }; 375 376 #ifdef CONFIG_BLOCK 377 static void sysrq_handle_thaw(int key) 378 { 379 emergency_thaw_all(); 380 } 381 static struct sysrq_key_op sysrq_thaw_op = { 382 .handler = sysrq_handle_thaw, 383 .help_msg = "thaw-filesystems(j)", 384 .action_msg = "Emergency Thaw of all frozen filesystems", 385 .enable_mask = SYSRQ_ENABLE_SIGNAL, 386 }; 387 #endif 388 389 static void sysrq_handle_kill(int key) 390 { 391 send_sig_all(SIGKILL); 392 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 393 } 394 static struct sysrq_key_op sysrq_kill_op = { 395 .handler = sysrq_handle_kill, 396 .help_msg = "kill-all-tasks(i)", 397 .action_msg = "Kill All Tasks", 398 .enable_mask = SYSRQ_ENABLE_SIGNAL, 399 }; 400 401 static void sysrq_handle_unrt(int key) 402 { 403 normalize_rt_tasks(); 404 } 405 static struct sysrq_key_op sysrq_unrt_op = { 406 .handler = sysrq_handle_unrt, 407 .help_msg = "nice-all-RT-tasks(n)", 408 .action_msg = "Nice All RT Tasks", 409 .enable_mask = SYSRQ_ENABLE_RTNICE, 410 }; 411 412 /* Key Operations table and lock */ 413 static DEFINE_SPINLOCK(sysrq_key_table_lock); 414 415 static struct sysrq_key_op *sysrq_key_table[36] = { 416 &sysrq_loglevel_op, /* 0 */ 417 &sysrq_loglevel_op, /* 1 */ 418 &sysrq_loglevel_op, /* 2 */ 419 &sysrq_loglevel_op, /* 3 */ 420 &sysrq_loglevel_op, /* 4 */ 421 &sysrq_loglevel_op, /* 5 */ 422 &sysrq_loglevel_op, /* 6 */ 423 &sysrq_loglevel_op, /* 7 */ 424 &sysrq_loglevel_op, /* 8 */ 425 &sysrq_loglevel_op, /* 9 */ 426 427 /* 428 * a: Don't use for system provided sysrqs, it is handled specially on 429 * sparc and will never arrive. 430 */ 431 NULL, /* a */ 432 &sysrq_reboot_op, /* b */ 433 &sysrq_crash_op, /* c & ibm_emac driver debug */ 434 &sysrq_showlocks_op, /* d */ 435 &sysrq_term_op, /* e */ 436 &sysrq_moom_op, /* f */ 437 /* g: May be registered for the kernel debugger */ 438 NULL, /* g */ 439 NULL, /* h - reserved for help */ 440 &sysrq_kill_op, /* i */ 441 #ifdef CONFIG_BLOCK 442 &sysrq_thaw_op, /* j */ 443 #else 444 NULL, /* j */ 445 #endif 446 &sysrq_SAK_op, /* k */ 447 #ifdef CONFIG_SMP 448 &sysrq_showallcpus_op, /* l */ 449 #else 450 NULL, /* l */ 451 #endif 452 &sysrq_showmem_op, /* m */ 453 &sysrq_unrt_op, /* n */ 454 /* o: This will often be registered as 'Off' at init time */ 455 NULL, /* o */ 456 &sysrq_showregs_op, /* p */ 457 &sysrq_show_timers_op, /* q */ 458 &sysrq_unraw_op, /* r */ 459 &sysrq_sync_op, /* s */ 460 &sysrq_showstate_op, /* t */ 461 &sysrq_mountro_op, /* u */ 462 /* v: May be registered for frame buffer console restore */ 463 NULL, /* v */ 464 &sysrq_showstate_blocked_op, /* w */ 465 /* x: May be registered on ppc/powerpc for xmon */ 466 /* x: May be registered on sparc64 for global PMU dump */ 467 NULL, /* x */ 468 /* y: May be registered on sparc64 for global register dump */ 469 NULL, /* y */ 470 &sysrq_ftrace_dump_op, /* z */ 471 }; 472 473 /* key2index calculation, -1 on invalid index */ 474 static int sysrq_key_table_key2index(int key) 475 { 476 int retval; 477 478 if ((key >= '0') && (key <= '9')) 479 retval = key - '0'; 480 else if ((key >= 'a') && (key <= 'z')) 481 retval = key + 10 - 'a'; 482 else 483 retval = -1; 484 return retval; 485 } 486 487 /* 488 * get and put functions for the table, exposed to modules. 489 */ 490 struct sysrq_key_op *__sysrq_get_key_op(int key) 491 { 492 struct sysrq_key_op *op_p = NULL; 493 int i; 494 495 i = sysrq_key_table_key2index(key); 496 if (i != -1) 497 op_p = sysrq_key_table[i]; 498 499 return op_p; 500 } 501 502 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 503 { 504 int i = sysrq_key_table_key2index(key); 505 506 if (i != -1) 507 sysrq_key_table[i] = op_p; 508 } 509 510 void __handle_sysrq(int key, bool check_mask) 511 { 512 struct sysrq_key_op *op_p; 513 int orig_log_level; 514 int i; 515 516 rcu_sysrq_start(); 517 rcu_read_lock(); 518 /* 519 * Raise the apparent loglevel to maximum so that the sysrq header 520 * is shown to provide the user with positive feedback. We do not 521 * simply emit this at KERN_EMERG as that would change message 522 * routing in the consumers of /proc/kmsg. 523 */ 524 orig_log_level = console_loglevel; 525 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 526 pr_info("SysRq : "); 527 528 op_p = __sysrq_get_key_op(key); 529 if (op_p) { 530 /* 531 * Should we check for enabled operations (/proc/sysrq-trigger 532 * should not) and is the invoked operation enabled? 533 */ 534 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 535 pr_cont("%s\n", op_p->action_msg); 536 console_loglevel = orig_log_level; 537 op_p->handler(key); 538 } else { 539 pr_cont("This sysrq operation is disabled.\n"); 540 } 541 } else { 542 pr_cont("HELP : "); 543 /* Only print the help msg once per handler */ 544 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 545 if (sysrq_key_table[i]) { 546 int j; 547 548 for (j = 0; sysrq_key_table[i] != 549 sysrq_key_table[j]; j++) 550 ; 551 if (j != i) 552 continue; 553 pr_cont("%s ", sysrq_key_table[i]->help_msg); 554 } 555 } 556 pr_cont("\n"); 557 console_loglevel = orig_log_level; 558 } 559 rcu_read_unlock(); 560 rcu_sysrq_end(); 561 } 562 563 void handle_sysrq(int key) 564 { 565 if (sysrq_on()) 566 __handle_sysrq(key, true); 567 } 568 EXPORT_SYMBOL(handle_sysrq); 569 570 #ifdef CONFIG_INPUT 571 static int sysrq_reset_downtime_ms; 572 573 /* Simple translation table for the SysRq keys */ 574 static const unsigned char sysrq_xlate[KEY_CNT] = 575 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 576 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 577 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 578 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 579 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 580 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 581 "\r\000/"; /* 0x60 - 0x6f */ 582 583 struct sysrq_state { 584 struct input_handle handle; 585 struct work_struct reinject_work; 586 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 587 unsigned int alt; 588 unsigned int alt_use; 589 bool active; 590 bool need_reinject; 591 bool reinjecting; 592 593 /* reset sequence handling */ 594 bool reset_canceled; 595 bool reset_requested; 596 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 597 int reset_seq_len; 598 int reset_seq_cnt; 599 int reset_seq_version; 600 struct timer_list keyreset_timer; 601 }; 602 603 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 604 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 605 static unsigned int sysrq_reset_seq_len; 606 static unsigned int sysrq_reset_seq_version = 1; 607 608 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 609 { 610 int i; 611 unsigned short key; 612 613 state->reset_seq_cnt = 0; 614 615 for (i = 0; i < sysrq_reset_seq_len; i++) { 616 key = sysrq_reset_seq[i]; 617 618 if (key == KEY_RESERVED || key > KEY_MAX) 619 break; 620 621 __set_bit(key, state->reset_keybit); 622 state->reset_seq_len++; 623 624 if (test_bit(key, state->key_down)) 625 state->reset_seq_cnt++; 626 } 627 628 /* Disable reset until old keys are not released */ 629 state->reset_canceled = state->reset_seq_cnt != 0; 630 631 state->reset_seq_version = sysrq_reset_seq_version; 632 } 633 634 static void sysrq_do_reset(unsigned long _state) 635 { 636 struct sysrq_state *state = (struct sysrq_state *) _state; 637 638 state->reset_requested = true; 639 640 sys_sync(); 641 kernel_restart(NULL); 642 } 643 644 static void sysrq_handle_reset_request(struct sysrq_state *state) 645 { 646 if (state->reset_requested) 647 __handle_sysrq(sysrq_xlate[KEY_B], false); 648 649 if (sysrq_reset_downtime_ms) 650 mod_timer(&state->keyreset_timer, 651 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 652 else 653 sysrq_do_reset((unsigned long)state); 654 } 655 656 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 657 unsigned int code, int value) 658 { 659 if (!test_bit(code, state->reset_keybit)) { 660 /* 661 * Pressing any key _not_ in reset sequence cancels 662 * the reset sequence. Also cancelling the timer in 663 * case additional keys were pressed after a reset 664 * has been requested. 665 */ 666 if (value && state->reset_seq_cnt) { 667 state->reset_canceled = true; 668 del_timer(&state->keyreset_timer); 669 } 670 } else if (value == 0) { 671 /* 672 * Key release - all keys in the reset sequence need 673 * to be pressed and held for the reset timeout 674 * to hold. 675 */ 676 del_timer(&state->keyreset_timer); 677 678 if (--state->reset_seq_cnt == 0) 679 state->reset_canceled = false; 680 } else if (value == 1) { 681 /* key press, not autorepeat */ 682 if (++state->reset_seq_cnt == state->reset_seq_len && 683 !state->reset_canceled) { 684 sysrq_handle_reset_request(state); 685 } 686 } 687 } 688 689 #ifdef CONFIG_OF 690 static void sysrq_of_get_keyreset_config(void) 691 { 692 u32 key; 693 struct device_node *np; 694 struct property *prop; 695 const __be32 *p; 696 697 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 698 if (!np) { 699 pr_debug("No sysrq node found"); 700 return; 701 } 702 703 /* Reset in case a __weak definition was present */ 704 sysrq_reset_seq_len = 0; 705 706 of_property_for_each_u32(np, "keyset", prop, p, key) { 707 if (key == KEY_RESERVED || key > KEY_MAX || 708 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 709 break; 710 711 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 712 } 713 714 /* Get reset timeout if any. */ 715 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 716 } 717 #else 718 static void sysrq_of_get_keyreset_config(void) 719 { 720 } 721 #endif 722 723 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 724 { 725 struct sysrq_state *sysrq = 726 container_of(work, struct sysrq_state, reinject_work); 727 struct input_handle *handle = &sysrq->handle; 728 unsigned int alt_code = sysrq->alt_use; 729 730 if (sysrq->need_reinject) { 731 /* we do not want the assignment to be reordered */ 732 sysrq->reinjecting = true; 733 mb(); 734 735 /* Simulate press and release of Alt + SysRq */ 736 input_inject_event(handle, EV_KEY, alt_code, 1); 737 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 738 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 739 740 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 741 input_inject_event(handle, EV_KEY, alt_code, 0); 742 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 743 744 mb(); 745 sysrq->reinjecting = false; 746 } 747 } 748 749 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 750 unsigned int code, int value) 751 { 752 bool was_active = sysrq->active; 753 bool suppress; 754 755 switch (code) { 756 757 case KEY_LEFTALT: 758 case KEY_RIGHTALT: 759 if (!value) { 760 /* One of ALTs is being released */ 761 if (sysrq->active && code == sysrq->alt_use) 762 sysrq->active = false; 763 764 sysrq->alt = KEY_RESERVED; 765 766 } else if (value != 2) { 767 sysrq->alt = code; 768 sysrq->need_reinject = false; 769 } 770 break; 771 772 case KEY_SYSRQ: 773 if (value == 1 && sysrq->alt != KEY_RESERVED) { 774 sysrq->active = true; 775 sysrq->alt_use = sysrq->alt; 776 /* 777 * If nothing else will be pressed we'll need 778 * to re-inject Alt-SysRq keysroke. 779 */ 780 sysrq->need_reinject = true; 781 } 782 783 /* 784 * Pretend that sysrq was never pressed at all. This 785 * is needed to properly handle KGDB which will try 786 * to release all keys after exiting debugger. If we 787 * do not clear key bit it KGDB will end up sending 788 * release events for Alt and SysRq, potentially 789 * triggering print screen function. 790 */ 791 if (sysrq->active) 792 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 793 794 break; 795 796 default: 797 if (sysrq->active && value && value != 2) { 798 sysrq->need_reinject = false; 799 __handle_sysrq(sysrq_xlate[code], true); 800 } 801 break; 802 } 803 804 suppress = sysrq->active; 805 806 if (!sysrq->active) { 807 808 /* 809 * See if reset sequence has changed since the last time. 810 */ 811 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 812 sysrq_parse_reset_sequence(sysrq); 813 814 /* 815 * If we are not suppressing key presses keep track of 816 * keyboard state so we can release keys that have been 817 * pressed before entering SysRq mode. 818 */ 819 if (value) 820 set_bit(code, sysrq->key_down); 821 else 822 clear_bit(code, sysrq->key_down); 823 824 if (was_active) 825 schedule_work(&sysrq->reinject_work); 826 827 /* Check for reset sequence */ 828 sysrq_detect_reset_sequence(sysrq, code, value); 829 830 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 831 /* 832 * Pass on release events for keys that was pressed before 833 * entering SysRq mode. 834 */ 835 suppress = false; 836 } 837 838 return suppress; 839 } 840 841 static bool sysrq_filter(struct input_handle *handle, 842 unsigned int type, unsigned int code, int value) 843 { 844 struct sysrq_state *sysrq = handle->private; 845 bool suppress; 846 847 /* 848 * Do not filter anything if we are in the process of re-injecting 849 * Alt+SysRq combination. 850 */ 851 if (sysrq->reinjecting) 852 return false; 853 854 switch (type) { 855 856 case EV_SYN: 857 suppress = false; 858 break; 859 860 case EV_KEY: 861 suppress = sysrq_handle_keypress(sysrq, code, value); 862 break; 863 864 default: 865 suppress = sysrq->active; 866 break; 867 } 868 869 return suppress; 870 } 871 872 static int sysrq_connect(struct input_handler *handler, 873 struct input_dev *dev, 874 const struct input_device_id *id) 875 { 876 struct sysrq_state *sysrq; 877 int error; 878 879 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 880 if (!sysrq) 881 return -ENOMEM; 882 883 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 884 885 sysrq->handle.dev = dev; 886 sysrq->handle.handler = handler; 887 sysrq->handle.name = "sysrq"; 888 sysrq->handle.private = sysrq; 889 setup_timer(&sysrq->keyreset_timer, 890 sysrq_do_reset, (unsigned long)sysrq); 891 892 error = input_register_handle(&sysrq->handle); 893 if (error) { 894 pr_err("Failed to register input sysrq handler, error %d\n", 895 error); 896 goto err_free; 897 } 898 899 error = input_open_device(&sysrq->handle); 900 if (error) { 901 pr_err("Failed to open input device, error %d\n", error); 902 goto err_unregister; 903 } 904 905 return 0; 906 907 err_unregister: 908 input_unregister_handle(&sysrq->handle); 909 err_free: 910 kfree(sysrq); 911 return error; 912 } 913 914 static void sysrq_disconnect(struct input_handle *handle) 915 { 916 struct sysrq_state *sysrq = handle->private; 917 918 input_close_device(handle); 919 cancel_work_sync(&sysrq->reinject_work); 920 del_timer_sync(&sysrq->keyreset_timer); 921 input_unregister_handle(handle); 922 kfree(sysrq); 923 } 924 925 /* 926 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 927 * keyboards have SysRq key predefined and so user may add it to keymap 928 * later, but we expect all such keyboards to have left alt. 929 */ 930 static const struct input_device_id sysrq_ids[] = { 931 { 932 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 933 INPUT_DEVICE_ID_MATCH_KEYBIT, 934 .evbit = { BIT_MASK(EV_KEY) }, 935 .keybit = { BIT_MASK(KEY_LEFTALT) }, 936 }, 937 { }, 938 }; 939 940 static struct input_handler sysrq_handler = { 941 .filter = sysrq_filter, 942 .connect = sysrq_connect, 943 .disconnect = sysrq_disconnect, 944 .name = "sysrq", 945 .id_table = sysrq_ids, 946 }; 947 948 static bool sysrq_handler_registered; 949 950 static inline void sysrq_register_handler(void) 951 { 952 int error; 953 954 sysrq_of_get_keyreset_config(); 955 956 error = input_register_handler(&sysrq_handler); 957 if (error) 958 pr_err("Failed to register input handler, error %d", error); 959 else 960 sysrq_handler_registered = true; 961 } 962 963 static inline void sysrq_unregister_handler(void) 964 { 965 if (sysrq_handler_registered) { 966 input_unregister_handler(&sysrq_handler); 967 sysrq_handler_registered = false; 968 } 969 } 970 971 static int sysrq_reset_seq_param_set(const char *buffer, 972 const struct kernel_param *kp) 973 { 974 unsigned long val; 975 int error; 976 977 error = kstrtoul(buffer, 0, &val); 978 if (error < 0) 979 return error; 980 981 if (val > KEY_MAX) 982 return -EINVAL; 983 984 *((unsigned short *)kp->arg) = val; 985 sysrq_reset_seq_version++; 986 987 return 0; 988 } 989 990 static struct kernel_param_ops param_ops_sysrq_reset_seq = { 991 .get = param_get_ushort, 992 .set = sysrq_reset_seq_param_set, 993 }; 994 995 #define param_check_sysrq_reset_seq(name, p) \ 996 __param_check(name, p, unsigned short) 997 998 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 999 &sysrq_reset_seq_len, 0644); 1000 1001 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1002 1003 #else 1004 1005 static inline void sysrq_register_handler(void) 1006 { 1007 } 1008 1009 static inline void sysrq_unregister_handler(void) 1010 { 1011 } 1012 1013 #endif /* CONFIG_INPUT */ 1014 1015 int sysrq_toggle_support(int enable_mask) 1016 { 1017 bool was_enabled = sysrq_on(); 1018 1019 sysrq_enabled = enable_mask; 1020 1021 if (was_enabled != sysrq_on()) { 1022 if (sysrq_on()) 1023 sysrq_register_handler(); 1024 else 1025 sysrq_unregister_handler(); 1026 } 1027 1028 return 0; 1029 } 1030 1031 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1032 struct sysrq_key_op *remove_op_p) 1033 { 1034 int retval; 1035 1036 spin_lock(&sysrq_key_table_lock); 1037 if (__sysrq_get_key_op(key) == remove_op_p) { 1038 __sysrq_put_key_op(key, insert_op_p); 1039 retval = 0; 1040 } else { 1041 retval = -1; 1042 } 1043 spin_unlock(&sysrq_key_table_lock); 1044 1045 /* 1046 * A concurrent __handle_sysrq either got the old op or the new op. 1047 * Wait for it to go away before returning, so the code for an old 1048 * op is not freed (eg. on module unload) while it is in use. 1049 */ 1050 synchronize_rcu(); 1051 1052 return retval; 1053 } 1054 1055 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1056 { 1057 return __sysrq_swap_key_ops(key, op_p, NULL); 1058 } 1059 EXPORT_SYMBOL(register_sysrq_key); 1060 1061 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1062 { 1063 return __sysrq_swap_key_ops(key, NULL, op_p); 1064 } 1065 EXPORT_SYMBOL(unregister_sysrq_key); 1066 1067 #ifdef CONFIG_PROC_FS 1068 /* 1069 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1070 */ 1071 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1072 size_t count, loff_t *ppos) 1073 { 1074 if (count) { 1075 char c; 1076 1077 if (get_user(c, buf)) 1078 return -EFAULT; 1079 __handle_sysrq(c, false); 1080 } 1081 1082 return count; 1083 } 1084 1085 static const struct file_operations proc_sysrq_trigger_operations = { 1086 .write = write_sysrq_trigger, 1087 .llseek = noop_llseek, 1088 }; 1089 1090 static void sysrq_init_procfs(void) 1091 { 1092 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1093 &proc_sysrq_trigger_operations)) 1094 pr_err("Failed to register proc interface\n"); 1095 } 1096 1097 #else 1098 1099 static inline void sysrq_init_procfs(void) 1100 { 1101 } 1102 1103 #endif /* CONFIG_PROC_FS */ 1104 1105 static int __init sysrq_init(void) 1106 { 1107 sysrq_init_procfs(); 1108 1109 if (sysrq_on()) 1110 sysrq_register_handler(); 1111 1112 return 0; 1113 } 1114 module_init(sysrq_init); 1115