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 /* we need to release the RCU read lock here, 137 * otherwise we get an annoying 138 * 'BUG: sleeping function called from invalid context' 139 * complaint from the kernel before the panic. 140 */ 141 rcu_read_unlock(); 142 panic_on_oops = 1; /* force panic */ 143 wmb(); 144 *killer = 1; 145 } 146 static struct sysrq_key_op sysrq_crash_op = { 147 .handler = sysrq_handle_crash, 148 .help_msg = "crash(c)", 149 .action_msg = "Trigger a crash", 150 .enable_mask = SYSRQ_ENABLE_DUMP, 151 }; 152 153 static void sysrq_handle_reboot(int key) 154 { 155 lockdep_off(); 156 local_irq_enable(); 157 emergency_restart(); 158 } 159 static struct sysrq_key_op sysrq_reboot_op = { 160 .handler = sysrq_handle_reboot, 161 .help_msg = "reboot(b)", 162 .action_msg = "Resetting", 163 .enable_mask = SYSRQ_ENABLE_BOOT, 164 }; 165 166 static void sysrq_handle_sync(int key) 167 { 168 emergency_sync(); 169 } 170 static struct sysrq_key_op sysrq_sync_op = { 171 .handler = sysrq_handle_sync, 172 .help_msg = "sync(s)", 173 .action_msg = "Emergency Sync", 174 .enable_mask = SYSRQ_ENABLE_SYNC, 175 }; 176 177 static void sysrq_handle_show_timers(int key) 178 { 179 sysrq_timer_list_show(); 180 } 181 182 static struct sysrq_key_op sysrq_show_timers_op = { 183 .handler = sysrq_handle_show_timers, 184 .help_msg = "show-all-timers(q)", 185 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 186 }; 187 188 static void sysrq_handle_mountro(int key) 189 { 190 emergency_remount(); 191 } 192 static struct sysrq_key_op sysrq_mountro_op = { 193 .handler = sysrq_handle_mountro, 194 .help_msg = "unmount(u)", 195 .action_msg = "Emergency Remount R/O", 196 .enable_mask = SYSRQ_ENABLE_REMOUNT, 197 }; 198 199 #ifdef CONFIG_LOCKDEP 200 static void sysrq_handle_showlocks(int key) 201 { 202 debug_show_all_locks(); 203 } 204 205 static struct sysrq_key_op sysrq_showlocks_op = { 206 .handler = sysrq_handle_showlocks, 207 .help_msg = "show-all-locks(d)", 208 .action_msg = "Show Locks Held", 209 }; 210 #else 211 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 212 #endif 213 214 #ifdef CONFIG_SMP 215 static DEFINE_SPINLOCK(show_lock); 216 217 static void showacpu(void *dummy) 218 { 219 unsigned long flags; 220 221 /* Idle CPUs have no interesting backtrace. */ 222 if (idle_cpu(smp_processor_id())) 223 return; 224 225 spin_lock_irqsave(&show_lock, flags); 226 pr_info("CPU%d:\n", smp_processor_id()); 227 show_stack(NULL, NULL); 228 spin_unlock_irqrestore(&show_lock, flags); 229 } 230 231 static void sysrq_showregs_othercpus(struct work_struct *dummy) 232 { 233 smp_call_function(showacpu, NULL, 0); 234 } 235 236 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 237 238 static void sysrq_handle_showallcpus(int key) 239 { 240 /* 241 * Fall back to the workqueue based printing if the 242 * backtrace printing did not succeed or the 243 * architecture has no support for it: 244 */ 245 if (!trigger_all_cpu_backtrace()) { 246 struct pt_regs *regs = get_irq_regs(); 247 248 if (regs) { 249 pr_info("CPU%d:\n", smp_processor_id()); 250 show_regs(regs); 251 } 252 schedule_work(&sysrq_showallcpus); 253 } 254 } 255 256 static struct sysrq_key_op sysrq_showallcpus_op = { 257 .handler = sysrq_handle_showallcpus, 258 .help_msg = "show-backtrace-all-active-cpus(l)", 259 .action_msg = "Show backtrace of all active CPUs", 260 .enable_mask = SYSRQ_ENABLE_DUMP, 261 }; 262 #endif 263 264 static void sysrq_handle_showregs(int key) 265 { 266 struct pt_regs *regs = get_irq_regs(); 267 if (regs) 268 show_regs(regs); 269 perf_event_print_debug(); 270 } 271 static struct sysrq_key_op sysrq_showregs_op = { 272 .handler = sysrq_handle_showregs, 273 .help_msg = "show-registers(p)", 274 .action_msg = "Show Regs", 275 .enable_mask = SYSRQ_ENABLE_DUMP, 276 }; 277 278 static void sysrq_handle_showstate(int key) 279 { 280 show_state(); 281 show_workqueue_state(); 282 } 283 static struct sysrq_key_op sysrq_showstate_op = { 284 .handler = sysrq_handle_showstate, 285 .help_msg = "show-task-states(t)", 286 .action_msg = "Show State", 287 .enable_mask = SYSRQ_ENABLE_DUMP, 288 }; 289 290 static void sysrq_handle_showstate_blocked(int key) 291 { 292 show_state_filter(TASK_UNINTERRUPTIBLE); 293 } 294 static struct sysrq_key_op sysrq_showstate_blocked_op = { 295 .handler = sysrq_handle_showstate_blocked, 296 .help_msg = "show-blocked-tasks(w)", 297 .action_msg = "Show Blocked State", 298 .enable_mask = SYSRQ_ENABLE_DUMP, 299 }; 300 301 #ifdef CONFIG_TRACING 302 #include <linux/ftrace.h> 303 304 static void sysrq_ftrace_dump(int key) 305 { 306 ftrace_dump(DUMP_ALL); 307 } 308 static struct sysrq_key_op sysrq_ftrace_dump_op = { 309 .handler = sysrq_ftrace_dump, 310 .help_msg = "dump-ftrace-buffer(z)", 311 .action_msg = "Dump ftrace buffer", 312 .enable_mask = SYSRQ_ENABLE_DUMP, 313 }; 314 #else 315 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 316 #endif 317 318 static void sysrq_handle_showmem(int key) 319 { 320 show_mem(0); 321 } 322 static struct sysrq_key_op sysrq_showmem_op = { 323 .handler = sysrq_handle_showmem, 324 .help_msg = "show-memory-usage(m)", 325 .action_msg = "Show Memory", 326 .enable_mask = SYSRQ_ENABLE_DUMP, 327 }; 328 329 /* 330 * Signal sysrq helper function. Sends a signal to all user processes. 331 */ 332 static void send_sig_all(int sig) 333 { 334 struct task_struct *p; 335 336 read_lock(&tasklist_lock); 337 for_each_process(p) { 338 if (p->flags & PF_KTHREAD) 339 continue; 340 if (is_global_init(p)) 341 continue; 342 343 do_send_sig_info(sig, SEND_SIG_FORCED, p, true); 344 } 345 read_unlock(&tasklist_lock); 346 } 347 348 static void sysrq_handle_term(int key) 349 { 350 send_sig_all(SIGTERM); 351 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 352 } 353 static struct sysrq_key_op sysrq_term_op = { 354 .handler = sysrq_handle_term, 355 .help_msg = "terminate-all-tasks(e)", 356 .action_msg = "Terminate All Tasks", 357 .enable_mask = SYSRQ_ENABLE_SIGNAL, 358 }; 359 360 static void moom_callback(struct work_struct *ignored) 361 { 362 const gfp_t gfp_mask = GFP_KERNEL; 363 struct oom_control oc = { 364 .zonelist = node_zonelist(first_memory_node, gfp_mask), 365 .nodemask = NULL, 366 .gfp_mask = gfp_mask, 367 .order = -1, 368 }; 369 370 mutex_lock(&oom_lock); 371 if (!out_of_memory(&oc)) 372 pr_info("OOM request ignored because killer is disabled\n"); 373 mutex_unlock(&oom_lock); 374 } 375 376 static DECLARE_WORK(moom_work, moom_callback); 377 378 static void sysrq_handle_moom(int key) 379 { 380 schedule_work(&moom_work); 381 } 382 static struct sysrq_key_op sysrq_moom_op = { 383 .handler = sysrq_handle_moom, 384 .help_msg = "memory-full-oom-kill(f)", 385 .action_msg = "Manual OOM execution", 386 .enable_mask = SYSRQ_ENABLE_SIGNAL, 387 }; 388 389 #ifdef CONFIG_BLOCK 390 static void sysrq_handle_thaw(int key) 391 { 392 emergency_thaw_all(); 393 } 394 static struct sysrq_key_op sysrq_thaw_op = { 395 .handler = sysrq_handle_thaw, 396 .help_msg = "thaw-filesystems(j)", 397 .action_msg = "Emergency Thaw of all frozen filesystems", 398 .enable_mask = SYSRQ_ENABLE_SIGNAL, 399 }; 400 #endif 401 402 static void sysrq_handle_kill(int key) 403 { 404 send_sig_all(SIGKILL); 405 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 406 } 407 static struct sysrq_key_op sysrq_kill_op = { 408 .handler = sysrq_handle_kill, 409 .help_msg = "kill-all-tasks(i)", 410 .action_msg = "Kill All Tasks", 411 .enable_mask = SYSRQ_ENABLE_SIGNAL, 412 }; 413 414 static void sysrq_handle_unrt(int key) 415 { 416 normalize_rt_tasks(); 417 } 418 static struct sysrq_key_op sysrq_unrt_op = { 419 .handler = sysrq_handle_unrt, 420 .help_msg = "nice-all-RT-tasks(n)", 421 .action_msg = "Nice All RT Tasks", 422 .enable_mask = SYSRQ_ENABLE_RTNICE, 423 }; 424 425 /* Key Operations table and lock */ 426 static DEFINE_SPINLOCK(sysrq_key_table_lock); 427 428 static struct sysrq_key_op *sysrq_key_table[36] = { 429 &sysrq_loglevel_op, /* 0 */ 430 &sysrq_loglevel_op, /* 1 */ 431 &sysrq_loglevel_op, /* 2 */ 432 &sysrq_loglevel_op, /* 3 */ 433 &sysrq_loglevel_op, /* 4 */ 434 &sysrq_loglevel_op, /* 5 */ 435 &sysrq_loglevel_op, /* 6 */ 436 &sysrq_loglevel_op, /* 7 */ 437 &sysrq_loglevel_op, /* 8 */ 438 &sysrq_loglevel_op, /* 9 */ 439 440 /* 441 * a: Don't use for system provided sysrqs, it is handled specially on 442 * sparc and will never arrive. 443 */ 444 NULL, /* a */ 445 &sysrq_reboot_op, /* b */ 446 &sysrq_crash_op, /* c & ibm_emac driver debug */ 447 &sysrq_showlocks_op, /* d */ 448 &sysrq_term_op, /* e */ 449 &sysrq_moom_op, /* f */ 450 /* g: May be registered for the kernel debugger */ 451 NULL, /* g */ 452 NULL, /* h - reserved for help */ 453 &sysrq_kill_op, /* i */ 454 #ifdef CONFIG_BLOCK 455 &sysrq_thaw_op, /* j */ 456 #else 457 NULL, /* j */ 458 #endif 459 &sysrq_SAK_op, /* k */ 460 #ifdef CONFIG_SMP 461 &sysrq_showallcpus_op, /* l */ 462 #else 463 NULL, /* l */ 464 #endif 465 &sysrq_showmem_op, /* m */ 466 &sysrq_unrt_op, /* n */ 467 /* o: This will often be registered as 'Off' at init time */ 468 NULL, /* o */ 469 &sysrq_showregs_op, /* p */ 470 &sysrq_show_timers_op, /* q */ 471 &sysrq_unraw_op, /* r */ 472 &sysrq_sync_op, /* s */ 473 &sysrq_showstate_op, /* t */ 474 &sysrq_mountro_op, /* u */ 475 /* v: May be registered for frame buffer console restore */ 476 NULL, /* v */ 477 &sysrq_showstate_blocked_op, /* w */ 478 /* x: May be registered on mips for TLB dump */ 479 /* x: May be registered on ppc/powerpc for xmon */ 480 /* x: May be registered on sparc64 for global PMU dump */ 481 NULL, /* x */ 482 /* y: May be registered on sparc64 for global register dump */ 483 NULL, /* y */ 484 &sysrq_ftrace_dump_op, /* z */ 485 }; 486 487 /* key2index calculation, -1 on invalid index */ 488 static int sysrq_key_table_key2index(int key) 489 { 490 int retval; 491 492 if ((key >= '0') && (key <= '9')) 493 retval = key - '0'; 494 else if ((key >= 'a') && (key <= 'z')) 495 retval = key + 10 - 'a'; 496 else 497 retval = -1; 498 return retval; 499 } 500 501 /* 502 * get and put functions for the table, exposed to modules. 503 */ 504 struct sysrq_key_op *__sysrq_get_key_op(int key) 505 { 506 struct sysrq_key_op *op_p = NULL; 507 int i; 508 509 i = sysrq_key_table_key2index(key); 510 if (i != -1) 511 op_p = sysrq_key_table[i]; 512 513 return op_p; 514 } 515 516 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 517 { 518 int i = sysrq_key_table_key2index(key); 519 520 if (i != -1) 521 sysrq_key_table[i] = op_p; 522 } 523 524 void __handle_sysrq(int key, bool check_mask) 525 { 526 struct sysrq_key_op *op_p; 527 int orig_log_level; 528 int i; 529 530 rcu_sysrq_start(); 531 rcu_read_lock(); 532 /* 533 * Raise the apparent loglevel to maximum so that the sysrq header 534 * is shown to provide the user with positive feedback. We do not 535 * simply emit this at KERN_EMERG as that would change message 536 * routing in the consumers of /proc/kmsg. 537 */ 538 orig_log_level = console_loglevel; 539 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 540 pr_info("SysRq : "); 541 542 op_p = __sysrq_get_key_op(key); 543 if (op_p) { 544 /* 545 * Should we check for enabled operations (/proc/sysrq-trigger 546 * should not) and is the invoked operation enabled? 547 */ 548 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 549 pr_cont("%s\n", op_p->action_msg); 550 console_loglevel = orig_log_level; 551 op_p->handler(key); 552 } else { 553 pr_cont("This sysrq operation is disabled.\n"); 554 } 555 } else { 556 pr_cont("HELP : "); 557 /* Only print the help msg once per handler */ 558 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 559 if (sysrq_key_table[i]) { 560 int j; 561 562 for (j = 0; sysrq_key_table[i] != 563 sysrq_key_table[j]; j++) 564 ; 565 if (j != i) 566 continue; 567 pr_cont("%s ", sysrq_key_table[i]->help_msg); 568 } 569 } 570 pr_cont("\n"); 571 console_loglevel = orig_log_level; 572 } 573 rcu_read_unlock(); 574 rcu_sysrq_end(); 575 } 576 577 void handle_sysrq(int key) 578 { 579 if (sysrq_on()) 580 __handle_sysrq(key, true); 581 } 582 EXPORT_SYMBOL(handle_sysrq); 583 584 #ifdef CONFIG_INPUT 585 static int sysrq_reset_downtime_ms; 586 587 /* Simple translation table for the SysRq keys */ 588 static const unsigned char sysrq_xlate[KEY_CNT] = 589 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 590 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 591 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 592 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 593 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 594 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 595 "\r\000/"; /* 0x60 - 0x6f */ 596 597 struct sysrq_state { 598 struct input_handle handle; 599 struct work_struct reinject_work; 600 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 601 unsigned int alt; 602 unsigned int alt_use; 603 bool active; 604 bool need_reinject; 605 bool reinjecting; 606 607 /* reset sequence handling */ 608 bool reset_canceled; 609 bool reset_requested; 610 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 611 int reset_seq_len; 612 int reset_seq_cnt; 613 int reset_seq_version; 614 struct timer_list keyreset_timer; 615 }; 616 617 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 618 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 619 static unsigned int sysrq_reset_seq_len; 620 static unsigned int sysrq_reset_seq_version = 1; 621 622 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 623 { 624 int i; 625 unsigned short key; 626 627 state->reset_seq_cnt = 0; 628 629 for (i = 0; i < sysrq_reset_seq_len; i++) { 630 key = sysrq_reset_seq[i]; 631 632 if (key == KEY_RESERVED || key > KEY_MAX) 633 break; 634 635 __set_bit(key, state->reset_keybit); 636 state->reset_seq_len++; 637 638 if (test_bit(key, state->key_down)) 639 state->reset_seq_cnt++; 640 } 641 642 /* Disable reset until old keys are not released */ 643 state->reset_canceled = state->reset_seq_cnt != 0; 644 645 state->reset_seq_version = sysrq_reset_seq_version; 646 } 647 648 static void sysrq_do_reset(unsigned long _state) 649 { 650 struct sysrq_state *state = (struct sysrq_state *) _state; 651 652 state->reset_requested = true; 653 654 sys_sync(); 655 kernel_restart(NULL); 656 } 657 658 static void sysrq_handle_reset_request(struct sysrq_state *state) 659 { 660 if (state->reset_requested) 661 __handle_sysrq(sysrq_xlate[KEY_B], false); 662 663 if (sysrq_reset_downtime_ms) 664 mod_timer(&state->keyreset_timer, 665 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 666 else 667 sysrq_do_reset((unsigned long)state); 668 } 669 670 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 671 unsigned int code, int value) 672 { 673 if (!test_bit(code, state->reset_keybit)) { 674 /* 675 * Pressing any key _not_ in reset sequence cancels 676 * the reset sequence. Also cancelling the timer in 677 * case additional keys were pressed after a reset 678 * has been requested. 679 */ 680 if (value && state->reset_seq_cnt) { 681 state->reset_canceled = true; 682 del_timer(&state->keyreset_timer); 683 } 684 } else if (value == 0) { 685 /* 686 * Key release - all keys in the reset sequence need 687 * to be pressed and held for the reset timeout 688 * to hold. 689 */ 690 del_timer(&state->keyreset_timer); 691 692 if (--state->reset_seq_cnt == 0) 693 state->reset_canceled = false; 694 } else if (value == 1) { 695 /* key press, not autorepeat */ 696 if (++state->reset_seq_cnt == state->reset_seq_len && 697 !state->reset_canceled) { 698 sysrq_handle_reset_request(state); 699 } 700 } 701 } 702 703 #ifdef CONFIG_OF 704 static void sysrq_of_get_keyreset_config(void) 705 { 706 u32 key; 707 struct device_node *np; 708 struct property *prop; 709 const __be32 *p; 710 711 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 712 if (!np) { 713 pr_debug("No sysrq node found"); 714 return; 715 } 716 717 /* Reset in case a __weak definition was present */ 718 sysrq_reset_seq_len = 0; 719 720 of_property_for_each_u32(np, "keyset", prop, p, key) { 721 if (key == KEY_RESERVED || key > KEY_MAX || 722 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 723 break; 724 725 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 726 } 727 728 /* Get reset timeout if any. */ 729 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 730 } 731 #else 732 static void sysrq_of_get_keyreset_config(void) 733 { 734 } 735 #endif 736 737 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 738 { 739 struct sysrq_state *sysrq = 740 container_of(work, struct sysrq_state, reinject_work); 741 struct input_handle *handle = &sysrq->handle; 742 unsigned int alt_code = sysrq->alt_use; 743 744 if (sysrq->need_reinject) { 745 /* we do not want the assignment to be reordered */ 746 sysrq->reinjecting = true; 747 mb(); 748 749 /* Simulate press and release of Alt + SysRq */ 750 input_inject_event(handle, EV_KEY, alt_code, 1); 751 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 752 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 753 754 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 755 input_inject_event(handle, EV_KEY, alt_code, 0); 756 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 757 758 mb(); 759 sysrq->reinjecting = false; 760 } 761 } 762 763 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 764 unsigned int code, int value) 765 { 766 bool was_active = sysrq->active; 767 bool suppress; 768 769 switch (code) { 770 771 case KEY_LEFTALT: 772 case KEY_RIGHTALT: 773 if (!value) { 774 /* One of ALTs is being released */ 775 if (sysrq->active && code == sysrq->alt_use) 776 sysrq->active = false; 777 778 sysrq->alt = KEY_RESERVED; 779 780 } else if (value != 2) { 781 sysrq->alt = code; 782 sysrq->need_reinject = false; 783 } 784 break; 785 786 case KEY_SYSRQ: 787 if (value == 1 && sysrq->alt != KEY_RESERVED) { 788 sysrq->active = true; 789 sysrq->alt_use = sysrq->alt; 790 /* 791 * If nothing else will be pressed we'll need 792 * to re-inject Alt-SysRq keysroke. 793 */ 794 sysrq->need_reinject = true; 795 } 796 797 /* 798 * Pretend that sysrq was never pressed at all. This 799 * is needed to properly handle KGDB which will try 800 * to release all keys after exiting debugger. If we 801 * do not clear key bit it KGDB will end up sending 802 * release events for Alt and SysRq, potentially 803 * triggering print screen function. 804 */ 805 if (sysrq->active) 806 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 807 808 break; 809 810 default: 811 if (sysrq->active && value && value != 2) { 812 sysrq->need_reinject = false; 813 __handle_sysrq(sysrq_xlate[code], true); 814 } 815 break; 816 } 817 818 suppress = sysrq->active; 819 820 if (!sysrq->active) { 821 822 /* 823 * See if reset sequence has changed since the last time. 824 */ 825 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 826 sysrq_parse_reset_sequence(sysrq); 827 828 /* 829 * If we are not suppressing key presses keep track of 830 * keyboard state so we can release keys that have been 831 * pressed before entering SysRq mode. 832 */ 833 if (value) 834 set_bit(code, sysrq->key_down); 835 else 836 clear_bit(code, sysrq->key_down); 837 838 if (was_active) 839 schedule_work(&sysrq->reinject_work); 840 841 /* Check for reset sequence */ 842 sysrq_detect_reset_sequence(sysrq, code, value); 843 844 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 845 /* 846 * Pass on release events for keys that was pressed before 847 * entering SysRq mode. 848 */ 849 suppress = false; 850 } 851 852 return suppress; 853 } 854 855 static bool sysrq_filter(struct input_handle *handle, 856 unsigned int type, unsigned int code, int value) 857 { 858 struct sysrq_state *sysrq = handle->private; 859 bool suppress; 860 861 /* 862 * Do not filter anything if we are in the process of re-injecting 863 * Alt+SysRq combination. 864 */ 865 if (sysrq->reinjecting) 866 return false; 867 868 switch (type) { 869 870 case EV_SYN: 871 suppress = false; 872 break; 873 874 case EV_KEY: 875 suppress = sysrq_handle_keypress(sysrq, code, value); 876 break; 877 878 default: 879 suppress = sysrq->active; 880 break; 881 } 882 883 return suppress; 884 } 885 886 static int sysrq_connect(struct input_handler *handler, 887 struct input_dev *dev, 888 const struct input_device_id *id) 889 { 890 struct sysrq_state *sysrq; 891 int error; 892 893 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 894 if (!sysrq) 895 return -ENOMEM; 896 897 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 898 899 sysrq->handle.dev = dev; 900 sysrq->handle.handler = handler; 901 sysrq->handle.name = "sysrq"; 902 sysrq->handle.private = sysrq; 903 setup_timer(&sysrq->keyreset_timer, 904 sysrq_do_reset, (unsigned long)sysrq); 905 906 error = input_register_handle(&sysrq->handle); 907 if (error) { 908 pr_err("Failed to register input sysrq handler, error %d\n", 909 error); 910 goto err_free; 911 } 912 913 error = input_open_device(&sysrq->handle); 914 if (error) { 915 pr_err("Failed to open input device, error %d\n", error); 916 goto err_unregister; 917 } 918 919 return 0; 920 921 err_unregister: 922 input_unregister_handle(&sysrq->handle); 923 err_free: 924 kfree(sysrq); 925 return error; 926 } 927 928 static void sysrq_disconnect(struct input_handle *handle) 929 { 930 struct sysrq_state *sysrq = handle->private; 931 932 input_close_device(handle); 933 cancel_work_sync(&sysrq->reinject_work); 934 del_timer_sync(&sysrq->keyreset_timer); 935 input_unregister_handle(handle); 936 kfree(sysrq); 937 } 938 939 /* 940 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 941 * keyboards have SysRq key predefined and so user may add it to keymap 942 * later, but we expect all such keyboards to have left alt. 943 */ 944 static const struct input_device_id sysrq_ids[] = { 945 { 946 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 947 INPUT_DEVICE_ID_MATCH_KEYBIT, 948 .evbit = { BIT_MASK(EV_KEY) }, 949 .keybit = { BIT_MASK(KEY_LEFTALT) }, 950 }, 951 { }, 952 }; 953 954 static struct input_handler sysrq_handler = { 955 .filter = sysrq_filter, 956 .connect = sysrq_connect, 957 .disconnect = sysrq_disconnect, 958 .name = "sysrq", 959 .id_table = sysrq_ids, 960 }; 961 962 static bool sysrq_handler_registered; 963 964 static inline void sysrq_register_handler(void) 965 { 966 int error; 967 968 sysrq_of_get_keyreset_config(); 969 970 error = input_register_handler(&sysrq_handler); 971 if (error) 972 pr_err("Failed to register input handler, error %d", error); 973 else 974 sysrq_handler_registered = true; 975 } 976 977 static inline void sysrq_unregister_handler(void) 978 { 979 if (sysrq_handler_registered) { 980 input_unregister_handler(&sysrq_handler); 981 sysrq_handler_registered = false; 982 } 983 } 984 985 static int sysrq_reset_seq_param_set(const char *buffer, 986 const struct kernel_param *kp) 987 { 988 unsigned long val; 989 int error; 990 991 error = kstrtoul(buffer, 0, &val); 992 if (error < 0) 993 return error; 994 995 if (val > KEY_MAX) 996 return -EINVAL; 997 998 *((unsigned short *)kp->arg) = val; 999 sysrq_reset_seq_version++; 1000 1001 return 0; 1002 } 1003 1004 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1005 .get = param_get_ushort, 1006 .set = sysrq_reset_seq_param_set, 1007 }; 1008 1009 #define param_check_sysrq_reset_seq(name, p) \ 1010 __param_check(name, p, unsigned short) 1011 1012 /* 1013 * not really modular, but the easiest way to keep compat with existing 1014 * bootargs behaviour is to continue using module_param here. 1015 */ 1016 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1017 &sysrq_reset_seq_len, 0644); 1018 1019 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1020 1021 #else 1022 1023 static inline void sysrq_register_handler(void) 1024 { 1025 } 1026 1027 static inline void sysrq_unregister_handler(void) 1028 { 1029 } 1030 1031 #endif /* CONFIG_INPUT */ 1032 1033 int sysrq_toggle_support(int enable_mask) 1034 { 1035 bool was_enabled = sysrq_on(); 1036 1037 sysrq_enabled = enable_mask; 1038 1039 if (was_enabled != sysrq_on()) { 1040 if (sysrq_on()) 1041 sysrq_register_handler(); 1042 else 1043 sysrq_unregister_handler(); 1044 } 1045 1046 return 0; 1047 } 1048 1049 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1050 struct sysrq_key_op *remove_op_p) 1051 { 1052 int retval; 1053 1054 spin_lock(&sysrq_key_table_lock); 1055 if (__sysrq_get_key_op(key) == remove_op_p) { 1056 __sysrq_put_key_op(key, insert_op_p); 1057 retval = 0; 1058 } else { 1059 retval = -1; 1060 } 1061 spin_unlock(&sysrq_key_table_lock); 1062 1063 /* 1064 * A concurrent __handle_sysrq either got the old op or the new op. 1065 * Wait for it to go away before returning, so the code for an old 1066 * op is not freed (eg. on module unload) while it is in use. 1067 */ 1068 synchronize_rcu(); 1069 1070 return retval; 1071 } 1072 1073 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1074 { 1075 return __sysrq_swap_key_ops(key, op_p, NULL); 1076 } 1077 EXPORT_SYMBOL(register_sysrq_key); 1078 1079 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1080 { 1081 return __sysrq_swap_key_ops(key, NULL, op_p); 1082 } 1083 EXPORT_SYMBOL(unregister_sysrq_key); 1084 1085 #ifdef CONFIG_PROC_FS 1086 /* 1087 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1088 */ 1089 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1090 size_t count, loff_t *ppos) 1091 { 1092 if (count) { 1093 char c; 1094 1095 if (get_user(c, buf)) 1096 return -EFAULT; 1097 __handle_sysrq(c, false); 1098 } 1099 1100 return count; 1101 } 1102 1103 static const struct file_operations proc_sysrq_trigger_operations = { 1104 .write = write_sysrq_trigger, 1105 .llseek = noop_llseek, 1106 }; 1107 1108 static void sysrq_init_procfs(void) 1109 { 1110 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1111 &proc_sysrq_trigger_operations)) 1112 pr_err("Failed to register proc interface\n"); 1113 } 1114 1115 #else 1116 1117 static inline void sysrq_init_procfs(void) 1118 { 1119 } 1120 1121 #endif /* CONFIG_PROC_FS */ 1122 1123 static int __init sysrq_init(void) 1124 { 1125 sysrq_init_procfs(); 1126 1127 if (sysrq_on()) 1128 sysrq_register_handler(); 1129 1130 return 0; 1131 } 1132 device_initcall(sysrq_init); 1133