1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Linux Magic System Request Key Hacks 4 * 5 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz> 6 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz> 7 * 8 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com> 9 * overhauled to use key registration 10 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies 11 * 12 * Copyright (c) 2010 Dmitry Torokhov 13 * Input handler conversion 14 */ 15 16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 17 18 #include <linux/sched/signal.h> 19 #include <linux/sched/rt.h> 20 #include <linux/sched/debug.h> 21 #include <linux/sched/task.h> 22 #include <linux/interrupt.h> 23 #include <linux/mm.h> 24 #include <linux/fs.h> 25 #include <linux/mount.h> 26 #include <linux/kdev_t.h> 27 #include <linux/major.h> 28 #include <linux/reboot.h> 29 #include <linux/sysrq.h> 30 #include <linux/kbd_kern.h> 31 #include <linux/proc_fs.h> 32 #include <linux/nmi.h> 33 #include <linux/quotaops.h> 34 #include <linux/perf_event.h> 35 #include <linux/kernel.h> 36 #include <linux/module.h> 37 #include <linux/suspend.h> 38 #include <linux/writeback.h> 39 #include <linux/swap.h> 40 #include <linux/spinlock.h> 41 #include <linux/vt_kern.h> 42 #include <linux/workqueue.h> 43 #include <linux/hrtimer.h> 44 #include <linux/oom.h> 45 #include <linux/slab.h> 46 #include <linux/input.h> 47 #include <linux/uaccess.h> 48 #include <linux/moduleparam.h> 49 #include <linux/jiffies.h> 50 #include <linux/syscalls.h> 51 #include <linux/of.h> 52 #include <linux/rcupdate.h> 53 54 #include <asm/ptrace.h> 55 #include <asm/irq_regs.h> 56 57 /* Whether we react on sysrq keys or just ignore them */ 58 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; 59 static bool __read_mostly sysrq_always_enabled; 60 61 static bool sysrq_on(void) 62 { 63 return sysrq_enabled || sysrq_always_enabled; 64 } 65 66 /* 67 * A value of 1 means 'all', other nonzero values are an op mask: 68 */ 69 static bool sysrq_on_mask(int mask) 70 { 71 return sysrq_always_enabled || 72 sysrq_enabled == 1 || 73 (sysrq_enabled & mask); 74 } 75 76 static int __init sysrq_always_enabled_setup(char *str) 77 { 78 sysrq_always_enabled = true; 79 pr_info("sysrq always enabled.\n"); 80 81 return 1; 82 } 83 84 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 85 86 87 static void sysrq_handle_loglevel(int key) 88 { 89 int i; 90 91 i = key - '0'; 92 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 93 pr_info("Loglevel set to %d\n", i); 94 console_loglevel = i; 95 } 96 static struct sysrq_key_op sysrq_loglevel_op = { 97 .handler = sysrq_handle_loglevel, 98 .help_msg = "loglevel(0-9)", 99 .action_msg = "Changing Loglevel", 100 .enable_mask = SYSRQ_ENABLE_LOG, 101 }; 102 103 #ifdef CONFIG_VT 104 static void sysrq_handle_SAK(int key) 105 { 106 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 107 schedule_work(SAK_work); 108 } 109 static struct sysrq_key_op sysrq_SAK_op = { 110 .handler = sysrq_handle_SAK, 111 .help_msg = "sak(k)", 112 .action_msg = "SAK", 113 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 114 }; 115 #else 116 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL) 117 #endif 118 119 #ifdef CONFIG_VT 120 static void sysrq_handle_unraw(int key) 121 { 122 vt_reset_unicode(fg_console); 123 } 124 125 static struct sysrq_key_op sysrq_unraw_op = { 126 .handler = sysrq_handle_unraw, 127 .help_msg = "unraw(r)", 128 .action_msg = "Keyboard mode set to system default", 129 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 130 }; 131 #else 132 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL) 133 #endif /* CONFIG_VT */ 134 135 static void sysrq_handle_crash(int key) 136 { 137 char *killer = NULL; 138 139 /* we need to release the RCU read lock here, 140 * otherwise we get an annoying 141 * 'BUG: sleeping function called from invalid context' 142 * complaint from the kernel before the panic. 143 */ 144 rcu_read_unlock(); 145 panic_on_oops = 1; /* force panic */ 146 wmb(); 147 *killer = 1; 148 } 149 static struct sysrq_key_op sysrq_crash_op = { 150 .handler = sysrq_handle_crash, 151 .help_msg = "crash(c)", 152 .action_msg = "Trigger a crash", 153 .enable_mask = SYSRQ_ENABLE_DUMP, 154 }; 155 156 static void sysrq_handle_reboot(int key) 157 { 158 lockdep_off(); 159 local_irq_enable(); 160 emergency_restart(); 161 } 162 static struct sysrq_key_op sysrq_reboot_op = { 163 .handler = sysrq_handle_reboot, 164 .help_msg = "reboot(b)", 165 .action_msg = "Resetting", 166 .enable_mask = SYSRQ_ENABLE_BOOT, 167 }; 168 169 static void sysrq_handle_sync(int key) 170 { 171 emergency_sync(); 172 } 173 static struct sysrq_key_op sysrq_sync_op = { 174 .handler = sysrq_handle_sync, 175 .help_msg = "sync(s)", 176 .action_msg = "Emergency Sync", 177 .enable_mask = SYSRQ_ENABLE_SYNC, 178 }; 179 180 static void sysrq_handle_show_timers(int key) 181 { 182 sysrq_timer_list_show(); 183 } 184 185 static struct sysrq_key_op sysrq_show_timers_op = { 186 .handler = sysrq_handle_show_timers, 187 .help_msg = "show-all-timers(q)", 188 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 189 }; 190 191 static void sysrq_handle_mountro(int key) 192 { 193 emergency_remount(); 194 } 195 static struct sysrq_key_op sysrq_mountro_op = { 196 .handler = sysrq_handle_mountro, 197 .help_msg = "unmount(u)", 198 .action_msg = "Emergency Remount R/O", 199 .enable_mask = SYSRQ_ENABLE_REMOUNT, 200 }; 201 202 #ifdef CONFIG_LOCKDEP 203 static void sysrq_handle_showlocks(int key) 204 { 205 debug_show_all_locks(); 206 } 207 208 static struct sysrq_key_op sysrq_showlocks_op = { 209 .handler = sysrq_handle_showlocks, 210 .help_msg = "show-all-locks(d)", 211 .action_msg = "Show Locks Held", 212 }; 213 #else 214 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 215 #endif 216 217 #ifdef CONFIG_SMP 218 static DEFINE_SPINLOCK(show_lock); 219 220 static void showacpu(void *dummy) 221 { 222 unsigned long flags; 223 224 /* Idle CPUs have no interesting backtrace. */ 225 if (idle_cpu(smp_processor_id())) 226 return; 227 228 spin_lock_irqsave(&show_lock, flags); 229 pr_info("CPU%d:\n", smp_processor_id()); 230 show_stack(NULL, NULL); 231 spin_unlock_irqrestore(&show_lock, flags); 232 } 233 234 static void sysrq_showregs_othercpus(struct work_struct *dummy) 235 { 236 smp_call_function(showacpu, NULL, 0); 237 } 238 239 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 240 241 static void sysrq_handle_showallcpus(int key) 242 { 243 /* 244 * Fall back to the workqueue based printing if the 245 * backtrace printing did not succeed or the 246 * architecture has no support for it: 247 */ 248 if (!trigger_all_cpu_backtrace()) { 249 struct pt_regs *regs = NULL; 250 251 if (in_irq()) 252 regs = get_irq_regs(); 253 if (regs) { 254 pr_info("CPU%d:\n", smp_processor_id()); 255 show_regs(regs); 256 } 257 schedule_work(&sysrq_showallcpus); 258 } 259 } 260 261 static struct sysrq_key_op sysrq_showallcpus_op = { 262 .handler = sysrq_handle_showallcpus, 263 .help_msg = "show-backtrace-all-active-cpus(l)", 264 .action_msg = "Show backtrace of all active CPUs", 265 .enable_mask = SYSRQ_ENABLE_DUMP, 266 }; 267 #endif 268 269 static void sysrq_handle_showregs(int key) 270 { 271 struct pt_regs *regs = NULL; 272 273 if (in_irq()) 274 regs = get_irq_regs(); 275 if (regs) 276 show_regs(regs); 277 perf_event_print_debug(); 278 } 279 static struct sysrq_key_op sysrq_showregs_op = { 280 .handler = sysrq_handle_showregs, 281 .help_msg = "show-registers(p)", 282 .action_msg = "Show Regs", 283 .enable_mask = SYSRQ_ENABLE_DUMP, 284 }; 285 286 static void sysrq_handle_showstate(int key) 287 { 288 show_state(); 289 show_workqueue_state(); 290 } 291 static struct sysrq_key_op sysrq_showstate_op = { 292 .handler = sysrq_handle_showstate, 293 .help_msg = "show-task-states(t)", 294 .action_msg = "Show State", 295 .enable_mask = SYSRQ_ENABLE_DUMP, 296 }; 297 298 static void sysrq_handle_showstate_blocked(int key) 299 { 300 show_state_filter(TASK_UNINTERRUPTIBLE); 301 } 302 static struct sysrq_key_op sysrq_showstate_blocked_op = { 303 .handler = sysrq_handle_showstate_blocked, 304 .help_msg = "show-blocked-tasks(w)", 305 .action_msg = "Show Blocked State", 306 .enable_mask = SYSRQ_ENABLE_DUMP, 307 }; 308 309 #ifdef CONFIG_TRACING 310 #include <linux/ftrace.h> 311 312 static void sysrq_ftrace_dump(int key) 313 { 314 ftrace_dump(DUMP_ALL); 315 } 316 static struct sysrq_key_op sysrq_ftrace_dump_op = { 317 .handler = sysrq_ftrace_dump, 318 .help_msg = "dump-ftrace-buffer(z)", 319 .action_msg = "Dump ftrace buffer", 320 .enable_mask = SYSRQ_ENABLE_DUMP, 321 }; 322 #else 323 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 324 #endif 325 326 static void sysrq_handle_showmem(int key) 327 { 328 show_mem(0, NULL); 329 } 330 static struct sysrq_key_op sysrq_showmem_op = { 331 .handler = sysrq_handle_showmem, 332 .help_msg = "show-memory-usage(m)", 333 .action_msg = "Show Memory", 334 .enable_mask = SYSRQ_ENABLE_DUMP, 335 }; 336 337 /* 338 * Signal sysrq helper function. Sends a signal to all user processes. 339 */ 340 static void send_sig_all(int sig) 341 { 342 struct task_struct *p; 343 344 read_lock(&tasklist_lock); 345 for_each_process(p) { 346 if (p->flags & PF_KTHREAD) 347 continue; 348 if (is_global_init(p)) 349 continue; 350 351 do_send_sig_info(sig, SEND_SIG_FORCED, p, true); 352 } 353 read_unlock(&tasklist_lock); 354 } 355 356 static void sysrq_handle_term(int key) 357 { 358 send_sig_all(SIGTERM); 359 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 360 } 361 static struct sysrq_key_op sysrq_term_op = { 362 .handler = sysrq_handle_term, 363 .help_msg = "terminate-all-tasks(e)", 364 .action_msg = "Terminate All Tasks", 365 .enable_mask = SYSRQ_ENABLE_SIGNAL, 366 }; 367 368 static void moom_callback(struct work_struct *ignored) 369 { 370 const gfp_t gfp_mask = GFP_KERNEL; 371 struct oom_control oc = { 372 .zonelist = node_zonelist(first_memory_node, gfp_mask), 373 .nodemask = NULL, 374 .memcg = NULL, 375 .gfp_mask = gfp_mask, 376 .order = -1, 377 }; 378 379 mutex_lock(&oom_lock); 380 if (!out_of_memory(&oc)) 381 pr_info("OOM request ignored. No task eligible\n"); 382 mutex_unlock(&oom_lock); 383 } 384 385 static DECLARE_WORK(moom_work, moom_callback); 386 387 static void sysrq_handle_moom(int key) 388 { 389 schedule_work(&moom_work); 390 } 391 static struct sysrq_key_op sysrq_moom_op = { 392 .handler = sysrq_handle_moom, 393 .help_msg = "memory-full-oom-kill(f)", 394 .action_msg = "Manual OOM execution", 395 .enable_mask = SYSRQ_ENABLE_SIGNAL, 396 }; 397 398 #ifdef CONFIG_BLOCK 399 static void sysrq_handle_thaw(int key) 400 { 401 emergency_thaw_all(); 402 } 403 static struct sysrq_key_op sysrq_thaw_op = { 404 .handler = sysrq_handle_thaw, 405 .help_msg = "thaw-filesystems(j)", 406 .action_msg = "Emergency Thaw of all frozen filesystems", 407 .enable_mask = SYSRQ_ENABLE_SIGNAL, 408 }; 409 #endif 410 411 static void sysrq_handle_kill(int key) 412 { 413 send_sig_all(SIGKILL); 414 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 415 } 416 static struct sysrq_key_op sysrq_kill_op = { 417 .handler = sysrq_handle_kill, 418 .help_msg = "kill-all-tasks(i)", 419 .action_msg = "Kill All Tasks", 420 .enable_mask = SYSRQ_ENABLE_SIGNAL, 421 }; 422 423 static void sysrq_handle_unrt(int key) 424 { 425 normalize_rt_tasks(); 426 } 427 static struct sysrq_key_op sysrq_unrt_op = { 428 .handler = sysrq_handle_unrt, 429 .help_msg = "nice-all-RT-tasks(n)", 430 .action_msg = "Nice All RT Tasks", 431 .enable_mask = SYSRQ_ENABLE_RTNICE, 432 }; 433 434 /* Key Operations table and lock */ 435 static DEFINE_SPINLOCK(sysrq_key_table_lock); 436 437 static struct sysrq_key_op *sysrq_key_table[36] = { 438 &sysrq_loglevel_op, /* 0 */ 439 &sysrq_loglevel_op, /* 1 */ 440 &sysrq_loglevel_op, /* 2 */ 441 &sysrq_loglevel_op, /* 3 */ 442 &sysrq_loglevel_op, /* 4 */ 443 &sysrq_loglevel_op, /* 5 */ 444 &sysrq_loglevel_op, /* 6 */ 445 &sysrq_loglevel_op, /* 7 */ 446 &sysrq_loglevel_op, /* 8 */ 447 &sysrq_loglevel_op, /* 9 */ 448 449 /* 450 * a: Don't use for system provided sysrqs, it is handled specially on 451 * sparc and will never arrive. 452 */ 453 NULL, /* a */ 454 &sysrq_reboot_op, /* b */ 455 &sysrq_crash_op, /* c */ 456 &sysrq_showlocks_op, /* d */ 457 &sysrq_term_op, /* e */ 458 &sysrq_moom_op, /* f */ 459 /* g: May be registered for the kernel debugger */ 460 NULL, /* g */ 461 NULL, /* h - reserved for help */ 462 &sysrq_kill_op, /* i */ 463 #ifdef CONFIG_BLOCK 464 &sysrq_thaw_op, /* j */ 465 #else 466 NULL, /* j */ 467 #endif 468 &sysrq_SAK_op, /* k */ 469 #ifdef CONFIG_SMP 470 &sysrq_showallcpus_op, /* l */ 471 #else 472 NULL, /* l */ 473 #endif 474 &sysrq_showmem_op, /* m */ 475 &sysrq_unrt_op, /* n */ 476 /* o: This will often be registered as 'Off' at init time */ 477 NULL, /* o */ 478 &sysrq_showregs_op, /* p */ 479 &sysrq_show_timers_op, /* q */ 480 &sysrq_unraw_op, /* r */ 481 &sysrq_sync_op, /* s */ 482 &sysrq_showstate_op, /* t */ 483 &sysrq_mountro_op, /* u */ 484 /* v: May be registered for frame buffer console restore */ 485 NULL, /* v */ 486 &sysrq_showstate_blocked_op, /* w */ 487 /* x: May be registered on mips for TLB dump */ 488 /* x: May be registered on ppc/powerpc for xmon */ 489 /* x: May be registered on sparc64 for global PMU dump */ 490 NULL, /* x */ 491 /* y: May be registered on sparc64 for global register dump */ 492 NULL, /* y */ 493 &sysrq_ftrace_dump_op, /* z */ 494 }; 495 496 /* key2index calculation, -1 on invalid index */ 497 static int sysrq_key_table_key2index(int key) 498 { 499 int retval; 500 501 if ((key >= '0') && (key <= '9')) 502 retval = key - '0'; 503 else if ((key >= 'a') && (key <= 'z')) 504 retval = key + 10 - 'a'; 505 else 506 retval = -1; 507 return retval; 508 } 509 510 /* 511 * get and put functions for the table, exposed to modules. 512 */ 513 struct sysrq_key_op *__sysrq_get_key_op(int key) 514 { 515 struct sysrq_key_op *op_p = NULL; 516 int i; 517 518 i = sysrq_key_table_key2index(key); 519 if (i != -1) 520 op_p = sysrq_key_table[i]; 521 522 return op_p; 523 } 524 525 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 526 { 527 int i = sysrq_key_table_key2index(key); 528 529 if (i != -1) 530 sysrq_key_table[i] = op_p; 531 } 532 533 void __handle_sysrq(int key, bool check_mask) 534 { 535 struct sysrq_key_op *op_p; 536 int orig_log_level; 537 int i; 538 539 rcu_sysrq_start(); 540 rcu_read_lock(); 541 /* 542 * Raise the apparent loglevel to maximum so that the sysrq header 543 * is shown to provide the user with positive feedback. We do not 544 * simply emit this at KERN_EMERG as that would change message 545 * routing in the consumers of /proc/kmsg. 546 */ 547 orig_log_level = console_loglevel; 548 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 549 pr_info("SysRq : "); 550 551 op_p = __sysrq_get_key_op(key); 552 if (op_p) { 553 /* 554 * Should we check for enabled operations (/proc/sysrq-trigger 555 * should not) and is the invoked operation enabled? 556 */ 557 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 558 pr_cont("%s\n", op_p->action_msg); 559 console_loglevel = orig_log_level; 560 op_p->handler(key); 561 } else { 562 pr_cont("This sysrq operation is disabled.\n"); 563 } 564 } else { 565 pr_cont("HELP : "); 566 /* Only print the help msg once per handler */ 567 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 568 if (sysrq_key_table[i]) { 569 int j; 570 571 for (j = 0; sysrq_key_table[i] != 572 sysrq_key_table[j]; j++) 573 ; 574 if (j != i) 575 continue; 576 pr_cont("%s ", sysrq_key_table[i]->help_msg); 577 } 578 } 579 pr_cont("\n"); 580 console_loglevel = orig_log_level; 581 } 582 rcu_read_unlock(); 583 rcu_sysrq_end(); 584 } 585 586 void handle_sysrq(int key) 587 { 588 if (sysrq_on()) 589 __handle_sysrq(key, true); 590 } 591 EXPORT_SYMBOL(handle_sysrq); 592 593 #ifdef CONFIG_INPUT 594 static int sysrq_reset_downtime_ms; 595 596 /* Simple translation table for the SysRq keys */ 597 static const unsigned char sysrq_xlate[KEY_CNT] = 598 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 599 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 600 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 601 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 602 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 603 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 604 "\r\000/"; /* 0x60 - 0x6f */ 605 606 struct sysrq_state { 607 struct input_handle handle; 608 struct work_struct reinject_work; 609 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 610 unsigned int alt; 611 unsigned int alt_use; 612 bool active; 613 bool need_reinject; 614 bool reinjecting; 615 616 /* reset sequence handling */ 617 bool reset_canceled; 618 bool reset_requested; 619 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 620 int reset_seq_len; 621 int reset_seq_cnt; 622 int reset_seq_version; 623 struct timer_list keyreset_timer; 624 }; 625 626 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 627 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 628 static unsigned int sysrq_reset_seq_len; 629 static unsigned int sysrq_reset_seq_version = 1; 630 631 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 632 { 633 int i; 634 unsigned short key; 635 636 state->reset_seq_cnt = 0; 637 638 for (i = 0; i < sysrq_reset_seq_len; i++) { 639 key = sysrq_reset_seq[i]; 640 641 if (key == KEY_RESERVED || key > KEY_MAX) 642 break; 643 644 __set_bit(key, state->reset_keybit); 645 state->reset_seq_len++; 646 647 if (test_bit(key, state->key_down)) 648 state->reset_seq_cnt++; 649 } 650 651 /* Disable reset until old keys are not released */ 652 state->reset_canceled = state->reset_seq_cnt != 0; 653 654 state->reset_seq_version = sysrq_reset_seq_version; 655 } 656 657 static void sysrq_do_reset(struct timer_list *t) 658 { 659 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 660 661 state->reset_requested = true; 662 663 sys_sync(); 664 kernel_restart(NULL); 665 } 666 667 static void sysrq_handle_reset_request(struct sysrq_state *state) 668 { 669 if (state->reset_requested) 670 __handle_sysrq(sysrq_xlate[KEY_B], false); 671 672 if (sysrq_reset_downtime_ms) 673 mod_timer(&state->keyreset_timer, 674 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 675 else 676 sysrq_do_reset(&state->keyreset_timer); 677 } 678 679 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 680 unsigned int code, int value) 681 { 682 if (!test_bit(code, state->reset_keybit)) { 683 /* 684 * Pressing any key _not_ in reset sequence cancels 685 * the reset sequence. Also cancelling the timer in 686 * case additional keys were pressed after a reset 687 * has been requested. 688 */ 689 if (value && state->reset_seq_cnt) { 690 state->reset_canceled = true; 691 del_timer(&state->keyreset_timer); 692 } 693 } else if (value == 0) { 694 /* 695 * Key release - all keys in the reset sequence need 696 * to be pressed and held for the reset timeout 697 * to hold. 698 */ 699 del_timer(&state->keyreset_timer); 700 701 if (--state->reset_seq_cnt == 0) 702 state->reset_canceled = false; 703 } else if (value == 1) { 704 /* key press, not autorepeat */ 705 if (++state->reset_seq_cnt == state->reset_seq_len && 706 !state->reset_canceled) { 707 sysrq_handle_reset_request(state); 708 } 709 } 710 } 711 712 #ifdef CONFIG_OF 713 static void sysrq_of_get_keyreset_config(void) 714 { 715 u32 key; 716 struct device_node *np; 717 struct property *prop; 718 const __be32 *p; 719 720 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 721 if (!np) { 722 pr_debug("No sysrq node found"); 723 return; 724 } 725 726 /* Reset in case a __weak definition was present */ 727 sysrq_reset_seq_len = 0; 728 729 of_property_for_each_u32(np, "keyset", prop, p, key) { 730 if (key == KEY_RESERVED || key > KEY_MAX || 731 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 732 break; 733 734 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 735 } 736 737 /* Get reset timeout if any. */ 738 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 739 } 740 #else 741 static void sysrq_of_get_keyreset_config(void) 742 { 743 } 744 #endif 745 746 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 747 { 748 struct sysrq_state *sysrq = 749 container_of(work, struct sysrq_state, reinject_work); 750 struct input_handle *handle = &sysrq->handle; 751 unsigned int alt_code = sysrq->alt_use; 752 753 if (sysrq->need_reinject) { 754 /* we do not want the assignment to be reordered */ 755 sysrq->reinjecting = true; 756 mb(); 757 758 /* Simulate press and release of Alt + SysRq */ 759 input_inject_event(handle, EV_KEY, alt_code, 1); 760 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 761 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 762 763 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 764 input_inject_event(handle, EV_KEY, alt_code, 0); 765 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 766 767 mb(); 768 sysrq->reinjecting = false; 769 } 770 } 771 772 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 773 unsigned int code, int value) 774 { 775 bool was_active = sysrq->active; 776 bool suppress; 777 778 switch (code) { 779 780 case KEY_LEFTALT: 781 case KEY_RIGHTALT: 782 if (!value) { 783 /* One of ALTs is being released */ 784 if (sysrq->active && code == sysrq->alt_use) 785 sysrq->active = false; 786 787 sysrq->alt = KEY_RESERVED; 788 789 } else if (value != 2) { 790 sysrq->alt = code; 791 sysrq->need_reinject = false; 792 } 793 break; 794 795 case KEY_SYSRQ: 796 if (value == 1 && sysrq->alt != KEY_RESERVED) { 797 sysrq->active = true; 798 sysrq->alt_use = sysrq->alt; 799 /* 800 * If nothing else will be pressed we'll need 801 * to re-inject Alt-SysRq keysroke. 802 */ 803 sysrq->need_reinject = true; 804 } 805 806 /* 807 * Pretend that sysrq was never pressed at all. This 808 * is needed to properly handle KGDB which will try 809 * to release all keys after exiting debugger. If we 810 * do not clear key bit it KGDB will end up sending 811 * release events for Alt and SysRq, potentially 812 * triggering print screen function. 813 */ 814 if (sysrq->active) 815 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 816 817 break; 818 819 default: 820 if (sysrq->active && value && value != 2) { 821 sysrq->need_reinject = false; 822 __handle_sysrq(sysrq_xlate[code], true); 823 } 824 break; 825 } 826 827 suppress = sysrq->active; 828 829 if (!sysrq->active) { 830 831 /* 832 * See if reset sequence has changed since the last time. 833 */ 834 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 835 sysrq_parse_reset_sequence(sysrq); 836 837 /* 838 * If we are not suppressing key presses keep track of 839 * keyboard state so we can release keys that have been 840 * pressed before entering SysRq mode. 841 */ 842 if (value) 843 set_bit(code, sysrq->key_down); 844 else 845 clear_bit(code, sysrq->key_down); 846 847 if (was_active) 848 schedule_work(&sysrq->reinject_work); 849 850 /* Check for reset sequence */ 851 sysrq_detect_reset_sequence(sysrq, code, value); 852 853 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 854 /* 855 * Pass on release events for keys that was pressed before 856 * entering SysRq mode. 857 */ 858 suppress = false; 859 } 860 861 return suppress; 862 } 863 864 static bool sysrq_filter(struct input_handle *handle, 865 unsigned int type, unsigned int code, int value) 866 { 867 struct sysrq_state *sysrq = handle->private; 868 bool suppress; 869 870 /* 871 * Do not filter anything if we are in the process of re-injecting 872 * Alt+SysRq combination. 873 */ 874 if (sysrq->reinjecting) 875 return false; 876 877 switch (type) { 878 879 case EV_SYN: 880 suppress = false; 881 break; 882 883 case EV_KEY: 884 suppress = sysrq_handle_keypress(sysrq, code, value); 885 break; 886 887 default: 888 suppress = sysrq->active; 889 break; 890 } 891 892 return suppress; 893 } 894 895 static int sysrq_connect(struct input_handler *handler, 896 struct input_dev *dev, 897 const struct input_device_id *id) 898 { 899 struct sysrq_state *sysrq; 900 int error; 901 902 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 903 if (!sysrq) 904 return -ENOMEM; 905 906 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 907 908 sysrq->handle.dev = dev; 909 sysrq->handle.handler = handler; 910 sysrq->handle.name = "sysrq"; 911 sysrq->handle.private = sysrq; 912 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 913 914 error = input_register_handle(&sysrq->handle); 915 if (error) { 916 pr_err("Failed to register input sysrq handler, error %d\n", 917 error); 918 goto err_free; 919 } 920 921 error = input_open_device(&sysrq->handle); 922 if (error) { 923 pr_err("Failed to open input device, error %d\n", error); 924 goto err_unregister; 925 } 926 927 return 0; 928 929 err_unregister: 930 input_unregister_handle(&sysrq->handle); 931 err_free: 932 kfree(sysrq); 933 return error; 934 } 935 936 static void sysrq_disconnect(struct input_handle *handle) 937 { 938 struct sysrq_state *sysrq = handle->private; 939 940 input_close_device(handle); 941 cancel_work_sync(&sysrq->reinject_work); 942 del_timer_sync(&sysrq->keyreset_timer); 943 input_unregister_handle(handle); 944 kfree(sysrq); 945 } 946 947 /* 948 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 949 * keyboards have SysRq key predefined and so user may add it to keymap 950 * later, but we expect all such keyboards to have left alt. 951 */ 952 static const struct input_device_id sysrq_ids[] = { 953 { 954 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 955 INPUT_DEVICE_ID_MATCH_KEYBIT, 956 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 957 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 958 }, 959 { }, 960 }; 961 962 static struct input_handler sysrq_handler = { 963 .filter = sysrq_filter, 964 .connect = sysrq_connect, 965 .disconnect = sysrq_disconnect, 966 .name = "sysrq", 967 .id_table = sysrq_ids, 968 }; 969 970 static bool sysrq_handler_registered; 971 972 static inline void sysrq_register_handler(void) 973 { 974 int error; 975 976 sysrq_of_get_keyreset_config(); 977 978 error = input_register_handler(&sysrq_handler); 979 if (error) 980 pr_err("Failed to register input handler, error %d", error); 981 else 982 sysrq_handler_registered = true; 983 } 984 985 static inline void sysrq_unregister_handler(void) 986 { 987 if (sysrq_handler_registered) { 988 input_unregister_handler(&sysrq_handler); 989 sysrq_handler_registered = false; 990 } 991 } 992 993 static int sysrq_reset_seq_param_set(const char *buffer, 994 const struct kernel_param *kp) 995 { 996 unsigned long val; 997 int error; 998 999 error = kstrtoul(buffer, 0, &val); 1000 if (error < 0) 1001 return error; 1002 1003 if (val > KEY_MAX) 1004 return -EINVAL; 1005 1006 *((unsigned short *)kp->arg) = val; 1007 sysrq_reset_seq_version++; 1008 1009 return 0; 1010 } 1011 1012 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1013 .get = param_get_ushort, 1014 .set = sysrq_reset_seq_param_set, 1015 }; 1016 1017 #define param_check_sysrq_reset_seq(name, p) \ 1018 __param_check(name, p, unsigned short) 1019 1020 /* 1021 * not really modular, but the easiest way to keep compat with existing 1022 * bootargs behaviour is to continue using module_param here. 1023 */ 1024 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1025 &sysrq_reset_seq_len, 0644); 1026 1027 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1028 1029 #else 1030 1031 static inline void sysrq_register_handler(void) 1032 { 1033 } 1034 1035 static inline void sysrq_unregister_handler(void) 1036 { 1037 } 1038 1039 #endif /* CONFIG_INPUT */ 1040 1041 int sysrq_toggle_support(int enable_mask) 1042 { 1043 bool was_enabled = sysrq_on(); 1044 1045 sysrq_enabled = enable_mask; 1046 1047 if (was_enabled != sysrq_on()) { 1048 if (sysrq_on()) 1049 sysrq_register_handler(); 1050 else 1051 sysrq_unregister_handler(); 1052 } 1053 1054 return 0; 1055 } 1056 1057 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1058 struct sysrq_key_op *remove_op_p) 1059 { 1060 int retval; 1061 1062 spin_lock(&sysrq_key_table_lock); 1063 if (__sysrq_get_key_op(key) == remove_op_p) { 1064 __sysrq_put_key_op(key, insert_op_p); 1065 retval = 0; 1066 } else { 1067 retval = -1; 1068 } 1069 spin_unlock(&sysrq_key_table_lock); 1070 1071 /* 1072 * A concurrent __handle_sysrq either got the old op or the new op. 1073 * Wait for it to go away before returning, so the code for an old 1074 * op is not freed (eg. on module unload) while it is in use. 1075 */ 1076 synchronize_rcu(); 1077 1078 return retval; 1079 } 1080 1081 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1082 { 1083 return __sysrq_swap_key_ops(key, op_p, NULL); 1084 } 1085 EXPORT_SYMBOL(register_sysrq_key); 1086 1087 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1088 { 1089 return __sysrq_swap_key_ops(key, NULL, op_p); 1090 } 1091 EXPORT_SYMBOL(unregister_sysrq_key); 1092 1093 #ifdef CONFIG_PROC_FS 1094 /* 1095 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1096 */ 1097 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1098 size_t count, loff_t *ppos) 1099 { 1100 if (count) { 1101 char c; 1102 1103 if (get_user(c, buf)) 1104 return -EFAULT; 1105 __handle_sysrq(c, false); 1106 } 1107 1108 return count; 1109 } 1110 1111 static const struct file_operations proc_sysrq_trigger_operations = { 1112 .write = write_sysrq_trigger, 1113 .llseek = noop_llseek, 1114 }; 1115 1116 static void sysrq_init_procfs(void) 1117 { 1118 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1119 &proc_sysrq_trigger_operations)) 1120 pr_err("Failed to register proc interface\n"); 1121 } 1122 1123 #else 1124 1125 static inline void sysrq_init_procfs(void) 1126 { 1127 } 1128 1129 #endif /* CONFIG_PROC_FS */ 1130 1131 static int __init sysrq_init(void) 1132 { 1133 sysrq_init_procfs(); 1134 1135 if (sysrq_on()) 1136 sysrq_register_handler(); 1137 1138 return 0; 1139 } 1140 device_initcall(sysrq_init); 1141