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 = get_irq_regs(); 250 251 if (regs) { 252 pr_info("CPU%d:\n", smp_processor_id()); 253 show_regs(regs); 254 } 255 schedule_work(&sysrq_showallcpus); 256 } 257 } 258 259 static struct sysrq_key_op sysrq_showallcpus_op = { 260 .handler = sysrq_handle_showallcpus, 261 .help_msg = "show-backtrace-all-active-cpus(l)", 262 .action_msg = "Show backtrace of all active CPUs", 263 .enable_mask = SYSRQ_ENABLE_DUMP, 264 }; 265 #endif 266 267 static void sysrq_handle_showregs(int key) 268 { 269 struct pt_regs *regs = get_irq_regs(); 270 if (regs) 271 show_regs(regs); 272 perf_event_print_debug(); 273 } 274 static struct sysrq_key_op sysrq_showregs_op = { 275 .handler = sysrq_handle_showregs, 276 .help_msg = "show-registers(p)", 277 .action_msg = "Show Regs", 278 .enable_mask = SYSRQ_ENABLE_DUMP, 279 }; 280 281 static void sysrq_handle_showstate(int key) 282 { 283 show_state(); 284 show_workqueue_state(); 285 } 286 static struct sysrq_key_op sysrq_showstate_op = { 287 .handler = sysrq_handle_showstate, 288 .help_msg = "show-task-states(t)", 289 .action_msg = "Show State", 290 .enable_mask = SYSRQ_ENABLE_DUMP, 291 }; 292 293 static void sysrq_handle_showstate_blocked(int key) 294 { 295 show_state_filter(TASK_UNINTERRUPTIBLE); 296 } 297 static struct sysrq_key_op sysrq_showstate_blocked_op = { 298 .handler = sysrq_handle_showstate_blocked, 299 .help_msg = "show-blocked-tasks(w)", 300 .action_msg = "Show Blocked State", 301 .enable_mask = SYSRQ_ENABLE_DUMP, 302 }; 303 304 #ifdef CONFIG_TRACING 305 #include <linux/ftrace.h> 306 307 static void sysrq_ftrace_dump(int key) 308 { 309 ftrace_dump(DUMP_ALL); 310 } 311 static struct sysrq_key_op sysrq_ftrace_dump_op = { 312 .handler = sysrq_ftrace_dump, 313 .help_msg = "dump-ftrace-buffer(z)", 314 .action_msg = "Dump ftrace buffer", 315 .enable_mask = SYSRQ_ENABLE_DUMP, 316 }; 317 #else 318 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 319 #endif 320 321 static void sysrq_handle_showmem(int key) 322 { 323 show_mem(0, NULL); 324 } 325 static struct sysrq_key_op sysrq_showmem_op = { 326 .handler = sysrq_handle_showmem, 327 .help_msg = "show-memory-usage(m)", 328 .action_msg = "Show Memory", 329 .enable_mask = SYSRQ_ENABLE_DUMP, 330 }; 331 332 /* 333 * Signal sysrq helper function. Sends a signal to all user processes. 334 */ 335 static void send_sig_all(int sig) 336 { 337 struct task_struct *p; 338 339 read_lock(&tasklist_lock); 340 for_each_process(p) { 341 if (p->flags & PF_KTHREAD) 342 continue; 343 if (is_global_init(p)) 344 continue; 345 346 do_send_sig_info(sig, SEND_SIG_FORCED, p, true); 347 } 348 read_unlock(&tasklist_lock); 349 } 350 351 static void sysrq_handle_term(int key) 352 { 353 send_sig_all(SIGTERM); 354 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 355 } 356 static struct sysrq_key_op sysrq_term_op = { 357 .handler = sysrq_handle_term, 358 .help_msg = "terminate-all-tasks(e)", 359 .action_msg = "Terminate All Tasks", 360 .enable_mask = SYSRQ_ENABLE_SIGNAL, 361 }; 362 363 static void moom_callback(struct work_struct *ignored) 364 { 365 const gfp_t gfp_mask = GFP_KERNEL; 366 struct oom_control oc = { 367 .zonelist = node_zonelist(first_memory_node, gfp_mask), 368 .nodemask = NULL, 369 .memcg = NULL, 370 .gfp_mask = gfp_mask, 371 .order = -1, 372 }; 373 374 mutex_lock(&oom_lock); 375 if (!out_of_memory(&oc)) 376 pr_info("OOM request ignored. No task eligible\n"); 377 mutex_unlock(&oom_lock); 378 } 379 380 static DECLARE_WORK(moom_work, moom_callback); 381 382 static void sysrq_handle_moom(int key) 383 { 384 schedule_work(&moom_work); 385 } 386 static struct sysrq_key_op sysrq_moom_op = { 387 .handler = sysrq_handle_moom, 388 .help_msg = "memory-full-oom-kill(f)", 389 .action_msg = "Manual OOM execution", 390 .enable_mask = SYSRQ_ENABLE_SIGNAL, 391 }; 392 393 #ifdef CONFIG_BLOCK 394 static void sysrq_handle_thaw(int key) 395 { 396 emergency_thaw_all(); 397 } 398 static struct sysrq_key_op sysrq_thaw_op = { 399 .handler = sysrq_handle_thaw, 400 .help_msg = "thaw-filesystems(j)", 401 .action_msg = "Emergency Thaw of all frozen filesystems", 402 .enable_mask = SYSRQ_ENABLE_SIGNAL, 403 }; 404 #endif 405 406 static void sysrq_handle_kill(int key) 407 { 408 send_sig_all(SIGKILL); 409 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 410 } 411 static struct sysrq_key_op sysrq_kill_op = { 412 .handler = sysrq_handle_kill, 413 .help_msg = "kill-all-tasks(i)", 414 .action_msg = "Kill All Tasks", 415 .enable_mask = SYSRQ_ENABLE_SIGNAL, 416 }; 417 418 static void sysrq_handle_unrt(int key) 419 { 420 normalize_rt_tasks(); 421 } 422 static struct sysrq_key_op sysrq_unrt_op = { 423 .handler = sysrq_handle_unrt, 424 .help_msg = "nice-all-RT-tasks(n)", 425 .action_msg = "Nice All RT Tasks", 426 .enable_mask = SYSRQ_ENABLE_RTNICE, 427 }; 428 429 /* Key Operations table and lock */ 430 static DEFINE_SPINLOCK(sysrq_key_table_lock); 431 432 static struct sysrq_key_op *sysrq_key_table[36] = { 433 &sysrq_loglevel_op, /* 0 */ 434 &sysrq_loglevel_op, /* 1 */ 435 &sysrq_loglevel_op, /* 2 */ 436 &sysrq_loglevel_op, /* 3 */ 437 &sysrq_loglevel_op, /* 4 */ 438 &sysrq_loglevel_op, /* 5 */ 439 &sysrq_loglevel_op, /* 6 */ 440 &sysrq_loglevel_op, /* 7 */ 441 &sysrq_loglevel_op, /* 8 */ 442 &sysrq_loglevel_op, /* 9 */ 443 444 /* 445 * a: Don't use for system provided sysrqs, it is handled specially on 446 * sparc and will never arrive. 447 */ 448 NULL, /* a */ 449 &sysrq_reboot_op, /* b */ 450 &sysrq_crash_op, /* c */ 451 &sysrq_showlocks_op, /* d */ 452 &sysrq_term_op, /* e */ 453 &sysrq_moom_op, /* f */ 454 /* g: May be registered for the kernel debugger */ 455 NULL, /* g */ 456 NULL, /* h - reserved for help */ 457 &sysrq_kill_op, /* i */ 458 #ifdef CONFIG_BLOCK 459 &sysrq_thaw_op, /* j */ 460 #else 461 NULL, /* j */ 462 #endif 463 &sysrq_SAK_op, /* k */ 464 #ifdef CONFIG_SMP 465 &sysrq_showallcpus_op, /* l */ 466 #else 467 NULL, /* l */ 468 #endif 469 &sysrq_showmem_op, /* m */ 470 &sysrq_unrt_op, /* n */ 471 /* o: This will often be registered as 'Off' at init time */ 472 NULL, /* o */ 473 &sysrq_showregs_op, /* p */ 474 &sysrq_show_timers_op, /* q */ 475 &sysrq_unraw_op, /* r */ 476 &sysrq_sync_op, /* s */ 477 &sysrq_showstate_op, /* t */ 478 &sysrq_mountro_op, /* u */ 479 /* v: May be registered for frame buffer console restore */ 480 NULL, /* v */ 481 &sysrq_showstate_blocked_op, /* w */ 482 /* x: May be registered on mips for TLB dump */ 483 /* x: May be registered on ppc/powerpc for xmon */ 484 /* x: May be registered on sparc64 for global PMU dump */ 485 NULL, /* x */ 486 /* y: May be registered on sparc64 for global register dump */ 487 NULL, /* y */ 488 &sysrq_ftrace_dump_op, /* z */ 489 }; 490 491 /* key2index calculation, -1 on invalid index */ 492 static int sysrq_key_table_key2index(int key) 493 { 494 int retval; 495 496 if ((key >= '0') && (key <= '9')) 497 retval = key - '0'; 498 else if ((key >= 'a') && (key <= 'z')) 499 retval = key + 10 - 'a'; 500 else 501 retval = -1; 502 return retval; 503 } 504 505 /* 506 * get and put functions for the table, exposed to modules. 507 */ 508 struct sysrq_key_op *__sysrq_get_key_op(int key) 509 { 510 struct sysrq_key_op *op_p = NULL; 511 int i; 512 513 i = sysrq_key_table_key2index(key); 514 if (i != -1) 515 op_p = sysrq_key_table[i]; 516 517 return op_p; 518 } 519 520 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 521 { 522 int i = sysrq_key_table_key2index(key); 523 524 if (i != -1) 525 sysrq_key_table[i] = op_p; 526 } 527 528 void __handle_sysrq(int key, bool check_mask) 529 { 530 struct sysrq_key_op *op_p; 531 int orig_log_level; 532 int i; 533 534 rcu_sysrq_start(); 535 rcu_read_lock(); 536 /* 537 * Raise the apparent loglevel to maximum so that the sysrq header 538 * is shown to provide the user with positive feedback. We do not 539 * simply emit this at KERN_EMERG as that would change message 540 * routing in the consumers of /proc/kmsg. 541 */ 542 orig_log_level = console_loglevel; 543 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 544 pr_info("SysRq : "); 545 546 op_p = __sysrq_get_key_op(key); 547 if (op_p) { 548 /* 549 * Should we check for enabled operations (/proc/sysrq-trigger 550 * should not) and is the invoked operation enabled? 551 */ 552 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 553 pr_cont("%s\n", op_p->action_msg); 554 console_loglevel = orig_log_level; 555 op_p->handler(key); 556 } else { 557 pr_cont("This sysrq operation is disabled.\n"); 558 } 559 } else { 560 pr_cont("HELP : "); 561 /* Only print the help msg once per handler */ 562 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 563 if (sysrq_key_table[i]) { 564 int j; 565 566 for (j = 0; sysrq_key_table[i] != 567 sysrq_key_table[j]; j++) 568 ; 569 if (j != i) 570 continue; 571 pr_cont("%s ", sysrq_key_table[i]->help_msg); 572 } 573 } 574 pr_cont("\n"); 575 console_loglevel = orig_log_level; 576 } 577 rcu_read_unlock(); 578 rcu_sysrq_end(); 579 } 580 581 void handle_sysrq(int key) 582 { 583 if (sysrq_on()) 584 __handle_sysrq(key, true); 585 } 586 EXPORT_SYMBOL(handle_sysrq); 587 588 #ifdef CONFIG_INPUT 589 static int sysrq_reset_downtime_ms; 590 591 /* Simple translation table for the SysRq keys */ 592 static const unsigned char sysrq_xlate[KEY_CNT] = 593 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 594 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 595 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 596 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 597 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 598 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 599 "\r\000/"; /* 0x60 - 0x6f */ 600 601 struct sysrq_state { 602 struct input_handle handle; 603 struct work_struct reinject_work; 604 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 605 unsigned int alt; 606 unsigned int alt_use; 607 bool active; 608 bool need_reinject; 609 bool reinjecting; 610 611 /* reset sequence handling */ 612 bool reset_canceled; 613 bool reset_requested; 614 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 615 int reset_seq_len; 616 int reset_seq_cnt; 617 int reset_seq_version; 618 struct timer_list keyreset_timer; 619 }; 620 621 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 622 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 623 static unsigned int sysrq_reset_seq_len; 624 static unsigned int sysrq_reset_seq_version = 1; 625 626 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 627 { 628 int i; 629 unsigned short key; 630 631 state->reset_seq_cnt = 0; 632 633 for (i = 0; i < sysrq_reset_seq_len; i++) { 634 key = sysrq_reset_seq[i]; 635 636 if (key == KEY_RESERVED || key > KEY_MAX) 637 break; 638 639 __set_bit(key, state->reset_keybit); 640 state->reset_seq_len++; 641 642 if (test_bit(key, state->key_down)) 643 state->reset_seq_cnt++; 644 } 645 646 /* Disable reset until old keys are not released */ 647 state->reset_canceled = state->reset_seq_cnt != 0; 648 649 state->reset_seq_version = sysrq_reset_seq_version; 650 } 651 652 static void sysrq_do_reset(unsigned long _state) 653 { 654 struct sysrq_state *state = (struct sysrq_state *) _state; 655 656 state->reset_requested = true; 657 658 sys_sync(); 659 kernel_restart(NULL); 660 } 661 662 static void sysrq_handle_reset_request(struct sysrq_state *state) 663 { 664 if (state->reset_requested) 665 __handle_sysrq(sysrq_xlate[KEY_B], false); 666 667 if (sysrq_reset_downtime_ms) 668 mod_timer(&state->keyreset_timer, 669 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 670 else 671 sysrq_do_reset((unsigned long)state); 672 } 673 674 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 675 unsigned int code, int value) 676 { 677 if (!test_bit(code, state->reset_keybit)) { 678 /* 679 * Pressing any key _not_ in reset sequence cancels 680 * the reset sequence. Also cancelling the timer in 681 * case additional keys were pressed after a reset 682 * has been requested. 683 */ 684 if (value && state->reset_seq_cnt) { 685 state->reset_canceled = true; 686 del_timer(&state->keyreset_timer); 687 } 688 } else if (value == 0) { 689 /* 690 * Key release - all keys in the reset sequence need 691 * to be pressed and held for the reset timeout 692 * to hold. 693 */ 694 del_timer(&state->keyreset_timer); 695 696 if (--state->reset_seq_cnt == 0) 697 state->reset_canceled = false; 698 } else if (value == 1) { 699 /* key press, not autorepeat */ 700 if (++state->reset_seq_cnt == state->reset_seq_len && 701 !state->reset_canceled) { 702 sysrq_handle_reset_request(state); 703 } 704 } 705 } 706 707 #ifdef CONFIG_OF 708 static void sysrq_of_get_keyreset_config(void) 709 { 710 u32 key; 711 struct device_node *np; 712 struct property *prop; 713 const __be32 *p; 714 715 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 716 if (!np) { 717 pr_debug("No sysrq node found"); 718 return; 719 } 720 721 /* Reset in case a __weak definition was present */ 722 sysrq_reset_seq_len = 0; 723 724 of_property_for_each_u32(np, "keyset", prop, p, key) { 725 if (key == KEY_RESERVED || key > KEY_MAX || 726 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 727 break; 728 729 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 730 } 731 732 /* Get reset timeout if any. */ 733 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 734 } 735 #else 736 static void sysrq_of_get_keyreset_config(void) 737 { 738 } 739 #endif 740 741 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 742 { 743 struct sysrq_state *sysrq = 744 container_of(work, struct sysrq_state, reinject_work); 745 struct input_handle *handle = &sysrq->handle; 746 unsigned int alt_code = sysrq->alt_use; 747 748 if (sysrq->need_reinject) { 749 /* we do not want the assignment to be reordered */ 750 sysrq->reinjecting = true; 751 mb(); 752 753 /* Simulate press and release of Alt + SysRq */ 754 input_inject_event(handle, EV_KEY, alt_code, 1); 755 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 756 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 757 758 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 759 input_inject_event(handle, EV_KEY, alt_code, 0); 760 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 761 762 mb(); 763 sysrq->reinjecting = false; 764 } 765 } 766 767 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 768 unsigned int code, int value) 769 { 770 bool was_active = sysrq->active; 771 bool suppress; 772 773 switch (code) { 774 775 case KEY_LEFTALT: 776 case KEY_RIGHTALT: 777 if (!value) { 778 /* One of ALTs is being released */ 779 if (sysrq->active && code == sysrq->alt_use) 780 sysrq->active = false; 781 782 sysrq->alt = KEY_RESERVED; 783 784 } else if (value != 2) { 785 sysrq->alt = code; 786 sysrq->need_reinject = false; 787 } 788 break; 789 790 case KEY_SYSRQ: 791 if (value == 1 && sysrq->alt != KEY_RESERVED) { 792 sysrq->active = true; 793 sysrq->alt_use = sysrq->alt; 794 /* 795 * If nothing else will be pressed we'll need 796 * to re-inject Alt-SysRq keysroke. 797 */ 798 sysrq->need_reinject = true; 799 } 800 801 /* 802 * Pretend that sysrq was never pressed at all. This 803 * is needed to properly handle KGDB which will try 804 * to release all keys after exiting debugger. If we 805 * do not clear key bit it KGDB will end up sending 806 * release events for Alt and SysRq, potentially 807 * triggering print screen function. 808 */ 809 if (sysrq->active) 810 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 811 812 break; 813 814 default: 815 if (sysrq->active && value && value != 2) { 816 sysrq->need_reinject = false; 817 __handle_sysrq(sysrq_xlate[code], true); 818 } 819 break; 820 } 821 822 suppress = sysrq->active; 823 824 if (!sysrq->active) { 825 826 /* 827 * See if reset sequence has changed since the last time. 828 */ 829 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 830 sysrq_parse_reset_sequence(sysrq); 831 832 /* 833 * If we are not suppressing key presses keep track of 834 * keyboard state so we can release keys that have been 835 * pressed before entering SysRq mode. 836 */ 837 if (value) 838 set_bit(code, sysrq->key_down); 839 else 840 clear_bit(code, sysrq->key_down); 841 842 if (was_active) 843 schedule_work(&sysrq->reinject_work); 844 845 /* Check for reset sequence */ 846 sysrq_detect_reset_sequence(sysrq, code, value); 847 848 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 849 /* 850 * Pass on release events for keys that was pressed before 851 * entering SysRq mode. 852 */ 853 suppress = false; 854 } 855 856 return suppress; 857 } 858 859 static bool sysrq_filter(struct input_handle *handle, 860 unsigned int type, unsigned int code, int value) 861 { 862 struct sysrq_state *sysrq = handle->private; 863 bool suppress; 864 865 /* 866 * Do not filter anything if we are in the process of re-injecting 867 * Alt+SysRq combination. 868 */ 869 if (sysrq->reinjecting) 870 return false; 871 872 switch (type) { 873 874 case EV_SYN: 875 suppress = false; 876 break; 877 878 case EV_KEY: 879 suppress = sysrq_handle_keypress(sysrq, code, value); 880 break; 881 882 default: 883 suppress = sysrq->active; 884 break; 885 } 886 887 return suppress; 888 } 889 890 static int sysrq_connect(struct input_handler *handler, 891 struct input_dev *dev, 892 const struct input_device_id *id) 893 { 894 struct sysrq_state *sysrq; 895 int error; 896 897 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 898 if (!sysrq) 899 return -ENOMEM; 900 901 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 902 903 sysrq->handle.dev = dev; 904 sysrq->handle.handler = handler; 905 sysrq->handle.name = "sysrq"; 906 sysrq->handle.private = sysrq; 907 setup_timer(&sysrq->keyreset_timer, 908 sysrq_do_reset, (unsigned long)sysrq); 909 910 error = input_register_handle(&sysrq->handle); 911 if (error) { 912 pr_err("Failed to register input sysrq handler, error %d\n", 913 error); 914 goto err_free; 915 } 916 917 error = input_open_device(&sysrq->handle); 918 if (error) { 919 pr_err("Failed to open input device, error %d\n", error); 920 goto err_unregister; 921 } 922 923 return 0; 924 925 err_unregister: 926 input_unregister_handle(&sysrq->handle); 927 err_free: 928 kfree(sysrq); 929 return error; 930 } 931 932 static void sysrq_disconnect(struct input_handle *handle) 933 { 934 struct sysrq_state *sysrq = handle->private; 935 936 input_close_device(handle); 937 cancel_work_sync(&sysrq->reinject_work); 938 del_timer_sync(&sysrq->keyreset_timer); 939 input_unregister_handle(handle); 940 kfree(sysrq); 941 } 942 943 /* 944 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 945 * keyboards have SysRq key predefined and so user may add it to keymap 946 * later, but we expect all such keyboards to have left alt. 947 */ 948 static const struct input_device_id sysrq_ids[] = { 949 { 950 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 951 INPUT_DEVICE_ID_MATCH_KEYBIT, 952 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 953 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 954 }, 955 { }, 956 }; 957 958 static struct input_handler sysrq_handler = { 959 .filter = sysrq_filter, 960 .connect = sysrq_connect, 961 .disconnect = sysrq_disconnect, 962 .name = "sysrq", 963 .id_table = sysrq_ids, 964 }; 965 966 static bool sysrq_handler_registered; 967 968 static inline void sysrq_register_handler(void) 969 { 970 int error; 971 972 sysrq_of_get_keyreset_config(); 973 974 error = input_register_handler(&sysrq_handler); 975 if (error) 976 pr_err("Failed to register input handler, error %d", error); 977 else 978 sysrq_handler_registered = true; 979 } 980 981 static inline void sysrq_unregister_handler(void) 982 { 983 if (sysrq_handler_registered) { 984 input_unregister_handler(&sysrq_handler); 985 sysrq_handler_registered = false; 986 } 987 } 988 989 static int sysrq_reset_seq_param_set(const char *buffer, 990 const struct kernel_param *kp) 991 { 992 unsigned long val; 993 int error; 994 995 error = kstrtoul(buffer, 0, &val); 996 if (error < 0) 997 return error; 998 999 if (val > KEY_MAX) 1000 return -EINVAL; 1001 1002 *((unsigned short *)kp->arg) = val; 1003 sysrq_reset_seq_version++; 1004 1005 return 0; 1006 } 1007 1008 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1009 .get = param_get_ushort, 1010 .set = sysrq_reset_seq_param_set, 1011 }; 1012 1013 #define param_check_sysrq_reset_seq(name, p) \ 1014 __param_check(name, p, unsigned short) 1015 1016 /* 1017 * not really modular, but the easiest way to keep compat with existing 1018 * bootargs behaviour is to continue using module_param here. 1019 */ 1020 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1021 &sysrq_reset_seq_len, 0644); 1022 1023 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1024 1025 #else 1026 1027 static inline void sysrq_register_handler(void) 1028 { 1029 } 1030 1031 static inline void sysrq_unregister_handler(void) 1032 { 1033 } 1034 1035 #endif /* CONFIG_INPUT */ 1036 1037 int sysrq_toggle_support(int enable_mask) 1038 { 1039 bool was_enabled = sysrq_on(); 1040 1041 sysrq_enabled = enable_mask; 1042 1043 if (was_enabled != sysrq_on()) { 1044 if (sysrq_on()) 1045 sysrq_register_handler(); 1046 else 1047 sysrq_unregister_handler(); 1048 } 1049 1050 return 0; 1051 } 1052 1053 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1054 struct sysrq_key_op *remove_op_p) 1055 { 1056 int retval; 1057 1058 spin_lock(&sysrq_key_table_lock); 1059 if (__sysrq_get_key_op(key) == remove_op_p) { 1060 __sysrq_put_key_op(key, insert_op_p); 1061 retval = 0; 1062 } else { 1063 retval = -1; 1064 } 1065 spin_unlock(&sysrq_key_table_lock); 1066 1067 /* 1068 * A concurrent __handle_sysrq either got the old op or the new op. 1069 * Wait for it to go away before returning, so the code for an old 1070 * op is not freed (eg. on module unload) while it is in use. 1071 */ 1072 synchronize_rcu(); 1073 1074 return retval; 1075 } 1076 1077 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1078 { 1079 return __sysrq_swap_key_ops(key, op_p, NULL); 1080 } 1081 EXPORT_SYMBOL(register_sysrq_key); 1082 1083 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1084 { 1085 return __sysrq_swap_key_ops(key, NULL, op_p); 1086 } 1087 EXPORT_SYMBOL(unregister_sysrq_key); 1088 1089 #ifdef CONFIG_PROC_FS 1090 /* 1091 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1092 */ 1093 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1094 size_t count, loff_t *ppos) 1095 { 1096 if (count) { 1097 char c; 1098 1099 if (get_user(c, buf)) 1100 return -EFAULT; 1101 __handle_sysrq(c, false); 1102 } 1103 1104 return count; 1105 } 1106 1107 static const struct file_operations proc_sysrq_trigger_operations = { 1108 .write = write_sysrq_trigger, 1109 .llseek = noop_llseek, 1110 }; 1111 1112 static void sysrq_init_procfs(void) 1113 { 1114 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1115 &proc_sysrq_trigger_operations)) 1116 pr_err("Failed to register proc interface\n"); 1117 } 1118 1119 #else 1120 1121 static inline void sysrq_init_procfs(void) 1122 { 1123 } 1124 1125 #endif /* CONFIG_PROC_FS */ 1126 1127 static int __init sysrq_init(void) 1128 { 1129 sysrq_init_procfs(); 1130 1131 if (sysrq_on()) 1132 sysrq_register_handler(); 1133 1134 return 0; 1135 } 1136 device_initcall(sysrq_init); 1137