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 * sysrq_mask - Getter for sysrq_enabled mask. 68 * 69 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise. 70 */ 71 int sysrq_mask(void) 72 { 73 if (sysrq_always_enabled) 74 return 1; 75 return sysrq_enabled; 76 } 77 78 /* 79 * A value of 1 means 'all', other nonzero values are an op mask: 80 */ 81 static bool sysrq_on_mask(int mask) 82 { 83 return sysrq_always_enabled || 84 sysrq_enabled == 1 || 85 (sysrq_enabled & mask); 86 } 87 88 static int __init sysrq_always_enabled_setup(char *str) 89 { 90 sysrq_always_enabled = true; 91 pr_info("sysrq always enabled.\n"); 92 93 return 1; 94 } 95 96 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 97 98 99 static void sysrq_handle_loglevel(int key) 100 { 101 int i; 102 103 i = key - '0'; 104 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 105 pr_info("Loglevel set to %d\n", i); 106 console_loglevel = i; 107 } 108 static struct sysrq_key_op sysrq_loglevel_op = { 109 .handler = sysrq_handle_loglevel, 110 .help_msg = "loglevel(0-9)", 111 .action_msg = "Changing Loglevel", 112 .enable_mask = SYSRQ_ENABLE_LOG, 113 }; 114 115 #ifdef CONFIG_VT 116 static void sysrq_handle_SAK(int key) 117 { 118 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 119 schedule_work(SAK_work); 120 } 121 static struct sysrq_key_op sysrq_SAK_op = { 122 .handler = sysrq_handle_SAK, 123 .help_msg = "sak(k)", 124 .action_msg = "SAK", 125 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 126 }; 127 #else 128 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL) 129 #endif 130 131 #ifdef CONFIG_VT 132 static void sysrq_handle_unraw(int key) 133 { 134 vt_reset_unicode(fg_console); 135 } 136 137 static struct sysrq_key_op sysrq_unraw_op = { 138 .handler = sysrq_handle_unraw, 139 .help_msg = "unraw(r)", 140 .action_msg = "Keyboard mode set to system default", 141 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 142 }; 143 #else 144 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL) 145 #endif /* CONFIG_VT */ 146 147 static void sysrq_handle_crash(int key) 148 { 149 /* release the RCU read lock before crashing */ 150 rcu_read_unlock(); 151 152 panic("sysrq triggered crash\n"); 153 } 154 static struct sysrq_key_op sysrq_crash_op = { 155 .handler = sysrq_handle_crash, 156 .help_msg = "crash(c)", 157 .action_msg = "Trigger a crash", 158 .enable_mask = SYSRQ_ENABLE_DUMP, 159 }; 160 161 static void sysrq_handle_reboot(int key) 162 { 163 lockdep_off(); 164 local_irq_enable(); 165 emergency_restart(); 166 } 167 static struct sysrq_key_op sysrq_reboot_op = { 168 .handler = sysrq_handle_reboot, 169 .help_msg = "reboot(b)", 170 .action_msg = "Resetting", 171 .enable_mask = SYSRQ_ENABLE_BOOT, 172 }; 173 174 static void sysrq_handle_sync(int key) 175 { 176 emergency_sync(); 177 } 178 static struct sysrq_key_op sysrq_sync_op = { 179 .handler = sysrq_handle_sync, 180 .help_msg = "sync(s)", 181 .action_msg = "Emergency Sync", 182 .enable_mask = SYSRQ_ENABLE_SYNC, 183 }; 184 185 static void sysrq_handle_show_timers(int key) 186 { 187 sysrq_timer_list_show(); 188 } 189 190 static struct sysrq_key_op sysrq_show_timers_op = { 191 .handler = sysrq_handle_show_timers, 192 .help_msg = "show-all-timers(q)", 193 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 194 }; 195 196 static void sysrq_handle_mountro(int key) 197 { 198 emergency_remount(); 199 } 200 static struct sysrq_key_op sysrq_mountro_op = { 201 .handler = sysrq_handle_mountro, 202 .help_msg = "unmount(u)", 203 .action_msg = "Emergency Remount R/O", 204 .enable_mask = SYSRQ_ENABLE_REMOUNT, 205 }; 206 207 #ifdef CONFIG_LOCKDEP 208 static void sysrq_handle_showlocks(int key) 209 { 210 debug_show_all_locks(); 211 } 212 213 static struct sysrq_key_op sysrq_showlocks_op = { 214 .handler = sysrq_handle_showlocks, 215 .help_msg = "show-all-locks(d)", 216 .action_msg = "Show Locks Held", 217 }; 218 #else 219 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 220 #endif 221 222 #ifdef CONFIG_SMP 223 static DEFINE_RAW_SPINLOCK(show_lock); 224 225 static void showacpu(void *dummy) 226 { 227 unsigned long flags; 228 229 /* Idle CPUs have no interesting backtrace. */ 230 if (idle_cpu(smp_processor_id())) 231 return; 232 233 raw_spin_lock_irqsave(&show_lock, flags); 234 pr_info("CPU%d:\n", smp_processor_id()); 235 show_stack(NULL, NULL); 236 raw_spin_unlock_irqrestore(&show_lock, flags); 237 } 238 239 static void sysrq_showregs_othercpus(struct work_struct *dummy) 240 { 241 smp_call_function(showacpu, NULL, 0); 242 } 243 244 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 245 246 static void sysrq_handle_showallcpus(int key) 247 { 248 /* 249 * Fall back to the workqueue based printing if the 250 * backtrace printing did not succeed or the 251 * architecture has no support for it: 252 */ 253 if (!trigger_all_cpu_backtrace()) { 254 struct pt_regs *regs = NULL; 255 256 if (in_irq()) 257 regs = get_irq_regs(); 258 if (regs) { 259 pr_info("CPU%d:\n", smp_processor_id()); 260 show_regs(regs); 261 } 262 schedule_work(&sysrq_showallcpus); 263 } 264 } 265 266 static struct sysrq_key_op sysrq_showallcpus_op = { 267 .handler = sysrq_handle_showallcpus, 268 .help_msg = "show-backtrace-all-active-cpus(l)", 269 .action_msg = "Show backtrace of all active CPUs", 270 .enable_mask = SYSRQ_ENABLE_DUMP, 271 }; 272 #endif 273 274 static void sysrq_handle_showregs(int key) 275 { 276 struct pt_regs *regs = NULL; 277 278 if (in_irq()) 279 regs = get_irq_regs(); 280 if (regs) 281 show_regs(regs); 282 perf_event_print_debug(); 283 } 284 static struct sysrq_key_op sysrq_showregs_op = { 285 .handler = sysrq_handle_showregs, 286 .help_msg = "show-registers(p)", 287 .action_msg = "Show Regs", 288 .enable_mask = SYSRQ_ENABLE_DUMP, 289 }; 290 291 static void sysrq_handle_showstate(int key) 292 { 293 show_state(); 294 show_workqueue_state(); 295 } 296 static struct sysrq_key_op sysrq_showstate_op = { 297 .handler = sysrq_handle_showstate, 298 .help_msg = "show-task-states(t)", 299 .action_msg = "Show State", 300 .enable_mask = SYSRQ_ENABLE_DUMP, 301 }; 302 303 static void sysrq_handle_showstate_blocked(int key) 304 { 305 show_state_filter(TASK_UNINTERRUPTIBLE); 306 } 307 static struct sysrq_key_op sysrq_showstate_blocked_op = { 308 .handler = sysrq_handle_showstate_blocked, 309 .help_msg = "show-blocked-tasks(w)", 310 .action_msg = "Show Blocked State", 311 .enable_mask = SYSRQ_ENABLE_DUMP, 312 }; 313 314 #ifdef CONFIG_TRACING 315 #include <linux/ftrace.h> 316 317 static void sysrq_ftrace_dump(int key) 318 { 319 ftrace_dump(DUMP_ALL); 320 } 321 static struct sysrq_key_op sysrq_ftrace_dump_op = { 322 .handler = sysrq_ftrace_dump, 323 .help_msg = "dump-ftrace-buffer(z)", 324 .action_msg = "Dump ftrace buffer", 325 .enable_mask = SYSRQ_ENABLE_DUMP, 326 }; 327 #else 328 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 329 #endif 330 331 static void sysrq_handle_showmem(int key) 332 { 333 show_mem(0, NULL); 334 } 335 static struct sysrq_key_op sysrq_showmem_op = { 336 .handler = sysrq_handle_showmem, 337 .help_msg = "show-memory-usage(m)", 338 .action_msg = "Show Memory", 339 .enable_mask = SYSRQ_ENABLE_DUMP, 340 }; 341 342 /* 343 * Signal sysrq helper function. Sends a signal to all user processes. 344 */ 345 static void send_sig_all(int sig) 346 { 347 struct task_struct *p; 348 349 read_lock(&tasklist_lock); 350 for_each_process(p) { 351 if (p->flags & PF_KTHREAD) 352 continue; 353 if (is_global_init(p)) 354 continue; 355 356 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX); 357 } 358 read_unlock(&tasklist_lock); 359 } 360 361 static void sysrq_handle_term(int key) 362 { 363 send_sig_all(SIGTERM); 364 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 365 } 366 static struct sysrq_key_op sysrq_term_op = { 367 .handler = sysrq_handle_term, 368 .help_msg = "terminate-all-tasks(e)", 369 .action_msg = "Terminate All Tasks", 370 .enable_mask = SYSRQ_ENABLE_SIGNAL, 371 }; 372 373 static void moom_callback(struct work_struct *ignored) 374 { 375 const gfp_t gfp_mask = GFP_KERNEL; 376 struct oom_control oc = { 377 .zonelist = node_zonelist(first_memory_node, gfp_mask), 378 .nodemask = NULL, 379 .memcg = NULL, 380 .gfp_mask = gfp_mask, 381 .order = -1, 382 }; 383 384 mutex_lock(&oom_lock); 385 if (!out_of_memory(&oc)) 386 pr_info("OOM request ignored. No task eligible\n"); 387 mutex_unlock(&oom_lock); 388 } 389 390 static DECLARE_WORK(moom_work, moom_callback); 391 392 static void sysrq_handle_moom(int key) 393 { 394 schedule_work(&moom_work); 395 } 396 static struct sysrq_key_op sysrq_moom_op = { 397 .handler = sysrq_handle_moom, 398 .help_msg = "memory-full-oom-kill(f)", 399 .action_msg = "Manual OOM execution", 400 .enable_mask = SYSRQ_ENABLE_SIGNAL, 401 }; 402 403 #ifdef CONFIG_BLOCK 404 static void sysrq_handle_thaw(int key) 405 { 406 emergency_thaw_all(); 407 } 408 static struct sysrq_key_op sysrq_thaw_op = { 409 .handler = sysrq_handle_thaw, 410 .help_msg = "thaw-filesystems(j)", 411 .action_msg = "Emergency Thaw of all frozen filesystems", 412 .enable_mask = SYSRQ_ENABLE_SIGNAL, 413 }; 414 #endif 415 416 static void sysrq_handle_kill(int key) 417 { 418 send_sig_all(SIGKILL); 419 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 420 } 421 static struct sysrq_key_op sysrq_kill_op = { 422 .handler = sysrq_handle_kill, 423 .help_msg = "kill-all-tasks(i)", 424 .action_msg = "Kill All Tasks", 425 .enable_mask = SYSRQ_ENABLE_SIGNAL, 426 }; 427 428 static void sysrq_handle_unrt(int key) 429 { 430 normalize_rt_tasks(); 431 } 432 static struct sysrq_key_op sysrq_unrt_op = { 433 .handler = sysrq_handle_unrt, 434 .help_msg = "nice-all-RT-tasks(n)", 435 .action_msg = "Nice All RT Tasks", 436 .enable_mask = SYSRQ_ENABLE_RTNICE, 437 }; 438 439 /* Key Operations table and lock */ 440 static DEFINE_SPINLOCK(sysrq_key_table_lock); 441 442 static struct sysrq_key_op *sysrq_key_table[36] = { 443 &sysrq_loglevel_op, /* 0 */ 444 &sysrq_loglevel_op, /* 1 */ 445 &sysrq_loglevel_op, /* 2 */ 446 &sysrq_loglevel_op, /* 3 */ 447 &sysrq_loglevel_op, /* 4 */ 448 &sysrq_loglevel_op, /* 5 */ 449 &sysrq_loglevel_op, /* 6 */ 450 &sysrq_loglevel_op, /* 7 */ 451 &sysrq_loglevel_op, /* 8 */ 452 &sysrq_loglevel_op, /* 9 */ 453 454 /* 455 * a: Don't use for system provided sysrqs, it is handled specially on 456 * sparc and will never arrive. 457 */ 458 NULL, /* a */ 459 &sysrq_reboot_op, /* b */ 460 &sysrq_crash_op, /* c */ 461 &sysrq_showlocks_op, /* d */ 462 &sysrq_term_op, /* e */ 463 &sysrq_moom_op, /* f */ 464 /* g: May be registered for the kernel debugger */ 465 NULL, /* g */ 466 NULL, /* h - reserved for help */ 467 &sysrq_kill_op, /* i */ 468 #ifdef CONFIG_BLOCK 469 &sysrq_thaw_op, /* j */ 470 #else 471 NULL, /* j */ 472 #endif 473 &sysrq_SAK_op, /* k */ 474 #ifdef CONFIG_SMP 475 &sysrq_showallcpus_op, /* l */ 476 #else 477 NULL, /* l */ 478 #endif 479 &sysrq_showmem_op, /* m */ 480 &sysrq_unrt_op, /* n */ 481 /* o: This will often be registered as 'Off' at init time */ 482 NULL, /* o */ 483 &sysrq_showregs_op, /* p */ 484 &sysrq_show_timers_op, /* q */ 485 &sysrq_unraw_op, /* r */ 486 &sysrq_sync_op, /* s */ 487 &sysrq_showstate_op, /* t */ 488 &sysrq_mountro_op, /* u */ 489 /* v: May be registered for frame buffer console restore */ 490 NULL, /* v */ 491 &sysrq_showstate_blocked_op, /* w */ 492 /* x: May be registered on mips for TLB dump */ 493 /* x: May be registered on ppc/powerpc for xmon */ 494 /* x: May be registered on sparc64 for global PMU dump */ 495 NULL, /* x */ 496 /* y: May be registered on sparc64 for global register dump */ 497 NULL, /* y */ 498 &sysrq_ftrace_dump_op, /* z */ 499 }; 500 501 /* key2index calculation, -1 on invalid index */ 502 static int sysrq_key_table_key2index(int key) 503 { 504 int retval; 505 506 if ((key >= '0') && (key <= '9')) 507 retval = key - '0'; 508 else if ((key >= 'a') && (key <= 'z')) 509 retval = key + 10 - 'a'; 510 else 511 retval = -1; 512 return retval; 513 } 514 515 /* 516 * get and put functions for the table, exposed to modules. 517 */ 518 struct sysrq_key_op *__sysrq_get_key_op(int key) 519 { 520 struct sysrq_key_op *op_p = NULL; 521 int i; 522 523 i = sysrq_key_table_key2index(key); 524 if (i != -1) 525 op_p = sysrq_key_table[i]; 526 527 return op_p; 528 } 529 530 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 531 { 532 int i = sysrq_key_table_key2index(key); 533 534 if (i != -1) 535 sysrq_key_table[i] = op_p; 536 } 537 538 void __handle_sysrq(int key, bool check_mask) 539 { 540 struct sysrq_key_op *op_p; 541 int orig_log_level; 542 int orig_suppress_printk; 543 int i; 544 545 orig_suppress_printk = suppress_printk; 546 suppress_printk = 0; 547 548 rcu_sysrq_start(); 549 rcu_read_lock(); 550 /* 551 * Raise the apparent loglevel to maximum so that the sysrq header 552 * is shown to provide the user with positive feedback. We do not 553 * simply emit this at KERN_EMERG as that would change message 554 * routing in the consumers of /proc/kmsg. 555 */ 556 orig_log_level = console_loglevel; 557 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 558 559 op_p = __sysrq_get_key_op(key); 560 if (op_p) { 561 /* 562 * Should we check for enabled operations (/proc/sysrq-trigger 563 * should not) and is the invoked operation enabled? 564 */ 565 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 566 pr_info("%s\n", op_p->action_msg); 567 console_loglevel = orig_log_level; 568 op_p->handler(key); 569 } else { 570 pr_info("This sysrq operation is disabled.\n"); 571 console_loglevel = orig_log_level; 572 } 573 } else { 574 pr_info("HELP : "); 575 /* Only print the help msg once per handler */ 576 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 577 if (sysrq_key_table[i]) { 578 int j; 579 580 for (j = 0; sysrq_key_table[i] != 581 sysrq_key_table[j]; j++) 582 ; 583 if (j != i) 584 continue; 585 pr_cont("%s ", sysrq_key_table[i]->help_msg); 586 } 587 } 588 pr_cont("\n"); 589 console_loglevel = orig_log_level; 590 } 591 rcu_read_unlock(); 592 rcu_sysrq_end(); 593 594 suppress_printk = orig_suppress_printk; 595 } 596 597 void handle_sysrq(int key) 598 { 599 if (sysrq_on()) 600 __handle_sysrq(key, true); 601 } 602 EXPORT_SYMBOL(handle_sysrq); 603 604 #ifdef CONFIG_INPUT 605 static int sysrq_reset_downtime_ms; 606 607 /* Simple translation table for the SysRq keys */ 608 static const unsigned char sysrq_xlate[KEY_CNT] = 609 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 610 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 611 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 612 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 613 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 614 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 615 "\r\000/"; /* 0x60 - 0x6f */ 616 617 struct sysrq_state { 618 struct input_handle handle; 619 struct work_struct reinject_work; 620 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 621 unsigned int alt; 622 unsigned int alt_use; 623 bool active; 624 bool need_reinject; 625 bool reinjecting; 626 627 /* reset sequence handling */ 628 bool reset_canceled; 629 bool reset_requested; 630 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 631 int reset_seq_len; 632 int reset_seq_cnt; 633 int reset_seq_version; 634 struct timer_list keyreset_timer; 635 }; 636 637 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 638 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 639 static unsigned int sysrq_reset_seq_len; 640 static unsigned int sysrq_reset_seq_version = 1; 641 642 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 643 { 644 int i; 645 unsigned short key; 646 647 state->reset_seq_cnt = 0; 648 649 for (i = 0; i < sysrq_reset_seq_len; i++) { 650 key = sysrq_reset_seq[i]; 651 652 if (key == KEY_RESERVED || key > KEY_MAX) 653 break; 654 655 __set_bit(key, state->reset_keybit); 656 state->reset_seq_len++; 657 658 if (test_bit(key, state->key_down)) 659 state->reset_seq_cnt++; 660 } 661 662 /* Disable reset until old keys are not released */ 663 state->reset_canceled = state->reset_seq_cnt != 0; 664 665 state->reset_seq_version = sysrq_reset_seq_version; 666 } 667 668 static void sysrq_do_reset(struct timer_list *t) 669 { 670 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 671 672 state->reset_requested = true; 673 674 orderly_reboot(); 675 } 676 677 static void sysrq_handle_reset_request(struct sysrq_state *state) 678 { 679 if (state->reset_requested) 680 __handle_sysrq(sysrq_xlate[KEY_B], false); 681 682 if (sysrq_reset_downtime_ms) 683 mod_timer(&state->keyreset_timer, 684 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 685 else 686 sysrq_do_reset(&state->keyreset_timer); 687 } 688 689 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 690 unsigned int code, int value) 691 { 692 if (!test_bit(code, state->reset_keybit)) { 693 /* 694 * Pressing any key _not_ in reset sequence cancels 695 * the reset sequence. Also cancelling the timer in 696 * case additional keys were pressed after a reset 697 * has been requested. 698 */ 699 if (value && state->reset_seq_cnt) { 700 state->reset_canceled = true; 701 del_timer(&state->keyreset_timer); 702 } 703 } else if (value == 0) { 704 /* 705 * Key release - all keys in the reset sequence need 706 * to be pressed and held for the reset timeout 707 * to hold. 708 */ 709 del_timer(&state->keyreset_timer); 710 711 if (--state->reset_seq_cnt == 0) 712 state->reset_canceled = false; 713 } else if (value == 1) { 714 /* key press, not autorepeat */ 715 if (++state->reset_seq_cnt == state->reset_seq_len && 716 !state->reset_canceled) { 717 sysrq_handle_reset_request(state); 718 } 719 } 720 } 721 722 #ifdef CONFIG_OF 723 static void sysrq_of_get_keyreset_config(void) 724 { 725 u32 key; 726 struct device_node *np; 727 struct property *prop; 728 const __be32 *p; 729 730 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 731 if (!np) { 732 pr_debug("No sysrq node found"); 733 return; 734 } 735 736 /* Reset in case a __weak definition was present */ 737 sysrq_reset_seq_len = 0; 738 739 of_property_for_each_u32(np, "keyset", prop, p, key) { 740 if (key == KEY_RESERVED || key > KEY_MAX || 741 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 742 break; 743 744 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 745 } 746 747 /* Get reset timeout if any. */ 748 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 749 750 of_node_put(np); 751 } 752 #else 753 static void sysrq_of_get_keyreset_config(void) 754 { 755 } 756 #endif 757 758 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 759 { 760 struct sysrq_state *sysrq = 761 container_of(work, struct sysrq_state, reinject_work); 762 struct input_handle *handle = &sysrq->handle; 763 unsigned int alt_code = sysrq->alt_use; 764 765 if (sysrq->need_reinject) { 766 /* we do not want the assignment to be reordered */ 767 sysrq->reinjecting = true; 768 mb(); 769 770 /* Simulate press and release of Alt + SysRq */ 771 input_inject_event(handle, EV_KEY, alt_code, 1); 772 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 773 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 774 775 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 776 input_inject_event(handle, EV_KEY, alt_code, 0); 777 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 778 779 mb(); 780 sysrq->reinjecting = false; 781 } 782 } 783 784 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 785 unsigned int code, int value) 786 { 787 bool was_active = sysrq->active; 788 bool suppress; 789 790 switch (code) { 791 792 case KEY_LEFTALT: 793 case KEY_RIGHTALT: 794 if (!value) { 795 /* One of ALTs is being released */ 796 if (sysrq->active && code == sysrq->alt_use) 797 sysrq->active = false; 798 799 sysrq->alt = KEY_RESERVED; 800 801 } else if (value != 2) { 802 sysrq->alt = code; 803 sysrq->need_reinject = false; 804 } 805 break; 806 807 case KEY_SYSRQ: 808 if (value == 1 && sysrq->alt != KEY_RESERVED) { 809 sysrq->active = true; 810 sysrq->alt_use = sysrq->alt; 811 /* 812 * If nothing else will be pressed we'll need 813 * to re-inject Alt-SysRq keysroke. 814 */ 815 sysrq->need_reinject = true; 816 } 817 818 /* 819 * Pretend that sysrq was never pressed at all. This 820 * is needed to properly handle KGDB which will try 821 * to release all keys after exiting debugger. If we 822 * do not clear key bit it KGDB will end up sending 823 * release events for Alt and SysRq, potentially 824 * triggering print screen function. 825 */ 826 if (sysrq->active) 827 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 828 829 break; 830 831 default: 832 if (sysrq->active && value && value != 2) { 833 sysrq->need_reinject = false; 834 __handle_sysrq(sysrq_xlate[code], true); 835 } 836 break; 837 } 838 839 suppress = sysrq->active; 840 841 if (!sysrq->active) { 842 843 /* 844 * See if reset sequence has changed since the last time. 845 */ 846 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 847 sysrq_parse_reset_sequence(sysrq); 848 849 /* 850 * If we are not suppressing key presses keep track of 851 * keyboard state so we can release keys that have been 852 * pressed before entering SysRq mode. 853 */ 854 if (value) 855 set_bit(code, sysrq->key_down); 856 else 857 clear_bit(code, sysrq->key_down); 858 859 if (was_active) 860 schedule_work(&sysrq->reinject_work); 861 862 /* Check for reset sequence */ 863 sysrq_detect_reset_sequence(sysrq, code, value); 864 865 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 866 /* 867 * Pass on release events for keys that was pressed before 868 * entering SysRq mode. 869 */ 870 suppress = false; 871 } 872 873 return suppress; 874 } 875 876 static bool sysrq_filter(struct input_handle *handle, 877 unsigned int type, unsigned int code, int value) 878 { 879 struct sysrq_state *sysrq = handle->private; 880 bool suppress; 881 882 /* 883 * Do not filter anything if we are in the process of re-injecting 884 * Alt+SysRq combination. 885 */ 886 if (sysrq->reinjecting) 887 return false; 888 889 switch (type) { 890 891 case EV_SYN: 892 suppress = false; 893 break; 894 895 case EV_KEY: 896 suppress = sysrq_handle_keypress(sysrq, code, value); 897 break; 898 899 default: 900 suppress = sysrq->active; 901 break; 902 } 903 904 return suppress; 905 } 906 907 static int sysrq_connect(struct input_handler *handler, 908 struct input_dev *dev, 909 const struct input_device_id *id) 910 { 911 struct sysrq_state *sysrq; 912 int error; 913 914 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 915 if (!sysrq) 916 return -ENOMEM; 917 918 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 919 920 sysrq->handle.dev = dev; 921 sysrq->handle.handler = handler; 922 sysrq->handle.name = "sysrq"; 923 sysrq->handle.private = sysrq; 924 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 925 926 error = input_register_handle(&sysrq->handle); 927 if (error) { 928 pr_err("Failed to register input sysrq handler, error %d\n", 929 error); 930 goto err_free; 931 } 932 933 error = input_open_device(&sysrq->handle); 934 if (error) { 935 pr_err("Failed to open input device, error %d\n", error); 936 goto err_unregister; 937 } 938 939 return 0; 940 941 err_unregister: 942 input_unregister_handle(&sysrq->handle); 943 err_free: 944 kfree(sysrq); 945 return error; 946 } 947 948 static void sysrq_disconnect(struct input_handle *handle) 949 { 950 struct sysrq_state *sysrq = handle->private; 951 952 input_close_device(handle); 953 cancel_work_sync(&sysrq->reinject_work); 954 del_timer_sync(&sysrq->keyreset_timer); 955 input_unregister_handle(handle); 956 kfree(sysrq); 957 } 958 959 /* 960 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 961 * keyboards have SysRq key predefined and so user may add it to keymap 962 * later, but we expect all such keyboards to have left alt. 963 */ 964 static const struct input_device_id sysrq_ids[] = { 965 { 966 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 967 INPUT_DEVICE_ID_MATCH_KEYBIT, 968 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 969 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 970 }, 971 { }, 972 }; 973 974 static struct input_handler sysrq_handler = { 975 .filter = sysrq_filter, 976 .connect = sysrq_connect, 977 .disconnect = sysrq_disconnect, 978 .name = "sysrq", 979 .id_table = sysrq_ids, 980 }; 981 982 static inline void sysrq_register_handler(void) 983 { 984 int error; 985 986 sysrq_of_get_keyreset_config(); 987 988 error = input_register_handler(&sysrq_handler); 989 if (error) 990 pr_err("Failed to register input handler, error %d", error); 991 } 992 993 static inline void sysrq_unregister_handler(void) 994 { 995 input_unregister_handler(&sysrq_handler); 996 } 997 998 static int sysrq_reset_seq_param_set(const char *buffer, 999 const struct kernel_param *kp) 1000 { 1001 unsigned long val; 1002 int error; 1003 1004 error = kstrtoul(buffer, 0, &val); 1005 if (error < 0) 1006 return error; 1007 1008 if (val > KEY_MAX) 1009 return -EINVAL; 1010 1011 *((unsigned short *)kp->arg) = val; 1012 sysrq_reset_seq_version++; 1013 1014 return 0; 1015 } 1016 1017 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1018 .get = param_get_ushort, 1019 .set = sysrq_reset_seq_param_set, 1020 }; 1021 1022 #define param_check_sysrq_reset_seq(name, p) \ 1023 __param_check(name, p, unsigned short) 1024 1025 /* 1026 * not really modular, but the easiest way to keep compat with existing 1027 * bootargs behaviour is to continue using module_param here. 1028 */ 1029 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1030 &sysrq_reset_seq_len, 0644); 1031 1032 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1033 1034 #else 1035 1036 static inline void sysrq_register_handler(void) 1037 { 1038 } 1039 1040 static inline void sysrq_unregister_handler(void) 1041 { 1042 } 1043 1044 #endif /* CONFIG_INPUT */ 1045 1046 int sysrq_toggle_support(int enable_mask) 1047 { 1048 bool was_enabled = sysrq_on(); 1049 1050 sysrq_enabled = enable_mask; 1051 1052 if (was_enabled != sysrq_on()) { 1053 if (sysrq_on()) 1054 sysrq_register_handler(); 1055 else 1056 sysrq_unregister_handler(); 1057 } 1058 1059 return 0; 1060 } 1061 1062 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1063 struct sysrq_key_op *remove_op_p) 1064 { 1065 int retval; 1066 1067 spin_lock(&sysrq_key_table_lock); 1068 if (__sysrq_get_key_op(key) == remove_op_p) { 1069 __sysrq_put_key_op(key, insert_op_p); 1070 retval = 0; 1071 } else { 1072 retval = -1; 1073 } 1074 spin_unlock(&sysrq_key_table_lock); 1075 1076 /* 1077 * A concurrent __handle_sysrq either got the old op or the new op. 1078 * Wait for it to go away before returning, so the code for an old 1079 * op is not freed (eg. on module unload) while it is in use. 1080 */ 1081 synchronize_rcu(); 1082 1083 return retval; 1084 } 1085 1086 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1087 { 1088 return __sysrq_swap_key_ops(key, op_p, NULL); 1089 } 1090 EXPORT_SYMBOL(register_sysrq_key); 1091 1092 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1093 { 1094 return __sysrq_swap_key_ops(key, NULL, op_p); 1095 } 1096 EXPORT_SYMBOL(unregister_sysrq_key); 1097 1098 #ifdef CONFIG_PROC_FS 1099 /* 1100 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1101 */ 1102 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1103 size_t count, loff_t *ppos) 1104 { 1105 if (count) { 1106 char c; 1107 1108 if (get_user(c, buf)) 1109 return -EFAULT; 1110 __handle_sysrq(c, false); 1111 } 1112 1113 return count; 1114 } 1115 1116 static const struct proc_ops sysrq_trigger_proc_ops = { 1117 .proc_write = write_sysrq_trigger, 1118 .proc_lseek = noop_llseek, 1119 }; 1120 1121 static void sysrq_init_procfs(void) 1122 { 1123 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1124 &sysrq_trigger_proc_ops)) 1125 pr_err("Failed to register proc interface\n"); 1126 } 1127 1128 #else 1129 1130 static inline void sysrq_init_procfs(void) 1131 { 1132 } 1133 1134 #endif /* CONFIG_PROC_FS */ 1135 1136 static int __init sysrq_init(void) 1137 { 1138 sysrq_init_procfs(); 1139 1140 if (sysrq_on()) 1141 sysrq_register_handler(); 1142 1143 return 0; 1144 } 1145 device_initcall(sysrq_init); 1146