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/ctype.h> 23 #include <linux/interrupt.h> 24 #include <linux/mm.h> 25 #include <linux/fs.h> 26 #include <linux/mount.h> 27 #include <linux/kdev_t.h> 28 #include <linux/major.h> 29 #include <linux/reboot.h> 30 #include <linux/sysrq.h> 31 #include <linux/kbd_kern.h> 32 #include <linux/proc_fs.h> 33 #include <linux/nmi.h> 34 #include <linux/quotaops.h> 35 #include <linux/perf_event.h> 36 #include <linux/kernel.h> 37 #include <linux/module.h> 38 #include <linux/suspend.h> 39 #include <linux/writeback.h> 40 #include <linux/swap.h> 41 #include <linux/spinlock.h> 42 #include <linux/vt_kern.h> 43 #include <linux/workqueue.h> 44 #include <linux/hrtimer.h> 45 #include <linux/oom.h> 46 #include <linux/slab.h> 47 #include <linux/input.h> 48 #include <linux/uaccess.h> 49 #include <linux/moduleparam.h> 50 #include <linux/jiffies.h> 51 #include <linux/syscalls.h> 52 #include <linux/of.h> 53 #include <linux/rcupdate.h> 54 55 #include <asm/ptrace.h> 56 #include <asm/irq_regs.h> 57 58 /* Whether we react on sysrq keys or just ignore them */ 59 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; 60 static bool __read_mostly sysrq_always_enabled; 61 62 static bool sysrq_on(void) 63 { 64 return sysrq_enabled || sysrq_always_enabled; 65 } 66 67 /** 68 * sysrq_mask - Getter for sysrq_enabled mask. 69 * 70 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise. 71 */ 72 int sysrq_mask(void) 73 { 74 if (sysrq_always_enabled) 75 return 1; 76 return sysrq_enabled; 77 } 78 EXPORT_SYMBOL_GPL(sysrq_mask); 79 80 /* 81 * A value of 1 means 'all', other nonzero values are an op mask: 82 */ 83 static bool sysrq_on_mask(int mask) 84 { 85 return sysrq_always_enabled || 86 sysrq_enabled == 1 || 87 (sysrq_enabled & mask); 88 } 89 90 static int __init sysrq_always_enabled_setup(char *str) 91 { 92 sysrq_always_enabled = true; 93 pr_info("sysrq always enabled.\n"); 94 95 return 1; 96 } 97 98 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 99 100 101 static void sysrq_handle_loglevel(u8 key) 102 { 103 u8 loglevel = key - '0'; 104 105 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 106 pr_info("Loglevel set to %u\n", loglevel); 107 console_loglevel = loglevel; 108 } 109 static const struct sysrq_key_op sysrq_loglevel_op = { 110 .handler = sysrq_handle_loglevel, 111 .help_msg = "loglevel(0-9)", 112 .action_msg = "Changing Loglevel", 113 .enable_mask = SYSRQ_ENABLE_LOG, 114 }; 115 116 #ifdef CONFIG_VT 117 static void sysrq_handle_SAK(u8 key) 118 { 119 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 120 121 schedule_work(SAK_work); 122 } 123 static const struct sysrq_key_op sysrq_SAK_op = { 124 .handler = sysrq_handle_SAK, 125 .help_msg = "sak(k)", 126 .action_msg = "SAK", 127 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 128 }; 129 #else 130 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL) 131 #endif 132 133 #ifdef CONFIG_VT 134 static void sysrq_handle_unraw(u8 key) 135 { 136 vt_reset_unicode(fg_console); 137 } 138 139 static const struct sysrq_key_op sysrq_unraw_op = { 140 .handler = sysrq_handle_unraw, 141 .help_msg = "unraw(r)", 142 .action_msg = "Keyboard mode set to system default", 143 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 144 }; 145 #else 146 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL) 147 #endif /* CONFIG_VT */ 148 149 static void sysrq_handle_crash(u8 key) 150 { 151 /* release the RCU read lock before crashing */ 152 rcu_read_unlock(); 153 154 panic("sysrq triggered crash\n"); 155 } 156 static const struct sysrq_key_op sysrq_crash_op = { 157 .handler = sysrq_handle_crash, 158 .help_msg = "crash(c)", 159 .action_msg = "Trigger a crash", 160 .enable_mask = SYSRQ_ENABLE_DUMP, 161 }; 162 163 static void sysrq_handle_reboot(u8 key) 164 { 165 lockdep_off(); 166 local_irq_enable(); 167 emergency_restart(); 168 } 169 static const struct sysrq_key_op sysrq_reboot_op = { 170 .handler = sysrq_handle_reboot, 171 .help_msg = "reboot(b)", 172 .action_msg = "Resetting", 173 .enable_mask = SYSRQ_ENABLE_BOOT, 174 }; 175 176 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op; 177 178 static void sysrq_handle_sync(u8 key) 179 { 180 emergency_sync(); 181 } 182 static const struct sysrq_key_op sysrq_sync_op = { 183 .handler = sysrq_handle_sync, 184 .help_msg = "sync(s)", 185 .action_msg = "Emergency Sync", 186 .enable_mask = SYSRQ_ENABLE_SYNC, 187 }; 188 189 static void sysrq_handle_show_timers(u8 key) 190 { 191 sysrq_timer_list_show(); 192 } 193 194 static const struct sysrq_key_op sysrq_show_timers_op = { 195 .handler = sysrq_handle_show_timers, 196 .help_msg = "show-all-timers(q)", 197 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 198 }; 199 200 static void sysrq_handle_mountro(u8 key) 201 { 202 emergency_remount(); 203 } 204 static const struct sysrq_key_op sysrq_mountro_op = { 205 .handler = sysrq_handle_mountro, 206 .help_msg = "unmount(u)", 207 .action_msg = "Emergency Remount R/O", 208 .enable_mask = SYSRQ_ENABLE_REMOUNT, 209 }; 210 211 #ifdef CONFIG_LOCKDEP 212 static void sysrq_handle_showlocks(u8 key) 213 { 214 debug_show_all_locks(); 215 } 216 217 static const struct sysrq_key_op sysrq_showlocks_op = { 218 .handler = sysrq_handle_showlocks, 219 .help_msg = "show-all-locks(d)", 220 .action_msg = "Show Locks Held", 221 }; 222 #else 223 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL) 224 #endif 225 226 #ifdef CONFIG_SMP 227 static DEFINE_RAW_SPINLOCK(show_lock); 228 229 static void showacpu(void *dummy) 230 { 231 unsigned long flags; 232 233 /* Idle CPUs have no interesting backtrace. */ 234 if (idle_cpu(smp_processor_id())) { 235 pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id()); 236 return; 237 } 238 239 raw_spin_lock_irqsave(&show_lock, flags); 240 pr_info("CPU%d:\n", smp_processor_id()); 241 show_stack(NULL, NULL, KERN_INFO); 242 raw_spin_unlock_irqrestore(&show_lock, flags); 243 } 244 245 static void sysrq_showregs_othercpus(struct work_struct *dummy) 246 { 247 smp_call_function(showacpu, NULL, 0); 248 } 249 250 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 251 252 static void sysrq_handle_showallcpus(u8 key) 253 { 254 /* 255 * Fall back to the workqueue based printing if the 256 * backtrace printing did not succeed or the 257 * architecture has no support for it: 258 */ 259 if (!trigger_all_cpu_backtrace()) { 260 struct pt_regs *regs = NULL; 261 262 if (in_hardirq()) 263 regs = get_irq_regs(); 264 265 pr_info("CPU%d:\n", get_cpu()); 266 if (regs) 267 show_regs(regs); 268 else 269 show_stack(NULL, NULL, KERN_INFO); 270 271 schedule_work(&sysrq_showallcpus); 272 put_cpu(); 273 } 274 } 275 276 static const struct sysrq_key_op sysrq_showallcpus_op = { 277 .handler = sysrq_handle_showallcpus, 278 .help_msg = "show-backtrace-all-active-cpus(l)", 279 .action_msg = "Show backtrace of all active CPUs", 280 .enable_mask = SYSRQ_ENABLE_DUMP, 281 }; 282 #else 283 #define sysrq_showallcpus_op (*(const struct sysrq_key_op *)NULL) 284 #endif 285 286 static void sysrq_handle_showregs(u8 key) 287 { 288 struct pt_regs *regs = NULL; 289 290 if (in_hardirq()) 291 regs = get_irq_regs(); 292 if (regs) 293 show_regs(regs); 294 perf_event_print_debug(); 295 } 296 static const struct sysrq_key_op sysrq_showregs_op = { 297 .handler = sysrq_handle_showregs, 298 .help_msg = "show-registers(p)", 299 .action_msg = "Show Regs", 300 .enable_mask = SYSRQ_ENABLE_DUMP, 301 }; 302 303 static void sysrq_handle_showstate(u8 key) 304 { 305 show_state(); 306 show_all_workqueues(); 307 } 308 static const struct sysrq_key_op sysrq_showstate_op = { 309 .handler = sysrq_handle_showstate, 310 .help_msg = "show-task-states(t)", 311 .action_msg = "Show State", 312 .enable_mask = SYSRQ_ENABLE_DUMP, 313 }; 314 315 static void sysrq_handle_showstate_blocked(u8 key) 316 { 317 show_state_filter(TASK_UNINTERRUPTIBLE); 318 } 319 static const struct sysrq_key_op sysrq_showstate_blocked_op = { 320 .handler = sysrq_handle_showstate_blocked, 321 .help_msg = "show-blocked-tasks(w)", 322 .action_msg = "Show Blocked State", 323 .enable_mask = SYSRQ_ENABLE_DUMP, 324 }; 325 326 #ifdef CONFIG_TRACING 327 #include <linux/ftrace.h> 328 329 static void sysrq_ftrace_dump(u8 key) 330 { 331 ftrace_dump(DUMP_ALL); 332 } 333 static const struct sysrq_key_op sysrq_ftrace_dump_op = { 334 .handler = sysrq_ftrace_dump, 335 .help_msg = "dump-ftrace-buffer(z)", 336 .action_msg = "Dump ftrace buffer", 337 .enable_mask = SYSRQ_ENABLE_DUMP, 338 }; 339 #else 340 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL) 341 #endif 342 343 static void sysrq_handle_showmem(u8 key) 344 { 345 show_mem(); 346 } 347 static const struct sysrq_key_op sysrq_showmem_op = { 348 .handler = sysrq_handle_showmem, 349 .help_msg = "show-memory-usage(m)", 350 .action_msg = "Show Memory", 351 .enable_mask = SYSRQ_ENABLE_DUMP, 352 }; 353 354 /* 355 * Signal sysrq helper function. Sends a signal to all user processes. 356 */ 357 static void send_sig_all(int sig) 358 { 359 struct task_struct *p; 360 361 read_lock(&tasklist_lock); 362 for_each_process(p) { 363 if (p->flags & PF_KTHREAD) 364 continue; 365 if (is_global_init(p)) 366 continue; 367 368 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX); 369 } 370 read_unlock(&tasklist_lock); 371 } 372 373 static void sysrq_handle_term(u8 key) 374 { 375 send_sig_all(SIGTERM); 376 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 377 } 378 static const struct sysrq_key_op sysrq_term_op = { 379 .handler = sysrq_handle_term, 380 .help_msg = "terminate-all-tasks(e)", 381 .action_msg = "Terminate All Tasks", 382 .enable_mask = SYSRQ_ENABLE_SIGNAL, 383 }; 384 385 static void moom_callback(struct work_struct *ignored) 386 { 387 const gfp_t gfp_mask = GFP_KERNEL; 388 struct oom_control oc = { 389 .zonelist = node_zonelist(first_memory_node, gfp_mask), 390 .nodemask = NULL, 391 .memcg = NULL, 392 .gfp_mask = gfp_mask, 393 .order = -1, 394 }; 395 396 mutex_lock(&oom_lock); 397 if (!out_of_memory(&oc)) 398 pr_info("OOM request ignored. No task eligible\n"); 399 mutex_unlock(&oom_lock); 400 } 401 402 static DECLARE_WORK(moom_work, moom_callback); 403 404 static void sysrq_handle_moom(u8 key) 405 { 406 schedule_work(&moom_work); 407 } 408 static const struct sysrq_key_op sysrq_moom_op = { 409 .handler = sysrq_handle_moom, 410 .help_msg = "memory-full-oom-kill(f)", 411 .action_msg = "Manual OOM execution", 412 .enable_mask = SYSRQ_ENABLE_SIGNAL, 413 }; 414 415 #ifdef CONFIG_BLOCK 416 static void sysrq_handle_thaw(u8 key) 417 { 418 emergency_thaw_all(); 419 } 420 static const struct sysrq_key_op sysrq_thaw_op = { 421 .handler = sysrq_handle_thaw, 422 .help_msg = "thaw-filesystems(j)", 423 .action_msg = "Emergency Thaw of all frozen filesystems", 424 .enable_mask = SYSRQ_ENABLE_SIGNAL, 425 }; 426 #else 427 #define sysrq_thaw_op (*(const struct sysrq_key_op *)NULL) 428 #endif 429 430 static void sysrq_handle_kill(u8 key) 431 { 432 send_sig_all(SIGKILL); 433 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 434 } 435 static const struct sysrq_key_op sysrq_kill_op = { 436 .handler = sysrq_handle_kill, 437 .help_msg = "kill-all-tasks(i)", 438 .action_msg = "Kill All Tasks", 439 .enable_mask = SYSRQ_ENABLE_SIGNAL, 440 }; 441 442 static void sysrq_handle_unrt(u8 key) 443 { 444 normalize_rt_tasks(); 445 } 446 static const struct sysrq_key_op sysrq_unrt_op = { 447 .handler = sysrq_handle_unrt, 448 .help_msg = "nice-all-RT-tasks(n)", 449 .action_msg = "Nice All RT Tasks", 450 .enable_mask = SYSRQ_ENABLE_RTNICE, 451 }; 452 453 /* Key Operations table and lock */ 454 static DEFINE_SPINLOCK(sysrq_key_table_lock); 455 456 static const struct sysrq_key_op *sysrq_key_table[62] = { 457 &sysrq_loglevel_op, /* 0 */ 458 &sysrq_loglevel_op, /* 1 */ 459 &sysrq_loglevel_op, /* 2 */ 460 &sysrq_loglevel_op, /* 3 */ 461 &sysrq_loglevel_op, /* 4 */ 462 &sysrq_loglevel_op, /* 5 */ 463 &sysrq_loglevel_op, /* 6 */ 464 &sysrq_loglevel_op, /* 7 */ 465 &sysrq_loglevel_op, /* 8 */ 466 &sysrq_loglevel_op, /* 9 */ 467 468 /* 469 * a: Don't use for system provided sysrqs, it is handled specially on 470 * sparc and will never arrive. 471 */ 472 NULL, /* a */ 473 &sysrq_reboot_op, /* b */ 474 &sysrq_crash_op, /* c */ 475 &sysrq_showlocks_op, /* d */ 476 &sysrq_term_op, /* e */ 477 &sysrq_moom_op, /* f */ 478 /* g: May be registered for the kernel debugger */ 479 NULL, /* g */ 480 NULL, /* h - reserved for help */ 481 &sysrq_kill_op, /* i */ 482 &sysrq_thaw_op, /* j */ 483 &sysrq_SAK_op, /* k */ 484 &sysrq_showallcpus_op, /* l */ 485 &sysrq_showmem_op, /* m */ 486 &sysrq_unrt_op, /* n */ 487 /* o: This will often be registered as 'Off' at init time */ 488 NULL, /* o */ 489 &sysrq_showregs_op, /* p */ 490 &sysrq_show_timers_op, /* q */ 491 &sysrq_unraw_op, /* r */ 492 &sysrq_sync_op, /* s */ 493 &sysrq_showstate_op, /* t */ 494 &sysrq_mountro_op, /* u */ 495 /* v: May be registered for frame buffer console restore */ 496 NULL, /* v */ 497 &sysrq_showstate_blocked_op, /* w */ 498 /* x: May be registered on mips for TLB dump */ 499 /* x: May be registered on ppc/powerpc for xmon */ 500 /* x: May be registered on sparc64 for global PMU dump */ 501 NULL, /* x */ 502 /* y: May be registered on sparc64 for global register dump */ 503 NULL, /* y */ 504 &sysrq_ftrace_dump_op, /* z */ 505 NULL, /* A */ 506 NULL, /* B */ 507 NULL, /* C */ 508 NULL, /* D */ 509 NULL, /* E */ 510 NULL, /* F */ 511 NULL, /* G */ 512 NULL, /* H */ 513 NULL, /* I */ 514 NULL, /* J */ 515 NULL, /* K */ 516 NULL, /* L */ 517 NULL, /* M */ 518 NULL, /* N */ 519 NULL, /* O */ 520 NULL, /* P */ 521 NULL, /* Q */ 522 NULL, /* R */ 523 NULL, /* S */ 524 NULL, /* T */ 525 NULL, /* U */ 526 NULL, /* V */ 527 NULL, /* W */ 528 NULL, /* X */ 529 NULL, /* Y */ 530 NULL, /* Z */ 531 }; 532 533 /* key2index calculation, -1 on invalid index */ 534 static int sysrq_key_table_key2index(u8 key) 535 { 536 switch (key) { 537 case '0' ... '9': 538 return key - '0'; 539 case 'a' ... 'z': 540 return key - 'a' + 10; 541 case 'A' ... 'Z': 542 return key - 'A' + 10 + 26; 543 default: 544 return -1; 545 } 546 } 547 548 /* 549 * get and put functions for the table, exposed to modules. 550 */ 551 static const struct sysrq_key_op *__sysrq_get_key_op(u8 key) 552 { 553 const struct sysrq_key_op *op_p = NULL; 554 int i; 555 556 i = sysrq_key_table_key2index(key); 557 if (i != -1) 558 op_p = sysrq_key_table[i]; 559 560 return op_p; 561 } 562 563 static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p) 564 { 565 int i = sysrq_key_table_key2index(key); 566 567 if (i != -1) 568 sysrq_key_table[i] = op_p; 569 } 570 571 void __handle_sysrq(u8 key, bool check_mask) 572 { 573 const struct sysrq_key_op *op_p; 574 int orig_log_level; 575 int orig_suppress_printk; 576 int i; 577 578 orig_suppress_printk = suppress_printk; 579 suppress_printk = 0; 580 581 rcu_sysrq_start(); 582 rcu_read_lock(); 583 /* 584 * Raise the apparent loglevel to maximum so that the sysrq header 585 * is shown to provide the user with positive feedback. We do not 586 * simply emit this at KERN_EMERG as that would change message 587 * routing in the consumers of /proc/kmsg. 588 */ 589 orig_log_level = console_loglevel; 590 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 591 592 op_p = __sysrq_get_key_op(key); 593 if (op_p) { 594 /* 595 * Should we check for enabled operations (/proc/sysrq-trigger 596 * should not) and is the invoked operation enabled? 597 */ 598 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 599 pr_info("%s\n", op_p->action_msg); 600 console_loglevel = orig_log_level; 601 op_p->handler(key); 602 } else { 603 pr_info("This sysrq operation is disabled.\n"); 604 console_loglevel = orig_log_level; 605 } 606 } else { 607 pr_info("HELP : "); 608 /* Only print the help msg once per handler */ 609 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 610 if (sysrq_key_table[i]) { 611 int j; 612 613 for (j = 0; sysrq_key_table[i] != 614 sysrq_key_table[j]; j++) 615 ; 616 if (j != i) 617 continue; 618 pr_cont("%s ", sysrq_key_table[i]->help_msg); 619 } 620 } 621 pr_cont("\n"); 622 console_loglevel = orig_log_level; 623 } 624 rcu_read_unlock(); 625 rcu_sysrq_end(); 626 627 suppress_printk = orig_suppress_printk; 628 } 629 630 void handle_sysrq(u8 key) 631 { 632 if (sysrq_on()) 633 __handle_sysrq(key, true); 634 } 635 EXPORT_SYMBOL(handle_sysrq); 636 637 #ifdef CONFIG_INPUT 638 static int sysrq_reset_downtime_ms; 639 640 /* Simple translation table for the SysRq keys */ 641 static const unsigned char sysrq_xlate[KEY_CNT] = 642 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 643 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 644 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 645 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 646 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 647 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 648 "\r\000/"; /* 0x60 - 0x6f */ 649 650 struct sysrq_state { 651 struct input_handle handle; 652 struct work_struct reinject_work; 653 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 654 unsigned int alt; 655 unsigned int alt_use; 656 unsigned int shift; 657 unsigned int shift_use; 658 bool active; 659 bool need_reinject; 660 bool reinjecting; 661 662 /* reset sequence handling */ 663 bool reset_canceled; 664 bool reset_requested; 665 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 666 int reset_seq_len; 667 int reset_seq_cnt; 668 int reset_seq_version; 669 struct timer_list keyreset_timer; 670 }; 671 672 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 673 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 674 static unsigned int sysrq_reset_seq_len; 675 static unsigned int sysrq_reset_seq_version = 1; 676 677 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 678 { 679 int i; 680 unsigned short key; 681 682 state->reset_seq_cnt = 0; 683 684 for (i = 0; i < sysrq_reset_seq_len; i++) { 685 key = sysrq_reset_seq[i]; 686 687 if (key == KEY_RESERVED || key > KEY_MAX) 688 break; 689 690 __set_bit(key, state->reset_keybit); 691 state->reset_seq_len++; 692 693 if (test_bit(key, state->key_down)) 694 state->reset_seq_cnt++; 695 } 696 697 /* Disable reset until old keys are not released */ 698 state->reset_canceled = state->reset_seq_cnt != 0; 699 700 state->reset_seq_version = sysrq_reset_seq_version; 701 } 702 703 static void sysrq_do_reset(struct timer_list *t) 704 { 705 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 706 707 state->reset_requested = true; 708 709 orderly_reboot(); 710 } 711 712 static void sysrq_handle_reset_request(struct sysrq_state *state) 713 { 714 if (state->reset_requested) 715 __handle_sysrq(sysrq_xlate[KEY_B], false); 716 717 if (sysrq_reset_downtime_ms) 718 mod_timer(&state->keyreset_timer, 719 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 720 else 721 sysrq_do_reset(&state->keyreset_timer); 722 } 723 724 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 725 unsigned int code, int value) 726 { 727 if (!test_bit(code, state->reset_keybit)) { 728 /* 729 * Pressing any key _not_ in reset sequence cancels 730 * the reset sequence. Also cancelling the timer in 731 * case additional keys were pressed after a reset 732 * has been requested. 733 */ 734 if (value && state->reset_seq_cnt) { 735 state->reset_canceled = true; 736 del_timer(&state->keyreset_timer); 737 } 738 } else if (value == 0) { 739 /* 740 * Key release - all keys in the reset sequence need 741 * to be pressed and held for the reset timeout 742 * to hold. 743 */ 744 del_timer(&state->keyreset_timer); 745 746 if (--state->reset_seq_cnt == 0) 747 state->reset_canceled = false; 748 } else if (value == 1) { 749 /* key press, not autorepeat */ 750 if (++state->reset_seq_cnt == state->reset_seq_len && 751 !state->reset_canceled) { 752 sysrq_handle_reset_request(state); 753 } 754 } 755 } 756 757 #ifdef CONFIG_OF 758 static void sysrq_of_get_keyreset_config(void) 759 { 760 u32 key; 761 struct device_node *np; 762 struct property *prop; 763 const __be32 *p; 764 765 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 766 if (!np) { 767 pr_debug("No sysrq node found"); 768 return; 769 } 770 771 /* Reset in case a __weak definition was present */ 772 sysrq_reset_seq_len = 0; 773 774 of_property_for_each_u32(np, "keyset", prop, p, key) { 775 if (key == KEY_RESERVED || key > KEY_MAX || 776 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 777 break; 778 779 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 780 } 781 782 /* Get reset timeout if any. */ 783 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 784 785 of_node_put(np); 786 } 787 #else 788 static void sysrq_of_get_keyreset_config(void) 789 { 790 } 791 #endif 792 793 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 794 { 795 struct sysrq_state *sysrq = 796 container_of(work, struct sysrq_state, reinject_work); 797 struct input_handle *handle = &sysrq->handle; 798 unsigned int alt_code = sysrq->alt_use; 799 800 if (sysrq->need_reinject) { 801 /* we do not want the assignment to be reordered */ 802 sysrq->reinjecting = true; 803 mb(); 804 805 /* Simulate press and release of Alt + SysRq */ 806 input_inject_event(handle, EV_KEY, alt_code, 1); 807 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 808 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 809 810 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 811 input_inject_event(handle, EV_KEY, alt_code, 0); 812 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 813 814 mb(); 815 sysrq->reinjecting = false; 816 } 817 } 818 819 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 820 unsigned int code, int value) 821 { 822 bool was_active = sysrq->active; 823 bool suppress; 824 825 switch (code) { 826 827 case KEY_LEFTALT: 828 case KEY_RIGHTALT: 829 if (!value) { 830 /* One of ALTs is being released */ 831 if (sysrq->active && code == sysrq->alt_use) 832 sysrq->active = false; 833 834 sysrq->alt = KEY_RESERVED; 835 836 } else if (value != 2) { 837 sysrq->alt = code; 838 sysrq->need_reinject = false; 839 } 840 break; 841 842 case KEY_LEFTSHIFT: 843 case KEY_RIGHTSHIFT: 844 if (!value) 845 sysrq->shift = KEY_RESERVED; 846 else if (value != 2) 847 sysrq->shift = code; 848 if (sysrq->active) 849 sysrq->shift_use = sysrq->shift; 850 break; 851 852 case KEY_SYSRQ: 853 if (value == 1 && sysrq->alt != KEY_RESERVED) { 854 sysrq->active = true; 855 sysrq->alt_use = sysrq->alt; 856 /* either RESERVED (for released) or actual code */ 857 sysrq->shift_use = sysrq->shift; 858 /* 859 * If nothing else will be pressed we'll need 860 * to re-inject Alt-SysRq keysroke. 861 */ 862 sysrq->need_reinject = true; 863 } 864 865 /* 866 * Pretend that sysrq was never pressed at all. This 867 * is needed to properly handle KGDB which will try 868 * to release all keys after exiting debugger. If we 869 * do not clear key bit it KGDB will end up sending 870 * release events for Alt and SysRq, potentially 871 * triggering print screen function. 872 */ 873 if (sysrq->active) 874 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 875 876 break; 877 878 default: 879 if (sysrq->active && value && value != 2) { 880 unsigned char c = sysrq_xlate[code]; 881 882 sysrq->need_reinject = false; 883 if (sysrq->shift_use != KEY_RESERVED) 884 c = toupper(c); 885 __handle_sysrq(c, true); 886 } 887 break; 888 } 889 890 suppress = sysrq->active; 891 892 if (!sysrq->active) { 893 894 /* 895 * See if reset sequence has changed since the last time. 896 */ 897 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 898 sysrq_parse_reset_sequence(sysrq); 899 900 /* 901 * If we are not suppressing key presses keep track of 902 * keyboard state so we can release keys that have been 903 * pressed before entering SysRq mode. 904 */ 905 if (value) 906 set_bit(code, sysrq->key_down); 907 else 908 clear_bit(code, sysrq->key_down); 909 910 if (was_active) 911 schedule_work(&sysrq->reinject_work); 912 913 /* Check for reset sequence */ 914 sysrq_detect_reset_sequence(sysrq, code, value); 915 916 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 917 /* 918 * Pass on release events for keys that was pressed before 919 * entering SysRq mode. 920 */ 921 suppress = false; 922 } 923 924 return suppress; 925 } 926 927 static bool sysrq_filter(struct input_handle *handle, 928 unsigned int type, unsigned int code, int value) 929 { 930 struct sysrq_state *sysrq = handle->private; 931 bool suppress; 932 933 /* 934 * Do not filter anything if we are in the process of re-injecting 935 * Alt+SysRq combination. 936 */ 937 if (sysrq->reinjecting) 938 return false; 939 940 switch (type) { 941 942 case EV_SYN: 943 suppress = false; 944 break; 945 946 case EV_KEY: 947 suppress = sysrq_handle_keypress(sysrq, code, value); 948 break; 949 950 default: 951 suppress = sysrq->active; 952 break; 953 } 954 955 return suppress; 956 } 957 958 static int sysrq_connect(struct input_handler *handler, 959 struct input_dev *dev, 960 const struct input_device_id *id) 961 { 962 struct sysrq_state *sysrq; 963 int error; 964 965 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 966 if (!sysrq) 967 return -ENOMEM; 968 969 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 970 971 sysrq->handle.dev = dev; 972 sysrq->handle.handler = handler; 973 sysrq->handle.name = "sysrq"; 974 sysrq->handle.private = sysrq; 975 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 976 977 error = input_register_handle(&sysrq->handle); 978 if (error) { 979 pr_err("Failed to register input sysrq handler, error %d\n", 980 error); 981 goto err_free; 982 } 983 984 error = input_open_device(&sysrq->handle); 985 if (error) { 986 pr_err("Failed to open input device, error %d\n", error); 987 goto err_unregister; 988 } 989 990 return 0; 991 992 err_unregister: 993 input_unregister_handle(&sysrq->handle); 994 err_free: 995 kfree(sysrq); 996 return error; 997 } 998 999 static void sysrq_disconnect(struct input_handle *handle) 1000 { 1001 struct sysrq_state *sysrq = handle->private; 1002 1003 input_close_device(handle); 1004 cancel_work_sync(&sysrq->reinject_work); 1005 timer_shutdown_sync(&sysrq->keyreset_timer); 1006 input_unregister_handle(handle); 1007 kfree(sysrq); 1008 } 1009 1010 /* 1011 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 1012 * keyboards have SysRq key predefined and so user may add it to keymap 1013 * later, but we expect all such keyboards to have left alt. 1014 */ 1015 static const struct input_device_id sysrq_ids[] = { 1016 { 1017 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 1018 INPUT_DEVICE_ID_MATCH_KEYBIT, 1019 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 1020 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 1021 }, 1022 { }, 1023 }; 1024 1025 static struct input_handler sysrq_handler = { 1026 .filter = sysrq_filter, 1027 .connect = sysrq_connect, 1028 .disconnect = sysrq_disconnect, 1029 .name = "sysrq", 1030 .id_table = sysrq_ids, 1031 }; 1032 1033 static inline void sysrq_register_handler(void) 1034 { 1035 int error; 1036 1037 sysrq_of_get_keyreset_config(); 1038 1039 error = input_register_handler(&sysrq_handler); 1040 if (error) 1041 pr_err("Failed to register input handler, error %d", error); 1042 } 1043 1044 static inline void sysrq_unregister_handler(void) 1045 { 1046 input_unregister_handler(&sysrq_handler); 1047 } 1048 1049 static int sysrq_reset_seq_param_set(const char *buffer, 1050 const struct kernel_param *kp) 1051 { 1052 unsigned long val; 1053 int error; 1054 1055 error = kstrtoul(buffer, 0, &val); 1056 if (error < 0) 1057 return error; 1058 1059 if (val > KEY_MAX) 1060 return -EINVAL; 1061 1062 *((unsigned short *)kp->arg) = val; 1063 sysrq_reset_seq_version++; 1064 1065 return 0; 1066 } 1067 1068 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1069 .get = param_get_ushort, 1070 .set = sysrq_reset_seq_param_set, 1071 }; 1072 1073 #define param_check_sysrq_reset_seq(name, p) \ 1074 __param_check(name, p, unsigned short) 1075 1076 /* 1077 * not really modular, but the easiest way to keep compat with existing 1078 * bootargs behaviour is to continue using module_param here. 1079 */ 1080 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1081 &sysrq_reset_seq_len, 0644); 1082 1083 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1084 1085 #else 1086 1087 static inline void sysrq_register_handler(void) 1088 { 1089 } 1090 1091 static inline void sysrq_unregister_handler(void) 1092 { 1093 } 1094 1095 #endif /* CONFIG_INPUT */ 1096 1097 int sysrq_toggle_support(int enable_mask) 1098 { 1099 bool was_enabled = sysrq_on(); 1100 1101 sysrq_enabled = enable_mask; 1102 1103 if (was_enabled != sysrq_on()) { 1104 if (sysrq_on()) 1105 sysrq_register_handler(); 1106 else 1107 sysrq_unregister_handler(); 1108 } 1109 1110 return 0; 1111 } 1112 EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1113 1114 static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p, 1115 const struct sysrq_key_op *remove_op_p) 1116 { 1117 int retval; 1118 1119 spin_lock(&sysrq_key_table_lock); 1120 if (__sysrq_get_key_op(key) == remove_op_p) { 1121 __sysrq_put_key_op(key, insert_op_p); 1122 retval = 0; 1123 } else { 1124 retval = -1; 1125 } 1126 spin_unlock(&sysrq_key_table_lock); 1127 1128 /* 1129 * A concurrent __handle_sysrq either got the old op or the new op. 1130 * Wait for it to go away before returning, so the code for an old 1131 * op is not freed (eg. on module unload) while it is in use. 1132 */ 1133 synchronize_rcu(); 1134 1135 return retval; 1136 } 1137 1138 int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p) 1139 { 1140 return __sysrq_swap_key_ops(key, op_p, NULL); 1141 } 1142 EXPORT_SYMBOL(register_sysrq_key); 1143 1144 int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p) 1145 { 1146 return __sysrq_swap_key_ops(key, NULL, op_p); 1147 } 1148 EXPORT_SYMBOL(unregister_sysrq_key); 1149 1150 #ifdef CONFIG_PROC_FS 1151 /* 1152 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1153 * Normally, only the first character written is processed. 1154 * However, if the first character is an underscore, 1155 * all characters are processed. 1156 */ 1157 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1158 size_t count, loff_t *ppos) 1159 { 1160 bool bulk = false; 1161 size_t i; 1162 1163 for (i = 0; i < count; i++) { 1164 char c; 1165 1166 if (get_user(c, buf + i)) 1167 return -EFAULT; 1168 1169 if (c == '_') 1170 bulk = true; 1171 else 1172 __handle_sysrq(c, false); 1173 1174 if (!bulk) 1175 break; 1176 } 1177 1178 return count; 1179 } 1180 1181 static const struct proc_ops sysrq_trigger_proc_ops = { 1182 .proc_write = write_sysrq_trigger, 1183 .proc_lseek = noop_llseek, 1184 }; 1185 1186 static void sysrq_init_procfs(void) 1187 { 1188 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1189 &sysrq_trigger_proc_ops)) 1190 pr_err("Failed to register proc interface\n"); 1191 } 1192 1193 #else 1194 1195 static inline void sysrq_init_procfs(void) 1196 { 1197 } 1198 1199 #endif /* CONFIG_PROC_FS */ 1200 1201 static int __init sysrq_init(void) 1202 { 1203 sysrq_init_procfs(); 1204 1205 if (sysrq_on()) 1206 sysrq_register_handler(); 1207 1208 return 0; 1209 } 1210 device_initcall(sysrq_init); 1211