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