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(int key) 102 { 103 int i; 104 105 i = key - '0'; 106 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 107 pr_info("Loglevel set to %d\n", i); 108 console_loglevel = i; 109 } 110 static const struct sysrq_key_op sysrq_loglevel_op = { 111 .handler = sysrq_handle_loglevel, 112 .help_msg = "loglevel(0-9)", 113 .action_msg = "Changing Loglevel", 114 .enable_mask = SYSRQ_ENABLE_LOG, 115 }; 116 117 #ifdef CONFIG_VT 118 static void sysrq_handle_SAK(int key) 119 { 120 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 121 122 schedule_work(SAK_work); 123 } 124 static const struct sysrq_key_op sysrq_SAK_op = { 125 .handler = sysrq_handle_SAK, 126 .help_msg = "sak(k)", 127 .action_msg = "SAK", 128 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 129 }; 130 #else 131 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL) 132 #endif 133 134 #ifdef CONFIG_VT 135 static void sysrq_handle_unraw(int key) 136 { 137 vt_reset_unicode(fg_console); 138 } 139 140 static const struct sysrq_key_op sysrq_unraw_op = { 141 .handler = sysrq_handle_unraw, 142 .help_msg = "unraw(r)", 143 .action_msg = "Keyboard mode set to system default", 144 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 145 }; 146 #else 147 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL) 148 #endif /* CONFIG_VT */ 149 150 static void sysrq_handle_crash(int key) 151 { 152 /* release the RCU read lock before crashing */ 153 rcu_read_unlock(); 154 155 panic("sysrq triggered crash\n"); 156 } 157 static const struct sysrq_key_op sysrq_crash_op = { 158 .handler = sysrq_handle_crash, 159 .help_msg = "crash(c)", 160 .action_msg = "Trigger a crash", 161 .enable_mask = SYSRQ_ENABLE_DUMP, 162 }; 163 164 static void sysrq_handle_reboot(int key) 165 { 166 lockdep_off(); 167 local_irq_enable(); 168 emergency_restart(); 169 } 170 static const struct sysrq_key_op sysrq_reboot_op = { 171 .handler = sysrq_handle_reboot, 172 .help_msg = "reboot(b)", 173 .action_msg = "Resetting", 174 .enable_mask = SYSRQ_ENABLE_BOOT, 175 }; 176 177 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op; 178 179 static void sysrq_handle_sync(int key) 180 { 181 emergency_sync(); 182 } 183 static const struct sysrq_key_op sysrq_sync_op = { 184 .handler = sysrq_handle_sync, 185 .help_msg = "sync(s)", 186 .action_msg = "Emergency Sync", 187 .enable_mask = SYSRQ_ENABLE_SYNC, 188 }; 189 190 static void sysrq_handle_show_timers(int key) 191 { 192 sysrq_timer_list_show(); 193 } 194 195 static const struct sysrq_key_op sysrq_show_timers_op = { 196 .handler = sysrq_handle_show_timers, 197 .help_msg = "show-all-timers(q)", 198 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 199 }; 200 201 static void sysrq_handle_mountro(int key) 202 { 203 emergency_remount(); 204 } 205 static const struct sysrq_key_op sysrq_mountro_op = { 206 .handler = sysrq_handle_mountro, 207 .help_msg = "unmount(u)", 208 .action_msg = "Emergency Remount R/O", 209 .enable_mask = SYSRQ_ENABLE_REMOUNT, 210 }; 211 212 #ifdef CONFIG_LOCKDEP 213 static void sysrq_handle_showlocks(int key) 214 { 215 debug_show_all_locks(); 216 } 217 218 static const struct sysrq_key_op sysrq_showlocks_op = { 219 .handler = sysrq_handle_showlocks, 220 .help_msg = "show-all-locks(d)", 221 .action_msg = "Show Locks Held", 222 }; 223 #else 224 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL) 225 #endif 226 227 #ifdef CONFIG_SMP 228 static DEFINE_RAW_SPINLOCK(show_lock); 229 230 static void showacpu(void *dummy) 231 { 232 unsigned long flags; 233 234 /* Idle CPUs have no interesting backtrace. */ 235 if (idle_cpu(smp_processor_id())) { 236 pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id()); 237 return; 238 } 239 240 raw_spin_lock_irqsave(&show_lock, flags); 241 pr_info("CPU%d:\n", smp_processor_id()); 242 show_stack(NULL, NULL, KERN_INFO); 243 raw_spin_unlock_irqrestore(&show_lock, flags); 244 } 245 246 static void sysrq_showregs_othercpus(struct work_struct *dummy) 247 { 248 smp_call_function(showacpu, NULL, 0); 249 } 250 251 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 252 253 static void sysrq_handle_showallcpus(int key) 254 { 255 /* 256 * Fall back to the workqueue based printing if the 257 * backtrace printing did not succeed or the 258 * architecture has no support for it: 259 */ 260 if (!trigger_all_cpu_backtrace()) { 261 struct pt_regs *regs = NULL; 262 263 if (in_hardirq()) 264 regs = get_irq_regs(); 265 266 pr_info("CPU%d:\n", smp_processor_id()); 267 if (regs) 268 show_regs(regs); 269 else 270 show_stack(NULL, NULL, KERN_INFO); 271 272 schedule_work(&sysrq_showallcpus); 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(int 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(int 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(int 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(int 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(int key) 344 { 345 show_mem(0, NULL); 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(int 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(int 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(int 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(int 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(int 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(int key) 535 { 536 int retval; 537 538 if ((key >= '0') && (key <= '9')) 539 retval = key - '0'; 540 else if ((key >= 'a') && (key <= 'z')) 541 retval = key + 10 - 'a'; 542 else if ((key >= 'A') && (key <= 'Z')) 543 retval = key + 36 - 'A'; 544 else 545 retval = -1; 546 return retval; 547 } 548 549 /* 550 * get and put functions for the table, exposed to modules. 551 */ 552 static const struct sysrq_key_op *__sysrq_get_key_op(int key) 553 { 554 const struct sysrq_key_op *op_p = NULL; 555 int i; 556 557 i = sysrq_key_table_key2index(key); 558 if (i != -1) 559 op_p = sysrq_key_table[i]; 560 561 return op_p; 562 } 563 564 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p) 565 { 566 int i = sysrq_key_table_key2index(key); 567 568 if (i != -1) 569 sysrq_key_table[i] = op_p; 570 } 571 572 void __handle_sysrq(int key, bool check_mask) 573 { 574 const struct sysrq_key_op *op_p; 575 int orig_log_level; 576 int orig_suppress_printk; 577 int i; 578 579 orig_suppress_printk = suppress_printk; 580 suppress_printk = 0; 581 582 rcu_sysrq_start(); 583 rcu_read_lock(); 584 printk_prefer_direct_enter(); 585 /* 586 * Raise the apparent loglevel to maximum so that the sysrq header 587 * is shown to provide the user with positive feedback. We do not 588 * simply emit this at KERN_EMERG as that would change message 589 * routing in the consumers of /proc/kmsg. 590 */ 591 orig_log_level = console_loglevel; 592 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 593 594 op_p = __sysrq_get_key_op(key); 595 if (op_p) { 596 /* 597 * Should we check for enabled operations (/proc/sysrq-trigger 598 * should not) and is the invoked operation enabled? 599 */ 600 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 601 pr_info("%s\n", op_p->action_msg); 602 console_loglevel = orig_log_level; 603 op_p->handler(key); 604 } else { 605 pr_info("This sysrq operation is disabled.\n"); 606 console_loglevel = orig_log_level; 607 } 608 } else { 609 pr_info("HELP : "); 610 /* Only print the help msg once per handler */ 611 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 612 if (sysrq_key_table[i]) { 613 int j; 614 615 for (j = 0; sysrq_key_table[i] != 616 sysrq_key_table[j]; j++) 617 ; 618 if (j != i) 619 continue; 620 pr_cont("%s ", sysrq_key_table[i]->help_msg); 621 } 622 } 623 pr_cont("\n"); 624 console_loglevel = orig_log_level; 625 } 626 printk_prefer_direct_exit(); 627 rcu_read_unlock(); 628 rcu_sysrq_end(); 629 630 suppress_printk = orig_suppress_printk; 631 } 632 633 void handle_sysrq(int key) 634 { 635 if (sysrq_on()) 636 __handle_sysrq(key, true); 637 } 638 EXPORT_SYMBOL(handle_sysrq); 639 640 #ifdef CONFIG_INPUT 641 static int sysrq_reset_downtime_ms; 642 643 /* Simple translation table for the SysRq keys */ 644 static const unsigned char sysrq_xlate[KEY_CNT] = 645 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 646 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 647 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 648 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 649 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 650 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 651 "\r\000/"; /* 0x60 - 0x6f */ 652 653 struct sysrq_state { 654 struct input_handle handle; 655 struct work_struct reinject_work; 656 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 657 unsigned int alt; 658 unsigned int alt_use; 659 unsigned int shift; 660 unsigned int shift_use; 661 bool active; 662 bool need_reinject; 663 bool reinjecting; 664 665 /* reset sequence handling */ 666 bool reset_canceled; 667 bool reset_requested; 668 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 669 int reset_seq_len; 670 int reset_seq_cnt; 671 int reset_seq_version; 672 struct timer_list keyreset_timer; 673 }; 674 675 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 676 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 677 static unsigned int sysrq_reset_seq_len; 678 static unsigned int sysrq_reset_seq_version = 1; 679 680 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 681 { 682 int i; 683 unsigned short key; 684 685 state->reset_seq_cnt = 0; 686 687 for (i = 0; i < sysrq_reset_seq_len; i++) { 688 key = sysrq_reset_seq[i]; 689 690 if (key == KEY_RESERVED || key > KEY_MAX) 691 break; 692 693 __set_bit(key, state->reset_keybit); 694 state->reset_seq_len++; 695 696 if (test_bit(key, state->key_down)) 697 state->reset_seq_cnt++; 698 } 699 700 /* Disable reset until old keys are not released */ 701 state->reset_canceled = state->reset_seq_cnt != 0; 702 703 state->reset_seq_version = sysrq_reset_seq_version; 704 } 705 706 static void sysrq_do_reset(struct timer_list *t) 707 { 708 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 709 710 state->reset_requested = true; 711 712 orderly_reboot(); 713 } 714 715 static void sysrq_handle_reset_request(struct sysrq_state *state) 716 { 717 if (state->reset_requested) 718 __handle_sysrq(sysrq_xlate[KEY_B], false); 719 720 if (sysrq_reset_downtime_ms) 721 mod_timer(&state->keyreset_timer, 722 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 723 else 724 sysrq_do_reset(&state->keyreset_timer); 725 } 726 727 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 728 unsigned int code, int value) 729 { 730 if (!test_bit(code, state->reset_keybit)) { 731 /* 732 * Pressing any key _not_ in reset sequence cancels 733 * the reset sequence. Also cancelling the timer in 734 * case additional keys were pressed after a reset 735 * has been requested. 736 */ 737 if (value && state->reset_seq_cnt) { 738 state->reset_canceled = true; 739 del_timer(&state->keyreset_timer); 740 } 741 } else if (value == 0) { 742 /* 743 * Key release - all keys in the reset sequence need 744 * to be pressed and held for the reset timeout 745 * to hold. 746 */ 747 del_timer(&state->keyreset_timer); 748 749 if (--state->reset_seq_cnt == 0) 750 state->reset_canceled = false; 751 } else if (value == 1) { 752 /* key press, not autorepeat */ 753 if (++state->reset_seq_cnt == state->reset_seq_len && 754 !state->reset_canceled) { 755 sysrq_handle_reset_request(state); 756 } 757 } 758 } 759 760 #ifdef CONFIG_OF 761 static void sysrq_of_get_keyreset_config(void) 762 { 763 u32 key; 764 struct device_node *np; 765 struct property *prop; 766 const __be32 *p; 767 768 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 769 if (!np) { 770 pr_debug("No sysrq node found"); 771 return; 772 } 773 774 /* Reset in case a __weak definition was present */ 775 sysrq_reset_seq_len = 0; 776 777 of_property_for_each_u32(np, "keyset", prop, p, key) { 778 if (key == KEY_RESERVED || key > KEY_MAX || 779 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 780 break; 781 782 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 783 } 784 785 /* Get reset timeout if any. */ 786 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 787 788 of_node_put(np); 789 } 790 #else 791 static void sysrq_of_get_keyreset_config(void) 792 { 793 } 794 #endif 795 796 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 797 { 798 struct sysrq_state *sysrq = 799 container_of(work, struct sysrq_state, reinject_work); 800 struct input_handle *handle = &sysrq->handle; 801 unsigned int alt_code = sysrq->alt_use; 802 803 if (sysrq->need_reinject) { 804 /* we do not want the assignment to be reordered */ 805 sysrq->reinjecting = true; 806 mb(); 807 808 /* Simulate press and release of Alt + SysRq */ 809 input_inject_event(handle, EV_KEY, alt_code, 1); 810 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 811 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 812 813 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 814 input_inject_event(handle, EV_KEY, alt_code, 0); 815 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 816 817 mb(); 818 sysrq->reinjecting = false; 819 } 820 } 821 822 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 823 unsigned int code, int value) 824 { 825 bool was_active = sysrq->active; 826 bool suppress; 827 828 switch (code) { 829 830 case KEY_LEFTALT: 831 case KEY_RIGHTALT: 832 if (!value) { 833 /* One of ALTs is being released */ 834 if (sysrq->active && code == sysrq->alt_use) 835 sysrq->active = false; 836 837 sysrq->alt = KEY_RESERVED; 838 839 } else if (value != 2) { 840 sysrq->alt = code; 841 sysrq->need_reinject = false; 842 } 843 break; 844 845 case KEY_LEFTSHIFT: 846 case KEY_RIGHTSHIFT: 847 if (!value) 848 sysrq->shift = KEY_RESERVED; 849 else if (value != 2) 850 sysrq->shift = code; 851 if (sysrq->active) 852 sysrq->shift_use = sysrq->shift; 853 break; 854 855 case KEY_SYSRQ: 856 if (value == 1 && sysrq->alt != KEY_RESERVED) { 857 sysrq->active = true; 858 sysrq->alt_use = sysrq->alt; 859 /* either RESERVED (for released) or actual code */ 860 sysrq->shift_use = sysrq->shift; 861 /* 862 * If nothing else will be pressed we'll need 863 * to re-inject Alt-SysRq keysroke. 864 */ 865 sysrq->need_reinject = true; 866 } 867 868 /* 869 * Pretend that sysrq was never pressed at all. This 870 * is needed to properly handle KGDB which will try 871 * to release all keys after exiting debugger. If we 872 * do not clear key bit it KGDB will end up sending 873 * release events for Alt and SysRq, potentially 874 * triggering print screen function. 875 */ 876 if (sysrq->active) 877 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 878 879 break; 880 881 default: 882 if (sysrq->active && value && value != 2) { 883 unsigned char c = sysrq_xlate[code]; 884 885 sysrq->need_reinject = false; 886 if (sysrq->shift_use != KEY_RESERVED) 887 c = toupper(c); 888 __handle_sysrq(c, true); 889 } 890 break; 891 } 892 893 suppress = sysrq->active; 894 895 if (!sysrq->active) { 896 897 /* 898 * See if reset sequence has changed since the last time. 899 */ 900 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 901 sysrq_parse_reset_sequence(sysrq); 902 903 /* 904 * If we are not suppressing key presses keep track of 905 * keyboard state so we can release keys that have been 906 * pressed before entering SysRq mode. 907 */ 908 if (value) 909 set_bit(code, sysrq->key_down); 910 else 911 clear_bit(code, sysrq->key_down); 912 913 if (was_active) 914 schedule_work(&sysrq->reinject_work); 915 916 /* Check for reset sequence */ 917 sysrq_detect_reset_sequence(sysrq, code, value); 918 919 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 920 /* 921 * Pass on release events for keys that was pressed before 922 * entering SysRq mode. 923 */ 924 suppress = false; 925 } 926 927 return suppress; 928 } 929 930 static bool sysrq_filter(struct input_handle *handle, 931 unsigned int type, unsigned int code, int value) 932 { 933 struct sysrq_state *sysrq = handle->private; 934 bool suppress; 935 936 /* 937 * Do not filter anything if we are in the process of re-injecting 938 * Alt+SysRq combination. 939 */ 940 if (sysrq->reinjecting) 941 return false; 942 943 switch (type) { 944 945 case EV_SYN: 946 suppress = false; 947 break; 948 949 case EV_KEY: 950 suppress = sysrq_handle_keypress(sysrq, code, value); 951 break; 952 953 default: 954 suppress = sysrq->active; 955 break; 956 } 957 958 return suppress; 959 } 960 961 static int sysrq_connect(struct input_handler *handler, 962 struct input_dev *dev, 963 const struct input_device_id *id) 964 { 965 struct sysrq_state *sysrq; 966 int error; 967 968 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 969 if (!sysrq) 970 return -ENOMEM; 971 972 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 973 974 sysrq->handle.dev = dev; 975 sysrq->handle.handler = handler; 976 sysrq->handle.name = "sysrq"; 977 sysrq->handle.private = sysrq; 978 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 979 980 error = input_register_handle(&sysrq->handle); 981 if (error) { 982 pr_err("Failed to register input sysrq handler, error %d\n", 983 error); 984 goto err_free; 985 } 986 987 error = input_open_device(&sysrq->handle); 988 if (error) { 989 pr_err("Failed to open input device, error %d\n", error); 990 goto err_unregister; 991 } 992 993 return 0; 994 995 err_unregister: 996 input_unregister_handle(&sysrq->handle); 997 err_free: 998 kfree(sysrq); 999 return error; 1000 } 1001 1002 static void sysrq_disconnect(struct input_handle *handle) 1003 { 1004 struct sysrq_state *sysrq = handle->private; 1005 1006 input_close_device(handle); 1007 cancel_work_sync(&sysrq->reinject_work); 1008 del_timer_sync(&sysrq->keyreset_timer); 1009 input_unregister_handle(handle); 1010 kfree(sysrq); 1011 } 1012 1013 /* 1014 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 1015 * keyboards have SysRq key predefined and so user may add it to keymap 1016 * later, but we expect all such keyboards to have left alt. 1017 */ 1018 static const struct input_device_id sysrq_ids[] = { 1019 { 1020 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 1021 INPUT_DEVICE_ID_MATCH_KEYBIT, 1022 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 1023 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 1024 }, 1025 { }, 1026 }; 1027 1028 static struct input_handler sysrq_handler = { 1029 .filter = sysrq_filter, 1030 .connect = sysrq_connect, 1031 .disconnect = sysrq_disconnect, 1032 .name = "sysrq", 1033 .id_table = sysrq_ids, 1034 }; 1035 1036 static inline void sysrq_register_handler(void) 1037 { 1038 int error; 1039 1040 sysrq_of_get_keyreset_config(); 1041 1042 error = input_register_handler(&sysrq_handler); 1043 if (error) 1044 pr_err("Failed to register input handler, error %d", error); 1045 } 1046 1047 static inline void sysrq_unregister_handler(void) 1048 { 1049 input_unregister_handler(&sysrq_handler); 1050 } 1051 1052 static int sysrq_reset_seq_param_set(const char *buffer, 1053 const struct kernel_param *kp) 1054 { 1055 unsigned long val; 1056 int error; 1057 1058 error = kstrtoul(buffer, 0, &val); 1059 if (error < 0) 1060 return error; 1061 1062 if (val > KEY_MAX) 1063 return -EINVAL; 1064 1065 *((unsigned short *)kp->arg) = val; 1066 sysrq_reset_seq_version++; 1067 1068 return 0; 1069 } 1070 1071 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1072 .get = param_get_ushort, 1073 .set = sysrq_reset_seq_param_set, 1074 }; 1075 1076 #define param_check_sysrq_reset_seq(name, p) \ 1077 __param_check(name, p, unsigned short) 1078 1079 /* 1080 * not really modular, but the easiest way to keep compat with existing 1081 * bootargs behaviour is to continue using module_param here. 1082 */ 1083 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1084 &sysrq_reset_seq_len, 0644); 1085 1086 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1087 1088 #else 1089 1090 static inline void sysrq_register_handler(void) 1091 { 1092 } 1093 1094 static inline void sysrq_unregister_handler(void) 1095 { 1096 } 1097 1098 #endif /* CONFIG_INPUT */ 1099 1100 int sysrq_toggle_support(int enable_mask) 1101 { 1102 bool was_enabled = sysrq_on(); 1103 1104 sysrq_enabled = enable_mask; 1105 1106 if (was_enabled != sysrq_on()) { 1107 if (sysrq_on()) 1108 sysrq_register_handler(); 1109 else 1110 sysrq_unregister_handler(); 1111 } 1112 1113 return 0; 1114 } 1115 EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1116 1117 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p, 1118 const struct sysrq_key_op *remove_op_p) 1119 { 1120 int retval; 1121 1122 spin_lock(&sysrq_key_table_lock); 1123 if (__sysrq_get_key_op(key) == remove_op_p) { 1124 __sysrq_put_key_op(key, insert_op_p); 1125 retval = 0; 1126 } else { 1127 retval = -1; 1128 } 1129 spin_unlock(&sysrq_key_table_lock); 1130 1131 /* 1132 * A concurrent __handle_sysrq either got the old op or the new op. 1133 * Wait for it to go away before returning, so the code for an old 1134 * op is not freed (eg. on module unload) while it is in use. 1135 */ 1136 synchronize_rcu(); 1137 1138 return retval; 1139 } 1140 1141 int register_sysrq_key(int key, const struct sysrq_key_op *op_p) 1142 { 1143 return __sysrq_swap_key_ops(key, op_p, NULL); 1144 } 1145 EXPORT_SYMBOL(register_sysrq_key); 1146 1147 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p) 1148 { 1149 return __sysrq_swap_key_ops(key, NULL, op_p); 1150 } 1151 EXPORT_SYMBOL(unregister_sysrq_key); 1152 1153 #ifdef CONFIG_PROC_FS 1154 /* 1155 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1156 */ 1157 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1158 size_t count, loff_t *ppos) 1159 { 1160 if (count) { 1161 char c; 1162 1163 if (get_user(c, buf)) 1164 return -EFAULT; 1165 __handle_sysrq(c, false); 1166 } 1167 1168 return count; 1169 } 1170 1171 static const struct proc_ops sysrq_trigger_proc_ops = { 1172 .proc_write = write_sysrq_trigger, 1173 .proc_lseek = noop_llseek, 1174 }; 1175 1176 static void sysrq_init_procfs(void) 1177 { 1178 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1179 &sysrq_trigger_proc_ops)) 1180 pr_err("Failed to register proc interface\n"); 1181 } 1182 1183 #else 1184 1185 static inline void sysrq_init_procfs(void) 1186 { 1187 } 1188 1189 #endif /* CONFIG_PROC_FS */ 1190 1191 static int __init sysrq_init(void) 1192 { 1193 sysrq_init_procfs(); 1194 1195 if (sysrq_on()) 1196 sysrq_register_handler(); 1197 1198 return 0; 1199 } 1200 device_initcall(sysrq_init); 1201