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 /* 585 * Raise the apparent loglevel to maximum so that the sysrq header 586 * is shown to provide the user with positive feedback. We do not 587 * simply emit this at KERN_EMERG as that would change message 588 * routing in the consumers of /proc/kmsg. 589 */ 590 orig_log_level = console_loglevel; 591 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 592 593 op_p = __sysrq_get_key_op(key); 594 if (op_p) { 595 /* 596 * Should we check for enabled operations (/proc/sysrq-trigger 597 * should not) and is the invoked operation enabled? 598 */ 599 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 600 pr_info("%s\n", op_p->action_msg); 601 console_loglevel = orig_log_level; 602 op_p->handler(key); 603 } else { 604 pr_info("This sysrq operation is disabled.\n"); 605 console_loglevel = orig_log_level; 606 } 607 } else { 608 pr_info("HELP : "); 609 /* Only print the help msg once per handler */ 610 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 611 if (sysrq_key_table[i]) { 612 int j; 613 614 for (j = 0; sysrq_key_table[i] != 615 sysrq_key_table[j]; j++) 616 ; 617 if (j != i) 618 continue; 619 pr_cont("%s ", sysrq_key_table[i]->help_msg); 620 } 621 } 622 pr_cont("\n"); 623 console_loglevel = orig_log_level; 624 } 625 rcu_read_unlock(); 626 rcu_sysrq_end(); 627 628 suppress_printk = orig_suppress_printk; 629 } 630 631 void handle_sysrq(int key) 632 { 633 if (sysrq_on()) 634 __handle_sysrq(key, true); 635 } 636 EXPORT_SYMBOL(handle_sysrq); 637 638 #ifdef CONFIG_INPUT 639 static int sysrq_reset_downtime_ms; 640 641 /* Simple translation table for the SysRq keys */ 642 static const unsigned char sysrq_xlate[KEY_CNT] = 643 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 644 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 645 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 646 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 647 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 648 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 649 "\r\000/"; /* 0x60 - 0x6f */ 650 651 struct sysrq_state { 652 struct input_handle handle; 653 struct work_struct reinject_work; 654 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 655 unsigned int alt; 656 unsigned int alt_use; 657 unsigned int shift; 658 unsigned int shift_use; 659 bool active; 660 bool need_reinject; 661 bool reinjecting; 662 663 /* reset sequence handling */ 664 bool reset_canceled; 665 bool reset_requested; 666 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 667 int reset_seq_len; 668 int reset_seq_cnt; 669 int reset_seq_version; 670 struct timer_list keyreset_timer; 671 }; 672 673 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 674 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 675 static unsigned int sysrq_reset_seq_len; 676 static unsigned int sysrq_reset_seq_version = 1; 677 678 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 679 { 680 int i; 681 unsigned short key; 682 683 state->reset_seq_cnt = 0; 684 685 for (i = 0; i < sysrq_reset_seq_len; i++) { 686 key = sysrq_reset_seq[i]; 687 688 if (key == KEY_RESERVED || key > KEY_MAX) 689 break; 690 691 __set_bit(key, state->reset_keybit); 692 state->reset_seq_len++; 693 694 if (test_bit(key, state->key_down)) 695 state->reset_seq_cnt++; 696 } 697 698 /* Disable reset until old keys are not released */ 699 state->reset_canceled = state->reset_seq_cnt != 0; 700 701 state->reset_seq_version = sysrq_reset_seq_version; 702 } 703 704 static void sysrq_do_reset(struct timer_list *t) 705 { 706 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 707 708 state->reset_requested = true; 709 710 orderly_reboot(); 711 } 712 713 static void sysrq_handle_reset_request(struct sysrq_state *state) 714 { 715 if (state->reset_requested) 716 __handle_sysrq(sysrq_xlate[KEY_B], false); 717 718 if (sysrq_reset_downtime_ms) 719 mod_timer(&state->keyreset_timer, 720 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 721 else 722 sysrq_do_reset(&state->keyreset_timer); 723 } 724 725 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 726 unsigned int code, int value) 727 { 728 if (!test_bit(code, state->reset_keybit)) { 729 /* 730 * Pressing any key _not_ in reset sequence cancels 731 * the reset sequence. Also cancelling the timer in 732 * case additional keys were pressed after a reset 733 * has been requested. 734 */ 735 if (value && state->reset_seq_cnt) { 736 state->reset_canceled = true; 737 del_timer(&state->keyreset_timer); 738 } 739 } else if (value == 0) { 740 /* 741 * Key release - all keys in the reset sequence need 742 * to be pressed and held for the reset timeout 743 * to hold. 744 */ 745 del_timer(&state->keyreset_timer); 746 747 if (--state->reset_seq_cnt == 0) 748 state->reset_canceled = false; 749 } else if (value == 1) { 750 /* key press, not autorepeat */ 751 if (++state->reset_seq_cnt == state->reset_seq_len && 752 !state->reset_canceled) { 753 sysrq_handle_reset_request(state); 754 } 755 } 756 } 757 758 #ifdef CONFIG_OF 759 static void sysrq_of_get_keyreset_config(void) 760 { 761 u32 key; 762 struct device_node *np; 763 struct property *prop; 764 const __be32 *p; 765 766 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 767 if (!np) { 768 pr_debug("No sysrq node found"); 769 return; 770 } 771 772 /* Reset in case a __weak definition was present */ 773 sysrq_reset_seq_len = 0; 774 775 of_property_for_each_u32(np, "keyset", prop, p, key) { 776 if (key == KEY_RESERVED || key > KEY_MAX || 777 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 778 break; 779 780 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 781 } 782 783 /* Get reset timeout if any. */ 784 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 785 786 of_node_put(np); 787 } 788 #else 789 static void sysrq_of_get_keyreset_config(void) 790 { 791 } 792 #endif 793 794 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 795 { 796 struct sysrq_state *sysrq = 797 container_of(work, struct sysrq_state, reinject_work); 798 struct input_handle *handle = &sysrq->handle; 799 unsigned int alt_code = sysrq->alt_use; 800 801 if (sysrq->need_reinject) { 802 /* we do not want the assignment to be reordered */ 803 sysrq->reinjecting = true; 804 mb(); 805 806 /* Simulate press and release of Alt + SysRq */ 807 input_inject_event(handle, EV_KEY, alt_code, 1); 808 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 809 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 810 811 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 812 input_inject_event(handle, EV_KEY, alt_code, 0); 813 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 814 815 mb(); 816 sysrq->reinjecting = false; 817 } 818 } 819 820 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 821 unsigned int code, int value) 822 { 823 bool was_active = sysrq->active; 824 bool suppress; 825 826 switch (code) { 827 828 case KEY_LEFTALT: 829 case KEY_RIGHTALT: 830 if (!value) { 831 /* One of ALTs is being released */ 832 if (sysrq->active && code == sysrq->alt_use) 833 sysrq->active = false; 834 835 sysrq->alt = KEY_RESERVED; 836 837 } else if (value != 2) { 838 sysrq->alt = code; 839 sysrq->need_reinject = false; 840 } 841 break; 842 843 case KEY_LEFTSHIFT: 844 case KEY_RIGHTSHIFT: 845 if (!value) 846 sysrq->shift = KEY_RESERVED; 847 else if (value != 2) 848 sysrq->shift = code; 849 if (sysrq->active) 850 sysrq->shift_use = sysrq->shift; 851 break; 852 853 case KEY_SYSRQ: 854 if (value == 1 && sysrq->alt != KEY_RESERVED) { 855 sysrq->active = true; 856 sysrq->alt_use = sysrq->alt; 857 /* either RESERVED (for released) or actual code */ 858 sysrq->shift_use = sysrq->shift; 859 /* 860 * If nothing else will be pressed we'll need 861 * to re-inject Alt-SysRq keysroke. 862 */ 863 sysrq->need_reinject = true; 864 } 865 866 /* 867 * Pretend that sysrq was never pressed at all. This 868 * is needed to properly handle KGDB which will try 869 * to release all keys after exiting debugger. If we 870 * do not clear key bit it KGDB will end up sending 871 * release events for Alt and SysRq, potentially 872 * triggering print screen function. 873 */ 874 if (sysrq->active) 875 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 876 877 break; 878 879 default: 880 if (sysrq->active && value && value != 2) { 881 unsigned char c = sysrq_xlate[code]; 882 883 sysrq->need_reinject = false; 884 if (sysrq->shift_use != KEY_RESERVED) 885 c = toupper(c); 886 __handle_sysrq(c, true); 887 } 888 break; 889 } 890 891 suppress = sysrq->active; 892 893 if (!sysrq->active) { 894 895 /* 896 * See if reset sequence has changed since the last time. 897 */ 898 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 899 sysrq_parse_reset_sequence(sysrq); 900 901 /* 902 * If we are not suppressing key presses keep track of 903 * keyboard state so we can release keys that have been 904 * pressed before entering SysRq mode. 905 */ 906 if (value) 907 set_bit(code, sysrq->key_down); 908 else 909 clear_bit(code, sysrq->key_down); 910 911 if (was_active) 912 schedule_work(&sysrq->reinject_work); 913 914 /* Check for reset sequence */ 915 sysrq_detect_reset_sequence(sysrq, code, value); 916 917 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 918 /* 919 * Pass on release events for keys that was pressed before 920 * entering SysRq mode. 921 */ 922 suppress = false; 923 } 924 925 return suppress; 926 } 927 928 static bool sysrq_filter(struct input_handle *handle, 929 unsigned int type, unsigned int code, int value) 930 { 931 struct sysrq_state *sysrq = handle->private; 932 bool suppress; 933 934 /* 935 * Do not filter anything if we are in the process of re-injecting 936 * Alt+SysRq combination. 937 */ 938 if (sysrq->reinjecting) 939 return false; 940 941 switch (type) { 942 943 case EV_SYN: 944 suppress = false; 945 break; 946 947 case EV_KEY: 948 suppress = sysrq_handle_keypress(sysrq, code, value); 949 break; 950 951 default: 952 suppress = sysrq->active; 953 break; 954 } 955 956 return suppress; 957 } 958 959 static int sysrq_connect(struct input_handler *handler, 960 struct input_dev *dev, 961 const struct input_device_id *id) 962 { 963 struct sysrq_state *sysrq; 964 int error; 965 966 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 967 if (!sysrq) 968 return -ENOMEM; 969 970 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 971 972 sysrq->handle.dev = dev; 973 sysrq->handle.handler = handler; 974 sysrq->handle.name = "sysrq"; 975 sysrq->handle.private = sysrq; 976 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 977 978 error = input_register_handle(&sysrq->handle); 979 if (error) { 980 pr_err("Failed to register input sysrq handler, error %d\n", 981 error); 982 goto err_free; 983 } 984 985 error = input_open_device(&sysrq->handle); 986 if (error) { 987 pr_err("Failed to open input device, error %d\n", error); 988 goto err_unregister; 989 } 990 991 return 0; 992 993 err_unregister: 994 input_unregister_handle(&sysrq->handle); 995 err_free: 996 kfree(sysrq); 997 return error; 998 } 999 1000 static void sysrq_disconnect(struct input_handle *handle) 1001 { 1002 struct sysrq_state *sysrq = handle->private; 1003 1004 input_close_device(handle); 1005 cancel_work_sync(&sysrq->reinject_work); 1006 timer_shutdown_sync(&sysrq->keyreset_timer); 1007 input_unregister_handle(handle); 1008 kfree(sysrq); 1009 } 1010 1011 /* 1012 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 1013 * keyboards have SysRq key predefined and so user may add it to keymap 1014 * later, but we expect all such keyboards to have left alt. 1015 */ 1016 static const struct input_device_id sysrq_ids[] = { 1017 { 1018 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 1019 INPUT_DEVICE_ID_MATCH_KEYBIT, 1020 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 1021 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 1022 }, 1023 { }, 1024 }; 1025 1026 static struct input_handler sysrq_handler = { 1027 .filter = sysrq_filter, 1028 .connect = sysrq_connect, 1029 .disconnect = sysrq_disconnect, 1030 .name = "sysrq", 1031 .id_table = sysrq_ids, 1032 }; 1033 1034 static inline void sysrq_register_handler(void) 1035 { 1036 int error; 1037 1038 sysrq_of_get_keyreset_config(); 1039 1040 error = input_register_handler(&sysrq_handler); 1041 if (error) 1042 pr_err("Failed to register input handler, error %d", error); 1043 } 1044 1045 static inline void sysrq_unregister_handler(void) 1046 { 1047 input_unregister_handler(&sysrq_handler); 1048 } 1049 1050 static int sysrq_reset_seq_param_set(const char *buffer, 1051 const struct kernel_param *kp) 1052 { 1053 unsigned long val; 1054 int error; 1055 1056 error = kstrtoul(buffer, 0, &val); 1057 if (error < 0) 1058 return error; 1059 1060 if (val > KEY_MAX) 1061 return -EINVAL; 1062 1063 *((unsigned short *)kp->arg) = val; 1064 sysrq_reset_seq_version++; 1065 1066 return 0; 1067 } 1068 1069 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1070 .get = param_get_ushort, 1071 .set = sysrq_reset_seq_param_set, 1072 }; 1073 1074 #define param_check_sysrq_reset_seq(name, p) \ 1075 __param_check(name, p, unsigned short) 1076 1077 /* 1078 * not really modular, but the easiest way to keep compat with existing 1079 * bootargs behaviour is to continue using module_param here. 1080 */ 1081 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1082 &sysrq_reset_seq_len, 0644); 1083 1084 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1085 1086 #else 1087 1088 static inline void sysrq_register_handler(void) 1089 { 1090 } 1091 1092 static inline void sysrq_unregister_handler(void) 1093 { 1094 } 1095 1096 #endif /* CONFIG_INPUT */ 1097 1098 int sysrq_toggle_support(int enable_mask) 1099 { 1100 bool was_enabled = sysrq_on(); 1101 1102 sysrq_enabled = enable_mask; 1103 1104 if (was_enabled != sysrq_on()) { 1105 if (sysrq_on()) 1106 sysrq_register_handler(); 1107 else 1108 sysrq_unregister_handler(); 1109 } 1110 1111 return 0; 1112 } 1113 EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1114 1115 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p, 1116 const struct sysrq_key_op *remove_op_p) 1117 { 1118 int retval; 1119 1120 spin_lock(&sysrq_key_table_lock); 1121 if (__sysrq_get_key_op(key) == remove_op_p) { 1122 __sysrq_put_key_op(key, insert_op_p); 1123 retval = 0; 1124 } else { 1125 retval = -1; 1126 } 1127 spin_unlock(&sysrq_key_table_lock); 1128 1129 /* 1130 * A concurrent __handle_sysrq either got the old op or the new op. 1131 * Wait for it to go away before returning, so the code for an old 1132 * op is not freed (eg. on module unload) while it is in use. 1133 */ 1134 synchronize_rcu(); 1135 1136 return retval; 1137 } 1138 1139 int register_sysrq_key(int key, const struct sysrq_key_op *op_p) 1140 { 1141 return __sysrq_swap_key_ops(key, op_p, NULL); 1142 } 1143 EXPORT_SYMBOL(register_sysrq_key); 1144 1145 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p) 1146 { 1147 return __sysrq_swap_key_ops(key, NULL, op_p); 1148 } 1149 EXPORT_SYMBOL(unregister_sysrq_key); 1150 1151 #ifdef CONFIG_PROC_FS 1152 /* 1153 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1154 */ 1155 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1156 size_t count, loff_t *ppos) 1157 { 1158 if (count) { 1159 char c; 1160 1161 if (get_user(c, buf)) 1162 return -EFAULT; 1163 __handle_sysrq(c, false); 1164 } 1165 1166 return count; 1167 } 1168 1169 static const struct proc_ops sysrq_trigger_proc_ops = { 1170 .proc_write = write_sysrq_trigger, 1171 .proc_lseek = noop_llseek, 1172 }; 1173 1174 static void sysrq_init_procfs(void) 1175 { 1176 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1177 &sysrq_trigger_proc_ops)) 1178 pr_err("Failed to register proc interface\n"); 1179 } 1180 1181 #else 1182 1183 static inline void sysrq_init_procfs(void) 1184 { 1185 } 1186 1187 #endif /* CONFIG_PROC_FS */ 1188 1189 static int __init sysrq_init(void) 1190 { 1191 sysrq_init_procfs(); 1192 1193 if (sysrq_on()) 1194 sysrq_register_handler(); 1195 1196 return 0; 1197 } 1198 device_initcall(sysrq_init); 1199