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 return; 237 238 raw_spin_lock_irqsave(&show_lock, flags); 239 pr_info("CPU%d:\n", smp_processor_id()); 240 show_stack(NULL, NULL, KERN_INFO); 241 raw_spin_unlock_irqrestore(&show_lock, flags); 242 } 243 244 static void sysrq_showregs_othercpus(struct work_struct *dummy) 245 { 246 smp_call_function(showacpu, NULL, 0); 247 } 248 249 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 250 251 static void sysrq_handle_showallcpus(int key) 252 { 253 /* 254 * Fall back to the workqueue based printing if the 255 * backtrace printing did not succeed or the 256 * architecture has no support for it: 257 */ 258 if (!trigger_all_cpu_backtrace()) { 259 struct pt_regs *regs = NULL; 260 261 if (in_hardirq()) 262 regs = get_irq_regs(); 263 if (regs) { 264 pr_info("CPU%d:\n", smp_processor_id()); 265 show_regs(regs); 266 } 267 schedule_work(&sysrq_showallcpus); 268 } 269 } 270 271 static const struct sysrq_key_op sysrq_showallcpus_op = { 272 .handler = sysrq_handle_showallcpus, 273 .help_msg = "show-backtrace-all-active-cpus(l)", 274 .action_msg = "Show backtrace of all active CPUs", 275 .enable_mask = SYSRQ_ENABLE_DUMP, 276 }; 277 #endif 278 279 static void sysrq_handle_showregs(int key) 280 { 281 struct pt_regs *regs = NULL; 282 283 if (in_hardirq()) 284 regs = get_irq_regs(); 285 if (regs) 286 show_regs(regs); 287 perf_event_print_debug(); 288 } 289 static const struct sysrq_key_op sysrq_showregs_op = { 290 .handler = sysrq_handle_showregs, 291 .help_msg = "show-registers(p)", 292 .action_msg = "Show Regs", 293 .enable_mask = SYSRQ_ENABLE_DUMP, 294 }; 295 296 static void sysrq_handle_showstate(int key) 297 { 298 show_state(); 299 show_all_workqueues(); 300 } 301 static const struct sysrq_key_op sysrq_showstate_op = { 302 .handler = sysrq_handle_showstate, 303 .help_msg = "show-task-states(t)", 304 .action_msg = "Show State", 305 .enable_mask = SYSRQ_ENABLE_DUMP, 306 }; 307 308 static void sysrq_handle_showstate_blocked(int key) 309 { 310 show_state_filter(TASK_UNINTERRUPTIBLE); 311 } 312 static const struct sysrq_key_op sysrq_showstate_blocked_op = { 313 .handler = sysrq_handle_showstate_blocked, 314 .help_msg = "show-blocked-tasks(w)", 315 .action_msg = "Show Blocked State", 316 .enable_mask = SYSRQ_ENABLE_DUMP, 317 }; 318 319 #ifdef CONFIG_TRACING 320 #include <linux/ftrace.h> 321 322 static void sysrq_ftrace_dump(int key) 323 { 324 ftrace_dump(DUMP_ALL); 325 } 326 static const struct sysrq_key_op sysrq_ftrace_dump_op = { 327 .handler = sysrq_ftrace_dump, 328 .help_msg = "dump-ftrace-buffer(z)", 329 .action_msg = "Dump ftrace buffer", 330 .enable_mask = SYSRQ_ENABLE_DUMP, 331 }; 332 #else 333 #define sysrq_ftrace_dump_op (*(const struct sysrq_key_op *)NULL) 334 #endif 335 336 static void sysrq_handle_showmem(int key) 337 { 338 show_mem(0, NULL); 339 } 340 static const struct sysrq_key_op sysrq_showmem_op = { 341 .handler = sysrq_handle_showmem, 342 .help_msg = "show-memory-usage(m)", 343 .action_msg = "Show Memory", 344 .enable_mask = SYSRQ_ENABLE_DUMP, 345 }; 346 347 /* 348 * Signal sysrq helper function. Sends a signal to all user processes. 349 */ 350 static void send_sig_all(int sig) 351 { 352 struct task_struct *p; 353 354 read_lock(&tasklist_lock); 355 for_each_process(p) { 356 if (p->flags & PF_KTHREAD) 357 continue; 358 if (is_global_init(p)) 359 continue; 360 361 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX); 362 } 363 read_unlock(&tasklist_lock); 364 } 365 366 static void sysrq_handle_term(int key) 367 { 368 send_sig_all(SIGTERM); 369 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 370 } 371 static const struct sysrq_key_op sysrq_term_op = { 372 .handler = sysrq_handle_term, 373 .help_msg = "terminate-all-tasks(e)", 374 .action_msg = "Terminate All Tasks", 375 .enable_mask = SYSRQ_ENABLE_SIGNAL, 376 }; 377 378 static void moom_callback(struct work_struct *ignored) 379 { 380 const gfp_t gfp_mask = GFP_KERNEL; 381 struct oom_control oc = { 382 .zonelist = node_zonelist(first_memory_node, gfp_mask), 383 .nodemask = NULL, 384 .memcg = NULL, 385 .gfp_mask = gfp_mask, 386 .order = -1, 387 }; 388 389 mutex_lock(&oom_lock); 390 if (!out_of_memory(&oc)) 391 pr_info("OOM request ignored. No task eligible\n"); 392 mutex_unlock(&oom_lock); 393 } 394 395 static DECLARE_WORK(moom_work, moom_callback); 396 397 static void sysrq_handle_moom(int key) 398 { 399 schedule_work(&moom_work); 400 } 401 static const struct sysrq_key_op sysrq_moom_op = { 402 .handler = sysrq_handle_moom, 403 .help_msg = "memory-full-oom-kill(f)", 404 .action_msg = "Manual OOM execution", 405 .enable_mask = SYSRQ_ENABLE_SIGNAL, 406 }; 407 408 static void sysrq_handle_thaw(int key) 409 { 410 emergency_thaw_all(); 411 } 412 static const struct sysrq_key_op sysrq_thaw_op = { 413 .handler = sysrq_handle_thaw, 414 .help_msg = "thaw-filesystems(j)", 415 .action_msg = "Emergency Thaw of all frozen filesystems", 416 .enable_mask = SYSRQ_ENABLE_SIGNAL, 417 }; 418 419 static void sysrq_handle_kill(int key) 420 { 421 send_sig_all(SIGKILL); 422 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 423 } 424 static const struct sysrq_key_op sysrq_kill_op = { 425 .handler = sysrq_handle_kill, 426 .help_msg = "kill-all-tasks(i)", 427 .action_msg = "Kill All Tasks", 428 .enable_mask = SYSRQ_ENABLE_SIGNAL, 429 }; 430 431 static void sysrq_handle_unrt(int key) 432 { 433 normalize_rt_tasks(); 434 } 435 static const struct sysrq_key_op sysrq_unrt_op = { 436 .handler = sysrq_handle_unrt, 437 .help_msg = "nice-all-RT-tasks(n)", 438 .action_msg = "Nice All RT Tasks", 439 .enable_mask = SYSRQ_ENABLE_RTNICE, 440 }; 441 442 /* Key Operations table and lock */ 443 static DEFINE_SPINLOCK(sysrq_key_table_lock); 444 445 static const struct sysrq_key_op *sysrq_key_table[62] = { 446 &sysrq_loglevel_op, /* 0 */ 447 &sysrq_loglevel_op, /* 1 */ 448 &sysrq_loglevel_op, /* 2 */ 449 &sysrq_loglevel_op, /* 3 */ 450 &sysrq_loglevel_op, /* 4 */ 451 &sysrq_loglevel_op, /* 5 */ 452 &sysrq_loglevel_op, /* 6 */ 453 &sysrq_loglevel_op, /* 7 */ 454 &sysrq_loglevel_op, /* 8 */ 455 &sysrq_loglevel_op, /* 9 */ 456 457 /* 458 * a: Don't use for system provided sysrqs, it is handled specially on 459 * sparc and will never arrive. 460 */ 461 NULL, /* a */ 462 &sysrq_reboot_op, /* b */ 463 &sysrq_crash_op, /* c */ 464 &sysrq_showlocks_op, /* d */ 465 &sysrq_term_op, /* e */ 466 &sysrq_moom_op, /* f */ 467 /* g: May be registered for the kernel debugger */ 468 NULL, /* g */ 469 NULL, /* h - reserved for help */ 470 &sysrq_kill_op, /* i */ 471 #ifdef CONFIG_BLOCK 472 &sysrq_thaw_op, /* j */ 473 #else 474 NULL, /* j */ 475 #endif 476 &sysrq_SAK_op, /* k */ 477 #ifdef CONFIG_SMP 478 &sysrq_showallcpus_op, /* l */ 479 #else 480 NULL, /* l */ 481 #endif 482 &sysrq_showmem_op, /* m */ 483 &sysrq_unrt_op, /* n */ 484 /* o: This will often be registered as 'Off' at init time */ 485 NULL, /* o */ 486 &sysrq_showregs_op, /* p */ 487 &sysrq_show_timers_op, /* q */ 488 &sysrq_unraw_op, /* r */ 489 &sysrq_sync_op, /* s */ 490 &sysrq_showstate_op, /* t */ 491 &sysrq_mountro_op, /* u */ 492 /* v: May be registered for frame buffer console restore */ 493 NULL, /* v */ 494 &sysrq_showstate_blocked_op, /* w */ 495 /* x: May be registered on mips for TLB dump */ 496 /* x: May be registered on ppc/powerpc for xmon */ 497 /* x: May be registered on sparc64 for global PMU dump */ 498 NULL, /* x */ 499 /* y: May be registered on sparc64 for global register dump */ 500 NULL, /* y */ 501 &sysrq_ftrace_dump_op, /* z */ 502 NULL, /* A */ 503 NULL, /* B */ 504 NULL, /* C */ 505 NULL, /* D */ 506 NULL, /* E */ 507 NULL, /* F */ 508 NULL, /* G */ 509 NULL, /* H */ 510 NULL, /* I */ 511 NULL, /* J */ 512 NULL, /* K */ 513 NULL, /* L */ 514 NULL, /* M */ 515 NULL, /* N */ 516 NULL, /* O */ 517 NULL, /* P */ 518 NULL, /* Q */ 519 NULL, /* R */ 520 NULL, /* S */ 521 NULL, /* T */ 522 NULL, /* U */ 523 NULL, /* V */ 524 NULL, /* W */ 525 NULL, /* X */ 526 NULL, /* Y */ 527 NULL, /* Z */ 528 }; 529 530 /* key2index calculation, -1 on invalid index */ 531 static int sysrq_key_table_key2index(int key) 532 { 533 int retval; 534 535 if ((key >= '0') && (key <= '9')) 536 retval = key - '0'; 537 else if ((key >= 'a') && (key <= 'z')) 538 retval = key + 10 - 'a'; 539 else if ((key >= 'A') && (key <= 'Z')) 540 retval = key + 36 - 'A'; 541 else 542 retval = -1; 543 return retval; 544 } 545 546 /* 547 * get and put functions for the table, exposed to modules. 548 */ 549 static const struct sysrq_key_op *__sysrq_get_key_op(int key) 550 { 551 const struct sysrq_key_op *op_p = NULL; 552 int i; 553 554 i = sysrq_key_table_key2index(key); 555 if (i != -1) 556 op_p = sysrq_key_table[i]; 557 558 return op_p; 559 } 560 561 static void __sysrq_put_key_op(int key, const struct sysrq_key_op *op_p) 562 { 563 int i = sysrq_key_table_key2index(key); 564 565 if (i != -1) 566 sysrq_key_table[i] = op_p; 567 } 568 569 void __handle_sysrq(int key, bool check_mask) 570 { 571 const struct sysrq_key_op *op_p; 572 int orig_log_level; 573 int orig_suppress_printk; 574 int i; 575 576 orig_suppress_printk = suppress_printk; 577 suppress_printk = 0; 578 579 rcu_sysrq_start(); 580 rcu_read_lock(); 581 printk_prefer_direct_enter(); 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 printk_prefer_direct_exit(); 624 rcu_read_unlock(); 625 rcu_sysrq_end(); 626 627 suppress_printk = orig_suppress_printk; 628 } 629 630 void handle_sysrq(int key) 631 { 632 if (sysrq_on()) 633 __handle_sysrq(key, true); 634 } 635 EXPORT_SYMBOL(handle_sysrq); 636 637 #ifdef CONFIG_INPUT 638 static int sysrq_reset_downtime_ms; 639 640 /* Simple translation table for the SysRq keys */ 641 static const unsigned char sysrq_xlate[KEY_CNT] = 642 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 643 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 644 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 645 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 646 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 647 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 648 "\r\000/"; /* 0x60 - 0x6f */ 649 650 struct sysrq_state { 651 struct input_handle handle; 652 struct work_struct reinject_work; 653 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 654 unsigned int alt; 655 unsigned int alt_use; 656 unsigned int shift; 657 unsigned int shift_use; 658 bool active; 659 bool need_reinject; 660 bool reinjecting; 661 662 /* reset sequence handling */ 663 bool reset_canceled; 664 bool reset_requested; 665 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 666 int reset_seq_len; 667 int reset_seq_cnt; 668 int reset_seq_version; 669 struct timer_list keyreset_timer; 670 }; 671 672 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 673 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 674 static unsigned int sysrq_reset_seq_len; 675 static unsigned int sysrq_reset_seq_version = 1; 676 677 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 678 { 679 int i; 680 unsigned short key; 681 682 state->reset_seq_cnt = 0; 683 684 for (i = 0; i < sysrq_reset_seq_len; i++) { 685 key = sysrq_reset_seq[i]; 686 687 if (key == KEY_RESERVED || key > KEY_MAX) 688 break; 689 690 __set_bit(key, state->reset_keybit); 691 state->reset_seq_len++; 692 693 if (test_bit(key, state->key_down)) 694 state->reset_seq_cnt++; 695 } 696 697 /* Disable reset until old keys are not released */ 698 state->reset_canceled = state->reset_seq_cnt != 0; 699 700 state->reset_seq_version = sysrq_reset_seq_version; 701 } 702 703 static void sysrq_do_reset(struct timer_list *t) 704 { 705 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 706 707 state->reset_requested = true; 708 709 orderly_reboot(); 710 } 711 712 static void sysrq_handle_reset_request(struct sysrq_state *state) 713 { 714 if (state->reset_requested) 715 __handle_sysrq(sysrq_xlate[KEY_B], false); 716 717 if (sysrq_reset_downtime_ms) 718 mod_timer(&state->keyreset_timer, 719 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 720 else 721 sysrq_do_reset(&state->keyreset_timer); 722 } 723 724 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 725 unsigned int code, int value) 726 { 727 if (!test_bit(code, state->reset_keybit)) { 728 /* 729 * Pressing any key _not_ in reset sequence cancels 730 * the reset sequence. Also cancelling the timer in 731 * case additional keys were pressed after a reset 732 * has been requested. 733 */ 734 if (value && state->reset_seq_cnt) { 735 state->reset_canceled = true; 736 del_timer(&state->keyreset_timer); 737 } 738 } else if (value == 0) { 739 /* 740 * Key release - all keys in the reset sequence need 741 * to be pressed and held for the reset timeout 742 * to hold. 743 */ 744 del_timer(&state->keyreset_timer); 745 746 if (--state->reset_seq_cnt == 0) 747 state->reset_canceled = false; 748 } else if (value == 1) { 749 /* key press, not autorepeat */ 750 if (++state->reset_seq_cnt == state->reset_seq_len && 751 !state->reset_canceled) { 752 sysrq_handle_reset_request(state); 753 } 754 } 755 } 756 757 #ifdef CONFIG_OF 758 static void sysrq_of_get_keyreset_config(void) 759 { 760 u32 key; 761 struct device_node *np; 762 struct property *prop; 763 const __be32 *p; 764 765 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 766 if (!np) { 767 pr_debug("No sysrq node found"); 768 return; 769 } 770 771 /* Reset in case a __weak definition was present */ 772 sysrq_reset_seq_len = 0; 773 774 of_property_for_each_u32(np, "keyset", prop, p, key) { 775 if (key == KEY_RESERVED || key > KEY_MAX || 776 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 777 break; 778 779 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 780 } 781 782 /* Get reset timeout if any. */ 783 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 784 785 of_node_put(np); 786 } 787 #else 788 static void sysrq_of_get_keyreset_config(void) 789 { 790 } 791 #endif 792 793 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 794 { 795 struct sysrq_state *sysrq = 796 container_of(work, struct sysrq_state, reinject_work); 797 struct input_handle *handle = &sysrq->handle; 798 unsigned int alt_code = sysrq->alt_use; 799 800 if (sysrq->need_reinject) { 801 /* we do not want the assignment to be reordered */ 802 sysrq->reinjecting = true; 803 mb(); 804 805 /* Simulate press and release of Alt + SysRq */ 806 input_inject_event(handle, EV_KEY, alt_code, 1); 807 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 808 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 809 810 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 811 input_inject_event(handle, EV_KEY, alt_code, 0); 812 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 813 814 mb(); 815 sysrq->reinjecting = false; 816 } 817 } 818 819 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 820 unsigned int code, int value) 821 { 822 bool was_active = sysrq->active; 823 bool suppress; 824 825 switch (code) { 826 827 case KEY_LEFTALT: 828 case KEY_RIGHTALT: 829 if (!value) { 830 /* One of ALTs is being released */ 831 if (sysrq->active && code == sysrq->alt_use) 832 sysrq->active = false; 833 834 sysrq->alt = KEY_RESERVED; 835 836 } else if (value != 2) { 837 sysrq->alt = code; 838 sysrq->need_reinject = false; 839 } 840 break; 841 842 case KEY_LEFTSHIFT: 843 case KEY_RIGHTSHIFT: 844 if (!value) 845 sysrq->shift = KEY_RESERVED; 846 else if (value != 2) 847 sysrq->shift = code; 848 if (sysrq->active) 849 sysrq->shift_use = sysrq->shift; 850 break; 851 852 case KEY_SYSRQ: 853 if (value == 1 && sysrq->alt != KEY_RESERVED) { 854 sysrq->active = true; 855 sysrq->alt_use = sysrq->alt; 856 /* either RESERVED (for released) or actual code */ 857 sysrq->shift_use = sysrq->shift; 858 /* 859 * If nothing else will be pressed we'll need 860 * to re-inject Alt-SysRq keysroke. 861 */ 862 sysrq->need_reinject = true; 863 } 864 865 /* 866 * Pretend that sysrq was never pressed at all. This 867 * is needed to properly handle KGDB which will try 868 * to release all keys after exiting debugger. If we 869 * do not clear key bit it KGDB will end up sending 870 * release events for Alt and SysRq, potentially 871 * triggering print screen function. 872 */ 873 if (sysrq->active) 874 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 875 876 break; 877 878 default: 879 if (sysrq->active && value && value != 2) { 880 unsigned char c = sysrq_xlate[code]; 881 882 sysrq->need_reinject = false; 883 if (sysrq->shift_use != KEY_RESERVED) 884 c = toupper(c); 885 __handle_sysrq(c, true); 886 } 887 break; 888 } 889 890 suppress = sysrq->active; 891 892 if (!sysrq->active) { 893 894 /* 895 * See if reset sequence has changed since the last time. 896 */ 897 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 898 sysrq_parse_reset_sequence(sysrq); 899 900 /* 901 * If we are not suppressing key presses keep track of 902 * keyboard state so we can release keys that have been 903 * pressed before entering SysRq mode. 904 */ 905 if (value) 906 set_bit(code, sysrq->key_down); 907 else 908 clear_bit(code, sysrq->key_down); 909 910 if (was_active) 911 schedule_work(&sysrq->reinject_work); 912 913 /* Check for reset sequence */ 914 sysrq_detect_reset_sequence(sysrq, code, value); 915 916 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 917 /* 918 * Pass on release events for keys that was pressed before 919 * entering SysRq mode. 920 */ 921 suppress = false; 922 } 923 924 return suppress; 925 } 926 927 static bool sysrq_filter(struct input_handle *handle, 928 unsigned int type, unsigned int code, int value) 929 { 930 struct sysrq_state *sysrq = handle->private; 931 bool suppress; 932 933 /* 934 * Do not filter anything if we are in the process of re-injecting 935 * Alt+SysRq combination. 936 */ 937 if (sysrq->reinjecting) 938 return false; 939 940 switch (type) { 941 942 case EV_SYN: 943 suppress = false; 944 break; 945 946 case EV_KEY: 947 suppress = sysrq_handle_keypress(sysrq, code, value); 948 break; 949 950 default: 951 suppress = sysrq->active; 952 break; 953 } 954 955 return suppress; 956 } 957 958 static int sysrq_connect(struct input_handler *handler, 959 struct input_dev *dev, 960 const struct input_device_id *id) 961 { 962 struct sysrq_state *sysrq; 963 int error; 964 965 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 966 if (!sysrq) 967 return -ENOMEM; 968 969 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 970 971 sysrq->handle.dev = dev; 972 sysrq->handle.handler = handler; 973 sysrq->handle.name = "sysrq"; 974 sysrq->handle.private = sysrq; 975 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 976 977 error = input_register_handle(&sysrq->handle); 978 if (error) { 979 pr_err("Failed to register input sysrq handler, error %d\n", 980 error); 981 goto err_free; 982 } 983 984 error = input_open_device(&sysrq->handle); 985 if (error) { 986 pr_err("Failed to open input device, error %d\n", error); 987 goto err_unregister; 988 } 989 990 return 0; 991 992 err_unregister: 993 input_unregister_handle(&sysrq->handle); 994 err_free: 995 kfree(sysrq); 996 return error; 997 } 998 999 static void sysrq_disconnect(struct input_handle *handle) 1000 { 1001 struct sysrq_state *sysrq = handle->private; 1002 1003 input_close_device(handle); 1004 cancel_work_sync(&sysrq->reinject_work); 1005 del_timer_sync(&sysrq->keyreset_timer); 1006 input_unregister_handle(handle); 1007 kfree(sysrq); 1008 } 1009 1010 /* 1011 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 1012 * keyboards have SysRq key predefined and so user may add it to keymap 1013 * later, but we expect all such keyboards to have left alt. 1014 */ 1015 static const struct input_device_id sysrq_ids[] = { 1016 { 1017 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 1018 INPUT_DEVICE_ID_MATCH_KEYBIT, 1019 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 1020 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 1021 }, 1022 { }, 1023 }; 1024 1025 static struct input_handler sysrq_handler = { 1026 .filter = sysrq_filter, 1027 .connect = sysrq_connect, 1028 .disconnect = sysrq_disconnect, 1029 .name = "sysrq", 1030 .id_table = sysrq_ids, 1031 }; 1032 1033 static inline void sysrq_register_handler(void) 1034 { 1035 int error; 1036 1037 sysrq_of_get_keyreset_config(); 1038 1039 error = input_register_handler(&sysrq_handler); 1040 if (error) 1041 pr_err("Failed to register input handler, error %d", error); 1042 } 1043 1044 static inline void sysrq_unregister_handler(void) 1045 { 1046 input_unregister_handler(&sysrq_handler); 1047 } 1048 1049 static int sysrq_reset_seq_param_set(const char *buffer, 1050 const struct kernel_param *kp) 1051 { 1052 unsigned long val; 1053 int error; 1054 1055 error = kstrtoul(buffer, 0, &val); 1056 if (error < 0) 1057 return error; 1058 1059 if (val > KEY_MAX) 1060 return -EINVAL; 1061 1062 *((unsigned short *)kp->arg) = val; 1063 sysrq_reset_seq_version++; 1064 1065 return 0; 1066 } 1067 1068 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1069 .get = param_get_ushort, 1070 .set = sysrq_reset_seq_param_set, 1071 }; 1072 1073 #define param_check_sysrq_reset_seq(name, p) \ 1074 __param_check(name, p, unsigned short) 1075 1076 /* 1077 * not really modular, but the easiest way to keep compat with existing 1078 * bootargs behaviour is to continue using module_param here. 1079 */ 1080 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1081 &sysrq_reset_seq_len, 0644); 1082 1083 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1084 1085 #else 1086 1087 static inline void sysrq_register_handler(void) 1088 { 1089 } 1090 1091 static inline void sysrq_unregister_handler(void) 1092 { 1093 } 1094 1095 #endif /* CONFIG_INPUT */ 1096 1097 int sysrq_toggle_support(int enable_mask) 1098 { 1099 bool was_enabled = sysrq_on(); 1100 1101 sysrq_enabled = enable_mask; 1102 1103 if (was_enabled != sysrq_on()) { 1104 if (sysrq_on()) 1105 sysrq_register_handler(); 1106 else 1107 sysrq_unregister_handler(); 1108 } 1109 1110 return 0; 1111 } 1112 EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1113 1114 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p, 1115 const struct sysrq_key_op *remove_op_p) 1116 { 1117 int retval; 1118 1119 spin_lock(&sysrq_key_table_lock); 1120 if (__sysrq_get_key_op(key) == remove_op_p) { 1121 __sysrq_put_key_op(key, insert_op_p); 1122 retval = 0; 1123 } else { 1124 retval = -1; 1125 } 1126 spin_unlock(&sysrq_key_table_lock); 1127 1128 /* 1129 * A concurrent __handle_sysrq either got the old op or the new op. 1130 * Wait for it to go away before returning, so the code for an old 1131 * op is not freed (eg. on module unload) while it is in use. 1132 */ 1133 synchronize_rcu(); 1134 1135 return retval; 1136 } 1137 1138 int register_sysrq_key(int key, const struct sysrq_key_op *op_p) 1139 { 1140 return __sysrq_swap_key_ops(key, op_p, NULL); 1141 } 1142 EXPORT_SYMBOL(register_sysrq_key); 1143 1144 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p) 1145 { 1146 return __sysrq_swap_key_ops(key, NULL, op_p); 1147 } 1148 EXPORT_SYMBOL(unregister_sysrq_key); 1149 1150 #ifdef CONFIG_PROC_FS 1151 /* 1152 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1153 */ 1154 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1155 size_t count, loff_t *ppos) 1156 { 1157 if (count) { 1158 char c; 1159 1160 if (get_user(c, buf)) 1161 return -EFAULT; 1162 __handle_sysrq(c, false); 1163 } 1164 1165 return count; 1166 } 1167 1168 static const struct proc_ops sysrq_trigger_proc_ops = { 1169 .proc_write = write_sysrq_trigger, 1170 .proc_lseek = noop_llseek, 1171 }; 1172 1173 static void sysrq_init_procfs(void) 1174 { 1175 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1176 &sysrq_trigger_proc_ops)) 1177 pr_err("Failed to register proc interface\n"); 1178 } 1179 1180 #else 1181 1182 static inline void sysrq_init_procfs(void) 1183 { 1184 } 1185 1186 #endif /* CONFIG_PROC_FS */ 1187 1188 static int __init sysrq_init(void) 1189 { 1190 sysrq_init_procfs(); 1191 1192 if (sysrq_on()) 1193 sysrq_register_handler(); 1194 1195 return 0; 1196 } 1197 device_initcall(sysrq_init); 1198