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 /* 582 * Raise the apparent loglevel to maximum so that the sysrq header 583 * is shown to provide the user with positive feedback. We do not 584 * simply emit this at KERN_EMERG as that would change message 585 * routing in the consumers of /proc/kmsg. 586 */ 587 orig_log_level = console_loglevel; 588 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 589 590 op_p = __sysrq_get_key_op(key); 591 if (op_p) { 592 /* 593 * Should we check for enabled operations (/proc/sysrq-trigger 594 * should not) and is the invoked operation enabled? 595 */ 596 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 597 pr_info("%s\n", op_p->action_msg); 598 console_loglevel = orig_log_level; 599 op_p->handler(key); 600 } else { 601 pr_info("This sysrq operation is disabled.\n"); 602 console_loglevel = orig_log_level; 603 } 604 } else { 605 pr_info("HELP : "); 606 /* Only print the help msg once per handler */ 607 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 608 if (sysrq_key_table[i]) { 609 int j; 610 611 for (j = 0; sysrq_key_table[i] != 612 sysrq_key_table[j]; j++) 613 ; 614 if (j != i) 615 continue; 616 pr_cont("%s ", sysrq_key_table[i]->help_msg); 617 } 618 } 619 pr_cont("\n"); 620 console_loglevel = orig_log_level; 621 } 622 rcu_read_unlock(); 623 rcu_sysrq_end(); 624 625 suppress_printk = orig_suppress_printk; 626 } 627 628 void handle_sysrq(int key) 629 { 630 if (sysrq_on()) 631 __handle_sysrq(key, true); 632 } 633 EXPORT_SYMBOL(handle_sysrq); 634 635 #ifdef CONFIG_INPUT 636 static int sysrq_reset_downtime_ms; 637 638 /* Simple translation table for the SysRq keys */ 639 static const unsigned char sysrq_xlate[KEY_CNT] = 640 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 641 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 642 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 643 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 644 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 645 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 646 "\r\000/"; /* 0x60 - 0x6f */ 647 648 struct sysrq_state { 649 struct input_handle handle; 650 struct work_struct reinject_work; 651 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 652 unsigned int alt; 653 unsigned int alt_use; 654 unsigned int shift; 655 unsigned int shift_use; 656 bool active; 657 bool need_reinject; 658 bool reinjecting; 659 660 /* reset sequence handling */ 661 bool reset_canceled; 662 bool reset_requested; 663 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 664 int reset_seq_len; 665 int reset_seq_cnt; 666 int reset_seq_version; 667 struct timer_list keyreset_timer; 668 }; 669 670 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 671 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 672 static unsigned int sysrq_reset_seq_len; 673 static unsigned int sysrq_reset_seq_version = 1; 674 675 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 676 { 677 int i; 678 unsigned short key; 679 680 state->reset_seq_cnt = 0; 681 682 for (i = 0; i < sysrq_reset_seq_len; i++) { 683 key = sysrq_reset_seq[i]; 684 685 if (key == KEY_RESERVED || key > KEY_MAX) 686 break; 687 688 __set_bit(key, state->reset_keybit); 689 state->reset_seq_len++; 690 691 if (test_bit(key, state->key_down)) 692 state->reset_seq_cnt++; 693 } 694 695 /* Disable reset until old keys are not released */ 696 state->reset_canceled = state->reset_seq_cnt != 0; 697 698 state->reset_seq_version = sysrq_reset_seq_version; 699 } 700 701 static void sysrq_do_reset(struct timer_list *t) 702 { 703 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 704 705 state->reset_requested = true; 706 707 orderly_reboot(); 708 } 709 710 static void sysrq_handle_reset_request(struct sysrq_state *state) 711 { 712 if (state->reset_requested) 713 __handle_sysrq(sysrq_xlate[KEY_B], false); 714 715 if (sysrq_reset_downtime_ms) 716 mod_timer(&state->keyreset_timer, 717 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 718 else 719 sysrq_do_reset(&state->keyreset_timer); 720 } 721 722 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 723 unsigned int code, int value) 724 { 725 if (!test_bit(code, state->reset_keybit)) { 726 /* 727 * Pressing any key _not_ in reset sequence cancels 728 * the reset sequence. Also cancelling the timer in 729 * case additional keys were pressed after a reset 730 * has been requested. 731 */ 732 if (value && state->reset_seq_cnt) { 733 state->reset_canceled = true; 734 del_timer(&state->keyreset_timer); 735 } 736 } else if (value == 0) { 737 /* 738 * Key release - all keys in the reset sequence need 739 * to be pressed and held for the reset timeout 740 * to hold. 741 */ 742 del_timer(&state->keyreset_timer); 743 744 if (--state->reset_seq_cnt == 0) 745 state->reset_canceled = false; 746 } else if (value == 1) { 747 /* key press, not autorepeat */ 748 if (++state->reset_seq_cnt == state->reset_seq_len && 749 !state->reset_canceled) { 750 sysrq_handle_reset_request(state); 751 } 752 } 753 } 754 755 #ifdef CONFIG_OF 756 static void sysrq_of_get_keyreset_config(void) 757 { 758 u32 key; 759 struct device_node *np; 760 struct property *prop; 761 const __be32 *p; 762 763 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 764 if (!np) { 765 pr_debug("No sysrq node found"); 766 return; 767 } 768 769 /* Reset in case a __weak definition was present */ 770 sysrq_reset_seq_len = 0; 771 772 of_property_for_each_u32(np, "keyset", prop, p, key) { 773 if (key == KEY_RESERVED || key > KEY_MAX || 774 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 775 break; 776 777 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 778 } 779 780 /* Get reset timeout if any. */ 781 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 782 783 of_node_put(np); 784 } 785 #else 786 static void sysrq_of_get_keyreset_config(void) 787 { 788 } 789 #endif 790 791 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 792 { 793 struct sysrq_state *sysrq = 794 container_of(work, struct sysrq_state, reinject_work); 795 struct input_handle *handle = &sysrq->handle; 796 unsigned int alt_code = sysrq->alt_use; 797 798 if (sysrq->need_reinject) { 799 /* we do not want the assignment to be reordered */ 800 sysrq->reinjecting = true; 801 mb(); 802 803 /* Simulate press and release of Alt + SysRq */ 804 input_inject_event(handle, EV_KEY, alt_code, 1); 805 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 806 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 807 808 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 809 input_inject_event(handle, EV_KEY, alt_code, 0); 810 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 811 812 mb(); 813 sysrq->reinjecting = false; 814 } 815 } 816 817 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 818 unsigned int code, int value) 819 { 820 bool was_active = sysrq->active; 821 bool suppress; 822 823 switch (code) { 824 825 case KEY_LEFTALT: 826 case KEY_RIGHTALT: 827 if (!value) { 828 /* One of ALTs is being released */ 829 if (sysrq->active && code == sysrq->alt_use) 830 sysrq->active = false; 831 832 sysrq->alt = KEY_RESERVED; 833 834 } else if (value != 2) { 835 sysrq->alt = code; 836 sysrq->need_reinject = false; 837 } 838 break; 839 840 case KEY_LEFTSHIFT: 841 case KEY_RIGHTSHIFT: 842 if (!value) 843 sysrq->shift = KEY_RESERVED; 844 else if (value != 2) 845 sysrq->shift = code; 846 if (sysrq->active) 847 sysrq->shift_use = sysrq->shift; 848 break; 849 850 case KEY_SYSRQ: 851 if (value == 1 && sysrq->alt != KEY_RESERVED) { 852 sysrq->active = true; 853 sysrq->alt_use = sysrq->alt; 854 /* either RESERVED (for released) or actual code */ 855 sysrq->shift_use = sysrq->shift; 856 /* 857 * If nothing else will be pressed we'll need 858 * to re-inject Alt-SysRq keysroke. 859 */ 860 sysrq->need_reinject = true; 861 } 862 863 /* 864 * Pretend that sysrq was never pressed at all. This 865 * is needed to properly handle KGDB which will try 866 * to release all keys after exiting debugger. If we 867 * do not clear key bit it KGDB will end up sending 868 * release events for Alt and SysRq, potentially 869 * triggering print screen function. 870 */ 871 if (sysrq->active) 872 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 873 874 break; 875 876 default: 877 if (sysrq->active && value && value != 2) { 878 unsigned char c = sysrq_xlate[code]; 879 880 sysrq->need_reinject = false; 881 if (sysrq->shift_use != KEY_RESERVED) 882 c = toupper(c); 883 __handle_sysrq(c, true); 884 } 885 break; 886 } 887 888 suppress = sysrq->active; 889 890 if (!sysrq->active) { 891 892 /* 893 * See if reset sequence has changed since the last time. 894 */ 895 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 896 sysrq_parse_reset_sequence(sysrq); 897 898 /* 899 * If we are not suppressing key presses keep track of 900 * keyboard state so we can release keys that have been 901 * pressed before entering SysRq mode. 902 */ 903 if (value) 904 set_bit(code, sysrq->key_down); 905 else 906 clear_bit(code, sysrq->key_down); 907 908 if (was_active) 909 schedule_work(&sysrq->reinject_work); 910 911 /* Check for reset sequence */ 912 sysrq_detect_reset_sequence(sysrq, code, value); 913 914 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 915 /* 916 * Pass on release events for keys that was pressed before 917 * entering SysRq mode. 918 */ 919 suppress = false; 920 } 921 922 return suppress; 923 } 924 925 static bool sysrq_filter(struct input_handle *handle, 926 unsigned int type, unsigned int code, int value) 927 { 928 struct sysrq_state *sysrq = handle->private; 929 bool suppress; 930 931 /* 932 * Do not filter anything if we are in the process of re-injecting 933 * Alt+SysRq combination. 934 */ 935 if (sysrq->reinjecting) 936 return false; 937 938 switch (type) { 939 940 case EV_SYN: 941 suppress = false; 942 break; 943 944 case EV_KEY: 945 suppress = sysrq_handle_keypress(sysrq, code, value); 946 break; 947 948 default: 949 suppress = sysrq->active; 950 break; 951 } 952 953 return suppress; 954 } 955 956 static int sysrq_connect(struct input_handler *handler, 957 struct input_dev *dev, 958 const struct input_device_id *id) 959 { 960 struct sysrq_state *sysrq; 961 int error; 962 963 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 964 if (!sysrq) 965 return -ENOMEM; 966 967 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 968 969 sysrq->handle.dev = dev; 970 sysrq->handle.handler = handler; 971 sysrq->handle.name = "sysrq"; 972 sysrq->handle.private = sysrq; 973 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 974 975 error = input_register_handle(&sysrq->handle); 976 if (error) { 977 pr_err("Failed to register input sysrq handler, error %d\n", 978 error); 979 goto err_free; 980 } 981 982 error = input_open_device(&sysrq->handle); 983 if (error) { 984 pr_err("Failed to open input device, error %d\n", error); 985 goto err_unregister; 986 } 987 988 return 0; 989 990 err_unregister: 991 input_unregister_handle(&sysrq->handle); 992 err_free: 993 kfree(sysrq); 994 return error; 995 } 996 997 static void sysrq_disconnect(struct input_handle *handle) 998 { 999 struct sysrq_state *sysrq = handle->private; 1000 1001 input_close_device(handle); 1002 cancel_work_sync(&sysrq->reinject_work); 1003 del_timer_sync(&sysrq->keyreset_timer); 1004 input_unregister_handle(handle); 1005 kfree(sysrq); 1006 } 1007 1008 /* 1009 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 1010 * keyboards have SysRq key predefined and so user may add it to keymap 1011 * later, but we expect all such keyboards to have left alt. 1012 */ 1013 static const struct input_device_id sysrq_ids[] = { 1014 { 1015 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 1016 INPUT_DEVICE_ID_MATCH_KEYBIT, 1017 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 1018 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 1019 }, 1020 { }, 1021 }; 1022 1023 static struct input_handler sysrq_handler = { 1024 .filter = sysrq_filter, 1025 .connect = sysrq_connect, 1026 .disconnect = sysrq_disconnect, 1027 .name = "sysrq", 1028 .id_table = sysrq_ids, 1029 }; 1030 1031 static inline void sysrq_register_handler(void) 1032 { 1033 int error; 1034 1035 sysrq_of_get_keyreset_config(); 1036 1037 error = input_register_handler(&sysrq_handler); 1038 if (error) 1039 pr_err("Failed to register input handler, error %d", error); 1040 } 1041 1042 static inline void sysrq_unregister_handler(void) 1043 { 1044 input_unregister_handler(&sysrq_handler); 1045 } 1046 1047 static int sysrq_reset_seq_param_set(const char *buffer, 1048 const struct kernel_param *kp) 1049 { 1050 unsigned long val; 1051 int error; 1052 1053 error = kstrtoul(buffer, 0, &val); 1054 if (error < 0) 1055 return error; 1056 1057 if (val > KEY_MAX) 1058 return -EINVAL; 1059 1060 *((unsigned short *)kp->arg) = val; 1061 sysrq_reset_seq_version++; 1062 1063 return 0; 1064 } 1065 1066 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1067 .get = param_get_ushort, 1068 .set = sysrq_reset_seq_param_set, 1069 }; 1070 1071 #define param_check_sysrq_reset_seq(name, p) \ 1072 __param_check(name, p, unsigned short) 1073 1074 /* 1075 * not really modular, but the easiest way to keep compat with existing 1076 * bootargs behaviour is to continue using module_param here. 1077 */ 1078 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1079 &sysrq_reset_seq_len, 0644); 1080 1081 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1082 1083 #else 1084 1085 static inline void sysrq_register_handler(void) 1086 { 1087 } 1088 1089 static inline void sysrq_unregister_handler(void) 1090 { 1091 } 1092 1093 #endif /* CONFIG_INPUT */ 1094 1095 int sysrq_toggle_support(int enable_mask) 1096 { 1097 bool was_enabled = sysrq_on(); 1098 1099 sysrq_enabled = enable_mask; 1100 1101 if (was_enabled != sysrq_on()) { 1102 if (sysrq_on()) 1103 sysrq_register_handler(); 1104 else 1105 sysrq_unregister_handler(); 1106 } 1107 1108 return 0; 1109 } 1110 EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1111 1112 static int __sysrq_swap_key_ops(int key, const struct sysrq_key_op *insert_op_p, 1113 const struct sysrq_key_op *remove_op_p) 1114 { 1115 int retval; 1116 1117 spin_lock(&sysrq_key_table_lock); 1118 if (__sysrq_get_key_op(key) == remove_op_p) { 1119 __sysrq_put_key_op(key, insert_op_p); 1120 retval = 0; 1121 } else { 1122 retval = -1; 1123 } 1124 spin_unlock(&sysrq_key_table_lock); 1125 1126 /* 1127 * A concurrent __handle_sysrq either got the old op or the new op. 1128 * Wait for it to go away before returning, so the code for an old 1129 * op is not freed (eg. on module unload) while it is in use. 1130 */ 1131 synchronize_rcu(); 1132 1133 return retval; 1134 } 1135 1136 int register_sysrq_key(int key, const struct sysrq_key_op *op_p) 1137 { 1138 return __sysrq_swap_key_ops(key, op_p, NULL); 1139 } 1140 EXPORT_SYMBOL(register_sysrq_key); 1141 1142 int unregister_sysrq_key(int key, const struct sysrq_key_op *op_p) 1143 { 1144 return __sysrq_swap_key_ops(key, NULL, op_p); 1145 } 1146 EXPORT_SYMBOL(unregister_sysrq_key); 1147 1148 #ifdef CONFIG_PROC_FS 1149 /* 1150 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1151 */ 1152 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1153 size_t count, loff_t *ppos) 1154 { 1155 if (count) { 1156 char c; 1157 1158 if (get_user(c, buf)) 1159 return -EFAULT; 1160 __handle_sysrq(c, false); 1161 } 1162 1163 return count; 1164 } 1165 1166 static const struct proc_ops sysrq_trigger_proc_ops = { 1167 .proc_write = write_sysrq_trigger, 1168 .proc_lseek = noop_llseek, 1169 }; 1170 1171 static void sysrq_init_procfs(void) 1172 { 1173 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1174 &sysrq_trigger_proc_ops)) 1175 pr_err("Failed to register proc interface\n"); 1176 } 1177 1178 #else 1179 1180 static inline void sysrq_init_procfs(void) 1181 { 1182 } 1183 1184 #endif /* CONFIG_PROC_FS */ 1185 1186 static int __init sysrq_init(void) 1187 { 1188 sysrq_init_procfs(); 1189 1190 if (sysrq_on()) 1191 sysrq_register_handler(); 1192 1193 return 0; 1194 } 1195 device_initcall(sysrq_init); 1196