1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Linux Magic System Request Key Hacks 4 * 5 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz> 6 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz> 7 * 8 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com> 9 * overhauled to use key registration 10 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies 11 * 12 * Copyright (c) 2010 Dmitry Torokhov 13 * Input handler conversion 14 */ 15 16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 17 18 #include <linux/sched/signal.h> 19 #include <linux/sched/rt.h> 20 #include <linux/sched/debug.h> 21 #include <linux/sched/task.h> 22 #include <linux/ctype.h> 23 #include <linux/interrupt.h> 24 #include <linux/mm.h> 25 #include <linux/fs.h> 26 #include <linux/mount.h> 27 #include <linux/kdev_t.h> 28 #include <linux/major.h> 29 #include <linux/reboot.h> 30 #include <linux/sysrq.h> 31 #include <linux/kbd_kern.h> 32 #include <linux/proc_fs.h> 33 #include <linux/nmi.h> 34 #include <linux/quotaops.h> 35 #include <linux/perf_event.h> 36 #include <linux/kernel.h> 37 #include <linux/module.h> 38 #include <linux/suspend.h> 39 #include <linux/writeback.h> 40 #include <linux/swap.h> 41 #include <linux/spinlock.h> 42 #include <linux/vt_kern.h> 43 #include <linux/workqueue.h> 44 #include <linux/hrtimer.h> 45 #include <linux/oom.h> 46 #include <linux/slab.h> 47 #include <linux/input.h> 48 #include <linux/uaccess.h> 49 #include <linux/moduleparam.h> 50 #include <linux/jiffies.h> 51 #include <linux/syscalls.h> 52 #include <linux/of.h> 53 #include <linux/rcupdate.h> 54 55 #include <asm/ptrace.h> 56 #include <asm/irq_regs.h> 57 58 /* Whether we react on sysrq keys or just ignore them */ 59 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; 60 static bool __read_mostly sysrq_always_enabled; 61 62 static bool sysrq_on(void) 63 { 64 return sysrq_enabled || sysrq_always_enabled; 65 } 66 67 /** 68 * sysrq_mask - Getter for sysrq_enabled mask. 69 * 70 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise. 71 */ 72 int sysrq_mask(void) 73 { 74 if (sysrq_always_enabled) 75 return 1; 76 return sysrq_enabled; 77 } 78 EXPORT_SYMBOL_GPL(sysrq_mask); 79 80 /* 81 * A value of 1 means 'all', other nonzero values are an op mask: 82 */ 83 static bool sysrq_on_mask(int mask) 84 { 85 return sysrq_always_enabled || 86 sysrq_enabled == 1 || 87 (sysrq_enabled & mask); 88 } 89 90 static int __init sysrq_always_enabled_setup(char *str) 91 { 92 sysrq_always_enabled = true; 93 pr_info("sysrq always enabled.\n"); 94 95 return 1; 96 } 97 98 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 99 100 101 static void sysrq_handle_loglevel(u8 key) 102 { 103 u8 loglevel = key - '0'; 104 105 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 106 pr_info("Loglevel set to %u\n", loglevel); 107 console_loglevel = loglevel; 108 } 109 static const struct sysrq_key_op sysrq_loglevel_op = { 110 .handler = sysrq_handle_loglevel, 111 .help_msg = "loglevel(0-9)", 112 .action_msg = "Changing Loglevel", 113 .enable_mask = SYSRQ_ENABLE_LOG, 114 }; 115 116 #ifdef CONFIG_VT 117 static void sysrq_handle_SAK(u8 key) 118 { 119 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 120 121 schedule_work(SAK_work); 122 } 123 static const struct sysrq_key_op sysrq_SAK_op = { 124 .handler = sysrq_handle_SAK, 125 .help_msg = "sak(k)", 126 .action_msg = "SAK", 127 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 128 }; 129 #else 130 #define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL) 131 #endif 132 133 #ifdef CONFIG_VT 134 static void sysrq_handle_unraw(u8 key) 135 { 136 vt_reset_unicode(fg_console); 137 } 138 139 static const struct sysrq_key_op sysrq_unraw_op = { 140 .handler = sysrq_handle_unraw, 141 .help_msg = "unraw(r)", 142 .action_msg = "Keyboard mode set to system default", 143 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 144 }; 145 #else 146 #define sysrq_unraw_op (*(const struct sysrq_key_op *)NULL) 147 #endif /* CONFIG_VT */ 148 149 static void sysrq_handle_crash(u8 key) 150 { 151 /* release the RCU read lock before crashing */ 152 rcu_read_unlock(); 153 154 panic("sysrq triggered crash\n"); 155 } 156 static const struct sysrq_key_op sysrq_crash_op = { 157 .handler = sysrq_handle_crash, 158 .help_msg = "crash(c)", 159 .action_msg = "Trigger a crash", 160 .enable_mask = SYSRQ_ENABLE_DUMP, 161 }; 162 163 static void sysrq_handle_reboot(u8 key) 164 { 165 lockdep_off(); 166 local_irq_enable(); 167 emergency_restart(); 168 } 169 static const struct sysrq_key_op sysrq_reboot_op = { 170 .handler = sysrq_handle_reboot, 171 .help_msg = "reboot(b)", 172 .action_msg = "Resetting", 173 .enable_mask = SYSRQ_ENABLE_BOOT, 174 }; 175 176 const struct sysrq_key_op *__sysrq_reboot_op = &sysrq_reboot_op; 177 178 static void sysrq_handle_sync(u8 key) 179 { 180 emergency_sync(); 181 } 182 static const struct sysrq_key_op sysrq_sync_op = { 183 .handler = sysrq_handle_sync, 184 .help_msg = "sync(s)", 185 .action_msg = "Emergency Sync", 186 .enable_mask = SYSRQ_ENABLE_SYNC, 187 }; 188 189 static void sysrq_handle_show_timers(u8 key) 190 { 191 sysrq_timer_list_show(); 192 } 193 194 static const struct sysrq_key_op sysrq_show_timers_op = { 195 .handler = sysrq_handle_show_timers, 196 .help_msg = "show-all-timers(q)", 197 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 198 }; 199 200 static void sysrq_handle_mountro(u8 key) 201 { 202 emergency_remount(); 203 } 204 static const struct sysrq_key_op sysrq_mountro_op = { 205 .handler = sysrq_handle_mountro, 206 .help_msg = "unmount(u)", 207 .action_msg = "Emergency Remount R/O", 208 .enable_mask = SYSRQ_ENABLE_REMOUNT, 209 }; 210 211 #ifdef CONFIG_LOCKDEP 212 static void sysrq_handle_showlocks(u8 key) 213 { 214 debug_show_all_locks(); 215 } 216 217 static const struct sysrq_key_op sysrq_showlocks_op = { 218 .handler = sysrq_handle_showlocks, 219 .help_msg = "show-all-locks(d)", 220 .action_msg = "Show Locks Held", 221 }; 222 #else 223 #define sysrq_showlocks_op (*(const struct sysrq_key_op *)NULL) 224 #endif 225 226 #ifdef CONFIG_SMP 227 static DEFINE_RAW_SPINLOCK(show_lock); 228 229 static void showacpu(void *dummy) 230 { 231 unsigned long flags; 232 233 /* Idle CPUs have no interesting backtrace. */ 234 if (idle_cpu(smp_processor_id())) { 235 pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id()); 236 return; 237 } 238 239 raw_spin_lock_irqsave(&show_lock, flags); 240 pr_info("CPU%d:\n", smp_processor_id()); 241 show_stack(NULL, NULL, KERN_INFO); 242 raw_spin_unlock_irqrestore(&show_lock, flags); 243 } 244 245 static void sysrq_showregs_othercpus(struct work_struct *dummy) 246 { 247 smp_call_function(showacpu, NULL, 0); 248 } 249 250 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 251 252 static void sysrq_handle_showallcpus(u8 key) 253 { 254 /* 255 * Fall back to the workqueue based printing if the 256 * backtrace printing did not succeed or the 257 * architecture has no support for it: 258 */ 259 if (!trigger_all_cpu_backtrace()) { 260 struct pt_regs *regs = NULL; 261 262 if (in_hardirq()) 263 regs = get_irq_regs(); 264 265 pr_info("CPU%d:\n", get_cpu()); 266 if (regs) 267 show_regs(regs); 268 else 269 show_stack(NULL, NULL, KERN_INFO); 270 271 schedule_work(&sysrq_showallcpus); 272 put_cpu(); 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(u8 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(u8 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(u8 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(u8 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(u8 key) 344 { 345 show_mem(); 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(u8 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(u8 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(u8 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(u8 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(u8 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 static void sysrq_handle_replay_logs(u8 key) 454 { 455 console_replay_all(); 456 } 457 static struct sysrq_key_op sysrq_replay_logs_op = { 458 .handler = sysrq_handle_replay_logs, 459 .help_msg = "replay-kernel-logs(R)", 460 .action_msg = "Replay kernel logs on consoles", 461 .enable_mask = SYSRQ_ENABLE_DUMP, 462 }; 463 464 /* Key Operations table and lock */ 465 static DEFINE_SPINLOCK(sysrq_key_table_lock); 466 467 static const struct sysrq_key_op *sysrq_key_table[62] = { 468 &sysrq_loglevel_op, /* 0 */ 469 &sysrq_loglevel_op, /* 1 */ 470 &sysrq_loglevel_op, /* 2 */ 471 &sysrq_loglevel_op, /* 3 */ 472 &sysrq_loglevel_op, /* 4 */ 473 &sysrq_loglevel_op, /* 5 */ 474 &sysrq_loglevel_op, /* 6 */ 475 &sysrq_loglevel_op, /* 7 */ 476 &sysrq_loglevel_op, /* 8 */ 477 &sysrq_loglevel_op, /* 9 */ 478 479 /* 480 * a: Don't use for system provided sysrqs, it is handled specially on 481 * sparc and will never arrive. 482 */ 483 NULL, /* a */ 484 &sysrq_reboot_op, /* b */ 485 &sysrq_crash_op, /* c */ 486 &sysrq_showlocks_op, /* d */ 487 &sysrq_term_op, /* e */ 488 &sysrq_moom_op, /* f */ 489 /* g: May be registered for the kernel debugger */ 490 NULL, /* g */ 491 NULL, /* h - reserved for help */ 492 &sysrq_kill_op, /* i */ 493 &sysrq_thaw_op, /* j */ 494 &sysrq_SAK_op, /* k */ 495 &sysrq_showallcpus_op, /* l */ 496 &sysrq_showmem_op, /* m */ 497 &sysrq_unrt_op, /* n */ 498 /* o: This will often be registered as 'Off' at init time */ 499 NULL, /* o */ 500 &sysrq_showregs_op, /* p */ 501 &sysrq_show_timers_op, /* q */ 502 &sysrq_unraw_op, /* r */ 503 &sysrq_sync_op, /* s */ 504 &sysrq_showstate_op, /* t */ 505 &sysrq_mountro_op, /* u */ 506 /* v: May be registered for frame buffer console restore */ 507 NULL, /* v */ 508 &sysrq_showstate_blocked_op, /* w */ 509 /* x: May be registered on mips for TLB dump */ 510 /* x: May be registered on ppc/powerpc for xmon */ 511 /* x: May be registered on sparc64 for global PMU dump */ 512 NULL, /* x */ 513 /* y: May be registered on sparc64 for global register dump */ 514 NULL, /* y */ 515 &sysrq_ftrace_dump_op, /* z */ 516 NULL, /* A */ 517 NULL, /* B */ 518 NULL, /* C */ 519 NULL, /* D */ 520 NULL, /* E */ 521 NULL, /* F */ 522 NULL, /* G */ 523 NULL, /* H */ 524 NULL, /* I */ 525 NULL, /* J */ 526 NULL, /* K */ 527 NULL, /* L */ 528 NULL, /* M */ 529 NULL, /* N */ 530 NULL, /* O */ 531 NULL, /* P */ 532 NULL, /* Q */ 533 &sysrq_replay_logs_op, /* R */ 534 /* S: May be registered by sched_ext for resetting */ 535 NULL, /* S */ 536 NULL, /* T */ 537 NULL, /* U */ 538 NULL, /* V */ 539 NULL, /* W */ 540 NULL, /* X */ 541 NULL, /* Y */ 542 NULL, /* Z */ 543 }; 544 545 /* key2index calculation, -1 on invalid index */ 546 static int sysrq_key_table_key2index(u8 key) 547 { 548 switch (key) { 549 case '0' ... '9': 550 return key - '0'; 551 case 'a' ... 'z': 552 return key - 'a' + 10; 553 case 'A' ... 'Z': 554 return key - 'A' + 10 + 26; 555 default: 556 return -1; 557 } 558 } 559 560 /* 561 * get and put functions for the table, exposed to modules. 562 */ 563 static const struct sysrq_key_op *__sysrq_get_key_op(u8 key) 564 { 565 const struct sysrq_key_op *op_p = NULL; 566 int i; 567 568 i = sysrq_key_table_key2index(key); 569 if (i != -1) 570 op_p = sysrq_key_table[i]; 571 572 return op_p; 573 } 574 575 static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p) 576 { 577 int i = sysrq_key_table_key2index(key); 578 579 if (i != -1) 580 sysrq_key_table[i] = op_p; 581 } 582 583 void __handle_sysrq(u8 key, bool check_mask) 584 { 585 const struct sysrq_key_op *op_p; 586 int orig_log_level; 587 int orig_suppress_printk; 588 int i; 589 590 orig_suppress_printk = suppress_printk; 591 suppress_printk = 0; 592 593 rcu_sysrq_start(); 594 rcu_read_lock(); 595 /* 596 * Raise the apparent loglevel to maximum so that the sysrq header 597 * is shown to provide the user with positive feedback. We do not 598 * simply emit this at KERN_EMERG as that would change message 599 * routing in the consumers of /proc/kmsg. 600 */ 601 orig_log_level = console_loglevel; 602 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 603 604 op_p = __sysrq_get_key_op(key); 605 if (op_p) { 606 /* 607 * Should we check for enabled operations (/proc/sysrq-trigger 608 * should not) and is the invoked operation enabled? 609 */ 610 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 611 pr_info("%s\n", op_p->action_msg); 612 console_loglevel = orig_log_level; 613 op_p->handler(key); 614 } else { 615 pr_info("This sysrq operation is disabled.\n"); 616 console_loglevel = orig_log_level; 617 } 618 } else { 619 pr_info("HELP : "); 620 /* Only print the help msg once per handler */ 621 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 622 if (sysrq_key_table[i]) { 623 int j; 624 625 for (j = 0; sysrq_key_table[i] != 626 sysrq_key_table[j]; j++) 627 ; 628 if (j != i) 629 continue; 630 pr_cont("%s ", sysrq_key_table[i]->help_msg); 631 } 632 } 633 pr_cont("\n"); 634 console_loglevel = orig_log_level; 635 } 636 rcu_read_unlock(); 637 rcu_sysrq_end(); 638 639 suppress_printk = orig_suppress_printk; 640 } 641 642 void handle_sysrq(u8 key) 643 { 644 if (sysrq_on()) 645 __handle_sysrq(key, true); 646 } 647 EXPORT_SYMBOL(handle_sysrq); 648 649 #ifdef CONFIG_INPUT 650 static int sysrq_reset_downtime_ms; 651 652 /* Simple translation table for the SysRq keys */ 653 static const unsigned char sysrq_xlate[KEY_CNT] = 654 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 655 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 656 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 657 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 658 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 659 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 660 "\r\000/"; /* 0x60 - 0x6f */ 661 662 struct sysrq_state { 663 struct input_handle handle; 664 struct work_struct reinject_work; 665 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 666 unsigned int alt; 667 unsigned int alt_use; 668 unsigned int shift; 669 unsigned int shift_use; 670 bool active; 671 bool need_reinject; 672 bool reinjecting; 673 674 /* reset sequence handling */ 675 bool reset_canceled; 676 bool reset_requested; 677 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 678 int reset_seq_len; 679 int reset_seq_cnt; 680 int reset_seq_version; 681 struct timer_list keyreset_timer; 682 }; 683 684 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 685 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 686 static unsigned int sysrq_reset_seq_len; 687 static unsigned int sysrq_reset_seq_version = 1; 688 689 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 690 { 691 int i; 692 unsigned short key; 693 694 state->reset_seq_cnt = 0; 695 696 for (i = 0; i < sysrq_reset_seq_len; i++) { 697 key = sysrq_reset_seq[i]; 698 699 if (key == KEY_RESERVED || key > KEY_MAX) 700 break; 701 702 __set_bit(key, state->reset_keybit); 703 state->reset_seq_len++; 704 705 if (test_bit(key, state->key_down)) 706 state->reset_seq_cnt++; 707 } 708 709 /* Disable reset until old keys are not released */ 710 state->reset_canceled = state->reset_seq_cnt != 0; 711 712 state->reset_seq_version = sysrq_reset_seq_version; 713 } 714 715 static void sysrq_do_reset(struct timer_list *t) 716 { 717 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 718 719 state->reset_requested = true; 720 721 orderly_reboot(); 722 } 723 724 static void sysrq_handle_reset_request(struct sysrq_state *state) 725 { 726 if (state->reset_requested) 727 __handle_sysrq(sysrq_xlate[KEY_B], false); 728 729 if (sysrq_reset_downtime_ms) 730 mod_timer(&state->keyreset_timer, 731 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 732 else 733 sysrq_do_reset(&state->keyreset_timer); 734 } 735 736 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 737 unsigned int code, int value) 738 { 739 if (!test_bit(code, state->reset_keybit)) { 740 /* 741 * Pressing any key _not_ in reset sequence cancels 742 * the reset sequence. Also cancelling the timer in 743 * case additional keys were pressed after a reset 744 * has been requested. 745 */ 746 if (value && state->reset_seq_cnt) { 747 state->reset_canceled = true; 748 del_timer(&state->keyreset_timer); 749 } 750 } else if (value == 0) { 751 /* 752 * Key release - all keys in the reset sequence need 753 * to be pressed and held for the reset timeout 754 * to hold. 755 */ 756 del_timer(&state->keyreset_timer); 757 758 if (--state->reset_seq_cnt == 0) 759 state->reset_canceled = false; 760 } else if (value == 1) { 761 /* key press, not autorepeat */ 762 if (++state->reset_seq_cnt == state->reset_seq_len && 763 !state->reset_canceled) { 764 sysrq_handle_reset_request(state); 765 } 766 } 767 } 768 769 #ifdef CONFIG_OF 770 static void sysrq_of_get_keyreset_config(void) 771 { 772 u32 key; 773 struct device_node *np; 774 struct property *prop; 775 const __be32 *p; 776 777 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 778 if (!np) { 779 pr_debug("No sysrq node found"); 780 return; 781 } 782 783 /* Reset in case a __weak definition was present */ 784 sysrq_reset_seq_len = 0; 785 786 of_property_for_each_u32(np, "keyset", prop, p, key) { 787 if (key == KEY_RESERVED || key > KEY_MAX || 788 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 789 break; 790 791 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 792 } 793 794 /* Get reset timeout if any. */ 795 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 796 797 of_node_put(np); 798 } 799 #else 800 static void sysrq_of_get_keyreset_config(void) 801 { 802 } 803 #endif 804 805 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 806 { 807 struct sysrq_state *sysrq = 808 container_of(work, struct sysrq_state, reinject_work); 809 struct input_handle *handle = &sysrq->handle; 810 unsigned int alt_code = sysrq->alt_use; 811 812 if (sysrq->need_reinject) { 813 /* we do not want the assignment to be reordered */ 814 sysrq->reinjecting = true; 815 mb(); 816 817 /* Simulate press and release of Alt + SysRq */ 818 input_inject_event(handle, EV_KEY, alt_code, 1); 819 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 820 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 821 822 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 823 input_inject_event(handle, EV_KEY, alt_code, 0); 824 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 825 826 mb(); 827 sysrq->reinjecting = false; 828 } 829 } 830 831 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 832 unsigned int code, int value) 833 { 834 bool was_active = sysrq->active; 835 bool suppress; 836 837 switch (code) { 838 839 case KEY_LEFTALT: 840 case KEY_RIGHTALT: 841 if (!value) { 842 /* One of ALTs is being released */ 843 if (sysrq->active && code == sysrq->alt_use) 844 sysrq->active = false; 845 846 sysrq->alt = KEY_RESERVED; 847 848 } else if (value != 2) { 849 sysrq->alt = code; 850 sysrq->need_reinject = false; 851 } 852 break; 853 854 case KEY_LEFTSHIFT: 855 case KEY_RIGHTSHIFT: 856 if (!value) 857 sysrq->shift = KEY_RESERVED; 858 else if (value != 2) 859 sysrq->shift = code; 860 if (sysrq->active) 861 sysrq->shift_use = sysrq->shift; 862 break; 863 864 case KEY_SYSRQ: 865 if (value == 1 && sysrq->alt != KEY_RESERVED) { 866 sysrq->active = true; 867 sysrq->alt_use = sysrq->alt; 868 /* either RESERVED (for released) or actual code */ 869 sysrq->shift_use = sysrq->shift; 870 /* 871 * If nothing else will be pressed we'll need 872 * to re-inject Alt-SysRq keysroke. 873 */ 874 sysrq->need_reinject = true; 875 } 876 877 /* 878 * Pretend that sysrq was never pressed at all. This 879 * is needed to properly handle KGDB which will try 880 * to release all keys after exiting debugger. If we 881 * do not clear key bit it KGDB will end up sending 882 * release events for Alt and SysRq, potentially 883 * triggering print screen function. 884 */ 885 if (sysrq->active) 886 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 887 888 break; 889 890 default: 891 if (sysrq->active && value && value != 2) { 892 unsigned char c = sysrq_xlate[code]; 893 894 sysrq->need_reinject = false; 895 if (sysrq->shift_use != KEY_RESERVED) 896 c = toupper(c); 897 __handle_sysrq(c, true); 898 } 899 break; 900 } 901 902 suppress = sysrq->active; 903 904 if (!sysrq->active) { 905 906 /* 907 * See if reset sequence has changed since the last time. 908 */ 909 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 910 sysrq_parse_reset_sequence(sysrq); 911 912 /* 913 * If we are not suppressing key presses keep track of 914 * keyboard state so we can release keys that have been 915 * pressed before entering SysRq mode. 916 */ 917 if (value) 918 set_bit(code, sysrq->key_down); 919 else 920 clear_bit(code, sysrq->key_down); 921 922 if (was_active) 923 schedule_work(&sysrq->reinject_work); 924 925 /* Check for reset sequence */ 926 sysrq_detect_reset_sequence(sysrq, code, value); 927 928 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 929 /* 930 * Pass on release events for keys that was pressed before 931 * entering SysRq mode. 932 */ 933 suppress = false; 934 } 935 936 return suppress; 937 } 938 939 static bool sysrq_filter(struct input_handle *handle, 940 unsigned int type, unsigned int code, int value) 941 { 942 struct sysrq_state *sysrq = handle->private; 943 bool suppress; 944 945 /* 946 * Do not filter anything if we are in the process of re-injecting 947 * Alt+SysRq combination. 948 */ 949 if (sysrq->reinjecting) 950 return false; 951 952 switch (type) { 953 954 case EV_SYN: 955 suppress = false; 956 break; 957 958 case EV_KEY: 959 suppress = sysrq_handle_keypress(sysrq, code, value); 960 break; 961 962 default: 963 suppress = sysrq->active; 964 break; 965 } 966 967 return suppress; 968 } 969 970 static int sysrq_connect(struct input_handler *handler, 971 struct input_dev *dev, 972 const struct input_device_id *id) 973 { 974 struct sysrq_state *sysrq; 975 int error; 976 977 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 978 if (!sysrq) 979 return -ENOMEM; 980 981 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 982 983 sysrq->handle.dev = dev; 984 sysrq->handle.handler = handler; 985 sysrq->handle.name = "sysrq"; 986 sysrq->handle.private = sysrq; 987 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 988 989 error = input_register_handle(&sysrq->handle); 990 if (error) { 991 pr_err("Failed to register input sysrq handler, error %d\n", 992 error); 993 goto err_free; 994 } 995 996 error = input_open_device(&sysrq->handle); 997 if (error) { 998 pr_err("Failed to open input device, error %d\n", error); 999 goto err_unregister; 1000 } 1001 1002 return 0; 1003 1004 err_unregister: 1005 input_unregister_handle(&sysrq->handle); 1006 err_free: 1007 kfree(sysrq); 1008 return error; 1009 } 1010 1011 static void sysrq_disconnect(struct input_handle *handle) 1012 { 1013 struct sysrq_state *sysrq = handle->private; 1014 1015 input_close_device(handle); 1016 cancel_work_sync(&sysrq->reinject_work); 1017 timer_shutdown_sync(&sysrq->keyreset_timer); 1018 input_unregister_handle(handle); 1019 kfree(sysrq); 1020 } 1021 1022 /* 1023 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 1024 * keyboards have SysRq key predefined and so user may add it to keymap 1025 * later, but we expect all such keyboards to have left alt. 1026 */ 1027 static const struct input_device_id sysrq_ids[] = { 1028 { 1029 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 1030 INPUT_DEVICE_ID_MATCH_KEYBIT, 1031 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 1032 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 1033 }, 1034 { }, 1035 }; 1036 1037 static struct input_handler sysrq_handler = { 1038 .filter = sysrq_filter, 1039 .connect = sysrq_connect, 1040 .disconnect = sysrq_disconnect, 1041 .name = "sysrq", 1042 .id_table = sysrq_ids, 1043 }; 1044 1045 static inline void sysrq_register_handler(void) 1046 { 1047 int error; 1048 1049 sysrq_of_get_keyreset_config(); 1050 1051 error = input_register_handler(&sysrq_handler); 1052 if (error) 1053 pr_err("Failed to register input handler, error %d", error); 1054 } 1055 1056 static inline void sysrq_unregister_handler(void) 1057 { 1058 input_unregister_handler(&sysrq_handler); 1059 } 1060 1061 static int sysrq_reset_seq_param_set(const char *buffer, 1062 const struct kernel_param *kp) 1063 { 1064 unsigned long val; 1065 int error; 1066 1067 error = kstrtoul(buffer, 0, &val); 1068 if (error < 0) 1069 return error; 1070 1071 if (val > KEY_MAX) 1072 return -EINVAL; 1073 1074 *((unsigned short *)kp->arg) = val; 1075 sysrq_reset_seq_version++; 1076 1077 return 0; 1078 } 1079 1080 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1081 .get = param_get_ushort, 1082 .set = sysrq_reset_seq_param_set, 1083 }; 1084 1085 #define param_check_sysrq_reset_seq(name, p) \ 1086 __param_check(name, p, unsigned short) 1087 1088 /* 1089 * not really modular, but the easiest way to keep compat with existing 1090 * bootargs behaviour is to continue using module_param here. 1091 */ 1092 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1093 &sysrq_reset_seq_len, 0644); 1094 1095 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1096 1097 #else 1098 1099 static inline void sysrq_register_handler(void) 1100 { 1101 } 1102 1103 static inline void sysrq_unregister_handler(void) 1104 { 1105 } 1106 1107 #endif /* CONFIG_INPUT */ 1108 1109 int sysrq_toggle_support(int enable_mask) 1110 { 1111 bool was_enabled = sysrq_on(); 1112 1113 sysrq_enabled = enable_mask; 1114 1115 if (was_enabled != sysrq_on()) { 1116 if (sysrq_on()) 1117 sysrq_register_handler(); 1118 else 1119 sysrq_unregister_handler(); 1120 } 1121 1122 return 0; 1123 } 1124 EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1125 1126 static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p, 1127 const struct sysrq_key_op *remove_op_p) 1128 { 1129 int retval; 1130 1131 spin_lock(&sysrq_key_table_lock); 1132 if (__sysrq_get_key_op(key) == remove_op_p) { 1133 __sysrq_put_key_op(key, insert_op_p); 1134 retval = 0; 1135 } else { 1136 retval = -1; 1137 } 1138 spin_unlock(&sysrq_key_table_lock); 1139 1140 /* 1141 * A concurrent __handle_sysrq either got the old op or the new op. 1142 * Wait for it to go away before returning, so the code for an old 1143 * op is not freed (eg. on module unload) while it is in use. 1144 */ 1145 synchronize_rcu(); 1146 1147 return retval; 1148 } 1149 1150 int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p) 1151 { 1152 return __sysrq_swap_key_ops(key, op_p, NULL); 1153 } 1154 EXPORT_SYMBOL(register_sysrq_key); 1155 1156 int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p) 1157 { 1158 return __sysrq_swap_key_ops(key, NULL, op_p); 1159 } 1160 EXPORT_SYMBOL(unregister_sysrq_key); 1161 1162 #ifdef CONFIG_PROC_FS 1163 /* 1164 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1165 * Normally, only the first character written is processed. 1166 * However, if the first character is an underscore, 1167 * all characters are processed. 1168 */ 1169 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1170 size_t count, loff_t *ppos) 1171 { 1172 bool bulk = false; 1173 size_t i; 1174 1175 for (i = 0; i < count; i++) { 1176 char c; 1177 1178 if (get_user(c, buf + i)) 1179 return -EFAULT; 1180 1181 if (c == '_') 1182 bulk = true; 1183 else 1184 __handle_sysrq(c, false); 1185 1186 if (!bulk) 1187 break; 1188 } 1189 1190 return count; 1191 } 1192 1193 static const struct proc_ops sysrq_trigger_proc_ops = { 1194 .proc_write = write_sysrq_trigger, 1195 .proc_lseek = noop_llseek, 1196 }; 1197 1198 static void sysrq_init_procfs(void) 1199 { 1200 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1201 &sysrq_trigger_proc_ops)) 1202 pr_err("Failed to register proc interface\n"); 1203 } 1204 1205 #else 1206 1207 static inline void sysrq_init_procfs(void) 1208 { 1209 } 1210 1211 #endif /* CONFIG_PROC_FS */ 1212 1213 static int __init sysrq_init(void) 1214 { 1215 sysrq_init_procfs(); 1216 1217 if (sysrq_on()) 1218 sysrq_register_handler(); 1219 1220 return 0; 1221 } 1222 device_initcall(sysrq_init); 1223