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_try_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 NULL, /* S */ 535 NULL, /* T */ 536 NULL, /* U */ 537 NULL, /* V */ 538 NULL, /* W */ 539 NULL, /* X */ 540 NULL, /* Y */ 541 NULL, /* Z */ 542 }; 543 544 /* key2index calculation, -1 on invalid index */ 545 static int sysrq_key_table_key2index(u8 key) 546 { 547 switch (key) { 548 case '0' ... '9': 549 return key - '0'; 550 case 'a' ... 'z': 551 return key - 'a' + 10; 552 case 'A' ... 'Z': 553 return key - 'A' + 10 + 26; 554 default: 555 return -1; 556 } 557 } 558 559 /* 560 * get and put functions for the table, exposed to modules. 561 */ 562 static const struct sysrq_key_op *__sysrq_get_key_op(u8 key) 563 { 564 const struct sysrq_key_op *op_p = NULL; 565 int i; 566 567 i = sysrq_key_table_key2index(key); 568 if (i != -1) 569 op_p = sysrq_key_table[i]; 570 571 return op_p; 572 } 573 574 static void __sysrq_put_key_op(u8 key, const struct sysrq_key_op *op_p) 575 { 576 int i = sysrq_key_table_key2index(key); 577 578 if (i != -1) 579 sysrq_key_table[i] = op_p; 580 } 581 582 void __handle_sysrq(u8 key, bool check_mask) 583 { 584 const struct sysrq_key_op *op_p; 585 int orig_log_level; 586 int orig_suppress_printk; 587 int i; 588 589 orig_suppress_printk = suppress_printk; 590 suppress_printk = 0; 591 592 rcu_sysrq_start(); 593 rcu_read_lock(); 594 /* 595 * Raise the apparent loglevel to maximum so that the sysrq header 596 * is shown to provide the user with positive feedback. We do not 597 * simply emit this at KERN_EMERG as that would change message 598 * routing in the consumers of /proc/kmsg. 599 */ 600 orig_log_level = console_loglevel; 601 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 602 603 op_p = __sysrq_get_key_op(key); 604 if (op_p) { 605 /* 606 * Should we check for enabled operations (/proc/sysrq-trigger 607 * should not) and is the invoked operation enabled? 608 */ 609 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 610 pr_info("%s\n", op_p->action_msg); 611 console_loglevel = orig_log_level; 612 op_p->handler(key); 613 } else { 614 pr_info("This sysrq operation is disabled.\n"); 615 console_loglevel = orig_log_level; 616 } 617 } else { 618 pr_info("HELP : "); 619 /* Only print the help msg once per handler */ 620 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 621 if (sysrq_key_table[i]) { 622 int j; 623 624 for (j = 0; sysrq_key_table[i] != 625 sysrq_key_table[j]; j++) 626 ; 627 if (j != i) 628 continue; 629 pr_cont("%s ", sysrq_key_table[i]->help_msg); 630 } 631 } 632 pr_cont("\n"); 633 console_loglevel = orig_log_level; 634 } 635 rcu_read_unlock(); 636 rcu_sysrq_end(); 637 638 suppress_printk = orig_suppress_printk; 639 } 640 641 void handle_sysrq(u8 key) 642 { 643 if (sysrq_on()) 644 __handle_sysrq(key, true); 645 } 646 EXPORT_SYMBOL(handle_sysrq); 647 648 #ifdef CONFIG_INPUT 649 static int sysrq_reset_downtime_ms; 650 651 /* Simple translation table for the SysRq keys */ 652 static const unsigned char sysrq_xlate[KEY_CNT] = 653 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 654 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 655 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 656 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 657 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 658 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 659 "\r\000/"; /* 0x60 - 0x6f */ 660 661 struct sysrq_state { 662 struct input_handle handle; 663 struct work_struct reinject_work; 664 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 665 unsigned int alt; 666 unsigned int alt_use; 667 unsigned int shift; 668 unsigned int shift_use; 669 bool active; 670 bool need_reinject; 671 bool reinjecting; 672 673 /* reset sequence handling */ 674 bool reset_canceled; 675 bool reset_requested; 676 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 677 int reset_seq_len; 678 int reset_seq_cnt; 679 int reset_seq_version; 680 struct timer_list keyreset_timer; 681 }; 682 683 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 684 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 685 static unsigned int sysrq_reset_seq_len; 686 static unsigned int sysrq_reset_seq_version = 1; 687 688 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 689 { 690 int i; 691 unsigned short key; 692 693 state->reset_seq_cnt = 0; 694 695 for (i = 0; i < sysrq_reset_seq_len; i++) { 696 key = sysrq_reset_seq[i]; 697 698 if (key == KEY_RESERVED || key > KEY_MAX) 699 break; 700 701 __set_bit(key, state->reset_keybit); 702 state->reset_seq_len++; 703 704 if (test_bit(key, state->key_down)) 705 state->reset_seq_cnt++; 706 } 707 708 /* Disable reset until old keys are not released */ 709 state->reset_canceled = state->reset_seq_cnt != 0; 710 711 state->reset_seq_version = sysrq_reset_seq_version; 712 } 713 714 static void sysrq_do_reset(struct timer_list *t) 715 { 716 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 717 718 state->reset_requested = true; 719 720 orderly_reboot(); 721 } 722 723 static void sysrq_handle_reset_request(struct sysrq_state *state) 724 { 725 if (state->reset_requested) 726 __handle_sysrq(sysrq_xlate[KEY_B], false); 727 728 if (sysrq_reset_downtime_ms) 729 mod_timer(&state->keyreset_timer, 730 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 731 else 732 sysrq_do_reset(&state->keyreset_timer); 733 } 734 735 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 736 unsigned int code, int value) 737 { 738 if (!test_bit(code, state->reset_keybit)) { 739 /* 740 * Pressing any key _not_ in reset sequence cancels 741 * the reset sequence. Also cancelling the timer in 742 * case additional keys were pressed after a reset 743 * has been requested. 744 */ 745 if (value && state->reset_seq_cnt) { 746 state->reset_canceled = true; 747 del_timer(&state->keyreset_timer); 748 } 749 } else if (value == 0) { 750 /* 751 * Key release - all keys in the reset sequence need 752 * to be pressed and held for the reset timeout 753 * to hold. 754 */ 755 del_timer(&state->keyreset_timer); 756 757 if (--state->reset_seq_cnt == 0) 758 state->reset_canceled = false; 759 } else if (value == 1) { 760 /* key press, not autorepeat */ 761 if (++state->reset_seq_cnt == state->reset_seq_len && 762 !state->reset_canceled) { 763 sysrq_handle_reset_request(state); 764 } 765 } 766 } 767 768 #ifdef CONFIG_OF 769 static void sysrq_of_get_keyreset_config(void) 770 { 771 u32 key; 772 struct device_node *np; 773 774 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 775 if (!np) { 776 pr_debug("No sysrq node found"); 777 return; 778 } 779 780 /* Reset in case a __weak definition was present */ 781 sysrq_reset_seq_len = 0; 782 783 of_property_for_each_u32(np, "keyset", key) { 784 if (key == KEY_RESERVED || key > KEY_MAX || 785 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 786 break; 787 788 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 789 } 790 791 /* Get reset timeout if any. */ 792 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 793 794 of_node_put(np); 795 } 796 #else 797 static void sysrq_of_get_keyreset_config(void) 798 { 799 } 800 #endif 801 802 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 803 { 804 struct sysrq_state *sysrq = 805 container_of(work, struct sysrq_state, reinject_work); 806 struct input_handle *handle = &sysrq->handle; 807 unsigned int alt_code = sysrq->alt_use; 808 809 if (sysrq->need_reinject) { 810 /* we do not want the assignment to be reordered */ 811 sysrq->reinjecting = true; 812 mb(); 813 814 /* Simulate press and release of Alt + SysRq */ 815 input_inject_event(handle, EV_KEY, alt_code, 1); 816 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 817 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 818 819 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 820 input_inject_event(handle, EV_KEY, alt_code, 0); 821 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 822 823 mb(); 824 sysrq->reinjecting = false; 825 } 826 } 827 828 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 829 unsigned int code, int value) 830 { 831 bool was_active = sysrq->active; 832 bool suppress; 833 834 switch (code) { 835 836 case KEY_LEFTALT: 837 case KEY_RIGHTALT: 838 if (!value) { 839 /* One of ALTs is being released */ 840 if (sysrq->active && code == sysrq->alt_use) 841 sysrq->active = false; 842 843 sysrq->alt = KEY_RESERVED; 844 845 } else if (value != 2) { 846 sysrq->alt = code; 847 sysrq->need_reinject = false; 848 } 849 break; 850 851 case KEY_LEFTSHIFT: 852 case KEY_RIGHTSHIFT: 853 if (!value) 854 sysrq->shift = KEY_RESERVED; 855 else if (value != 2) 856 sysrq->shift = code; 857 if (sysrq->active) 858 sysrq->shift_use = sysrq->shift; 859 break; 860 861 case KEY_SYSRQ: 862 if (value == 1 && sysrq->alt != KEY_RESERVED) { 863 sysrq->active = true; 864 sysrq->alt_use = sysrq->alt; 865 /* either RESERVED (for released) or actual code */ 866 sysrq->shift_use = sysrq->shift; 867 /* 868 * If nothing else will be pressed we'll need 869 * to re-inject Alt-SysRq keysroke. 870 */ 871 sysrq->need_reinject = true; 872 } 873 874 /* 875 * Pretend that sysrq was never pressed at all. This 876 * is needed to properly handle KGDB which will try 877 * to release all keys after exiting debugger. If we 878 * do not clear key bit it KGDB will end up sending 879 * release events for Alt and SysRq, potentially 880 * triggering print screen function. 881 */ 882 if (sysrq->active) 883 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 884 885 break; 886 887 default: 888 if (sysrq->active && value && value != 2) { 889 unsigned char c = sysrq_xlate[code]; 890 891 sysrq->need_reinject = false; 892 if (sysrq->shift_use != KEY_RESERVED) 893 c = toupper(c); 894 __handle_sysrq(c, true); 895 } 896 break; 897 } 898 899 suppress = sysrq->active; 900 901 if (!sysrq->active) { 902 903 /* 904 * See if reset sequence has changed since the last time. 905 */ 906 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 907 sysrq_parse_reset_sequence(sysrq); 908 909 /* 910 * If we are not suppressing key presses keep track of 911 * keyboard state so we can release keys that have been 912 * pressed before entering SysRq mode. 913 */ 914 if (value) 915 set_bit(code, sysrq->key_down); 916 else 917 clear_bit(code, sysrq->key_down); 918 919 if (was_active) 920 schedule_work(&sysrq->reinject_work); 921 922 /* Check for reset sequence */ 923 sysrq_detect_reset_sequence(sysrq, code, value); 924 925 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 926 /* 927 * Pass on release events for keys that was pressed before 928 * entering SysRq mode. 929 */ 930 suppress = false; 931 } 932 933 return suppress; 934 } 935 936 static bool sysrq_filter(struct input_handle *handle, 937 unsigned int type, unsigned int code, int value) 938 { 939 struct sysrq_state *sysrq = handle->private; 940 bool suppress; 941 942 /* 943 * Do not filter anything if we are in the process of re-injecting 944 * Alt+SysRq combination. 945 */ 946 if (sysrq->reinjecting) 947 return false; 948 949 switch (type) { 950 951 case EV_SYN: 952 suppress = false; 953 break; 954 955 case EV_KEY: 956 suppress = sysrq_handle_keypress(sysrq, code, value); 957 break; 958 959 default: 960 suppress = sysrq->active; 961 break; 962 } 963 964 return suppress; 965 } 966 967 static int sysrq_connect(struct input_handler *handler, 968 struct input_dev *dev, 969 const struct input_device_id *id) 970 { 971 struct sysrq_state *sysrq; 972 int error; 973 974 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 975 if (!sysrq) 976 return -ENOMEM; 977 978 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 979 980 sysrq->handle.dev = dev; 981 sysrq->handle.handler = handler; 982 sysrq->handle.name = "sysrq"; 983 sysrq->handle.private = sysrq; 984 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 985 986 error = input_register_handle(&sysrq->handle); 987 if (error) { 988 pr_err("Failed to register input sysrq handler, error %d\n", 989 error); 990 goto err_free; 991 } 992 993 error = input_open_device(&sysrq->handle); 994 if (error) { 995 pr_err("Failed to open input device, error %d\n", error); 996 goto err_unregister; 997 } 998 999 return 0; 1000 1001 err_unregister: 1002 input_unregister_handle(&sysrq->handle); 1003 err_free: 1004 kfree(sysrq); 1005 return error; 1006 } 1007 1008 static void sysrq_disconnect(struct input_handle *handle) 1009 { 1010 struct sysrq_state *sysrq = handle->private; 1011 1012 input_close_device(handle); 1013 cancel_work_sync(&sysrq->reinject_work); 1014 timer_shutdown_sync(&sysrq->keyreset_timer); 1015 input_unregister_handle(handle); 1016 kfree(sysrq); 1017 } 1018 1019 /* 1020 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 1021 * keyboards have SysRq key predefined and so user may add it to keymap 1022 * later, but we expect all such keyboards to have left alt. 1023 */ 1024 static const struct input_device_id sysrq_ids[] = { 1025 { 1026 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 1027 INPUT_DEVICE_ID_MATCH_KEYBIT, 1028 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 1029 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 1030 }, 1031 { }, 1032 }; 1033 1034 static struct input_handler sysrq_handler = { 1035 .filter = sysrq_filter, 1036 .connect = sysrq_connect, 1037 .disconnect = sysrq_disconnect, 1038 .name = "sysrq", 1039 .id_table = sysrq_ids, 1040 }; 1041 1042 static inline void sysrq_register_handler(void) 1043 { 1044 int error; 1045 1046 sysrq_of_get_keyreset_config(); 1047 1048 error = input_register_handler(&sysrq_handler); 1049 if (error) 1050 pr_err("Failed to register input handler, error %d", error); 1051 } 1052 1053 static inline void sysrq_unregister_handler(void) 1054 { 1055 input_unregister_handler(&sysrq_handler); 1056 } 1057 1058 static int sysrq_reset_seq_param_set(const char *buffer, 1059 const struct kernel_param *kp) 1060 { 1061 unsigned long val; 1062 int error; 1063 1064 error = kstrtoul(buffer, 0, &val); 1065 if (error < 0) 1066 return error; 1067 1068 if (val > KEY_MAX) 1069 return -EINVAL; 1070 1071 *((unsigned short *)kp->arg) = val; 1072 sysrq_reset_seq_version++; 1073 1074 return 0; 1075 } 1076 1077 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1078 .get = param_get_ushort, 1079 .set = sysrq_reset_seq_param_set, 1080 }; 1081 1082 #define param_check_sysrq_reset_seq(name, p) \ 1083 __param_check(name, p, unsigned short) 1084 1085 /* 1086 * not really modular, but the easiest way to keep compat with existing 1087 * bootargs behaviour is to continue using module_param here. 1088 */ 1089 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1090 &sysrq_reset_seq_len, 0644); 1091 1092 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1093 1094 #else 1095 1096 static inline void sysrq_register_handler(void) 1097 { 1098 } 1099 1100 static inline void sysrq_unregister_handler(void) 1101 { 1102 } 1103 1104 #endif /* CONFIG_INPUT */ 1105 1106 int sysrq_toggle_support(int enable_mask) 1107 { 1108 bool was_enabled = sysrq_on(); 1109 1110 sysrq_enabled = enable_mask; 1111 1112 if (was_enabled != sysrq_on()) { 1113 if (sysrq_on()) 1114 sysrq_register_handler(); 1115 else 1116 sysrq_unregister_handler(); 1117 } 1118 1119 return 0; 1120 } 1121 EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1122 1123 static int __sysrq_swap_key_ops(u8 key, const struct sysrq_key_op *insert_op_p, 1124 const struct sysrq_key_op *remove_op_p) 1125 { 1126 int retval; 1127 1128 spin_lock(&sysrq_key_table_lock); 1129 if (__sysrq_get_key_op(key) == remove_op_p) { 1130 __sysrq_put_key_op(key, insert_op_p); 1131 retval = 0; 1132 } else { 1133 retval = -1; 1134 } 1135 spin_unlock(&sysrq_key_table_lock); 1136 1137 /* 1138 * A concurrent __handle_sysrq either got the old op or the new op. 1139 * Wait for it to go away before returning, so the code for an old 1140 * op is not freed (eg. on module unload) while it is in use. 1141 */ 1142 synchronize_rcu(); 1143 1144 return retval; 1145 } 1146 1147 int register_sysrq_key(u8 key, const struct sysrq_key_op *op_p) 1148 { 1149 return __sysrq_swap_key_ops(key, op_p, NULL); 1150 } 1151 EXPORT_SYMBOL(register_sysrq_key); 1152 1153 int unregister_sysrq_key(u8 key, const struct sysrq_key_op *op_p) 1154 { 1155 return __sysrq_swap_key_ops(key, NULL, op_p); 1156 } 1157 EXPORT_SYMBOL(unregister_sysrq_key); 1158 1159 #ifdef CONFIG_PROC_FS 1160 /* 1161 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1162 * Normally, only the first character written is processed. 1163 * However, if the first character is an underscore, 1164 * all characters are processed. 1165 */ 1166 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1167 size_t count, loff_t *ppos) 1168 { 1169 bool bulk = false; 1170 size_t i; 1171 1172 for (i = 0; i < count; i++) { 1173 char c; 1174 1175 if (get_user(c, buf + i)) 1176 return -EFAULT; 1177 1178 if (c == '_') 1179 bulk = true; 1180 else 1181 __handle_sysrq(c, false); 1182 1183 if (!bulk) 1184 break; 1185 } 1186 1187 return count; 1188 } 1189 1190 static const struct proc_ops sysrq_trigger_proc_ops = { 1191 .proc_write = write_sysrq_trigger, 1192 .proc_lseek = noop_llseek, 1193 }; 1194 1195 static void sysrq_init_procfs(void) 1196 { 1197 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1198 &sysrq_trigger_proc_ops)) 1199 pr_err("Failed to register proc interface\n"); 1200 } 1201 1202 #else 1203 1204 static inline void sysrq_init_procfs(void) 1205 { 1206 } 1207 1208 #endif /* CONFIG_PROC_FS */ 1209 1210 static int __init sysrq_init(void) 1211 { 1212 sysrq_init_procfs(); 1213 1214 if (sysrq_on()) 1215 sysrq_register_handler(); 1216 1217 return 0; 1218 } 1219 device_initcall(sysrq_init); 1220