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/interrupt.h> 23 #include <linux/mm.h> 24 #include <linux/fs.h> 25 #include <linux/mount.h> 26 #include <linux/kdev_t.h> 27 #include <linux/major.h> 28 #include <linux/reboot.h> 29 #include <linux/sysrq.h> 30 #include <linux/kbd_kern.h> 31 #include <linux/proc_fs.h> 32 #include <linux/nmi.h> 33 #include <linux/quotaops.h> 34 #include <linux/perf_event.h> 35 #include <linux/kernel.h> 36 #include <linux/module.h> 37 #include <linux/suspend.h> 38 #include <linux/writeback.h> 39 #include <linux/swap.h> 40 #include <linux/spinlock.h> 41 #include <linux/vt_kern.h> 42 #include <linux/workqueue.h> 43 #include <linux/hrtimer.h> 44 #include <linux/oom.h> 45 #include <linux/slab.h> 46 #include <linux/input.h> 47 #include <linux/uaccess.h> 48 #include <linux/moduleparam.h> 49 #include <linux/jiffies.h> 50 #include <linux/syscalls.h> 51 #include <linux/of.h> 52 #include <linux/rcupdate.h> 53 54 #include <asm/ptrace.h> 55 #include <asm/irq_regs.h> 56 57 /* Whether we react on sysrq keys or just ignore them */ 58 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; 59 static bool __read_mostly sysrq_always_enabled; 60 61 static bool sysrq_on(void) 62 { 63 return sysrq_enabled || sysrq_always_enabled; 64 } 65 66 /** 67 * sysrq_mask - Getter for sysrq_enabled mask. 68 * 69 * Return: 1 if sysrq is always enabled, enabled sysrq_key_op mask otherwise. 70 */ 71 int sysrq_mask(void) 72 { 73 if (sysrq_always_enabled) 74 return 1; 75 return sysrq_enabled; 76 } 77 EXPORT_SYMBOL_GPL(sysrq_mask); 78 79 /* 80 * A value of 1 means 'all', other nonzero values are an op mask: 81 */ 82 static bool sysrq_on_mask(int mask) 83 { 84 return sysrq_always_enabled || 85 sysrq_enabled == 1 || 86 (sysrq_enabled & mask); 87 } 88 89 static int __init sysrq_always_enabled_setup(char *str) 90 { 91 sysrq_always_enabled = true; 92 pr_info("sysrq always enabled.\n"); 93 94 return 1; 95 } 96 97 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 98 99 100 static void sysrq_handle_loglevel(int key) 101 { 102 int i; 103 104 i = key - '0'; 105 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 106 pr_info("Loglevel set to %d\n", i); 107 console_loglevel = i; 108 } 109 static 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(int key) 118 { 119 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 120 schedule_work(SAK_work); 121 } 122 static struct sysrq_key_op sysrq_SAK_op = { 123 .handler = sysrq_handle_SAK, 124 .help_msg = "sak(k)", 125 .action_msg = "SAK", 126 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 127 }; 128 #else 129 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL) 130 #endif 131 132 #ifdef CONFIG_VT 133 static void sysrq_handle_unraw(int key) 134 { 135 vt_reset_unicode(fg_console); 136 } 137 138 static struct sysrq_key_op sysrq_unraw_op = { 139 .handler = sysrq_handle_unraw, 140 .help_msg = "unraw(r)", 141 .action_msg = "Keyboard mode set to system default", 142 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 143 }; 144 #else 145 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL) 146 #endif /* CONFIG_VT */ 147 148 static void sysrq_handle_crash(int key) 149 { 150 /* release the RCU read lock before crashing */ 151 rcu_read_unlock(); 152 153 panic("sysrq triggered crash\n"); 154 } 155 static struct sysrq_key_op sysrq_crash_op = { 156 .handler = sysrq_handle_crash, 157 .help_msg = "crash(c)", 158 .action_msg = "Trigger a crash", 159 .enable_mask = SYSRQ_ENABLE_DUMP, 160 }; 161 162 static void sysrq_handle_reboot(int key) 163 { 164 lockdep_off(); 165 local_irq_enable(); 166 emergency_restart(); 167 } 168 static struct sysrq_key_op sysrq_reboot_op = { 169 .handler = sysrq_handle_reboot, 170 .help_msg = "reboot(b)", 171 .action_msg = "Resetting", 172 .enable_mask = SYSRQ_ENABLE_BOOT, 173 }; 174 175 static void sysrq_handle_sync(int key) 176 { 177 emergency_sync(); 178 } 179 static struct sysrq_key_op sysrq_sync_op = { 180 .handler = sysrq_handle_sync, 181 .help_msg = "sync(s)", 182 .action_msg = "Emergency Sync", 183 .enable_mask = SYSRQ_ENABLE_SYNC, 184 }; 185 186 static void sysrq_handle_show_timers(int key) 187 { 188 sysrq_timer_list_show(); 189 } 190 191 static struct sysrq_key_op sysrq_show_timers_op = { 192 .handler = sysrq_handle_show_timers, 193 .help_msg = "show-all-timers(q)", 194 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 195 }; 196 197 static void sysrq_handle_mountro(int key) 198 { 199 emergency_remount(); 200 } 201 static struct sysrq_key_op sysrq_mountro_op = { 202 .handler = sysrq_handle_mountro, 203 .help_msg = "unmount(u)", 204 .action_msg = "Emergency Remount R/O", 205 .enable_mask = SYSRQ_ENABLE_REMOUNT, 206 }; 207 208 #ifdef CONFIG_LOCKDEP 209 static void sysrq_handle_showlocks(int key) 210 { 211 debug_show_all_locks(); 212 } 213 214 static struct sysrq_key_op sysrq_showlocks_op = { 215 .handler = sysrq_handle_showlocks, 216 .help_msg = "show-all-locks(d)", 217 .action_msg = "Show Locks Held", 218 }; 219 #else 220 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 221 #endif 222 223 #ifdef CONFIG_SMP 224 static DEFINE_RAW_SPINLOCK(show_lock); 225 226 static void showacpu(void *dummy) 227 { 228 unsigned long flags; 229 230 /* Idle CPUs have no interesting backtrace. */ 231 if (idle_cpu(smp_processor_id())) 232 return; 233 234 raw_spin_lock_irqsave(&show_lock, flags); 235 pr_info("CPU%d:\n", smp_processor_id()); 236 show_stack(NULL, NULL); 237 raw_spin_unlock_irqrestore(&show_lock, flags); 238 } 239 240 static void sysrq_showregs_othercpus(struct work_struct *dummy) 241 { 242 smp_call_function(showacpu, NULL, 0); 243 } 244 245 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 246 247 static void sysrq_handle_showallcpus(int key) 248 { 249 /* 250 * Fall back to the workqueue based printing if the 251 * backtrace printing did not succeed or the 252 * architecture has no support for it: 253 */ 254 if (!trigger_all_cpu_backtrace()) { 255 struct pt_regs *regs = NULL; 256 257 if (in_irq()) 258 regs = get_irq_regs(); 259 if (regs) { 260 pr_info("CPU%d:\n", smp_processor_id()); 261 show_regs(regs); 262 } 263 schedule_work(&sysrq_showallcpus); 264 } 265 } 266 267 static struct sysrq_key_op sysrq_showallcpus_op = { 268 .handler = sysrq_handle_showallcpus, 269 .help_msg = "show-backtrace-all-active-cpus(l)", 270 .action_msg = "Show backtrace of all active CPUs", 271 .enable_mask = SYSRQ_ENABLE_DUMP, 272 }; 273 #endif 274 275 static void sysrq_handle_showregs(int key) 276 { 277 struct pt_regs *regs = NULL; 278 279 if (in_irq()) 280 regs = get_irq_regs(); 281 if (regs) 282 show_regs(regs); 283 perf_event_print_debug(); 284 } 285 static struct sysrq_key_op sysrq_showregs_op = { 286 .handler = sysrq_handle_showregs, 287 .help_msg = "show-registers(p)", 288 .action_msg = "Show Regs", 289 .enable_mask = SYSRQ_ENABLE_DUMP, 290 }; 291 292 static void sysrq_handle_showstate(int key) 293 { 294 show_state(); 295 show_workqueue_state(); 296 } 297 static struct sysrq_key_op sysrq_showstate_op = { 298 .handler = sysrq_handle_showstate, 299 .help_msg = "show-task-states(t)", 300 .action_msg = "Show State", 301 .enable_mask = SYSRQ_ENABLE_DUMP, 302 }; 303 304 static void sysrq_handle_showstate_blocked(int key) 305 { 306 show_state_filter(TASK_UNINTERRUPTIBLE); 307 } 308 static struct sysrq_key_op sysrq_showstate_blocked_op = { 309 .handler = sysrq_handle_showstate_blocked, 310 .help_msg = "show-blocked-tasks(w)", 311 .action_msg = "Show Blocked State", 312 .enable_mask = SYSRQ_ENABLE_DUMP, 313 }; 314 315 #ifdef CONFIG_TRACING 316 #include <linux/ftrace.h> 317 318 static void sysrq_ftrace_dump(int key) 319 { 320 ftrace_dump(DUMP_ALL); 321 } 322 static struct sysrq_key_op sysrq_ftrace_dump_op = { 323 .handler = sysrq_ftrace_dump, 324 .help_msg = "dump-ftrace-buffer(z)", 325 .action_msg = "Dump ftrace buffer", 326 .enable_mask = SYSRQ_ENABLE_DUMP, 327 }; 328 #else 329 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 330 #endif 331 332 static void sysrq_handle_showmem(int key) 333 { 334 show_mem(0, NULL); 335 } 336 static struct sysrq_key_op sysrq_showmem_op = { 337 .handler = sysrq_handle_showmem, 338 .help_msg = "show-memory-usage(m)", 339 .action_msg = "Show Memory", 340 .enable_mask = SYSRQ_ENABLE_DUMP, 341 }; 342 343 /* 344 * Signal sysrq helper function. Sends a signal to all user processes. 345 */ 346 static void send_sig_all(int sig) 347 { 348 struct task_struct *p; 349 350 read_lock(&tasklist_lock); 351 for_each_process(p) { 352 if (p->flags & PF_KTHREAD) 353 continue; 354 if (is_global_init(p)) 355 continue; 356 357 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX); 358 } 359 read_unlock(&tasklist_lock); 360 } 361 362 static void sysrq_handle_term(int key) 363 { 364 send_sig_all(SIGTERM); 365 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 366 } 367 static struct sysrq_key_op sysrq_term_op = { 368 .handler = sysrq_handle_term, 369 .help_msg = "terminate-all-tasks(e)", 370 .action_msg = "Terminate All Tasks", 371 .enable_mask = SYSRQ_ENABLE_SIGNAL, 372 }; 373 374 static void moom_callback(struct work_struct *ignored) 375 { 376 const gfp_t gfp_mask = GFP_KERNEL; 377 struct oom_control oc = { 378 .zonelist = node_zonelist(first_memory_node, gfp_mask), 379 .nodemask = NULL, 380 .memcg = NULL, 381 .gfp_mask = gfp_mask, 382 .order = -1, 383 }; 384 385 mutex_lock(&oom_lock); 386 if (!out_of_memory(&oc)) 387 pr_info("OOM request ignored. No task eligible\n"); 388 mutex_unlock(&oom_lock); 389 } 390 391 static DECLARE_WORK(moom_work, moom_callback); 392 393 static void sysrq_handle_moom(int key) 394 { 395 schedule_work(&moom_work); 396 } 397 static struct sysrq_key_op sysrq_moom_op = { 398 .handler = sysrq_handle_moom, 399 .help_msg = "memory-full-oom-kill(f)", 400 .action_msg = "Manual OOM execution", 401 .enable_mask = SYSRQ_ENABLE_SIGNAL, 402 }; 403 404 #ifdef CONFIG_BLOCK 405 static void sysrq_handle_thaw(int key) 406 { 407 emergency_thaw_all(); 408 } 409 static struct sysrq_key_op sysrq_thaw_op = { 410 .handler = sysrq_handle_thaw, 411 .help_msg = "thaw-filesystems(j)", 412 .action_msg = "Emergency Thaw of all frozen filesystems", 413 .enable_mask = SYSRQ_ENABLE_SIGNAL, 414 }; 415 #endif 416 417 static void sysrq_handle_kill(int key) 418 { 419 send_sig_all(SIGKILL); 420 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 421 } 422 static struct sysrq_key_op sysrq_kill_op = { 423 .handler = sysrq_handle_kill, 424 .help_msg = "kill-all-tasks(i)", 425 .action_msg = "Kill All Tasks", 426 .enable_mask = SYSRQ_ENABLE_SIGNAL, 427 }; 428 429 static void sysrq_handle_unrt(int key) 430 { 431 normalize_rt_tasks(); 432 } 433 static struct sysrq_key_op sysrq_unrt_op = { 434 .handler = sysrq_handle_unrt, 435 .help_msg = "nice-all-RT-tasks(n)", 436 .action_msg = "Nice All RT Tasks", 437 .enable_mask = SYSRQ_ENABLE_RTNICE, 438 }; 439 440 /* Key Operations table and lock */ 441 static DEFINE_SPINLOCK(sysrq_key_table_lock); 442 443 static struct sysrq_key_op *sysrq_key_table[36] = { 444 &sysrq_loglevel_op, /* 0 */ 445 &sysrq_loglevel_op, /* 1 */ 446 &sysrq_loglevel_op, /* 2 */ 447 &sysrq_loglevel_op, /* 3 */ 448 &sysrq_loglevel_op, /* 4 */ 449 &sysrq_loglevel_op, /* 5 */ 450 &sysrq_loglevel_op, /* 6 */ 451 &sysrq_loglevel_op, /* 7 */ 452 &sysrq_loglevel_op, /* 8 */ 453 &sysrq_loglevel_op, /* 9 */ 454 455 /* 456 * a: Don't use for system provided sysrqs, it is handled specially on 457 * sparc and will never arrive. 458 */ 459 NULL, /* a */ 460 &sysrq_reboot_op, /* b */ 461 &sysrq_crash_op, /* c */ 462 &sysrq_showlocks_op, /* d */ 463 &sysrq_term_op, /* e */ 464 &sysrq_moom_op, /* f */ 465 /* g: May be registered for the kernel debugger */ 466 NULL, /* g */ 467 NULL, /* h - reserved for help */ 468 &sysrq_kill_op, /* i */ 469 #ifdef CONFIG_BLOCK 470 &sysrq_thaw_op, /* j */ 471 #else 472 NULL, /* j */ 473 #endif 474 &sysrq_SAK_op, /* k */ 475 #ifdef CONFIG_SMP 476 &sysrq_showallcpus_op, /* l */ 477 #else 478 NULL, /* l */ 479 #endif 480 &sysrq_showmem_op, /* m */ 481 &sysrq_unrt_op, /* n */ 482 /* o: This will often be registered as 'Off' at init time */ 483 NULL, /* o */ 484 &sysrq_showregs_op, /* p */ 485 &sysrq_show_timers_op, /* q */ 486 &sysrq_unraw_op, /* r */ 487 &sysrq_sync_op, /* s */ 488 &sysrq_showstate_op, /* t */ 489 &sysrq_mountro_op, /* u */ 490 /* v: May be registered for frame buffer console restore */ 491 NULL, /* v */ 492 &sysrq_showstate_blocked_op, /* w */ 493 /* x: May be registered on mips for TLB dump */ 494 /* x: May be registered on ppc/powerpc for xmon */ 495 /* x: May be registered on sparc64 for global PMU dump */ 496 NULL, /* x */ 497 /* y: May be registered on sparc64 for global register dump */ 498 NULL, /* y */ 499 &sysrq_ftrace_dump_op, /* z */ 500 }; 501 502 /* key2index calculation, -1 on invalid index */ 503 static int sysrq_key_table_key2index(int key) 504 { 505 int retval; 506 507 if ((key >= '0') && (key <= '9')) 508 retval = key - '0'; 509 else if ((key >= 'a') && (key <= 'z')) 510 retval = key + 10 - 'a'; 511 else 512 retval = -1; 513 return retval; 514 } 515 516 /* 517 * get and put functions for the table, exposed to modules. 518 */ 519 struct sysrq_key_op *__sysrq_get_key_op(int key) 520 { 521 struct sysrq_key_op *op_p = NULL; 522 int i; 523 524 i = sysrq_key_table_key2index(key); 525 if (i != -1) 526 op_p = sysrq_key_table[i]; 527 528 return op_p; 529 } 530 531 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 532 { 533 int i = sysrq_key_table_key2index(key); 534 535 if (i != -1) 536 sysrq_key_table[i] = op_p; 537 } 538 539 void __handle_sysrq(int key, bool check_mask) 540 { 541 struct sysrq_key_op *op_p; 542 int orig_log_level; 543 int orig_suppress_printk; 544 int i; 545 546 orig_suppress_printk = suppress_printk; 547 suppress_printk = 0; 548 549 rcu_sysrq_start(); 550 rcu_read_lock(); 551 /* 552 * Raise the apparent loglevel to maximum so that the sysrq header 553 * is shown to provide the user with positive feedback. We do not 554 * simply emit this at KERN_EMERG as that would change message 555 * routing in the consumers of /proc/kmsg. 556 */ 557 orig_log_level = console_loglevel; 558 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 559 560 op_p = __sysrq_get_key_op(key); 561 if (op_p) { 562 /* 563 * Should we check for enabled operations (/proc/sysrq-trigger 564 * should not) and is the invoked operation enabled? 565 */ 566 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 567 pr_info("%s\n", op_p->action_msg); 568 console_loglevel = orig_log_level; 569 op_p->handler(key); 570 } else { 571 pr_info("This sysrq operation is disabled.\n"); 572 console_loglevel = orig_log_level; 573 } 574 } else { 575 pr_info("HELP : "); 576 /* Only print the help msg once per handler */ 577 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 578 if (sysrq_key_table[i]) { 579 int j; 580 581 for (j = 0; sysrq_key_table[i] != 582 sysrq_key_table[j]; j++) 583 ; 584 if (j != i) 585 continue; 586 pr_cont("%s ", sysrq_key_table[i]->help_msg); 587 } 588 } 589 pr_cont("\n"); 590 console_loglevel = orig_log_level; 591 } 592 rcu_read_unlock(); 593 rcu_sysrq_end(); 594 595 suppress_printk = orig_suppress_printk; 596 } 597 598 void handle_sysrq(int key) 599 { 600 if (sysrq_on()) 601 __handle_sysrq(key, true); 602 } 603 EXPORT_SYMBOL(handle_sysrq); 604 605 #ifdef CONFIG_INPUT 606 static int sysrq_reset_downtime_ms; 607 608 /* Simple translation table for the SysRq keys */ 609 static const unsigned char sysrq_xlate[KEY_CNT] = 610 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 611 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 612 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 613 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 614 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 615 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 616 "\r\000/"; /* 0x60 - 0x6f */ 617 618 struct sysrq_state { 619 struct input_handle handle; 620 struct work_struct reinject_work; 621 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 622 unsigned int alt; 623 unsigned int alt_use; 624 bool active; 625 bool need_reinject; 626 bool reinjecting; 627 628 /* reset sequence handling */ 629 bool reset_canceled; 630 bool reset_requested; 631 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 632 int reset_seq_len; 633 int reset_seq_cnt; 634 int reset_seq_version; 635 struct timer_list keyreset_timer; 636 }; 637 638 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 639 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 640 static unsigned int sysrq_reset_seq_len; 641 static unsigned int sysrq_reset_seq_version = 1; 642 643 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 644 { 645 int i; 646 unsigned short key; 647 648 state->reset_seq_cnt = 0; 649 650 for (i = 0; i < sysrq_reset_seq_len; i++) { 651 key = sysrq_reset_seq[i]; 652 653 if (key == KEY_RESERVED || key > KEY_MAX) 654 break; 655 656 __set_bit(key, state->reset_keybit); 657 state->reset_seq_len++; 658 659 if (test_bit(key, state->key_down)) 660 state->reset_seq_cnt++; 661 } 662 663 /* Disable reset until old keys are not released */ 664 state->reset_canceled = state->reset_seq_cnt != 0; 665 666 state->reset_seq_version = sysrq_reset_seq_version; 667 } 668 669 static void sysrq_do_reset(struct timer_list *t) 670 { 671 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 672 673 state->reset_requested = true; 674 675 orderly_reboot(); 676 } 677 678 static void sysrq_handle_reset_request(struct sysrq_state *state) 679 { 680 if (state->reset_requested) 681 __handle_sysrq(sysrq_xlate[KEY_B], false); 682 683 if (sysrq_reset_downtime_ms) 684 mod_timer(&state->keyreset_timer, 685 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 686 else 687 sysrq_do_reset(&state->keyreset_timer); 688 } 689 690 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 691 unsigned int code, int value) 692 { 693 if (!test_bit(code, state->reset_keybit)) { 694 /* 695 * Pressing any key _not_ in reset sequence cancels 696 * the reset sequence. Also cancelling the timer in 697 * case additional keys were pressed after a reset 698 * has been requested. 699 */ 700 if (value && state->reset_seq_cnt) { 701 state->reset_canceled = true; 702 del_timer(&state->keyreset_timer); 703 } 704 } else if (value == 0) { 705 /* 706 * Key release - all keys in the reset sequence need 707 * to be pressed and held for the reset timeout 708 * to hold. 709 */ 710 del_timer(&state->keyreset_timer); 711 712 if (--state->reset_seq_cnt == 0) 713 state->reset_canceled = false; 714 } else if (value == 1) { 715 /* key press, not autorepeat */ 716 if (++state->reset_seq_cnt == state->reset_seq_len && 717 !state->reset_canceled) { 718 sysrq_handle_reset_request(state); 719 } 720 } 721 } 722 723 #ifdef CONFIG_OF 724 static void sysrq_of_get_keyreset_config(void) 725 { 726 u32 key; 727 struct device_node *np; 728 struct property *prop; 729 const __be32 *p; 730 731 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 732 if (!np) { 733 pr_debug("No sysrq node found"); 734 return; 735 } 736 737 /* Reset in case a __weak definition was present */ 738 sysrq_reset_seq_len = 0; 739 740 of_property_for_each_u32(np, "keyset", prop, p, key) { 741 if (key == KEY_RESERVED || key > KEY_MAX || 742 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 743 break; 744 745 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 746 } 747 748 /* Get reset timeout if any. */ 749 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 750 751 of_node_put(np); 752 } 753 #else 754 static void sysrq_of_get_keyreset_config(void) 755 { 756 } 757 #endif 758 759 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 760 { 761 struct sysrq_state *sysrq = 762 container_of(work, struct sysrq_state, reinject_work); 763 struct input_handle *handle = &sysrq->handle; 764 unsigned int alt_code = sysrq->alt_use; 765 766 if (sysrq->need_reinject) { 767 /* we do not want the assignment to be reordered */ 768 sysrq->reinjecting = true; 769 mb(); 770 771 /* Simulate press and release of Alt + SysRq */ 772 input_inject_event(handle, EV_KEY, alt_code, 1); 773 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 774 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 775 776 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 777 input_inject_event(handle, EV_KEY, alt_code, 0); 778 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 779 780 mb(); 781 sysrq->reinjecting = false; 782 } 783 } 784 785 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 786 unsigned int code, int value) 787 { 788 bool was_active = sysrq->active; 789 bool suppress; 790 791 switch (code) { 792 793 case KEY_LEFTALT: 794 case KEY_RIGHTALT: 795 if (!value) { 796 /* One of ALTs is being released */ 797 if (sysrq->active && code == sysrq->alt_use) 798 sysrq->active = false; 799 800 sysrq->alt = KEY_RESERVED; 801 802 } else if (value != 2) { 803 sysrq->alt = code; 804 sysrq->need_reinject = false; 805 } 806 break; 807 808 case KEY_SYSRQ: 809 if (value == 1 && sysrq->alt != KEY_RESERVED) { 810 sysrq->active = true; 811 sysrq->alt_use = sysrq->alt; 812 /* 813 * If nothing else will be pressed we'll need 814 * to re-inject Alt-SysRq keysroke. 815 */ 816 sysrq->need_reinject = true; 817 } 818 819 /* 820 * Pretend that sysrq was never pressed at all. This 821 * is needed to properly handle KGDB which will try 822 * to release all keys after exiting debugger. If we 823 * do not clear key bit it KGDB will end up sending 824 * release events for Alt and SysRq, potentially 825 * triggering print screen function. 826 */ 827 if (sysrq->active) 828 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 829 830 break; 831 832 default: 833 if (sysrq->active && value && value != 2) { 834 sysrq->need_reinject = false; 835 __handle_sysrq(sysrq_xlate[code], true); 836 } 837 break; 838 } 839 840 suppress = sysrq->active; 841 842 if (!sysrq->active) { 843 844 /* 845 * See if reset sequence has changed since the last time. 846 */ 847 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 848 sysrq_parse_reset_sequence(sysrq); 849 850 /* 851 * If we are not suppressing key presses keep track of 852 * keyboard state so we can release keys that have been 853 * pressed before entering SysRq mode. 854 */ 855 if (value) 856 set_bit(code, sysrq->key_down); 857 else 858 clear_bit(code, sysrq->key_down); 859 860 if (was_active) 861 schedule_work(&sysrq->reinject_work); 862 863 /* Check for reset sequence */ 864 sysrq_detect_reset_sequence(sysrq, code, value); 865 866 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 867 /* 868 * Pass on release events for keys that was pressed before 869 * entering SysRq mode. 870 */ 871 suppress = false; 872 } 873 874 return suppress; 875 } 876 877 static bool sysrq_filter(struct input_handle *handle, 878 unsigned int type, unsigned int code, int value) 879 { 880 struct sysrq_state *sysrq = handle->private; 881 bool suppress; 882 883 /* 884 * Do not filter anything if we are in the process of re-injecting 885 * Alt+SysRq combination. 886 */ 887 if (sysrq->reinjecting) 888 return false; 889 890 switch (type) { 891 892 case EV_SYN: 893 suppress = false; 894 break; 895 896 case EV_KEY: 897 suppress = sysrq_handle_keypress(sysrq, code, value); 898 break; 899 900 default: 901 suppress = sysrq->active; 902 break; 903 } 904 905 return suppress; 906 } 907 908 static int sysrq_connect(struct input_handler *handler, 909 struct input_dev *dev, 910 const struct input_device_id *id) 911 { 912 struct sysrq_state *sysrq; 913 int error; 914 915 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 916 if (!sysrq) 917 return -ENOMEM; 918 919 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 920 921 sysrq->handle.dev = dev; 922 sysrq->handle.handler = handler; 923 sysrq->handle.name = "sysrq"; 924 sysrq->handle.private = sysrq; 925 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 926 927 error = input_register_handle(&sysrq->handle); 928 if (error) { 929 pr_err("Failed to register input sysrq handler, error %d\n", 930 error); 931 goto err_free; 932 } 933 934 error = input_open_device(&sysrq->handle); 935 if (error) { 936 pr_err("Failed to open input device, error %d\n", error); 937 goto err_unregister; 938 } 939 940 return 0; 941 942 err_unregister: 943 input_unregister_handle(&sysrq->handle); 944 err_free: 945 kfree(sysrq); 946 return error; 947 } 948 949 static void sysrq_disconnect(struct input_handle *handle) 950 { 951 struct sysrq_state *sysrq = handle->private; 952 953 input_close_device(handle); 954 cancel_work_sync(&sysrq->reinject_work); 955 del_timer_sync(&sysrq->keyreset_timer); 956 input_unregister_handle(handle); 957 kfree(sysrq); 958 } 959 960 /* 961 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 962 * keyboards have SysRq key predefined and so user may add it to keymap 963 * later, but we expect all such keyboards to have left alt. 964 */ 965 static const struct input_device_id sysrq_ids[] = { 966 { 967 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 968 INPUT_DEVICE_ID_MATCH_KEYBIT, 969 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 970 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 971 }, 972 { }, 973 }; 974 975 static struct input_handler sysrq_handler = { 976 .filter = sysrq_filter, 977 .connect = sysrq_connect, 978 .disconnect = sysrq_disconnect, 979 .name = "sysrq", 980 .id_table = sysrq_ids, 981 }; 982 983 static inline void sysrq_register_handler(void) 984 { 985 int error; 986 987 sysrq_of_get_keyreset_config(); 988 989 error = input_register_handler(&sysrq_handler); 990 if (error) 991 pr_err("Failed to register input handler, error %d", error); 992 } 993 994 static inline void sysrq_unregister_handler(void) 995 { 996 input_unregister_handler(&sysrq_handler); 997 } 998 999 static int sysrq_reset_seq_param_set(const char *buffer, 1000 const struct kernel_param *kp) 1001 { 1002 unsigned long val; 1003 int error; 1004 1005 error = kstrtoul(buffer, 0, &val); 1006 if (error < 0) 1007 return error; 1008 1009 if (val > KEY_MAX) 1010 return -EINVAL; 1011 1012 *((unsigned short *)kp->arg) = val; 1013 sysrq_reset_seq_version++; 1014 1015 return 0; 1016 } 1017 1018 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1019 .get = param_get_ushort, 1020 .set = sysrq_reset_seq_param_set, 1021 }; 1022 1023 #define param_check_sysrq_reset_seq(name, p) \ 1024 __param_check(name, p, unsigned short) 1025 1026 /* 1027 * not really modular, but the easiest way to keep compat with existing 1028 * bootargs behaviour is to continue using module_param here. 1029 */ 1030 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1031 &sysrq_reset_seq_len, 0644); 1032 1033 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1034 1035 #else 1036 1037 static inline void sysrq_register_handler(void) 1038 { 1039 } 1040 1041 static inline void sysrq_unregister_handler(void) 1042 { 1043 } 1044 1045 #endif /* CONFIG_INPUT */ 1046 1047 int sysrq_toggle_support(int enable_mask) 1048 { 1049 bool was_enabled = sysrq_on(); 1050 1051 sysrq_enabled = enable_mask; 1052 1053 if (was_enabled != sysrq_on()) { 1054 if (sysrq_on()) 1055 sysrq_register_handler(); 1056 else 1057 sysrq_unregister_handler(); 1058 } 1059 1060 return 0; 1061 } 1062 EXPORT_SYMBOL_GPL(sysrq_toggle_support); 1063 1064 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1065 struct sysrq_key_op *remove_op_p) 1066 { 1067 int retval; 1068 1069 spin_lock(&sysrq_key_table_lock); 1070 if (__sysrq_get_key_op(key) == remove_op_p) { 1071 __sysrq_put_key_op(key, insert_op_p); 1072 retval = 0; 1073 } else { 1074 retval = -1; 1075 } 1076 spin_unlock(&sysrq_key_table_lock); 1077 1078 /* 1079 * A concurrent __handle_sysrq either got the old op or the new op. 1080 * Wait for it to go away before returning, so the code for an old 1081 * op is not freed (eg. on module unload) while it is in use. 1082 */ 1083 synchronize_rcu(); 1084 1085 return retval; 1086 } 1087 1088 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1089 { 1090 return __sysrq_swap_key_ops(key, op_p, NULL); 1091 } 1092 EXPORT_SYMBOL(register_sysrq_key); 1093 1094 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1095 { 1096 return __sysrq_swap_key_ops(key, NULL, op_p); 1097 } 1098 EXPORT_SYMBOL(unregister_sysrq_key); 1099 1100 #ifdef CONFIG_PROC_FS 1101 /* 1102 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1103 */ 1104 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1105 size_t count, loff_t *ppos) 1106 { 1107 if (count) { 1108 char c; 1109 1110 if (get_user(c, buf)) 1111 return -EFAULT; 1112 __handle_sysrq(c, false); 1113 } 1114 1115 return count; 1116 } 1117 1118 static const struct proc_ops sysrq_trigger_proc_ops = { 1119 .proc_write = write_sysrq_trigger, 1120 .proc_lseek = noop_llseek, 1121 }; 1122 1123 static void sysrq_init_procfs(void) 1124 { 1125 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1126 &sysrq_trigger_proc_ops)) 1127 pr_err("Failed to register proc interface\n"); 1128 } 1129 1130 #else 1131 1132 static inline void sysrq_init_procfs(void) 1133 { 1134 } 1135 1136 #endif /* CONFIG_PROC_FS */ 1137 1138 static int __init sysrq_init(void) 1139 { 1140 sysrq_init_procfs(); 1141 1142 if (sysrq_on()) 1143 sysrq_register_handler(); 1144 1145 return 0; 1146 } 1147 device_initcall(sysrq_init); 1148