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 * A value of 1 means 'all', other nonzero values are an op mask: 68 */ 69 static bool sysrq_on_mask(int mask) 70 { 71 return sysrq_always_enabled || 72 sysrq_enabled == 1 || 73 (sysrq_enabled & mask); 74 } 75 76 static int __init sysrq_always_enabled_setup(char *str) 77 { 78 sysrq_always_enabled = true; 79 pr_info("sysrq always enabled.\n"); 80 81 return 1; 82 } 83 84 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 85 86 87 static void sysrq_handle_loglevel(int key) 88 { 89 int i; 90 91 i = key - '0'; 92 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 93 pr_info("Loglevel set to %d\n", i); 94 console_loglevel = i; 95 } 96 static struct sysrq_key_op sysrq_loglevel_op = { 97 .handler = sysrq_handle_loglevel, 98 .help_msg = "loglevel(0-9)", 99 .action_msg = "Changing Loglevel", 100 .enable_mask = SYSRQ_ENABLE_LOG, 101 }; 102 103 #ifdef CONFIG_VT 104 static void sysrq_handle_SAK(int key) 105 { 106 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 107 schedule_work(SAK_work); 108 } 109 static struct sysrq_key_op sysrq_SAK_op = { 110 .handler = sysrq_handle_SAK, 111 .help_msg = "sak(k)", 112 .action_msg = "SAK", 113 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 114 }; 115 #else 116 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL) 117 #endif 118 119 #ifdef CONFIG_VT 120 static void sysrq_handle_unraw(int key) 121 { 122 vt_reset_unicode(fg_console); 123 } 124 125 static struct sysrq_key_op sysrq_unraw_op = { 126 .handler = sysrq_handle_unraw, 127 .help_msg = "unraw(r)", 128 .action_msg = "Keyboard mode set to system default", 129 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 130 }; 131 #else 132 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL) 133 #endif /* CONFIG_VT */ 134 135 static void sysrq_handle_crash(int key) 136 { 137 /* release the RCU read lock before crashing */ 138 rcu_read_unlock(); 139 140 panic("sysrq triggered crash\n"); 141 } 142 static struct sysrq_key_op sysrq_crash_op = { 143 .handler = sysrq_handle_crash, 144 .help_msg = "crash(c)", 145 .action_msg = "Trigger a crash", 146 .enable_mask = SYSRQ_ENABLE_DUMP, 147 }; 148 149 static void sysrq_handle_reboot(int key) 150 { 151 lockdep_off(); 152 local_irq_enable(); 153 emergency_restart(); 154 } 155 static struct sysrq_key_op sysrq_reboot_op = { 156 .handler = sysrq_handle_reboot, 157 .help_msg = "reboot(b)", 158 .action_msg = "Resetting", 159 .enable_mask = SYSRQ_ENABLE_BOOT, 160 }; 161 162 static void sysrq_handle_sync(int key) 163 { 164 emergency_sync(); 165 } 166 static struct sysrq_key_op sysrq_sync_op = { 167 .handler = sysrq_handle_sync, 168 .help_msg = "sync(s)", 169 .action_msg = "Emergency Sync", 170 .enable_mask = SYSRQ_ENABLE_SYNC, 171 }; 172 173 static void sysrq_handle_show_timers(int key) 174 { 175 sysrq_timer_list_show(); 176 } 177 178 static struct sysrq_key_op sysrq_show_timers_op = { 179 .handler = sysrq_handle_show_timers, 180 .help_msg = "show-all-timers(q)", 181 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 182 }; 183 184 static void sysrq_handle_mountro(int key) 185 { 186 emergency_remount(); 187 } 188 static struct sysrq_key_op sysrq_mountro_op = { 189 .handler = sysrq_handle_mountro, 190 .help_msg = "unmount(u)", 191 .action_msg = "Emergency Remount R/O", 192 .enable_mask = SYSRQ_ENABLE_REMOUNT, 193 }; 194 195 #ifdef CONFIG_LOCKDEP 196 static void sysrq_handle_showlocks(int key) 197 { 198 debug_show_all_locks(); 199 } 200 201 static struct sysrq_key_op sysrq_showlocks_op = { 202 .handler = sysrq_handle_showlocks, 203 .help_msg = "show-all-locks(d)", 204 .action_msg = "Show Locks Held", 205 }; 206 #else 207 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 208 #endif 209 210 #ifdef CONFIG_SMP 211 static DEFINE_SPINLOCK(show_lock); 212 213 static void showacpu(void *dummy) 214 { 215 unsigned long flags; 216 217 /* Idle CPUs have no interesting backtrace. */ 218 if (idle_cpu(smp_processor_id())) 219 return; 220 221 spin_lock_irqsave(&show_lock, flags); 222 pr_info("CPU%d:\n", smp_processor_id()); 223 show_stack(NULL, NULL); 224 spin_unlock_irqrestore(&show_lock, flags); 225 } 226 227 static void sysrq_showregs_othercpus(struct work_struct *dummy) 228 { 229 smp_call_function(showacpu, NULL, 0); 230 } 231 232 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 233 234 static void sysrq_handle_showallcpus(int key) 235 { 236 /* 237 * Fall back to the workqueue based printing if the 238 * backtrace printing did not succeed or the 239 * architecture has no support for it: 240 */ 241 if (!trigger_all_cpu_backtrace()) { 242 struct pt_regs *regs = NULL; 243 244 if (in_irq()) 245 regs = get_irq_regs(); 246 if (regs) { 247 pr_info("CPU%d:\n", smp_processor_id()); 248 show_regs(regs); 249 } 250 schedule_work(&sysrq_showallcpus); 251 } 252 } 253 254 static struct sysrq_key_op sysrq_showallcpus_op = { 255 .handler = sysrq_handle_showallcpus, 256 .help_msg = "show-backtrace-all-active-cpus(l)", 257 .action_msg = "Show backtrace of all active CPUs", 258 .enable_mask = SYSRQ_ENABLE_DUMP, 259 }; 260 #endif 261 262 static void sysrq_handle_showregs(int key) 263 { 264 struct pt_regs *regs = NULL; 265 266 if (in_irq()) 267 regs = get_irq_regs(); 268 if (regs) 269 show_regs(regs); 270 perf_event_print_debug(); 271 } 272 static struct sysrq_key_op sysrq_showregs_op = { 273 .handler = sysrq_handle_showregs, 274 .help_msg = "show-registers(p)", 275 .action_msg = "Show Regs", 276 .enable_mask = SYSRQ_ENABLE_DUMP, 277 }; 278 279 static void sysrq_handle_showstate(int key) 280 { 281 show_state(); 282 show_workqueue_state(); 283 } 284 static struct sysrq_key_op sysrq_showstate_op = { 285 .handler = sysrq_handle_showstate, 286 .help_msg = "show-task-states(t)", 287 .action_msg = "Show State", 288 .enable_mask = SYSRQ_ENABLE_DUMP, 289 }; 290 291 static void sysrq_handle_showstate_blocked(int key) 292 { 293 show_state_filter(TASK_UNINTERRUPTIBLE); 294 } 295 static struct sysrq_key_op sysrq_showstate_blocked_op = { 296 .handler = sysrq_handle_showstate_blocked, 297 .help_msg = "show-blocked-tasks(w)", 298 .action_msg = "Show Blocked State", 299 .enable_mask = SYSRQ_ENABLE_DUMP, 300 }; 301 302 #ifdef CONFIG_TRACING 303 #include <linux/ftrace.h> 304 305 static void sysrq_ftrace_dump(int key) 306 { 307 ftrace_dump(DUMP_ALL); 308 } 309 static struct sysrq_key_op sysrq_ftrace_dump_op = { 310 .handler = sysrq_ftrace_dump, 311 .help_msg = "dump-ftrace-buffer(z)", 312 .action_msg = "Dump ftrace buffer", 313 .enable_mask = SYSRQ_ENABLE_DUMP, 314 }; 315 #else 316 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 317 #endif 318 319 static void sysrq_handle_showmem(int key) 320 { 321 show_mem(0, NULL); 322 } 323 static struct sysrq_key_op sysrq_showmem_op = { 324 .handler = sysrq_handle_showmem, 325 .help_msg = "show-memory-usage(m)", 326 .action_msg = "Show Memory", 327 .enable_mask = SYSRQ_ENABLE_DUMP, 328 }; 329 330 /* 331 * Signal sysrq helper function. Sends a signal to all user processes. 332 */ 333 static void send_sig_all(int sig) 334 { 335 struct task_struct *p; 336 337 read_lock(&tasklist_lock); 338 for_each_process(p) { 339 if (p->flags & PF_KTHREAD) 340 continue; 341 if (is_global_init(p)) 342 continue; 343 344 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX); 345 } 346 read_unlock(&tasklist_lock); 347 } 348 349 static void sysrq_handle_term(int key) 350 { 351 send_sig_all(SIGTERM); 352 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 353 } 354 static struct sysrq_key_op sysrq_term_op = { 355 .handler = sysrq_handle_term, 356 .help_msg = "terminate-all-tasks(e)", 357 .action_msg = "Terminate All Tasks", 358 .enable_mask = SYSRQ_ENABLE_SIGNAL, 359 }; 360 361 static void moom_callback(struct work_struct *ignored) 362 { 363 const gfp_t gfp_mask = GFP_KERNEL; 364 struct oom_control oc = { 365 .zonelist = node_zonelist(first_memory_node, gfp_mask), 366 .nodemask = NULL, 367 .memcg = NULL, 368 .gfp_mask = gfp_mask, 369 .order = -1, 370 }; 371 372 mutex_lock(&oom_lock); 373 if (!out_of_memory(&oc)) 374 pr_info("OOM request ignored. No task eligible\n"); 375 mutex_unlock(&oom_lock); 376 } 377 378 static DECLARE_WORK(moom_work, moom_callback); 379 380 static void sysrq_handle_moom(int key) 381 { 382 schedule_work(&moom_work); 383 } 384 static struct sysrq_key_op sysrq_moom_op = { 385 .handler = sysrq_handle_moom, 386 .help_msg = "memory-full-oom-kill(f)", 387 .action_msg = "Manual OOM execution", 388 .enable_mask = SYSRQ_ENABLE_SIGNAL, 389 }; 390 391 #ifdef CONFIG_BLOCK 392 static void sysrq_handle_thaw(int key) 393 { 394 emergency_thaw_all(); 395 } 396 static struct sysrq_key_op sysrq_thaw_op = { 397 .handler = sysrq_handle_thaw, 398 .help_msg = "thaw-filesystems(j)", 399 .action_msg = "Emergency Thaw of all frozen filesystems", 400 .enable_mask = SYSRQ_ENABLE_SIGNAL, 401 }; 402 #endif 403 404 static void sysrq_handle_kill(int key) 405 { 406 send_sig_all(SIGKILL); 407 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 408 } 409 static struct sysrq_key_op sysrq_kill_op = { 410 .handler = sysrq_handle_kill, 411 .help_msg = "kill-all-tasks(i)", 412 .action_msg = "Kill All Tasks", 413 .enable_mask = SYSRQ_ENABLE_SIGNAL, 414 }; 415 416 static void sysrq_handle_unrt(int key) 417 { 418 normalize_rt_tasks(); 419 } 420 static struct sysrq_key_op sysrq_unrt_op = { 421 .handler = sysrq_handle_unrt, 422 .help_msg = "nice-all-RT-tasks(n)", 423 .action_msg = "Nice All RT Tasks", 424 .enable_mask = SYSRQ_ENABLE_RTNICE, 425 }; 426 427 /* Key Operations table and lock */ 428 static DEFINE_SPINLOCK(sysrq_key_table_lock); 429 430 static struct sysrq_key_op *sysrq_key_table[36] = { 431 &sysrq_loglevel_op, /* 0 */ 432 &sysrq_loglevel_op, /* 1 */ 433 &sysrq_loglevel_op, /* 2 */ 434 &sysrq_loglevel_op, /* 3 */ 435 &sysrq_loglevel_op, /* 4 */ 436 &sysrq_loglevel_op, /* 5 */ 437 &sysrq_loglevel_op, /* 6 */ 438 &sysrq_loglevel_op, /* 7 */ 439 &sysrq_loglevel_op, /* 8 */ 440 &sysrq_loglevel_op, /* 9 */ 441 442 /* 443 * a: Don't use for system provided sysrqs, it is handled specially on 444 * sparc and will never arrive. 445 */ 446 NULL, /* a */ 447 &sysrq_reboot_op, /* b */ 448 &sysrq_crash_op, /* c */ 449 &sysrq_showlocks_op, /* d */ 450 &sysrq_term_op, /* e */ 451 &sysrq_moom_op, /* f */ 452 /* g: May be registered for the kernel debugger */ 453 NULL, /* g */ 454 NULL, /* h - reserved for help */ 455 &sysrq_kill_op, /* i */ 456 #ifdef CONFIG_BLOCK 457 &sysrq_thaw_op, /* j */ 458 #else 459 NULL, /* j */ 460 #endif 461 &sysrq_SAK_op, /* k */ 462 #ifdef CONFIG_SMP 463 &sysrq_showallcpus_op, /* l */ 464 #else 465 NULL, /* l */ 466 #endif 467 &sysrq_showmem_op, /* m */ 468 &sysrq_unrt_op, /* n */ 469 /* o: This will often be registered as 'Off' at init time */ 470 NULL, /* o */ 471 &sysrq_showregs_op, /* p */ 472 &sysrq_show_timers_op, /* q */ 473 &sysrq_unraw_op, /* r */ 474 &sysrq_sync_op, /* s */ 475 &sysrq_showstate_op, /* t */ 476 &sysrq_mountro_op, /* u */ 477 /* v: May be registered for frame buffer console restore */ 478 NULL, /* v */ 479 &sysrq_showstate_blocked_op, /* w */ 480 /* x: May be registered on mips for TLB dump */ 481 /* x: May be registered on ppc/powerpc for xmon */ 482 /* x: May be registered on sparc64 for global PMU dump */ 483 NULL, /* x */ 484 /* y: May be registered on sparc64 for global register dump */ 485 NULL, /* y */ 486 &sysrq_ftrace_dump_op, /* z */ 487 }; 488 489 /* key2index calculation, -1 on invalid index */ 490 static int sysrq_key_table_key2index(int key) 491 { 492 int retval; 493 494 if ((key >= '0') && (key <= '9')) 495 retval = key - '0'; 496 else if ((key >= 'a') && (key <= 'z')) 497 retval = key + 10 - 'a'; 498 else 499 retval = -1; 500 return retval; 501 } 502 503 /* 504 * get and put functions for the table, exposed to modules. 505 */ 506 struct sysrq_key_op *__sysrq_get_key_op(int key) 507 { 508 struct sysrq_key_op *op_p = NULL; 509 int i; 510 511 i = sysrq_key_table_key2index(key); 512 if (i != -1) 513 op_p = sysrq_key_table[i]; 514 515 return op_p; 516 } 517 518 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 519 { 520 int i = sysrq_key_table_key2index(key); 521 522 if (i != -1) 523 sysrq_key_table[i] = op_p; 524 } 525 526 void __handle_sysrq(int key, bool check_mask) 527 { 528 struct sysrq_key_op *op_p; 529 int orig_log_level; 530 int i; 531 532 rcu_sysrq_start(); 533 rcu_read_lock(); 534 /* 535 * Raise the apparent loglevel to maximum so that the sysrq header 536 * is shown to provide the user with positive feedback. We do not 537 * simply emit this at KERN_EMERG as that would change message 538 * routing in the consumers of /proc/kmsg. 539 */ 540 orig_log_level = console_loglevel; 541 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 542 pr_info("SysRq : "); 543 544 op_p = __sysrq_get_key_op(key); 545 if (op_p) { 546 /* 547 * Should we check for enabled operations (/proc/sysrq-trigger 548 * should not) and is the invoked operation enabled? 549 */ 550 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 551 pr_cont("%s\n", op_p->action_msg); 552 console_loglevel = orig_log_level; 553 op_p->handler(key); 554 } else { 555 pr_cont("This sysrq operation is disabled.\n"); 556 } 557 } else { 558 pr_cont("HELP : "); 559 /* Only print the help msg once per handler */ 560 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 561 if (sysrq_key_table[i]) { 562 int j; 563 564 for (j = 0; sysrq_key_table[i] != 565 sysrq_key_table[j]; j++) 566 ; 567 if (j != i) 568 continue; 569 pr_cont("%s ", sysrq_key_table[i]->help_msg); 570 } 571 } 572 pr_cont("\n"); 573 console_loglevel = orig_log_level; 574 } 575 rcu_read_unlock(); 576 rcu_sysrq_end(); 577 } 578 579 void handle_sysrq(int key) 580 { 581 if (sysrq_on()) 582 __handle_sysrq(key, true); 583 } 584 EXPORT_SYMBOL(handle_sysrq); 585 586 #ifdef CONFIG_INPUT 587 static int sysrq_reset_downtime_ms; 588 589 /* Simple translation table for the SysRq keys */ 590 static const unsigned char sysrq_xlate[KEY_CNT] = 591 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 592 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 593 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 594 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 595 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 596 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 597 "\r\000/"; /* 0x60 - 0x6f */ 598 599 struct sysrq_state { 600 struct input_handle handle; 601 struct work_struct reinject_work; 602 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 603 unsigned int alt; 604 unsigned int alt_use; 605 bool active; 606 bool need_reinject; 607 bool reinjecting; 608 609 /* reset sequence handling */ 610 bool reset_canceled; 611 bool reset_requested; 612 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 613 int reset_seq_len; 614 int reset_seq_cnt; 615 int reset_seq_version; 616 struct timer_list keyreset_timer; 617 }; 618 619 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 620 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 621 static unsigned int sysrq_reset_seq_len; 622 static unsigned int sysrq_reset_seq_version = 1; 623 624 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 625 { 626 int i; 627 unsigned short key; 628 629 state->reset_seq_cnt = 0; 630 631 for (i = 0; i < sysrq_reset_seq_len; i++) { 632 key = sysrq_reset_seq[i]; 633 634 if (key == KEY_RESERVED || key > KEY_MAX) 635 break; 636 637 __set_bit(key, state->reset_keybit); 638 state->reset_seq_len++; 639 640 if (test_bit(key, state->key_down)) 641 state->reset_seq_cnt++; 642 } 643 644 /* Disable reset until old keys are not released */ 645 state->reset_canceled = state->reset_seq_cnt != 0; 646 647 state->reset_seq_version = sysrq_reset_seq_version; 648 } 649 650 static void sysrq_do_reset(struct timer_list *t) 651 { 652 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 653 654 state->reset_requested = true; 655 656 orderly_reboot(); 657 } 658 659 static void sysrq_handle_reset_request(struct sysrq_state *state) 660 { 661 if (state->reset_requested) 662 __handle_sysrq(sysrq_xlate[KEY_B], false); 663 664 if (sysrq_reset_downtime_ms) 665 mod_timer(&state->keyreset_timer, 666 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 667 else 668 sysrq_do_reset(&state->keyreset_timer); 669 } 670 671 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 672 unsigned int code, int value) 673 { 674 if (!test_bit(code, state->reset_keybit)) { 675 /* 676 * Pressing any key _not_ in reset sequence cancels 677 * the reset sequence. Also cancelling the timer in 678 * case additional keys were pressed after a reset 679 * has been requested. 680 */ 681 if (value && state->reset_seq_cnt) { 682 state->reset_canceled = true; 683 del_timer(&state->keyreset_timer); 684 } 685 } else if (value == 0) { 686 /* 687 * Key release - all keys in the reset sequence need 688 * to be pressed and held for the reset timeout 689 * to hold. 690 */ 691 del_timer(&state->keyreset_timer); 692 693 if (--state->reset_seq_cnt == 0) 694 state->reset_canceled = false; 695 } else if (value == 1) { 696 /* key press, not autorepeat */ 697 if (++state->reset_seq_cnt == state->reset_seq_len && 698 !state->reset_canceled) { 699 sysrq_handle_reset_request(state); 700 } 701 } 702 } 703 704 #ifdef CONFIG_OF 705 static void sysrq_of_get_keyreset_config(void) 706 { 707 u32 key; 708 struct device_node *np; 709 struct property *prop; 710 const __be32 *p; 711 712 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 713 if (!np) { 714 pr_debug("No sysrq node found"); 715 return; 716 } 717 718 /* Reset in case a __weak definition was present */ 719 sysrq_reset_seq_len = 0; 720 721 of_property_for_each_u32(np, "keyset", prop, p, key) { 722 if (key == KEY_RESERVED || key > KEY_MAX || 723 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 724 break; 725 726 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 727 } 728 729 /* Get reset timeout if any. */ 730 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 731 732 of_node_put(np); 733 } 734 #else 735 static void sysrq_of_get_keyreset_config(void) 736 { 737 } 738 #endif 739 740 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 741 { 742 struct sysrq_state *sysrq = 743 container_of(work, struct sysrq_state, reinject_work); 744 struct input_handle *handle = &sysrq->handle; 745 unsigned int alt_code = sysrq->alt_use; 746 747 if (sysrq->need_reinject) { 748 /* we do not want the assignment to be reordered */ 749 sysrq->reinjecting = true; 750 mb(); 751 752 /* Simulate press and release of Alt + SysRq */ 753 input_inject_event(handle, EV_KEY, alt_code, 1); 754 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 755 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 756 757 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 758 input_inject_event(handle, EV_KEY, alt_code, 0); 759 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 760 761 mb(); 762 sysrq->reinjecting = false; 763 } 764 } 765 766 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 767 unsigned int code, int value) 768 { 769 bool was_active = sysrq->active; 770 bool suppress; 771 772 switch (code) { 773 774 case KEY_LEFTALT: 775 case KEY_RIGHTALT: 776 if (!value) { 777 /* One of ALTs is being released */ 778 if (sysrq->active && code == sysrq->alt_use) 779 sysrq->active = false; 780 781 sysrq->alt = KEY_RESERVED; 782 783 } else if (value != 2) { 784 sysrq->alt = code; 785 sysrq->need_reinject = false; 786 } 787 break; 788 789 case KEY_SYSRQ: 790 if (value == 1 && sysrq->alt != KEY_RESERVED) { 791 sysrq->active = true; 792 sysrq->alt_use = sysrq->alt; 793 /* 794 * If nothing else will be pressed we'll need 795 * to re-inject Alt-SysRq keysroke. 796 */ 797 sysrq->need_reinject = true; 798 } 799 800 /* 801 * Pretend that sysrq was never pressed at all. This 802 * is needed to properly handle KGDB which will try 803 * to release all keys after exiting debugger. If we 804 * do not clear key bit it KGDB will end up sending 805 * release events for Alt and SysRq, potentially 806 * triggering print screen function. 807 */ 808 if (sysrq->active) 809 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 810 811 break; 812 813 default: 814 if (sysrq->active && value && value != 2) { 815 sysrq->need_reinject = false; 816 __handle_sysrq(sysrq_xlate[code], true); 817 } 818 break; 819 } 820 821 suppress = sysrq->active; 822 823 if (!sysrq->active) { 824 825 /* 826 * See if reset sequence has changed since the last time. 827 */ 828 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 829 sysrq_parse_reset_sequence(sysrq); 830 831 /* 832 * If we are not suppressing key presses keep track of 833 * keyboard state so we can release keys that have been 834 * pressed before entering SysRq mode. 835 */ 836 if (value) 837 set_bit(code, sysrq->key_down); 838 else 839 clear_bit(code, sysrq->key_down); 840 841 if (was_active) 842 schedule_work(&sysrq->reinject_work); 843 844 /* Check for reset sequence */ 845 sysrq_detect_reset_sequence(sysrq, code, value); 846 847 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 848 /* 849 * Pass on release events for keys that was pressed before 850 * entering SysRq mode. 851 */ 852 suppress = false; 853 } 854 855 return suppress; 856 } 857 858 static bool sysrq_filter(struct input_handle *handle, 859 unsigned int type, unsigned int code, int value) 860 { 861 struct sysrq_state *sysrq = handle->private; 862 bool suppress; 863 864 /* 865 * Do not filter anything if we are in the process of re-injecting 866 * Alt+SysRq combination. 867 */ 868 if (sysrq->reinjecting) 869 return false; 870 871 switch (type) { 872 873 case EV_SYN: 874 suppress = false; 875 break; 876 877 case EV_KEY: 878 suppress = sysrq_handle_keypress(sysrq, code, value); 879 break; 880 881 default: 882 suppress = sysrq->active; 883 break; 884 } 885 886 return suppress; 887 } 888 889 static int sysrq_connect(struct input_handler *handler, 890 struct input_dev *dev, 891 const struct input_device_id *id) 892 { 893 struct sysrq_state *sysrq; 894 int error; 895 896 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 897 if (!sysrq) 898 return -ENOMEM; 899 900 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 901 902 sysrq->handle.dev = dev; 903 sysrq->handle.handler = handler; 904 sysrq->handle.name = "sysrq"; 905 sysrq->handle.private = sysrq; 906 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 907 908 error = input_register_handle(&sysrq->handle); 909 if (error) { 910 pr_err("Failed to register input sysrq handler, error %d\n", 911 error); 912 goto err_free; 913 } 914 915 error = input_open_device(&sysrq->handle); 916 if (error) { 917 pr_err("Failed to open input device, error %d\n", error); 918 goto err_unregister; 919 } 920 921 return 0; 922 923 err_unregister: 924 input_unregister_handle(&sysrq->handle); 925 err_free: 926 kfree(sysrq); 927 return error; 928 } 929 930 static void sysrq_disconnect(struct input_handle *handle) 931 { 932 struct sysrq_state *sysrq = handle->private; 933 934 input_close_device(handle); 935 cancel_work_sync(&sysrq->reinject_work); 936 del_timer_sync(&sysrq->keyreset_timer); 937 input_unregister_handle(handle); 938 kfree(sysrq); 939 } 940 941 /* 942 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 943 * keyboards have SysRq key predefined and so user may add it to keymap 944 * later, but we expect all such keyboards to have left alt. 945 */ 946 static const struct input_device_id sysrq_ids[] = { 947 { 948 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 949 INPUT_DEVICE_ID_MATCH_KEYBIT, 950 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 951 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 952 }, 953 { }, 954 }; 955 956 static struct input_handler sysrq_handler = { 957 .filter = sysrq_filter, 958 .connect = sysrq_connect, 959 .disconnect = sysrq_disconnect, 960 .name = "sysrq", 961 .id_table = sysrq_ids, 962 }; 963 964 static bool sysrq_handler_registered; 965 966 static inline void sysrq_register_handler(void) 967 { 968 int error; 969 970 sysrq_of_get_keyreset_config(); 971 972 error = input_register_handler(&sysrq_handler); 973 if (error) 974 pr_err("Failed to register input handler, error %d", error); 975 else 976 sysrq_handler_registered = true; 977 } 978 979 static inline void sysrq_unregister_handler(void) 980 { 981 if (sysrq_handler_registered) { 982 input_unregister_handler(&sysrq_handler); 983 sysrq_handler_registered = false; 984 } 985 } 986 987 static int sysrq_reset_seq_param_set(const char *buffer, 988 const struct kernel_param *kp) 989 { 990 unsigned long val; 991 int error; 992 993 error = kstrtoul(buffer, 0, &val); 994 if (error < 0) 995 return error; 996 997 if (val > KEY_MAX) 998 return -EINVAL; 999 1000 *((unsigned short *)kp->arg) = val; 1001 sysrq_reset_seq_version++; 1002 1003 return 0; 1004 } 1005 1006 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1007 .get = param_get_ushort, 1008 .set = sysrq_reset_seq_param_set, 1009 }; 1010 1011 #define param_check_sysrq_reset_seq(name, p) \ 1012 __param_check(name, p, unsigned short) 1013 1014 /* 1015 * not really modular, but the easiest way to keep compat with existing 1016 * bootargs behaviour is to continue using module_param here. 1017 */ 1018 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1019 &sysrq_reset_seq_len, 0644); 1020 1021 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1022 1023 #else 1024 1025 static inline void sysrq_register_handler(void) 1026 { 1027 } 1028 1029 static inline void sysrq_unregister_handler(void) 1030 { 1031 } 1032 1033 #endif /* CONFIG_INPUT */ 1034 1035 int sysrq_toggle_support(int enable_mask) 1036 { 1037 bool was_enabled = sysrq_on(); 1038 1039 sysrq_enabled = enable_mask; 1040 1041 if (was_enabled != sysrq_on()) { 1042 if (sysrq_on()) 1043 sysrq_register_handler(); 1044 else 1045 sysrq_unregister_handler(); 1046 } 1047 1048 return 0; 1049 } 1050 1051 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1052 struct sysrq_key_op *remove_op_p) 1053 { 1054 int retval; 1055 1056 spin_lock(&sysrq_key_table_lock); 1057 if (__sysrq_get_key_op(key) == remove_op_p) { 1058 __sysrq_put_key_op(key, insert_op_p); 1059 retval = 0; 1060 } else { 1061 retval = -1; 1062 } 1063 spin_unlock(&sysrq_key_table_lock); 1064 1065 /* 1066 * A concurrent __handle_sysrq either got the old op or the new op. 1067 * Wait for it to go away before returning, so the code for an old 1068 * op is not freed (eg. on module unload) while it is in use. 1069 */ 1070 synchronize_rcu(); 1071 1072 return retval; 1073 } 1074 1075 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1076 { 1077 return __sysrq_swap_key_ops(key, op_p, NULL); 1078 } 1079 EXPORT_SYMBOL(register_sysrq_key); 1080 1081 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1082 { 1083 return __sysrq_swap_key_ops(key, NULL, op_p); 1084 } 1085 EXPORT_SYMBOL(unregister_sysrq_key); 1086 1087 #ifdef CONFIG_PROC_FS 1088 /* 1089 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1090 */ 1091 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1092 size_t count, loff_t *ppos) 1093 { 1094 if (count) { 1095 char c; 1096 1097 if (get_user(c, buf)) 1098 return -EFAULT; 1099 __handle_sysrq(c, false); 1100 } 1101 1102 return count; 1103 } 1104 1105 static const struct file_operations proc_sysrq_trigger_operations = { 1106 .write = write_sysrq_trigger, 1107 .llseek = noop_llseek, 1108 }; 1109 1110 static void sysrq_init_procfs(void) 1111 { 1112 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1113 &proc_sysrq_trigger_operations)) 1114 pr_err("Failed to register proc interface\n"); 1115 } 1116 1117 #else 1118 1119 static inline void sysrq_init_procfs(void) 1120 { 1121 } 1122 1123 #endif /* CONFIG_PROC_FS */ 1124 1125 static int __init sysrq_init(void) 1126 { 1127 sysrq_init_procfs(); 1128 1129 if (sysrq_on()) 1130 sysrq_register_handler(); 1131 1132 return 0; 1133 } 1134 device_initcall(sysrq_init); 1135