1 /* 2 * Linux Magic System Request Key Hacks 3 * 4 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz> 5 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz> 6 * 7 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com> 8 * overhauled to use key registration 9 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies 10 * 11 * Copyright (c) 2010 Dmitry Torokhov 12 * Input handler conversion 13 */ 14 15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 16 17 #include <linux/sched.h> 18 #include <linux/sched/rt.h> 19 #include <linux/interrupt.h> 20 #include <linux/mm.h> 21 #include <linux/fs.h> 22 #include <linux/mount.h> 23 #include <linux/kdev_t.h> 24 #include <linux/major.h> 25 #include <linux/reboot.h> 26 #include <linux/sysrq.h> 27 #include <linux/kbd_kern.h> 28 #include <linux/proc_fs.h> 29 #include <linux/nmi.h> 30 #include <linux/quotaops.h> 31 #include <linux/perf_event.h> 32 #include <linux/kernel.h> 33 #include <linux/module.h> 34 #include <linux/suspend.h> 35 #include <linux/writeback.h> 36 #include <linux/swap.h> 37 #include <linux/spinlock.h> 38 #include <linux/vt_kern.h> 39 #include <linux/workqueue.h> 40 #include <linux/hrtimer.h> 41 #include <linux/oom.h> 42 #include <linux/slab.h> 43 #include <linux/input.h> 44 #include <linux/uaccess.h> 45 #include <linux/moduleparam.h> 46 #include <linux/jiffies.h> 47 #include <linux/syscalls.h> 48 #include <linux/of.h> 49 #include <linux/rcupdate.h> 50 51 #include <asm/ptrace.h> 52 #include <asm/irq_regs.h> 53 54 /* Whether we react on sysrq keys or just ignore them */ 55 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; 56 static bool __read_mostly sysrq_always_enabled; 57 58 unsigned short platform_sysrq_reset_seq[] __weak = { KEY_RESERVED }; 59 int sysrq_reset_downtime_ms __weak; 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 printk("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 char *killer = NULL; 138 139 panic_on_oops = 1; /* force panic */ 140 wmb(); 141 *killer = 1; 142 } 143 static struct sysrq_key_op sysrq_crash_op = { 144 .handler = sysrq_handle_crash, 145 .help_msg = "crash(c)", 146 .action_msg = "Trigger a crash", 147 .enable_mask = SYSRQ_ENABLE_DUMP, 148 }; 149 150 static void sysrq_handle_reboot(int key) 151 { 152 lockdep_off(); 153 local_irq_enable(); 154 emergency_restart(); 155 } 156 static struct sysrq_key_op sysrq_reboot_op = { 157 .handler = sysrq_handle_reboot, 158 .help_msg = "reboot(b)", 159 .action_msg = "Resetting", 160 .enable_mask = SYSRQ_ENABLE_BOOT, 161 }; 162 163 static void sysrq_handle_sync(int key) 164 { 165 emergency_sync(); 166 } 167 static struct sysrq_key_op sysrq_sync_op = { 168 .handler = sysrq_handle_sync, 169 .help_msg = "sync(s)", 170 .action_msg = "Emergency Sync", 171 .enable_mask = SYSRQ_ENABLE_SYNC, 172 }; 173 174 static void sysrq_handle_show_timers(int key) 175 { 176 sysrq_timer_list_show(); 177 } 178 179 static struct sysrq_key_op sysrq_show_timers_op = { 180 .handler = sysrq_handle_show_timers, 181 .help_msg = "show-all-timers(q)", 182 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 183 }; 184 185 static void sysrq_handle_mountro(int key) 186 { 187 emergency_remount(); 188 } 189 static struct sysrq_key_op sysrq_mountro_op = { 190 .handler = sysrq_handle_mountro, 191 .help_msg = "unmount(u)", 192 .action_msg = "Emergency Remount R/O", 193 .enable_mask = SYSRQ_ENABLE_REMOUNT, 194 }; 195 196 #ifdef CONFIG_LOCKDEP 197 static void sysrq_handle_showlocks(int key) 198 { 199 debug_show_all_locks(); 200 } 201 202 static struct sysrq_key_op sysrq_showlocks_op = { 203 .handler = sysrq_handle_showlocks, 204 .help_msg = "show-all-locks(d)", 205 .action_msg = "Show Locks Held", 206 }; 207 #else 208 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 209 #endif 210 211 #ifdef CONFIG_SMP 212 static DEFINE_SPINLOCK(show_lock); 213 214 static void showacpu(void *dummy) 215 { 216 unsigned long flags; 217 218 /* Idle CPUs have no interesting backtrace. */ 219 if (idle_cpu(smp_processor_id())) 220 return; 221 222 spin_lock_irqsave(&show_lock, flags); 223 printk(KERN_INFO "CPU%d:\n", smp_processor_id()); 224 show_stack(NULL, NULL); 225 spin_unlock_irqrestore(&show_lock, flags); 226 } 227 228 static void sysrq_showregs_othercpus(struct work_struct *dummy) 229 { 230 smp_call_function(showacpu, NULL, 0); 231 } 232 233 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 234 235 static void sysrq_handle_showallcpus(int key) 236 { 237 /* 238 * Fall back to the workqueue based printing if the 239 * backtrace printing did not succeed or the 240 * architecture has no support for it: 241 */ 242 if (!trigger_all_cpu_backtrace()) { 243 struct pt_regs *regs = get_irq_regs(); 244 245 if (regs) { 246 printk(KERN_INFO "CPU%d:\n", smp_processor_id()); 247 show_regs(regs); 248 } 249 schedule_work(&sysrq_showallcpus); 250 } 251 } 252 253 static struct sysrq_key_op sysrq_showallcpus_op = { 254 .handler = sysrq_handle_showallcpus, 255 .help_msg = "show-backtrace-all-active-cpus(l)", 256 .action_msg = "Show backtrace of all active CPUs", 257 .enable_mask = SYSRQ_ENABLE_DUMP, 258 }; 259 #endif 260 261 static void sysrq_handle_showregs(int key) 262 { 263 struct pt_regs *regs = get_irq_regs(); 264 if (regs) 265 show_regs(regs); 266 perf_event_print_debug(); 267 } 268 static struct sysrq_key_op sysrq_showregs_op = { 269 .handler = sysrq_handle_showregs, 270 .help_msg = "show-registers(p)", 271 .action_msg = "Show Regs", 272 .enable_mask = SYSRQ_ENABLE_DUMP, 273 }; 274 275 static void sysrq_handle_showstate(int key) 276 { 277 show_state(); 278 } 279 static struct sysrq_key_op sysrq_showstate_op = { 280 .handler = sysrq_handle_showstate, 281 .help_msg = "show-task-states(t)", 282 .action_msg = "Show State", 283 .enable_mask = SYSRQ_ENABLE_DUMP, 284 }; 285 286 static void sysrq_handle_showstate_blocked(int key) 287 { 288 show_state_filter(TASK_UNINTERRUPTIBLE); 289 } 290 static struct sysrq_key_op sysrq_showstate_blocked_op = { 291 .handler = sysrq_handle_showstate_blocked, 292 .help_msg = "show-blocked-tasks(w)", 293 .action_msg = "Show Blocked State", 294 .enable_mask = SYSRQ_ENABLE_DUMP, 295 }; 296 297 #ifdef CONFIG_TRACING 298 #include <linux/ftrace.h> 299 300 static void sysrq_ftrace_dump(int key) 301 { 302 ftrace_dump(DUMP_ALL); 303 } 304 static struct sysrq_key_op sysrq_ftrace_dump_op = { 305 .handler = sysrq_ftrace_dump, 306 .help_msg = "dump-ftrace-buffer(z)", 307 .action_msg = "Dump ftrace buffer", 308 .enable_mask = SYSRQ_ENABLE_DUMP, 309 }; 310 #else 311 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 312 #endif 313 314 static void sysrq_handle_showmem(int key) 315 { 316 show_mem(0); 317 } 318 static struct sysrq_key_op sysrq_showmem_op = { 319 .handler = sysrq_handle_showmem, 320 .help_msg = "show-memory-usage(m)", 321 .action_msg = "Show Memory", 322 .enable_mask = SYSRQ_ENABLE_DUMP, 323 }; 324 325 /* 326 * Signal sysrq helper function. Sends a signal to all user processes. 327 */ 328 static void send_sig_all(int sig) 329 { 330 struct task_struct *p; 331 332 read_lock(&tasklist_lock); 333 for_each_process(p) { 334 if (p->flags & PF_KTHREAD) 335 continue; 336 if (is_global_init(p)) 337 continue; 338 339 do_send_sig_info(sig, SEND_SIG_FORCED, p, true); 340 } 341 read_unlock(&tasklist_lock); 342 } 343 344 static void sysrq_handle_term(int key) 345 { 346 send_sig_all(SIGTERM); 347 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 348 } 349 static struct sysrq_key_op sysrq_term_op = { 350 .handler = sysrq_handle_term, 351 .help_msg = "terminate-all-tasks(e)", 352 .action_msg = "Terminate All Tasks", 353 .enable_mask = SYSRQ_ENABLE_SIGNAL, 354 }; 355 356 static void moom_callback(struct work_struct *ignored) 357 { 358 out_of_memory(node_zonelist(first_memory_node, GFP_KERNEL), GFP_KERNEL, 359 0, NULL, true); 360 } 361 362 static DECLARE_WORK(moom_work, moom_callback); 363 364 static void sysrq_handle_moom(int key) 365 { 366 schedule_work(&moom_work); 367 } 368 static struct sysrq_key_op sysrq_moom_op = { 369 .handler = sysrq_handle_moom, 370 .help_msg = "memory-full-oom-kill(f)", 371 .action_msg = "Manual OOM execution", 372 .enable_mask = SYSRQ_ENABLE_SIGNAL, 373 }; 374 375 #ifdef CONFIG_BLOCK 376 static void sysrq_handle_thaw(int key) 377 { 378 emergency_thaw_all(); 379 } 380 static struct sysrq_key_op sysrq_thaw_op = { 381 .handler = sysrq_handle_thaw, 382 .help_msg = "thaw-filesystems(j)", 383 .action_msg = "Emergency Thaw of all frozen filesystems", 384 .enable_mask = SYSRQ_ENABLE_SIGNAL, 385 }; 386 #endif 387 388 static void sysrq_handle_kill(int key) 389 { 390 send_sig_all(SIGKILL); 391 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 392 } 393 static struct sysrq_key_op sysrq_kill_op = { 394 .handler = sysrq_handle_kill, 395 .help_msg = "kill-all-tasks(i)", 396 .action_msg = "Kill All Tasks", 397 .enable_mask = SYSRQ_ENABLE_SIGNAL, 398 }; 399 400 static void sysrq_handle_unrt(int key) 401 { 402 normalize_rt_tasks(); 403 } 404 static struct sysrq_key_op sysrq_unrt_op = { 405 .handler = sysrq_handle_unrt, 406 .help_msg = "nice-all-RT-tasks(n)", 407 .action_msg = "Nice All RT Tasks", 408 .enable_mask = SYSRQ_ENABLE_RTNICE, 409 }; 410 411 /* Key Operations table and lock */ 412 static DEFINE_SPINLOCK(sysrq_key_table_lock); 413 414 static struct sysrq_key_op *sysrq_key_table[36] = { 415 &sysrq_loglevel_op, /* 0 */ 416 &sysrq_loglevel_op, /* 1 */ 417 &sysrq_loglevel_op, /* 2 */ 418 &sysrq_loglevel_op, /* 3 */ 419 &sysrq_loglevel_op, /* 4 */ 420 &sysrq_loglevel_op, /* 5 */ 421 &sysrq_loglevel_op, /* 6 */ 422 &sysrq_loglevel_op, /* 7 */ 423 &sysrq_loglevel_op, /* 8 */ 424 &sysrq_loglevel_op, /* 9 */ 425 426 /* 427 * a: Don't use for system provided sysrqs, it is handled specially on 428 * sparc and will never arrive. 429 */ 430 NULL, /* a */ 431 &sysrq_reboot_op, /* b */ 432 &sysrq_crash_op, /* c & ibm_emac driver debug */ 433 &sysrq_showlocks_op, /* d */ 434 &sysrq_term_op, /* e */ 435 &sysrq_moom_op, /* f */ 436 /* g: May be registered for the kernel debugger */ 437 NULL, /* g */ 438 NULL, /* h - reserved for help */ 439 &sysrq_kill_op, /* i */ 440 #ifdef CONFIG_BLOCK 441 &sysrq_thaw_op, /* j */ 442 #else 443 NULL, /* j */ 444 #endif 445 &sysrq_SAK_op, /* k */ 446 #ifdef CONFIG_SMP 447 &sysrq_showallcpus_op, /* l */ 448 #else 449 NULL, /* l */ 450 #endif 451 &sysrq_showmem_op, /* m */ 452 &sysrq_unrt_op, /* n */ 453 /* o: This will often be registered as 'Off' at init time */ 454 NULL, /* o */ 455 &sysrq_showregs_op, /* p */ 456 &sysrq_show_timers_op, /* q */ 457 &sysrq_unraw_op, /* r */ 458 &sysrq_sync_op, /* s */ 459 &sysrq_showstate_op, /* t */ 460 &sysrq_mountro_op, /* u */ 461 /* v: May be registered for frame buffer console restore */ 462 NULL, /* v */ 463 &sysrq_showstate_blocked_op, /* w */ 464 /* x: May be registered on ppc/powerpc for xmon */ 465 /* x: May be registered on sparc64 for global PMU dump */ 466 NULL, /* x */ 467 /* y: May be registered on sparc64 for global register dump */ 468 NULL, /* y */ 469 &sysrq_ftrace_dump_op, /* z */ 470 }; 471 472 /* key2index calculation, -1 on invalid index */ 473 static int sysrq_key_table_key2index(int key) 474 { 475 int retval; 476 477 if ((key >= '0') && (key <= '9')) 478 retval = key - '0'; 479 else if ((key >= 'a') && (key <= 'z')) 480 retval = key + 10 - 'a'; 481 else 482 retval = -1; 483 return retval; 484 } 485 486 /* 487 * get and put functions for the table, exposed to modules. 488 */ 489 struct sysrq_key_op *__sysrq_get_key_op(int key) 490 { 491 struct sysrq_key_op *op_p = NULL; 492 int i; 493 494 i = sysrq_key_table_key2index(key); 495 if (i != -1) 496 op_p = sysrq_key_table[i]; 497 498 return op_p; 499 } 500 501 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 502 { 503 int i = sysrq_key_table_key2index(key); 504 505 if (i != -1) 506 sysrq_key_table[i] = op_p; 507 } 508 509 void __handle_sysrq(int key, bool check_mask) 510 { 511 struct sysrq_key_op *op_p; 512 int orig_log_level; 513 int i; 514 515 rcu_sysrq_start(); 516 rcu_read_lock(); 517 /* 518 * Raise the apparent loglevel to maximum so that the sysrq header 519 * is shown to provide the user with positive feedback. We do not 520 * simply emit this at KERN_EMERG as that would change message 521 * routing in the consumers of /proc/kmsg. 522 */ 523 orig_log_level = console_loglevel; 524 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 525 printk(KERN_INFO "SysRq : "); 526 527 op_p = __sysrq_get_key_op(key); 528 if (op_p) { 529 /* 530 * Should we check for enabled operations (/proc/sysrq-trigger 531 * should not) and is the invoked operation enabled? 532 */ 533 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 534 printk("%s\n", op_p->action_msg); 535 console_loglevel = orig_log_level; 536 op_p->handler(key); 537 } else { 538 printk("This sysrq operation is disabled.\n"); 539 } 540 } else { 541 printk("HELP : "); 542 /* Only print the help msg once per handler */ 543 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 544 if (sysrq_key_table[i]) { 545 int j; 546 547 for (j = 0; sysrq_key_table[i] != 548 sysrq_key_table[j]; j++) 549 ; 550 if (j != i) 551 continue; 552 printk("%s ", sysrq_key_table[i]->help_msg); 553 } 554 } 555 printk("\n"); 556 console_loglevel = orig_log_level; 557 } 558 rcu_read_unlock(); 559 rcu_sysrq_end(); 560 } 561 562 void handle_sysrq(int key) 563 { 564 if (sysrq_on()) 565 __handle_sysrq(key, true); 566 } 567 EXPORT_SYMBOL(handle_sysrq); 568 569 #ifdef CONFIG_INPUT 570 571 /* Simple translation table for the SysRq keys */ 572 static const unsigned char sysrq_xlate[KEY_CNT] = 573 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 574 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 575 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 576 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 577 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 578 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 579 "\r\000/"; /* 0x60 - 0x6f */ 580 581 struct sysrq_state { 582 struct input_handle handle; 583 struct work_struct reinject_work; 584 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 585 unsigned int alt; 586 unsigned int alt_use; 587 bool active; 588 bool need_reinject; 589 bool reinjecting; 590 591 /* reset sequence handling */ 592 bool reset_canceled; 593 bool reset_requested; 594 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 595 int reset_seq_len; 596 int reset_seq_cnt; 597 int reset_seq_version; 598 struct timer_list keyreset_timer; 599 }; 600 601 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 602 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 603 static unsigned int sysrq_reset_seq_len; 604 static unsigned int sysrq_reset_seq_version = 1; 605 606 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 607 { 608 int i; 609 unsigned short key; 610 611 state->reset_seq_cnt = 0; 612 613 for (i = 0; i < sysrq_reset_seq_len; i++) { 614 key = sysrq_reset_seq[i]; 615 616 if (key == KEY_RESERVED || key > KEY_MAX) 617 break; 618 619 __set_bit(key, state->reset_keybit); 620 state->reset_seq_len++; 621 622 if (test_bit(key, state->key_down)) 623 state->reset_seq_cnt++; 624 } 625 626 /* Disable reset until old keys are not released */ 627 state->reset_canceled = state->reset_seq_cnt != 0; 628 629 state->reset_seq_version = sysrq_reset_seq_version; 630 } 631 632 static void sysrq_do_reset(unsigned long _state) 633 { 634 struct sysrq_state *state = (struct sysrq_state *) _state; 635 636 state->reset_requested = true; 637 638 sys_sync(); 639 kernel_restart(NULL); 640 } 641 642 static void sysrq_handle_reset_request(struct sysrq_state *state) 643 { 644 if (state->reset_requested) 645 __handle_sysrq(sysrq_xlate[KEY_B], false); 646 647 if (sysrq_reset_downtime_ms) 648 mod_timer(&state->keyreset_timer, 649 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 650 else 651 sysrq_do_reset((unsigned long)state); 652 } 653 654 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 655 unsigned int code, int value) 656 { 657 if (!test_bit(code, state->reset_keybit)) { 658 /* 659 * Pressing any key _not_ in reset sequence cancels 660 * the reset sequence. Also cancelling the timer in 661 * case additional keys were pressed after a reset 662 * has been requested. 663 */ 664 if (value && state->reset_seq_cnt) { 665 state->reset_canceled = true; 666 del_timer(&state->keyreset_timer); 667 } 668 } else if (value == 0) { 669 /* 670 * Key release - all keys in the reset sequence need 671 * to be pressed and held for the reset timeout 672 * to hold. 673 */ 674 del_timer(&state->keyreset_timer); 675 676 if (--state->reset_seq_cnt == 0) 677 state->reset_canceled = false; 678 } else if (value == 1) { 679 /* key press, not autorepeat */ 680 if (++state->reset_seq_cnt == state->reset_seq_len && 681 !state->reset_canceled) { 682 sysrq_handle_reset_request(state); 683 } 684 } 685 } 686 687 #ifdef CONFIG_OF 688 static void sysrq_of_get_keyreset_config(void) 689 { 690 u32 key; 691 struct device_node *np; 692 struct property *prop; 693 const __be32 *p; 694 695 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 696 if (!np) { 697 pr_debug("No sysrq node found"); 698 return; 699 } 700 701 /* Reset in case a __weak definition was present */ 702 sysrq_reset_seq_len = 0; 703 704 of_property_for_each_u32(np, "keyset", prop, p, key) { 705 if (key == KEY_RESERVED || key > KEY_MAX || 706 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 707 break; 708 709 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 710 } 711 712 /* Get reset timeout if any. */ 713 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 714 } 715 #else 716 static void sysrq_of_get_keyreset_config(void) 717 { 718 } 719 #endif 720 721 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 722 { 723 struct sysrq_state *sysrq = 724 container_of(work, struct sysrq_state, reinject_work); 725 struct input_handle *handle = &sysrq->handle; 726 unsigned int alt_code = sysrq->alt_use; 727 728 if (sysrq->need_reinject) { 729 /* we do not want the assignment to be reordered */ 730 sysrq->reinjecting = true; 731 mb(); 732 733 /* Simulate press and release of Alt + SysRq */ 734 input_inject_event(handle, EV_KEY, alt_code, 1); 735 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 736 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 737 738 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 739 input_inject_event(handle, EV_KEY, alt_code, 0); 740 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 741 742 mb(); 743 sysrq->reinjecting = false; 744 } 745 } 746 747 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 748 unsigned int code, int value) 749 { 750 bool was_active = sysrq->active; 751 bool suppress; 752 753 switch (code) { 754 755 case KEY_LEFTALT: 756 case KEY_RIGHTALT: 757 if (!value) { 758 /* One of ALTs is being released */ 759 if (sysrq->active && code == sysrq->alt_use) 760 sysrq->active = false; 761 762 sysrq->alt = KEY_RESERVED; 763 764 } else if (value != 2) { 765 sysrq->alt = code; 766 sysrq->need_reinject = false; 767 } 768 break; 769 770 case KEY_SYSRQ: 771 if (value == 1 && sysrq->alt != KEY_RESERVED) { 772 sysrq->active = true; 773 sysrq->alt_use = sysrq->alt; 774 /* 775 * If nothing else will be pressed we'll need 776 * to re-inject Alt-SysRq keysroke. 777 */ 778 sysrq->need_reinject = true; 779 } 780 781 /* 782 * Pretend that sysrq was never pressed at all. This 783 * is needed to properly handle KGDB which will try 784 * to release all keys after exiting debugger. If we 785 * do not clear key bit it KGDB will end up sending 786 * release events for Alt and SysRq, potentially 787 * triggering print screen function. 788 */ 789 if (sysrq->active) 790 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 791 792 break; 793 794 default: 795 if (sysrq->active && value && value != 2) { 796 sysrq->need_reinject = false; 797 __handle_sysrq(sysrq_xlate[code], true); 798 } 799 break; 800 } 801 802 suppress = sysrq->active; 803 804 if (!sysrq->active) { 805 806 /* 807 * See if reset sequence has changed since the last time. 808 */ 809 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 810 sysrq_parse_reset_sequence(sysrq); 811 812 /* 813 * If we are not suppressing key presses keep track of 814 * keyboard state so we can release keys that have been 815 * pressed before entering SysRq mode. 816 */ 817 if (value) 818 set_bit(code, sysrq->key_down); 819 else 820 clear_bit(code, sysrq->key_down); 821 822 if (was_active) 823 schedule_work(&sysrq->reinject_work); 824 825 /* Check for reset sequence */ 826 sysrq_detect_reset_sequence(sysrq, code, value); 827 828 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 829 /* 830 * Pass on release events for keys that was pressed before 831 * entering SysRq mode. 832 */ 833 suppress = false; 834 } 835 836 return suppress; 837 } 838 839 static bool sysrq_filter(struct input_handle *handle, 840 unsigned int type, unsigned int code, int value) 841 { 842 struct sysrq_state *sysrq = handle->private; 843 bool suppress; 844 845 /* 846 * Do not filter anything if we are in the process of re-injecting 847 * Alt+SysRq combination. 848 */ 849 if (sysrq->reinjecting) 850 return false; 851 852 switch (type) { 853 854 case EV_SYN: 855 suppress = false; 856 break; 857 858 case EV_KEY: 859 suppress = sysrq_handle_keypress(sysrq, code, value); 860 break; 861 862 default: 863 suppress = sysrq->active; 864 break; 865 } 866 867 return suppress; 868 } 869 870 static int sysrq_connect(struct input_handler *handler, 871 struct input_dev *dev, 872 const struct input_device_id *id) 873 { 874 struct sysrq_state *sysrq; 875 int error; 876 877 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 878 if (!sysrq) 879 return -ENOMEM; 880 881 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 882 883 sysrq->handle.dev = dev; 884 sysrq->handle.handler = handler; 885 sysrq->handle.name = "sysrq"; 886 sysrq->handle.private = sysrq; 887 setup_timer(&sysrq->keyreset_timer, 888 sysrq_do_reset, (unsigned long)sysrq); 889 890 error = input_register_handle(&sysrq->handle); 891 if (error) { 892 pr_err("Failed to register input sysrq handler, error %d\n", 893 error); 894 goto err_free; 895 } 896 897 error = input_open_device(&sysrq->handle); 898 if (error) { 899 pr_err("Failed to open input device, error %d\n", error); 900 goto err_unregister; 901 } 902 903 return 0; 904 905 err_unregister: 906 input_unregister_handle(&sysrq->handle); 907 err_free: 908 kfree(sysrq); 909 return error; 910 } 911 912 static void sysrq_disconnect(struct input_handle *handle) 913 { 914 struct sysrq_state *sysrq = handle->private; 915 916 input_close_device(handle); 917 cancel_work_sync(&sysrq->reinject_work); 918 del_timer_sync(&sysrq->keyreset_timer); 919 input_unregister_handle(handle); 920 kfree(sysrq); 921 } 922 923 /* 924 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 925 * keyboards have SysRq key predefined and so user may add it to keymap 926 * later, but we expect all such keyboards to have left alt. 927 */ 928 static const struct input_device_id sysrq_ids[] = { 929 { 930 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 931 INPUT_DEVICE_ID_MATCH_KEYBIT, 932 .evbit = { BIT_MASK(EV_KEY) }, 933 .keybit = { BIT_MASK(KEY_LEFTALT) }, 934 }, 935 { }, 936 }; 937 938 static struct input_handler sysrq_handler = { 939 .filter = sysrq_filter, 940 .connect = sysrq_connect, 941 .disconnect = sysrq_disconnect, 942 .name = "sysrq", 943 .id_table = sysrq_ids, 944 }; 945 946 static bool sysrq_handler_registered; 947 948 static inline void sysrq_register_handler(void) 949 { 950 unsigned short key; 951 int error; 952 int i; 953 954 /* First check if a __weak interface was instantiated. */ 955 for (i = 0; i < ARRAY_SIZE(sysrq_reset_seq); i++) { 956 key = platform_sysrq_reset_seq[i]; 957 if (key == KEY_RESERVED || key > KEY_MAX) 958 break; 959 960 sysrq_reset_seq[sysrq_reset_seq_len++] = key; 961 } 962 963 /* 964 * DT configuration takes precedence over anything that would 965 * have been defined via the __weak interface. 966 */ 967 sysrq_of_get_keyreset_config(); 968 969 error = input_register_handler(&sysrq_handler); 970 if (error) 971 pr_err("Failed to register input handler, error %d", error); 972 else 973 sysrq_handler_registered = true; 974 } 975 976 static inline void sysrq_unregister_handler(void) 977 { 978 if (sysrq_handler_registered) { 979 input_unregister_handler(&sysrq_handler); 980 sysrq_handler_registered = false; 981 } 982 } 983 984 static int sysrq_reset_seq_param_set(const char *buffer, 985 const struct kernel_param *kp) 986 { 987 unsigned long val; 988 int error; 989 990 error = kstrtoul(buffer, 0, &val); 991 if (error < 0) 992 return error; 993 994 if (val > KEY_MAX) 995 return -EINVAL; 996 997 *((unsigned short *)kp->arg) = val; 998 sysrq_reset_seq_version++; 999 1000 return 0; 1001 } 1002 1003 static struct kernel_param_ops param_ops_sysrq_reset_seq = { 1004 .get = param_get_ushort, 1005 .set = sysrq_reset_seq_param_set, 1006 }; 1007 1008 #define param_check_sysrq_reset_seq(name, p) \ 1009 __param_check(name, p, unsigned short) 1010 1011 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1012 &sysrq_reset_seq_len, 0644); 1013 1014 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1015 1016 #else 1017 1018 static inline void sysrq_register_handler(void) 1019 { 1020 } 1021 1022 static inline void sysrq_unregister_handler(void) 1023 { 1024 } 1025 1026 #endif /* CONFIG_INPUT */ 1027 1028 int sysrq_toggle_support(int enable_mask) 1029 { 1030 bool was_enabled = sysrq_on(); 1031 1032 sysrq_enabled = enable_mask; 1033 1034 if (was_enabled != sysrq_on()) { 1035 if (sysrq_on()) 1036 sysrq_register_handler(); 1037 else 1038 sysrq_unregister_handler(); 1039 } 1040 1041 return 0; 1042 } 1043 1044 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1045 struct sysrq_key_op *remove_op_p) 1046 { 1047 int retval; 1048 1049 spin_lock(&sysrq_key_table_lock); 1050 if (__sysrq_get_key_op(key) == remove_op_p) { 1051 __sysrq_put_key_op(key, insert_op_p); 1052 retval = 0; 1053 } else { 1054 retval = -1; 1055 } 1056 spin_unlock(&sysrq_key_table_lock); 1057 1058 /* 1059 * A concurrent __handle_sysrq either got the old op or the new op. 1060 * Wait for it to go away before returning, so the code for an old 1061 * op is not freed (eg. on module unload) while it is in use. 1062 */ 1063 synchronize_rcu(); 1064 1065 return retval; 1066 } 1067 1068 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1069 { 1070 return __sysrq_swap_key_ops(key, op_p, NULL); 1071 } 1072 EXPORT_SYMBOL(register_sysrq_key); 1073 1074 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1075 { 1076 return __sysrq_swap_key_ops(key, NULL, op_p); 1077 } 1078 EXPORT_SYMBOL(unregister_sysrq_key); 1079 1080 #ifdef CONFIG_PROC_FS 1081 /* 1082 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1083 */ 1084 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1085 size_t count, loff_t *ppos) 1086 { 1087 if (count) { 1088 char c; 1089 1090 if (get_user(c, buf)) 1091 return -EFAULT; 1092 __handle_sysrq(c, false); 1093 } 1094 1095 return count; 1096 } 1097 1098 static const struct file_operations proc_sysrq_trigger_operations = { 1099 .write = write_sysrq_trigger, 1100 .llseek = noop_llseek, 1101 }; 1102 1103 static void sysrq_init_procfs(void) 1104 { 1105 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1106 &proc_sysrq_trigger_operations)) 1107 pr_err("Failed to register proc interface\n"); 1108 } 1109 1110 #else 1111 1112 static inline void sysrq_init_procfs(void) 1113 { 1114 } 1115 1116 #endif /* CONFIG_PROC_FS */ 1117 1118 static int __init sysrq_init(void) 1119 { 1120 sysrq_init_procfs(); 1121 1122 if (sysrq_on()) 1123 sysrq_register_handler(); 1124 1125 return 0; 1126 } 1127 module_init(sysrq_init); 1128