1 /* 2 * Kernel Debug Core 3 * 4 * Maintainer: Jason Wessel <jason.wessel@windriver.com> 5 * 6 * Copyright (C) 2000-2001 VERITAS Software Corporation. 7 * Copyright (C) 2002-2004 Timesys Corporation 8 * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com> 9 * Copyright (C) 2004 Pavel Machek <pavel@ucw.cz> 10 * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org> 11 * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd. 12 * Copyright (C) 2005-2009 Wind River Systems, Inc. 13 * Copyright (C) 2007 MontaVista Software, Inc. 14 * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> 15 * 16 * Contributors at various stages not listed above: 17 * Jason Wessel ( jason.wessel@windriver.com ) 18 * George Anzinger <george@mvista.com> 19 * Anurekh Saxena (anurekh.saxena@timesys.com) 20 * Lake Stevens Instrument Division (Glenn Engel) 21 * Jim Kingdon, Cygnus Support. 22 * 23 * Original KGDB stub: David Grothe <dave@gcom.com>, 24 * Tigran Aivazian <tigran@sco.com> 25 * 26 * This file is licensed under the terms of the GNU General Public License 27 * version 2. This program is licensed "as is" without any warranty of any 28 * kind, whether express or implied. 29 */ 30 31 #define pr_fmt(fmt) "KGDB: " fmt 32 33 #include <linux/pid_namespace.h> 34 #include <linux/clocksource.h> 35 #include <linux/serial_core.h> 36 #include <linux/interrupt.h> 37 #include <linux/spinlock.h> 38 #include <linux/console.h> 39 #include <linux/threads.h> 40 #include <linux/uaccess.h> 41 #include <linux/kernel.h> 42 #include <linux/module.h> 43 #include <linux/ptrace.h> 44 #include <linux/string.h> 45 #include <linux/delay.h> 46 #include <linux/sched.h> 47 #include <linux/sysrq.h> 48 #include <linux/reboot.h> 49 #include <linux/init.h> 50 #include <linux/kgdb.h> 51 #include <linux/kdb.h> 52 #include <linux/pid.h> 53 #include <linux/smp.h> 54 #include <linux/mm.h> 55 #include <linux/vmacache.h> 56 #include <linux/rcupdate.h> 57 58 #include <asm/cacheflush.h> 59 #include <asm/byteorder.h> 60 #include <linux/atomic.h> 61 62 #include "debug_core.h" 63 64 static int kgdb_break_asap; 65 66 struct debuggerinfo_struct kgdb_info[NR_CPUS]; 67 68 /** 69 * kgdb_connected - Is a host GDB connected to us? 70 */ 71 int kgdb_connected; 72 EXPORT_SYMBOL_GPL(kgdb_connected); 73 74 /* All the KGDB handlers are installed */ 75 int kgdb_io_module_registered; 76 77 /* Guard for recursive entry */ 78 static int exception_level; 79 80 struct kgdb_io *dbg_io_ops; 81 static DEFINE_SPINLOCK(kgdb_registration_lock); 82 83 /* Action for the reboot notifiter, a global allow kdb to change it */ 84 static int kgdbreboot; 85 /* kgdb console driver is loaded */ 86 static int kgdb_con_registered; 87 /* determine if kgdb console output should be used */ 88 static int kgdb_use_con; 89 /* Flag for alternate operations for early debugging */ 90 bool dbg_is_early = true; 91 /* Next cpu to become the master debug core */ 92 int dbg_switch_cpu; 93 94 /* Use kdb or gdbserver mode */ 95 int dbg_kdb_mode = 1; 96 97 static int __init opt_kgdb_con(char *str) 98 { 99 kgdb_use_con = 1; 100 return 0; 101 } 102 103 early_param("kgdbcon", opt_kgdb_con); 104 105 module_param(kgdb_use_con, int, 0644); 106 module_param(kgdbreboot, int, 0644); 107 108 /* 109 * Holds information about breakpoints in a kernel. These breakpoints are 110 * added and removed by gdb. 111 */ 112 static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = { 113 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED } 114 }; 115 116 /* 117 * The CPU# of the active CPU, or -1 if none: 118 */ 119 atomic_t kgdb_active = ATOMIC_INIT(-1); 120 EXPORT_SYMBOL_GPL(kgdb_active); 121 static DEFINE_RAW_SPINLOCK(dbg_master_lock); 122 static DEFINE_RAW_SPINLOCK(dbg_slave_lock); 123 124 /* 125 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early 126 * bootup code (which might not have percpu set up yet): 127 */ 128 static atomic_t masters_in_kgdb; 129 static atomic_t slaves_in_kgdb; 130 static atomic_t kgdb_break_tasklet_var; 131 atomic_t kgdb_setting_breakpoint; 132 133 struct task_struct *kgdb_usethread; 134 struct task_struct *kgdb_contthread; 135 136 int kgdb_single_step; 137 static pid_t kgdb_sstep_pid; 138 139 /* to keep track of the CPU which is doing the single stepping*/ 140 atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1); 141 142 /* 143 * If you are debugging a problem where roundup (the collection of 144 * all other CPUs) is a problem [this should be extremely rare], 145 * then use the nokgdbroundup option to avoid roundup. In that case 146 * the other CPUs might interfere with your debugging context, so 147 * use this with care: 148 */ 149 static int kgdb_do_roundup = 1; 150 151 static int __init opt_nokgdbroundup(char *str) 152 { 153 kgdb_do_roundup = 0; 154 155 return 0; 156 } 157 158 early_param("nokgdbroundup", opt_nokgdbroundup); 159 160 /* 161 * Finally, some KGDB code :-) 162 */ 163 164 /* 165 * Weak aliases for breakpoint management, 166 * can be overriden by architectures when needed: 167 */ 168 int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) 169 { 170 int err; 171 172 err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr, 173 BREAK_INSTR_SIZE); 174 if (err) 175 return err; 176 err = probe_kernel_write((char *)bpt->bpt_addr, 177 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE); 178 return err; 179 } 180 181 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt) 182 { 183 return probe_kernel_write((char *)bpt->bpt_addr, 184 (char *)bpt->saved_instr, BREAK_INSTR_SIZE); 185 } 186 187 int __weak kgdb_validate_break_address(unsigned long addr) 188 { 189 struct kgdb_bkpt tmp; 190 int err; 191 /* Validate setting the breakpoint and then removing it. If the 192 * remove fails, the kernel needs to emit a bad message because we 193 * are deep trouble not being able to put things back the way we 194 * found them. 195 */ 196 tmp.bpt_addr = addr; 197 err = kgdb_arch_set_breakpoint(&tmp); 198 if (err) 199 return err; 200 err = kgdb_arch_remove_breakpoint(&tmp); 201 if (err) 202 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n", 203 addr); 204 return err; 205 } 206 207 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs) 208 { 209 return instruction_pointer(regs); 210 } 211 212 int __weak kgdb_arch_init(void) 213 { 214 return 0; 215 } 216 217 int __weak kgdb_skipexception(int exception, struct pt_regs *regs) 218 { 219 return 0; 220 } 221 222 /* 223 * Some architectures need cache flushes when we set/clear a 224 * breakpoint: 225 */ 226 static void kgdb_flush_swbreak_addr(unsigned long addr) 227 { 228 if (!CACHE_FLUSH_IS_SAFE) 229 return; 230 231 if (current->mm) { 232 int i; 233 234 for (i = 0; i < VMACACHE_SIZE; i++) { 235 if (!current->vmacache[i]) 236 continue; 237 flush_cache_range(current->vmacache[i], 238 addr, addr + BREAK_INSTR_SIZE); 239 } 240 } 241 242 /* Force flush instruction cache if it was outside the mm */ 243 flush_icache_range(addr, addr + BREAK_INSTR_SIZE); 244 } 245 246 /* 247 * SW breakpoint management: 248 */ 249 int dbg_activate_sw_breakpoints(void) 250 { 251 int error; 252 int ret = 0; 253 int i; 254 255 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 256 if (kgdb_break[i].state != BP_SET) 257 continue; 258 259 error = kgdb_arch_set_breakpoint(&kgdb_break[i]); 260 if (error) { 261 ret = error; 262 pr_info("BP install failed: %lx\n", 263 kgdb_break[i].bpt_addr); 264 continue; 265 } 266 267 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); 268 kgdb_break[i].state = BP_ACTIVE; 269 } 270 return ret; 271 } 272 273 int dbg_set_sw_break(unsigned long addr) 274 { 275 int err = kgdb_validate_break_address(addr); 276 int breakno = -1; 277 int i; 278 279 if (err) 280 return err; 281 282 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 283 if ((kgdb_break[i].state == BP_SET) && 284 (kgdb_break[i].bpt_addr == addr)) 285 return -EEXIST; 286 } 287 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 288 if (kgdb_break[i].state == BP_REMOVED && 289 kgdb_break[i].bpt_addr == addr) { 290 breakno = i; 291 break; 292 } 293 } 294 295 if (breakno == -1) { 296 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 297 if (kgdb_break[i].state == BP_UNDEFINED) { 298 breakno = i; 299 break; 300 } 301 } 302 } 303 304 if (breakno == -1) 305 return -E2BIG; 306 307 kgdb_break[breakno].state = BP_SET; 308 kgdb_break[breakno].type = BP_BREAKPOINT; 309 kgdb_break[breakno].bpt_addr = addr; 310 311 return 0; 312 } 313 314 int dbg_deactivate_sw_breakpoints(void) 315 { 316 int error; 317 int ret = 0; 318 int i; 319 320 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 321 if (kgdb_break[i].state != BP_ACTIVE) 322 continue; 323 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); 324 if (error) { 325 pr_info("BP remove failed: %lx\n", 326 kgdb_break[i].bpt_addr); 327 ret = error; 328 } 329 330 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); 331 kgdb_break[i].state = BP_SET; 332 } 333 return ret; 334 } 335 336 int dbg_remove_sw_break(unsigned long addr) 337 { 338 int i; 339 340 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 341 if ((kgdb_break[i].state == BP_SET) && 342 (kgdb_break[i].bpt_addr == addr)) { 343 kgdb_break[i].state = BP_REMOVED; 344 return 0; 345 } 346 } 347 return -ENOENT; 348 } 349 350 int kgdb_isremovedbreak(unsigned long addr) 351 { 352 int i; 353 354 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 355 if ((kgdb_break[i].state == BP_REMOVED) && 356 (kgdb_break[i].bpt_addr == addr)) 357 return 1; 358 } 359 return 0; 360 } 361 362 int dbg_remove_all_break(void) 363 { 364 int error; 365 int i; 366 367 /* Clear memory breakpoints. */ 368 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 369 if (kgdb_break[i].state != BP_ACTIVE) 370 goto setundefined; 371 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); 372 if (error) 373 pr_err("breakpoint remove failed: %lx\n", 374 kgdb_break[i].bpt_addr); 375 setundefined: 376 kgdb_break[i].state = BP_UNDEFINED; 377 } 378 379 /* Clear hardware breakpoints. */ 380 if (arch_kgdb_ops.remove_all_hw_break) 381 arch_kgdb_ops.remove_all_hw_break(); 382 383 return 0; 384 } 385 386 /* 387 * Return true if there is a valid kgdb I/O module. Also if no 388 * debugger is attached a message can be printed to the console about 389 * waiting for the debugger to attach. 390 * 391 * The print_wait argument is only to be true when called from inside 392 * the core kgdb_handle_exception, because it will wait for the 393 * debugger to attach. 394 */ 395 static int kgdb_io_ready(int print_wait) 396 { 397 if (!dbg_io_ops) 398 return 0; 399 if (kgdb_connected) 400 return 1; 401 if (atomic_read(&kgdb_setting_breakpoint)) 402 return 1; 403 if (print_wait) { 404 #ifdef CONFIG_KGDB_KDB 405 if (!dbg_kdb_mode) 406 pr_crit("waiting... or $3#33 for KDB\n"); 407 #else 408 pr_crit("Waiting for remote debugger\n"); 409 #endif 410 } 411 return 1; 412 } 413 414 static int kgdb_reenter_check(struct kgdb_state *ks) 415 { 416 unsigned long addr; 417 418 if (atomic_read(&kgdb_active) != raw_smp_processor_id()) 419 return 0; 420 421 /* Panic on recursive debugger calls: */ 422 exception_level++; 423 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs); 424 dbg_deactivate_sw_breakpoints(); 425 426 /* 427 * If the break point removed ok at the place exception 428 * occurred, try to recover and print a warning to the end 429 * user because the user planted a breakpoint in a place that 430 * KGDB needs in order to function. 431 */ 432 if (dbg_remove_sw_break(addr) == 0) { 433 exception_level = 0; 434 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 435 dbg_activate_sw_breakpoints(); 436 pr_crit("re-enter error: breakpoint removed %lx\n", addr); 437 WARN_ON_ONCE(1); 438 439 return 1; 440 } 441 dbg_remove_all_break(); 442 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 443 444 if (exception_level > 1) { 445 dump_stack(); 446 panic("Recursive entry to debugger"); 447 } 448 449 pr_crit("re-enter exception: ALL breakpoints killed\n"); 450 #ifdef CONFIG_KGDB_KDB 451 /* Allow kdb to debug itself one level */ 452 return 0; 453 #endif 454 dump_stack(); 455 panic("Recursive entry to debugger"); 456 457 return 1; 458 } 459 460 static void dbg_touch_watchdogs(void) 461 { 462 touch_softlockup_watchdog_sync(); 463 clocksource_touch_watchdog(); 464 rcu_cpu_stall_reset(); 465 } 466 467 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, 468 int exception_state) 469 { 470 unsigned long flags; 471 int sstep_tries = 100; 472 int error; 473 int cpu; 474 int trace_on = 0; 475 int online_cpus = num_online_cpus(); 476 u64 time_left; 477 478 kgdb_info[ks->cpu].enter_kgdb++; 479 kgdb_info[ks->cpu].exception_state |= exception_state; 480 481 if (exception_state == DCPU_WANT_MASTER) 482 atomic_inc(&masters_in_kgdb); 483 else 484 atomic_inc(&slaves_in_kgdb); 485 486 if (arch_kgdb_ops.disable_hw_break) 487 arch_kgdb_ops.disable_hw_break(regs); 488 489 acquirelock: 490 /* 491 * Interrupts will be restored by the 'trap return' code, except when 492 * single stepping. 493 */ 494 local_irq_save(flags); 495 496 cpu = ks->cpu; 497 kgdb_info[cpu].debuggerinfo = regs; 498 kgdb_info[cpu].task = current; 499 kgdb_info[cpu].ret_state = 0; 500 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT; 501 502 /* Make sure the above info reaches the primary CPU */ 503 smp_mb(); 504 505 if (exception_level == 1) { 506 if (raw_spin_trylock(&dbg_master_lock)) 507 atomic_xchg(&kgdb_active, cpu); 508 goto cpu_master_loop; 509 } 510 511 /* 512 * CPU will loop if it is a slave or request to become a kgdb 513 * master cpu and acquire the kgdb_active lock: 514 */ 515 while (1) { 516 cpu_loop: 517 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) { 518 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER; 519 goto cpu_master_loop; 520 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) { 521 if (raw_spin_trylock(&dbg_master_lock)) { 522 atomic_xchg(&kgdb_active, cpu); 523 break; 524 } 525 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) { 526 if (!raw_spin_is_locked(&dbg_slave_lock)) 527 goto return_normal; 528 } else { 529 return_normal: 530 /* Return to normal operation by executing any 531 * hw breakpoint fixup. 532 */ 533 if (arch_kgdb_ops.correct_hw_break) 534 arch_kgdb_ops.correct_hw_break(); 535 if (trace_on) 536 tracing_on(); 537 kgdb_info[cpu].exception_state &= 538 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 539 kgdb_info[cpu].enter_kgdb--; 540 smp_mb__before_atomic(); 541 atomic_dec(&slaves_in_kgdb); 542 dbg_touch_watchdogs(); 543 local_irq_restore(flags); 544 return 0; 545 } 546 cpu_relax(); 547 } 548 549 /* 550 * For single stepping, try to only enter on the processor 551 * that was single stepping. To guard against a deadlock, the 552 * kernel will only try for the value of sstep_tries before 553 * giving up and continuing on. 554 */ 555 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 && 556 (kgdb_info[cpu].task && 557 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) { 558 atomic_set(&kgdb_active, -1); 559 raw_spin_unlock(&dbg_master_lock); 560 dbg_touch_watchdogs(); 561 local_irq_restore(flags); 562 563 goto acquirelock; 564 } 565 566 if (!kgdb_io_ready(1)) { 567 kgdb_info[cpu].ret_state = 1; 568 goto kgdb_restore; /* No I/O connection, resume the system */ 569 } 570 571 /* 572 * Don't enter if we have hit a removed breakpoint. 573 */ 574 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs)) 575 goto kgdb_restore; 576 577 /* Call the I/O driver's pre_exception routine */ 578 if (dbg_io_ops->pre_exception) 579 dbg_io_ops->pre_exception(); 580 581 /* 582 * Get the passive CPU lock which will hold all the non-primary 583 * CPU in a spin state while the debugger is active 584 */ 585 if (!kgdb_single_step) 586 raw_spin_lock(&dbg_slave_lock); 587 588 #ifdef CONFIG_SMP 589 /* If send_ready set, slaves are already waiting */ 590 if (ks->send_ready) 591 atomic_set(ks->send_ready, 1); 592 593 /* Signal the other CPUs to enter kgdb_wait() */ 594 else if ((!kgdb_single_step) && kgdb_do_roundup) 595 kgdb_roundup_cpus(flags); 596 #endif 597 598 /* 599 * Wait for the other CPUs to be notified and be waiting for us: 600 */ 601 time_left = loops_per_jiffy * HZ; 602 while (kgdb_do_roundup && --time_left && 603 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) != 604 online_cpus) 605 cpu_relax(); 606 if (!time_left) 607 pr_crit("Timed out waiting for secondary CPUs.\n"); 608 609 /* 610 * At this point the primary processor is completely 611 * in the debugger and all secondary CPUs are quiescent 612 */ 613 dbg_deactivate_sw_breakpoints(); 614 kgdb_single_step = 0; 615 kgdb_contthread = current; 616 exception_level = 0; 617 trace_on = tracing_is_on(); 618 if (trace_on) 619 tracing_off(); 620 621 while (1) { 622 cpu_master_loop: 623 if (dbg_kdb_mode) { 624 kgdb_connected = 1; 625 error = kdb_stub(ks); 626 if (error == -1) 627 continue; 628 kgdb_connected = 0; 629 } else { 630 error = gdb_serial_stub(ks); 631 } 632 633 if (error == DBG_PASS_EVENT) { 634 dbg_kdb_mode = !dbg_kdb_mode; 635 } else if (error == DBG_SWITCH_CPU_EVENT) { 636 kgdb_info[dbg_switch_cpu].exception_state |= 637 DCPU_NEXT_MASTER; 638 goto cpu_loop; 639 } else { 640 kgdb_info[cpu].ret_state = error; 641 break; 642 } 643 } 644 645 /* Call the I/O driver's post_exception routine */ 646 if (dbg_io_ops->post_exception) 647 dbg_io_ops->post_exception(); 648 649 if (!kgdb_single_step) { 650 raw_spin_unlock(&dbg_slave_lock); 651 /* Wait till all the CPUs have quit from the debugger. */ 652 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb)) 653 cpu_relax(); 654 } 655 656 kgdb_restore: 657 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) { 658 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step); 659 if (kgdb_info[sstep_cpu].task) 660 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid; 661 else 662 kgdb_sstep_pid = 0; 663 } 664 if (arch_kgdb_ops.correct_hw_break) 665 arch_kgdb_ops.correct_hw_break(); 666 if (trace_on) 667 tracing_on(); 668 669 kgdb_info[cpu].exception_state &= 670 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 671 kgdb_info[cpu].enter_kgdb--; 672 smp_mb__before_atomic(); 673 atomic_dec(&masters_in_kgdb); 674 /* Free kgdb_active */ 675 atomic_set(&kgdb_active, -1); 676 raw_spin_unlock(&dbg_master_lock); 677 dbg_touch_watchdogs(); 678 local_irq_restore(flags); 679 680 return kgdb_info[cpu].ret_state; 681 } 682 683 /* 684 * kgdb_handle_exception() - main entry point from a kernel exception 685 * 686 * Locking hierarchy: 687 * interface locks, if any (begin_session) 688 * kgdb lock (kgdb_active) 689 */ 690 int 691 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 692 { 693 struct kgdb_state kgdb_var; 694 struct kgdb_state *ks = &kgdb_var; 695 int ret = 0; 696 697 if (arch_kgdb_ops.enable_nmi) 698 arch_kgdb_ops.enable_nmi(0); 699 /* 700 * Avoid entering the debugger if we were triggered due to an oops 701 * but panic_timeout indicates the system should automatically 702 * reboot on panic. We don't want to get stuck waiting for input 703 * on such systems, especially if its "just" an oops. 704 */ 705 if (signo != SIGTRAP && panic_timeout) 706 return 1; 707 708 memset(ks, 0, sizeof(struct kgdb_state)); 709 ks->cpu = raw_smp_processor_id(); 710 ks->ex_vector = evector; 711 ks->signo = signo; 712 ks->err_code = ecode; 713 ks->linux_regs = regs; 714 715 if (kgdb_reenter_check(ks)) 716 goto out; /* Ouch, double exception ! */ 717 if (kgdb_info[ks->cpu].enter_kgdb != 0) 718 goto out; 719 720 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 721 out: 722 if (arch_kgdb_ops.enable_nmi) 723 arch_kgdb_ops.enable_nmi(1); 724 return ret; 725 } 726 727 /* 728 * GDB places a breakpoint at this function to know dynamically 729 * loaded objects. It's not defined static so that only one instance with this 730 * name exists in the kernel. 731 */ 732 733 static int module_event(struct notifier_block *self, unsigned long val, 734 void *data) 735 { 736 return 0; 737 } 738 739 static struct notifier_block dbg_module_load_nb = { 740 .notifier_call = module_event, 741 }; 742 743 int kgdb_nmicallback(int cpu, void *regs) 744 { 745 #ifdef CONFIG_SMP 746 struct kgdb_state kgdb_var; 747 struct kgdb_state *ks = &kgdb_var; 748 749 memset(ks, 0, sizeof(struct kgdb_state)); 750 ks->cpu = cpu; 751 ks->linux_regs = regs; 752 753 if (kgdb_info[ks->cpu].enter_kgdb == 0 && 754 raw_spin_is_locked(&dbg_master_lock)) { 755 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE); 756 return 0; 757 } 758 #endif 759 return 1; 760 } 761 762 int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code, 763 atomic_t *send_ready) 764 { 765 #ifdef CONFIG_SMP 766 if (!kgdb_io_ready(0) || !send_ready) 767 return 1; 768 769 if (kgdb_info[cpu].enter_kgdb == 0) { 770 struct kgdb_state kgdb_var; 771 struct kgdb_state *ks = &kgdb_var; 772 773 memset(ks, 0, sizeof(struct kgdb_state)); 774 ks->cpu = cpu; 775 ks->ex_vector = trapnr; 776 ks->signo = SIGTRAP; 777 ks->err_code = err_code; 778 ks->linux_regs = regs; 779 ks->send_ready = send_ready; 780 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 781 return 0; 782 } 783 #endif 784 return 1; 785 } 786 787 static void kgdb_console_write(struct console *co, const char *s, 788 unsigned count) 789 { 790 unsigned long flags; 791 792 /* If we're debugging, or KGDB has not connected, don't try 793 * and print. */ 794 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode) 795 return; 796 797 local_irq_save(flags); 798 gdbstub_msg_write(s, count); 799 local_irq_restore(flags); 800 } 801 802 static struct console kgdbcons = { 803 .name = "kgdb", 804 .write = kgdb_console_write, 805 .flags = CON_PRINTBUFFER | CON_ENABLED, 806 .index = -1, 807 }; 808 809 #ifdef CONFIG_MAGIC_SYSRQ 810 static void sysrq_handle_dbg(int key) 811 { 812 if (!dbg_io_ops) { 813 pr_crit("ERROR: No KGDB I/O module available\n"); 814 return; 815 } 816 if (!kgdb_connected) { 817 #ifdef CONFIG_KGDB_KDB 818 if (!dbg_kdb_mode) 819 pr_crit("KGDB or $3#33 for KDB\n"); 820 #else 821 pr_crit("Entering KGDB\n"); 822 #endif 823 } 824 825 kgdb_breakpoint(); 826 } 827 828 static struct sysrq_key_op sysrq_dbg_op = { 829 .handler = sysrq_handle_dbg, 830 .help_msg = "debug(g)", 831 .action_msg = "DEBUG", 832 }; 833 #endif 834 835 static int kgdb_panic_event(struct notifier_block *self, 836 unsigned long val, 837 void *data) 838 { 839 /* 840 * Avoid entering the debugger if we were triggered due to a panic 841 * We don't want to get stuck waiting for input from user in such case. 842 * panic_timeout indicates the system should automatically 843 * reboot on panic. 844 */ 845 if (panic_timeout) 846 return NOTIFY_DONE; 847 848 if (dbg_kdb_mode) 849 kdb_printf("PANIC: %s\n", (char *)data); 850 kgdb_breakpoint(); 851 return NOTIFY_DONE; 852 } 853 854 static struct notifier_block kgdb_panic_event_nb = { 855 .notifier_call = kgdb_panic_event, 856 .priority = INT_MAX, 857 }; 858 859 void __weak kgdb_arch_late(void) 860 { 861 } 862 863 void __init dbg_late_init(void) 864 { 865 dbg_is_early = false; 866 if (kgdb_io_module_registered) 867 kgdb_arch_late(); 868 kdb_init(KDB_INIT_FULL); 869 } 870 871 static int 872 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x) 873 { 874 /* 875 * Take the following action on reboot notify depending on value: 876 * 1 == Enter debugger 877 * 0 == [the default] detatch debug client 878 * -1 == Do nothing... and use this until the board resets 879 */ 880 switch (kgdbreboot) { 881 case 1: 882 kgdb_breakpoint(); 883 case -1: 884 goto done; 885 } 886 if (!dbg_kdb_mode) 887 gdbstub_exit(code); 888 done: 889 return NOTIFY_DONE; 890 } 891 892 static struct notifier_block dbg_reboot_notifier = { 893 .notifier_call = dbg_notify_reboot, 894 .next = NULL, 895 .priority = INT_MAX, 896 }; 897 898 static void kgdb_register_callbacks(void) 899 { 900 if (!kgdb_io_module_registered) { 901 kgdb_io_module_registered = 1; 902 kgdb_arch_init(); 903 if (!dbg_is_early) 904 kgdb_arch_late(); 905 register_module_notifier(&dbg_module_load_nb); 906 register_reboot_notifier(&dbg_reboot_notifier); 907 atomic_notifier_chain_register(&panic_notifier_list, 908 &kgdb_panic_event_nb); 909 #ifdef CONFIG_MAGIC_SYSRQ 910 register_sysrq_key('g', &sysrq_dbg_op); 911 #endif 912 if (kgdb_use_con && !kgdb_con_registered) { 913 register_console(&kgdbcons); 914 kgdb_con_registered = 1; 915 } 916 } 917 } 918 919 static void kgdb_unregister_callbacks(void) 920 { 921 /* 922 * When this routine is called KGDB should unregister from the 923 * panic handler and clean up, making sure it is not handling any 924 * break exceptions at the time. 925 */ 926 if (kgdb_io_module_registered) { 927 kgdb_io_module_registered = 0; 928 unregister_reboot_notifier(&dbg_reboot_notifier); 929 unregister_module_notifier(&dbg_module_load_nb); 930 atomic_notifier_chain_unregister(&panic_notifier_list, 931 &kgdb_panic_event_nb); 932 kgdb_arch_exit(); 933 #ifdef CONFIG_MAGIC_SYSRQ 934 unregister_sysrq_key('g', &sysrq_dbg_op); 935 #endif 936 if (kgdb_con_registered) { 937 unregister_console(&kgdbcons); 938 kgdb_con_registered = 0; 939 } 940 } 941 } 942 943 /* 944 * There are times a tasklet needs to be used vs a compiled in 945 * break point so as to cause an exception outside a kgdb I/O module, 946 * such as is the case with kgdboe, where calling a breakpoint in the 947 * I/O driver itself would be fatal. 948 */ 949 static void kgdb_tasklet_bpt(unsigned long ing) 950 { 951 kgdb_breakpoint(); 952 atomic_set(&kgdb_break_tasklet_var, 0); 953 } 954 955 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0); 956 957 void kgdb_schedule_breakpoint(void) 958 { 959 if (atomic_read(&kgdb_break_tasklet_var) || 960 atomic_read(&kgdb_active) != -1 || 961 atomic_read(&kgdb_setting_breakpoint)) 962 return; 963 atomic_inc(&kgdb_break_tasklet_var); 964 tasklet_schedule(&kgdb_tasklet_breakpoint); 965 } 966 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint); 967 968 static void kgdb_initial_breakpoint(void) 969 { 970 kgdb_break_asap = 0; 971 972 pr_crit("Waiting for connection from remote gdb...\n"); 973 kgdb_breakpoint(); 974 } 975 976 /** 977 * kgdb_register_io_module - register KGDB IO module 978 * @new_dbg_io_ops: the io ops vector 979 * 980 * Register it with the KGDB core. 981 */ 982 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) 983 { 984 int err; 985 986 spin_lock(&kgdb_registration_lock); 987 988 if (dbg_io_ops) { 989 spin_unlock(&kgdb_registration_lock); 990 991 pr_err("Another I/O driver is already registered with KGDB\n"); 992 return -EBUSY; 993 } 994 995 if (new_dbg_io_ops->init) { 996 err = new_dbg_io_ops->init(); 997 if (err) { 998 spin_unlock(&kgdb_registration_lock); 999 return err; 1000 } 1001 } 1002 1003 dbg_io_ops = new_dbg_io_ops; 1004 1005 spin_unlock(&kgdb_registration_lock); 1006 1007 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name); 1008 1009 /* Arm KGDB now. */ 1010 kgdb_register_callbacks(); 1011 1012 if (kgdb_break_asap) 1013 kgdb_initial_breakpoint(); 1014 1015 return 0; 1016 } 1017 EXPORT_SYMBOL_GPL(kgdb_register_io_module); 1018 1019 /** 1020 * kkgdb_unregister_io_module - unregister KGDB IO module 1021 * @old_dbg_io_ops: the io ops vector 1022 * 1023 * Unregister it with the KGDB core. 1024 */ 1025 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops) 1026 { 1027 BUG_ON(kgdb_connected); 1028 1029 /* 1030 * KGDB is no longer able to communicate out, so 1031 * unregister our callbacks and reset state. 1032 */ 1033 kgdb_unregister_callbacks(); 1034 1035 spin_lock(&kgdb_registration_lock); 1036 1037 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops); 1038 dbg_io_ops = NULL; 1039 1040 spin_unlock(&kgdb_registration_lock); 1041 1042 pr_info("Unregistered I/O driver %s, debugger disabled\n", 1043 old_dbg_io_ops->name); 1044 } 1045 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module); 1046 1047 int dbg_io_get_char(void) 1048 { 1049 int ret = dbg_io_ops->read_char(); 1050 if (ret == NO_POLL_CHAR) 1051 return -1; 1052 if (!dbg_kdb_mode) 1053 return ret; 1054 if (ret == 127) 1055 return 8; 1056 return ret; 1057 } 1058 1059 /** 1060 * kgdb_breakpoint - generate breakpoint exception 1061 * 1062 * This function will generate a breakpoint exception. It is used at the 1063 * beginning of a program to sync up with a debugger and can be used 1064 * otherwise as a quick means to stop program execution and "break" into 1065 * the debugger. 1066 */ 1067 noinline void kgdb_breakpoint(void) 1068 { 1069 atomic_inc(&kgdb_setting_breakpoint); 1070 wmb(); /* Sync point before breakpoint */ 1071 arch_kgdb_breakpoint(); 1072 wmb(); /* Sync point after breakpoint */ 1073 atomic_dec(&kgdb_setting_breakpoint); 1074 } 1075 EXPORT_SYMBOL_GPL(kgdb_breakpoint); 1076 1077 static int __init opt_kgdb_wait(char *str) 1078 { 1079 kgdb_break_asap = 1; 1080 1081 kdb_init(KDB_INIT_EARLY); 1082 if (kgdb_io_module_registered) 1083 kgdb_initial_breakpoint(); 1084 1085 return 0; 1086 } 1087 1088 early_param("kgdbwait", opt_kgdb_wait); 1089