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/nmi.h> 53 #include <linux/pid.h> 54 #include <linux/smp.h> 55 #include <linux/mm.h> 56 #include <linux/vmacache.h> 57 #include <linux/rcupdate.h> 58 #include <linux/irq.h> 59 60 #include <asm/cacheflush.h> 61 #include <asm/byteorder.h> 62 #include <linux/atomic.h> 63 64 #include "debug_core.h" 65 66 static int kgdb_break_asap; 67 68 struct debuggerinfo_struct kgdb_info[NR_CPUS]; 69 70 /** 71 * kgdb_connected - Is a host GDB connected to us? 72 */ 73 int kgdb_connected; 74 EXPORT_SYMBOL_GPL(kgdb_connected); 75 76 /* All the KGDB handlers are installed */ 77 int kgdb_io_module_registered; 78 79 /* Guard for recursive entry */ 80 static int exception_level; 81 82 struct kgdb_io *dbg_io_ops; 83 static DEFINE_SPINLOCK(kgdb_registration_lock); 84 85 /* Action for the reboot notifiter, a global allow kdb to change it */ 86 static int kgdbreboot; 87 /* kgdb console driver is loaded */ 88 static int kgdb_con_registered; 89 /* determine if kgdb console output should be used */ 90 static int kgdb_use_con; 91 /* Flag for alternate operations for early debugging */ 92 bool dbg_is_early = true; 93 /* Next cpu to become the master debug core */ 94 int dbg_switch_cpu; 95 96 /* Use kdb or gdbserver mode */ 97 int dbg_kdb_mode = 1; 98 99 static int __init opt_kgdb_con(char *str) 100 { 101 kgdb_use_con = 1; 102 return 0; 103 } 104 105 early_param("kgdbcon", opt_kgdb_con); 106 107 module_param(kgdb_use_con, int, 0644); 108 module_param(kgdbreboot, int, 0644); 109 110 /* 111 * Holds information about breakpoints in a kernel. These breakpoints are 112 * added and removed by gdb. 113 */ 114 static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = { 115 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED } 116 }; 117 118 /* 119 * The CPU# of the active CPU, or -1 if none: 120 */ 121 atomic_t kgdb_active = ATOMIC_INIT(-1); 122 EXPORT_SYMBOL_GPL(kgdb_active); 123 static DEFINE_RAW_SPINLOCK(dbg_master_lock); 124 static DEFINE_RAW_SPINLOCK(dbg_slave_lock); 125 126 /* 127 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early 128 * bootup code (which might not have percpu set up yet): 129 */ 130 static atomic_t masters_in_kgdb; 131 static atomic_t slaves_in_kgdb; 132 static atomic_t kgdb_break_tasklet_var; 133 atomic_t kgdb_setting_breakpoint; 134 135 struct task_struct *kgdb_usethread; 136 struct task_struct *kgdb_contthread; 137 138 int kgdb_single_step; 139 static pid_t kgdb_sstep_pid; 140 141 /* to keep track of the CPU which is doing the single stepping*/ 142 atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1); 143 144 /* 145 * If you are debugging a problem where roundup (the collection of 146 * all other CPUs) is a problem [this should be extremely rare], 147 * then use the nokgdbroundup option to avoid roundup. In that case 148 * the other CPUs might interfere with your debugging context, so 149 * use this with care: 150 */ 151 static int kgdb_do_roundup = 1; 152 153 static int __init opt_nokgdbroundup(char *str) 154 { 155 kgdb_do_roundup = 0; 156 157 return 0; 158 } 159 160 early_param("nokgdbroundup", opt_nokgdbroundup); 161 162 /* 163 * Finally, some KGDB code :-) 164 */ 165 166 /* 167 * Weak aliases for breakpoint management, 168 * can be overriden by architectures when needed: 169 */ 170 int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) 171 { 172 int err; 173 174 err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr, 175 BREAK_INSTR_SIZE); 176 if (err) 177 return err; 178 err = probe_kernel_write((char *)bpt->bpt_addr, 179 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE); 180 return err; 181 } 182 183 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt) 184 { 185 return probe_kernel_write((char *)bpt->bpt_addr, 186 (char *)bpt->saved_instr, BREAK_INSTR_SIZE); 187 } 188 189 int __weak kgdb_validate_break_address(unsigned long addr) 190 { 191 struct kgdb_bkpt tmp; 192 int err; 193 /* Validate setting the breakpoint and then removing it. If the 194 * remove fails, the kernel needs to emit a bad message because we 195 * are deep trouble not being able to put things back the way we 196 * found them. 197 */ 198 tmp.bpt_addr = addr; 199 err = kgdb_arch_set_breakpoint(&tmp); 200 if (err) 201 return err; 202 err = kgdb_arch_remove_breakpoint(&tmp); 203 if (err) 204 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n", 205 addr); 206 return err; 207 } 208 209 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs) 210 { 211 return instruction_pointer(regs); 212 } 213 214 int __weak kgdb_arch_init(void) 215 { 216 return 0; 217 } 218 219 int __weak kgdb_skipexception(int exception, struct pt_regs *regs) 220 { 221 return 0; 222 } 223 224 #ifdef CONFIG_SMP 225 226 /* 227 * Default (weak) implementation for kgdb_roundup_cpus 228 */ 229 230 static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd); 231 232 void __weak kgdb_call_nmi_hook(void *ignored) 233 { 234 /* 235 * NOTE: get_irq_regs() is supposed to get the registers from 236 * before the IPI interrupt happened and so is supposed to 237 * show where the processor was. In some situations it's 238 * possible we might be called without an IPI, so it might be 239 * safer to figure out how to make kgdb_breakpoint() work 240 * properly here. 241 */ 242 kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs()); 243 } 244 245 void __weak kgdb_roundup_cpus(void) 246 { 247 call_single_data_t *csd; 248 int this_cpu = raw_smp_processor_id(); 249 int cpu; 250 int ret; 251 252 for_each_online_cpu(cpu) { 253 /* No need to roundup ourselves */ 254 if (cpu == this_cpu) 255 continue; 256 257 csd = &per_cpu(kgdb_roundup_csd, cpu); 258 259 /* 260 * If it didn't round up last time, don't try again 261 * since smp_call_function_single_async() will block. 262 * 263 * If rounding_up is false then we know that the 264 * previous call must have at least started and that 265 * means smp_call_function_single_async() won't block. 266 */ 267 if (kgdb_info[cpu].rounding_up) 268 continue; 269 kgdb_info[cpu].rounding_up = true; 270 271 csd->func = kgdb_call_nmi_hook; 272 ret = smp_call_function_single_async(cpu, csd); 273 if (ret) 274 kgdb_info[cpu].rounding_up = false; 275 } 276 } 277 278 #endif 279 280 /* 281 * Some architectures need cache flushes when we set/clear a 282 * breakpoint: 283 */ 284 static void kgdb_flush_swbreak_addr(unsigned long addr) 285 { 286 if (!CACHE_FLUSH_IS_SAFE) 287 return; 288 289 if (current->mm) { 290 int i; 291 292 for (i = 0; i < VMACACHE_SIZE; i++) { 293 if (!current->vmacache.vmas[i]) 294 continue; 295 flush_cache_range(current->vmacache.vmas[i], 296 addr, addr + BREAK_INSTR_SIZE); 297 } 298 } 299 300 /* Force flush instruction cache if it was outside the mm */ 301 flush_icache_range(addr, addr + BREAK_INSTR_SIZE); 302 } 303 304 /* 305 * SW breakpoint management: 306 */ 307 int dbg_activate_sw_breakpoints(void) 308 { 309 int error; 310 int ret = 0; 311 int i; 312 313 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 314 if (kgdb_break[i].state != BP_SET) 315 continue; 316 317 error = kgdb_arch_set_breakpoint(&kgdb_break[i]); 318 if (error) { 319 ret = error; 320 pr_info("BP install failed: %lx\n", 321 kgdb_break[i].bpt_addr); 322 continue; 323 } 324 325 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); 326 kgdb_break[i].state = BP_ACTIVE; 327 } 328 return ret; 329 } 330 331 int dbg_set_sw_break(unsigned long addr) 332 { 333 int err = kgdb_validate_break_address(addr); 334 int breakno = -1; 335 int i; 336 337 if (err) 338 return err; 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 return -EEXIST; 344 } 345 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 346 if (kgdb_break[i].state == BP_REMOVED && 347 kgdb_break[i].bpt_addr == addr) { 348 breakno = i; 349 break; 350 } 351 } 352 353 if (breakno == -1) { 354 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 355 if (kgdb_break[i].state == BP_UNDEFINED) { 356 breakno = i; 357 break; 358 } 359 } 360 } 361 362 if (breakno == -1) 363 return -E2BIG; 364 365 kgdb_break[breakno].state = BP_SET; 366 kgdb_break[breakno].type = BP_BREAKPOINT; 367 kgdb_break[breakno].bpt_addr = addr; 368 369 return 0; 370 } 371 372 int dbg_deactivate_sw_breakpoints(void) 373 { 374 int error; 375 int ret = 0; 376 int i; 377 378 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 379 if (kgdb_break[i].state != BP_ACTIVE) 380 continue; 381 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); 382 if (error) { 383 pr_info("BP remove failed: %lx\n", 384 kgdb_break[i].bpt_addr); 385 ret = error; 386 } 387 388 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); 389 kgdb_break[i].state = BP_SET; 390 } 391 return ret; 392 } 393 394 int dbg_remove_sw_break(unsigned long addr) 395 { 396 int i; 397 398 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 399 if ((kgdb_break[i].state == BP_SET) && 400 (kgdb_break[i].bpt_addr == addr)) { 401 kgdb_break[i].state = BP_REMOVED; 402 return 0; 403 } 404 } 405 return -ENOENT; 406 } 407 408 int kgdb_isremovedbreak(unsigned long addr) 409 { 410 int i; 411 412 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 413 if ((kgdb_break[i].state == BP_REMOVED) && 414 (kgdb_break[i].bpt_addr == addr)) 415 return 1; 416 } 417 return 0; 418 } 419 420 int dbg_remove_all_break(void) 421 { 422 int error; 423 int i; 424 425 /* Clear memory breakpoints. */ 426 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 427 if (kgdb_break[i].state != BP_ACTIVE) 428 goto setundefined; 429 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); 430 if (error) 431 pr_err("breakpoint remove failed: %lx\n", 432 kgdb_break[i].bpt_addr); 433 setundefined: 434 kgdb_break[i].state = BP_UNDEFINED; 435 } 436 437 /* Clear hardware breakpoints. */ 438 if (arch_kgdb_ops.remove_all_hw_break) 439 arch_kgdb_ops.remove_all_hw_break(); 440 441 return 0; 442 } 443 444 /* 445 * Return true if there is a valid kgdb I/O module. Also if no 446 * debugger is attached a message can be printed to the console about 447 * waiting for the debugger to attach. 448 * 449 * The print_wait argument is only to be true when called from inside 450 * the core kgdb_handle_exception, because it will wait for the 451 * debugger to attach. 452 */ 453 static int kgdb_io_ready(int print_wait) 454 { 455 if (!dbg_io_ops) 456 return 0; 457 if (kgdb_connected) 458 return 1; 459 if (atomic_read(&kgdb_setting_breakpoint)) 460 return 1; 461 if (print_wait) { 462 #ifdef CONFIG_KGDB_KDB 463 if (!dbg_kdb_mode) 464 pr_crit("waiting... or $3#33 for KDB\n"); 465 #else 466 pr_crit("Waiting for remote debugger\n"); 467 #endif 468 } 469 return 1; 470 } 471 472 static int kgdb_reenter_check(struct kgdb_state *ks) 473 { 474 unsigned long addr; 475 476 if (atomic_read(&kgdb_active) != raw_smp_processor_id()) 477 return 0; 478 479 /* Panic on recursive debugger calls: */ 480 exception_level++; 481 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs); 482 dbg_deactivate_sw_breakpoints(); 483 484 /* 485 * If the break point removed ok at the place exception 486 * occurred, try to recover and print a warning to the end 487 * user because the user planted a breakpoint in a place that 488 * KGDB needs in order to function. 489 */ 490 if (dbg_remove_sw_break(addr) == 0) { 491 exception_level = 0; 492 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 493 dbg_activate_sw_breakpoints(); 494 pr_crit("re-enter error: breakpoint removed %lx\n", addr); 495 WARN_ON_ONCE(1); 496 497 return 1; 498 } 499 dbg_remove_all_break(); 500 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 501 502 if (exception_level > 1) { 503 dump_stack(); 504 panic("Recursive entry to debugger"); 505 } 506 507 pr_crit("re-enter exception: ALL breakpoints killed\n"); 508 #ifdef CONFIG_KGDB_KDB 509 /* Allow kdb to debug itself one level */ 510 return 0; 511 #endif 512 dump_stack(); 513 panic("Recursive entry to debugger"); 514 515 return 1; 516 } 517 518 static void dbg_touch_watchdogs(void) 519 { 520 touch_softlockup_watchdog_sync(); 521 clocksource_touch_watchdog(); 522 rcu_cpu_stall_reset(); 523 } 524 525 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, 526 int exception_state) 527 { 528 unsigned long flags; 529 int sstep_tries = 100; 530 int error; 531 int cpu; 532 int trace_on = 0; 533 int online_cpus = num_online_cpus(); 534 u64 time_left; 535 536 kgdb_info[ks->cpu].enter_kgdb++; 537 kgdb_info[ks->cpu].exception_state |= exception_state; 538 539 if (exception_state == DCPU_WANT_MASTER) 540 atomic_inc(&masters_in_kgdb); 541 else 542 atomic_inc(&slaves_in_kgdb); 543 544 if (arch_kgdb_ops.disable_hw_break) 545 arch_kgdb_ops.disable_hw_break(regs); 546 547 acquirelock: 548 /* 549 * Interrupts will be restored by the 'trap return' code, except when 550 * single stepping. 551 */ 552 local_irq_save(flags); 553 554 cpu = ks->cpu; 555 kgdb_info[cpu].debuggerinfo = regs; 556 kgdb_info[cpu].task = current; 557 kgdb_info[cpu].ret_state = 0; 558 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT; 559 560 /* Make sure the above info reaches the primary CPU */ 561 smp_mb(); 562 563 if (exception_level == 1) { 564 if (raw_spin_trylock(&dbg_master_lock)) 565 atomic_xchg(&kgdb_active, cpu); 566 goto cpu_master_loop; 567 } 568 569 /* 570 * CPU will loop if it is a slave or request to become a kgdb 571 * master cpu and acquire the kgdb_active lock: 572 */ 573 while (1) { 574 cpu_loop: 575 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) { 576 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER; 577 goto cpu_master_loop; 578 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) { 579 if (raw_spin_trylock(&dbg_master_lock)) { 580 atomic_xchg(&kgdb_active, cpu); 581 break; 582 } 583 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) { 584 if (!raw_spin_is_locked(&dbg_slave_lock)) 585 goto return_normal; 586 } else { 587 return_normal: 588 /* Return to normal operation by executing any 589 * hw breakpoint fixup. 590 */ 591 if (arch_kgdb_ops.correct_hw_break) 592 arch_kgdb_ops.correct_hw_break(); 593 if (trace_on) 594 tracing_on(); 595 kgdb_info[cpu].debuggerinfo = NULL; 596 kgdb_info[cpu].task = NULL; 597 kgdb_info[cpu].exception_state &= 598 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 599 kgdb_info[cpu].enter_kgdb--; 600 smp_mb__before_atomic(); 601 atomic_dec(&slaves_in_kgdb); 602 dbg_touch_watchdogs(); 603 local_irq_restore(flags); 604 return 0; 605 } 606 cpu_relax(); 607 } 608 609 /* 610 * For single stepping, try to only enter on the processor 611 * that was single stepping. To guard against a deadlock, the 612 * kernel will only try for the value of sstep_tries before 613 * giving up and continuing on. 614 */ 615 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 && 616 (kgdb_info[cpu].task && 617 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) { 618 atomic_set(&kgdb_active, -1); 619 raw_spin_unlock(&dbg_master_lock); 620 dbg_touch_watchdogs(); 621 local_irq_restore(flags); 622 623 goto acquirelock; 624 } 625 626 if (!kgdb_io_ready(1)) { 627 kgdb_info[cpu].ret_state = 1; 628 goto kgdb_restore; /* No I/O connection, resume the system */ 629 } 630 631 /* 632 * Don't enter if we have hit a removed breakpoint. 633 */ 634 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs)) 635 goto kgdb_restore; 636 637 /* Call the I/O driver's pre_exception routine */ 638 if (dbg_io_ops->pre_exception) 639 dbg_io_ops->pre_exception(); 640 641 /* 642 * Get the passive CPU lock which will hold all the non-primary 643 * CPU in a spin state while the debugger is active 644 */ 645 if (!kgdb_single_step) 646 raw_spin_lock(&dbg_slave_lock); 647 648 #ifdef CONFIG_SMP 649 /* If send_ready set, slaves are already waiting */ 650 if (ks->send_ready) 651 atomic_set(ks->send_ready, 1); 652 653 /* Signal the other CPUs to enter kgdb_wait() */ 654 else if ((!kgdb_single_step) && kgdb_do_roundup) 655 kgdb_roundup_cpus(); 656 #endif 657 658 /* 659 * Wait for the other CPUs to be notified and be waiting for us: 660 */ 661 time_left = MSEC_PER_SEC; 662 while (kgdb_do_roundup && --time_left && 663 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) != 664 online_cpus) 665 udelay(1000); 666 if (!time_left) 667 pr_crit("Timed out waiting for secondary CPUs.\n"); 668 669 /* 670 * At this point the primary processor is completely 671 * in the debugger and all secondary CPUs are quiescent 672 */ 673 dbg_deactivate_sw_breakpoints(); 674 kgdb_single_step = 0; 675 kgdb_contthread = current; 676 exception_level = 0; 677 trace_on = tracing_is_on(); 678 if (trace_on) 679 tracing_off(); 680 681 while (1) { 682 cpu_master_loop: 683 if (dbg_kdb_mode) { 684 kgdb_connected = 1; 685 error = kdb_stub(ks); 686 if (error == -1) 687 continue; 688 kgdb_connected = 0; 689 } else { 690 error = gdb_serial_stub(ks); 691 } 692 693 if (error == DBG_PASS_EVENT) { 694 dbg_kdb_mode = !dbg_kdb_mode; 695 } else if (error == DBG_SWITCH_CPU_EVENT) { 696 kgdb_info[dbg_switch_cpu].exception_state |= 697 DCPU_NEXT_MASTER; 698 goto cpu_loop; 699 } else { 700 kgdb_info[cpu].ret_state = error; 701 break; 702 } 703 } 704 705 /* Call the I/O driver's post_exception routine */ 706 if (dbg_io_ops->post_exception) 707 dbg_io_ops->post_exception(); 708 709 if (!kgdb_single_step) { 710 raw_spin_unlock(&dbg_slave_lock); 711 /* Wait till all the CPUs have quit from the debugger. */ 712 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb)) 713 cpu_relax(); 714 } 715 716 kgdb_restore: 717 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) { 718 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step); 719 if (kgdb_info[sstep_cpu].task) 720 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid; 721 else 722 kgdb_sstep_pid = 0; 723 } 724 if (arch_kgdb_ops.correct_hw_break) 725 arch_kgdb_ops.correct_hw_break(); 726 if (trace_on) 727 tracing_on(); 728 729 kgdb_info[cpu].debuggerinfo = NULL; 730 kgdb_info[cpu].task = NULL; 731 kgdb_info[cpu].exception_state &= 732 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 733 kgdb_info[cpu].enter_kgdb--; 734 smp_mb__before_atomic(); 735 atomic_dec(&masters_in_kgdb); 736 /* Free kgdb_active */ 737 atomic_set(&kgdb_active, -1); 738 raw_spin_unlock(&dbg_master_lock); 739 dbg_touch_watchdogs(); 740 local_irq_restore(flags); 741 742 return kgdb_info[cpu].ret_state; 743 } 744 745 /* 746 * kgdb_handle_exception() - main entry point from a kernel exception 747 * 748 * Locking hierarchy: 749 * interface locks, if any (begin_session) 750 * kgdb lock (kgdb_active) 751 */ 752 int 753 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 754 { 755 struct kgdb_state kgdb_var; 756 struct kgdb_state *ks = &kgdb_var; 757 int ret = 0; 758 759 if (arch_kgdb_ops.enable_nmi) 760 arch_kgdb_ops.enable_nmi(0); 761 /* 762 * Avoid entering the debugger if we were triggered due to an oops 763 * but panic_timeout indicates the system should automatically 764 * reboot on panic. We don't want to get stuck waiting for input 765 * on such systems, especially if its "just" an oops. 766 */ 767 if (signo != SIGTRAP && panic_timeout) 768 return 1; 769 770 memset(ks, 0, sizeof(struct kgdb_state)); 771 ks->cpu = raw_smp_processor_id(); 772 ks->ex_vector = evector; 773 ks->signo = signo; 774 ks->err_code = ecode; 775 ks->linux_regs = regs; 776 777 if (kgdb_reenter_check(ks)) 778 goto out; /* Ouch, double exception ! */ 779 if (kgdb_info[ks->cpu].enter_kgdb != 0) 780 goto out; 781 782 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 783 out: 784 if (arch_kgdb_ops.enable_nmi) 785 arch_kgdb_ops.enable_nmi(1); 786 return ret; 787 } 788 789 /* 790 * GDB places a breakpoint at this function to know dynamically 791 * loaded objects. It's not defined static so that only one instance with this 792 * name exists in the kernel. 793 */ 794 795 static int module_event(struct notifier_block *self, unsigned long val, 796 void *data) 797 { 798 return 0; 799 } 800 801 static struct notifier_block dbg_module_load_nb = { 802 .notifier_call = module_event, 803 }; 804 805 int kgdb_nmicallback(int cpu, void *regs) 806 { 807 #ifdef CONFIG_SMP 808 struct kgdb_state kgdb_var; 809 struct kgdb_state *ks = &kgdb_var; 810 811 kgdb_info[cpu].rounding_up = false; 812 813 memset(ks, 0, sizeof(struct kgdb_state)); 814 ks->cpu = cpu; 815 ks->linux_regs = regs; 816 817 if (kgdb_info[ks->cpu].enter_kgdb == 0 && 818 raw_spin_is_locked(&dbg_master_lock)) { 819 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE); 820 return 0; 821 } 822 #endif 823 return 1; 824 } 825 826 int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code, 827 atomic_t *send_ready) 828 { 829 #ifdef CONFIG_SMP 830 if (!kgdb_io_ready(0) || !send_ready) 831 return 1; 832 833 if (kgdb_info[cpu].enter_kgdb == 0) { 834 struct kgdb_state kgdb_var; 835 struct kgdb_state *ks = &kgdb_var; 836 837 memset(ks, 0, sizeof(struct kgdb_state)); 838 ks->cpu = cpu; 839 ks->ex_vector = trapnr; 840 ks->signo = SIGTRAP; 841 ks->err_code = err_code; 842 ks->linux_regs = regs; 843 ks->send_ready = send_ready; 844 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 845 return 0; 846 } 847 #endif 848 return 1; 849 } 850 851 static void kgdb_console_write(struct console *co, const char *s, 852 unsigned count) 853 { 854 unsigned long flags; 855 856 /* If we're debugging, or KGDB has not connected, don't try 857 * and print. */ 858 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode) 859 return; 860 861 local_irq_save(flags); 862 gdbstub_msg_write(s, count); 863 local_irq_restore(flags); 864 } 865 866 static struct console kgdbcons = { 867 .name = "kgdb", 868 .write = kgdb_console_write, 869 .flags = CON_PRINTBUFFER | CON_ENABLED, 870 .index = -1, 871 }; 872 873 #ifdef CONFIG_MAGIC_SYSRQ 874 static void sysrq_handle_dbg(int key) 875 { 876 if (!dbg_io_ops) { 877 pr_crit("ERROR: No KGDB I/O module available\n"); 878 return; 879 } 880 if (!kgdb_connected) { 881 #ifdef CONFIG_KGDB_KDB 882 if (!dbg_kdb_mode) 883 pr_crit("KGDB or $3#33 for KDB\n"); 884 #else 885 pr_crit("Entering KGDB\n"); 886 #endif 887 } 888 889 kgdb_breakpoint(); 890 } 891 892 static struct sysrq_key_op sysrq_dbg_op = { 893 .handler = sysrq_handle_dbg, 894 .help_msg = "debug(g)", 895 .action_msg = "DEBUG", 896 }; 897 #endif 898 899 static int kgdb_panic_event(struct notifier_block *self, 900 unsigned long val, 901 void *data) 902 { 903 /* 904 * Avoid entering the debugger if we were triggered due to a panic 905 * We don't want to get stuck waiting for input from user in such case. 906 * panic_timeout indicates the system should automatically 907 * reboot on panic. 908 */ 909 if (panic_timeout) 910 return NOTIFY_DONE; 911 912 if (dbg_kdb_mode) 913 kdb_printf("PANIC: %s\n", (char *)data); 914 kgdb_breakpoint(); 915 return NOTIFY_DONE; 916 } 917 918 static struct notifier_block kgdb_panic_event_nb = { 919 .notifier_call = kgdb_panic_event, 920 .priority = INT_MAX, 921 }; 922 923 void __weak kgdb_arch_late(void) 924 { 925 } 926 927 void __init dbg_late_init(void) 928 { 929 dbg_is_early = false; 930 if (kgdb_io_module_registered) 931 kgdb_arch_late(); 932 kdb_init(KDB_INIT_FULL); 933 } 934 935 static int 936 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x) 937 { 938 /* 939 * Take the following action on reboot notify depending on value: 940 * 1 == Enter debugger 941 * 0 == [the default] detatch debug client 942 * -1 == Do nothing... and use this until the board resets 943 */ 944 switch (kgdbreboot) { 945 case 1: 946 kgdb_breakpoint(); 947 case -1: 948 goto done; 949 } 950 if (!dbg_kdb_mode) 951 gdbstub_exit(code); 952 done: 953 return NOTIFY_DONE; 954 } 955 956 static struct notifier_block dbg_reboot_notifier = { 957 .notifier_call = dbg_notify_reboot, 958 .next = NULL, 959 .priority = INT_MAX, 960 }; 961 962 static void kgdb_register_callbacks(void) 963 { 964 if (!kgdb_io_module_registered) { 965 kgdb_io_module_registered = 1; 966 kgdb_arch_init(); 967 if (!dbg_is_early) 968 kgdb_arch_late(); 969 register_module_notifier(&dbg_module_load_nb); 970 register_reboot_notifier(&dbg_reboot_notifier); 971 atomic_notifier_chain_register(&panic_notifier_list, 972 &kgdb_panic_event_nb); 973 #ifdef CONFIG_MAGIC_SYSRQ 974 register_sysrq_key('g', &sysrq_dbg_op); 975 #endif 976 if (kgdb_use_con && !kgdb_con_registered) { 977 register_console(&kgdbcons); 978 kgdb_con_registered = 1; 979 } 980 } 981 } 982 983 static void kgdb_unregister_callbacks(void) 984 { 985 /* 986 * When this routine is called KGDB should unregister from the 987 * panic handler and clean up, making sure it is not handling any 988 * break exceptions at the time. 989 */ 990 if (kgdb_io_module_registered) { 991 kgdb_io_module_registered = 0; 992 unregister_reboot_notifier(&dbg_reboot_notifier); 993 unregister_module_notifier(&dbg_module_load_nb); 994 atomic_notifier_chain_unregister(&panic_notifier_list, 995 &kgdb_panic_event_nb); 996 kgdb_arch_exit(); 997 #ifdef CONFIG_MAGIC_SYSRQ 998 unregister_sysrq_key('g', &sysrq_dbg_op); 999 #endif 1000 if (kgdb_con_registered) { 1001 unregister_console(&kgdbcons); 1002 kgdb_con_registered = 0; 1003 } 1004 } 1005 } 1006 1007 /* 1008 * There are times a tasklet needs to be used vs a compiled in 1009 * break point so as to cause an exception outside a kgdb I/O module, 1010 * such as is the case with kgdboe, where calling a breakpoint in the 1011 * I/O driver itself would be fatal. 1012 */ 1013 static void kgdb_tasklet_bpt(unsigned long ing) 1014 { 1015 kgdb_breakpoint(); 1016 atomic_set(&kgdb_break_tasklet_var, 0); 1017 } 1018 1019 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0); 1020 1021 void kgdb_schedule_breakpoint(void) 1022 { 1023 if (atomic_read(&kgdb_break_tasklet_var) || 1024 atomic_read(&kgdb_active) != -1 || 1025 atomic_read(&kgdb_setting_breakpoint)) 1026 return; 1027 atomic_inc(&kgdb_break_tasklet_var); 1028 tasklet_schedule(&kgdb_tasklet_breakpoint); 1029 } 1030 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint); 1031 1032 static void kgdb_initial_breakpoint(void) 1033 { 1034 kgdb_break_asap = 0; 1035 1036 pr_crit("Waiting for connection from remote gdb...\n"); 1037 kgdb_breakpoint(); 1038 } 1039 1040 /** 1041 * kgdb_register_io_module - register KGDB IO module 1042 * @new_dbg_io_ops: the io ops vector 1043 * 1044 * Register it with the KGDB core. 1045 */ 1046 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) 1047 { 1048 int err; 1049 1050 spin_lock(&kgdb_registration_lock); 1051 1052 if (dbg_io_ops) { 1053 spin_unlock(&kgdb_registration_lock); 1054 1055 pr_err("Another I/O driver is already registered with KGDB\n"); 1056 return -EBUSY; 1057 } 1058 1059 if (new_dbg_io_ops->init) { 1060 err = new_dbg_io_ops->init(); 1061 if (err) { 1062 spin_unlock(&kgdb_registration_lock); 1063 return err; 1064 } 1065 } 1066 1067 dbg_io_ops = new_dbg_io_ops; 1068 1069 spin_unlock(&kgdb_registration_lock); 1070 1071 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name); 1072 1073 /* Arm KGDB now. */ 1074 kgdb_register_callbacks(); 1075 1076 if (kgdb_break_asap) 1077 kgdb_initial_breakpoint(); 1078 1079 return 0; 1080 } 1081 EXPORT_SYMBOL_GPL(kgdb_register_io_module); 1082 1083 /** 1084 * kkgdb_unregister_io_module - unregister KGDB IO module 1085 * @old_dbg_io_ops: the io ops vector 1086 * 1087 * Unregister it with the KGDB core. 1088 */ 1089 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops) 1090 { 1091 BUG_ON(kgdb_connected); 1092 1093 /* 1094 * KGDB is no longer able to communicate out, so 1095 * unregister our callbacks and reset state. 1096 */ 1097 kgdb_unregister_callbacks(); 1098 1099 spin_lock(&kgdb_registration_lock); 1100 1101 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops); 1102 dbg_io_ops = NULL; 1103 1104 spin_unlock(&kgdb_registration_lock); 1105 1106 pr_info("Unregistered I/O driver %s, debugger disabled\n", 1107 old_dbg_io_ops->name); 1108 } 1109 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module); 1110 1111 int dbg_io_get_char(void) 1112 { 1113 int ret = dbg_io_ops->read_char(); 1114 if (ret == NO_POLL_CHAR) 1115 return -1; 1116 if (!dbg_kdb_mode) 1117 return ret; 1118 if (ret == 127) 1119 return 8; 1120 return ret; 1121 } 1122 1123 /** 1124 * kgdb_breakpoint - generate breakpoint exception 1125 * 1126 * This function will generate a breakpoint exception. It is used at the 1127 * beginning of a program to sync up with a debugger and can be used 1128 * otherwise as a quick means to stop program execution and "break" into 1129 * the debugger. 1130 */ 1131 noinline void kgdb_breakpoint(void) 1132 { 1133 atomic_inc(&kgdb_setting_breakpoint); 1134 wmb(); /* Sync point before breakpoint */ 1135 arch_kgdb_breakpoint(); 1136 wmb(); /* Sync point after breakpoint */ 1137 atomic_dec(&kgdb_setting_breakpoint); 1138 } 1139 EXPORT_SYMBOL_GPL(kgdb_breakpoint); 1140 1141 static int __init opt_kgdb_wait(char *str) 1142 { 1143 kgdb_break_asap = 1; 1144 1145 kdb_init(KDB_INIT_EARLY); 1146 if (kgdb_io_module_registered) 1147 kgdb_initial_breakpoint(); 1148 1149 return 0; 1150 } 1151 1152 early_param("kgdbwait", opt_kgdb_wait); 1153