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 #ifdef CONFIG_KGDB_KDB 445 void kdb_dump_stack_on_cpu(int cpu) 446 { 447 if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) { 448 dump_stack(); 449 return; 450 } 451 452 if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) { 453 kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n", 454 cpu); 455 return; 456 } 457 458 /* 459 * In general, architectures don't support dumping the stack of a 460 * "running" process that's not the current one. From the point of 461 * view of the Linux, kernel processes that are looping in the kgdb 462 * slave loop are still "running". There's also no API (that actually 463 * works across all architectures) that can do a stack crawl based 464 * on registers passed as a parameter. 465 * 466 * Solve this conundrum by asking slave CPUs to do the backtrace 467 * themselves. 468 */ 469 kgdb_info[cpu].exception_state |= DCPU_WANT_BT; 470 while (kgdb_info[cpu].exception_state & DCPU_WANT_BT) 471 cpu_relax(); 472 } 473 #endif 474 475 /* 476 * Return true if there is a valid kgdb I/O module. Also if no 477 * debugger is attached a message can be printed to the console about 478 * waiting for the debugger to attach. 479 * 480 * The print_wait argument is only to be true when called from inside 481 * the core kgdb_handle_exception, because it will wait for the 482 * debugger to attach. 483 */ 484 static int kgdb_io_ready(int print_wait) 485 { 486 if (!dbg_io_ops) 487 return 0; 488 if (kgdb_connected) 489 return 1; 490 if (atomic_read(&kgdb_setting_breakpoint)) 491 return 1; 492 if (print_wait) { 493 #ifdef CONFIG_KGDB_KDB 494 if (!dbg_kdb_mode) 495 pr_crit("waiting... or $3#33 for KDB\n"); 496 #else 497 pr_crit("Waiting for remote debugger\n"); 498 #endif 499 } 500 return 1; 501 } 502 503 static int kgdb_reenter_check(struct kgdb_state *ks) 504 { 505 unsigned long addr; 506 507 if (atomic_read(&kgdb_active) != raw_smp_processor_id()) 508 return 0; 509 510 /* Panic on recursive debugger calls: */ 511 exception_level++; 512 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs); 513 dbg_deactivate_sw_breakpoints(); 514 515 /* 516 * If the break point removed ok at the place exception 517 * occurred, try to recover and print a warning to the end 518 * user because the user planted a breakpoint in a place that 519 * KGDB needs in order to function. 520 */ 521 if (dbg_remove_sw_break(addr) == 0) { 522 exception_level = 0; 523 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 524 dbg_activate_sw_breakpoints(); 525 pr_crit("re-enter error: breakpoint removed %lx\n", addr); 526 WARN_ON_ONCE(1); 527 528 return 1; 529 } 530 dbg_remove_all_break(); 531 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 532 533 if (exception_level > 1) { 534 dump_stack(); 535 panic("Recursive entry to debugger"); 536 } 537 538 pr_crit("re-enter exception: ALL breakpoints killed\n"); 539 #ifdef CONFIG_KGDB_KDB 540 /* Allow kdb to debug itself one level */ 541 return 0; 542 #endif 543 dump_stack(); 544 panic("Recursive entry to debugger"); 545 546 return 1; 547 } 548 549 static void dbg_touch_watchdogs(void) 550 { 551 touch_softlockup_watchdog_sync(); 552 clocksource_touch_watchdog(); 553 rcu_cpu_stall_reset(); 554 } 555 556 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, 557 int exception_state) 558 { 559 unsigned long flags; 560 int sstep_tries = 100; 561 int error; 562 int cpu; 563 int trace_on = 0; 564 int online_cpus = num_online_cpus(); 565 u64 time_left; 566 567 kgdb_info[ks->cpu].enter_kgdb++; 568 kgdb_info[ks->cpu].exception_state |= exception_state; 569 570 if (exception_state == DCPU_WANT_MASTER) 571 atomic_inc(&masters_in_kgdb); 572 else 573 atomic_inc(&slaves_in_kgdb); 574 575 if (arch_kgdb_ops.disable_hw_break) 576 arch_kgdb_ops.disable_hw_break(regs); 577 578 acquirelock: 579 /* 580 * Interrupts will be restored by the 'trap return' code, except when 581 * single stepping. 582 */ 583 local_irq_save(flags); 584 585 cpu = ks->cpu; 586 kgdb_info[cpu].debuggerinfo = regs; 587 kgdb_info[cpu].task = current; 588 kgdb_info[cpu].ret_state = 0; 589 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT; 590 591 /* Make sure the above info reaches the primary CPU */ 592 smp_mb(); 593 594 if (exception_level == 1) { 595 if (raw_spin_trylock(&dbg_master_lock)) 596 atomic_xchg(&kgdb_active, cpu); 597 goto cpu_master_loop; 598 } 599 600 /* 601 * CPU will loop if it is a slave or request to become a kgdb 602 * master cpu and acquire the kgdb_active lock: 603 */ 604 while (1) { 605 cpu_loop: 606 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) { 607 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER; 608 goto cpu_master_loop; 609 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) { 610 if (raw_spin_trylock(&dbg_master_lock)) { 611 atomic_xchg(&kgdb_active, cpu); 612 break; 613 } 614 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) { 615 dump_stack(); 616 kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT; 617 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) { 618 if (!raw_spin_is_locked(&dbg_slave_lock)) 619 goto return_normal; 620 } else { 621 return_normal: 622 /* Return to normal operation by executing any 623 * hw breakpoint fixup. 624 */ 625 if (arch_kgdb_ops.correct_hw_break) 626 arch_kgdb_ops.correct_hw_break(); 627 if (trace_on) 628 tracing_on(); 629 kgdb_info[cpu].debuggerinfo = NULL; 630 kgdb_info[cpu].task = NULL; 631 kgdb_info[cpu].exception_state &= 632 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 633 kgdb_info[cpu].enter_kgdb--; 634 smp_mb__before_atomic(); 635 atomic_dec(&slaves_in_kgdb); 636 dbg_touch_watchdogs(); 637 local_irq_restore(flags); 638 return 0; 639 } 640 cpu_relax(); 641 } 642 643 /* 644 * For single stepping, try to only enter on the processor 645 * that was single stepping. To guard against a deadlock, the 646 * kernel will only try for the value of sstep_tries before 647 * giving up and continuing on. 648 */ 649 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 && 650 (kgdb_info[cpu].task && 651 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) { 652 atomic_set(&kgdb_active, -1); 653 raw_spin_unlock(&dbg_master_lock); 654 dbg_touch_watchdogs(); 655 local_irq_restore(flags); 656 657 goto acquirelock; 658 } 659 660 if (!kgdb_io_ready(1)) { 661 kgdb_info[cpu].ret_state = 1; 662 goto kgdb_restore; /* No I/O connection, resume the system */ 663 } 664 665 /* 666 * Don't enter if we have hit a removed breakpoint. 667 */ 668 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs)) 669 goto kgdb_restore; 670 671 /* Call the I/O driver's pre_exception routine */ 672 if (dbg_io_ops->pre_exception) 673 dbg_io_ops->pre_exception(); 674 675 /* 676 * Get the passive CPU lock which will hold all the non-primary 677 * CPU in a spin state while the debugger is active 678 */ 679 if (!kgdb_single_step) 680 raw_spin_lock(&dbg_slave_lock); 681 682 #ifdef CONFIG_SMP 683 /* If send_ready set, slaves are already waiting */ 684 if (ks->send_ready) 685 atomic_set(ks->send_ready, 1); 686 687 /* Signal the other CPUs to enter kgdb_wait() */ 688 else if ((!kgdb_single_step) && kgdb_do_roundup) 689 kgdb_roundup_cpus(); 690 #endif 691 692 /* 693 * Wait for the other CPUs to be notified and be waiting for us: 694 */ 695 time_left = MSEC_PER_SEC; 696 while (kgdb_do_roundup && --time_left && 697 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) != 698 online_cpus) 699 udelay(1000); 700 if (!time_left) 701 pr_crit("Timed out waiting for secondary CPUs.\n"); 702 703 /* 704 * At this point the primary processor is completely 705 * in the debugger and all secondary CPUs are quiescent 706 */ 707 dbg_deactivate_sw_breakpoints(); 708 kgdb_single_step = 0; 709 kgdb_contthread = current; 710 exception_level = 0; 711 trace_on = tracing_is_on(); 712 if (trace_on) 713 tracing_off(); 714 715 while (1) { 716 cpu_master_loop: 717 if (dbg_kdb_mode) { 718 kgdb_connected = 1; 719 error = kdb_stub(ks); 720 if (error == -1) 721 continue; 722 kgdb_connected = 0; 723 } else { 724 error = gdb_serial_stub(ks); 725 } 726 727 if (error == DBG_PASS_EVENT) { 728 dbg_kdb_mode = !dbg_kdb_mode; 729 } else if (error == DBG_SWITCH_CPU_EVENT) { 730 kgdb_info[dbg_switch_cpu].exception_state |= 731 DCPU_NEXT_MASTER; 732 goto cpu_loop; 733 } else { 734 kgdb_info[cpu].ret_state = error; 735 break; 736 } 737 } 738 739 /* Call the I/O driver's post_exception routine */ 740 if (dbg_io_ops->post_exception) 741 dbg_io_ops->post_exception(); 742 743 if (!kgdb_single_step) { 744 raw_spin_unlock(&dbg_slave_lock); 745 /* Wait till all the CPUs have quit from the debugger. */ 746 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb)) 747 cpu_relax(); 748 } 749 750 kgdb_restore: 751 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) { 752 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step); 753 if (kgdb_info[sstep_cpu].task) 754 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid; 755 else 756 kgdb_sstep_pid = 0; 757 } 758 if (arch_kgdb_ops.correct_hw_break) 759 arch_kgdb_ops.correct_hw_break(); 760 if (trace_on) 761 tracing_on(); 762 763 kgdb_info[cpu].debuggerinfo = NULL; 764 kgdb_info[cpu].task = NULL; 765 kgdb_info[cpu].exception_state &= 766 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 767 kgdb_info[cpu].enter_kgdb--; 768 smp_mb__before_atomic(); 769 atomic_dec(&masters_in_kgdb); 770 /* Free kgdb_active */ 771 atomic_set(&kgdb_active, -1); 772 raw_spin_unlock(&dbg_master_lock); 773 dbg_touch_watchdogs(); 774 local_irq_restore(flags); 775 776 return kgdb_info[cpu].ret_state; 777 } 778 779 /* 780 * kgdb_handle_exception() - main entry point from a kernel exception 781 * 782 * Locking hierarchy: 783 * interface locks, if any (begin_session) 784 * kgdb lock (kgdb_active) 785 */ 786 int 787 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 788 { 789 struct kgdb_state kgdb_var; 790 struct kgdb_state *ks = &kgdb_var; 791 int ret = 0; 792 793 if (arch_kgdb_ops.enable_nmi) 794 arch_kgdb_ops.enable_nmi(0); 795 /* 796 * Avoid entering the debugger if we were triggered due to an oops 797 * but panic_timeout indicates the system should automatically 798 * reboot on panic. We don't want to get stuck waiting for input 799 * on such systems, especially if its "just" an oops. 800 */ 801 if (signo != SIGTRAP && panic_timeout) 802 return 1; 803 804 memset(ks, 0, sizeof(struct kgdb_state)); 805 ks->cpu = raw_smp_processor_id(); 806 ks->ex_vector = evector; 807 ks->signo = signo; 808 ks->err_code = ecode; 809 ks->linux_regs = regs; 810 811 if (kgdb_reenter_check(ks)) 812 goto out; /* Ouch, double exception ! */ 813 if (kgdb_info[ks->cpu].enter_kgdb != 0) 814 goto out; 815 816 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 817 out: 818 if (arch_kgdb_ops.enable_nmi) 819 arch_kgdb_ops.enable_nmi(1); 820 return ret; 821 } 822 823 /* 824 * GDB places a breakpoint at this function to know dynamically loaded objects. 825 */ 826 static int module_event(struct notifier_block *self, unsigned long val, 827 void *data) 828 { 829 return 0; 830 } 831 832 static struct notifier_block dbg_module_load_nb = { 833 .notifier_call = module_event, 834 }; 835 836 int kgdb_nmicallback(int cpu, void *regs) 837 { 838 #ifdef CONFIG_SMP 839 struct kgdb_state kgdb_var; 840 struct kgdb_state *ks = &kgdb_var; 841 842 kgdb_info[cpu].rounding_up = false; 843 844 memset(ks, 0, sizeof(struct kgdb_state)); 845 ks->cpu = cpu; 846 ks->linux_regs = regs; 847 848 if (kgdb_info[ks->cpu].enter_kgdb == 0 && 849 raw_spin_is_locked(&dbg_master_lock)) { 850 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE); 851 return 0; 852 } 853 #endif 854 return 1; 855 } 856 857 int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code, 858 atomic_t *send_ready) 859 { 860 #ifdef CONFIG_SMP 861 if (!kgdb_io_ready(0) || !send_ready) 862 return 1; 863 864 if (kgdb_info[cpu].enter_kgdb == 0) { 865 struct kgdb_state kgdb_var; 866 struct kgdb_state *ks = &kgdb_var; 867 868 memset(ks, 0, sizeof(struct kgdb_state)); 869 ks->cpu = cpu; 870 ks->ex_vector = trapnr; 871 ks->signo = SIGTRAP; 872 ks->err_code = err_code; 873 ks->linux_regs = regs; 874 ks->send_ready = send_ready; 875 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 876 return 0; 877 } 878 #endif 879 return 1; 880 } 881 882 static void kgdb_console_write(struct console *co, const char *s, 883 unsigned count) 884 { 885 unsigned long flags; 886 887 /* If we're debugging, or KGDB has not connected, don't try 888 * and print. */ 889 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode) 890 return; 891 892 local_irq_save(flags); 893 gdbstub_msg_write(s, count); 894 local_irq_restore(flags); 895 } 896 897 static struct console kgdbcons = { 898 .name = "kgdb", 899 .write = kgdb_console_write, 900 .flags = CON_PRINTBUFFER | CON_ENABLED, 901 .index = -1, 902 }; 903 904 #ifdef CONFIG_MAGIC_SYSRQ 905 static void sysrq_handle_dbg(int key) 906 { 907 if (!dbg_io_ops) { 908 pr_crit("ERROR: No KGDB I/O module available\n"); 909 return; 910 } 911 if (!kgdb_connected) { 912 #ifdef CONFIG_KGDB_KDB 913 if (!dbg_kdb_mode) 914 pr_crit("KGDB or $3#33 for KDB\n"); 915 #else 916 pr_crit("Entering KGDB\n"); 917 #endif 918 } 919 920 kgdb_breakpoint(); 921 } 922 923 static struct sysrq_key_op sysrq_dbg_op = { 924 .handler = sysrq_handle_dbg, 925 .help_msg = "debug(g)", 926 .action_msg = "DEBUG", 927 }; 928 #endif 929 930 void kgdb_panic(const char *msg) 931 { 932 if (!kgdb_io_module_registered) 933 return; 934 935 /* 936 * We don't want to get stuck waiting for input from user if 937 * "panic_timeout" indicates the system should automatically 938 * reboot on panic. 939 */ 940 if (panic_timeout) 941 return; 942 943 if (dbg_kdb_mode) 944 kdb_printf("PANIC: %s\n", msg); 945 946 kgdb_breakpoint(); 947 } 948 949 void __weak kgdb_arch_late(void) 950 { 951 } 952 953 void __init dbg_late_init(void) 954 { 955 dbg_is_early = false; 956 if (kgdb_io_module_registered) 957 kgdb_arch_late(); 958 kdb_init(KDB_INIT_FULL); 959 } 960 961 static int 962 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x) 963 { 964 /* 965 * Take the following action on reboot notify depending on value: 966 * 1 == Enter debugger 967 * 0 == [the default] detatch debug client 968 * -1 == Do nothing... and use this until the board resets 969 */ 970 switch (kgdbreboot) { 971 case 1: 972 kgdb_breakpoint(); 973 case -1: 974 goto done; 975 } 976 if (!dbg_kdb_mode) 977 gdbstub_exit(code); 978 done: 979 return NOTIFY_DONE; 980 } 981 982 static struct notifier_block dbg_reboot_notifier = { 983 .notifier_call = dbg_notify_reboot, 984 .next = NULL, 985 .priority = INT_MAX, 986 }; 987 988 static void kgdb_register_callbacks(void) 989 { 990 if (!kgdb_io_module_registered) { 991 kgdb_io_module_registered = 1; 992 kgdb_arch_init(); 993 if (!dbg_is_early) 994 kgdb_arch_late(); 995 register_module_notifier(&dbg_module_load_nb); 996 register_reboot_notifier(&dbg_reboot_notifier); 997 #ifdef CONFIG_MAGIC_SYSRQ 998 register_sysrq_key('g', &sysrq_dbg_op); 999 #endif 1000 if (kgdb_use_con && !kgdb_con_registered) { 1001 register_console(&kgdbcons); 1002 kgdb_con_registered = 1; 1003 } 1004 } 1005 } 1006 1007 static void kgdb_unregister_callbacks(void) 1008 { 1009 /* 1010 * When this routine is called KGDB should unregister from 1011 * handlers and clean up, making sure it is not handling any 1012 * break exceptions at the time. 1013 */ 1014 if (kgdb_io_module_registered) { 1015 kgdb_io_module_registered = 0; 1016 unregister_reboot_notifier(&dbg_reboot_notifier); 1017 unregister_module_notifier(&dbg_module_load_nb); 1018 kgdb_arch_exit(); 1019 #ifdef CONFIG_MAGIC_SYSRQ 1020 unregister_sysrq_key('g', &sysrq_dbg_op); 1021 #endif 1022 if (kgdb_con_registered) { 1023 unregister_console(&kgdbcons); 1024 kgdb_con_registered = 0; 1025 } 1026 } 1027 } 1028 1029 /* 1030 * There are times a tasklet needs to be used vs a compiled in 1031 * break point so as to cause an exception outside a kgdb I/O module, 1032 * such as is the case with kgdboe, where calling a breakpoint in the 1033 * I/O driver itself would be fatal. 1034 */ 1035 static void kgdb_tasklet_bpt(unsigned long ing) 1036 { 1037 kgdb_breakpoint(); 1038 atomic_set(&kgdb_break_tasklet_var, 0); 1039 } 1040 1041 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0); 1042 1043 void kgdb_schedule_breakpoint(void) 1044 { 1045 if (atomic_read(&kgdb_break_tasklet_var) || 1046 atomic_read(&kgdb_active) != -1 || 1047 atomic_read(&kgdb_setting_breakpoint)) 1048 return; 1049 atomic_inc(&kgdb_break_tasklet_var); 1050 tasklet_schedule(&kgdb_tasklet_breakpoint); 1051 } 1052 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint); 1053 1054 static void kgdb_initial_breakpoint(void) 1055 { 1056 kgdb_break_asap = 0; 1057 1058 pr_crit("Waiting for connection from remote gdb...\n"); 1059 kgdb_breakpoint(); 1060 } 1061 1062 /** 1063 * kgdb_register_io_module - register KGDB IO module 1064 * @new_dbg_io_ops: the io ops vector 1065 * 1066 * Register it with the KGDB core. 1067 */ 1068 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) 1069 { 1070 int err; 1071 1072 spin_lock(&kgdb_registration_lock); 1073 1074 if (dbg_io_ops) { 1075 spin_unlock(&kgdb_registration_lock); 1076 1077 pr_err("Another I/O driver is already registered with KGDB\n"); 1078 return -EBUSY; 1079 } 1080 1081 if (new_dbg_io_ops->init) { 1082 err = new_dbg_io_ops->init(); 1083 if (err) { 1084 spin_unlock(&kgdb_registration_lock); 1085 return err; 1086 } 1087 } 1088 1089 dbg_io_ops = new_dbg_io_ops; 1090 1091 spin_unlock(&kgdb_registration_lock); 1092 1093 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name); 1094 1095 /* Arm KGDB now. */ 1096 kgdb_register_callbacks(); 1097 1098 if (kgdb_break_asap) 1099 kgdb_initial_breakpoint(); 1100 1101 return 0; 1102 } 1103 EXPORT_SYMBOL_GPL(kgdb_register_io_module); 1104 1105 /** 1106 * kkgdb_unregister_io_module - unregister KGDB IO module 1107 * @old_dbg_io_ops: the io ops vector 1108 * 1109 * Unregister it with the KGDB core. 1110 */ 1111 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops) 1112 { 1113 BUG_ON(kgdb_connected); 1114 1115 /* 1116 * KGDB is no longer able to communicate out, so 1117 * unregister our callbacks and reset state. 1118 */ 1119 kgdb_unregister_callbacks(); 1120 1121 spin_lock(&kgdb_registration_lock); 1122 1123 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops); 1124 dbg_io_ops = NULL; 1125 1126 spin_unlock(&kgdb_registration_lock); 1127 1128 pr_info("Unregistered I/O driver %s, debugger disabled\n", 1129 old_dbg_io_ops->name); 1130 } 1131 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module); 1132 1133 int dbg_io_get_char(void) 1134 { 1135 int ret = dbg_io_ops->read_char(); 1136 if (ret == NO_POLL_CHAR) 1137 return -1; 1138 if (!dbg_kdb_mode) 1139 return ret; 1140 if (ret == 127) 1141 return 8; 1142 return ret; 1143 } 1144 1145 /** 1146 * kgdb_breakpoint - generate breakpoint exception 1147 * 1148 * This function will generate a breakpoint exception. It is used at the 1149 * beginning of a program to sync up with a debugger and can be used 1150 * otherwise as a quick means to stop program execution and "break" into 1151 * the debugger. 1152 */ 1153 noinline void kgdb_breakpoint(void) 1154 { 1155 atomic_inc(&kgdb_setting_breakpoint); 1156 wmb(); /* Sync point before breakpoint */ 1157 arch_kgdb_breakpoint(); 1158 wmb(); /* Sync point after breakpoint */ 1159 atomic_dec(&kgdb_setting_breakpoint); 1160 } 1161 EXPORT_SYMBOL_GPL(kgdb_breakpoint); 1162 1163 static int __init opt_kgdb_wait(char *str) 1164 { 1165 kgdb_break_asap = 1; 1166 1167 kdb_init(KDB_INIT_EARLY); 1168 if (kgdb_io_module_registered) 1169 kgdb_initial_breakpoint(); 1170 1171 return 0; 1172 } 1173 1174 early_param("kgdbwait", opt_kgdb_wait); 1175