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 /* kgdb_connected - Is a host GDB connected to us? */ 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 = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr, 173 BREAK_INSTR_SIZE); 174 if (err) 175 return err; 176 err = copy_to_kernel_nofault((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 copy_to_kernel_nofault((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 #ifdef CONFIG_SMP 223 224 /* 225 * Default (weak) implementation for kgdb_roundup_cpus 226 */ 227 228 static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd); 229 230 void __weak kgdb_call_nmi_hook(void *ignored) 231 { 232 /* 233 * NOTE: get_irq_regs() is supposed to get the registers from 234 * before the IPI interrupt happened and so is supposed to 235 * show where the processor was. In some situations it's 236 * possible we might be called without an IPI, so it might be 237 * safer to figure out how to make kgdb_breakpoint() work 238 * properly here. 239 */ 240 kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs()); 241 } 242 243 void __weak kgdb_roundup_cpus(void) 244 { 245 call_single_data_t *csd; 246 int this_cpu = raw_smp_processor_id(); 247 int cpu; 248 int ret; 249 250 for_each_online_cpu(cpu) { 251 /* No need to roundup ourselves */ 252 if (cpu == this_cpu) 253 continue; 254 255 csd = &per_cpu(kgdb_roundup_csd, cpu); 256 257 /* 258 * If it didn't round up last time, don't try again 259 * since smp_call_function_single_async() will block. 260 * 261 * If rounding_up is false then we know that the 262 * previous call must have at least started and that 263 * means smp_call_function_single_async() won't block. 264 */ 265 if (kgdb_info[cpu].rounding_up) 266 continue; 267 kgdb_info[cpu].rounding_up = true; 268 269 csd->func = kgdb_call_nmi_hook; 270 ret = smp_call_function_single_async(cpu, csd); 271 if (ret) 272 kgdb_info[cpu].rounding_up = false; 273 } 274 } 275 276 #endif 277 278 /* 279 * Some architectures need cache flushes when we set/clear a 280 * breakpoint: 281 */ 282 static void kgdb_flush_swbreak_addr(unsigned long addr) 283 { 284 if (!CACHE_FLUSH_IS_SAFE) 285 return; 286 287 if (current->mm) { 288 int i; 289 290 for (i = 0; i < VMACACHE_SIZE; i++) { 291 if (!current->vmacache.vmas[i]) 292 continue; 293 flush_cache_range(current->vmacache.vmas[i], 294 addr, addr + BREAK_INSTR_SIZE); 295 } 296 } 297 298 /* Force flush instruction cache if it was outside the mm */ 299 flush_icache_range(addr, addr + BREAK_INSTR_SIZE); 300 } 301 302 /* 303 * SW breakpoint management: 304 */ 305 int dbg_activate_sw_breakpoints(void) 306 { 307 int error; 308 int ret = 0; 309 int i; 310 311 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 312 if (kgdb_break[i].state != BP_SET) 313 continue; 314 315 error = kgdb_arch_set_breakpoint(&kgdb_break[i]); 316 if (error) { 317 ret = error; 318 pr_info("BP install failed: %lx\n", 319 kgdb_break[i].bpt_addr); 320 continue; 321 } 322 323 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); 324 kgdb_break[i].state = BP_ACTIVE; 325 } 326 return ret; 327 } 328 329 int dbg_set_sw_break(unsigned long addr) 330 { 331 int err = kgdb_validate_break_address(addr); 332 int breakno = -1; 333 int i; 334 335 if (err) 336 return err; 337 338 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 339 if ((kgdb_break[i].state == BP_SET) && 340 (kgdb_break[i].bpt_addr == addr)) 341 return -EEXIST; 342 } 343 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 344 if (kgdb_break[i].state == BP_REMOVED && 345 kgdb_break[i].bpt_addr == addr) { 346 breakno = i; 347 break; 348 } 349 } 350 351 if (breakno == -1) { 352 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 353 if (kgdb_break[i].state == BP_UNDEFINED) { 354 breakno = i; 355 break; 356 } 357 } 358 } 359 360 if (breakno == -1) 361 return -E2BIG; 362 363 kgdb_break[breakno].state = BP_SET; 364 kgdb_break[breakno].type = BP_BREAKPOINT; 365 kgdb_break[breakno].bpt_addr = addr; 366 367 return 0; 368 } 369 370 int dbg_deactivate_sw_breakpoints(void) 371 { 372 int error; 373 int ret = 0; 374 int i; 375 376 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 377 if (kgdb_break[i].state != BP_ACTIVE) 378 continue; 379 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); 380 if (error) { 381 pr_info("BP remove failed: %lx\n", 382 kgdb_break[i].bpt_addr); 383 ret = error; 384 } 385 386 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); 387 kgdb_break[i].state = BP_SET; 388 } 389 return ret; 390 } 391 392 int dbg_remove_sw_break(unsigned long addr) 393 { 394 int i; 395 396 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 397 if ((kgdb_break[i].state == BP_SET) && 398 (kgdb_break[i].bpt_addr == addr)) { 399 kgdb_break[i].state = BP_REMOVED; 400 return 0; 401 } 402 } 403 return -ENOENT; 404 } 405 406 int kgdb_isremovedbreak(unsigned long addr) 407 { 408 int i; 409 410 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 411 if ((kgdb_break[i].state == BP_REMOVED) && 412 (kgdb_break[i].bpt_addr == addr)) 413 return 1; 414 } 415 return 0; 416 } 417 418 int kgdb_has_hit_break(unsigned long addr) 419 { 420 int i; 421 422 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 423 if (kgdb_break[i].state == BP_ACTIVE && 424 kgdb_break[i].bpt_addr == addr) 425 return 1; 426 } 427 return 0; 428 } 429 430 int dbg_remove_all_break(void) 431 { 432 int error; 433 int i; 434 435 /* Clear memory breakpoints. */ 436 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 437 if (kgdb_break[i].state != BP_ACTIVE) 438 goto setundefined; 439 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); 440 if (error) 441 pr_err("breakpoint remove failed: %lx\n", 442 kgdb_break[i].bpt_addr); 443 setundefined: 444 kgdb_break[i].state = BP_UNDEFINED; 445 } 446 447 /* Clear hardware breakpoints. */ 448 if (arch_kgdb_ops.remove_all_hw_break) 449 arch_kgdb_ops.remove_all_hw_break(); 450 451 return 0; 452 } 453 454 #ifdef CONFIG_KGDB_KDB 455 void kdb_dump_stack_on_cpu(int cpu) 456 { 457 if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) { 458 dump_stack(); 459 return; 460 } 461 462 if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) { 463 kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n", 464 cpu); 465 return; 466 } 467 468 /* 469 * In general, architectures don't support dumping the stack of a 470 * "running" process that's not the current one. From the point of 471 * view of the Linux, kernel processes that are looping in the kgdb 472 * slave loop are still "running". There's also no API (that actually 473 * works across all architectures) that can do a stack crawl based 474 * on registers passed as a parameter. 475 * 476 * Solve this conundrum by asking slave CPUs to do the backtrace 477 * themselves. 478 */ 479 kgdb_info[cpu].exception_state |= DCPU_WANT_BT; 480 while (kgdb_info[cpu].exception_state & DCPU_WANT_BT) 481 cpu_relax(); 482 } 483 #endif 484 485 /* 486 * Return true if there is a valid kgdb I/O module. Also if no 487 * debugger is attached a message can be printed to the console about 488 * waiting for the debugger to attach. 489 * 490 * The print_wait argument is only to be true when called from inside 491 * the core kgdb_handle_exception, because it will wait for the 492 * debugger to attach. 493 */ 494 static int kgdb_io_ready(int print_wait) 495 { 496 if (!dbg_io_ops) 497 return 0; 498 if (kgdb_connected) 499 return 1; 500 if (atomic_read(&kgdb_setting_breakpoint)) 501 return 1; 502 if (print_wait) { 503 #ifdef CONFIG_KGDB_KDB 504 if (!dbg_kdb_mode) 505 pr_crit("waiting... or $3#33 for KDB\n"); 506 #else 507 pr_crit("Waiting for remote debugger\n"); 508 #endif 509 } 510 return 1; 511 } 512 513 static int kgdb_reenter_check(struct kgdb_state *ks) 514 { 515 unsigned long addr; 516 517 if (atomic_read(&kgdb_active) != raw_smp_processor_id()) 518 return 0; 519 520 /* Panic on recursive debugger calls: */ 521 exception_level++; 522 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs); 523 dbg_deactivate_sw_breakpoints(); 524 525 /* 526 * If the break point removed ok at the place exception 527 * occurred, try to recover and print a warning to the end 528 * user because the user planted a breakpoint in a place that 529 * KGDB needs in order to function. 530 */ 531 if (dbg_remove_sw_break(addr) == 0) { 532 exception_level = 0; 533 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 534 dbg_activate_sw_breakpoints(); 535 pr_crit("re-enter error: breakpoint removed %lx\n", addr); 536 WARN_ON_ONCE(1); 537 538 return 1; 539 } 540 dbg_remove_all_break(); 541 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 542 543 if (exception_level > 1) { 544 dump_stack(); 545 kgdb_io_module_registered = false; 546 panic("Recursive entry to debugger"); 547 } 548 549 pr_crit("re-enter exception: ALL breakpoints killed\n"); 550 #ifdef CONFIG_KGDB_KDB 551 /* Allow kdb to debug itself one level */ 552 return 0; 553 #endif 554 dump_stack(); 555 panic("Recursive entry to debugger"); 556 557 return 1; 558 } 559 560 static void dbg_touch_watchdogs(void) 561 { 562 touch_softlockup_watchdog_sync(); 563 clocksource_touch_watchdog(); 564 rcu_cpu_stall_reset(); 565 } 566 567 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, 568 int exception_state) 569 { 570 unsigned long flags; 571 int sstep_tries = 100; 572 int error; 573 int cpu; 574 int trace_on = 0; 575 int online_cpus = num_online_cpus(); 576 u64 time_left; 577 578 kgdb_info[ks->cpu].enter_kgdb++; 579 kgdb_info[ks->cpu].exception_state |= exception_state; 580 581 if (exception_state == DCPU_WANT_MASTER) 582 atomic_inc(&masters_in_kgdb); 583 else 584 atomic_inc(&slaves_in_kgdb); 585 586 if (arch_kgdb_ops.disable_hw_break) 587 arch_kgdb_ops.disable_hw_break(regs); 588 589 acquirelock: 590 rcu_read_lock(); 591 /* 592 * Interrupts will be restored by the 'trap return' code, except when 593 * single stepping. 594 */ 595 local_irq_save(flags); 596 597 cpu = ks->cpu; 598 kgdb_info[cpu].debuggerinfo = regs; 599 kgdb_info[cpu].task = current; 600 kgdb_info[cpu].ret_state = 0; 601 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT; 602 603 /* Make sure the above info reaches the primary CPU */ 604 smp_mb(); 605 606 if (exception_level == 1) { 607 if (raw_spin_trylock(&dbg_master_lock)) 608 atomic_xchg(&kgdb_active, cpu); 609 goto cpu_master_loop; 610 } 611 612 /* 613 * CPU will loop if it is a slave or request to become a kgdb 614 * master cpu and acquire the kgdb_active lock: 615 */ 616 while (1) { 617 cpu_loop: 618 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) { 619 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER; 620 goto cpu_master_loop; 621 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) { 622 if (raw_spin_trylock(&dbg_master_lock)) { 623 atomic_xchg(&kgdb_active, cpu); 624 break; 625 } 626 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) { 627 dump_stack(); 628 kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT; 629 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) { 630 if (!raw_spin_is_locked(&dbg_slave_lock)) 631 goto return_normal; 632 } else { 633 return_normal: 634 /* Return to normal operation by executing any 635 * hw breakpoint fixup. 636 */ 637 if (arch_kgdb_ops.correct_hw_break) 638 arch_kgdb_ops.correct_hw_break(); 639 if (trace_on) 640 tracing_on(); 641 kgdb_info[cpu].debuggerinfo = NULL; 642 kgdb_info[cpu].task = NULL; 643 kgdb_info[cpu].exception_state &= 644 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 645 kgdb_info[cpu].enter_kgdb--; 646 smp_mb__before_atomic(); 647 atomic_dec(&slaves_in_kgdb); 648 dbg_touch_watchdogs(); 649 local_irq_restore(flags); 650 rcu_read_unlock(); 651 return 0; 652 } 653 cpu_relax(); 654 } 655 656 /* 657 * For single stepping, try to only enter on the processor 658 * that was single stepping. To guard against a deadlock, the 659 * kernel will only try for the value of sstep_tries before 660 * giving up and continuing on. 661 */ 662 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 && 663 (kgdb_info[cpu].task && 664 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) { 665 atomic_set(&kgdb_active, -1); 666 raw_spin_unlock(&dbg_master_lock); 667 dbg_touch_watchdogs(); 668 local_irq_restore(flags); 669 rcu_read_unlock(); 670 671 goto acquirelock; 672 } 673 674 if (!kgdb_io_ready(1)) { 675 kgdb_info[cpu].ret_state = 1; 676 goto kgdb_restore; /* No I/O connection, resume the system */ 677 } 678 679 /* 680 * Don't enter if we have hit a removed breakpoint. 681 */ 682 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs)) 683 goto kgdb_restore; 684 685 atomic_inc(&ignore_console_lock_warning); 686 687 /* Call the I/O driver's pre_exception routine */ 688 if (dbg_io_ops->pre_exception) 689 dbg_io_ops->pre_exception(); 690 691 /* 692 * Get the passive CPU lock which will hold all the non-primary 693 * CPU in a spin state while the debugger is active 694 */ 695 if (!kgdb_single_step) 696 raw_spin_lock(&dbg_slave_lock); 697 698 #ifdef CONFIG_SMP 699 /* If send_ready set, slaves are already waiting */ 700 if (ks->send_ready) 701 atomic_set(ks->send_ready, 1); 702 703 /* Signal the other CPUs to enter kgdb_wait() */ 704 else if ((!kgdb_single_step) && kgdb_do_roundup) 705 kgdb_roundup_cpus(); 706 #endif 707 708 /* 709 * Wait for the other CPUs to be notified and be waiting for us: 710 */ 711 time_left = MSEC_PER_SEC; 712 while (kgdb_do_roundup && --time_left && 713 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) != 714 online_cpus) 715 udelay(1000); 716 if (!time_left) 717 pr_crit("Timed out waiting for secondary CPUs.\n"); 718 719 /* 720 * At this point the primary processor is completely 721 * in the debugger and all secondary CPUs are quiescent 722 */ 723 dbg_deactivate_sw_breakpoints(); 724 kgdb_single_step = 0; 725 kgdb_contthread = current; 726 exception_level = 0; 727 trace_on = tracing_is_on(); 728 if (trace_on) 729 tracing_off(); 730 731 while (1) { 732 cpu_master_loop: 733 if (dbg_kdb_mode) { 734 kgdb_connected = 1; 735 error = kdb_stub(ks); 736 if (error == -1) 737 continue; 738 kgdb_connected = 0; 739 } else { 740 error = gdb_serial_stub(ks); 741 } 742 743 if (error == DBG_PASS_EVENT) { 744 dbg_kdb_mode = !dbg_kdb_mode; 745 } else if (error == DBG_SWITCH_CPU_EVENT) { 746 kgdb_info[dbg_switch_cpu].exception_state |= 747 DCPU_NEXT_MASTER; 748 goto cpu_loop; 749 } else { 750 kgdb_info[cpu].ret_state = error; 751 break; 752 } 753 } 754 755 /* Call the I/O driver's post_exception routine */ 756 if (dbg_io_ops->post_exception) 757 dbg_io_ops->post_exception(); 758 759 atomic_dec(&ignore_console_lock_warning); 760 761 if (!kgdb_single_step) { 762 raw_spin_unlock(&dbg_slave_lock); 763 /* Wait till all the CPUs have quit from the debugger. */ 764 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb)) 765 cpu_relax(); 766 } 767 768 kgdb_restore: 769 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) { 770 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step); 771 if (kgdb_info[sstep_cpu].task) 772 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid; 773 else 774 kgdb_sstep_pid = 0; 775 } 776 if (arch_kgdb_ops.correct_hw_break) 777 arch_kgdb_ops.correct_hw_break(); 778 if (trace_on) 779 tracing_on(); 780 781 kgdb_info[cpu].debuggerinfo = NULL; 782 kgdb_info[cpu].task = NULL; 783 kgdb_info[cpu].exception_state &= 784 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 785 kgdb_info[cpu].enter_kgdb--; 786 smp_mb__before_atomic(); 787 atomic_dec(&masters_in_kgdb); 788 /* Free kgdb_active */ 789 atomic_set(&kgdb_active, -1); 790 raw_spin_unlock(&dbg_master_lock); 791 dbg_touch_watchdogs(); 792 local_irq_restore(flags); 793 rcu_read_unlock(); 794 795 return kgdb_info[cpu].ret_state; 796 } 797 798 /* 799 * kgdb_handle_exception() - main entry point from a kernel exception 800 * 801 * Locking hierarchy: 802 * interface locks, if any (begin_session) 803 * kgdb lock (kgdb_active) 804 */ 805 int 806 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 807 { 808 struct kgdb_state kgdb_var; 809 struct kgdb_state *ks = &kgdb_var; 810 int ret = 0; 811 812 if (arch_kgdb_ops.enable_nmi) 813 arch_kgdb_ops.enable_nmi(0); 814 /* 815 * Avoid entering the debugger if we were triggered due to an oops 816 * but panic_timeout indicates the system should automatically 817 * reboot on panic. We don't want to get stuck waiting for input 818 * on such systems, especially if its "just" an oops. 819 */ 820 if (signo != SIGTRAP && panic_timeout) 821 return 1; 822 823 memset(ks, 0, sizeof(struct kgdb_state)); 824 ks->cpu = raw_smp_processor_id(); 825 ks->ex_vector = evector; 826 ks->signo = signo; 827 ks->err_code = ecode; 828 ks->linux_regs = regs; 829 830 if (kgdb_reenter_check(ks)) 831 goto out; /* Ouch, double exception ! */ 832 if (kgdb_info[ks->cpu].enter_kgdb != 0) 833 goto out; 834 835 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 836 out: 837 if (arch_kgdb_ops.enable_nmi) 838 arch_kgdb_ops.enable_nmi(1); 839 return ret; 840 } 841 842 /* 843 * GDB places a breakpoint at this function to know dynamically loaded objects. 844 */ 845 static int module_event(struct notifier_block *self, unsigned long val, 846 void *data) 847 { 848 return 0; 849 } 850 851 static struct notifier_block dbg_module_load_nb = { 852 .notifier_call = module_event, 853 }; 854 855 int kgdb_nmicallback(int cpu, void *regs) 856 { 857 #ifdef CONFIG_SMP 858 struct kgdb_state kgdb_var; 859 struct kgdb_state *ks = &kgdb_var; 860 861 kgdb_info[cpu].rounding_up = false; 862 863 memset(ks, 0, sizeof(struct kgdb_state)); 864 ks->cpu = cpu; 865 ks->linux_regs = regs; 866 867 if (kgdb_info[ks->cpu].enter_kgdb == 0 && 868 raw_spin_is_locked(&dbg_master_lock)) { 869 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE); 870 return 0; 871 } 872 #endif 873 return 1; 874 } 875 876 int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code, 877 atomic_t *send_ready) 878 { 879 #ifdef CONFIG_SMP 880 if (!kgdb_io_ready(0) || !send_ready) 881 return 1; 882 883 if (kgdb_info[cpu].enter_kgdb == 0) { 884 struct kgdb_state kgdb_var; 885 struct kgdb_state *ks = &kgdb_var; 886 887 memset(ks, 0, sizeof(struct kgdb_state)); 888 ks->cpu = cpu; 889 ks->ex_vector = trapnr; 890 ks->signo = SIGTRAP; 891 ks->err_code = err_code; 892 ks->linux_regs = regs; 893 ks->send_ready = send_ready; 894 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 895 return 0; 896 } 897 #endif 898 return 1; 899 } 900 901 static void kgdb_console_write(struct console *co, const char *s, 902 unsigned count) 903 { 904 unsigned long flags; 905 906 /* If we're debugging, or KGDB has not connected, don't try 907 * and print. */ 908 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode) 909 return; 910 911 local_irq_save(flags); 912 gdbstub_msg_write(s, count); 913 local_irq_restore(flags); 914 } 915 916 static struct console kgdbcons = { 917 .name = "kgdb", 918 .write = kgdb_console_write, 919 .flags = CON_PRINTBUFFER | CON_ENABLED, 920 .index = -1, 921 }; 922 923 #ifdef CONFIG_MAGIC_SYSRQ 924 static void sysrq_handle_dbg(int key) 925 { 926 if (!dbg_io_ops) { 927 pr_crit("ERROR: No KGDB I/O module available\n"); 928 return; 929 } 930 if (!kgdb_connected) { 931 #ifdef CONFIG_KGDB_KDB 932 if (!dbg_kdb_mode) 933 pr_crit("KGDB or $3#33 for KDB\n"); 934 #else 935 pr_crit("Entering KGDB\n"); 936 #endif 937 } 938 939 kgdb_breakpoint(); 940 } 941 942 static const struct sysrq_key_op sysrq_dbg_op = { 943 .handler = sysrq_handle_dbg, 944 .help_msg = "debug(g)", 945 .action_msg = "DEBUG", 946 }; 947 #endif 948 949 void kgdb_panic(const char *msg) 950 { 951 if (!kgdb_io_module_registered) 952 return; 953 954 /* 955 * We don't want to get stuck waiting for input from user if 956 * "panic_timeout" indicates the system should automatically 957 * reboot on panic. 958 */ 959 if (panic_timeout) 960 return; 961 962 if (dbg_kdb_mode) 963 kdb_printf("PANIC: %s\n", msg); 964 965 kgdb_breakpoint(); 966 } 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 void __weak kgdb_arch_late(void) 977 { 978 } 979 980 void __init dbg_late_init(void) 981 { 982 dbg_is_early = false; 983 if (kgdb_io_module_registered) 984 kgdb_arch_late(); 985 kdb_init(KDB_INIT_FULL); 986 987 if (kgdb_io_module_registered && kgdb_break_asap) 988 kgdb_initial_breakpoint(); 989 } 990 991 static int 992 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x) 993 { 994 /* 995 * Take the following action on reboot notify depending on value: 996 * 1 == Enter debugger 997 * 0 == [the default] detatch debug client 998 * -1 == Do nothing... and use this until the board resets 999 */ 1000 switch (kgdbreboot) { 1001 case 1: 1002 kgdb_breakpoint(); 1003 case -1: 1004 goto done; 1005 } 1006 if (!dbg_kdb_mode) 1007 gdbstub_exit(code); 1008 done: 1009 return NOTIFY_DONE; 1010 } 1011 1012 static struct notifier_block dbg_reboot_notifier = { 1013 .notifier_call = dbg_notify_reboot, 1014 .next = NULL, 1015 .priority = INT_MAX, 1016 }; 1017 1018 static void kgdb_register_callbacks(void) 1019 { 1020 if (!kgdb_io_module_registered) { 1021 kgdb_io_module_registered = 1; 1022 kgdb_arch_init(); 1023 if (!dbg_is_early) 1024 kgdb_arch_late(); 1025 register_module_notifier(&dbg_module_load_nb); 1026 register_reboot_notifier(&dbg_reboot_notifier); 1027 #ifdef CONFIG_MAGIC_SYSRQ 1028 register_sysrq_key('g', &sysrq_dbg_op); 1029 #endif 1030 if (kgdb_use_con && !kgdb_con_registered) { 1031 register_console(&kgdbcons); 1032 kgdb_con_registered = 1; 1033 } 1034 } 1035 } 1036 1037 static void kgdb_unregister_callbacks(void) 1038 { 1039 /* 1040 * When this routine is called KGDB should unregister from 1041 * handlers and clean up, making sure it is not handling any 1042 * break exceptions at the time. 1043 */ 1044 if (kgdb_io_module_registered) { 1045 kgdb_io_module_registered = 0; 1046 unregister_reboot_notifier(&dbg_reboot_notifier); 1047 unregister_module_notifier(&dbg_module_load_nb); 1048 kgdb_arch_exit(); 1049 #ifdef CONFIG_MAGIC_SYSRQ 1050 unregister_sysrq_key('g', &sysrq_dbg_op); 1051 #endif 1052 if (kgdb_con_registered) { 1053 unregister_console(&kgdbcons); 1054 kgdb_con_registered = 0; 1055 } 1056 } 1057 } 1058 1059 /* 1060 * There are times a tasklet needs to be used vs a compiled in 1061 * break point so as to cause an exception outside a kgdb I/O module, 1062 * such as is the case with kgdboe, where calling a breakpoint in the 1063 * I/O driver itself would be fatal. 1064 */ 1065 static void kgdb_tasklet_bpt(unsigned long ing) 1066 { 1067 kgdb_breakpoint(); 1068 atomic_set(&kgdb_break_tasklet_var, 0); 1069 } 1070 1071 static DECLARE_TASKLET_OLD(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt); 1072 1073 void kgdb_schedule_breakpoint(void) 1074 { 1075 if (atomic_read(&kgdb_break_tasklet_var) || 1076 atomic_read(&kgdb_active) != -1 || 1077 atomic_read(&kgdb_setting_breakpoint)) 1078 return; 1079 atomic_inc(&kgdb_break_tasklet_var); 1080 tasklet_schedule(&kgdb_tasklet_breakpoint); 1081 } 1082 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint); 1083 1084 /** 1085 * kgdb_register_io_module - register KGDB IO module 1086 * @new_dbg_io_ops: the io ops vector 1087 * 1088 * Register it with the KGDB core. 1089 */ 1090 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) 1091 { 1092 struct kgdb_io *old_dbg_io_ops; 1093 int err; 1094 1095 spin_lock(&kgdb_registration_lock); 1096 1097 old_dbg_io_ops = dbg_io_ops; 1098 if (old_dbg_io_ops) { 1099 if (!old_dbg_io_ops->deinit) { 1100 spin_unlock(&kgdb_registration_lock); 1101 1102 pr_err("KGDB I/O driver %s can't replace %s.\n", 1103 new_dbg_io_ops->name, old_dbg_io_ops->name); 1104 return -EBUSY; 1105 } 1106 pr_info("Replacing I/O driver %s with %s\n", 1107 old_dbg_io_ops->name, new_dbg_io_ops->name); 1108 } 1109 1110 if (new_dbg_io_ops->init) { 1111 err = new_dbg_io_ops->init(); 1112 if (err) { 1113 spin_unlock(&kgdb_registration_lock); 1114 return err; 1115 } 1116 } 1117 1118 dbg_io_ops = new_dbg_io_ops; 1119 1120 spin_unlock(&kgdb_registration_lock); 1121 1122 if (old_dbg_io_ops) { 1123 old_dbg_io_ops->deinit(); 1124 return 0; 1125 } 1126 1127 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name); 1128 1129 /* Arm KGDB now. */ 1130 kgdb_register_callbacks(); 1131 1132 if (kgdb_break_asap && 1133 (!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))) 1134 kgdb_initial_breakpoint(); 1135 1136 return 0; 1137 } 1138 EXPORT_SYMBOL_GPL(kgdb_register_io_module); 1139 1140 /** 1141 * kkgdb_unregister_io_module - unregister KGDB IO module 1142 * @old_dbg_io_ops: the io ops vector 1143 * 1144 * Unregister it with the KGDB core. 1145 */ 1146 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops) 1147 { 1148 BUG_ON(kgdb_connected); 1149 1150 /* 1151 * KGDB is no longer able to communicate out, so 1152 * unregister our callbacks and reset state. 1153 */ 1154 kgdb_unregister_callbacks(); 1155 1156 spin_lock(&kgdb_registration_lock); 1157 1158 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops); 1159 dbg_io_ops = NULL; 1160 1161 spin_unlock(&kgdb_registration_lock); 1162 1163 if (old_dbg_io_ops->deinit) 1164 old_dbg_io_ops->deinit(); 1165 1166 pr_info("Unregistered I/O driver %s, debugger disabled\n", 1167 old_dbg_io_ops->name); 1168 } 1169 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module); 1170 1171 int dbg_io_get_char(void) 1172 { 1173 int ret = dbg_io_ops->read_char(); 1174 if (ret == NO_POLL_CHAR) 1175 return -1; 1176 if (!dbg_kdb_mode) 1177 return ret; 1178 if (ret == 127) 1179 return 8; 1180 return ret; 1181 } 1182 1183 /** 1184 * kgdb_breakpoint - generate breakpoint exception 1185 * 1186 * This function will generate a breakpoint exception. It is used at the 1187 * beginning of a program to sync up with a debugger and can be used 1188 * otherwise as a quick means to stop program execution and "break" into 1189 * the debugger. 1190 */ 1191 noinline void kgdb_breakpoint(void) 1192 { 1193 atomic_inc(&kgdb_setting_breakpoint); 1194 wmb(); /* Sync point before breakpoint */ 1195 arch_kgdb_breakpoint(); 1196 wmb(); /* Sync point after breakpoint */ 1197 atomic_dec(&kgdb_setting_breakpoint); 1198 } 1199 EXPORT_SYMBOL_GPL(kgdb_breakpoint); 1200 1201 static int __init opt_kgdb_wait(char *str) 1202 { 1203 kgdb_break_asap = 1; 1204 1205 kdb_init(KDB_INIT_EARLY); 1206 if (kgdb_io_module_registered && 1207 IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)) 1208 kgdb_initial_breakpoint(); 1209 1210 return 0; 1211 } 1212 1213 early_param("kgdbwait", opt_kgdb_wait); 1214