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 notifier, 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 module_param(kgdb_use_con, int, 0644); 98 module_param(kgdbreboot, int, 0644); 99 100 /* 101 * Holds information about breakpoints in a kernel. These breakpoints are 102 * added and removed by gdb. 103 */ 104 static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = { 105 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED } 106 }; 107 108 /* 109 * The CPU# of the active CPU, or -1 if none: 110 */ 111 atomic_t kgdb_active = ATOMIC_INIT(-1); 112 EXPORT_SYMBOL_GPL(kgdb_active); 113 static DEFINE_RAW_SPINLOCK(dbg_master_lock); 114 static DEFINE_RAW_SPINLOCK(dbg_slave_lock); 115 116 /* 117 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early 118 * bootup code (which might not have percpu set up yet): 119 */ 120 static atomic_t masters_in_kgdb; 121 static atomic_t slaves_in_kgdb; 122 atomic_t kgdb_setting_breakpoint; 123 124 struct task_struct *kgdb_usethread; 125 struct task_struct *kgdb_contthread; 126 127 int kgdb_single_step; 128 static pid_t kgdb_sstep_pid; 129 130 /* to keep track of the CPU which is doing the single stepping*/ 131 atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1); 132 133 /* 134 * If you are debugging a problem where roundup (the collection of 135 * all other CPUs) is a problem [this should be extremely rare], 136 * then use the nokgdbroundup option to avoid roundup. In that case 137 * the other CPUs might interfere with your debugging context, so 138 * use this with care: 139 */ 140 static int kgdb_do_roundup = 1; 141 142 static int __init opt_nokgdbroundup(char *str) 143 { 144 kgdb_do_roundup = 0; 145 146 return 0; 147 } 148 149 early_param("nokgdbroundup", opt_nokgdbroundup); 150 151 /* 152 * Finally, some KGDB code :-) 153 */ 154 155 /* 156 * Weak aliases for breakpoint management, 157 * can be overridden by architectures when needed: 158 */ 159 int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) 160 { 161 int err; 162 163 err = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr, 164 BREAK_INSTR_SIZE); 165 if (err) 166 return err; 167 err = copy_to_kernel_nofault((char *)bpt->bpt_addr, 168 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE); 169 return err; 170 } 171 NOKPROBE_SYMBOL(kgdb_arch_set_breakpoint); 172 173 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt) 174 { 175 return copy_to_kernel_nofault((char *)bpt->bpt_addr, 176 (char *)bpt->saved_instr, BREAK_INSTR_SIZE); 177 } 178 NOKPROBE_SYMBOL(kgdb_arch_remove_breakpoint); 179 180 int __weak kgdb_validate_break_address(unsigned long addr) 181 { 182 struct kgdb_bkpt tmp; 183 int err; 184 185 if (kgdb_within_blocklist(addr)) 186 return -EINVAL; 187 188 /* Validate setting the breakpoint and then removing it. If the 189 * remove fails, the kernel needs to emit a bad message because we 190 * are deep trouble not being able to put things back the way we 191 * found them. 192 */ 193 tmp.bpt_addr = addr; 194 err = kgdb_arch_set_breakpoint(&tmp); 195 if (err) 196 return err; 197 err = kgdb_arch_remove_breakpoint(&tmp); 198 if (err) 199 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n", 200 addr); 201 return err; 202 } 203 204 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs) 205 { 206 return instruction_pointer(regs); 207 } 208 NOKPROBE_SYMBOL(kgdb_arch_pc); 209 210 int __weak kgdb_arch_init(void) 211 { 212 return 0; 213 } 214 215 int __weak kgdb_skipexception(int exception, struct pt_regs *regs) 216 { 217 return 0; 218 } 219 NOKPROBE_SYMBOL(kgdb_skipexception); 220 221 #ifdef CONFIG_SMP 222 223 /* 224 * Default (weak) implementation for kgdb_roundup_cpus 225 */ 226 227 void __weak kgdb_call_nmi_hook(void *ignored) 228 { 229 /* 230 * NOTE: get_irq_regs() is supposed to get the registers from 231 * before the IPI interrupt happened and so is supposed to 232 * show where the processor was. In some situations it's 233 * possible we might be called without an IPI, so it might be 234 * safer to figure out how to make kgdb_breakpoint() work 235 * properly here. 236 */ 237 kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs()); 238 } 239 NOKPROBE_SYMBOL(kgdb_call_nmi_hook); 240 241 static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd) = 242 CSD_INIT(kgdb_call_nmi_hook, NULL); 243 244 void __weak kgdb_roundup_cpus(void) 245 { 246 call_single_data_t *csd; 247 int this_cpu = raw_smp_processor_id(); 248 int cpu; 249 int ret; 250 251 for_each_online_cpu(cpu) { 252 /* No need to roundup ourselves */ 253 if (cpu == this_cpu) 254 continue; 255 256 csd = &per_cpu(kgdb_roundup_csd, cpu); 257 258 /* 259 * If it didn't round up last time, don't try again 260 * since smp_call_function_single_async() will block. 261 * 262 * If rounding_up is false then we know that the 263 * previous call must have at least started and that 264 * means smp_call_function_single_async() won't block. 265 */ 266 if (kgdb_info[cpu].rounding_up) 267 continue; 268 kgdb_info[cpu].rounding_up = true; 269 270 ret = smp_call_function_single_async(cpu, csd); 271 if (ret) 272 kgdb_info[cpu].rounding_up = false; 273 } 274 } 275 NOKPROBE_SYMBOL(kgdb_roundup_cpus); 276 277 #endif 278 279 /* 280 * Some architectures need cache flushes when we set/clear a 281 * breakpoint: 282 */ 283 static void kgdb_flush_swbreak_addr(unsigned long addr) 284 { 285 if (!CACHE_FLUSH_IS_SAFE) 286 return; 287 288 if (current->mm) { 289 int i; 290 291 for (i = 0; i < VMACACHE_SIZE; i++) { 292 if (!current->vmacache.vmas[i]) 293 continue; 294 flush_cache_range(current->vmacache.vmas[i], 295 addr, addr + BREAK_INSTR_SIZE); 296 } 297 } 298 299 /* Force flush instruction cache if it was outside the mm */ 300 flush_icache_range(addr, addr + BREAK_INSTR_SIZE); 301 } 302 NOKPROBE_SYMBOL(kgdb_flush_swbreak_addr); 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 NOKPROBE_SYMBOL(dbg_activate_sw_breakpoints); 331 332 int dbg_set_sw_break(unsigned long addr) 333 { 334 int err = kgdb_validate_break_address(addr); 335 int breakno = -1; 336 int i; 337 338 if (err) 339 return err; 340 341 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 342 if ((kgdb_break[i].state == BP_SET) && 343 (kgdb_break[i].bpt_addr == addr)) 344 return -EEXIST; 345 } 346 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 347 if (kgdb_break[i].state == BP_REMOVED && 348 kgdb_break[i].bpt_addr == addr) { 349 breakno = i; 350 break; 351 } 352 } 353 354 if (breakno == -1) { 355 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 356 if (kgdb_break[i].state == BP_UNDEFINED) { 357 breakno = i; 358 break; 359 } 360 } 361 } 362 363 if (breakno == -1) 364 return -E2BIG; 365 366 kgdb_break[breakno].state = BP_SET; 367 kgdb_break[breakno].type = BP_BREAKPOINT; 368 kgdb_break[breakno].bpt_addr = addr; 369 370 return 0; 371 } 372 373 int dbg_deactivate_sw_breakpoints(void) 374 { 375 int error; 376 int ret = 0; 377 int i; 378 379 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 380 if (kgdb_break[i].state != BP_ACTIVE) 381 continue; 382 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); 383 if (error) { 384 pr_info("BP remove failed: %lx\n", 385 kgdb_break[i].bpt_addr); 386 ret = error; 387 } 388 389 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); 390 kgdb_break[i].state = BP_SET; 391 } 392 return ret; 393 } 394 NOKPROBE_SYMBOL(dbg_deactivate_sw_breakpoints); 395 396 int dbg_remove_sw_break(unsigned long addr) 397 { 398 int i; 399 400 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 401 if ((kgdb_break[i].state == BP_SET) && 402 (kgdb_break[i].bpt_addr == addr)) { 403 kgdb_break[i].state = BP_REMOVED; 404 return 0; 405 } 406 } 407 return -ENOENT; 408 } 409 410 int kgdb_isremovedbreak(unsigned long addr) 411 { 412 int i; 413 414 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 415 if ((kgdb_break[i].state == BP_REMOVED) && 416 (kgdb_break[i].bpt_addr == addr)) 417 return 1; 418 } 419 return 0; 420 } 421 422 int kgdb_has_hit_break(unsigned long addr) 423 { 424 int i; 425 426 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 427 if (kgdb_break[i].state == BP_ACTIVE && 428 kgdb_break[i].bpt_addr == addr) 429 return 1; 430 } 431 return 0; 432 } 433 434 int dbg_remove_all_break(void) 435 { 436 int error; 437 int i; 438 439 /* Clear memory breakpoints. */ 440 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 441 if (kgdb_break[i].state != BP_ACTIVE) 442 goto setundefined; 443 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); 444 if (error) 445 pr_err("breakpoint remove failed: %lx\n", 446 kgdb_break[i].bpt_addr); 447 setundefined: 448 kgdb_break[i].state = BP_UNDEFINED; 449 } 450 451 /* Clear hardware breakpoints. */ 452 if (arch_kgdb_ops.remove_all_hw_break) 453 arch_kgdb_ops.remove_all_hw_break(); 454 455 return 0; 456 } 457 458 #ifdef CONFIG_KGDB_KDB 459 void kdb_dump_stack_on_cpu(int cpu) 460 { 461 if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) { 462 dump_stack(); 463 return; 464 } 465 466 if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) { 467 kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n", 468 cpu); 469 return; 470 } 471 472 /* 473 * In general, architectures don't support dumping the stack of a 474 * "running" process that's not the current one. From the point of 475 * view of the Linux, kernel processes that are looping in the kgdb 476 * slave loop are still "running". There's also no API (that actually 477 * works across all architectures) that can do a stack crawl based 478 * on registers passed as a parameter. 479 * 480 * Solve this conundrum by asking slave CPUs to do the backtrace 481 * themselves. 482 */ 483 kgdb_info[cpu].exception_state |= DCPU_WANT_BT; 484 while (kgdb_info[cpu].exception_state & DCPU_WANT_BT) 485 cpu_relax(); 486 } 487 #endif 488 489 /* 490 * Return true if there is a valid kgdb I/O module. Also if no 491 * debugger is attached a message can be printed to the console about 492 * waiting for the debugger to attach. 493 * 494 * The print_wait argument is only to be true when called from inside 495 * the core kgdb_handle_exception, because it will wait for the 496 * debugger to attach. 497 */ 498 static int kgdb_io_ready(int print_wait) 499 { 500 if (!dbg_io_ops) 501 return 0; 502 if (kgdb_connected) 503 return 1; 504 if (atomic_read(&kgdb_setting_breakpoint)) 505 return 1; 506 if (print_wait) { 507 #ifdef CONFIG_KGDB_KDB 508 if (!dbg_kdb_mode) 509 pr_crit("waiting... or $3#33 for KDB\n"); 510 #else 511 pr_crit("Waiting for remote debugger\n"); 512 #endif 513 } 514 return 1; 515 } 516 NOKPROBE_SYMBOL(kgdb_io_ready); 517 518 static int kgdb_reenter_check(struct kgdb_state *ks) 519 { 520 unsigned long addr; 521 522 if (atomic_read(&kgdb_active) != raw_smp_processor_id()) 523 return 0; 524 525 /* Panic on recursive debugger calls: */ 526 exception_level++; 527 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs); 528 dbg_deactivate_sw_breakpoints(); 529 530 /* 531 * If the break point removed ok at the place exception 532 * occurred, try to recover and print a warning to the end 533 * user because the user planted a breakpoint in a place that 534 * KGDB needs in order to function. 535 */ 536 if (dbg_remove_sw_break(addr) == 0) { 537 exception_level = 0; 538 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 539 dbg_activate_sw_breakpoints(); 540 pr_crit("re-enter error: breakpoint removed %lx\n", addr); 541 WARN_ON_ONCE(1); 542 543 return 1; 544 } 545 dbg_remove_all_break(); 546 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 547 548 if (exception_level > 1) { 549 dump_stack(); 550 kgdb_io_module_registered = false; 551 panic("Recursive entry to debugger"); 552 } 553 554 pr_crit("re-enter exception: ALL breakpoints killed\n"); 555 #ifdef CONFIG_KGDB_KDB 556 /* Allow kdb to debug itself one level */ 557 return 0; 558 #endif 559 dump_stack(); 560 panic("Recursive entry to debugger"); 561 562 return 1; 563 } 564 NOKPROBE_SYMBOL(kgdb_reenter_check); 565 566 static void dbg_touch_watchdogs(void) 567 { 568 touch_softlockup_watchdog_sync(); 569 clocksource_touch_watchdog(); 570 rcu_cpu_stall_reset(); 571 } 572 NOKPROBE_SYMBOL(dbg_touch_watchdogs); 573 574 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, 575 int exception_state) 576 { 577 unsigned long flags; 578 int sstep_tries = 100; 579 int error; 580 int cpu; 581 int trace_on = 0; 582 int online_cpus = num_online_cpus(); 583 u64 time_left; 584 585 kgdb_info[ks->cpu].enter_kgdb++; 586 kgdb_info[ks->cpu].exception_state |= exception_state; 587 588 if (exception_state == DCPU_WANT_MASTER) 589 atomic_inc(&masters_in_kgdb); 590 else 591 atomic_inc(&slaves_in_kgdb); 592 593 if (arch_kgdb_ops.disable_hw_break) 594 arch_kgdb_ops.disable_hw_break(regs); 595 596 acquirelock: 597 rcu_read_lock(); 598 /* 599 * Interrupts will be restored by the 'trap return' code, except when 600 * single stepping. 601 */ 602 local_irq_save(flags); 603 604 cpu = ks->cpu; 605 kgdb_info[cpu].debuggerinfo = regs; 606 kgdb_info[cpu].task = current; 607 kgdb_info[cpu].ret_state = 0; 608 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT; 609 610 /* Make sure the above info reaches the primary CPU */ 611 smp_mb(); 612 613 if (exception_level == 1) { 614 if (raw_spin_trylock(&dbg_master_lock)) 615 atomic_xchg(&kgdb_active, cpu); 616 goto cpu_master_loop; 617 } 618 619 /* 620 * CPU will loop if it is a slave or request to become a kgdb 621 * master cpu and acquire the kgdb_active lock: 622 */ 623 while (1) { 624 cpu_loop: 625 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) { 626 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER; 627 goto cpu_master_loop; 628 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) { 629 if (raw_spin_trylock(&dbg_master_lock)) { 630 atomic_xchg(&kgdb_active, cpu); 631 break; 632 } 633 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) { 634 dump_stack(); 635 kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT; 636 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) { 637 if (!raw_spin_is_locked(&dbg_slave_lock)) 638 goto return_normal; 639 } else { 640 return_normal: 641 /* Return to normal operation by executing any 642 * hw breakpoint fixup. 643 */ 644 if (arch_kgdb_ops.correct_hw_break) 645 arch_kgdb_ops.correct_hw_break(); 646 if (trace_on) 647 tracing_on(); 648 kgdb_info[cpu].debuggerinfo = NULL; 649 kgdb_info[cpu].task = NULL; 650 kgdb_info[cpu].exception_state &= 651 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 652 kgdb_info[cpu].enter_kgdb--; 653 smp_mb__before_atomic(); 654 atomic_dec(&slaves_in_kgdb); 655 dbg_touch_watchdogs(); 656 local_irq_restore(flags); 657 rcu_read_unlock(); 658 return 0; 659 } 660 cpu_relax(); 661 } 662 663 /* 664 * For single stepping, try to only enter on the processor 665 * that was single stepping. To guard against a deadlock, the 666 * kernel will only try for the value of sstep_tries before 667 * giving up and continuing on. 668 */ 669 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 && 670 (kgdb_info[cpu].task && 671 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) { 672 atomic_set(&kgdb_active, -1); 673 raw_spin_unlock(&dbg_master_lock); 674 dbg_touch_watchdogs(); 675 local_irq_restore(flags); 676 rcu_read_unlock(); 677 678 goto acquirelock; 679 } 680 681 if (!kgdb_io_ready(1)) { 682 kgdb_info[cpu].ret_state = 1; 683 goto kgdb_restore; /* No I/O connection, resume the system */ 684 } 685 686 /* 687 * Don't enter if we have hit a removed breakpoint. 688 */ 689 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs)) 690 goto kgdb_restore; 691 692 atomic_inc(&ignore_console_lock_warning); 693 694 /* Call the I/O driver's pre_exception routine */ 695 if (dbg_io_ops->pre_exception) 696 dbg_io_ops->pre_exception(); 697 698 /* 699 * Get the passive CPU lock which will hold all the non-primary 700 * CPU in a spin state while the debugger is active 701 */ 702 if (!kgdb_single_step) 703 raw_spin_lock(&dbg_slave_lock); 704 705 #ifdef CONFIG_SMP 706 /* If send_ready set, slaves are already waiting */ 707 if (ks->send_ready) 708 atomic_set(ks->send_ready, 1); 709 710 /* Signal the other CPUs to enter kgdb_wait() */ 711 else if ((!kgdb_single_step) && kgdb_do_roundup) 712 kgdb_roundup_cpus(); 713 #endif 714 715 /* 716 * Wait for the other CPUs to be notified and be waiting for us: 717 */ 718 time_left = MSEC_PER_SEC; 719 while (kgdb_do_roundup && --time_left && 720 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) != 721 online_cpus) 722 udelay(1000); 723 if (!time_left) 724 pr_crit("Timed out waiting for secondary CPUs.\n"); 725 726 /* 727 * At this point the primary processor is completely 728 * in the debugger and all secondary CPUs are quiescent 729 */ 730 dbg_deactivate_sw_breakpoints(); 731 kgdb_single_step = 0; 732 kgdb_contthread = current; 733 exception_level = 0; 734 trace_on = tracing_is_on(); 735 if (trace_on) 736 tracing_off(); 737 738 while (1) { 739 cpu_master_loop: 740 if (dbg_kdb_mode) { 741 kgdb_connected = 1; 742 error = kdb_stub(ks); 743 if (error == -1) 744 continue; 745 kgdb_connected = 0; 746 } else { 747 error = gdb_serial_stub(ks); 748 } 749 750 if (error == DBG_PASS_EVENT) { 751 dbg_kdb_mode = !dbg_kdb_mode; 752 } else if (error == DBG_SWITCH_CPU_EVENT) { 753 kgdb_info[dbg_switch_cpu].exception_state |= 754 DCPU_NEXT_MASTER; 755 goto cpu_loop; 756 } else { 757 kgdb_info[cpu].ret_state = error; 758 break; 759 } 760 } 761 762 dbg_activate_sw_breakpoints(); 763 764 /* Call the I/O driver's post_exception routine */ 765 if (dbg_io_ops->post_exception) 766 dbg_io_ops->post_exception(); 767 768 atomic_dec(&ignore_console_lock_warning); 769 770 if (!kgdb_single_step) { 771 raw_spin_unlock(&dbg_slave_lock); 772 /* Wait till all the CPUs have quit from the debugger. */ 773 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb)) 774 cpu_relax(); 775 } 776 777 kgdb_restore: 778 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) { 779 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step); 780 if (kgdb_info[sstep_cpu].task) 781 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid; 782 else 783 kgdb_sstep_pid = 0; 784 } 785 if (arch_kgdb_ops.correct_hw_break) 786 arch_kgdb_ops.correct_hw_break(); 787 if (trace_on) 788 tracing_on(); 789 790 kgdb_info[cpu].debuggerinfo = NULL; 791 kgdb_info[cpu].task = NULL; 792 kgdb_info[cpu].exception_state &= 793 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 794 kgdb_info[cpu].enter_kgdb--; 795 smp_mb__before_atomic(); 796 atomic_dec(&masters_in_kgdb); 797 /* Free kgdb_active */ 798 atomic_set(&kgdb_active, -1); 799 raw_spin_unlock(&dbg_master_lock); 800 dbg_touch_watchdogs(); 801 local_irq_restore(flags); 802 rcu_read_unlock(); 803 804 return kgdb_info[cpu].ret_state; 805 } 806 NOKPROBE_SYMBOL(kgdb_cpu_enter); 807 808 /* 809 * kgdb_handle_exception() - main entry point from a kernel exception 810 * 811 * Locking hierarchy: 812 * interface locks, if any (begin_session) 813 * kgdb lock (kgdb_active) 814 */ 815 int 816 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 817 { 818 struct kgdb_state kgdb_var; 819 struct kgdb_state *ks = &kgdb_var; 820 int ret = 0; 821 822 if (arch_kgdb_ops.enable_nmi) 823 arch_kgdb_ops.enable_nmi(0); 824 /* 825 * Avoid entering the debugger if we were triggered due to an oops 826 * but panic_timeout indicates the system should automatically 827 * reboot on panic. We don't want to get stuck waiting for input 828 * on such systems, especially if its "just" an oops. 829 */ 830 if (signo != SIGTRAP && panic_timeout) 831 return 1; 832 833 memset(ks, 0, sizeof(struct kgdb_state)); 834 ks->cpu = raw_smp_processor_id(); 835 ks->ex_vector = evector; 836 ks->signo = signo; 837 ks->err_code = ecode; 838 ks->linux_regs = regs; 839 840 if (kgdb_reenter_check(ks)) 841 goto out; /* Ouch, double exception ! */ 842 if (kgdb_info[ks->cpu].enter_kgdb != 0) 843 goto out; 844 845 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 846 out: 847 if (arch_kgdb_ops.enable_nmi) 848 arch_kgdb_ops.enable_nmi(1); 849 return ret; 850 } 851 NOKPROBE_SYMBOL(kgdb_handle_exception); 852 853 /* 854 * GDB places a breakpoint at this function to know dynamically loaded objects. 855 */ 856 static int module_event(struct notifier_block *self, unsigned long val, 857 void *data) 858 { 859 return 0; 860 } 861 862 static struct notifier_block dbg_module_load_nb = { 863 .notifier_call = module_event, 864 }; 865 866 int kgdb_nmicallback(int cpu, void *regs) 867 { 868 #ifdef CONFIG_SMP 869 struct kgdb_state kgdb_var; 870 struct kgdb_state *ks = &kgdb_var; 871 872 kgdb_info[cpu].rounding_up = false; 873 874 memset(ks, 0, sizeof(struct kgdb_state)); 875 ks->cpu = cpu; 876 ks->linux_regs = regs; 877 878 if (kgdb_info[ks->cpu].enter_kgdb == 0 && 879 raw_spin_is_locked(&dbg_master_lock)) { 880 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE); 881 return 0; 882 } 883 #endif 884 return 1; 885 } 886 NOKPROBE_SYMBOL(kgdb_nmicallback); 887 888 int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code, 889 atomic_t *send_ready) 890 { 891 #ifdef CONFIG_SMP 892 if (!kgdb_io_ready(0) || !send_ready) 893 return 1; 894 895 if (kgdb_info[cpu].enter_kgdb == 0) { 896 struct kgdb_state kgdb_var; 897 struct kgdb_state *ks = &kgdb_var; 898 899 memset(ks, 0, sizeof(struct kgdb_state)); 900 ks->cpu = cpu; 901 ks->ex_vector = trapnr; 902 ks->signo = SIGTRAP; 903 ks->err_code = err_code; 904 ks->linux_regs = regs; 905 ks->send_ready = send_ready; 906 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 907 return 0; 908 } 909 #endif 910 return 1; 911 } 912 NOKPROBE_SYMBOL(kgdb_nmicallin); 913 914 static void kgdb_console_write(struct console *co, const char *s, 915 unsigned count) 916 { 917 unsigned long flags; 918 919 /* If we're debugging, or KGDB has not connected, don't try 920 * and print. */ 921 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode) 922 return; 923 924 local_irq_save(flags); 925 gdbstub_msg_write(s, count); 926 local_irq_restore(flags); 927 } 928 929 static struct console kgdbcons = { 930 .name = "kgdb", 931 .write = kgdb_console_write, 932 .flags = CON_PRINTBUFFER | CON_ENABLED, 933 .index = -1, 934 }; 935 936 static int __init opt_kgdb_con(char *str) 937 { 938 kgdb_use_con = 1; 939 940 if (kgdb_io_module_registered && !kgdb_con_registered) { 941 register_console(&kgdbcons); 942 kgdb_con_registered = 1; 943 } 944 945 return 0; 946 } 947 948 early_param("kgdbcon", opt_kgdb_con); 949 950 #ifdef CONFIG_MAGIC_SYSRQ 951 static void sysrq_handle_dbg(int key) 952 { 953 if (!dbg_io_ops) { 954 pr_crit("ERROR: No KGDB I/O module available\n"); 955 return; 956 } 957 if (!kgdb_connected) { 958 #ifdef CONFIG_KGDB_KDB 959 if (!dbg_kdb_mode) 960 pr_crit("KGDB or $3#33 for KDB\n"); 961 #else 962 pr_crit("Entering KGDB\n"); 963 #endif 964 } 965 966 kgdb_breakpoint(); 967 } 968 969 static const struct sysrq_key_op sysrq_dbg_op = { 970 .handler = sysrq_handle_dbg, 971 .help_msg = "debug(g)", 972 .action_msg = "DEBUG", 973 }; 974 #endif 975 976 void kgdb_panic(const char *msg) 977 { 978 if (!kgdb_io_module_registered) 979 return; 980 981 /* 982 * We don't want to get stuck waiting for input from user if 983 * "panic_timeout" indicates the system should automatically 984 * reboot on panic. 985 */ 986 if (panic_timeout) 987 return; 988 989 if (dbg_kdb_mode) 990 kdb_printf("PANIC: %s\n", msg); 991 992 kgdb_breakpoint(); 993 } 994 995 static void kgdb_initial_breakpoint(void) 996 { 997 kgdb_break_asap = 0; 998 999 pr_crit("Waiting for connection from remote gdb...\n"); 1000 kgdb_breakpoint(); 1001 } 1002 1003 void __weak kgdb_arch_late(void) 1004 { 1005 } 1006 1007 void __init dbg_late_init(void) 1008 { 1009 dbg_is_early = false; 1010 if (kgdb_io_module_registered) 1011 kgdb_arch_late(); 1012 kdb_init(KDB_INIT_FULL); 1013 1014 if (kgdb_io_module_registered && kgdb_break_asap) 1015 kgdb_initial_breakpoint(); 1016 } 1017 1018 static int 1019 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x) 1020 { 1021 /* 1022 * Take the following action on reboot notify depending on value: 1023 * 1 == Enter debugger 1024 * 0 == [the default] detatch debug client 1025 * -1 == Do nothing... and use this until the board resets 1026 */ 1027 switch (kgdbreboot) { 1028 case 1: 1029 kgdb_breakpoint(); 1030 case -1: 1031 goto done; 1032 } 1033 if (!dbg_kdb_mode) 1034 gdbstub_exit(code); 1035 done: 1036 return NOTIFY_DONE; 1037 } 1038 1039 static struct notifier_block dbg_reboot_notifier = { 1040 .notifier_call = dbg_notify_reboot, 1041 .next = NULL, 1042 .priority = INT_MAX, 1043 }; 1044 1045 static void kgdb_register_callbacks(void) 1046 { 1047 if (!kgdb_io_module_registered) { 1048 kgdb_io_module_registered = 1; 1049 kgdb_arch_init(); 1050 if (!dbg_is_early) 1051 kgdb_arch_late(); 1052 register_module_notifier(&dbg_module_load_nb); 1053 register_reboot_notifier(&dbg_reboot_notifier); 1054 #ifdef CONFIG_MAGIC_SYSRQ 1055 register_sysrq_key('g', &sysrq_dbg_op); 1056 #endif 1057 if (kgdb_use_con && !kgdb_con_registered) { 1058 register_console(&kgdbcons); 1059 kgdb_con_registered = 1; 1060 } 1061 } 1062 } 1063 1064 static void kgdb_unregister_callbacks(void) 1065 { 1066 /* 1067 * When this routine is called KGDB should unregister from 1068 * handlers and clean up, making sure it is not handling any 1069 * break exceptions at the time. 1070 */ 1071 if (kgdb_io_module_registered) { 1072 kgdb_io_module_registered = 0; 1073 unregister_reboot_notifier(&dbg_reboot_notifier); 1074 unregister_module_notifier(&dbg_module_load_nb); 1075 kgdb_arch_exit(); 1076 #ifdef CONFIG_MAGIC_SYSRQ 1077 unregister_sysrq_key('g', &sysrq_dbg_op); 1078 #endif 1079 if (kgdb_con_registered) { 1080 unregister_console(&kgdbcons); 1081 kgdb_con_registered = 0; 1082 } 1083 } 1084 } 1085 1086 /** 1087 * kgdb_register_io_module - register KGDB IO module 1088 * @new_dbg_io_ops: the io ops vector 1089 * 1090 * Register it with the KGDB core. 1091 */ 1092 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) 1093 { 1094 struct kgdb_io *old_dbg_io_ops; 1095 int err; 1096 1097 spin_lock(&kgdb_registration_lock); 1098 1099 old_dbg_io_ops = dbg_io_ops; 1100 if (old_dbg_io_ops) { 1101 if (!old_dbg_io_ops->deinit) { 1102 spin_unlock(&kgdb_registration_lock); 1103 1104 pr_err("KGDB I/O driver %s can't replace %s.\n", 1105 new_dbg_io_ops->name, old_dbg_io_ops->name); 1106 return -EBUSY; 1107 } 1108 pr_info("Replacing I/O driver %s with %s\n", 1109 old_dbg_io_ops->name, new_dbg_io_ops->name); 1110 } 1111 1112 if (new_dbg_io_ops->init) { 1113 err = new_dbg_io_ops->init(); 1114 if (err) { 1115 spin_unlock(&kgdb_registration_lock); 1116 return err; 1117 } 1118 } 1119 1120 dbg_io_ops = new_dbg_io_ops; 1121 1122 spin_unlock(&kgdb_registration_lock); 1123 1124 if (old_dbg_io_ops) { 1125 old_dbg_io_ops->deinit(); 1126 return 0; 1127 } 1128 1129 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name); 1130 1131 /* Arm KGDB now. */ 1132 kgdb_register_callbacks(); 1133 1134 if (kgdb_break_asap && 1135 (!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))) 1136 kgdb_initial_breakpoint(); 1137 1138 return 0; 1139 } 1140 EXPORT_SYMBOL_GPL(kgdb_register_io_module); 1141 1142 /** 1143 * kgdb_unregister_io_module - unregister KGDB IO module 1144 * @old_dbg_io_ops: the io ops vector 1145 * 1146 * Unregister it with the KGDB core. 1147 */ 1148 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops) 1149 { 1150 BUG_ON(kgdb_connected); 1151 1152 /* 1153 * KGDB is no longer able to communicate out, so 1154 * unregister our callbacks and reset state. 1155 */ 1156 kgdb_unregister_callbacks(); 1157 1158 spin_lock(&kgdb_registration_lock); 1159 1160 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops); 1161 dbg_io_ops = NULL; 1162 1163 spin_unlock(&kgdb_registration_lock); 1164 1165 if (old_dbg_io_ops->deinit) 1166 old_dbg_io_ops->deinit(); 1167 1168 pr_info("Unregistered I/O driver %s, debugger disabled\n", 1169 old_dbg_io_ops->name); 1170 } 1171 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module); 1172 1173 int dbg_io_get_char(void) 1174 { 1175 int ret = dbg_io_ops->read_char(); 1176 if (ret == NO_POLL_CHAR) 1177 return -1; 1178 if (!dbg_kdb_mode) 1179 return ret; 1180 if (ret == 127) 1181 return 8; 1182 return ret; 1183 } 1184 1185 /** 1186 * kgdb_breakpoint - generate breakpoint exception 1187 * 1188 * This function will generate a breakpoint exception. It is used at the 1189 * beginning of a program to sync up with a debugger and can be used 1190 * otherwise as a quick means to stop program execution and "break" into 1191 * the debugger. 1192 */ 1193 noinline void kgdb_breakpoint(void) 1194 { 1195 atomic_inc(&kgdb_setting_breakpoint); 1196 wmb(); /* Sync point before breakpoint */ 1197 arch_kgdb_breakpoint(); 1198 wmb(); /* Sync point after breakpoint */ 1199 atomic_dec(&kgdb_setting_breakpoint); 1200 } 1201 EXPORT_SYMBOL_GPL(kgdb_breakpoint); 1202 1203 static int __init opt_kgdb_wait(char *str) 1204 { 1205 kgdb_break_asap = 1; 1206 1207 kdb_init(KDB_INIT_EARLY); 1208 if (kgdb_io_module_registered && 1209 IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)) 1210 kgdb_initial_breakpoint(); 1211 1212 return 0; 1213 } 1214 1215 early_param("kgdbwait", opt_kgdb_wait); 1216