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 static atomic_t kgdb_break_tasklet_var; 123 atomic_t kgdb_setting_breakpoint; 124 125 struct task_struct *kgdb_usethread; 126 struct task_struct *kgdb_contthread; 127 128 int kgdb_single_step; 129 static pid_t kgdb_sstep_pid; 130 131 /* to keep track of the CPU which is doing the single stepping*/ 132 atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1); 133 134 /* 135 * If you are debugging a problem where roundup (the collection of 136 * all other CPUs) is a problem [this should be extremely rare], 137 * then use the nokgdbroundup option to avoid roundup. In that case 138 * the other CPUs might interfere with your debugging context, so 139 * use this with care: 140 */ 141 static int kgdb_do_roundup = 1; 142 143 static int __init opt_nokgdbroundup(char *str) 144 { 145 kgdb_do_roundup = 0; 146 147 return 0; 148 } 149 150 early_param("nokgdbroundup", opt_nokgdbroundup); 151 152 /* 153 * Finally, some KGDB code :-) 154 */ 155 156 /* 157 * Weak aliases for breakpoint management, 158 * can be overridden by architectures when needed: 159 */ 160 int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) 161 { 162 int err; 163 164 err = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr, 165 BREAK_INSTR_SIZE); 166 if (err) 167 return err; 168 err = copy_to_kernel_nofault((char *)bpt->bpt_addr, 169 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE); 170 return err; 171 } 172 NOKPROBE_SYMBOL(kgdb_arch_set_breakpoint); 173 174 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt) 175 { 176 return copy_to_kernel_nofault((char *)bpt->bpt_addr, 177 (char *)bpt->saved_instr, BREAK_INSTR_SIZE); 178 } 179 NOKPROBE_SYMBOL(kgdb_arch_remove_breakpoint); 180 181 int __weak kgdb_validate_break_address(unsigned long addr) 182 { 183 struct kgdb_bkpt tmp; 184 int err; 185 186 if (kgdb_within_blocklist(addr)) 187 return -EINVAL; 188 189 /* Validate setting the breakpoint and then removing it. If the 190 * remove fails, the kernel needs to emit a bad message because we 191 * are deep trouble not being able to put things back the way we 192 * found them. 193 */ 194 tmp.bpt_addr = addr; 195 err = kgdb_arch_set_breakpoint(&tmp); 196 if (err) 197 return err; 198 err = kgdb_arch_remove_breakpoint(&tmp); 199 if (err) 200 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n", 201 addr); 202 return err; 203 } 204 205 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs) 206 { 207 return instruction_pointer(regs); 208 } 209 NOKPROBE_SYMBOL(kgdb_arch_pc); 210 211 int __weak kgdb_arch_init(void) 212 { 213 return 0; 214 } 215 216 int __weak kgdb_skipexception(int exception, struct pt_regs *regs) 217 { 218 return 0; 219 } 220 NOKPROBE_SYMBOL(kgdb_skipexception); 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 NOKPROBE_SYMBOL(kgdb_call_nmi_hook); 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 csd->func = kgdb_call_nmi_hook; 271 ret = smp_call_function_single_async(cpu, csd); 272 if (ret) 273 kgdb_info[cpu].rounding_up = false; 274 } 275 } 276 NOKPROBE_SYMBOL(kgdb_roundup_cpus); 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 NOKPROBE_SYMBOL(kgdb_flush_swbreak_addr); 304 305 /* 306 * SW breakpoint management: 307 */ 308 int dbg_activate_sw_breakpoints(void) 309 { 310 int error; 311 int ret = 0; 312 int i; 313 314 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 315 if (kgdb_break[i].state != BP_SET) 316 continue; 317 318 error = kgdb_arch_set_breakpoint(&kgdb_break[i]); 319 if (error) { 320 ret = error; 321 pr_info("BP install failed: %lx\n", 322 kgdb_break[i].bpt_addr); 323 continue; 324 } 325 326 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); 327 kgdb_break[i].state = BP_ACTIVE; 328 } 329 return ret; 330 } 331 NOKPROBE_SYMBOL(dbg_activate_sw_breakpoints); 332 333 int dbg_set_sw_break(unsigned long addr) 334 { 335 int err = kgdb_validate_break_address(addr); 336 int breakno = -1; 337 int i; 338 339 if (err) 340 return err; 341 342 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 343 if ((kgdb_break[i].state == BP_SET) && 344 (kgdb_break[i].bpt_addr == addr)) 345 return -EEXIST; 346 } 347 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 348 if (kgdb_break[i].state == BP_REMOVED && 349 kgdb_break[i].bpt_addr == addr) { 350 breakno = i; 351 break; 352 } 353 } 354 355 if (breakno == -1) { 356 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 357 if (kgdb_break[i].state == BP_UNDEFINED) { 358 breakno = i; 359 break; 360 } 361 } 362 } 363 364 if (breakno == -1) 365 return -E2BIG; 366 367 kgdb_break[breakno].state = BP_SET; 368 kgdb_break[breakno].type = BP_BREAKPOINT; 369 kgdb_break[breakno].bpt_addr = addr; 370 371 return 0; 372 } 373 374 int dbg_deactivate_sw_breakpoints(void) 375 { 376 int error; 377 int ret = 0; 378 int i; 379 380 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 381 if (kgdb_break[i].state != BP_ACTIVE) 382 continue; 383 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); 384 if (error) { 385 pr_info("BP remove failed: %lx\n", 386 kgdb_break[i].bpt_addr); 387 ret = error; 388 } 389 390 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); 391 kgdb_break[i].state = BP_SET; 392 } 393 return ret; 394 } 395 NOKPROBE_SYMBOL(dbg_deactivate_sw_breakpoints); 396 397 int dbg_remove_sw_break(unsigned long addr) 398 { 399 int i; 400 401 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 402 if ((kgdb_break[i].state == BP_SET) && 403 (kgdb_break[i].bpt_addr == addr)) { 404 kgdb_break[i].state = BP_REMOVED; 405 return 0; 406 } 407 } 408 return -ENOENT; 409 } 410 411 int kgdb_isremovedbreak(unsigned long addr) 412 { 413 int i; 414 415 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 416 if ((kgdb_break[i].state == BP_REMOVED) && 417 (kgdb_break[i].bpt_addr == addr)) 418 return 1; 419 } 420 return 0; 421 } 422 423 int kgdb_has_hit_break(unsigned long addr) 424 { 425 int i; 426 427 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 428 if (kgdb_break[i].state == BP_ACTIVE && 429 kgdb_break[i].bpt_addr == addr) 430 return 1; 431 } 432 return 0; 433 } 434 435 int dbg_remove_all_break(void) 436 { 437 int error; 438 int i; 439 440 /* Clear memory breakpoints. */ 441 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 442 if (kgdb_break[i].state != BP_ACTIVE) 443 goto setundefined; 444 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); 445 if (error) 446 pr_err("breakpoint remove failed: %lx\n", 447 kgdb_break[i].bpt_addr); 448 setundefined: 449 kgdb_break[i].state = BP_UNDEFINED; 450 } 451 452 /* Clear hardware breakpoints. */ 453 if (arch_kgdb_ops.remove_all_hw_break) 454 arch_kgdb_ops.remove_all_hw_break(); 455 456 return 0; 457 } 458 459 #ifdef CONFIG_KGDB_KDB 460 void kdb_dump_stack_on_cpu(int cpu) 461 { 462 if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) { 463 dump_stack(); 464 return; 465 } 466 467 if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) { 468 kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n", 469 cpu); 470 return; 471 } 472 473 /* 474 * In general, architectures don't support dumping the stack of a 475 * "running" process that's not the current one. From the point of 476 * view of the Linux, kernel processes that are looping in the kgdb 477 * slave loop are still "running". There's also no API (that actually 478 * works across all architectures) that can do a stack crawl based 479 * on registers passed as a parameter. 480 * 481 * Solve this conundrum by asking slave CPUs to do the backtrace 482 * themselves. 483 */ 484 kgdb_info[cpu].exception_state |= DCPU_WANT_BT; 485 while (kgdb_info[cpu].exception_state & DCPU_WANT_BT) 486 cpu_relax(); 487 } 488 #endif 489 490 /* 491 * Return true if there is a valid kgdb I/O module. Also if no 492 * debugger is attached a message can be printed to the console about 493 * waiting for the debugger to attach. 494 * 495 * The print_wait argument is only to be true when called from inside 496 * the core kgdb_handle_exception, because it will wait for the 497 * debugger to attach. 498 */ 499 static int kgdb_io_ready(int print_wait) 500 { 501 if (!dbg_io_ops) 502 return 0; 503 if (kgdb_connected) 504 return 1; 505 if (atomic_read(&kgdb_setting_breakpoint)) 506 return 1; 507 if (print_wait) { 508 #ifdef CONFIG_KGDB_KDB 509 if (!dbg_kdb_mode) 510 pr_crit("waiting... or $3#33 for KDB\n"); 511 #else 512 pr_crit("Waiting for remote debugger\n"); 513 #endif 514 } 515 return 1; 516 } 517 NOKPROBE_SYMBOL(kgdb_io_ready); 518 519 static int kgdb_reenter_check(struct kgdb_state *ks) 520 { 521 unsigned long addr; 522 523 if (atomic_read(&kgdb_active) != raw_smp_processor_id()) 524 return 0; 525 526 /* Panic on recursive debugger calls: */ 527 exception_level++; 528 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs); 529 dbg_deactivate_sw_breakpoints(); 530 531 /* 532 * If the break point removed ok at the place exception 533 * occurred, try to recover and print a warning to the end 534 * user because the user planted a breakpoint in a place that 535 * KGDB needs in order to function. 536 */ 537 if (dbg_remove_sw_break(addr) == 0) { 538 exception_level = 0; 539 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 540 dbg_activate_sw_breakpoints(); 541 pr_crit("re-enter error: breakpoint removed %lx\n", addr); 542 WARN_ON_ONCE(1); 543 544 return 1; 545 } 546 dbg_remove_all_break(); 547 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 548 549 if (exception_level > 1) { 550 dump_stack(); 551 kgdb_io_module_registered = false; 552 panic("Recursive entry to debugger"); 553 } 554 555 pr_crit("re-enter exception: ALL breakpoints killed\n"); 556 #ifdef CONFIG_KGDB_KDB 557 /* Allow kdb to debug itself one level */ 558 return 0; 559 #endif 560 dump_stack(); 561 panic("Recursive entry to debugger"); 562 563 return 1; 564 } 565 NOKPROBE_SYMBOL(kgdb_reenter_check); 566 567 static void dbg_touch_watchdogs(void) 568 { 569 touch_softlockup_watchdog_sync(); 570 clocksource_touch_watchdog(); 571 rcu_cpu_stall_reset(); 572 } 573 NOKPROBE_SYMBOL(dbg_touch_watchdogs); 574 575 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, 576 int exception_state) 577 { 578 unsigned long flags; 579 int sstep_tries = 100; 580 int error; 581 int cpu; 582 int trace_on = 0; 583 int online_cpus = num_online_cpus(); 584 u64 time_left; 585 586 kgdb_info[ks->cpu].enter_kgdb++; 587 kgdb_info[ks->cpu].exception_state |= exception_state; 588 589 if (exception_state == DCPU_WANT_MASTER) 590 atomic_inc(&masters_in_kgdb); 591 else 592 atomic_inc(&slaves_in_kgdb); 593 594 if (arch_kgdb_ops.disable_hw_break) 595 arch_kgdb_ops.disable_hw_break(regs); 596 597 acquirelock: 598 rcu_read_lock(); 599 /* 600 * Interrupts will be restored by the 'trap return' code, except when 601 * single stepping. 602 */ 603 local_irq_save(flags); 604 605 cpu = ks->cpu; 606 kgdb_info[cpu].debuggerinfo = regs; 607 kgdb_info[cpu].task = current; 608 kgdb_info[cpu].ret_state = 0; 609 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT; 610 611 /* Make sure the above info reaches the primary CPU */ 612 smp_mb(); 613 614 if (exception_level == 1) { 615 if (raw_spin_trylock(&dbg_master_lock)) 616 atomic_xchg(&kgdb_active, cpu); 617 goto cpu_master_loop; 618 } 619 620 /* 621 * CPU will loop if it is a slave or request to become a kgdb 622 * master cpu and acquire the kgdb_active lock: 623 */ 624 while (1) { 625 cpu_loop: 626 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) { 627 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER; 628 goto cpu_master_loop; 629 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) { 630 if (raw_spin_trylock(&dbg_master_lock)) { 631 atomic_xchg(&kgdb_active, cpu); 632 break; 633 } 634 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) { 635 dump_stack(); 636 kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT; 637 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) { 638 if (!raw_spin_is_locked(&dbg_slave_lock)) 639 goto return_normal; 640 } else { 641 return_normal: 642 /* Return to normal operation by executing any 643 * hw breakpoint fixup. 644 */ 645 if (arch_kgdb_ops.correct_hw_break) 646 arch_kgdb_ops.correct_hw_break(); 647 if (trace_on) 648 tracing_on(); 649 kgdb_info[cpu].debuggerinfo = NULL; 650 kgdb_info[cpu].task = NULL; 651 kgdb_info[cpu].exception_state &= 652 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 653 kgdb_info[cpu].enter_kgdb--; 654 smp_mb__before_atomic(); 655 atomic_dec(&slaves_in_kgdb); 656 dbg_touch_watchdogs(); 657 local_irq_restore(flags); 658 rcu_read_unlock(); 659 return 0; 660 } 661 cpu_relax(); 662 } 663 664 /* 665 * For single stepping, try to only enter on the processor 666 * that was single stepping. To guard against a deadlock, the 667 * kernel will only try for the value of sstep_tries before 668 * giving up and continuing on. 669 */ 670 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 && 671 (kgdb_info[cpu].task && 672 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) { 673 atomic_set(&kgdb_active, -1); 674 raw_spin_unlock(&dbg_master_lock); 675 dbg_touch_watchdogs(); 676 local_irq_restore(flags); 677 rcu_read_unlock(); 678 679 goto acquirelock; 680 } 681 682 if (!kgdb_io_ready(1)) { 683 kgdb_info[cpu].ret_state = 1; 684 goto kgdb_restore; /* No I/O connection, resume the system */ 685 } 686 687 /* 688 * Don't enter if we have hit a removed breakpoint. 689 */ 690 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs)) 691 goto kgdb_restore; 692 693 atomic_inc(&ignore_console_lock_warning); 694 695 /* Call the I/O driver's pre_exception routine */ 696 if (dbg_io_ops->pre_exception) 697 dbg_io_ops->pre_exception(); 698 699 /* 700 * Get the passive CPU lock which will hold all the non-primary 701 * CPU in a spin state while the debugger is active 702 */ 703 if (!kgdb_single_step) 704 raw_spin_lock(&dbg_slave_lock); 705 706 #ifdef CONFIG_SMP 707 /* If send_ready set, slaves are already waiting */ 708 if (ks->send_ready) 709 atomic_set(ks->send_ready, 1); 710 711 /* Signal the other CPUs to enter kgdb_wait() */ 712 else if ((!kgdb_single_step) && kgdb_do_roundup) 713 kgdb_roundup_cpus(); 714 #endif 715 716 /* 717 * Wait for the other CPUs to be notified and be waiting for us: 718 */ 719 time_left = MSEC_PER_SEC; 720 while (kgdb_do_roundup && --time_left && 721 (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) != 722 online_cpus) 723 udelay(1000); 724 if (!time_left) 725 pr_crit("Timed out waiting for secondary CPUs.\n"); 726 727 /* 728 * At this point the primary processor is completely 729 * in the debugger and all secondary CPUs are quiescent 730 */ 731 dbg_deactivate_sw_breakpoints(); 732 kgdb_single_step = 0; 733 kgdb_contthread = current; 734 exception_level = 0; 735 trace_on = tracing_is_on(); 736 if (trace_on) 737 tracing_off(); 738 739 while (1) { 740 cpu_master_loop: 741 if (dbg_kdb_mode) { 742 kgdb_connected = 1; 743 error = kdb_stub(ks); 744 if (error == -1) 745 continue; 746 kgdb_connected = 0; 747 } else { 748 error = gdb_serial_stub(ks); 749 } 750 751 if (error == DBG_PASS_EVENT) { 752 dbg_kdb_mode = !dbg_kdb_mode; 753 } else if (error == DBG_SWITCH_CPU_EVENT) { 754 kgdb_info[dbg_switch_cpu].exception_state |= 755 DCPU_NEXT_MASTER; 756 goto cpu_loop; 757 } else { 758 kgdb_info[cpu].ret_state = error; 759 break; 760 } 761 } 762 763 dbg_activate_sw_breakpoints(); 764 765 /* Call the I/O driver's post_exception routine */ 766 if (dbg_io_ops->post_exception) 767 dbg_io_ops->post_exception(); 768 769 atomic_dec(&ignore_console_lock_warning); 770 771 if (!kgdb_single_step) { 772 raw_spin_unlock(&dbg_slave_lock); 773 /* Wait till all the CPUs have quit from the debugger. */ 774 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb)) 775 cpu_relax(); 776 } 777 778 kgdb_restore: 779 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) { 780 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step); 781 if (kgdb_info[sstep_cpu].task) 782 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid; 783 else 784 kgdb_sstep_pid = 0; 785 } 786 if (arch_kgdb_ops.correct_hw_break) 787 arch_kgdb_ops.correct_hw_break(); 788 if (trace_on) 789 tracing_on(); 790 791 kgdb_info[cpu].debuggerinfo = NULL; 792 kgdb_info[cpu].task = NULL; 793 kgdb_info[cpu].exception_state &= 794 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 795 kgdb_info[cpu].enter_kgdb--; 796 smp_mb__before_atomic(); 797 atomic_dec(&masters_in_kgdb); 798 /* Free kgdb_active */ 799 atomic_set(&kgdb_active, -1); 800 raw_spin_unlock(&dbg_master_lock); 801 dbg_touch_watchdogs(); 802 local_irq_restore(flags); 803 rcu_read_unlock(); 804 805 return kgdb_info[cpu].ret_state; 806 } 807 NOKPROBE_SYMBOL(kgdb_cpu_enter); 808 809 /* 810 * kgdb_handle_exception() - main entry point from a kernel exception 811 * 812 * Locking hierarchy: 813 * interface locks, if any (begin_session) 814 * kgdb lock (kgdb_active) 815 */ 816 int 817 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 818 { 819 struct kgdb_state kgdb_var; 820 struct kgdb_state *ks = &kgdb_var; 821 int ret = 0; 822 823 if (arch_kgdb_ops.enable_nmi) 824 arch_kgdb_ops.enable_nmi(0); 825 /* 826 * Avoid entering the debugger if we were triggered due to an oops 827 * but panic_timeout indicates the system should automatically 828 * reboot on panic. We don't want to get stuck waiting for input 829 * on such systems, especially if its "just" an oops. 830 */ 831 if (signo != SIGTRAP && panic_timeout) 832 return 1; 833 834 memset(ks, 0, sizeof(struct kgdb_state)); 835 ks->cpu = raw_smp_processor_id(); 836 ks->ex_vector = evector; 837 ks->signo = signo; 838 ks->err_code = ecode; 839 ks->linux_regs = regs; 840 841 if (kgdb_reenter_check(ks)) 842 goto out; /* Ouch, double exception ! */ 843 if (kgdb_info[ks->cpu].enter_kgdb != 0) 844 goto out; 845 846 ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 847 out: 848 if (arch_kgdb_ops.enable_nmi) 849 arch_kgdb_ops.enable_nmi(1); 850 return ret; 851 } 852 NOKPROBE_SYMBOL(kgdb_handle_exception); 853 854 /* 855 * GDB places a breakpoint at this function to know dynamically loaded objects. 856 */ 857 static int module_event(struct notifier_block *self, unsigned long val, 858 void *data) 859 { 860 return 0; 861 } 862 863 static struct notifier_block dbg_module_load_nb = { 864 .notifier_call = module_event, 865 }; 866 867 int kgdb_nmicallback(int cpu, void *regs) 868 { 869 #ifdef CONFIG_SMP 870 struct kgdb_state kgdb_var; 871 struct kgdb_state *ks = &kgdb_var; 872 873 kgdb_info[cpu].rounding_up = false; 874 875 memset(ks, 0, sizeof(struct kgdb_state)); 876 ks->cpu = cpu; 877 ks->linux_regs = regs; 878 879 if (kgdb_info[ks->cpu].enter_kgdb == 0 && 880 raw_spin_is_locked(&dbg_master_lock)) { 881 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE); 882 return 0; 883 } 884 #endif 885 return 1; 886 } 887 NOKPROBE_SYMBOL(kgdb_nmicallback); 888 889 int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code, 890 atomic_t *send_ready) 891 { 892 #ifdef CONFIG_SMP 893 if (!kgdb_io_ready(0) || !send_ready) 894 return 1; 895 896 if (kgdb_info[cpu].enter_kgdb == 0) { 897 struct kgdb_state kgdb_var; 898 struct kgdb_state *ks = &kgdb_var; 899 900 memset(ks, 0, sizeof(struct kgdb_state)); 901 ks->cpu = cpu; 902 ks->ex_vector = trapnr; 903 ks->signo = SIGTRAP; 904 ks->err_code = err_code; 905 ks->linux_regs = regs; 906 ks->send_ready = send_ready; 907 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 908 return 0; 909 } 910 #endif 911 return 1; 912 } 913 NOKPROBE_SYMBOL(kgdb_nmicallin); 914 915 static void kgdb_console_write(struct console *co, const char *s, 916 unsigned count) 917 { 918 unsigned long flags; 919 920 /* If we're debugging, or KGDB has not connected, don't try 921 * and print. */ 922 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode) 923 return; 924 925 local_irq_save(flags); 926 gdbstub_msg_write(s, count); 927 local_irq_restore(flags); 928 } 929 930 static struct console kgdbcons = { 931 .name = "kgdb", 932 .write = kgdb_console_write, 933 .flags = CON_PRINTBUFFER | CON_ENABLED, 934 .index = -1, 935 }; 936 937 static int __init opt_kgdb_con(char *str) 938 { 939 kgdb_use_con = 1; 940 941 if (kgdb_io_module_registered && !kgdb_con_registered) { 942 register_console(&kgdbcons); 943 kgdb_con_registered = 1; 944 } 945 946 return 0; 947 } 948 949 early_param("kgdbcon", opt_kgdb_con); 950 951 #ifdef CONFIG_MAGIC_SYSRQ 952 static void sysrq_handle_dbg(int key) 953 { 954 if (!dbg_io_ops) { 955 pr_crit("ERROR: No KGDB I/O module available\n"); 956 return; 957 } 958 if (!kgdb_connected) { 959 #ifdef CONFIG_KGDB_KDB 960 if (!dbg_kdb_mode) 961 pr_crit("KGDB or $3#33 for KDB\n"); 962 #else 963 pr_crit("Entering KGDB\n"); 964 #endif 965 } 966 967 kgdb_breakpoint(); 968 } 969 970 static const struct sysrq_key_op sysrq_dbg_op = { 971 .handler = sysrq_handle_dbg, 972 .help_msg = "debug(g)", 973 .action_msg = "DEBUG", 974 }; 975 #endif 976 977 void kgdb_panic(const char *msg) 978 { 979 if (!kgdb_io_module_registered) 980 return; 981 982 /* 983 * We don't want to get stuck waiting for input from user if 984 * "panic_timeout" indicates the system should automatically 985 * reboot on panic. 986 */ 987 if (panic_timeout) 988 return; 989 990 if (dbg_kdb_mode) 991 kdb_printf("PANIC: %s\n", msg); 992 993 kgdb_breakpoint(); 994 } 995 996 static void kgdb_initial_breakpoint(void) 997 { 998 kgdb_break_asap = 0; 999 1000 pr_crit("Waiting for connection from remote gdb...\n"); 1001 kgdb_breakpoint(); 1002 } 1003 1004 void __weak kgdb_arch_late(void) 1005 { 1006 } 1007 1008 void __init dbg_late_init(void) 1009 { 1010 dbg_is_early = false; 1011 if (kgdb_io_module_registered) 1012 kgdb_arch_late(); 1013 kdb_init(KDB_INIT_FULL); 1014 1015 if (kgdb_io_module_registered && kgdb_break_asap) 1016 kgdb_initial_breakpoint(); 1017 } 1018 1019 static int 1020 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x) 1021 { 1022 /* 1023 * Take the following action on reboot notify depending on value: 1024 * 1 == Enter debugger 1025 * 0 == [the default] detatch debug client 1026 * -1 == Do nothing... and use this until the board resets 1027 */ 1028 switch (kgdbreboot) { 1029 case 1: 1030 kgdb_breakpoint(); 1031 case -1: 1032 goto done; 1033 } 1034 if (!dbg_kdb_mode) 1035 gdbstub_exit(code); 1036 done: 1037 return NOTIFY_DONE; 1038 } 1039 1040 static struct notifier_block dbg_reboot_notifier = { 1041 .notifier_call = dbg_notify_reboot, 1042 .next = NULL, 1043 .priority = INT_MAX, 1044 }; 1045 1046 static void kgdb_register_callbacks(void) 1047 { 1048 if (!kgdb_io_module_registered) { 1049 kgdb_io_module_registered = 1; 1050 kgdb_arch_init(); 1051 if (!dbg_is_early) 1052 kgdb_arch_late(); 1053 register_module_notifier(&dbg_module_load_nb); 1054 register_reboot_notifier(&dbg_reboot_notifier); 1055 #ifdef CONFIG_MAGIC_SYSRQ 1056 register_sysrq_key('g', &sysrq_dbg_op); 1057 #endif 1058 if (kgdb_use_con && !kgdb_con_registered) { 1059 register_console(&kgdbcons); 1060 kgdb_con_registered = 1; 1061 } 1062 } 1063 } 1064 1065 static void kgdb_unregister_callbacks(void) 1066 { 1067 /* 1068 * When this routine is called KGDB should unregister from 1069 * handlers and clean up, making sure it is not handling any 1070 * break exceptions at the time. 1071 */ 1072 if (kgdb_io_module_registered) { 1073 kgdb_io_module_registered = 0; 1074 unregister_reboot_notifier(&dbg_reboot_notifier); 1075 unregister_module_notifier(&dbg_module_load_nb); 1076 kgdb_arch_exit(); 1077 #ifdef CONFIG_MAGIC_SYSRQ 1078 unregister_sysrq_key('g', &sysrq_dbg_op); 1079 #endif 1080 if (kgdb_con_registered) { 1081 unregister_console(&kgdbcons); 1082 kgdb_con_registered = 0; 1083 } 1084 } 1085 } 1086 1087 /* 1088 * There are times a tasklet needs to be used vs a compiled in 1089 * break point so as to cause an exception outside a kgdb I/O module, 1090 * such as is the case with kgdboe, where calling a breakpoint in the 1091 * I/O driver itself would be fatal. 1092 */ 1093 static void kgdb_tasklet_bpt(unsigned long ing) 1094 { 1095 kgdb_breakpoint(); 1096 atomic_set(&kgdb_break_tasklet_var, 0); 1097 } 1098 1099 static DECLARE_TASKLET_OLD(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt); 1100 1101 void kgdb_schedule_breakpoint(void) 1102 { 1103 if (atomic_read(&kgdb_break_tasklet_var) || 1104 atomic_read(&kgdb_active) != -1 || 1105 atomic_read(&kgdb_setting_breakpoint)) 1106 return; 1107 atomic_inc(&kgdb_break_tasklet_var); 1108 tasklet_schedule(&kgdb_tasklet_breakpoint); 1109 } 1110 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint); 1111 1112 /** 1113 * kgdb_register_io_module - register KGDB IO module 1114 * @new_dbg_io_ops: the io ops vector 1115 * 1116 * Register it with the KGDB core. 1117 */ 1118 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) 1119 { 1120 struct kgdb_io *old_dbg_io_ops; 1121 int err; 1122 1123 spin_lock(&kgdb_registration_lock); 1124 1125 old_dbg_io_ops = dbg_io_ops; 1126 if (old_dbg_io_ops) { 1127 if (!old_dbg_io_ops->deinit) { 1128 spin_unlock(&kgdb_registration_lock); 1129 1130 pr_err("KGDB I/O driver %s can't replace %s.\n", 1131 new_dbg_io_ops->name, old_dbg_io_ops->name); 1132 return -EBUSY; 1133 } 1134 pr_info("Replacing I/O driver %s with %s\n", 1135 old_dbg_io_ops->name, new_dbg_io_ops->name); 1136 } 1137 1138 if (new_dbg_io_ops->init) { 1139 err = new_dbg_io_ops->init(); 1140 if (err) { 1141 spin_unlock(&kgdb_registration_lock); 1142 return err; 1143 } 1144 } 1145 1146 dbg_io_ops = new_dbg_io_ops; 1147 1148 spin_unlock(&kgdb_registration_lock); 1149 1150 if (old_dbg_io_ops) { 1151 old_dbg_io_ops->deinit(); 1152 return 0; 1153 } 1154 1155 pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name); 1156 1157 /* Arm KGDB now. */ 1158 kgdb_register_callbacks(); 1159 1160 if (kgdb_break_asap && 1161 (!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))) 1162 kgdb_initial_breakpoint(); 1163 1164 return 0; 1165 } 1166 EXPORT_SYMBOL_GPL(kgdb_register_io_module); 1167 1168 /** 1169 * kkgdb_unregister_io_module - unregister KGDB IO module 1170 * @old_dbg_io_ops: the io ops vector 1171 * 1172 * Unregister it with the KGDB core. 1173 */ 1174 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops) 1175 { 1176 BUG_ON(kgdb_connected); 1177 1178 /* 1179 * KGDB is no longer able to communicate out, so 1180 * unregister our callbacks and reset state. 1181 */ 1182 kgdb_unregister_callbacks(); 1183 1184 spin_lock(&kgdb_registration_lock); 1185 1186 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops); 1187 dbg_io_ops = NULL; 1188 1189 spin_unlock(&kgdb_registration_lock); 1190 1191 if (old_dbg_io_ops->deinit) 1192 old_dbg_io_ops->deinit(); 1193 1194 pr_info("Unregistered I/O driver %s, debugger disabled\n", 1195 old_dbg_io_ops->name); 1196 } 1197 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module); 1198 1199 int dbg_io_get_char(void) 1200 { 1201 int ret = dbg_io_ops->read_char(); 1202 if (ret == NO_POLL_CHAR) 1203 return -1; 1204 if (!dbg_kdb_mode) 1205 return ret; 1206 if (ret == 127) 1207 return 8; 1208 return ret; 1209 } 1210 1211 /** 1212 * kgdb_breakpoint - generate breakpoint exception 1213 * 1214 * This function will generate a breakpoint exception. It is used at the 1215 * beginning of a program to sync up with a debugger and can be used 1216 * otherwise as a quick means to stop program execution and "break" into 1217 * the debugger. 1218 */ 1219 noinline void kgdb_breakpoint(void) 1220 { 1221 atomic_inc(&kgdb_setting_breakpoint); 1222 wmb(); /* Sync point before breakpoint */ 1223 arch_kgdb_breakpoint(); 1224 wmb(); /* Sync point after breakpoint */ 1225 atomic_dec(&kgdb_setting_breakpoint); 1226 } 1227 EXPORT_SYMBOL_GPL(kgdb_breakpoint); 1228 1229 static int __init opt_kgdb_wait(char *str) 1230 { 1231 kgdb_break_asap = 1; 1232 1233 kdb_init(KDB_INIT_EARLY); 1234 if (kgdb_io_module_registered && 1235 IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)) 1236 kgdb_initial_breakpoint(); 1237 1238 return 0; 1239 } 1240 1241 early_param("kgdbwait", opt_kgdb_wait); 1242