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 #include <linux/pid_namespace.h> 31 #include <linux/clocksource.h> 32 #include <linux/interrupt.h> 33 #include <linux/spinlock.h> 34 #include <linux/console.h> 35 #include <linux/threads.h> 36 #include <linux/uaccess.h> 37 #include <linux/kernel.h> 38 #include <linux/module.h> 39 #include <linux/ptrace.h> 40 #include <linux/string.h> 41 #include <linux/delay.h> 42 #include <linux/sched.h> 43 #include <linux/sysrq.h> 44 #include <linux/init.h> 45 #include <linux/kgdb.h> 46 #include <linux/kdb.h> 47 #include <linux/pid.h> 48 #include <linux/smp.h> 49 #include <linux/mm.h> 50 #include <linux/rcupdate.h> 51 52 #include <asm/cacheflush.h> 53 #include <asm/byteorder.h> 54 #include <linux/atomic.h> 55 56 #include "debug_core.h" 57 58 static int kgdb_break_asap; 59 60 struct debuggerinfo_struct kgdb_info[NR_CPUS]; 61 62 /** 63 * kgdb_connected - Is a host GDB connected to us? 64 */ 65 int kgdb_connected; 66 EXPORT_SYMBOL_GPL(kgdb_connected); 67 68 /* All the KGDB handlers are installed */ 69 int kgdb_io_module_registered; 70 71 /* Guard for recursive entry */ 72 static int exception_level; 73 74 struct kgdb_io *dbg_io_ops; 75 static DEFINE_SPINLOCK(kgdb_registration_lock); 76 77 /* kgdb console driver is loaded */ 78 static int kgdb_con_registered; 79 /* determine if kgdb console output should be used */ 80 static int kgdb_use_con; 81 /* Flag for alternate operations for early debugging */ 82 bool dbg_is_early = true; 83 /* Next cpu to become the master debug core */ 84 int dbg_switch_cpu; 85 86 /* Use kdb or gdbserver mode */ 87 int dbg_kdb_mode = 1; 88 89 static int __init opt_kgdb_con(char *str) 90 { 91 kgdb_use_con = 1; 92 return 0; 93 } 94 95 early_param("kgdbcon", opt_kgdb_con); 96 97 module_param(kgdb_use_con, int, 0644); 98 99 /* 100 * Holds information about breakpoints in a kernel. These breakpoints are 101 * added and removed by gdb. 102 */ 103 static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = { 104 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED } 105 }; 106 107 /* 108 * The CPU# of the active CPU, or -1 if none: 109 */ 110 atomic_t kgdb_active = ATOMIC_INIT(-1); 111 EXPORT_SYMBOL_GPL(kgdb_active); 112 static DEFINE_RAW_SPINLOCK(dbg_master_lock); 113 static DEFINE_RAW_SPINLOCK(dbg_slave_lock); 114 115 /* 116 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early 117 * bootup code (which might not have percpu set up yet): 118 */ 119 static atomic_t masters_in_kgdb; 120 static atomic_t slaves_in_kgdb; 121 static atomic_t kgdb_break_tasklet_var; 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 overriden by architectures when needed: 158 */ 159 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr) 160 { 161 int err; 162 163 err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE); 164 if (err) 165 return err; 166 167 return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr, 168 BREAK_INSTR_SIZE); 169 } 170 171 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle) 172 { 173 return probe_kernel_write((char *)addr, 174 (char *)bundle, BREAK_INSTR_SIZE); 175 } 176 177 int __weak kgdb_validate_break_address(unsigned long addr) 178 { 179 char tmp_variable[BREAK_INSTR_SIZE]; 180 int err; 181 /* Validate setting the breakpoint and then removing it. In the 182 * remove fails, the kernel needs to emit a bad message because we 183 * are deep trouble not being able to put things back the way we 184 * found them. 185 */ 186 err = kgdb_arch_set_breakpoint(addr, tmp_variable); 187 if (err) 188 return err; 189 err = kgdb_arch_remove_breakpoint(addr, tmp_variable); 190 if (err) 191 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel " 192 "memory destroyed at: %lx", addr); 193 return err; 194 } 195 196 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs) 197 { 198 return instruction_pointer(regs); 199 } 200 201 int __weak kgdb_arch_init(void) 202 { 203 return 0; 204 } 205 206 int __weak kgdb_skipexception(int exception, struct pt_regs *regs) 207 { 208 return 0; 209 } 210 211 /* 212 * Some architectures need cache flushes when we set/clear a 213 * breakpoint: 214 */ 215 static void kgdb_flush_swbreak_addr(unsigned long addr) 216 { 217 if (!CACHE_FLUSH_IS_SAFE) 218 return; 219 220 if (current->mm && current->mm->mmap_cache) { 221 flush_cache_range(current->mm->mmap_cache, 222 addr, addr + BREAK_INSTR_SIZE); 223 } 224 /* Force flush instruction cache if it was outside the mm */ 225 flush_icache_range(addr, addr + BREAK_INSTR_SIZE); 226 } 227 228 /* 229 * SW breakpoint management: 230 */ 231 int dbg_activate_sw_breakpoints(void) 232 { 233 unsigned long addr; 234 int error; 235 int ret = 0; 236 int i; 237 238 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 239 if (kgdb_break[i].state != BP_SET) 240 continue; 241 242 addr = kgdb_break[i].bpt_addr; 243 error = kgdb_arch_set_breakpoint(addr, 244 kgdb_break[i].saved_instr); 245 if (error) { 246 ret = error; 247 printk(KERN_INFO "KGDB: BP install failed: %lx", addr); 248 continue; 249 } 250 251 kgdb_flush_swbreak_addr(addr); 252 kgdb_break[i].state = BP_ACTIVE; 253 } 254 return ret; 255 } 256 257 int dbg_set_sw_break(unsigned long addr) 258 { 259 int err = kgdb_validate_break_address(addr); 260 int breakno = -1; 261 int i; 262 263 if (err) 264 return err; 265 266 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 267 if ((kgdb_break[i].state == BP_SET) && 268 (kgdb_break[i].bpt_addr == addr)) 269 return -EEXIST; 270 } 271 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 272 if (kgdb_break[i].state == BP_REMOVED && 273 kgdb_break[i].bpt_addr == addr) { 274 breakno = i; 275 break; 276 } 277 } 278 279 if (breakno == -1) { 280 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 281 if (kgdb_break[i].state == BP_UNDEFINED) { 282 breakno = i; 283 break; 284 } 285 } 286 } 287 288 if (breakno == -1) 289 return -E2BIG; 290 291 kgdb_break[breakno].state = BP_SET; 292 kgdb_break[breakno].type = BP_BREAKPOINT; 293 kgdb_break[breakno].bpt_addr = addr; 294 295 return 0; 296 } 297 298 int dbg_deactivate_sw_breakpoints(void) 299 { 300 unsigned long addr; 301 int error; 302 int ret = 0; 303 int i; 304 305 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 306 if (kgdb_break[i].state != BP_ACTIVE) 307 continue; 308 addr = kgdb_break[i].bpt_addr; 309 error = kgdb_arch_remove_breakpoint(addr, 310 kgdb_break[i].saved_instr); 311 if (error) { 312 printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr); 313 ret = error; 314 } 315 316 kgdb_flush_swbreak_addr(addr); 317 kgdb_break[i].state = BP_SET; 318 } 319 return ret; 320 } 321 322 int dbg_remove_sw_break(unsigned long addr) 323 { 324 int i; 325 326 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 327 if ((kgdb_break[i].state == BP_SET) && 328 (kgdb_break[i].bpt_addr == addr)) { 329 kgdb_break[i].state = BP_REMOVED; 330 return 0; 331 } 332 } 333 return -ENOENT; 334 } 335 336 int kgdb_isremovedbreak(unsigned long addr) 337 { 338 int i; 339 340 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 341 if ((kgdb_break[i].state == BP_REMOVED) && 342 (kgdb_break[i].bpt_addr == addr)) 343 return 1; 344 } 345 return 0; 346 } 347 348 int dbg_remove_all_break(void) 349 { 350 unsigned long addr; 351 int error; 352 int i; 353 354 /* Clear memory breakpoints. */ 355 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 356 if (kgdb_break[i].state != BP_ACTIVE) 357 goto setundefined; 358 addr = kgdb_break[i].bpt_addr; 359 error = kgdb_arch_remove_breakpoint(addr, 360 kgdb_break[i].saved_instr); 361 if (error) 362 printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n", 363 addr); 364 setundefined: 365 kgdb_break[i].state = BP_UNDEFINED; 366 } 367 368 /* Clear hardware breakpoints. */ 369 if (arch_kgdb_ops.remove_all_hw_break) 370 arch_kgdb_ops.remove_all_hw_break(); 371 372 return 0; 373 } 374 375 /* 376 * Return true if there is a valid kgdb I/O module. Also if no 377 * debugger is attached a message can be printed to the console about 378 * waiting for the debugger to attach. 379 * 380 * The print_wait argument is only to be true when called from inside 381 * the core kgdb_handle_exception, because it will wait for the 382 * debugger to attach. 383 */ 384 static int kgdb_io_ready(int print_wait) 385 { 386 if (!dbg_io_ops) 387 return 0; 388 if (kgdb_connected) 389 return 1; 390 if (atomic_read(&kgdb_setting_breakpoint)) 391 return 1; 392 if (print_wait) { 393 #ifdef CONFIG_KGDB_KDB 394 if (!dbg_kdb_mode) 395 printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n"); 396 #else 397 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n"); 398 #endif 399 } 400 return 1; 401 } 402 403 static int kgdb_reenter_check(struct kgdb_state *ks) 404 { 405 unsigned long addr; 406 407 if (atomic_read(&kgdb_active) != raw_smp_processor_id()) 408 return 0; 409 410 /* Panic on recursive debugger calls: */ 411 exception_level++; 412 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs); 413 dbg_deactivate_sw_breakpoints(); 414 415 /* 416 * If the break point removed ok at the place exception 417 * occurred, try to recover and print a warning to the end 418 * user because the user planted a breakpoint in a place that 419 * KGDB needs in order to function. 420 */ 421 if (dbg_remove_sw_break(addr) == 0) { 422 exception_level = 0; 423 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 424 dbg_activate_sw_breakpoints(); 425 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n", 426 addr); 427 WARN_ON_ONCE(1); 428 429 return 1; 430 } 431 dbg_remove_all_break(); 432 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 433 434 if (exception_level > 1) { 435 dump_stack(); 436 panic("Recursive entry to debugger"); 437 } 438 439 printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n"); 440 #ifdef CONFIG_KGDB_KDB 441 /* Allow kdb to debug itself one level */ 442 return 0; 443 #endif 444 dump_stack(); 445 panic("Recursive entry to debugger"); 446 447 return 1; 448 } 449 450 static void dbg_touch_watchdogs(void) 451 { 452 touch_softlockup_watchdog_sync(); 453 clocksource_touch_watchdog(); 454 rcu_cpu_stall_reset(); 455 } 456 457 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, 458 int exception_state) 459 { 460 unsigned long flags; 461 int sstep_tries = 100; 462 int error; 463 int cpu; 464 int trace_on = 0; 465 int online_cpus = num_online_cpus(); 466 467 kgdb_info[ks->cpu].enter_kgdb++; 468 kgdb_info[ks->cpu].exception_state |= exception_state; 469 470 if (exception_state == DCPU_WANT_MASTER) 471 atomic_inc(&masters_in_kgdb); 472 else 473 atomic_inc(&slaves_in_kgdb); 474 475 if (arch_kgdb_ops.disable_hw_break) 476 arch_kgdb_ops.disable_hw_break(regs); 477 478 acquirelock: 479 /* 480 * Interrupts will be restored by the 'trap return' code, except when 481 * single stepping. 482 */ 483 local_irq_save(flags); 484 485 cpu = ks->cpu; 486 kgdb_info[cpu].debuggerinfo = regs; 487 kgdb_info[cpu].task = current; 488 kgdb_info[cpu].ret_state = 0; 489 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT; 490 491 /* Make sure the above info reaches the primary CPU */ 492 smp_mb(); 493 494 if (exception_level == 1) { 495 if (raw_spin_trylock(&dbg_master_lock)) 496 atomic_xchg(&kgdb_active, cpu); 497 goto cpu_master_loop; 498 } 499 500 /* 501 * CPU will loop if it is a slave or request to become a kgdb 502 * master cpu and acquire the kgdb_active lock: 503 */ 504 while (1) { 505 cpu_loop: 506 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) { 507 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER; 508 goto cpu_master_loop; 509 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) { 510 if (raw_spin_trylock(&dbg_master_lock)) { 511 atomic_xchg(&kgdb_active, cpu); 512 break; 513 } 514 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) { 515 if (!raw_spin_is_locked(&dbg_slave_lock)) 516 goto return_normal; 517 } else { 518 return_normal: 519 /* Return to normal operation by executing any 520 * hw breakpoint fixup. 521 */ 522 if (arch_kgdb_ops.correct_hw_break) 523 arch_kgdb_ops.correct_hw_break(); 524 if (trace_on) 525 tracing_on(); 526 kgdb_info[cpu].exception_state &= 527 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 528 kgdb_info[cpu].enter_kgdb--; 529 smp_mb__before_atomic_dec(); 530 atomic_dec(&slaves_in_kgdb); 531 dbg_touch_watchdogs(); 532 local_irq_restore(flags); 533 return 0; 534 } 535 cpu_relax(); 536 } 537 538 /* 539 * For single stepping, try to only enter on the processor 540 * that was single stepping. To guard against a deadlock, the 541 * kernel will only try for the value of sstep_tries before 542 * giving up and continuing on. 543 */ 544 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 && 545 (kgdb_info[cpu].task && 546 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) { 547 atomic_set(&kgdb_active, -1); 548 raw_spin_unlock(&dbg_master_lock); 549 dbg_touch_watchdogs(); 550 local_irq_restore(flags); 551 552 goto acquirelock; 553 } 554 555 if (!kgdb_io_ready(1)) { 556 kgdb_info[cpu].ret_state = 1; 557 goto kgdb_restore; /* No I/O connection, resume the system */ 558 } 559 560 /* 561 * Don't enter if we have hit a removed breakpoint. 562 */ 563 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs)) 564 goto kgdb_restore; 565 566 /* Call the I/O driver's pre_exception routine */ 567 if (dbg_io_ops->pre_exception) 568 dbg_io_ops->pre_exception(); 569 570 /* 571 * Get the passive CPU lock which will hold all the non-primary 572 * CPU in a spin state while the debugger is active 573 */ 574 if (!kgdb_single_step) 575 raw_spin_lock(&dbg_slave_lock); 576 577 #ifdef CONFIG_SMP 578 /* Signal the other CPUs to enter kgdb_wait() */ 579 if ((!kgdb_single_step) && kgdb_do_roundup) 580 kgdb_roundup_cpus(flags); 581 #endif 582 583 /* 584 * Wait for the other CPUs to be notified and be waiting for us: 585 */ 586 while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) + 587 atomic_read(&slaves_in_kgdb)) != online_cpus) 588 cpu_relax(); 589 590 /* 591 * At this point the primary processor is completely 592 * in the debugger and all secondary CPUs are quiescent 593 */ 594 dbg_deactivate_sw_breakpoints(); 595 kgdb_single_step = 0; 596 kgdb_contthread = current; 597 exception_level = 0; 598 trace_on = tracing_is_on(); 599 if (trace_on) 600 tracing_off(); 601 602 while (1) { 603 cpu_master_loop: 604 if (dbg_kdb_mode) { 605 kgdb_connected = 1; 606 error = kdb_stub(ks); 607 if (error == -1) 608 continue; 609 kgdb_connected = 0; 610 } else { 611 error = gdb_serial_stub(ks); 612 } 613 614 if (error == DBG_PASS_EVENT) { 615 dbg_kdb_mode = !dbg_kdb_mode; 616 } else if (error == DBG_SWITCH_CPU_EVENT) { 617 kgdb_info[dbg_switch_cpu].exception_state |= 618 DCPU_NEXT_MASTER; 619 goto cpu_loop; 620 } else { 621 kgdb_info[cpu].ret_state = error; 622 break; 623 } 624 } 625 626 /* Call the I/O driver's post_exception routine */ 627 if (dbg_io_ops->post_exception) 628 dbg_io_ops->post_exception(); 629 630 if (!kgdb_single_step) { 631 raw_spin_unlock(&dbg_slave_lock); 632 /* Wait till all the CPUs have quit from the debugger. */ 633 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb)) 634 cpu_relax(); 635 } 636 637 kgdb_restore: 638 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) { 639 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step); 640 if (kgdb_info[sstep_cpu].task) 641 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid; 642 else 643 kgdb_sstep_pid = 0; 644 } 645 if (arch_kgdb_ops.correct_hw_break) 646 arch_kgdb_ops.correct_hw_break(); 647 if (trace_on) 648 tracing_on(); 649 650 kgdb_info[cpu].exception_state &= 651 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 652 kgdb_info[cpu].enter_kgdb--; 653 smp_mb__before_atomic_dec(); 654 atomic_dec(&masters_in_kgdb); 655 /* Free kgdb_active */ 656 atomic_set(&kgdb_active, -1); 657 raw_spin_unlock(&dbg_master_lock); 658 dbg_touch_watchdogs(); 659 local_irq_restore(flags); 660 661 return kgdb_info[cpu].ret_state; 662 } 663 664 /* 665 * kgdb_handle_exception() - main entry point from a kernel exception 666 * 667 * Locking hierarchy: 668 * interface locks, if any (begin_session) 669 * kgdb lock (kgdb_active) 670 */ 671 int 672 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 673 { 674 struct kgdb_state kgdb_var; 675 struct kgdb_state *ks = &kgdb_var; 676 677 ks->cpu = raw_smp_processor_id(); 678 ks->ex_vector = evector; 679 ks->signo = signo; 680 ks->err_code = ecode; 681 ks->kgdb_usethreadid = 0; 682 ks->linux_regs = regs; 683 684 if (kgdb_reenter_check(ks)) 685 return 0; /* Ouch, double exception ! */ 686 if (kgdb_info[ks->cpu].enter_kgdb != 0) 687 return 0; 688 689 return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 690 } 691 692 int kgdb_nmicallback(int cpu, void *regs) 693 { 694 #ifdef CONFIG_SMP 695 struct kgdb_state kgdb_var; 696 struct kgdb_state *ks = &kgdb_var; 697 698 memset(ks, 0, sizeof(struct kgdb_state)); 699 ks->cpu = cpu; 700 ks->linux_regs = regs; 701 702 if (kgdb_info[ks->cpu].enter_kgdb == 0 && 703 raw_spin_is_locked(&dbg_master_lock)) { 704 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE); 705 return 0; 706 } 707 #endif 708 return 1; 709 } 710 711 static void kgdb_console_write(struct console *co, const char *s, 712 unsigned count) 713 { 714 unsigned long flags; 715 716 /* If we're debugging, or KGDB has not connected, don't try 717 * and print. */ 718 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode) 719 return; 720 721 local_irq_save(flags); 722 gdbstub_msg_write(s, count); 723 local_irq_restore(flags); 724 } 725 726 static struct console kgdbcons = { 727 .name = "kgdb", 728 .write = kgdb_console_write, 729 .flags = CON_PRINTBUFFER | CON_ENABLED, 730 .index = -1, 731 }; 732 733 #ifdef CONFIG_MAGIC_SYSRQ 734 static void sysrq_handle_dbg(int key) 735 { 736 if (!dbg_io_ops) { 737 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n"); 738 return; 739 } 740 if (!kgdb_connected) { 741 #ifdef CONFIG_KGDB_KDB 742 if (!dbg_kdb_mode) 743 printk(KERN_CRIT "KGDB or $3#33 for KDB\n"); 744 #else 745 printk(KERN_CRIT "Entering KGDB\n"); 746 #endif 747 } 748 749 kgdb_breakpoint(); 750 } 751 752 static struct sysrq_key_op sysrq_dbg_op = { 753 .handler = sysrq_handle_dbg, 754 .help_msg = "debug(G)", 755 .action_msg = "DEBUG", 756 }; 757 #endif 758 759 static int kgdb_panic_event(struct notifier_block *self, 760 unsigned long val, 761 void *data) 762 { 763 if (dbg_kdb_mode) 764 kdb_printf("PANIC: %s\n", (char *)data); 765 kgdb_breakpoint(); 766 return NOTIFY_DONE; 767 } 768 769 static struct notifier_block kgdb_panic_event_nb = { 770 .notifier_call = kgdb_panic_event, 771 .priority = INT_MAX, 772 }; 773 774 void __weak kgdb_arch_late(void) 775 { 776 } 777 778 void __init dbg_late_init(void) 779 { 780 dbg_is_early = false; 781 if (kgdb_io_module_registered) 782 kgdb_arch_late(); 783 kdb_init(KDB_INIT_FULL); 784 } 785 786 static void kgdb_register_callbacks(void) 787 { 788 if (!kgdb_io_module_registered) { 789 kgdb_io_module_registered = 1; 790 kgdb_arch_init(); 791 if (!dbg_is_early) 792 kgdb_arch_late(); 793 atomic_notifier_chain_register(&panic_notifier_list, 794 &kgdb_panic_event_nb); 795 #ifdef CONFIG_MAGIC_SYSRQ 796 register_sysrq_key('g', &sysrq_dbg_op); 797 #endif 798 if (kgdb_use_con && !kgdb_con_registered) { 799 register_console(&kgdbcons); 800 kgdb_con_registered = 1; 801 } 802 } 803 } 804 805 static void kgdb_unregister_callbacks(void) 806 { 807 /* 808 * When this routine is called KGDB should unregister from the 809 * panic handler and clean up, making sure it is not handling any 810 * break exceptions at the time. 811 */ 812 if (kgdb_io_module_registered) { 813 kgdb_io_module_registered = 0; 814 atomic_notifier_chain_unregister(&panic_notifier_list, 815 &kgdb_panic_event_nb); 816 kgdb_arch_exit(); 817 #ifdef CONFIG_MAGIC_SYSRQ 818 unregister_sysrq_key('g', &sysrq_dbg_op); 819 #endif 820 if (kgdb_con_registered) { 821 unregister_console(&kgdbcons); 822 kgdb_con_registered = 0; 823 } 824 } 825 } 826 827 /* 828 * There are times a tasklet needs to be used vs a compiled in 829 * break point so as to cause an exception outside a kgdb I/O module, 830 * such as is the case with kgdboe, where calling a breakpoint in the 831 * I/O driver itself would be fatal. 832 */ 833 static void kgdb_tasklet_bpt(unsigned long ing) 834 { 835 kgdb_breakpoint(); 836 atomic_set(&kgdb_break_tasklet_var, 0); 837 } 838 839 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0); 840 841 void kgdb_schedule_breakpoint(void) 842 { 843 if (atomic_read(&kgdb_break_tasklet_var) || 844 atomic_read(&kgdb_active) != -1 || 845 atomic_read(&kgdb_setting_breakpoint)) 846 return; 847 atomic_inc(&kgdb_break_tasklet_var); 848 tasklet_schedule(&kgdb_tasklet_breakpoint); 849 } 850 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint); 851 852 static void kgdb_initial_breakpoint(void) 853 { 854 kgdb_break_asap = 0; 855 856 printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n"); 857 kgdb_breakpoint(); 858 } 859 860 /** 861 * kgdb_register_io_module - register KGDB IO module 862 * @new_dbg_io_ops: the io ops vector 863 * 864 * Register it with the KGDB core. 865 */ 866 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) 867 { 868 int err; 869 870 spin_lock(&kgdb_registration_lock); 871 872 if (dbg_io_ops) { 873 spin_unlock(&kgdb_registration_lock); 874 875 printk(KERN_ERR "kgdb: Another I/O driver is already " 876 "registered with KGDB.\n"); 877 return -EBUSY; 878 } 879 880 if (new_dbg_io_ops->init) { 881 err = new_dbg_io_ops->init(); 882 if (err) { 883 spin_unlock(&kgdb_registration_lock); 884 return err; 885 } 886 } 887 888 dbg_io_ops = new_dbg_io_ops; 889 890 spin_unlock(&kgdb_registration_lock); 891 892 printk(KERN_INFO "kgdb: Registered I/O driver %s.\n", 893 new_dbg_io_ops->name); 894 895 /* Arm KGDB now. */ 896 kgdb_register_callbacks(); 897 898 if (kgdb_break_asap) 899 kgdb_initial_breakpoint(); 900 901 return 0; 902 } 903 EXPORT_SYMBOL_GPL(kgdb_register_io_module); 904 905 /** 906 * kkgdb_unregister_io_module - unregister KGDB IO module 907 * @old_dbg_io_ops: the io ops vector 908 * 909 * Unregister it with the KGDB core. 910 */ 911 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops) 912 { 913 BUG_ON(kgdb_connected); 914 915 /* 916 * KGDB is no longer able to communicate out, so 917 * unregister our callbacks and reset state. 918 */ 919 kgdb_unregister_callbacks(); 920 921 spin_lock(&kgdb_registration_lock); 922 923 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops); 924 dbg_io_ops = NULL; 925 926 spin_unlock(&kgdb_registration_lock); 927 928 printk(KERN_INFO 929 "kgdb: Unregistered I/O driver %s, debugger disabled.\n", 930 old_dbg_io_ops->name); 931 } 932 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module); 933 934 int dbg_io_get_char(void) 935 { 936 int ret = dbg_io_ops->read_char(); 937 if (ret == NO_POLL_CHAR) 938 return -1; 939 if (!dbg_kdb_mode) 940 return ret; 941 if (ret == 127) 942 return 8; 943 return ret; 944 } 945 946 /** 947 * kgdb_breakpoint - generate breakpoint exception 948 * 949 * This function will generate a breakpoint exception. It is used at the 950 * beginning of a program to sync up with a debugger and can be used 951 * otherwise as a quick means to stop program execution and "break" into 952 * the debugger. 953 */ 954 void kgdb_breakpoint(void) 955 { 956 atomic_inc(&kgdb_setting_breakpoint); 957 wmb(); /* Sync point before breakpoint */ 958 arch_kgdb_breakpoint(); 959 wmb(); /* Sync point after breakpoint */ 960 atomic_dec(&kgdb_setting_breakpoint); 961 } 962 EXPORT_SYMBOL_GPL(kgdb_breakpoint); 963 964 static int __init opt_kgdb_wait(char *str) 965 { 966 kgdb_break_asap = 1; 967 968 kdb_init(KDB_INIT_EARLY); 969 if (kgdb_io_module_registered) 970 kgdb_initial_breakpoint(); 971 972 return 0; 973 } 974 975 early_param("kgdbwait", opt_kgdb_wait); 976