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/reboot.h> 45 #include <linux/init.h> 46 #include <linux/kgdb.h> 47 #include <linux/kdb.h> 48 #include <linux/pid.h> 49 #include <linux/smp.h> 50 #include <linux/mm.h> 51 #include <linux/rcupdate.h> 52 53 #include <asm/cacheflush.h> 54 #include <asm/byteorder.h> 55 #include <linux/atomic.h> 56 #include <asm/system.h> 57 58 #include "debug_core.h" 59 60 static int kgdb_break_asap; 61 62 struct debuggerinfo_struct kgdb_info[NR_CPUS]; 63 64 /** 65 * kgdb_connected - Is a host GDB connected to us? 66 */ 67 int kgdb_connected; 68 EXPORT_SYMBOL_GPL(kgdb_connected); 69 70 /* All the KGDB handlers are installed */ 71 int kgdb_io_module_registered; 72 73 /* Guard for recursive entry */ 74 static int exception_level; 75 76 struct kgdb_io *dbg_io_ops; 77 static DEFINE_SPINLOCK(kgdb_registration_lock); 78 79 /* Action for the reboot notifiter, a global allow kdb to change it */ 80 static int kgdbreboot; 81 /* kgdb console driver is loaded */ 82 static int kgdb_con_registered; 83 /* determine if kgdb console output should be used */ 84 static int kgdb_use_con; 85 /* Flag for alternate operations for early debugging */ 86 bool dbg_is_early = true; 87 /* Next cpu to become the master debug core */ 88 int dbg_switch_cpu; 89 90 /* Use kdb or gdbserver mode */ 91 int dbg_kdb_mode = 1; 92 93 static int __init opt_kgdb_con(char *str) 94 { 95 kgdb_use_con = 1; 96 return 0; 97 } 98 99 early_param("kgdbcon", opt_kgdb_con); 100 101 module_param(kgdb_use_con, int, 0644); 102 module_param(kgdbreboot, int, 0644); 103 104 /* 105 * Holds information about breakpoints in a kernel. These breakpoints are 106 * added and removed by gdb. 107 */ 108 static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = { 109 [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED } 110 }; 111 112 /* 113 * The CPU# of the active CPU, or -1 if none: 114 */ 115 atomic_t kgdb_active = ATOMIC_INIT(-1); 116 EXPORT_SYMBOL_GPL(kgdb_active); 117 static DEFINE_RAW_SPINLOCK(dbg_master_lock); 118 static DEFINE_RAW_SPINLOCK(dbg_slave_lock); 119 120 /* 121 * We use NR_CPUs not PERCPU, in case kgdb is used to debug early 122 * bootup code (which might not have percpu set up yet): 123 */ 124 static atomic_t masters_in_kgdb; 125 static atomic_t slaves_in_kgdb; 126 static atomic_t kgdb_break_tasklet_var; 127 atomic_t kgdb_setting_breakpoint; 128 129 struct task_struct *kgdb_usethread; 130 struct task_struct *kgdb_contthread; 131 132 int kgdb_single_step; 133 static pid_t kgdb_sstep_pid; 134 135 /* to keep track of the CPU which is doing the single stepping*/ 136 atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1); 137 138 /* 139 * If you are debugging a problem where roundup (the collection of 140 * all other CPUs) is a problem [this should be extremely rare], 141 * then use the nokgdbroundup option to avoid roundup. In that case 142 * the other CPUs might interfere with your debugging context, so 143 * use this with care: 144 */ 145 static int kgdb_do_roundup = 1; 146 147 static int __init opt_nokgdbroundup(char *str) 148 { 149 kgdb_do_roundup = 0; 150 151 return 0; 152 } 153 154 early_param("nokgdbroundup", opt_nokgdbroundup); 155 156 /* 157 * Finally, some KGDB code :-) 158 */ 159 160 /* 161 * Weak aliases for breakpoint management, 162 * can be overriden by architectures when needed: 163 */ 164 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr) 165 { 166 int err; 167 168 err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE); 169 if (err) 170 return err; 171 172 return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr, 173 BREAK_INSTR_SIZE); 174 } 175 176 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle) 177 { 178 return probe_kernel_write((char *)addr, 179 (char *)bundle, BREAK_INSTR_SIZE); 180 } 181 182 int __weak kgdb_validate_break_address(unsigned long addr) 183 { 184 char tmp_variable[BREAK_INSTR_SIZE]; 185 int err; 186 /* Validate setting the breakpoint and then removing it. In the 187 * remove fails, the kernel needs to emit a bad message because we 188 * are deep trouble not being able to put things back the way we 189 * found them. 190 */ 191 err = kgdb_arch_set_breakpoint(addr, tmp_variable); 192 if (err) 193 return err; 194 err = kgdb_arch_remove_breakpoint(addr, tmp_variable); 195 if (err) 196 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel " 197 "memory destroyed at: %lx", addr); 198 return err; 199 } 200 201 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs) 202 { 203 return instruction_pointer(regs); 204 } 205 206 int __weak kgdb_arch_init(void) 207 { 208 return 0; 209 } 210 211 int __weak kgdb_skipexception(int exception, struct pt_regs *regs) 212 { 213 return 0; 214 } 215 216 /* 217 * Some architectures need cache flushes when we set/clear a 218 * breakpoint: 219 */ 220 static void kgdb_flush_swbreak_addr(unsigned long addr) 221 { 222 if (!CACHE_FLUSH_IS_SAFE) 223 return; 224 225 if (current->mm && current->mm->mmap_cache) { 226 flush_cache_range(current->mm->mmap_cache, 227 addr, addr + BREAK_INSTR_SIZE); 228 } 229 /* Force flush instruction cache if it was outside the mm */ 230 flush_icache_range(addr, addr + BREAK_INSTR_SIZE); 231 } 232 233 /* 234 * SW breakpoint management: 235 */ 236 int dbg_activate_sw_breakpoints(void) 237 { 238 unsigned long addr; 239 int error; 240 int ret = 0; 241 int i; 242 243 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 244 if (kgdb_break[i].state != BP_SET) 245 continue; 246 247 addr = kgdb_break[i].bpt_addr; 248 error = kgdb_arch_set_breakpoint(addr, 249 kgdb_break[i].saved_instr); 250 if (error) { 251 ret = error; 252 printk(KERN_INFO "KGDB: BP install failed: %lx", addr); 253 continue; 254 } 255 256 kgdb_flush_swbreak_addr(addr); 257 kgdb_break[i].state = BP_ACTIVE; 258 } 259 return ret; 260 } 261 262 int dbg_set_sw_break(unsigned long addr) 263 { 264 int err = kgdb_validate_break_address(addr); 265 int breakno = -1; 266 int i; 267 268 if (err) 269 return err; 270 271 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 272 if ((kgdb_break[i].state == BP_SET) && 273 (kgdb_break[i].bpt_addr == addr)) 274 return -EEXIST; 275 } 276 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 277 if (kgdb_break[i].state == BP_REMOVED && 278 kgdb_break[i].bpt_addr == addr) { 279 breakno = i; 280 break; 281 } 282 } 283 284 if (breakno == -1) { 285 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 286 if (kgdb_break[i].state == BP_UNDEFINED) { 287 breakno = i; 288 break; 289 } 290 } 291 } 292 293 if (breakno == -1) 294 return -E2BIG; 295 296 kgdb_break[breakno].state = BP_SET; 297 kgdb_break[breakno].type = BP_BREAKPOINT; 298 kgdb_break[breakno].bpt_addr = addr; 299 300 return 0; 301 } 302 303 int dbg_deactivate_sw_breakpoints(void) 304 { 305 unsigned long addr; 306 int error; 307 int ret = 0; 308 int i; 309 310 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 311 if (kgdb_break[i].state != BP_ACTIVE) 312 continue; 313 addr = kgdb_break[i].bpt_addr; 314 error = kgdb_arch_remove_breakpoint(addr, 315 kgdb_break[i].saved_instr); 316 if (error) { 317 printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr); 318 ret = error; 319 } 320 321 kgdb_flush_swbreak_addr(addr); 322 kgdb_break[i].state = BP_SET; 323 } 324 return ret; 325 } 326 327 int dbg_remove_sw_break(unsigned long addr) 328 { 329 int i; 330 331 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 332 if ((kgdb_break[i].state == BP_SET) && 333 (kgdb_break[i].bpt_addr == addr)) { 334 kgdb_break[i].state = BP_REMOVED; 335 return 0; 336 } 337 } 338 return -ENOENT; 339 } 340 341 int kgdb_isremovedbreak(unsigned long addr) 342 { 343 int i; 344 345 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 346 if ((kgdb_break[i].state == BP_REMOVED) && 347 (kgdb_break[i].bpt_addr == addr)) 348 return 1; 349 } 350 return 0; 351 } 352 353 int dbg_remove_all_break(void) 354 { 355 unsigned long addr; 356 int error; 357 int i; 358 359 /* Clear memory breakpoints. */ 360 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { 361 if (kgdb_break[i].state != BP_ACTIVE) 362 goto setundefined; 363 addr = kgdb_break[i].bpt_addr; 364 error = kgdb_arch_remove_breakpoint(addr, 365 kgdb_break[i].saved_instr); 366 if (error) 367 printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n", 368 addr); 369 setundefined: 370 kgdb_break[i].state = BP_UNDEFINED; 371 } 372 373 /* Clear hardware breakpoints. */ 374 if (arch_kgdb_ops.remove_all_hw_break) 375 arch_kgdb_ops.remove_all_hw_break(); 376 377 return 0; 378 } 379 380 /* 381 * Return true if there is a valid kgdb I/O module. Also if no 382 * debugger is attached a message can be printed to the console about 383 * waiting for the debugger to attach. 384 * 385 * The print_wait argument is only to be true when called from inside 386 * the core kgdb_handle_exception, because it will wait for the 387 * debugger to attach. 388 */ 389 static int kgdb_io_ready(int print_wait) 390 { 391 if (!dbg_io_ops) 392 return 0; 393 if (kgdb_connected) 394 return 1; 395 if (atomic_read(&kgdb_setting_breakpoint)) 396 return 1; 397 if (print_wait) { 398 #ifdef CONFIG_KGDB_KDB 399 if (!dbg_kdb_mode) 400 printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n"); 401 #else 402 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n"); 403 #endif 404 } 405 return 1; 406 } 407 408 static int kgdb_reenter_check(struct kgdb_state *ks) 409 { 410 unsigned long addr; 411 412 if (atomic_read(&kgdb_active) != raw_smp_processor_id()) 413 return 0; 414 415 /* Panic on recursive debugger calls: */ 416 exception_level++; 417 addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs); 418 dbg_deactivate_sw_breakpoints(); 419 420 /* 421 * If the break point removed ok at the place exception 422 * occurred, try to recover and print a warning to the end 423 * user because the user planted a breakpoint in a place that 424 * KGDB needs in order to function. 425 */ 426 if (dbg_remove_sw_break(addr) == 0) { 427 exception_level = 0; 428 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 429 dbg_activate_sw_breakpoints(); 430 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n", 431 addr); 432 WARN_ON_ONCE(1); 433 434 return 1; 435 } 436 dbg_remove_all_break(); 437 kgdb_skipexception(ks->ex_vector, ks->linux_regs); 438 439 if (exception_level > 1) { 440 dump_stack(); 441 panic("Recursive entry to debugger"); 442 } 443 444 printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n"); 445 #ifdef CONFIG_KGDB_KDB 446 /* Allow kdb to debug itself one level */ 447 return 0; 448 #endif 449 dump_stack(); 450 panic("Recursive entry to debugger"); 451 452 return 1; 453 } 454 455 static void dbg_touch_watchdogs(void) 456 { 457 touch_softlockup_watchdog_sync(); 458 clocksource_touch_watchdog(); 459 rcu_cpu_stall_reset(); 460 } 461 462 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, 463 int exception_state) 464 { 465 unsigned long flags; 466 int sstep_tries = 100; 467 int error; 468 int cpu; 469 int trace_on = 0; 470 int online_cpus = num_online_cpus(); 471 472 kgdb_info[ks->cpu].enter_kgdb++; 473 kgdb_info[ks->cpu].exception_state |= exception_state; 474 475 if (exception_state == DCPU_WANT_MASTER) 476 atomic_inc(&masters_in_kgdb); 477 else 478 atomic_inc(&slaves_in_kgdb); 479 480 if (arch_kgdb_ops.disable_hw_break) 481 arch_kgdb_ops.disable_hw_break(regs); 482 483 acquirelock: 484 /* 485 * Interrupts will be restored by the 'trap return' code, except when 486 * single stepping. 487 */ 488 local_irq_save(flags); 489 490 cpu = ks->cpu; 491 kgdb_info[cpu].debuggerinfo = regs; 492 kgdb_info[cpu].task = current; 493 kgdb_info[cpu].ret_state = 0; 494 kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT; 495 496 /* Make sure the above info reaches the primary CPU */ 497 smp_mb(); 498 499 if (exception_level == 1) { 500 if (raw_spin_trylock(&dbg_master_lock)) 501 atomic_xchg(&kgdb_active, cpu); 502 goto cpu_master_loop; 503 } 504 505 /* 506 * CPU will loop if it is a slave or request to become a kgdb 507 * master cpu and acquire the kgdb_active lock: 508 */ 509 while (1) { 510 cpu_loop: 511 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) { 512 kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER; 513 goto cpu_master_loop; 514 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) { 515 if (raw_spin_trylock(&dbg_master_lock)) { 516 atomic_xchg(&kgdb_active, cpu); 517 break; 518 } 519 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) { 520 if (!raw_spin_is_locked(&dbg_slave_lock)) 521 goto return_normal; 522 } else { 523 return_normal: 524 /* Return to normal operation by executing any 525 * hw breakpoint fixup. 526 */ 527 if (arch_kgdb_ops.correct_hw_break) 528 arch_kgdb_ops.correct_hw_break(); 529 if (trace_on) 530 tracing_on(); 531 kgdb_info[cpu].exception_state &= 532 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 533 kgdb_info[cpu].enter_kgdb--; 534 smp_mb__before_atomic_dec(); 535 atomic_dec(&slaves_in_kgdb); 536 dbg_touch_watchdogs(); 537 local_irq_restore(flags); 538 return 0; 539 } 540 cpu_relax(); 541 } 542 543 /* 544 * For single stepping, try to only enter on the processor 545 * that was single stepping. To guard against a deadlock, the 546 * kernel will only try for the value of sstep_tries before 547 * giving up and continuing on. 548 */ 549 if (atomic_read(&kgdb_cpu_doing_single_step) != -1 && 550 (kgdb_info[cpu].task && 551 kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) { 552 atomic_set(&kgdb_active, -1); 553 raw_spin_unlock(&dbg_master_lock); 554 dbg_touch_watchdogs(); 555 local_irq_restore(flags); 556 557 goto acquirelock; 558 } 559 560 if (!kgdb_io_ready(1)) { 561 kgdb_info[cpu].ret_state = 1; 562 goto kgdb_restore; /* No I/O connection, resume the system */ 563 } 564 565 /* 566 * Don't enter if we have hit a removed breakpoint. 567 */ 568 if (kgdb_skipexception(ks->ex_vector, ks->linux_regs)) 569 goto kgdb_restore; 570 571 /* Call the I/O driver's pre_exception routine */ 572 if (dbg_io_ops->pre_exception) 573 dbg_io_ops->pre_exception(); 574 575 /* 576 * Get the passive CPU lock which will hold all the non-primary 577 * CPU in a spin state while the debugger is active 578 */ 579 if (!kgdb_single_step) 580 raw_spin_lock(&dbg_slave_lock); 581 582 #ifdef CONFIG_SMP 583 /* Signal the other CPUs to enter kgdb_wait() */ 584 if ((!kgdb_single_step) && kgdb_do_roundup) 585 kgdb_roundup_cpus(flags); 586 #endif 587 588 /* 589 * Wait for the other CPUs to be notified and be waiting for us: 590 */ 591 while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) + 592 atomic_read(&slaves_in_kgdb)) != online_cpus) 593 cpu_relax(); 594 595 /* 596 * At this point the primary processor is completely 597 * in the debugger and all secondary CPUs are quiescent 598 */ 599 dbg_deactivate_sw_breakpoints(); 600 kgdb_single_step = 0; 601 kgdb_contthread = current; 602 exception_level = 0; 603 trace_on = tracing_is_on(); 604 if (trace_on) 605 tracing_off(); 606 607 while (1) { 608 cpu_master_loop: 609 if (dbg_kdb_mode) { 610 kgdb_connected = 1; 611 error = kdb_stub(ks); 612 if (error == -1) 613 continue; 614 kgdb_connected = 0; 615 } else { 616 error = gdb_serial_stub(ks); 617 } 618 619 if (error == DBG_PASS_EVENT) { 620 dbg_kdb_mode = !dbg_kdb_mode; 621 } else if (error == DBG_SWITCH_CPU_EVENT) { 622 kgdb_info[dbg_switch_cpu].exception_state |= 623 DCPU_NEXT_MASTER; 624 goto cpu_loop; 625 } else { 626 kgdb_info[cpu].ret_state = error; 627 break; 628 } 629 } 630 631 /* Call the I/O driver's post_exception routine */ 632 if (dbg_io_ops->post_exception) 633 dbg_io_ops->post_exception(); 634 635 if (!kgdb_single_step) { 636 raw_spin_unlock(&dbg_slave_lock); 637 /* Wait till all the CPUs have quit from the debugger. */ 638 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb)) 639 cpu_relax(); 640 } 641 642 kgdb_restore: 643 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) { 644 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step); 645 if (kgdb_info[sstep_cpu].task) 646 kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid; 647 else 648 kgdb_sstep_pid = 0; 649 } 650 if (arch_kgdb_ops.correct_hw_break) 651 arch_kgdb_ops.correct_hw_break(); 652 if (trace_on) 653 tracing_on(); 654 655 kgdb_info[cpu].exception_state &= 656 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); 657 kgdb_info[cpu].enter_kgdb--; 658 smp_mb__before_atomic_dec(); 659 atomic_dec(&masters_in_kgdb); 660 /* Free kgdb_active */ 661 atomic_set(&kgdb_active, -1); 662 raw_spin_unlock(&dbg_master_lock); 663 dbg_touch_watchdogs(); 664 local_irq_restore(flags); 665 666 return kgdb_info[cpu].ret_state; 667 } 668 669 /* 670 * kgdb_handle_exception() - main entry point from a kernel exception 671 * 672 * Locking hierarchy: 673 * interface locks, if any (begin_session) 674 * kgdb lock (kgdb_active) 675 */ 676 int 677 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) 678 { 679 struct kgdb_state kgdb_var; 680 struct kgdb_state *ks = &kgdb_var; 681 682 ks->cpu = raw_smp_processor_id(); 683 ks->ex_vector = evector; 684 ks->signo = signo; 685 ks->err_code = ecode; 686 ks->kgdb_usethreadid = 0; 687 ks->linux_regs = regs; 688 689 if (kgdb_reenter_check(ks)) 690 return 0; /* Ouch, double exception ! */ 691 if (kgdb_info[ks->cpu].enter_kgdb != 0) 692 return 0; 693 694 return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); 695 } 696 697 int kgdb_nmicallback(int cpu, void *regs) 698 { 699 #ifdef CONFIG_SMP 700 struct kgdb_state kgdb_var; 701 struct kgdb_state *ks = &kgdb_var; 702 703 memset(ks, 0, sizeof(struct kgdb_state)); 704 ks->cpu = cpu; 705 ks->linux_regs = regs; 706 707 if (kgdb_info[ks->cpu].enter_kgdb == 0 && 708 raw_spin_is_locked(&dbg_master_lock)) { 709 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE); 710 return 0; 711 } 712 #endif 713 return 1; 714 } 715 716 static void kgdb_console_write(struct console *co, const char *s, 717 unsigned count) 718 { 719 unsigned long flags; 720 721 /* If we're debugging, or KGDB has not connected, don't try 722 * and print. */ 723 if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode) 724 return; 725 726 local_irq_save(flags); 727 gdbstub_msg_write(s, count); 728 local_irq_restore(flags); 729 } 730 731 static struct console kgdbcons = { 732 .name = "kgdb", 733 .write = kgdb_console_write, 734 .flags = CON_PRINTBUFFER | CON_ENABLED, 735 .index = -1, 736 }; 737 738 #ifdef CONFIG_MAGIC_SYSRQ 739 static void sysrq_handle_dbg(int key) 740 { 741 if (!dbg_io_ops) { 742 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n"); 743 return; 744 } 745 if (!kgdb_connected) { 746 #ifdef CONFIG_KGDB_KDB 747 if (!dbg_kdb_mode) 748 printk(KERN_CRIT "KGDB or $3#33 for KDB\n"); 749 #else 750 printk(KERN_CRIT "Entering KGDB\n"); 751 #endif 752 } 753 754 kgdb_breakpoint(); 755 } 756 757 static struct sysrq_key_op sysrq_dbg_op = { 758 .handler = sysrq_handle_dbg, 759 .help_msg = "debug(G)", 760 .action_msg = "DEBUG", 761 }; 762 #endif 763 764 static int kgdb_panic_event(struct notifier_block *self, 765 unsigned long val, 766 void *data) 767 { 768 if (dbg_kdb_mode) 769 kdb_printf("PANIC: %s\n", (char *)data); 770 kgdb_breakpoint(); 771 return NOTIFY_DONE; 772 } 773 774 static struct notifier_block kgdb_panic_event_nb = { 775 .notifier_call = kgdb_panic_event, 776 .priority = INT_MAX, 777 }; 778 779 void __weak kgdb_arch_late(void) 780 { 781 } 782 783 void __init dbg_late_init(void) 784 { 785 dbg_is_early = false; 786 if (kgdb_io_module_registered) 787 kgdb_arch_late(); 788 kdb_init(KDB_INIT_FULL); 789 } 790 791 static int 792 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x) 793 { 794 /* 795 * Take the following action on reboot notify depending on value: 796 * 1 == Enter debugger 797 * 0 == [the default] detatch debug client 798 * -1 == Do nothing... and use this until the board resets 799 */ 800 switch (kgdbreboot) { 801 case 1: 802 kgdb_breakpoint(); 803 case -1: 804 goto done; 805 } 806 if (!dbg_kdb_mode) 807 gdbstub_exit(code); 808 done: 809 return NOTIFY_DONE; 810 } 811 812 static struct notifier_block dbg_reboot_notifier = { 813 .notifier_call = dbg_notify_reboot, 814 .next = NULL, 815 .priority = INT_MAX, 816 }; 817 818 static void kgdb_register_callbacks(void) 819 { 820 if (!kgdb_io_module_registered) { 821 kgdb_io_module_registered = 1; 822 kgdb_arch_init(); 823 if (!dbg_is_early) 824 kgdb_arch_late(); 825 register_reboot_notifier(&dbg_reboot_notifier); 826 atomic_notifier_chain_register(&panic_notifier_list, 827 &kgdb_panic_event_nb); 828 #ifdef CONFIG_MAGIC_SYSRQ 829 register_sysrq_key('g', &sysrq_dbg_op); 830 #endif 831 if (kgdb_use_con && !kgdb_con_registered) { 832 register_console(&kgdbcons); 833 kgdb_con_registered = 1; 834 } 835 } 836 } 837 838 static void kgdb_unregister_callbacks(void) 839 { 840 /* 841 * When this routine is called KGDB should unregister from the 842 * panic handler and clean up, making sure it is not handling any 843 * break exceptions at the time. 844 */ 845 if (kgdb_io_module_registered) { 846 kgdb_io_module_registered = 0; 847 unregister_reboot_notifier(&dbg_reboot_notifier); 848 atomic_notifier_chain_unregister(&panic_notifier_list, 849 &kgdb_panic_event_nb); 850 kgdb_arch_exit(); 851 #ifdef CONFIG_MAGIC_SYSRQ 852 unregister_sysrq_key('g', &sysrq_dbg_op); 853 #endif 854 if (kgdb_con_registered) { 855 unregister_console(&kgdbcons); 856 kgdb_con_registered = 0; 857 } 858 } 859 } 860 861 /* 862 * There are times a tasklet needs to be used vs a compiled in 863 * break point so as to cause an exception outside a kgdb I/O module, 864 * such as is the case with kgdboe, where calling a breakpoint in the 865 * I/O driver itself would be fatal. 866 */ 867 static void kgdb_tasklet_bpt(unsigned long ing) 868 { 869 kgdb_breakpoint(); 870 atomic_set(&kgdb_break_tasklet_var, 0); 871 } 872 873 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0); 874 875 void kgdb_schedule_breakpoint(void) 876 { 877 if (atomic_read(&kgdb_break_tasklet_var) || 878 atomic_read(&kgdb_active) != -1 || 879 atomic_read(&kgdb_setting_breakpoint)) 880 return; 881 atomic_inc(&kgdb_break_tasklet_var); 882 tasklet_schedule(&kgdb_tasklet_breakpoint); 883 } 884 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint); 885 886 static void kgdb_initial_breakpoint(void) 887 { 888 kgdb_break_asap = 0; 889 890 printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n"); 891 kgdb_breakpoint(); 892 } 893 894 /** 895 * kgdb_register_io_module - register KGDB IO module 896 * @new_dbg_io_ops: the io ops vector 897 * 898 * Register it with the KGDB core. 899 */ 900 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) 901 { 902 int err; 903 904 spin_lock(&kgdb_registration_lock); 905 906 if (dbg_io_ops) { 907 spin_unlock(&kgdb_registration_lock); 908 909 printk(KERN_ERR "kgdb: Another I/O driver is already " 910 "registered with KGDB.\n"); 911 return -EBUSY; 912 } 913 914 if (new_dbg_io_ops->init) { 915 err = new_dbg_io_ops->init(); 916 if (err) { 917 spin_unlock(&kgdb_registration_lock); 918 return err; 919 } 920 } 921 922 dbg_io_ops = new_dbg_io_ops; 923 924 spin_unlock(&kgdb_registration_lock); 925 926 printk(KERN_INFO "kgdb: Registered I/O driver %s.\n", 927 new_dbg_io_ops->name); 928 929 /* Arm KGDB now. */ 930 kgdb_register_callbacks(); 931 932 if (kgdb_break_asap) 933 kgdb_initial_breakpoint(); 934 935 return 0; 936 } 937 EXPORT_SYMBOL_GPL(kgdb_register_io_module); 938 939 /** 940 * kkgdb_unregister_io_module - unregister KGDB IO module 941 * @old_dbg_io_ops: the io ops vector 942 * 943 * Unregister it with the KGDB core. 944 */ 945 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops) 946 { 947 BUG_ON(kgdb_connected); 948 949 /* 950 * KGDB is no longer able to communicate out, so 951 * unregister our callbacks and reset state. 952 */ 953 kgdb_unregister_callbacks(); 954 955 spin_lock(&kgdb_registration_lock); 956 957 WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops); 958 dbg_io_ops = NULL; 959 960 spin_unlock(&kgdb_registration_lock); 961 962 printk(KERN_INFO 963 "kgdb: Unregistered I/O driver %s, debugger disabled.\n", 964 old_dbg_io_ops->name); 965 } 966 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module); 967 968 int dbg_io_get_char(void) 969 { 970 int ret = dbg_io_ops->read_char(); 971 if (ret == NO_POLL_CHAR) 972 return -1; 973 if (!dbg_kdb_mode) 974 return ret; 975 if (ret == 127) 976 return 8; 977 return ret; 978 } 979 980 /** 981 * kgdb_breakpoint - generate breakpoint exception 982 * 983 * This function will generate a breakpoint exception. It is used at the 984 * beginning of a program to sync up with a debugger and can be used 985 * otherwise as a quick means to stop program execution and "break" into 986 * the debugger. 987 */ 988 void kgdb_breakpoint(void) 989 { 990 atomic_inc(&kgdb_setting_breakpoint); 991 wmb(); /* Sync point before breakpoint */ 992 arch_kgdb_breakpoint(); 993 wmb(); /* Sync point after breakpoint */ 994 atomic_dec(&kgdb_setting_breakpoint); 995 } 996 EXPORT_SYMBOL_GPL(kgdb_breakpoint); 997 998 static int __init opt_kgdb_wait(char *str) 999 { 1000 kgdb_break_asap = 1; 1001 1002 kdb_init(KDB_INIT_EARLY); 1003 if (kgdb_io_module_registered) 1004 kgdb_initial_breakpoint(); 1005 1006 return 0; 1007 } 1008 1009 early_param("kgdbwait", opt_kgdb_wait); 1010