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