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