kernel/debug/debug_core.c

   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);