arch/x86/kernel/kgdb.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify it
   3  * under the terms of the GNU General Public License as published by the
   4  * Free Software Foundation; either version 2, or (at your option) any
   5  * later version.
   6  *
   7  * This program is distributed in the hope that it will be useful, but
   8  * WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  10  * General Public License for more details.
  11  *
  12  */
  13
  14 /*
  15  * Copyright (C) 2004 Amit S. Kale <amitkale@linsyssoft.com>
  16  * Copyright (C) 2000-2001 VERITAS Software Corporation.
  17  * Copyright (C) 2002 Andi Kleen, SuSE Labs
  18  * Copyright (C) 2004 LinSysSoft Technologies Pvt. Ltd.
  19  * Copyright (C) 2007 MontaVista Software, Inc.
  20  * Copyright (C) 2007-2008 Jason Wessel, Wind River Systems, Inc.
  21  */
  22 /****************************************************************************
  23  *  Contributor:     Lake Stevens Instrument Division$
  24  *  Written by:      Glenn Engel $
  25  *  Updated by:      Amit Kale<akale@veritas.com>
  26  *  Updated by:      Tom Rini <trini@kernel.crashing.org>
  27  *  Updated by:      Jason Wessel <jason.wessel@windriver.com>
  28  *  Modified for 386 by Jim Kingdon, Cygnus Support.
  29  *  Origianl kgdb, compatibility with 2.1.xx kernel by
  30  *  David Grothe <dave@gcom.com>
  31  *  Integrated into 2.2.5 kernel by Tigran Aivazian <tigran@sco.com>
  32  *  X86_64 changes from Andi Kleen's patch merged by Jim Houston
  33  */
  34 #include <linux/spinlock.h>
  35 #include <linux/kdebug.h>
  36 #include <linux/string.h>
  37 #include <linux/kernel.h>
  38 #include <linux/ptrace.h>
  39 #include <linux/sched.h>
  40 #include <linux/delay.h>
  41 #include <linux/kgdb.h>
  42 #include <linux/init.h>
  43 #include <linux/smp.h>
  44 #include <linux/nmi.h>
  45 #include <linux/hw_breakpoint.h>
  46
  47 #include <asm/debugreg.h>
  48 #include <asm/apicdef.h>
  49 #include <asm/system.h>
  50
  51 #include <asm/apic.h>
  52
  53 /*
  54  * Put the error code here just in case the user cares:
  55  */
  56 static int gdb_x86errcode;
  57
  58 /*
  59  * Likewise, the vector number here (since GDB only gets the signal
  60  * number through the usual means, and that's not very specific):
  61  */
  62 static int gdb_x86vector = -1;
  63
  64 /**
  65  *      pt_regs_to_gdb_regs - Convert ptrace regs to GDB regs
  66  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
  67  *      @regs: The &struct pt_regs of the current process.
  68  *
  69  *      Convert the pt_regs in @regs into the format for registers that
  70  *      GDB expects, stored in @gdb_regs.
  71  */
  72 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
  73 {
  74 #ifndef CONFIG_X86_32
  75         u32 *gdb_regs32 = (u32 *)gdb_regs;
  76 #endif
  77         gdb_regs[GDB_AX]        = regs->ax;
  78         gdb_regs[GDB_BX]        = regs->bx;
  79         gdb_regs[GDB_CX]        = regs->cx;
  80         gdb_regs[GDB_DX]        = regs->dx;
  81         gdb_regs[GDB_SI]        = regs->si;
  82         gdb_regs[GDB_DI]        = regs->di;
  83         gdb_regs[GDB_BP]        = regs->bp;
  84         gdb_regs[GDB_PC]        = regs->ip;
  85 #ifdef CONFIG_X86_32
  86         gdb_regs[GDB_PS]        = regs->flags;
  87         gdb_regs[GDB_DS]        = regs->ds;
  88         gdb_regs[GDB_ES]        = regs->es;
  89         gdb_regs[GDB_CS]        = regs->cs;
  90         gdb_regs[GDB_FS]        = 0xFFFF;
  91         gdb_regs[GDB_GS]        = 0xFFFF;
  92         if (user_mode_vm(regs)) {
  93                 gdb_regs[GDB_SS] = regs->ss;
  94                 gdb_regs[GDB_SP] = regs->sp;
  95         } else {
  96                 gdb_regs[GDB_SS] = __KERNEL_DS;
  97                 gdb_regs[GDB_SP] = kernel_stack_pointer(regs);
  98         }
  99 #else
 100         gdb_regs[GDB_R8]        = regs->r8;
 101         gdb_regs[GDB_R9]        = regs->r9;
 102         gdb_regs[GDB_R10]       = regs->r10;
 103         gdb_regs[GDB_R11]       = regs->r11;
 104         gdb_regs[GDB_R12]       = regs->r12;
 105         gdb_regs[GDB_R13]       = regs->r13;
 106         gdb_regs[GDB_R14]       = regs->r14;
 107         gdb_regs[GDB_R15]       = regs->r15;
 108         gdb_regs32[GDB_PS]      = regs->flags;
 109         gdb_regs32[GDB_CS]      = regs->cs;
 110         gdb_regs32[GDB_SS]      = regs->ss;
 111         gdb_regs[GDB_SP]        = kernel_stack_pointer(regs);
 112 #endif
 113 }
 114
 115 /**
 116  *      sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
 117  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
 118  *      @p: The &struct task_struct of the desired process.
 119  *
 120  *      Convert the register values of the sleeping process in @p to
 121  *      the format that GDB expects.
 122  *      This function is called when kgdb does not have access to the
 123  *      &struct pt_regs and therefore it should fill the gdb registers
 124  *      @gdb_regs with what has been saved in &struct thread_struct
 125  *      thread field during switch_to.
 126  */
 127 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
 128 {
 129 #ifndef CONFIG_X86_32
 130         u32 *gdb_regs32 = (u32 *)gdb_regs;
 131 #endif
 132         gdb_regs[GDB_AX]        = 0;
 133         gdb_regs[GDB_BX]        = 0;
 134         gdb_regs[GDB_CX]        = 0;
 135         gdb_regs[GDB_DX]        = 0;
 136         gdb_regs[GDB_SI]        = 0;
 137         gdb_regs[GDB_DI]        = 0;
 138         gdb_regs[GDB_BP]        = *(unsigned long *)p->thread.sp;
 139 #ifdef CONFIG_X86_32
 140         gdb_regs[GDB_DS]        = __KERNEL_DS;
 141         gdb_regs[GDB_ES]        = __KERNEL_DS;
 142         gdb_regs[GDB_PS]        = 0;
 143         gdb_regs[GDB_CS]        = __KERNEL_CS;
 144         gdb_regs[GDB_PC]        = p->thread.ip;
 145         gdb_regs[GDB_SS]        = __KERNEL_DS;
 146         gdb_regs[GDB_FS]        = 0xFFFF;
 147         gdb_regs[GDB_GS]        = 0xFFFF;
 148 #else
 149         gdb_regs32[GDB_PS]      = *(unsigned long *)(p->thread.sp + 8);
 150         gdb_regs32[GDB_CS]      = __KERNEL_CS;
 151         gdb_regs32[GDB_SS]      = __KERNEL_DS;
 152         gdb_regs[GDB_PC]        = 0;
 153         gdb_regs[GDB_R8]        = 0;
 154         gdb_regs[GDB_R9]        = 0;
 155         gdb_regs[GDB_R10]       = 0;
 156         gdb_regs[GDB_R11]       = 0;
 157         gdb_regs[GDB_R12]       = 0;
 158         gdb_regs[GDB_R13]       = 0;
 159         gdb_regs[GDB_R14]       = 0;
 160         gdb_regs[GDB_R15]       = 0;
 161 #endif
 162         gdb_regs[GDB_SP]        = p->thread.sp;
 163 }
 164
 165 /**
 166  *      gdb_regs_to_pt_regs - Convert GDB regs to ptrace regs.
 167  *      @gdb_regs: A pointer to hold the registers we've received from GDB.
 168  *      @regs: A pointer to a &struct pt_regs to hold these values in.
 169  *
 170  *      Convert the GDB regs in @gdb_regs into the pt_regs, and store them
 171  *      in @regs.
 172  */
 173 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 174 {
 175 #ifndef CONFIG_X86_32
 176         u32 *gdb_regs32 = (u32 *)gdb_regs;
 177 #endif
 178         regs->ax                = gdb_regs[GDB_AX];
 179         regs->bx                = gdb_regs[GDB_BX];
 180         regs->cx                = gdb_regs[GDB_CX];
 181         regs->dx                = gdb_regs[GDB_DX];
 182         regs->si                = gdb_regs[GDB_SI];
 183         regs->di                = gdb_regs[GDB_DI];
 184         regs->bp                = gdb_regs[GDB_BP];
 185         regs->ip                = gdb_regs[GDB_PC];
 186 #ifdef CONFIG_X86_32
 187         regs->flags             = gdb_regs[GDB_PS];
 188         regs->ds                = gdb_regs[GDB_DS];
 189         regs->es                = gdb_regs[GDB_ES];
 190         regs->cs                = gdb_regs[GDB_CS];
 191 #else
 192         regs->r8                = gdb_regs[GDB_R8];
 193         regs->r9                = gdb_regs[GDB_R9];
 194         regs->r10               = gdb_regs[GDB_R10];
 195         regs->r11               = gdb_regs[GDB_R11];
 196         regs->r12               = gdb_regs[GDB_R12];
 197         regs->r13               = gdb_regs[GDB_R13];
 198         regs->r14               = gdb_regs[GDB_R14];
 199         regs->r15               = gdb_regs[GDB_R15];
 200         regs->flags             = gdb_regs32[GDB_PS];
 201         regs->cs                = gdb_regs32[GDB_CS];
 202         regs->ss                = gdb_regs32[GDB_SS];
 203 #endif
 204 }
 205
 206 static struct hw_breakpoint {
 207         unsigned                enabled;
 208         unsigned long           addr;
 209         int                     len;
 210         int                     type;
 211         struct perf_event       **pev;
 212 } breakinfo[4];
 213
 214 static void kgdb_correct_hw_break(void)
 215 {
 216         int breakno;
 217
 218         for (breakno = 0; breakno < 4; breakno++) {
 219                 struct perf_event *bp;
 220                 struct arch_hw_breakpoint *info;
 221                 int val;
 222                 int cpu = raw_smp_processor_id();
 223                 if (!breakinfo[breakno].enabled)
 224                         continue;
 225                 bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
 226                 info = counter_arch_bp(bp);
 227                 if (bp->attr.disabled != 1)
 228                         continue;
 229                 bp->attr.bp_addr = breakinfo[breakno].addr;
 230                 bp->attr.bp_len = breakinfo[breakno].len;
 231                 bp->attr.bp_type = breakinfo[breakno].type;
 232                 info->address = breakinfo[breakno].addr;
 233                 info->len = breakinfo[breakno].len;
 234                 info->type = breakinfo[breakno].type;
 235                 val = arch_install_hw_breakpoint(bp);
 236                 if (!val)
 237                         bp->attr.disabled = 0;
 238         }
 239         hw_breakpoint_restore();
 240 }
 241
 242 static int
 243 kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
 244 {
 245         int i;
 246
 247         for (i = 0; i < 4; i++)
 248                 if (breakinfo[i].addr == addr && breakinfo[i].enabled)
 249                         break;
 250         if (i == 4)
 251                 return -1;
 252
 253         breakinfo[i].enabled = 0;
 254
 255         return 0;
 256 }
 257
 258 static void kgdb_remove_all_hw_break(void)
 259 {
 260         int i;
 261         int cpu = raw_smp_processor_id();
 262         struct perf_event *bp;
 263
 264         for (i = 0; i < 4; i++) {
 265                 if (!breakinfo[i].enabled)
 266                         continue;
 267                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
 268                 if (bp->attr.disabled == 1)
 269                         continue;
 270                 arch_uninstall_hw_breakpoint(bp);
 271                 bp->attr.disabled = 1;
 272         }
 273 }
 274
 275 static int
 276 kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
 277 {
 278         int i;
 279
 280         for (i = 0; i < 4; i++)
 281                 if (!breakinfo[i].enabled)
 282                         break;
 283         if (i == 4)
 284                 return -1;
 285
 286         switch (bptype) {
 287         case BP_HARDWARE_BREAKPOINT:
 288                 len = 1;
 289                 breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
 290                 break;
 291         case BP_WRITE_WATCHPOINT:
 292                 breakinfo[i].type = X86_BREAKPOINT_WRITE;
 293                 break;
 294         case BP_ACCESS_WATCHPOINT:
 295                 breakinfo[i].type = X86_BREAKPOINT_RW;
 296                 break;
 297         default:
 298                 return -1;
 299         }
 300         switch (len) {
 301         case 1:
 302                 breakinfo[i].len = X86_BREAKPOINT_LEN_1;
 303                 break;
 304         case 2:
 305                 breakinfo[i].len = X86_BREAKPOINT_LEN_2;
 306                 break;
 307         case 4:
 308                 breakinfo[i].len = X86_BREAKPOINT_LEN_4;
 309                 break;
 310 #ifdef CONFIG_X86_64
 311         case 8:
 312                 breakinfo[i].len = X86_BREAKPOINT_LEN_8;
 313                 break;
 314 #endif
 315         default:
 316                 return -1;
 317         }
 318         breakinfo[i].addr = addr;
 319         breakinfo[i].enabled = 1;
 320
 321         return 0;
 322 }
 323
 324 /**
 325  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 326  *      @regs: Current &struct pt_regs.
 327  *
 328  *      This function will be called if the particular architecture must
 329  *      disable hardware debugging while it is processing gdb packets or
 330  *      handling exception.
 331  */
 332 void kgdb_disable_hw_debug(struct pt_regs *regs)
 333 {
 334         int i;
 335         int cpu = raw_smp_processor_id();
 336         struct perf_event *bp;
 337
 338         /* Disable hardware debugging while we are in kgdb: */
 339         set_debugreg(0UL, 7);
 340         for (i = 0; i < 4; i++) {
 341                 if (!breakinfo[i].enabled)
 342                         continue;
 343                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
 344                 if (bp->attr.disabled == 1)
 345                         continue;
 346                 arch_uninstall_hw_breakpoint(bp);
 347                 bp->attr.disabled = 1;
 348         }
 349 }
 350
 351 /**
 352  *      kgdb_post_primary_code - Save error vector/code numbers.
 353  *      @regs: Original pt_regs.
 354  *      @e_vector: Original error vector.
 355  *      @err_code: Original error code.
 356  *
 357  *      This is needed on architectures which support SMP and KGDB.
 358  *      This function is called after all the slave cpus have been put
 359  *      to a know spin state and the primary CPU has control over KGDB.
 360  */
 361 void kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
 362 {
 363         /* primary processor is completely in the debugger */
 364         gdb_x86vector = e_vector;
 365         gdb_x86errcode = err_code;
 366 }
 367
 368 #ifdef CONFIG_SMP
 369 /**
 370  *      kgdb_roundup_cpus - Get other CPUs into a holding pattern
 371  *      @flags: Current IRQ state
 372  *
 373  *      On SMP systems, we need to get the attention of the other CPUs
 374  *      and get them be in a known state.  This should do what is needed
 375  *      to get the other CPUs to call kgdb_wait(). Note that on some arches,
 376  *      the NMI approach is not used for rounding up all the CPUs. For example,
 377  *      in case of MIPS, smp_call_function() is used to roundup CPUs. In
 378  *      this case, we have to make sure that interrupts are enabled before
 379  *      calling smp_call_function(). The argument to this function is
 380  *      the flags that will be used when restoring the interrupts. There is
 381  *      local_irq_save() call before kgdb_roundup_cpus().
 382  *
 383  *      On non-SMP systems, this is not called.
 384  */
 385 void kgdb_roundup_cpus(unsigned long flags)
 386 {
 387         apic->send_IPI_allbutself(APIC_DM_NMI);
 388 }
 389 #endif
 390
 391 /**
 392  *      kgdb_arch_handle_exception - Handle architecture specific GDB packets.
 393  *      @vector: The error vector of the exception that happened.
 394  *      @signo: The signal number of the exception that happened.
 395  *      @err_code: The error code of the exception that happened.
 396  *      @remcom_in_buffer: The buffer of the packet we have read.
 397  *      @remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
 398  *      @regs: The &struct pt_regs of the current process.
 399  *
 400  *      This function MUST handle the 'c' and 's' command packets,
 401  *      as well packets to set / remove a hardware breakpoint, if used.
 402  *      If there are additional packets which the hardware needs to handle,
 403  *      they are handled here.  The code should return -1 if it wants to
 404  *      process more packets, and a %0 or %1 if it wants to exit from the
 405  *      kgdb callback.
 406  */
 407 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
 408                                char *remcomInBuffer, char *remcomOutBuffer,
 409                                struct pt_regs *linux_regs)
 410 {
 411         unsigned long addr;
 412         char *ptr;
 413         int newPC;
 414
 415         switch (remcomInBuffer[0]) {
 416         case 'c':
 417         case 's':
 418                 /* try to read optional parameter, pc unchanged if no parm */
 419                 ptr = &remcomInBuffer[1];
 420                 if (kgdb_hex2long(&ptr, &addr))
 421                         linux_regs->ip = addr;
 422         case 'D':
 423         case 'k':
 424                 newPC = linux_regs->ip;
 425
 426                 /* clear the trace bit */
 427                 linux_regs->flags &= ~X86_EFLAGS_TF;
 428                 atomic_set(&kgdb_cpu_doing_single_step, -1);
 429
 430                 /* set the trace bit if we're stepping */
 431                 if (remcomInBuffer[0] == 's') {
 432                         linux_regs->flags |= X86_EFLAGS_TF;
 433                         atomic_set(&kgdb_cpu_doing_single_step,
 434                                    raw_smp_processor_id());
 435                 }
 436
 437                 kgdb_correct_hw_break();
 438
 439                 return 0;
 440         }
 441
 442         /* this means that we do not want to exit from the handler: */
 443         return -1;
 444 }
 445
 446 static inline int
 447 single_step_cont(struct pt_regs *regs, struct die_args *args)
 448 {
 449         /*
 450          * Single step exception from kernel space to user space so
 451          * eat the exception and continue the process:
 452          */
 453         printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
 454                         "resuming...\n");
 455         kgdb_arch_handle_exception(args->trapnr, args->signr,
 456                                    args->err, "c", "", regs);
 457         /*
 458          * Reset the BS bit in dr6 (pointed by args->err) to
 459          * denote completion of processing
 460          */
 461         (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
 462
 463         return NOTIFY_STOP;
 464 }
 465
 466 static int was_in_debug_nmi[NR_CPUS];
 467
 468 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 469 {
 470         struct pt_regs *regs = args->regs;
 471
 472         switch (cmd) {
 473         case DIE_NMI:
 474                 if (atomic_read(&kgdb_active) != -1) {
 475                         /* KGDB CPU roundup */
 476                         kgdb_nmicallback(raw_smp_processor_id(), regs);
 477                         was_in_debug_nmi[raw_smp_processor_id()] = 1;
 478                         touch_nmi_watchdog();
 479                         return NOTIFY_STOP;
 480                 }
 481                 return NOTIFY_DONE;
 482
 483         case DIE_NMI_IPI:
 484                 /* Just ignore, we will handle the roundup on DIE_NMI. */
 485                 return NOTIFY_DONE;
 486
 487         case DIE_NMIUNKNOWN:
 488                 if (was_in_debug_nmi[raw_smp_processor_id()]) {
 489                         was_in_debug_nmi[raw_smp_processor_id()] = 0;
 490                         return NOTIFY_STOP;
 491                 }
 492                 return NOTIFY_DONE;
 493
 494         case DIE_NMIWATCHDOG:
 495                 if (atomic_read(&kgdb_active) != -1) {
 496                         /* KGDB CPU roundup: */
 497                         kgdb_nmicallback(raw_smp_processor_id(), regs);
 498                         return NOTIFY_STOP;
 499                 }
 500                 /* Enter debugger: */
 501                 break;
 502
 503         case DIE_DEBUG:
 504                 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 505                         if (user_mode(regs))
 506                                 return single_step_cont(regs, args);
 507                         break;
 508                 } else if (test_thread_flag(TIF_SINGLESTEP))
 509                         /* This means a user thread is single stepping
 510                          * a system call which should be ignored
 511                          */
 512                         return NOTIFY_DONE;
 513                 /* fall through */
 514         default:
 515                 if (user_mode(regs))
 516                         return NOTIFY_DONE;
 517         }
 518
 519         if (kgdb_handle_exception(args->trapnr, args->signr, args->err, regs))
 520                 return NOTIFY_DONE;
 521
 522         /* Must touch watchdog before return to normal operation */
 523         touch_nmi_watchdog();
 524         return NOTIFY_STOP;
 525 }
 526
 527 static int
 528 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
 529 {
 530         unsigned long flags;
 531         int ret;
 532
 533         local_irq_save(flags);
 534         ret = __kgdb_notify(ptr, cmd);
 535         local_irq_restore(flags);
 536
 537         return ret;
 538 }
 539
 540 static struct notifier_block kgdb_notifier = {
 541         .notifier_call  = kgdb_notify,
 542
 543         /*
 544          * Lowest-prio notifier priority, we want to be notified last:
 545          */
 546         .priority       = -INT_MAX,
 547 };
 548
 549 /**
 550  *      kgdb_arch_init - Perform any architecture specific initalization.
 551  *
 552  *      This function will handle the initalization of any architecture
 553  *      specific callbacks.
 554  */
 555 int kgdb_arch_init(void)
 556 {
 557         int i, cpu;
 558         int ret;
 559         struct perf_event_attr attr;
 560         struct perf_event **pevent;
 561
 562         ret = register_die_notifier(&kgdb_notifier);
 563         if (ret != 0)
 564                 return ret;
 565         /*
 566          * Pre-allocate the hw breakpoint structions in the non-atomic
 567          * portion of kgdb because this operation requires mutexs to
 568          * complete.
 569          */
 570         attr.bp_addr = (unsigned long)kgdb_arch_init;
 571         attr.type = PERF_TYPE_BREAKPOINT;
 572         attr.bp_len = HW_BREAKPOINT_LEN_1;
 573         attr.bp_type = HW_BREAKPOINT_W;
 574         attr.disabled = 1;
 575         for (i = 0; i < 4; i++) {
 576                 breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL);
 577                 if (IS_ERR(breakinfo[i].pev)) {
 578                         printk(KERN_ERR "kgdb: Could not allocate hw breakpoints\n");
 579                         breakinfo[i].pev = NULL;
 580                         kgdb_arch_exit();
 581                         return -1;
 582                 }
 583                 for_each_online_cpu(cpu) {
 584                         pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
 585                         pevent[0]->hw.sample_period = 1;
 586                         if (pevent[0]->destroy != NULL) {
 587                                 pevent[0]->destroy = NULL;
 588                                 release_bp_slot(*pevent);
 589                         }
 590                 }
 591         }
 592         return ret;
 593 }
 594
 595 /**
 596  *      kgdb_arch_exit - Perform any architecture specific uninitalization.
 597  *
 598  *      This function will handle the uninitalization of any architecture
 599  *      specific callbacks, for dynamic registration and unregistration.
 600  */
 601 void kgdb_arch_exit(void)
 602 {
 603         int i;
 604         for (i = 0; i < 4; i++) {
 605                 if (breakinfo[i].pev) {
 606                         unregister_wide_hw_breakpoint(breakinfo[i].pev);
 607                         breakinfo[i].pev = NULL;
 608                 }
 609         }
 610         unregister_die_notifier(&kgdb_notifier);
 611 }
 612
 613 /**
 614  *
 615  *      kgdb_skipexception - Bail out of KGDB when we've been triggered.
 616  *      @exception: Exception vector number
 617  *      @regs: Current &struct pt_regs.
 618  *
 619  *      On some architectures we need to skip a breakpoint exception when
 620  *      it occurs after a breakpoint has been removed.
 621  *
 622  * Skip an int3 exception when it occurs after a breakpoint has been
 623  * removed. Backtrack eip by 1 since the int3 would have caused it to
 624  * increment by 1.
 625  */
 626 int kgdb_skipexception(int exception, struct pt_regs *regs)
 627 {
 628         if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
 629                 regs->ip -= 1;
 630                 return 1;
 631         }
 632         return 0;
 633 }
 634
 635 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
 636 {
 637         if (exception == 3)
 638                 return instruction_pointer(regs) - 1;
 639         return instruction_pointer(regs);
 640 }
 641
 642 struct kgdb_arch arch_kgdb_ops = {
 643         /* Breakpoint instruction: */
 644         .gdb_bpt_instr          = { 0xcc },
 645         .flags                  = KGDB_HW_BREAKPOINT,
 646         .set_hw_breakpoint      = kgdb_set_hw_break,
 647         .remove_hw_breakpoint   = kgdb_remove_hw_break,
 648         .remove_all_hw_break    = kgdb_remove_all_hw_break,
 649         .correct_hw_break       = kgdb_correct_hw_break,
 650 };