arch/powerpc/kernel/kgdb.c

   1 /*
   2  * PowerPC backend to the KGDB stub.
   3  *
   4  * 1998 (c) Michael AK Tesch (tesch@cs.wisc.edu)
   5  * Copyright (C) 2003 Timesys Corporation.
   6  * Copyright (C) 2004-2006 MontaVista Software, Inc.
   7  * PPC64 Mods (C) 2005 Frank Rowand (frowand@mvista.com)
   8  * PPC32 support restored by Vitaly Wool <vwool@ru.mvista.com> and
   9  * Sergei Shtylyov <sshtylyov@ru.mvista.com>
  10  * Copyright (C) 2007-2008 Wind River Systems, Inc.
  11  *
  12  * This file is licensed under the terms of the GNU General Public License
  13  * version 2. This program as licensed "as is" without any warranty of any
  14  * kind, whether express or implied.
  15  */
  16
  17 #include <linux/kernel.h>
  18 #include <linux/init.h>
  19 #include <linux/kgdb.h>
  20 #include <linux/smp.h>
  21 #include <linux/signal.h>
  22 #include <linux/ptrace.h>
  23 #include <linux/kdebug.h>
  24 #include <asm/current.h>
  25 #include <asm/processor.h>
  26 #include <asm/machdep.h>
  27 #include <asm/debug.h>
  28 #include <linux/slab.h>
  29
  30 /*
  31  * This table contains the mapping between PowerPC hardware trap types, and
  32  * signals, which are primarily what GDB understands.  GDB and the kernel
  33  * don't always agree on values, so we use constants taken from gdb-6.2.
  34  */
  35 static struct hard_trap_info
  36 {
  37         unsigned int tt;                /* Trap type code for powerpc */
  38         unsigned char signo;            /* Signal that we map this trap into */
  39 } hard_trap_info[] = {
  40         { 0x0100, 0x02 /* SIGINT */  },         /* system reset */
  41         { 0x0200, 0x0b /* SIGSEGV */ },         /* machine check */
  42         { 0x0300, 0x0b /* SIGSEGV */ },         /* data access */
  43         { 0x0400, 0x0b /* SIGSEGV */ },         /* instruction access */
  44         { 0x0500, 0x02 /* SIGINT */  },         /* external interrupt */
  45         { 0x0600, 0x0a /* SIGBUS */  },         /* alignment */
  46         { 0x0700, 0x05 /* SIGTRAP */ },         /* program check */
  47         { 0x0800, 0x08 /* SIGFPE */  },         /* fp unavailable */
  48         { 0x0900, 0x0e /* SIGALRM */ },         /* decrementer */
  49         { 0x0c00, 0x14 /* SIGCHLD */ },         /* system call */
  50 #if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
  51         { 0x2002, 0x05 /* SIGTRAP */ },         /* debug */
  52 #if defined(CONFIG_FSL_BOOKE)
  53         { 0x2010, 0x08 /* SIGFPE */  },         /* spe unavailable */
  54         { 0x2020, 0x08 /* SIGFPE */  },         /* spe unavailable */
  55         { 0x2030, 0x08 /* SIGFPE */  },         /* spe fp data */
  56         { 0x2040, 0x08 /* SIGFPE */  },         /* spe fp data */
  57         { 0x2050, 0x08 /* SIGFPE */  },         /* spe fp round */
  58         { 0x2060, 0x0e /* SIGILL */  },         /* performance monitor */
  59         { 0x2900, 0x08 /* SIGFPE */  },         /* apu unavailable */
  60         { 0x3100, 0x0e /* SIGALRM */ },         /* fixed interval timer */
  61         { 0x3200, 0x02 /* SIGINT */  },         /* watchdog */
  62 #else /* ! CONFIG_FSL_BOOKE */
  63         { 0x1000, 0x0e /* SIGALRM */ },         /* prog interval timer */
  64         { 0x1010, 0x0e /* SIGALRM */ },         /* fixed interval timer */
  65         { 0x1020, 0x02 /* SIGINT */  },         /* watchdog */
  66         { 0x2010, 0x08 /* SIGFPE */  },         /* fp unavailable */
  67         { 0x2020, 0x08 /* SIGFPE */  },         /* ap unavailable */
  68 #endif
  69 #else /* ! (defined(CONFIG_40x) || defined(CONFIG_BOOKE)) */
  70         { 0x0d00, 0x05 /* SIGTRAP */ },         /* single-step */
  71 #if defined(CONFIG_8xx)
  72         { 0x1000, 0x04 /* SIGILL */  },         /* software emulation */
  73 #else /* ! CONFIG_8xx */
  74         { 0x0f00, 0x04 /* SIGILL */  },         /* performance monitor */
  75         { 0x0f20, 0x08 /* SIGFPE */  },         /* altivec unavailable */
  76         { 0x1300, 0x05 /* SIGTRAP */ },         /* instruction address break */
  77 #if defined(CONFIG_PPC64)
  78         { 0x1200, 0x05 /* SIGILL */  },         /* system error */
  79         { 0x1500, 0x04 /* SIGILL */  },         /* soft patch */
  80         { 0x1600, 0x04 /* SIGILL */  },         /* maintenance */
  81         { 0x1700, 0x08 /* SIGFPE */  },         /* altivec assist */
  82         { 0x1800, 0x04 /* SIGILL */  },         /* thermal */
  83 #else /* ! CONFIG_PPC64 */
  84         { 0x1400, 0x02 /* SIGINT */  },         /* SMI */
  85         { 0x1600, 0x08 /* SIGFPE */  },         /* altivec assist */
  86         { 0x1700, 0x04 /* SIGILL */  },         /* TAU */
  87         { 0x2000, 0x05 /* SIGTRAP */ },         /* run mode */
  88 #endif
  89 #endif
  90 #endif
  91         { 0x0000, 0x00 }                        /* Must be last */
  92 };
  93
  94 static int computeSignal(unsigned int tt)
  95 {
  96         struct hard_trap_info *ht;
  97
  98         for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
  99                 if (ht->tt == tt)
 100                         return ht->signo;
 101
 102         return SIGHUP;          /* default for things we don't know about */
 103 }
 104
 105 /**
 106  *
 107  *      kgdb_skipexception - Bail out of KGDB when we've been triggered.
 108  *      @exception: Exception vector number
 109  *      @regs: Current &struct pt_regs.
 110  *
 111  *      On some architectures we need to skip a breakpoint exception when
 112  *      it occurs after a breakpoint has been removed.
 113  *
 114  */
 115 int kgdb_skipexception(int exception, struct pt_regs *regs)
 116 {
 117         return kgdb_isremovedbreak(regs->nip);
 118 }
 119
 120 static int kgdb_call_nmi_hook(struct pt_regs *regs)
 121 {
 122         kgdb_nmicallback(raw_smp_processor_id(), regs);
 123         return 0;
 124 }
 125
 126 #ifdef CONFIG_SMP
 127 void kgdb_roundup_cpus(unsigned long flags)
 128 {
 129         smp_send_debugger_break();
 130 }
 131 #endif
 132
 133 /* KGDB functions to use existing PowerPC64 hooks. */
 134 static int kgdb_debugger(struct pt_regs *regs)
 135 {
 136         return !kgdb_handle_exception(1, computeSignal(TRAP(regs)),
 137                                       DIE_OOPS, regs);
 138 }
 139
 140 static int kgdb_handle_breakpoint(struct pt_regs *regs)
 141 {
 142         if (user_mode(regs))
 143                 return 0;
 144
 145         if (kgdb_handle_exception(1, SIGTRAP, 0, regs) != 0)
 146                 return 0;
 147
 148         if (*(u32 *) (regs->nip) == *(u32 *) (&arch_kgdb_ops.gdb_bpt_instr))
 149                 regs->nip += BREAK_INSTR_SIZE;
 150
 151         return 1;
 152 }
 153
 154 static int kgdb_singlestep(struct pt_regs *regs)
 155 {
 156         struct thread_info *thread_info, *exception_thread_info;
 157         struct thread_info *backup_current_thread_info = \
 158                 (struct thread_info *)kmalloc(sizeof(struct thread_info), GFP_KERNEL);
 159
 160         if (user_mode(regs))
 161                 return 0;
 162
 163         /*
 164          * On Book E and perhaps other processors, singlestep is handled on
 165          * the critical exception stack.  This causes current_thread_info()
 166          * to fail, since it it locates the thread_info by masking off
 167          * the low bits of the current stack pointer.  We work around
 168          * this issue by copying the thread_info from the kernel stack
 169          * before calling kgdb_handle_exception, and copying it back
 170          * afterwards.  On most processors the copy is avoided since
 171          * exception_thread_info == thread_info.
 172          */
 173         thread_info = (struct thread_info *)(regs->gpr[1] & ~(THREAD_SIZE-1));
 174         exception_thread_info = current_thread_info();
 175
 176         if (thread_info != exception_thread_info) {
 177                 /* Save the original current_thread_info. */
 178                 memcpy(backup_current_thread_info, exception_thread_info, sizeof *thread_info);
 179                 memcpy(exception_thread_info, thread_info, sizeof *thread_info);
 180         }
 181
 182         kgdb_handle_exception(0, SIGTRAP, 0, regs);
 183
 184         if (thread_info != exception_thread_info)
 185                 /* Restore current_thread_info lastly. */
 186                 memcpy(exception_thread_info, backup_current_thread_info, sizeof *thread_info);
 187
 188         return 1;
 189 }
 190
 191 static int kgdb_iabr_match(struct pt_regs *regs)
 192 {
 193         if (user_mode(regs))
 194                 return 0;
 195
 196         if (kgdb_handle_exception(0, computeSignal(TRAP(regs)), 0, regs) != 0)
 197                 return 0;
 198         return 1;
 199 }
 200
 201 static int kgdb_dabr_match(struct pt_regs *regs)
 202 {
 203         if (user_mode(regs))
 204                 return 0;
 205
 206         if (kgdb_handle_exception(0, computeSignal(TRAP(regs)), 0, regs) != 0)
 207                 return 0;
 208         return 1;
 209 }
 210
 211 #define PACK64(ptr, src) do { *(ptr++) = (src); } while (0)
 212
 213 #define PACK32(ptr, src) do {          \
 214         u32 *ptr32;                   \
 215         ptr32 = (u32 *)ptr;           \
 216         *(ptr32++) = (src);           \
 217         ptr = (unsigned long *)ptr32; \
 218         } while (0)
 219
 220 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
 221 {
 222         struct pt_regs *regs = (struct pt_regs *)(p->thread.ksp +
 223                                                   STACK_FRAME_OVERHEAD);
 224         unsigned long *ptr = gdb_regs;
 225         int reg;
 226
 227         memset(gdb_regs, 0, NUMREGBYTES);
 228
 229         /* Regs GPR0-2 */
 230         for (reg = 0; reg < 3; reg++)
 231                 PACK64(ptr, regs->gpr[reg]);
 232
 233         /* Regs GPR3-13 are caller saved, not in regs->gpr[] */
 234         ptr += 11;
 235
 236         /* Regs GPR14-31 */
 237         for (reg = 14; reg < 32; reg++)
 238                 PACK64(ptr, regs->gpr[reg]);
 239
 240 #ifdef CONFIG_FSL_BOOKE
 241 #ifdef CONFIG_SPE
 242         for (reg = 0; reg < 32; reg++)
 243                 PACK64(ptr, p->thread.evr[reg]);
 244 #else
 245         ptr += 32;
 246 #endif
 247 #else
 248         /* fp registers not used by kernel, leave zero */
 249         ptr += 32 * 8 / sizeof(long);
 250 #endif
 251
 252         PACK64(ptr, regs->nip);
 253         PACK64(ptr, regs->msr);
 254         PACK32(ptr, regs->ccr);
 255         PACK64(ptr, regs->link);
 256         PACK64(ptr, regs->ctr);
 257         PACK32(ptr, regs->xer);
 258
 259         BUG_ON((unsigned long)ptr >
 260                (unsigned long)(((void *)gdb_regs) + NUMREGBYTES));
 261 }
 262
 263 #define GDB_SIZEOF_REG sizeof(unsigned long)
 264 #define GDB_SIZEOF_REG_U32 sizeof(u32)
 265
 266 #ifdef CONFIG_FSL_BOOKE
 267 #define GDB_SIZEOF_FLOAT_REG sizeof(unsigned long)
 268 #else
 269 #define GDB_SIZEOF_FLOAT_REG sizeof(u64)
 270 #endif
 271
 272 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
 273 {
 274         { "r0", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[0]) },
 275         { "r1", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[1]) },
 276         { "r2", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[2]) },
 277         { "r3", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[3]) },
 278         { "r4", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[4]) },
 279         { "r5", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[5]) },
 280         { "r6", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[6]) },
 281         { "r7", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[7]) },
 282         { "r8", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[8]) },
 283         { "r9", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[9]) },
 284         { "r10", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[10]) },
 285         { "r11", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[11]) },
 286         { "r12", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[12]) },
 287         { "r13", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[13]) },
 288         { "r14", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[14]) },
 289         { "r15", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[15]) },
 290         { "r16", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[16]) },
 291         { "r17", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[17]) },
 292         { "r18", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[18]) },
 293         { "r19", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[19]) },
 294         { "r20", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[20]) },
 295         { "r21", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[21]) },
 296         { "r22", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[22]) },
 297         { "r23", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[23]) },
 298         { "r24", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[24]) },
 299         { "r25", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[25]) },
 300         { "r26", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[26]) },
 301         { "r27", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[27]) },
 302         { "r28", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[28]) },
 303         { "r29", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[29]) },
 304         { "r30", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[30]) },
 305         { "r31", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[31]) },
 306
 307         { "f0", GDB_SIZEOF_FLOAT_REG, 0 },
 308         { "f1", GDB_SIZEOF_FLOAT_REG, 1 },
 309         { "f2", GDB_SIZEOF_FLOAT_REG, 2 },
 310         { "f3", GDB_SIZEOF_FLOAT_REG, 3 },
 311         { "f4", GDB_SIZEOF_FLOAT_REG, 4 },
 312         { "f5", GDB_SIZEOF_FLOAT_REG, 5 },
 313         { "f6", GDB_SIZEOF_FLOAT_REG, 6 },
 314         { "f7", GDB_SIZEOF_FLOAT_REG, 7 },
 315         { "f8", GDB_SIZEOF_FLOAT_REG, 8 },
 316         { "f9", GDB_SIZEOF_FLOAT_REG, 9 },
 317         { "f10", GDB_SIZEOF_FLOAT_REG, 10 },
 318         { "f11", GDB_SIZEOF_FLOAT_REG, 11 },
 319         { "f12", GDB_SIZEOF_FLOAT_REG, 12 },
 320         { "f13", GDB_SIZEOF_FLOAT_REG, 13 },
 321         { "f14", GDB_SIZEOF_FLOAT_REG, 14 },
 322         { "f15", GDB_SIZEOF_FLOAT_REG, 15 },
 323         { "f16", GDB_SIZEOF_FLOAT_REG, 16 },
 324         { "f17", GDB_SIZEOF_FLOAT_REG, 17 },
 325         { "f18", GDB_SIZEOF_FLOAT_REG, 18 },
 326         { "f19", GDB_SIZEOF_FLOAT_REG, 19 },
 327         { "f20", GDB_SIZEOF_FLOAT_REG, 20 },
 328         { "f21", GDB_SIZEOF_FLOAT_REG, 21 },
 329         { "f22", GDB_SIZEOF_FLOAT_REG, 22 },
 330         { "f23", GDB_SIZEOF_FLOAT_REG, 23 },
 331         { "f24", GDB_SIZEOF_FLOAT_REG, 24 },
 332         { "f25", GDB_SIZEOF_FLOAT_REG, 25 },
 333         { "f26", GDB_SIZEOF_FLOAT_REG, 26 },
 334         { "f27", GDB_SIZEOF_FLOAT_REG, 27 },
 335         { "f28", GDB_SIZEOF_FLOAT_REG, 28 },
 336         { "f29", GDB_SIZEOF_FLOAT_REG, 29 },
 337         { "f30", GDB_SIZEOF_FLOAT_REG, 30 },
 338         { "f31", GDB_SIZEOF_FLOAT_REG, 31 },
 339
 340         { "pc", GDB_SIZEOF_REG, offsetof(struct pt_regs, nip) },
 341         { "msr", GDB_SIZEOF_REG, offsetof(struct pt_regs, msr) },
 342         { "cr", GDB_SIZEOF_REG_U32, offsetof(struct pt_regs, ccr) },
 343         { "lr", GDB_SIZEOF_REG, offsetof(struct pt_regs, link) },
 344         { "ctr", GDB_SIZEOF_REG_U32, offsetof(struct pt_regs, ctr) },
 345         { "xer", GDB_SIZEOF_REG, offsetof(struct pt_regs, xer) },
 346 };
 347
 348 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
 349 {
 350         if (regno >= DBG_MAX_REG_NUM || regno < 0)
 351                 return NULL;
 352
 353         if (regno < 32 || regno >= 64)
 354                 /* First 0 -> 31 gpr registers*/
 355                 /* pc, msr, ls... registers 64 -> 69 */
 356                 memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
 357                                 dbg_reg_def[regno].size);
 358
 359         if (regno >= 32 && regno < 64) {
 360                 /* FP registers 32 -> 63 */
 361 #if defined(CONFIG_FSL_BOOKE) && defined(CONFIG_SPE)
 362                 if (current)
 363                         memcpy(mem, &current->thread.evr[regno-32],
 364                                         dbg_reg_def[regno].size);
 365 #else
 366                 /* fp registers not used by kernel, leave zero */
 367                 memset(mem, 0, dbg_reg_def[regno].size);
 368 #endif
 369         }
 370
 371         return dbg_reg_def[regno].name;
 372 }
 373
 374 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
 375 {
 376         if (regno >= DBG_MAX_REG_NUM || regno < 0)
 377                 return -EINVAL;
 378
 379         if (regno < 32 || regno >= 64)
 380                 /* First 0 -> 31 gpr registers*/
 381                 /* pc, msr, ls... registers 64 -> 69 */
 382                 memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
 383                                 dbg_reg_def[regno].size);
 384
 385         if (regno >= 32 && regno < 64) {
 386                 /* FP registers 32 -> 63 */
 387 #if defined(CONFIG_FSL_BOOKE) && defined(CONFIG_SPE)
 388                 memcpy(&current->thread.evr[regno-32], mem,
 389                                 dbg_reg_def[regno].size);
 390 #else
 391                 /* fp registers not used by kernel, leave zero */
 392                 return 0;
 393 #endif
 394         }
 395
 396         return 0;
 397 }
 398
 399 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
 400 {
 401         regs->nip = pc;
 402 }
 403
 404 /*
 405  * This function does PowerPC specific procesing for interfacing to gdb.
 406  */
 407 int kgdb_arch_handle_exception(int vector, int signo, int err_code,
 408                                char *remcom_in_buffer, char *remcom_out_buffer,
 409                                struct pt_regs *linux_regs)
 410 {
 411         char *ptr = &remcom_in_buffer[1];
 412         unsigned long addr;
 413
 414         switch (remcom_in_buffer[0]) {
 415                 /*
 416                  * sAA..AA   Step one instruction from AA..AA
 417                  * This will return an error to gdb ..
 418                  */
 419         case 's':
 420         case 'c':
 421                 /* handle the optional parameter */
 422                 if (kgdb_hex2long(&ptr, &addr))
 423                         linux_regs->nip = addr;
 424
 425                 atomic_set(&kgdb_cpu_doing_single_step, -1);
 426                 /* set the trace bit if we're stepping */
 427                 if (remcom_in_buffer[0] == 's') {
 428 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
 429                         mtspr(SPRN_DBCR0,
 430                               mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
 431                         linux_regs->msr |= MSR_DE;
 432 #else
 433                         linux_regs->msr |= MSR_SE;
 434 #endif
 435                         atomic_set(&kgdb_cpu_doing_single_step,
 436                                    raw_smp_processor_id());
 437                 }
 438                 return 0;
 439         }
 440
 441         return -1;
 442 }
 443
 444 /*
 445  * Global data
 446  */
 447 struct kgdb_arch arch_kgdb_ops = {
 448         .gdb_bpt_instr = {0x7d, 0x82, 0x10, 0x08},
 449 };
 450
 451 static int kgdb_not_implemented(struct pt_regs *regs)
 452 {
 453         return 0;
 454 }
 455
 456 static void *old__debugger_ipi;
 457 static void *old__debugger;
 458 static void *old__debugger_bpt;
 459 static void *old__debugger_sstep;
 460 static void *old__debugger_iabr_match;
 461 static void *old__debugger_dabr_match;
 462 static void *old__debugger_fault_handler;
 463
 464 int kgdb_arch_init(void)
 465 {
 466         old__debugger_ipi = __debugger_ipi;
 467         old__debugger = __debugger;
 468         old__debugger_bpt = __debugger_bpt;
 469         old__debugger_sstep = __debugger_sstep;
 470         old__debugger_iabr_match = __debugger_iabr_match;
 471         old__debugger_dabr_match = __debugger_dabr_match;
 472         old__debugger_fault_handler = __debugger_fault_handler;
 473
 474         __debugger_ipi = kgdb_call_nmi_hook;
 475         __debugger = kgdb_debugger;
 476         __debugger_bpt = kgdb_handle_breakpoint;
 477         __debugger_sstep = kgdb_singlestep;
 478         __debugger_iabr_match = kgdb_iabr_match;
 479         __debugger_dabr_match = kgdb_dabr_match;
 480         __debugger_fault_handler = kgdb_not_implemented;
 481
 482         return 0;
 483 }
 484
 485 void kgdb_arch_exit(void)
 486 {
 487         __debugger_ipi = old__debugger_ipi;
 488         __debugger = old__debugger;
 489         __debugger_bpt = old__debugger_bpt;
 490         __debugger_sstep = old__debugger_sstep;
 491         __debugger_iabr_match = old__debugger_iabr_match;
 492         __debugger_dabr_match = old__debugger_dabr_match;
 493         __debugger_fault_handler = old__debugger_fault_handler;
 494 }