summaryrefslogtreecommitdiffstats
path: root/arch/powerpc/kernel/kgdb.c
blob: c470a40b29f5d4937883cfcd8a40dd1c6bbdcfd1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
/*
 * PowerPC backend to the KGDB stub.
 *
 * 1998 (c) Michael AK Tesch (tesch@cs.wisc.edu)
 * Copyright (C) 2003 Timesys Corporation.
 * Copyright (C) 2004-2006 MontaVista Software, Inc.
 * PPC64 Mods (C) 2005 Frank Rowand (frowand@mvista.com)
 * PPC32 support restored by Vitaly Wool <vwool@ru.mvista.com> and
 * Sergei Shtylyov <sshtylyov@ru.mvista.com>
 * Copyright (C) 2007-2008 Wind River Systems, Inc.
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2. This program as licensed "as is" without any warranty of any
 * kind, whether express or implied.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/kgdb.h>
#include <linux/smp.h>
#include <linux/signal.h>
#include <linux/ptrace.h>
#include <linux/kdebug.h>
#include <asm/current.h>
#include <asm/processor.h>
#include <asm/machdep.h>
#include <asm/debug.h>
#include <linux/slab.h>

/*
 * This table contains the mapping between PowerPC hardware trap types, and
 * signals, which are primarily what GDB understands.  GDB and the kernel
 * don't always agree on values, so we use constants taken from gdb-6.2.
 */
static struct hard_trap_info
{
	unsigned int tt;		/* Trap type code for powerpc */
	unsigned char signo;		/* Signal that we map this trap into */
} hard_trap_info[] = {
	{ 0x0100, 0x02 /* SIGINT */  },		/* system reset */
	{ 0x0200, 0x0b /* SIGSEGV */ },		/* machine check */
	{ 0x0300, 0x0b /* SIGSEGV */ },		/* data access */
	{ 0x0400, 0x0b /* SIGSEGV */ },		/* instruction access */
	{ 0x0500, 0x02 /* SIGINT */  },		/* external interrupt */
	{ 0x0600, 0x0a /* SIGBUS */  },		/* alignment */
	{ 0x0700, 0x05 /* SIGTRAP */ },		/* program check */
	{ 0x0800, 0x08 /* SIGFPE */  },		/* fp unavailable */
	{ 0x0900, 0x0e /* SIGALRM */ },		/* decrementer */
	{ 0x0c00, 0x14 /* SIGCHLD */ },		/* system call */
#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
	{ 0x2002, 0x05 /* SIGTRAP */ },		/* debug */
#if defined(CONFIG_FSL_BOOKE)
	{ 0x2010, 0x08 /* SIGFPE */  },		/* spe unavailable */
	{ 0x2020, 0x08 /* SIGFPE */  },		/* spe unavailable */
	{ 0x2030, 0x08 /* SIGFPE */  },		/* spe fp data */
	{ 0x2040, 0x08 /* SIGFPE */  },		/* spe fp data */
	{ 0x2050, 0x08 /* SIGFPE */  },		/* spe fp round */
	{ 0x2060, 0x0e /* SIGILL */  },		/* performance monitor */
	{ 0x2900, 0x08 /* SIGFPE */  },		/* apu unavailable */
	{ 0x3100, 0x0e /* SIGALRM */ },		/* fixed interval timer */
	{ 0x3200, 0x02 /* SIGINT */  }, 	/* watchdog */
#else /* ! CONFIG_FSL_BOOKE */
	{ 0x1000, 0x0e /* SIGALRM */ },		/* prog interval timer */
	{ 0x1010, 0x0e /* SIGALRM */ },		/* fixed interval timer */
	{ 0x1020, 0x02 /* SIGINT */  }, 	/* watchdog */
	{ 0x2010, 0x08 /* SIGFPE */  },		/* fp unavailable */
	{ 0x2020, 0x08 /* SIGFPE */  },		/* ap unavailable */
#endif
#else /* ! (defined(CONFIG_40x) || defined(CONFIG_BOOKE)) */
	{ 0x0d00, 0x05 /* SIGTRAP */ },		/* single-step */
#if defined(CONFIG_8xx)
	{ 0x1000, 0x04 /* SIGILL */  },		/* software emulation */
#else /* ! CONFIG_8xx */
	{ 0x0f00, 0x04 /* SIGILL */  },		/* performance monitor */
	{ 0x0f20, 0x08 /* SIGFPE */  },		/* altivec unavailable */
	{ 0x1300, 0x05 /* SIGTRAP */ }, 	/* instruction address break */
#if defined(CONFIG_PPC64)
	{ 0x1200, 0x05 /* SIGILL */  },		/* system error */
	{ 0x1500, 0x04 /* SIGILL */  },		/* soft patch */
	{ 0x1600, 0x04 /* SIGILL */  },		/* maintenance */
	{ 0x1700, 0x08 /* SIGFPE */  },		/* altivec assist */
	{ 0x1800, 0x04 /* SIGILL */  },		/* thermal */
#else /* ! CONFIG_PPC64 */
	{ 0x1400, 0x02 /* SIGINT */  },		/* SMI */
	{ 0x1600, 0x08 /* SIGFPE */  },		/* altivec assist */
	{ 0x1700, 0x04 /* SIGILL */  },		/* TAU */
	{ 0x2000, 0x05 /* SIGTRAP */ },		/* run mode */
#endif
#endif
#endif
	{ 0x0000, 0x00 }			/* Must be last */
};

static int computeSignal(unsigned int tt)
{
	struct hard_trap_info *ht;

	for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
		if (ht->tt == tt)
			return ht->signo;

	return SIGHUP;		/* default for things we don't know about */
}

/**
 *
 *	kgdb_skipexception - Bail out of KGDB when we've been triggered.
 *	@exception: Exception vector number
 *	@regs: Current &struct pt_regs.
 *
 *	On some architectures we need to skip a breakpoint exception when
 *	it occurs after a breakpoint has been removed.
 *
 */
int kgdb_skipexception(int exception, struct pt_regs *regs)
{
	return kgdb_isremovedbreak(regs->nip);
}

static int kgdb_call_nmi_hook(struct pt_regs *regs)
{
	kgdb_nmicallback(raw_smp_processor_id(), regs);
	return 0;
}

#ifdef CONFIG_SMP
void kgdb_roundup_cpus(unsigned long flags)
{
	smp_send_debugger_break();
}
#endif

/* KGDB functions to use existing PowerPC64 hooks. */
static int kgdb_debugger(struct pt_regs *regs)
{
	return !kgdb_handle_exception(1, computeSignal(TRAP(regs)),
				      DIE_OOPS, regs);
}

static int kgdb_handle_breakpoint(struct pt_regs *regs)
{
	if (user_mode(regs))
		return 0;

	if (kgdb_handle_exception(1, SIGTRAP, 0, regs) != 0)
		return 0;

	if (*(u32 *) (regs->nip) == *(u32 *) (&arch_kgdb_ops.gdb_bpt_instr))
		regs->nip += BREAK_INSTR_SIZE;

	return 1;
}

static int kgdb_singlestep(struct pt_regs *regs)
{
	struct thread_info *thread_info, *exception_thread_info;
	struct thread_info *backup_current_thread_info = \
		(struct thread_info *)kmalloc(sizeof(struct thread_info), GFP_KERNEL);

	if (user_mode(regs))
		return 0;

	/*
	 * On Book E and perhaps other processors, singlestep is handled on
	 * the critical exception stack.  This causes current_thread_info()
	 * to fail, since it it locates the thread_info by masking off
	 * the low bits of the current stack pointer.  We work around
	 * this issue by copying the thread_info from the kernel stack
	 * before calling kgdb_handle_exception, and copying it back
	 * afterwards.  On most processors the copy is avoided since
	 * exception_thread_info == thread_info.
	 */
	thread_info = (struct thread_info *)(regs->gpr[1] & ~(THREAD_SIZE-1));
	exception_thread_info = current_thread_info();

	if (thread_info != exception_thread_info) {
		/* Save the original current_thread_info. */
		memcpy(backup_current_thread_info, exception_thread_info, sizeof *thread_info);
		memcpy(exception_thread_info, thread_info, sizeof *thread_info);
	}

	kgdb_handle_exception(0, SIGTRAP, 0, regs);

	if (thread_info != exception_thread_info)
		/* Restore current_thread_info lastly. */
		memcpy(exception_thread_info, backup_current_thread_info, sizeof *thread_info);

	return 1;
}

static int kgdb_iabr_match(struct pt_regs *regs)
{
	if (user_mode(regs))
		return 0;

	if (kgdb_handle_exception(0, computeSignal(TRAP(regs)), 0, regs) != 0)
		return 0;
	return 1;
}

static int kgdb_dabr_match(struct pt_regs *regs)
{
	if (user_mode(regs))
		return 0;

	if (kgdb_handle_exception(0, computeSignal(TRAP(regs)), 0, regs) != 0)
		return 0;
	return 1;
}

#define PACK64(ptr, src) do { *(ptr++) = (src); } while (0)

#define PACK32(ptr, src) do {          \
	u32 *ptr32;                   \
	ptr32 = (u32 *)ptr;           \
	*(ptr32++) = (src);           \
	ptr = (unsigned long *)ptr32; \
	} while (0)

void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
{
	struct pt_regs *regs = (struct pt_regs *)(p->thread.ksp +
						  STACK_FRAME_OVERHEAD);
	unsigned long *ptr = gdb_regs;
	int reg;

	memset(gdb_regs, 0, NUMREGBYTES);

	/* Regs GPR0-2 */
	for (reg = 0; reg < 3; reg++)
		PACK64(ptr, regs->gpr[reg]);

	/* Regs GPR3-13 are caller saved, not in regs->gpr[] */
	ptr += 11;

	/* Regs GPR14-31 */
	for (reg = 14; reg < 32; reg++)
		PACK64(ptr, regs->gpr[reg]);

#ifdef CONFIG_FSL_BOOKE
#ifdef CONFIG_SPE
	for (reg = 0; reg < 32; reg++)
		PACK64(ptr, p->thread.evr[reg]);
#else
	ptr += 32;
#endif
#else
	/* fp registers not used by kernel, leave zero */
	ptr += 32 * 8 / sizeof(long);
#endif

	PACK64(ptr, regs->nip);
	PACK64(ptr, regs->msr);
	PACK32(ptr, regs->ccr);
	PACK64(ptr, regs->link);
	PACK64(ptr, regs->ctr);
	PACK32(ptr, regs->xer);

	BUG_ON((unsigned long)ptr >
	       (unsigned long)(((void *)gdb_regs) + NUMREGBYTES));
}

#define GDB_SIZEOF_REG sizeof(unsigned long)
#define GDB_SIZEOF_REG_U32 sizeof(u32)

#ifdef CONFIG_FSL_BOOKE
#define GDB_SIZEOF_FLOAT_REG sizeof(unsigned long)
#else
#define GDB_SIZEOF_FLOAT_REG sizeof(u64)
#endif

struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
{
	{ "r0", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[0]) },
	{ "r1", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[1]) },
	{ "r2", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[2]) },
	{ "r3", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[3]) },
	{ "r4", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[4]) },
	{ "r5", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[5]) },
	{ "r6", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[6]) },
	{ "r7", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[7]) },
	{ "r8", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[8]) },
	{ "r9", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[9]) },
	{ "r10", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[10]) },
	{ "r11", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[11]) },
	{ "r12", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[12]) },
	{ "r13", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[13]) },
	{ "r14", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[14]) },
	{ "r15", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[15]) },
	{ "r16", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[16]) },
	{ "r17", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[17]) },
	{ "r18", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[18]) },
	{ "r19", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[19]) },
	{ "r20", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[20]) },
	{ "r21", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[21]) },
	{ "r22", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[22]) },
	{ "r23", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[23]) },
	{ "r24", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[24]) },
	{ "r25", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[25]) },
	{ "r26", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[26]) },
	{ "r27", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[27]) },
	{ "r28", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[28]) },
	{ "r29", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[29]) },
	{ "r30", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[30]) },
	{ "r31", GDB_SIZEOF_REG, offsetof(struct pt_regs, gpr[31]) },

	{ "f0", GDB_SIZEOF_FLOAT_REG, 0 },
	{ "f1", GDB_SIZEOF_FLOAT_REG, 1 },
	{ "f2", GDB_SIZEOF_FLOAT_REG, 2 },
	{ "f3", GDB_SIZEOF_FLOAT_REG, 3 },
	{ "f4", GDB_SIZEOF_FLOAT_REG, 4 },
	{ "f5", GDB_SIZEOF_FLOAT_REG, 5 },
	{ "f6", GDB_SIZEOF_FLOAT_REG, 6 },
	{ "f7", GDB_SIZEOF_FLOAT_REG, 7 },
	{ "f8", GDB_SIZEOF_FLOAT_REG, 8 },
	{ "f9", GDB_SIZEOF_FLOAT_REG, 9 },
	{ "f10", GDB_SIZEOF_FLOAT_REG, 10 },
	{ "f11", GDB_SIZEOF_FLOAT_REG, 11 },
	{ "f12", GDB_SIZEOF_FLOAT_REG, 12 },
	{ "f13", GDB_SIZEOF_FLOAT_REG, 13 },
	{ "f14", GDB_SIZEOF_FLOAT_REG, 14 },
	{ "f15", GDB_SIZEOF_FLOAT_REG, 15 },
	{ "f16", GDB_SIZEOF_FLOAT_REG, 16 },
	{ "f17", GDB_SIZEOF_FLOAT_REG, 17 },
	{ "f18", GDB_SIZEOF_FLOAT_REG, 18 },
	{ "f19", GDB_SIZEOF_FLOAT_REG, 19 },
	{ "f20", GDB_SIZEOF_FLOAT_REG, 20 },
	{ "f21", GDB_SIZEOF_FLOAT_REG, 21 },
	{ "f22", GDB_SIZEOF_FLOAT_REG, 22 },
	{ "f23", GDB_SIZEOF_FLOAT_REG, 23 },
	{ "f24", GDB_SIZEOF_FLOAT_REG, 24 },
	{ "f25", GDB_SIZEOF_FLOAT_REG, 25 },
	{ "f26", GDB_SIZEOF_FLOAT_REG, 26 },
	{ "f27", GDB_SIZEOF_FLOAT_REG, 27 },
	{ "f28", GDB_SIZEOF_FLOAT_REG, 28 },
	{ "f29", GDB_SIZEOF_FLOAT_REG, 29 },
	{ "f30", GDB_SIZEOF_FLOAT_REG, 30 },
	{ "f31", GDB_SIZEOF_FLOAT_REG, 31 },

	{ "pc", GDB_SIZEOF_REG, offsetof(struct pt_regs, nip) },
	{ "msr", GDB_SIZEOF_REG, offsetof(struct pt_regs, msr) },
	{ "cr", GDB_SIZEOF_REG_U32, offsetof(struct pt_regs, ccr) },
	{ "lr", GDB_SIZEOF_REG, offsetof(struct pt_regs, link) },
	{ "ctr", GDB_SIZEOF_REG_U32, offsetof(struct pt_regs, ctr) },
	{ "xer", GDB_SIZEOF_REG, offsetof(struct pt_regs, xer) },
};

char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
{
	if (regno >= DBG_MAX_REG_NUM || regno < 0)
		return NULL;

	if (regno < 32 || regno >= 64)
		/* First 0 -> 31 gpr registers*/
		/* pc, msr, ls... registers 64 -> 69 */
		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
				dbg_reg_def[regno].size);

	if (regno >= 32 && regno < 64) {
		/* FP registers 32 -> 63 */
#if defined(CONFIG_FSL_BOOKE) && defined(CONFIG_SPE)
		if (current)
			memcpy(mem, &current->thread.evr[regno-32],
					dbg_reg_def[regno].size);
#else
		/* fp registers not used by kernel, leave zero */
		memset(mem, 0, dbg_reg_def[regno].size);
#endif
	}

	return dbg_reg_def[regno].name;
}

int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
{
	if (regno >= DBG_MAX_REG_NUM || regno < 0)
		return -EINVAL;

	if (regno < 32 || regno >= 64)
		/* First 0 -> 31 gpr registers*/
		/* pc, msr, ls... registers 64 -> 69 */
		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
				dbg_reg_def[regno].size);

	if (regno >= 32 && regno < 64) {
		/* FP registers 32 -> 63 */
#if defined(CONFIG_FSL_BOOKE) && defined(CONFIG_SPE)
		memcpy(&current->thread.evr[regno-32], mem,
				dbg_reg_def[regno].size);
#else
		/* fp registers not used by kernel, leave zero */
		return 0;
#endif
	}

	return 0;
}

void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
{
	regs->nip = pc;
}

/*
 * This function does PowerPC specific procesing for interfacing to gdb.
 */
int kgdb_arch_handle_exception(int vector, int signo, int err_code,
			       char *remcom_in_buffer, char *remcom_out_buffer,
			       struct pt_regs *linux_regs)
{
	char *ptr = &remcom_in_buffer[1];
	unsigned long addr;

	switch (remcom_in_buffer[0]) {
		/*
		 * sAA..AA   Step one instruction from AA..AA
		 * This will return an error to gdb ..
		 */
	case 's':
	case 'c':
		/* handle the optional parameter */
		if (kgdb_hex2long(&ptr, &addr))
			linux_regs->nip = addr;

		atomic_set(&kgdb_cpu_doing_single_step, -1);
		/* set the trace bit if we're stepping */
		if (remcom_in_buffer[0] == 's') {
#ifdef CONFIG_PPC_ADV_DEBUG_REGS
			mtspr(SPRN_DBCR0,
			      mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
			linux_regs->msr |= MSR_DE;
#else
			linux_regs->msr |= MSR_SE;
#endif
			atomic_set(&kgdb_cpu_doing_single_step,
				   raw_smp_processor_id());
		}
		return 0;
	}

	return -1;
}

/*
 * Global data
 */
struct kgdb_arch arch_kgdb_ops = {
	.gdb_bpt_instr = {0x7d, 0x82, 0x10, 0x08},
};

static int kgdb_not_implemented(struct pt_regs *regs)
{
	return 0;
}

static void *old__debugger_ipi;
static void *old__debugger;
static void *old__debugger_bpt;
static void *old__debugger_sstep;
static void *old__debugger_iabr_match;
static void *old__debugger_dabr_match;
static void *old__debugger_fault_handler;

int kgdb_arch_init(void)
{
	old__debugger_ipi = __debugger_ipi;
	old__debugger = __debugger;
	old__debugger_bpt = __debugger_bpt;
	old__debugger_sstep = __debugger_sstep;
	old__debugger_iabr_match = __debugger_iabr_match;
	old__debugger_dabr_match = __debugger_dabr_match;
	old__debugger_fault_handler = __debugger_fault_handler;

	__debugger_ipi = kgdb_call_nmi_hook;
	__debugger = kgdb_debugger;
	__debugger_bpt = kgdb_handle_breakpoint;
	__debugger_sstep = kgdb_singlestep;
	__debugger_iabr_match = kgdb_iabr_match;
	__debugger_dabr_match = kgdb_dabr_match;
	__debugger_fault_handler = kgdb_not_implemented;

	return 0;
}

void kgdb_arch_exit(void)
{
	__debugger_ipi = old__debugger_ipi;
	__debugger = old__debugger;
	__debugger_bpt = old__debugger_bpt;
	__debugger_sstep = old__debugger_sstep;
	__debugger_iabr_match = old__debugger_iabr_match;
	__debugger_dabr_match = old__debugger_dabr_match;
	__debugger_fault_handler = old__debugger_fault_handler;
}