summaryrefslogtreecommitdiff
path: root/arch/x86/kernel/kgdb.c
blob: 4425a12ece43cfd05d4a2bdad150a6b5a38f36c4 (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
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
/*
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 */

/*
 * Copyright (C) 2004 Amit S. Kale <amitkale@linsyssoft.com>
 * Copyright (C) 2000-2001 VERITAS Software Corporation.
 * Copyright (C) 2002 Andi Kleen, SuSE Labs
 * Copyright (C) 2004 LinSysSoft Technologies Pvt. Ltd.
 * Copyright (C) 2007 MontaVista Software, Inc.
 * Copyright (C) 2007-2008 Jason Wessel, Wind River Systems, Inc.
 */
/****************************************************************************
 *  Contributor:     Lake Stevens Instrument Division$
 *  Written by:      Glenn Engel $
 *  Updated by:	     Amit Kale<akale@veritas.com>
 *  Updated by:	     Tom Rini <trini@kernel.crashing.org>
 *  Updated by:	     Jason Wessel <jason.wessel@windriver.com>
 *  Modified for 386 by Jim Kingdon, Cygnus Support.
 *  Origianl kgdb, compatibility with 2.1.xx kernel by
 *  David Grothe <dave@gcom.com>
 *  Integrated into 2.2.5 kernel by Tigran Aivazian <tigran@sco.com>
 *  X86_64 changes from Andi Kleen's patch merged by Jim Houston
 */
#include <linux/spinlock.h>
#include <linux/kdebug.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/kgdb.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/nmi.h>
#include <linux/hw_breakpoint.h>

#include <asm/debugreg.h>
#include <asm/apicdef.h>
#include <asm/apic.h>
#include <asm/nmi.h>

struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
{
#ifdef CONFIG_X86_32
	{ "ax", 4, offsetof(struct pt_regs, ax) },
	{ "cx", 4, offsetof(struct pt_regs, cx) },
	{ "dx", 4, offsetof(struct pt_regs, dx) },
	{ "bx", 4, offsetof(struct pt_regs, bx) },
	{ "sp", 4, offsetof(struct pt_regs, sp) },
	{ "bp", 4, offsetof(struct pt_regs, bp) },
	{ "si", 4, offsetof(struct pt_regs, si) },
	{ "di", 4, offsetof(struct pt_regs, di) },
	{ "ip", 4, offsetof(struct pt_regs, ip) },
	{ "flags", 4, offsetof(struct pt_regs, flags) },
	{ "cs", 4, offsetof(struct pt_regs, cs) },
	{ "ss", 4, offsetof(struct pt_regs, ss) },
	{ "ds", 4, offsetof(struct pt_regs, ds) },
	{ "es", 4, offsetof(struct pt_regs, es) },
	{ "fs", 4, -1 },
	{ "gs", 4, -1 },
#else
	{ "ax", 8, offsetof(struct pt_regs, ax) },
	{ "bx", 8, offsetof(struct pt_regs, bx) },
	{ "cx", 8, offsetof(struct pt_regs, cx) },
	{ "dx", 8, offsetof(struct pt_regs, dx) },
	{ "si", 8, offsetof(struct pt_regs, dx) },
	{ "di", 8, offsetof(struct pt_regs, di) },
	{ "bp", 8, offsetof(struct pt_regs, bp) },
	{ "sp", 8, offsetof(struct pt_regs, sp) },
	{ "r8", 8, offsetof(struct pt_regs, r8) },
	{ "r9", 8, offsetof(struct pt_regs, r9) },
	{ "r10", 8, offsetof(struct pt_regs, r10) },
	{ "r11", 8, offsetof(struct pt_regs, r11) },
	{ "r12", 8, offsetof(struct pt_regs, r12) },
	{ "r13", 8, offsetof(struct pt_regs, r13) },
	{ "r14", 8, offsetof(struct pt_regs, r14) },
	{ "r15", 8, offsetof(struct pt_regs, r15) },
	{ "ip", 8, offsetof(struct pt_regs, ip) },
	{ "flags", 4, offsetof(struct pt_regs, flags) },
	{ "cs", 4, offsetof(struct pt_regs, cs) },
	{ "ss", 4, offsetof(struct pt_regs, ss) },
#endif
};

int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
{
	if (
#ifdef CONFIG_X86_32
	    regno == GDB_SS || regno == GDB_FS || regno == GDB_GS ||
#endif
	    regno == GDB_SP || regno == GDB_ORIG_AX)
		return 0;

	if (dbg_reg_def[regno].offset != -1)
		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
		       dbg_reg_def[regno].size);
	return 0;
}

char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
{
	if (regno == GDB_ORIG_AX) {
		memcpy(mem, &regs->orig_ax, sizeof(regs->orig_ax));
		return "orig_ax";
	}
	if (regno >= DBG_MAX_REG_NUM || regno < 0)
		return NULL;

	if (dbg_reg_def[regno].offset != -1)
		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
		       dbg_reg_def[regno].size);

#ifdef CONFIG_X86_32
	switch (regno) {
	case GDB_SS:
		if (!user_mode_vm(regs))
			*(unsigned long *)mem = __KERNEL_DS;
		break;
	case GDB_SP:
		if (!user_mode_vm(regs))
			*(unsigned long *)mem = kernel_stack_pointer(regs);
		break;
	case GDB_GS:
	case GDB_FS:
		*(unsigned long *)mem = 0xFFFF;
		break;
	}
#endif
	return dbg_reg_def[regno].name;
}

/**
 *	sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
 *	@gdb_regs: A pointer to hold the registers in the order GDB wants.
 *	@p: The &struct task_struct of the desired process.
 *
 *	Convert the register values of the sleeping process in @p to
 *	the format that GDB expects.
 *	This function is called when kgdb does not have access to the
 *	&struct pt_regs and therefore it should fill the gdb registers
 *	@gdb_regs with what has	been saved in &struct thread_struct
 *	thread field during switch_to.
 */
void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
{
#ifndef CONFIG_X86_32
	u32 *gdb_regs32 = (u32 *)gdb_regs;
#endif
	gdb_regs[GDB_AX]	= 0;
	gdb_regs[GDB_BX]	= 0;
	gdb_regs[GDB_CX]	= 0;
	gdb_regs[GDB_DX]	= 0;
	gdb_regs[GDB_SI]	= 0;
	gdb_regs[GDB_DI]	= 0;
	gdb_regs[GDB_BP]	= *(unsigned long *)p->thread.sp;
#ifdef CONFIG_X86_32
	gdb_regs[GDB_DS]	= __KERNEL_DS;
	gdb_regs[GDB_ES]	= __KERNEL_DS;
	gdb_regs[GDB_PS]	= 0;
	gdb_regs[GDB_CS]	= __KERNEL_CS;
	gdb_regs[GDB_PC]	= p->thread.ip;
	gdb_regs[GDB_SS]	= __KERNEL_DS;
	gdb_regs[GDB_FS]	= 0xFFFF;
	gdb_regs[GDB_GS]	= 0xFFFF;
#else
	gdb_regs32[GDB_PS]	= *(unsigned long *)(p->thread.sp + 8);
	gdb_regs32[GDB_CS]	= __KERNEL_CS;
	gdb_regs32[GDB_SS]	= __KERNEL_DS;
	gdb_regs[GDB_PC]	= 0;
	gdb_regs[GDB_R8]	= 0;
	gdb_regs[GDB_R9]	= 0;
	gdb_regs[GDB_R10]	= 0;
	gdb_regs[GDB_R11]	= 0;
	gdb_regs[GDB_R12]	= 0;
	gdb_regs[GDB_R13]	= 0;
	gdb_regs[GDB_R14]	= 0;
	gdb_regs[GDB_R15]	= 0;
#endif
	gdb_regs[GDB_SP]	= p->thread.sp;
}

static struct hw_breakpoint {
	unsigned		enabled;
	unsigned long		addr;
	int			len;
	int			type;
	struct perf_event	* __percpu *pev;
} breakinfo[HBP_NUM];

static unsigned long early_dr7;

static void kgdb_correct_hw_break(void)
{
	int breakno;

	for (breakno = 0; breakno < HBP_NUM; breakno++) {
		struct perf_event *bp;
		struct arch_hw_breakpoint *info;
		int val;
		int cpu = raw_smp_processor_id();
		if (!breakinfo[breakno].enabled)
			continue;
		if (dbg_is_early) {
			set_debugreg(breakinfo[breakno].addr, breakno);
			early_dr7 |= encode_dr7(breakno,
						breakinfo[breakno].len,
						breakinfo[breakno].type);
			set_debugreg(early_dr7, 7);
			continue;
		}
		bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
		info = counter_arch_bp(bp);
		if (bp->attr.disabled != 1)
			continue;
		bp->attr.bp_addr = breakinfo[breakno].addr;
		bp->attr.bp_len = breakinfo[breakno].len;
		bp->attr.bp_type = breakinfo[breakno].type;
		info->address = breakinfo[breakno].addr;
		info->len = breakinfo[breakno].len;
		info->type = breakinfo[breakno].type;
		val = arch_install_hw_breakpoint(bp);
		if (!val)
			bp->attr.disabled = 0;
	}
	if (!dbg_is_early)
		hw_breakpoint_restore();
}

static int hw_break_reserve_slot(int breakno)
{
	int cpu;
	int cnt = 0;
	struct perf_event **pevent;

	if (dbg_is_early)
		return 0;

	for_each_online_cpu(cpu) {
		cnt++;
		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
		if (dbg_reserve_bp_slot(*pevent))
			goto fail;
	}

	return 0;

fail:
	for_each_online_cpu(cpu) {
		cnt--;
		if (!cnt)
			break;
		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
		dbg_release_bp_slot(*pevent);
	}
	return -1;
}

static int hw_break_release_slot(int breakno)
{
	struct perf_event **pevent;
	int cpu;

	if (dbg_is_early)
		return 0;

	for_each_online_cpu(cpu) {
		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
		if (dbg_release_bp_slot(*pevent))
			/*
			 * The debugger is responsible for handing the retry on
			 * remove failure.
			 */
			return -1;
	}
	return 0;
}

static int
kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
{
	int i;

	for (i = 0; i < HBP_NUM; i++)
		if (breakinfo[i].addr == addr && breakinfo[i].enabled)
			break;
	if (i == HBP_NUM)
		return -1;

	if (hw_break_release_slot(i)) {
		printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
		return -1;
	}
	breakinfo[i].enabled = 0;

	return 0;
}

static void kgdb_remove_all_hw_break(void)
{
	int i;
	int cpu = raw_smp_processor_id();
	struct perf_event *bp;

	for (i = 0; i < HBP_NUM; i++) {
		if (!breakinfo[i].enabled)
			continue;
		bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
		if (!bp->attr.disabled) {
			arch_uninstall_hw_breakpoint(bp);
			bp->attr.disabled = 1;
			continue;
		}
		if (dbg_is_early)
			early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
						 breakinfo[i].type);
		else if (hw_break_release_slot(i))
			printk(KERN_ERR "KGDB: hw bpt remove failed %lx\n",
			       breakinfo[i].addr);
		breakinfo[i].enabled = 0;
	}
}

static int
kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
{
	int i;

	for (i = 0; i < HBP_NUM; i++)
		if (!breakinfo[i].enabled)
			break;
	if (i == HBP_NUM)
		return -1;

	switch (bptype) {
	case BP_HARDWARE_BREAKPOINT:
		len = 1;
		breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
		break;
	case BP_WRITE_WATCHPOINT:
		breakinfo[i].type = X86_BREAKPOINT_WRITE;
		break;
	case BP_ACCESS_WATCHPOINT:
		breakinfo[i].type = X86_BREAKPOINT_RW;
		break;
	default:
		return -1;
	}
	switch (len) {
	case 1:
		breakinfo[i].len = X86_BREAKPOINT_LEN_1;
		break;
	case 2:
		breakinfo[i].len = X86_BREAKPOINT_LEN_2;
		break;
	case 4:
		breakinfo[i].len = X86_BREAKPOINT_LEN_4;
		break;
#ifdef CONFIG_X86_64
	case 8:
		breakinfo[i].len = X86_BREAKPOINT_LEN_8;
		break;
#endif
	default:
		return -1;
	}
	breakinfo[i].addr = addr;
	if (hw_break_reserve_slot(i)) {
		breakinfo[i].addr = 0;
		return -1;
	}
	breakinfo[i].enabled = 1;

	return 0;
}

/**
 *	kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 *	@regs: Current &struct pt_regs.
 *
 *	This function will be called if the particular architecture must
 *	disable hardware debugging while it is processing gdb packets or
 *	handling exception.
 */
static void kgdb_disable_hw_debug(struct pt_regs *regs)
{
	int i;
	int cpu = raw_smp_processor_id();
	struct perf_event *bp;

	/* Disable hardware debugging while we are in kgdb: */
	set_debugreg(0UL, 7);
	for (i = 0; i < HBP_NUM; i++) {
		if (!breakinfo[i].enabled)
			continue;
		if (dbg_is_early) {
			early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
						 breakinfo[i].type);
			continue;
		}
		bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
		if (bp->attr.disabled == 1)
			continue;
		arch_uninstall_hw_breakpoint(bp);
		bp->attr.disabled = 1;
	}
}

#ifdef CONFIG_SMP
/**
 *	kgdb_roundup_cpus - Get other CPUs into a holding pattern
 *	@flags: Current IRQ state
 *
 *	On SMP systems, we need to get the attention of the other CPUs
 *	and get them be in a known state.  This should do what is needed
 *	to get the other CPUs to call kgdb_wait(). Note that on some arches,
 *	the NMI approach is not used for rounding up all the CPUs. For example,
 *	in case of MIPS, smp_call_function() is used to roundup CPUs. In
 *	this case, we have to make sure that interrupts are enabled before
 *	calling smp_call_function(). The argument to this function is
 *	the flags that will be used when restoring the interrupts. There is
 *	local_irq_save() call before kgdb_roundup_cpus().
 *
 *	On non-SMP systems, this is not called.
 */
void kgdb_roundup_cpus(unsigned long flags)
{
	apic->send_IPI_allbutself(APIC_DM_NMI);
}
#endif

/**
 *	kgdb_arch_handle_exception - Handle architecture specific GDB packets.
 *	@vector: The error vector of the exception that happened.
 *	@signo: The signal number of the exception that happened.
 *	@err_code: The error code of the exception that happened.
 *	@remcom_in_buffer: The buffer of the packet we have read.
 *	@remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
 *	@regs: The &struct pt_regs of the current process.
 *
 *	This function MUST handle the 'c' and 's' command packets,
 *	as well packets to set / remove a hardware breakpoint, if used.
 *	If there are additional packets which the hardware needs to handle,
 *	they are handled here.  The code should return -1 if it wants to
 *	process more packets, and a %0 or %1 if it wants to exit from the
 *	kgdb callback.
 */
int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
			       char *remcomInBuffer, char *remcomOutBuffer,
			       struct pt_regs *linux_regs)
{
	unsigned long addr;
	char *ptr;

	switch (remcomInBuffer[0]) {
	case 'c':
	case 's':
		/* try to read optional parameter, pc unchanged if no parm */
		ptr = &remcomInBuffer[1];
		if (kgdb_hex2long(&ptr, &addr))
			linux_regs->ip = addr;
	case 'D':
	case 'k':
		/* clear the trace bit */
		linux_regs->flags &= ~X86_EFLAGS_TF;
		atomic_set(&kgdb_cpu_doing_single_step, -1);

		/* set the trace bit if we're stepping */
		if (remcomInBuffer[0] == 's') {
			linux_regs->flags |= X86_EFLAGS_TF;
			atomic_set(&kgdb_cpu_doing_single_step,
				   raw_smp_processor_id());
		}

		return 0;
	}

	/* this means that we do not want to exit from the handler: */
	return -1;
}

static inline int
single_step_cont(struct pt_regs *regs, struct die_args *args)
{
	/*
	 * Single step exception from kernel space to user space so
	 * eat the exception and continue the process:
	 */
	printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
			"resuming...\n");
	kgdb_arch_handle_exception(args->trapnr, args->signr,
				   args->err, "c", "", regs);
	/*
	 * Reset the BS bit in dr6 (pointed by args->err) to
	 * denote completion of processing
	 */
	(*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;

	return NOTIFY_STOP;
}

static int was_in_debug_nmi[NR_CPUS];

static int kgdb_nmi_handler(unsigned int cmd, struct pt_regs *regs)
{
	switch (cmd) {
	case NMI_LOCAL:
		if (atomic_read(&kgdb_active) != -1) {
			/* KGDB CPU roundup */
			kgdb_nmicallback(raw_smp_processor_id(), regs);
			was_in_debug_nmi[raw_smp_processor_id()] = 1;
			touch_nmi_watchdog();
			return NMI_HANDLED;
		}
		break;

	case NMI_UNKNOWN:
		if (was_in_debug_nmi[raw_smp_processor_id()]) {
			was_in_debug_nmi[raw_smp_processor_id()] = 0;
			return NMI_HANDLED;
		}
		break;
	default:
		/* do nothing */
		break;
	}
	return NMI_DONE;
}

static int __kgdb_notify(struct die_args *args, unsigned long cmd)
{
	struct pt_regs *regs = args->regs;

	switch (cmd) {
	case DIE_DEBUG:
		if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
			if (user_mode(regs))
				return single_step_cont(regs, args);
			break;
		} else if (test_thread_flag(TIF_SINGLESTEP))
			/* This means a user thread is single stepping
			 * a system call which should be ignored
			 */
			return NOTIFY_DONE;
		/* fall through */
	default:
		if (user_mode(regs))
			return NOTIFY_DONE;
	}

	if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
		return NOTIFY_DONE;

	/* Must touch watchdog before return to normal operation */
	touch_nmi_watchdog();
	return NOTIFY_STOP;
}

int kgdb_ll_trap(int cmd, const char *str,
		 struct pt_regs *regs, long err, int trap, int sig)
{
	struct die_args args = {
		.regs	= regs,
		.str	= str,
		.err	= err,
		.trapnr	= trap,
		.signr	= sig,

	};

	if (!kgdb_io_module_registered)
		return NOTIFY_DONE;

	return __kgdb_notify(&args, cmd);
}

static int
kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
{
	unsigned long flags;
	int ret;

	local_irq_save(flags);
	ret = __kgdb_notify(ptr, cmd);
	local_irq_restore(flags);

	return ret;
}

static struct notifier_block kgdb_notifier = {
	.notifier_call	= kgdb_notify,
};

/**
 *	kgdb_arch_init - Perform any architecture specific initalization.
 *
 *	This function will handle the initalization of any architecture
 *	specific callbacks.
 */
int kgdb_arch_init(void)
{
	int retval;

	retval = register_die_notifier(&kgdb_notifier);
	if (retval)
		goto out;

	retval = register_nmi_handler(NMI_LOCAL, kgdb_nmi_handler,
					0, "kgdb");
	if (retval)
		goto out1;

	retval = register_nmi_handler(NMI_UNKNOWN, kgdb_nmi_handler,
					0, "kgdb");

	if (retval)
		goto out2;

	return retval;

out2:
	unregister_nmi_handler(NMI_LOCAL, "kgdb");
out1:
	unregister_die_notifier(&kgdb_notifier);
out:
	return retval;
}

static void kgdb_hw_overflow_handler(struct perf_event *event,
		struct perf_sample_data *data, struct pt_regs *regs)
{
	struct task_struct *tsk = current;
	int i;

	for (i = 0; i < 4; i++)
		if (breakinfo[i].enabled)
			tsk->thread.debugreg6 |= (DR_TRAP0 << i);
}

void kgdb_arch_late(void)
{
	int i, cpu;
	struct perf_event_attr attr;
	struct perf_event **pevent;

	/*
	 * Pre-allocate the hw breakpoint structions in the non-atomic
	 * portion of kgdb because this operation requires mutexs to
	 * complete.
	 */
	hw_breakpoint_init(&attr);
	attr.bp_addr = (unsigned long)kgdb_arch_init;
	attr.bp_len = HW_BREAKPOINT_LEN_1;
	attr.bp_type = HW_BREAKPOINT_W;
	attr.disabled = 1;
	for (i = 0; i < HBP_NUM; i++) {
		if (breakinfo[i].pev)
			continue;
		breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL, NULL);
		if (IS_ERR((void * __force)breakinfo[i].pev)) {
			printk(KERN_ERR "kgdb: Could not allocate hw"
			       "breakpoints\nDisabling the kernel debugger\n");
			breakinfo[i].pev = NULL;
			kgdb_arch_exit();
			return;
		}
		for_each_online_cpu(cpu) {
			pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
			pevent[0]->hw.sample_period = 1;
			pevent[0]->overflow_handler = kgdb_hw_overflow_handler;
			if (pevent[0]->destroy != NULL) {
				pevent[0]->destroy = NULL;
				release_bp_slot(*pevent);
			}
		}
	}
}

/**
 *	kgdb_arch_exit - Perform any architecture specific uninitalization.
 *
 *	This function will handle the uninitalization of any architecture
 *	specific callbacks, for dynamic registration and unregistration.
 */
void kgdb_arch_exit(void)
{
	int i;
	for (i = 0; i < 4; i++) {
		if (breakinfo[i].pev) {
			unregister_wide_hw_breakpoint(breakinfo[i].pev);
			breakinfo[i].pev = NULL;
		}
	}
	unregister_nmi_handler(NMI_UNKNOWN, "kgdb");
	unregister_nmi_handler(NMI_LOCAL, "kgdb");
	unregister_die_notifier(&kgdb_notifier);
}

/**
 *
 *	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.
 *
 * Skip an int3 exception when it occurs after a breakpoint has been
 * removed. Backtrack eip by 1 since the int3 would have caused it to
 * increment by 1.
 */
int kgdb_skipexception(int exception, struct pt_regs *regs)
{
	if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
		regs->ip -= 1;
		return 1;
	}
	return 0;
}

unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
{
	if (exception == 3)
		return instruction_pointer(regs) - 1;
	return instruction_pointer(regs);
}

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

struct kgdb_arch arch_kgdb_ops = {
	/* Breakpoint instruction: */
	.gdb_bpt_instr		= { 0xcc },
	.flags			= KGDB_HW_BREAKPOINT,
	.set_hw_breakpoint	= kgdb_set_hw_break,
	.remove_hw_breakpoint	= kgdb_remove_hw_break,
	.disable_hw_break	= kgdb_disable_hw_debug,
	.remove_all_hw_break	= kgdb_remove_all_hw_break,
	.correct_hw_break	= kgdb_correct_hw_break,
};