kgdb.c revision 12bfa3de63504d879ae427ec1f2884fc46556157 
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#include <asm/apic.h>
51
52struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
53{
54#ifdef CONFIG_X86_32
55	{ "ax", 4, offsetof(struct pt_regs, ax) },
56	{ "cx", 4, offsetof(struct pt_regs, cx) },
57	{ "dx", 4, offsetof(struct pt_regs, dx) },
58	{ "bx", 4, offsetof(struct pt_regs, bx) },
59	{ "sp", 4, offsetof(struct pt_regs, sp) },
60	{ "bp", 4, offsetof(struct pt_regs, bp) },
61	{ "si", 4, offsetof(struct pt_regs, si) },
62	{ "di", 4, offsetof(struct pt_regs, di) },
63	{ "ip", 4, offsetof(struct pt_regs, ip) },
64	{ "flags", 4, offsetof(struct pt_regs, flags) },
65	{ "cs", 4, offsetof(struct pt_regs, cs) },
66	{ "ss", 4, offsetof(struct pt_regs, ss) },
67	{ "ds", 4, offsetof(struct pt_regs, ds) },
68	{ "es", 4, offsetof(struct pt_regs, es) },
69	{ "fs", 4, -1 },
70	{ "gs", 4, -1 },
71#else
72	{ "ax", 8, offsetof(struct pt_regs, ax) },
73	{ "bx", 8, offsetof(struct pt_regs, bx) },
74	{ "cx", 8, offsetof(struct pt_regs, cx) },
75	{ "dx", 8, offsetof(struct pt_regs, dx) },
76	{ "si", 8, offsetof(struct pt_regs, dx) },
77	{ "di", 8, offsetof(struct pt_regs, di) },
78	{ "bp", 8, offsetof(struct pt_regs, bp) },
79	{ "sp", 8, offsetof(struct pt_regs, sp) },
80	{ "r8", 8, offsetof(struct pt_regs, r8) },
81	{ "r9", 8, offsetof(struct pt_regs, r9) },
82	{ "r10", 8, offsetof(struct pt_regs, r10) },
83	{ "r11", 8, offsetof(struct pt_regs, r11) },
84	{ "r12", 8, offsetof(struct pt_regs, r12) },
85	{ "r13", 8, offsetof(struct pt_regs, r13) },
86	{ "r14", 8, offsetof(struct pt_regs, r14) },
87	{ "r15", 8, offsetof(struct pt_regs, r15) },
88	{ "ip", 8, offsetof(struct pt_regs, ip) },
89	{ "flags", 4, offsetof(struct pt_regs, flags) },
90	{ "cs", 4, offsetof(struct pt_regs, cs) },
91	{ "ss", 4, offsetof(struct pt_regs, ss) },
92#endif
93};
94
95int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
96{
97	if (
98#ifdef CONFIG_X86_32
99	    regno == GDB_SS || regno == GDB_FS || regno == GDB_GS ||
100#endif
101	    regno == GDB_SP || regno == GDB_ORIG_AX)
102		return 0;
103
104	if (dbg_reg_def[regno].offset != -1)
105		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
106		       dbg_reg_def[regno].size);
107	return 0;
108}
109
110char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
111{
112	if (regno == GDB_ORIG_AX) {
113		memcpy(mem, &regs->orig_ax, sizeof(regs->orig_ax));
114		return "orig_ax";
115	}
116	if (regno >= DBG_MAX_REG_NUM || regno < 0)
117		return NULL;
118
119	if (dbg_reg_def[regno].offset != -1)
120		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
121		       dbg_reg_def[regno].size);
122
123	switch (regno) {
124#ifdef CONFIG_X86_32
125	case GDB_SS:
126		if (!user_mode_vm(regs))
127			*(unsigned long *)mem = __KERNEL_DS;
128		break;
129	case GDB_SP:
130		if (!user_mode_vm(regs))
131			*(unsigned long *)mem = kernel_stack_pointer(regs);
132		break;
133	case GDB_GS:
134	case GDB_FS:
135		*(unsigned long *)mem = 0xFFFF;
136		break;
137#endif
138	}
139	return dbg_reg_def[regno].name;
140}
141
142/**
143 *	sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
144 *	@gdb_regs: A pointer to hold the registers in the order GDB wants.
145 *	@p: The &struct task_struct of the desired process.
146 *
147 *	Convert the register values of the sleeping process in @p to
148 *	the format that GDB expects.
149 *	This function is called when kgdb does not have access to the
150 *	&struct pt_regs and therefore it should fill the gdb registers
151 *	@gdb_regs with what has	been saved in &struct thread_struct
152 *	thread field during switch_to.
153 */
154void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
155{
156#ifndef CONFIG_X86_32
157	u32 *gdb_regs32 = (u32 *)gdb_regs;
158#endif
159	gdb_regs[GDB_AX]	= 0;
160	gdb_regs[GDB_BX]	= 0;
161	gdb_regs[GDB_CX]	= 0;
162	gdb_regs[GDB_DX]	= 0;
163	gdb_regs[GDB_SI]	= 0;
164	gdb_regs[GDB_DI]	= 0;
165	gdb_regs[GDB_BP]	= *(unsigned long *)p->thread.sp;
166#ifdef CONFIG_X86_32
167	gdb_regs[GDB_DS]	= __KERNEL_DS;
168	gdb_regs[GDB_ES]	= __KERNEL_DS;
169	gdb_regs[GDB_PS]	= 0;
170	gdb_regs[GDB_CS]	= __KERNEL_CS;
171	gdb_regs[GDB_PC]	= p->thread.ip;
172	gdb_regs[GDB_SS]	= __KERNEL_DS;
173	gdb_regs[GDB_FS]	= 0xFFFF;
174	gdb_regs[GDB_GS]	= 0xFFFF;
175#else
176	gdb_regs32[GDB_PS]	= *(unsigned long *)(p->thread.sp + 8);
177	gdb_regs32[GDB_CS]	= __KERNEL_CS;
178	gdb_regs32[GDB_SS]	= __KERNEL_DS;
179	gdb_regs[GDB_PC]	= 0;
180	gdb_regs[GDB_R8]	= 0;
181	gdb_regs[GDB_R9]	= 0;
182	gdb_regs[GDB_R10]	= 0;
183	gdb_regs[GDB_R11]	= 0;
184	gdb_regs[GDB_R12]	= 0;
185	gdb_regs[GDB_R13]	= 0;
186	gdb_regs[GDB_R14]	= 0;
187	gdb_regs[GDB_R15]	= 0;
188#endif
189	gdb_regs[GDB_SP]	= p->thread.sp;
190}
191
192static struct hw_breakpoint {
193	unsigned		enabled;
194	unsigned long		addr;
195	int			len;
196	int			type;
197	struct perf_event	**pev;
198} breakinfo[4];
199
200static unsigned long early_dr7;
201
202static void kgdb_correct_hw_break(void)
203{
204	int breakno;
205
206	for (breakno = 0; breakno < 4; breakno++) {
207		struct perf_event *bp;
208		struct arch_hw_breakpoint *info;
209		int val;
210		int cpu = raw_smp_processor_id();
211		if (!breakinfo[breakno].enabled)
212			continue;
213		if (dbg_is_early) {
214			set_debugreg(breakinfo[breakno].addr, breakno);
215			early_dr7 |= encode_dr7(breakno,
216						breakinfo[breakno].len,
217						breakinfo[breakno].type);
218			set_debugreg(early_dr7, 7);
219			continue;
220		}
221		bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
222		info = counter_arch_bp(bp);
223		if (bp->attr.disabled != 1)
224			continue;
225		bp->attr.bp_addr = breakinfo[breakno].addr;
226		bp->attr.bp_len = breakinfo[breakno].len;
227		bp->attr.bp_type = breakinfo[breakno].type;
228		info->address = breakinfo[breakno].addr;
229		info->len = breakinfo[breakno].len;
230		info->type = breakinfo[breakno].type;
231		val = arch_install_hw_breakpoint(bp);
232		if (!val)
233			bp->attr.disabled = 0;
234	}
235	if (!dbg_is_early)
236		hw_breakpoint_restore();
237}
238
239static int hw_break_reserve_slot(int breakno)
240{
241	int cpu;
242	int cnt = 0;
243	struct perf_event **pevent;
244
245	if (dbg_is_early)
246		return 0;
247
248	for_each_online_cpu(cpu) {
249		cnt++;
250		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
251		if (dbg_reserve_bp_slot(*pevent))
252			goto fail;
253	}
254
255	return 0;
256
257fail:
258	for_each_online_cpu(cpu) {
259		cnt--;
260		if (!cnt)
261			break;
262		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
263		dbg_release_bp_slot(*pevent);
264	}
265	return -1;
266}
267
268static int hw_break_release_slot(int breakno)
269{
270	struct perf_event **pevent;
271	int cpu;
272
273	if (dbg_is_early)
274		return 0;
275
276	for_each_online_cpu(cpu) {
277		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
278		if (dbg_release_bp_slot(*pevent))
279			/*
280			 * The debugger is responisble for handing the retry on
281			 * remove failure.
282			 */
283			return -1;
284	}
285	return 0;
286}
287
288static int
289kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
290{
291	int i;
292
293	for (i = 0; i < 4; i++)
294		if (breakinfo[i].addr == addr && breakinfo[i].enabled)
295			break;
296	if (i == 4)
297		return -1;
298
299	if (hw_break_release_slot(i)) {
300		printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
301		return -1;
302	}
303	breakinfo[i].enabled = 0;
304
305	return 0;
306}
307
308static void kgdb_remove_all_hw_break(void)
309{
310	int i;
311	int cpu = raw_smp_processor_id();
312	struct perf_event *bp;
313
314	for (i = 0; i < 4; i++) {
315		if (!breakinfo[i].enabled)
316			continue;
317		bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
318		if (bp->attr.disabled == 1)
319			continue;
320		if (dbg_is_early)
321			early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
322						 breakinfo[i].type);
323		else
324			arch_uninstall_hw_breakpoint(bp);
325		bp->attr.disabled = 1;
326	}
327}
328
329static int
330kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
331{
332	int i;
333
334	for (i = 0; i < 4; i++)
335		if (!breakinfo[i].enabled)
336			break;
337	if (i == 4)
338		return -1;
339
340	switch (bptype) {
341	case BP_HARDWARE_BREAKPOINT:
342		len = 1;
343		breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
344		break;
345	case BP_WRITE_WATCHPOINT:
346		breakinfo[i].type = X86_BREAKPOINT_WRITE;
347		break;
348	case BP_ACCESS_WATCHPOINT:
349		breakinfo[i].type = X86_BREAKPOINT_RW;
350		break;
351	default:
352		return -1;
353	}
354	switch (len) {
355	case 1:
356		breakinfo[i].len = X86_BREAKPOINT_LEN_1;
357		break;
358	case 2:
359		breakinfo[i].len = X86_BREAKPOINT_LEN_2;
360		break;
361	case 4:
362		breakinfo[i].len = X86_BREAKPOINT_LEN_4;
363		break;
364#ifdef CONFIG_X86_64
365	case 8:
366		breakinfo[i].len = X86_BREAKPOINT_LEN_8;
367		break;
368#endif
369	default:
370		return -1;
371	}
372	breakinfo[i].addr = addr;
373	if (hw_break_reserve_slot(i)) {
374		breakinfo[i].addr = 0;
375		return -1;
376	}
377	breakinfo[i].enabled = 1;
378
379	return 0;
380}
381
382/**
383 *	kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
384 *	@regs: Current &struct pt_regs.
385 *
386 *	This function will be called if the particular architecture must
387 *	disable hardware debugging while it is processing gdb packets or
388 *	handling exception.
389 */
390void kgdb_disable_hw_debug(struct pt_regs *regs)
391{
392	int i;
393	int cpu = raw_smp_processor_id();
394	struct perf_event *bp;
395
396	/* Disable hardware debugging while we are in kgdb: */
397	set_debugreg(0UL, 7);
398	for (i = 0; i < 4; i++) {
399		if (!breakinfo[i].enabled)
400			continue;
401		if (dbg_is_early) {
402			early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
403						 breakinfo[i].type);
404			continue;
405		}
406		bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
407		if (bp->attr.disabled == 1)
408			continue;
409		arch_uninstall_hw_breakpoint(bp);
410		bp->attr.disabled = 1;
411	}
412}
413
414#ifdef CONFIG_SMP
415/**
416 *	kgdb_roundup_cpus - Get other CPUs into a holding pattern
417 *	@flags: Current IRQ state
418 *
419 *	On SMP systems, we need to get the attention of the other CPUs
420 *	and get them be in a known state.  This should do what is needed
421 *	to get the other CPUs to call kgdb_wait(). Note that on some arches,
422 *	the NMI approach is not used for rounding up all the CPUs. For example,
423 *	in case of MIPS, smp_call_function() is used to roundup CPUs. In
424 *	this case, we have to make sure that interrupts are enabled before
425 *	calling smp_call_function(). The argument to this function is
426 *	the flags that will be used when restoring the interrupts. There is
427 *	local_irq_save() call before kgdb_roundup_cpus().
428 *
429 *	On non-SMP systems, this is not called.
430 */
431void kgdb_roundup_cpus(unsigned long flags)
432{
433	apic->send_IPI_allbutself(APIC_DM_NMI);
434}
435#endif
436
437/**
438 *	kgdb_arch_handle_exception - Handle architecture specific GDB packets.
439 *	@vector: The error vector of the exception that happened.
440 *	@signo: The signal number of the exception that happened.
441 *	@err_code: The error code of the exception that happened.
442 *	@remcom_in_buffer: The buffer of the packet we have read.
443 *	@remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
444 *	@regs: The &struct pt_regs of the current process.
445 *
446 *	This function MUST handle the 'c' and 's' command packets,
447 *	as well packets to set / remove a hardware breakpoint, if used.
448 *	If there are additional packets which the hardware needs to handle,
449 *	they are handled here.  The code should return -1 if it wants to
450 *	process more packets, and a %0 or %1 if it wants to exit from the
451 *	kgdb callback.
452 */
453int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
454			       char *remcomInBuffer, char *remcomOutBuffer,
455			       struct pt_regs *linux_regs)
456{
457	unsigned long addr;
458	char *ptr;
459	int newPC;
460
461	switch (remcomInBuffer[0]) {
462	case 'c':
463	case 's':
464		/* try to read optional parameter, pc unchanged if no parm */
465		ptr = &remcomInBuffer[1];
466		if (kgdb_hex2long(&ptr, &addr))
467			linux_regs->ip = addr;
468	case 'D':
469	case 'k':
470		newPC = linux_regs->ip;
471
472		/* clear the trace bit */
473		linux_regs->flags &= ~X86_EFLAGS_TF;
474		atomic_set(&kgdb_cpu_doing_single_step, -1);
475
476		/* set the trace bit if we're stepping */
477		if (remcomInBuffer[0] == 's') {
478			linux_regs->flags |= X86_EFLAGS_TF;
479			atomic_set(&kgdb_cpu_doing_single_step,
480				   raw_smp_processor_id());
481		}
482
483		kgdb_correct_hw_break();
484
485		return 0;
486	}
487
488	/* this means that we do not want to exit from the handler: */
489	return -1;
490}
491
492static inline int
493single_step_cont(struct pt_regs *regs, struct die_args *args)
494{
495	/*
496	 * Single step exception from kernel space to user space so
497	 * eat the exception and continue the process:
498	 */
499	printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
500			"resuming...\n");
501	kgdb_arch_handle_exception(args->trapnr, args->signr,
502				   args->err, "c", "", regs);
503	/*
504	 * Reset the BS bit in dr6 (pointed by args->err) to
505	 * denote completion of processing
506	 */
507	(*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
508
509	return NOTIFY_STOP;
510}
511
512static int was_in_debug_nmi[NR_CPUS];
513
514static int __kgdb_notify(struct die_args *args, unsigned long cmd)
515{
516	struct pt_regs *regs = args->regs;
517
518	switch (cmd) {
519	case DIE_NMI:
520		if (atomic_read(&kgdb_active) != -1) {
521			/* KGDB CPU roundup */
522			kgdb_nmicallback(raw_smp_processor_id(), regs);
523			was_in_debug_nmi[raw_smp_processor_id()] = 1;
524			touch_nmi_watchdog();
525			return NOTIFY_STOP;
526		}
527		return NOTIFY_DONE;
528
529	case DIE_NMI_IPI:
530		/* Just ignore, we will handle the roundup on DIE_NMI. */
531		return NOTIFY_DONE;
532
533	case DIE_NMIUNKNOWN:
534		if (was_in_debug_nmi[raw_smp_processor_id()]) {
535			was_in_debug_nmi[raw_smp_processor_id()] = 0;
536			return NOTIFY_STOP;
537		}
538		return NOTIFY_DONE;
539
540	case DIE_NMIWATCHDOG:
541		if (atomic_read(&kgdb_active) != -1) {
542			/* KGDB CPU roundup: */
543			kgdb_nmicallback(raw_smp_processor_id(), regs);
544			return NOTIFY_STOP;
545		}
546		/* Enter debugger: */
547		break;
548
549	case DIE_DEBUG:
550		if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
551			if (user_mode(regs))
552				return single_step_cont(regs, args);
553			break;
554		} else if (test_thread_flag(TIF_SINGLESTEP))
555			/* This means a user thread is single stepping
556			 * a system call which should be ignored
557			 */
558			return NOTIFY_DONE;
559		/* fall through */
560	default:
561		if (user_mode(regs))
562			return NOTIFY_DONE;
563	}
564
565	if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
566		return NOTIFY_DONE;
567
568	/* Must touch watchdog before return to normal operation */
569	touch_nmi_watchdog();
570	return NOTIFY_STOP;
571}
572
573int kgdb_ll_trap(int cmd, const char *str,
574		 struct pt_regs *regs, long err, int trap, int sig)
575{
576	struct die_args args = {
577		.regs	= regs,
578		.str	= str,
579		.err	= err,
580		.trapnr	= trap,
581		.signr	= sig,
582
583	};
584
585	if (!kgdb_io_module_registered)
586		return NOTIFY_DONE;
587
588	return __kgdb_notify(&args, cmd);
589}
590
591static int
592kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
593{
594	unsigned long flags;
595	int ret;
596
597	local_irq_save(flags);
598	ret = __kgdb_notify(ptr, cmd);
599	local_irq_restore(flags);
600
601	return ret;
602}
603
604static struct notifier_block kgdb_notifier = {
605	.notifier_call	= kgdb_notify,
606
607	/*
608	 * Lowest-prio notifier priority, we want to be notified last:
609	 */
610	.priority	= -INT_MAX,
611};
612
613/**
614 *	kgdb_arch_init - Perform any architecture specific initalization.
615 *
616 *	This function will handle the initalization of any architecture
617 *	specific callbacks.
618 */
619int kgdb_arch_init(void)
620{
621	return register_die_notifier(&kgdb_notifier);
622}
623
624static void kgdb_hw_overflow_handler(struct perf_event *event, int nmi,
625		struct perf_sample_data *data, struct pt_regs *regs)
626{
627	kgdb_ll_trap(DIE_DEBUG, "debug", regs, 0, 0, SIGTRAP);
628}
629
630void kgdb_arch_late(void)
631{
632	int i, cpu;
633	struct perf_event_attr attr;
634	struct perf_event **pevent;
635
636	/*
637	 * Pre-allocate the hw breakpoint structions in the non-atomic
638	 * portion of kgdb because this operation requires mutexs to
639	 * complete.
640	 */
641	hw_breakpoint_init(&attr);
642	attr.bp_addr = (unsigned long)kgdb_arch_init;
643	attr.bp_len = HW_BREAKPOINT_LEN_1;
644	attr.bp_type = HW_BREAKPOINT_W;
645	attr.disabled = 1;
646	for (i = 0; i < 4; i++) {
647		if (breakinfo[i].pev)
648			continue;
649		breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL);
650		if (IS_ERR(breakinfo[i].pev)) {
651			printk(KERN_ERR "kgdb: Could not allocate hw"
652			       "breakpoints\nDisabling the kernel debugger\n");
653			breakinfo[i].pev = NULL;
654			kgdb_arch_exit();
655			return;
656		}
657		for_each_online_cpu(cpu) {
658			pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
659			pevent[0]->hw.sample_period = 1;
660			pevent[0]->overflow_handler = kgdb_hw_overflow_handler;
661			if (pevent[0]->destroy != NULL) {
662				pevent[0]->destroy = NULL;
663				release_bp_slot(*pevent);
664			}
665		}
666	}
667}
668
669/**
670 *	kgdb_arch_exit - Perform any architecture specific uninitalization.
671 *
672 *	This function will handle the uninitalization of any architecture
673 *	specific callbacks, for dynamic registration and unregistration.
674 */
675void kgdb_arch_exit(void)
676{
677	int i;
678	for (i = 0; i < 4; i++) {
679		if (breakinfo[i].pev) {
680			unregister_wide_hw_breakpoint(breakinfo[i].pev);
681			breakinfo[i].pev = NULL;
682		}
683	}
684	unregister_die_notifier(&kgdb_notifier);
685}
686
687/**
688 *
689 *	kgdb_skipexception - Bail out of KGDB when we've been triggered.
690 *	@exception: Exception vector number
691 *	@regs: Current &struct pt_regs.
692 *
693 *	On some architectures we need to skip a breakpoint exception when
694 *	it occurs after a breakpoint has been removed.
695 *
696 * Skip an int3 exception when it occurs after a breakpoint has been
697 * removed. Backtrack eip by 1 since the int3 would have caused it to
698 * increment by 1.
699 */
700int kgdb_skipexception(int exception, struct pt_regs *regs)
701{
702	if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
703		regs->ip -= 1;
704		return 1;
705	}
706	return 0;
707}
708
709unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
710{
711	if (exception == 3)
712		return instruction_pointer(regs) - 1;
713	return instruction_pointer(regs);
714}
715
716void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
717{
718	regs->ip = ip;
719}
720
721struct kgdb_arch arch_kgdb_ops = {
722	/* Breakpoint instruction: */
723	.gdb_bpt_instr		= { 0xcc },
724	.flags			= KGDB_HW_BREAKPOINT,
725	.set_hw_breakpoint	= kgdb_set_hw_break,
726	.remove_hw_breakpoint	= kgdb_remove_hw_break,
727	.remove_all_hw_break	= kgdb_remove_all_hw_break,
728	.correct_hw_break	= kgdb_correct_hw_break,
729};
730