xref: /openbmc/linux/arch/x86/kernel/kgdb.c (revision 81d67439)
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 #include <asm/nmi.h>
52 
53 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
54 {
55 #ifdef CONFIG_X86_32
56 	{ "ax", 4, offsetof(struct pt_regs, ax) },
57 	{ "cx", 4, offsetof(struct pt_regs, cx) },
58 	{ "dx", 4, offsetof(struct pt_regs, dx) },
59 	{ "bx", 4, offsetof(struct pt_regs, bx) },
60 	{ "sp", 4, offsetof(struct pt_regs, sp) },
61 	{ "bp", 4, offsetof(struct pt_regs, bp) },
62 	{ "si", 4, offsetof(struct pt_regs, si) },
63 	{ "di", 4, offsetof(struct pt_regs, di) },
64 	{ "ip", 4, offsetof(struct pt_regs, ip) },
65 	{ "flags", 4, offsetof(struct pt_regs, flags) },
66 	{ "cs", 4, offsetof(struct pt_regs, cs) },
67 	{ "ss", 4, offsetof(struct pt_regs, ss) },
68 	{ "ds", 4, offsetof(struct pt_regs, ds) },
69 	{ "es", 4, offsetof(struct pt_regs, es) },
70 	{ "fs", 4, -1 },
71 	{ "gs", 4, -1 },
72 #else
73 	{ "ax", 8, offsetof(struct pt_regs, ax) },
74 	{ "bx", 8, offsetof(struct pt_regs, bx) },
75 	{ "cx", 8, offsetof(struct pt_regs, cx) },
76 	{ "dx", 8, offsetof(struct pt_regs, dx) },
77 	{ "si", 8, offsetof(struct pt_regs, dx) },
78 	{ "di", 8, offsetof(struct pt_regs, di) },
79 	{ "bp", 8, offsetof(struct pt_regs, bp) },
80 	{ "sp", 8, offsetof(struct pt_regs, sp) },
81 	{ "r8", 8, offsetof(struct pt_regs, r8) },
82 	{ "r9", 8, offsetof(struct pt_regs, r9) },
83 	{ "r10", 8, offsetof(struct pt_regs, r10) },
84 	{ "r11", 8, offsetof(struct pt_regs, r11) },
85 	{ "r12", 8, offsetof(struct pt_regs, r12) },
86 	{ "r13", 8, offsetof(struct pt_regs, r13) },
87 	{ "r14", 8, offsetof(struct pt_regs, r14) },
88 	{ "r15", 8, offsetof(struct pt_regs, r15) },
89 	{ "ip", 8, offsetof(struct pt_regs, ip) },
90 	{ "flags", 4, offsetof(struct pt_regs, flags) },
91 	{ "cs", 4, offsetof(struct pt_regs, cs) },
92 	{ "ss", 4, offsetof(struct pt_regs, ss) },
93 #endif
94 };
95 
96 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
97 {
98 	if (
99 #ifdef CONFIG_X86_32
100 	    regno == GDB_SS || regno == GDB_FS || regno == GDB_GS ||
101 #endif
102 	    regno == GDB_SP || regno == GDB_ORIG_AX)
103 		return 0;
104 
105 	if (dbg_reg_def[regno].offset != -1)
106 		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
107 		       dbg_reg_def[regno].size);
108 	return 0;
109 }
110 
111 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
112 {
113 	if (regno == GDB_ORIG_AX) {
114 		memcpy(mem, &regs->orig_ax, sizeof(regs->orig_ax));
115 		return "orig_ax";
116 	}
117 	if (regno >= DBG_MAX_REG_NUM || regno < 0)
118 		return NULL;
119 
120 	if (dbg_reg_def[regno].offset != -1)
121 		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
122 		       dbg_reg_def[regno].size);
123 
124 #ifdef CONFIG_X86_32
125 	switch (regno) {
126 	case GDB_SS:
127 		if (!user_mode_vm(regs))
128 			*(unsigned long *)mem = __KERNEL_DS;
129 		break;
130 	case GDB_SP:
131 		if (!user_mode_vm(regs))
132 			*(unsigned long *)mem = kernel_stack_pointer(regs);
133 		break;
134 	case GDB_GS:
135 	case GDB_FS:
136 		*(unsigned long *)mem = 0xFFFF;
137 		break;
138 	}
139 #endif
140 	return dbg_reg_def[regno].name;
141 }
142 
143 /**
144  *	sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
145  *	@gdb_regs: A pointer to hold the registers in the order GDB wants.
146  *	@p: The &struct task_struct of the desired process.
147  *
148  *	Convert the register values of the sleeping process in @p to
149  *	the format that GDB expects.
150  *	This function is called when kgdb does not have access to the
151  *	&struct pt_regs and therefore it should fill the gdb registers
152  *	@gdb_regs with what has	been saved in &struct thread_struct
153  *	thread field during switch_to.
154  */
155 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
156 {
157 #ifndef CONFIG_X86_32
158 	u32 *gdb_regs32 = (u32 *)gdb_regs;
159 #endif
160 	gdb_regs[GDB_AX]	= 0;
161 	gdb_regs[GDB_BX]	= 0;
162 	gdb_regs[GDB_CX]	= 0;
163 	gdb_regs[GDB_DX]	= 0;
164 	gdb_regs[GDB_SI]	= 0;
165 	gdb_regs[GDB_DI]	= 0;
166 	gdb_regs[GDB_BP]	= *(unsigned long *)p->thread.sp;
167 #ifdef CONFIG_X86_32
168 	gdb_regs[GDB_DS]	= __KERNEL_DS;
169 	gdb_regs[GDB_ES]	= __KERNEL_DS;
170 	gdb_regs[GDB_PS]	= 0;
171 	gdb_regs[GDB_CS]	= __KERNEL_CS;
172 	gdb_regs[GDB_PC]	= p->thread.ip;
173 	gdb_regs[GDB_SS]	= __KERNEL_DS;
174 	gdb_regs[GDB_FS]	= 0xFFFF;
175 	gdb_regs[GDB_GS]	= 0xFFFF;
176 #else
177 	gdb_regs32[GDB_PS]	= *(unsigned long *)(p->thread.sp + 8);
178 	gdb_regs32[GDB_CS]	= __KERNEL_CS;
179 	gdb_regs32[GDB_SS]	= __KERNEL_DS;
180 	gdb_regs[GDB_PC]	= 0;
181 	gdb_regs[GDB_R8]	= 0;
182 	gdb_regs[GDB_R9]	= 0;
183 	gdb_regs[GDB_R10]	= 0;
184 	gdb_regs[GDB_R11]	= 0;
185 	gdb_regs[GDB_R12]	= 0;
186 	gdb_regs[GDB_R13]	= 0;
187 	gdb_regs[GDB_R14]	= 0;
188 	gdb_regs[GDB_R15]	= 0;
189 #endif
190 	gdb_regs[GDB_SP]	= p->thread.sp;
191 }
192 
193 static struct hw_breakpoint {
194 	unsigned		enabled;
195 	unsigned long		addr;
196 	int			len;
197 	int			type;
198 	struct perf_event	* __percpu *pev;
199 } breakinfo[HBP_NUM];
200 
201 static unsigned long early_dr7;
202 
203 static void kgdb_correct_hw_break(void)
204 {
205 	int breakno;
206 
207 	for (breakno = 0; breakno < HBP_NUM; breakno++) {
208 		struct perf_event *bp;
209 		struct arch_hw_breakpoint *info;
210 		int val;
211 		int cpu = raw_smp_processor_id();
212 		if (!breakinfo[breakno].enabled)
213 			continue;
214 		if (dbg_is_early) {
215 			set_debugreg(breakinfo[breakno].addr, breakno);
216 			early_dr7 |= encode_dr7(breakno,
217 						breakinfo[breakno].len,
218 						breakinfo[breakno].type);
219 			set_debugreg(early_dr7, 7);
220 			continue;
221 		}
222 		bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
223 		info = counter_arch_bp(bp);
224 		if (bp->attr.disabled != 1)
225 			continue;
226 		bp->attr.bp_addr = breakinfo[breakno].addr;
227 		bp->attr.bp_len = breakinfo[breakno].len;
228 		bp->attr.bp_type = breakinfo[breakno].type;
229 		info->address = breakinfo[breakno].addr;
230 		info->len = breakinfo[breakno].len;
231 		info->type = breakinfo[breakno].type;
232 		val = arch_install_hw_breakpoint(bp);
233 		if (!val)
234 			bp->attr.disabled = 0;
235 	}
236 	if (!dbg_is_early)
237 		hw_breakpoint_restore();
238 }
239 
240 static int hw_break_reserve_slot(int breakno)
241 {
242 	int cpu;
243 	int cnt = 0;
244 	struct perf_event **pevent;
245 
246 	if (dbg_is_early)
247 		return 0;
248 
249 	for_each_online_cpu(cpu) {
250 		cnt++;
251 		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
252 		if (dbg_reserve_bp_slot(*pevent))
253 			goto fail;
254 	}
255 
256 	return 0;
257 
258 fail:
259 	for_each_online_cpu(cpu) {
260 		cnt--;
261 		if (!cnt)
262 			break;
263 		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
264 		dbg_release_bp_slot(*pevent);
265 	}
266 	return -1;
267 }
268 
269 static int hw_break_release_slot(int breakno)
270 {
271 	struct perf_event **pevent;
272 	int cpu;
273 
274 	if (dbg_is_early)
275 		return 0;
276 
277 	for_each_online_cpu(cpu) {
278 		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
279 		if (dbg_release_bp_slot(*pevent))
280 			/*
281 			 * The debugger is responsible for handing the retry on
282 			 * remove failure.
283 			 */
284 			return -1;
285 	}
286 	return 0;
287 }
288 
289 static int
290 kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
291 {
292 	int i;
293 
294 	for (i = 0; i < HBP_NUM; i++)
295 		if (breakinfo[i].addr == addr && breakinfo[i].enabled)
296 			break;
297 	if (i == HBP_NUM)
298 		return -1;
299 
300 	if (hw_break_release_slot(i)) {
301 		printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
302 		return -1;
303 	}
304 	breakinfo[i].enabled = 0;
305 
306 	return 0;
307 }
308 
309 static void kgdb_remove_all_hw_break(void)
310 {
311 	int i;
312 	int cpu = raw_smp_processor_id();
313 	struct perf_event *bp;
314 
315 	for (i = 0; i < HBP_NUM; i++) {
316 		if (!breakinfo[i].enabled)
317 			continue;
318 		bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
319 		if (!bp->attr.disabled) {
320 			arch_uninstall_hw_breakpoint(bp);
321 			bp->attr.disabled = 1;
322 			continue;
323 		}
324 		if (dbg_is_early)
325 			early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
326 						 breakinfo[i].type);
327 		else if (hw_break_release_slot(i))
328 			printk(KERN_ERR "KGDB: hw bpt remove failed %lx\n",
329 			       breakinfo[i].addr);
330 		breakinfo[i].enabled = 0;
331 	}
332 }
333 
334 static int
335 kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
336 {
337 	int i;
338 
339 	for (i = 0; i < HBP_NUM; i++)
340 		if (!breakinfo[i].enabled)
341 			break;
342 	if (i == HBP_NUM)
343 		return -1;
344 
345 	switch (bptype) {
346 	case BP_HARDWARE_BREAKPOINT:
347 		len = 1;
348 		breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
349 		break;
350 	case BP_WRITE_WATCHPOINT:
351 		breakinfo[i].type = X86_BREAKPOINT_WRITE;
352 		break;
353 	case BP_ACCESS_WATCHPOINT:
354 		breakinfo[i].type = X86_BREAKPOINT_RW;
355 		break;
356 	default:
357 		return -1;
358 	}
359 	switch (len) {
360 	case 1:
361 		breakinfo[i].len = X86_BREAKPOINT_LEN_1;
362 		break;
363 	case 2:
364 		breakinfo[i].len = X86_BREAKPOINT_LEN_2;
365 		break;
366 	case 4:
367 		breakinfo[i].len = X86_BREAKPOINT_LEN_4;
368 		break;
369 #ifdef CONFIG_X86_64
370 	case 8:
371 		breakinfo[i].len = X86_BREAKPOINT_LEN_8;
372 		break;
373 #endif
374 	default:
375 		return -1;
376 	}
377 	breakinfo[i].addr = addr;
378 	if (hw_break_reserve_slot(i)) {
379 		breakinfo[i].addr = 0;
380 		return -1;
381 	}
382 	breakinfo[i].enabled = 1;
383 
384 	return 0;
385 }
386 
387 /**
388  *	kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
389  *	@regs: Current &struct pt_regs.
390  *
391  *	This function will be called if the particular architecture must
392  *	disable hardware debugging while it is processing gdb packets or
393  *	handling exception.
394  */
395 static void kgdb_disable_hw_debug(struct pt_regs *regs)
396 {
397 	int i;
398 	int cpu = raw_smp_processor_id();
399 	struct perf_event *bp;
400 
401 	/* Disable hardware debugging while we are in kgdb: */
402 	set_debugreg(0UL, 7);
403 	for (i = 0; i < HBP_NUM; i++) {
404 		if (!breakinfo[i].enabled)
405 			continue;
406 		if (dbg_is_early) {
407 			early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
408 						 breakinfo[i].type);
409 			continue;
410 		}
411 		bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
412 		if (bp->attr.disabled == 1)
413 			continue;
414 		arch_uninstall_hw_breakpoint(bp);
415 		bp->attr.disabled = 1;
416 	}
417 }
418 
419 #ifdef CONFIG_SMP
420 /**
421  *	kgdb_roundup_cpus - Get other CPUs into a holding pattern
422  *	@flags: Current IRQ state
423  *
424  *	On SMP systems, we need to get the attention of the other CPUs
425  *	and get them be in a known state.  This should do what is needed
426  *	to get the other CPUs to call kgdb_wait(). Note that on some arches,
427  *	the NMI approach is not used for rounding up all the CPUs. For example,
428  *	in case of MIPS, smp_call_function() is used to roundup CPUs. In
429  *	this case, we have to make sure that interrupts are enabled before
430  *	calling smp_call_function(). The argument to this function is
431  *	the flags that will be used when restoring the interrupts. There is
432  *	local_irq_save() call before kgdb_roundup_cpus().
433  *
434  *	On non-SMP systems, this is not called.
435  */
436 void kgdb_roundup_cpus(unsigned long flags)
437 {
438 	apic->send_IPI_allbutself(APIC_DM_NMI);
439 }
440 #endif
441 
442 /**
443  *	kgdb_arch_handle_exception - Handle architecture specific GDB packets.
444  *	@vector: The error vector of the exception that happened.
445  *	@signo: The signal number of the exception that happened.
446  *	@err_code: The error code of the exception that happened.
447  *	@remcom_in_buffer: The buffer of the packet we have read.
448  *	@remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
449  *	@regs: The &struct pt_regs of the current process.
450  *
451  *	This function MUST handle the 'c' and 's' command packets,
452  *	as well packets to set / remove a hardware breakpoint, if used.
453  *	If there are additional packets which the hardware needs to handle,
454  *	they are handled here.  The code should return -1 if it wants to
455  *	process more packets, and a %0 or %1 if it wants to exit from the
456  *	kgdb callback.
457  */
458 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
459 			       char *remcomInBuffer, char *remcomOutBuffer,
460 			       struct pt_regs *linux_regs)
461 {
462 	unsigned long addr;
463 	char *ptr;
464 
465 	switch (remcomInBuffer[0]) {
466 	case 'c':
467 	case 's':
468 		/* try to read optional parameter, pc unchanged if no parm */
469 		ptr = &remcomInBuffer[1];
470 		if (kgdb_hex2long(&ptr, &addr))
471 			linux_regs->ip = addr;
472 	case 'D':
473 	case 'k':
474 		/* clear the trace bit */
475 		linux_regs->flags &= ~X86_EFLAGS_TF;
476 		atomic_set(&kgdb_cpu_doing_single_step, -1);
477 
478 		/* set the trace bit if we're stepping */
479 		if (remcomInBuffer[0] == 's') {
480 			linux_regs->flags |= X86_EFLAGS_TF;
481 			atomic_set(&kgdb_cpu_doing_single_step,
482 				   raw_smp_processor_id());
483 		}
484 
485 		return 0;
486 	}
487 
488 	/* this means that we do not want to exit from the handler: */
489 	return -1;
490 }
491 
492 static inline int
493 single_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 
512 static int was_in_debug_nmi[NR_CPUS];
513 
514 static 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_NMIUNKNOWN:
530 		if (was_in_debug_nmi[raw_smp_processor_id()]) {
531 			was_in_debug_nmi[raw_smp_processor_id()] = 0;
532 			return NOTIFY_STOP;
533 		}
534 		return NOTIFY_DONE;
535 
536 	case DIE_DEBUG:
537 		if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
538 			if (user_mode(regs))
539 				return single_step_cont(regs, args);
540 			break;
541 		} else if (test_thread_flag(TIF_SINGLESTEP))
542 			/* This means a user thread is single stepping
543 			 * a system call which should be ignored
544 			 */
545 			return NOTIFY_DONE;
546 		/* fall through */
547 	default:
548 		if (user_mode(regs))
549 			return NOTIFY_DONE;
550 	}
551 
552 	if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
553 		return NOTIFY_DONE;
554 
555 	/* Must touch watchdog before return to normal operation */
556 	touch_nmi_watchdog();
557 	return NOTIFY_STOP;
558 }
559 
560 int kgdb_ll_trap(int cmd, const char *str,
561 		 struct pt_regs *regs, long err, int trap, int sig)
562 {
563 	struct die_args args = {
564 		.regs	= regs,
565 		.str	= str,
566 		.err	= err,
567 		.trapnr	= trap,
568 		.signr	= sig,
569 
570 	};
571 
572 	if (!kgdb_io_module_registered)
573 		return NOTIFY_DONE;
574 
575 	return __kgdb_notify(&args, cmd);
576 }
577 
578 static int
579 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
580 {
581 	unsigned long flags;
582 	int ret;
583 
584 	local_irq_save(flags);
585 	ret = __kgdb_notify(ptr, cmd);
586 	local_irq_restore(flags);
587 
588 	return ret;
589 }
590 
591 static struct notifier_block kgdb_notifier = {
592 	.notifier_call	= kgdb_notify,
593 
594 	/*
595 	 * Lowest-prio notifier priority, we want to be notified last:
596 	 */
597 	.priority	= NMI_LOCAL_LOW_PRIOR,
598 };
599 
600 /**
601  *	kgdb_arch_init - Perform any architecture specific initalization.
602  *
603  *	This function will handle the initalization of any architecture
604  *	specific callbacks.
605  */
606 int kgdb_arch_init(void)
607 {
608 	return register_die_notifier(&kgdb_notifier);
609 }
610 
611 static void kgdb_hw_overflow_handler(struct perf_event *event,
612 		struct perf_sample_data *data, struct pt_regs *regs)
613 {
614 	struct task_struct *tsk = current;
615 	int i;
616 
617 	for (i = 0; i < 4; i++)
618 		if (breakinfo[i].enabled)
619 			tsk->thread.debugreg6 |= (DR_TRAP0 << i);
620 }
621 
622 void kgdb_arch_late(void)
623 {
624 	int i, cpu;
625 	struct perf_event_attr attr;
626 	struct perf_event **pevent;
627 
628 	/*
629 	 * Pre-allocate the hw breakpoint structions in the non-atomic
630 	 * portion of kgdb because this operation requires mutexs to
631 	 * complete.
632 	 */
633 	hw_breakpoint_init(&attr);
634 	attr.bp_addr = (unsigned long)kgdb_arch_init;
635 	attr.bp_len = HW_BREAKPOINT_LEN_1;
636 	attr.bp_type = HW_BREAKPOINT_W;
637 	attr.disabled = 1;
638 	for (i = 0; i < HBP_NUM; i++) {
639 		if (breakinfo[i].pev)
640 			continue;
641 		breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL, NULL);
642 		if (IS_ERR((void * __force)breakinfo[i].pev)) {
643 			printk(KERN_ERR "kgdb: Could not allocate hw"
644 			       "breakpoints\nDisabling the kernel debugger\n");
645 			breakinfo[i].pev = NULL;
646 			kgdb_arch_exit();
647 			return;
648 		}
649 		for_each_online_cpu(cpu) {
650 			pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
651 			pevent[0]->hw.sample_period = 1;
652 			pevent[0]->overflow_handler = kgdb_hw_overflow_handler;
653 			if (pevent[0]->destroy != NULL) {
654 				pevent[0]->destroy = NULL;
655 				release_bp_slot(*pevent);
656 			}
657 		}
658 	}
659 }
660 
661 /**
662  *	kgdb_arch_exit - Perform any architecture specific uninitalization.
663  *
664  *	This function will handle the uninitalization of any architecture
665  *	specific callbacks, for dynamic registration and unregistration.
666  */
667 void kgdb_arch_exit(void)
668 {
669 	int i;
670 	for (i = 0; i < 4; i++) {
671 		if (breakinfo[i].pev) {
672 			unregister_wide_hw_breakpoint(breakinfo[i].pev);
673 			breakinfo[i].pev = NULL;
674 		}
675 	}
676 	unregister_die_notifier(&kgdb_notifier);
677 }
678 
679 /**
680  *
681  *	kgdb_skipexception - Bail out of KGDB when we've been triggered.
682  *	@exception: Exception vector number
683  *	@regs: Current &struct pt_regs.
684  *
685  *	On some architectures we need to skip a breakpoint exception when
686  *	it occurs after a breakpoint has been removed.
687  *
688  * Skip an int3 exception when it occurs after a breakpoint has been
689  * removed. Backtrack eip by 1 since the int3 would have caused it to
690  * increment by 1.
691  */
692 int kgdb_skipexception(int exception, struct pt_regs *regs)
693 {
694 	if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
695 		regs->ip -= 1;
696 		return 1;
697 	}
698 	return 0;
699 }
700 
701 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
702 {
703 	if (exception == 3)
704 		return instruction_pointer(regs) - 1;
705 	return instruction_pointer(regs);
706 }
707 
708 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
709 {
710 	regs->ip = ip;
711 }
712 
713 struct kgdb_arch arch_kgdb_ops = {
714 	/* Breakpoint instruction: */
715 	.gdb_bpt_instr		= { 0xcc },
716 	.flags			= KGDB_HW_BREAKPOINT,
717 	.set_hw_breakpoint	= kgdb_set_hw_break,
718 	.remove_hw_breakpoint	= kgdb_remove_hw_break,
719 	.disable_hw_break	= kgdb_disable_hw_debug,
720 	.remove_all_hw_break	= kgdb_remove_all_hw_break,
721 	.correct_hw_break	= kgdb_correct_hw_break,
722 };
723