Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel...
[linux-2.6.git] / arch / x86 / kernel / kgdb.c
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
52 /**
53  *      pt_regs_to_gdb_regs - Convert ptrace regs to GDB regs
54  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
55  *      @regs: The &struct pt_regs of the current process.
56  *
57  *      Convert the pt_regs in @regs into the format for registers that
58  *      GDB expects, stored in @gdb_regs.
59  */
60 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
61 {
62 #ifndef CONFIG_X86_32
63         u32 *gdb_regs32 = (u32 *)gdb_regs;
64 #endif
65         gdb_regs[GDB_AX]        = regs->ax;
66         gdb_regs[GDB_BX]        = regs->bx;
67         gdb_regs[GDB_CX]        = regs->cx;
68         gdb_regs[GDB_DX]        = regs->dx;
69         gdb_regs[GDB_SI]        = regs->si;
70         gdb_regs[GDB_DI]        = regs->di;
71         gdb_regs[GDB_BP]        = regs->bp;
72         gdb_regs[GDB_PC]        = regs->ip;
73 #ifdef CONFIG_X86_32
74         gdb_regs[GDB_PS]        = regs->flags;
75         gdb_regs[GDB_DS]        = regs->ds;
76         gdb_regs[GDB_ES]        = regs->es;
77         gdb_regs[GDB_CS]        = regs->cs;
78         gdb_regs[GDB_FS]        = 0xFFFF;
79         gdb_regs[GDB_GS]        = 0xFFFF;
80         if (user_mode_vm(regs)) {
81                 gdb_regs[GDB_SS] = regs->ss;
82                 gdb_regs[GDB_SP] = regs->sp;
83         } else {
84                 gdb_regs[GDB_SS] = __KERNEL_DS;
85                 gdb_regs[GDB_SP] = kernel_stack_pointer(regs);
86         }
87 #else
88         gdb_regs[GDB_R8]        = regs->r8;
89         gdb_regs[GDB_R9]        = regs->r9;
90         gdb_regs[GDB_R10]       = regs->r10;
91         gdb_regs[GDB_R11]       = regs->r11;
92         gdb_regs[GDB_R12]       = regs->r12;
93         gdb_regs[GDB_R13]       = regs->r13;
94         gdb_regs[GDB_R14]       = regs->r14;
95         gdb_regs[GDB_R15]       = regs->r15;
96         gdb_regs32[GDB_PS]      = regs->flags;
97         gdb_regs32[GDB_CS]      = regs->cs;
98         gdb_regs32[GDB_SS]      = regs->ss;
99         gdb_regs[GDB_SP]        = kernel_stack_pointer(regs);
100 #endif
101 }
102
103 /**
104  *      sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
105  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
106  *      @p: The &struct task_struct of the desired process.
107  *
108  *      Convert the register values of the sleeping process in @p to
109  *      the format that GDB expects.
110  *      This function is called when kgdb does not have access to the
111  *      &struct pt_regs and therefore it should fill the gdb registers
112  *      @gdb_regs with what has been saved in &struct thread_struct
113  *      thread field during switch_to.
114  */
115 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
116 {
117 #ifndef CONFIG_X86_32
118         u32 *gdb_regs32 = (u32 *)gdb_regs;
119 #endif
120         gdb_regs[GDB_AX]        = 0;
121         gdb_regs[GDB_BX]        = 0;
122         gdb_regs[GDB_CX]        = 0;
123         gdb_regs[GDB_DX]        = 0;
124         gdb_regs[GDB_SI]        = 0;
125         gdb_regs[GDB_DI]        = 0;
126         gdb_regs[GDB_BP]        = *(unsigned long *)p->thread.sp;
127 #ifdef CONFIG_X86_32
128         gdb_regs[GDB_DS]        = __KERNEL_DS;
129         gdb_regs[GDB_ES]        = __KERNEL_DS;
130         gdb_regs[GDB_PS]        = 0;
131         gdb_regs[GDB_CS]        = __KERNEL_CS;
132         gdb_regs[GDB_PC]        = p->thread.ip;
133         gdb_regs[GDB_SS]        = __KERNEL_DS;
134         gdb_regs[GDB_FS]        = 0xFFFF;
135         gdb_regs[GDB_GS]        = 0xFFFF;
136 #else
137         gdb_regs32[GDB_PS]      = *(unsigned long *)(p->thread.sp + 8);
138         gdb_regs32[GDB_CS]      = __KERNEL_CS;
139         gdb_regs32[GDB_SS]      = __KERNEL_DS;
140         gdb_regs[GDB_PC]        = 0;
141         gdb_regs[GDB_R8]        = 0;
142         gdb_regs[GDB_R9]        = 0;
143         gdb_regs[GDB_R10]       = 0;
144         gdb_regs[GDB_R11]       = 0;
145         gdb_regs[GDB_R12]       = 0;
146         gdb_regs[GDB_R13]       = 0;
147         gdb_regs[GDB_R14]       = 0;
148         gdb_regs[GDB_R15]       = 0;
149 #endif
150         gdb_regs[GDB_SP]        = p->thread.sp;
151 }
152
153 /**
154  *      gdb_regs_to_pt_regs - Convert GDB regs to ptrace regs.
155  *      @gdb_regs: A pointer to hold the registers we've received from GDB.
156  *      @regs: A pointer to a &struct pt_regs to hold these values in.
157  *
158  *      Convert the GDB regs in @gdb_regs into the pt_regs, and store them
159  *      in @regs.
160  */
161 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
162 {
163 #ifndef CONFIG_X86_32
164         u32 *gdb_regs32 = (u32 *)gdb_regs;
165 #endif
166         regs->ax                = gdb_regs[GDB_AX];
167         regs->bx                = gdb_regs[GDB_BX];
168         regs->cx                = gdb_regs[GDB_CX];
169         regs->dx                = gdb_regs[GDB_DX];
170         regs->si                = gdb_regs[GDB_SI];
171         regs->di                = gdb_regs[GDB_DI];
172         regs->bp                = gdb_regs[GDB_BP];
173         regs->ip                = gdb_regs[GDB_PC];
174 #ifdef CONFIG_X86_32
175         regs->flags             = gdb_regs[GDB_PS];
176         regs->ds                = gdb_regs[GDB_DS];
177         regs->es                = gdb_regs[GDB_ES];
178         regs->cs                = gdb_regs[GDB_CS];
179 #else
180         regs->r8                = gdb_regs[GDB_R8];
181         regs->r9                = gdb_regs[GDB_R9];
182         regs->r10               = gdb_regs[GDB_R10];
183         regs->r11               = gdb_regs[GDB_R11];
184         regs->r12               = gdb_regs[GDB_R12];
185         regs->r13               = gdb_regs[GDB_R13];
186         regs->r14               = gdb_regs[GDB_R14];
187         regs->r15               = gdb_regs[GDB_R15];
188         regs->flags             = gdb_regs32[GDB_PS];
189         regs->cs                = gdb_regs32[GDB_CS];
190         regs->ss                = gdb_regs32[GDB_SS];
191 #endif
192 }
193
194 static struct hw_breakpoint {
195         unsigned                enabled;
196         unsigned long           addr;
197         int                     len;
198         int                     type;
199         struct perf_event       **pev;
200 } breakinfo[4];
201
202 static unsigned long early_dr7;
203
204 static void kgdb_correct_hw_break(void)
205 {
206         int breakno;
207
208         for (breakno = 0; breakno < 4; breakno++) {
209                 struct perf_event *bp;
210                 struct arch_hw_breakpoint *info;
211                 int val;
212                 int cpu = raw_smp_processor_id();
213                 if (!breakinfo[breakno].enabled)
214                         continue;
215                 if (dbg_is_early) {
216                         set_debugreg(breakinfo[breakno].addr, breakno);
217                         early_dr7 |= encode_dr7(breakno,
218                                                 breakinfo[breakno].len,
219                                                 breakinfo[breakno].type);
220                         set_debugreg(early_dr7, 7);
221                         continue;
222                 }
223                 bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
224                 info = counter_arch_bp(bp);
225                 if (bp->attr.disabled != 1)
226                         continue;
227                 bp->attr.bp_addr = breakinfo[breakno].addr;
228                 bp->attr.bp_len = breakinfo[breakno].len;
229                 bp->attr.bp_type = breakinfo[breakno].type;
230                 info->address = breakinfo[breakno].addr;
231                 info->len = breakinfo[breakno].len;
232                 info->type = breakinfo[breakno].type;
233                 val = arch_install_hw_breakpoint(bp);
234                 if (!val)
235                         bp->attr.disabled = 0;
236         }
237         if (!dbg_is_early)
238                 hw_breakpoint_restore();
239 }
240
241 static int hw_break_reserve_slot(int breakno)
242 {
243         int cpu;
244         int cnt = 0;
245         struct perf_event **pevent;
246
247         if (dbg_is_early)
248                 return 0;
249
250         for_each_online_cpu(cpu) {
251                 cnt++;
252                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
253                 if (dbg_reserve_bp_slot(*pevent))
254                         goto fail;
255         }
256
257         return 0;
258
259 fail:
260         for_each_online_cpu(cpu) {
261                 cnt--;
262                 if (!cnt)
263                         break;
264                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
265                 dbg_release_bp_slot(*pevent);
266         }
267         return -1;
268 }
269
270 static int hw_break_release_slot(int breakno)
271 {
272         struct perf_event **pevent;
273         int cpu;
274
275         if (dbg_is_early)
276                 return 0;
277
278         for_each_online_cpu(cpu) {
279                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
280                 if (dbg_release_bp_slot(*pevent))
281                         /*
282                          * The debugger is responisble for handing the retry on
283                          * remove failure.
284                          */
285                         return -1;
286         }
287         return 0;
288 }
289
290 static int
291 kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
292 {
293         int i;
294
295         for (i = 0; i < 4; i++)
296                 if (breakinfo[i].addr == addr && breakinfo[i].enabled)
297                         break;
298         if (i == 4)
299                 return -1;
300
301         if (hw_break_release_slot(i)) {
302                 printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
303                 return -1;
304         }
305         breakinfo[i].enabled = 0;
306
307         return 0;
308 }
309
310 static void kgdb_remove_all_hw_break(void)
311 {
312         int i;
313         int cpu = raw_smp_processor_id();
314         struct perf_event *bp;
315
316         for (i = 0; i < 4; i++) {
317                 if (!breakinfo[i].enabled)
318                         continue;
319                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
320                 if (bp->attr.disabled == 1)
321                         continue;
322                 if (dbg_is_early)
323                         early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
324                                                  breakinfo[i].type);
325                 else
326                         arch_uninstall_hw_breakpoint(bp);
327                 bp->attr.disabled = 1;
328         }
329 }
330
331 static int
332 kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
333 {
334         int i;
335
336         for (i = 0; i < 4; i++)
337                 if (!breakinfo[i].enabled)
338                         break;
339         if (i == 4)
340                 return -1;
341
342         switch (bptype) {
343         case BP_HARDWARE_BREAKPOINT:
344                 len = 1;
345                 breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
346                 break;
347         case BP_WRITE_WATCHPOINT:
348                 breakinfo[i].type = X86_BREAKPOINT_WRITE;
349                 break;
350         case BP_ACCESS_WATCHPOINT:
351                 breakinfo[i].type = X86_BREAKPOINT_RW;
352                 break;
353         default:
354                 return -1;
355         }
356         switch (len) {
357         case 1:
358                 breakinfo[i].len = X86_BREAKPOINT_LEN_1;
359                 break;
360         case 2:
361                 breakinfo[i].len = X86_BREAKPOINT_LEN_2;
362                 break;
363         case 4:
364                 breakinfo[i].len = X86_BREAKPOINT_LEN_4;
365                 break;
366 #ifdef CONFIG_X86_64
367         case 8:
368                 breakinfo[i].len = X86_BREAKPOINT_LEN_8;
369                 break;
370 #endif
371         default:
372                 return -1;
373         }
374         breakinfo[i].addr = addr;
375         if (hw_break_reserve_slot(i)) {
376                 breakinfo[i].addr = 0;
377                 return -1;
378         }
379         breakinfo[i].enabled = 1;
380
381         return 0;
382 }
383
384 /**
385  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
386  *      @regs: Current &struct pt_regs.
387  *
388  *      This function will be called if the particular architecture must
389  *      disable hardware debugging while it is processing gdb packets or
390  *      handling exception.
391  */
392 void kgdb_disable_hw_debug(struct pt_regs *regs)
393 {
394         int i;
395         int cpu = raw_smp_processor_id();
396         struct perf_event *bp;
397
398         /* Disable hardware debugging while we are in kgdb: */
399         set_debugreg(0UL, 7);
400         for (i = 0; i < 4; i++) {
401                 if (!breakinfo[i].enabled)
402                         continue;
403                 if (dbg_is_early) {
404                         early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
405                                                  breakinfo[i].type);
406                         continue;
407                 }
408                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
409                 if (bp->attr.disabled == 1)
410                         continue;
411                 arch_uninstall_hw_breakpoint(bp);
412                 bp->attr.disabled = 1;
413         }
414 }
415
416 #ifdef CONFIG_SMP
417 /**
418  *      kgdb_roundup_cpus - Get other CPUs into a holding pattern
419  *      @flags: Current IRQ state
420  *
421  *      On SMP systems, we need to get the attention of the other CPUs
422  *      and get them be in a known state.  This should do what is needed
423  *      to get the other CPUs to call kgdb_wait(). Note that on some arches,
424  *      the NMI approach is not used for rounding up all the CPUs. For example,
425  *      in case of MIPS, smp_call_function() is used to roundup CPUs. In
426  *      this case, we have to make sure that interrupts are enabled before
427  *      calling smp_call_function(). The argument to this function is
428  *      the flags that will be used when restoring the interrupts. There is
429  *      local_irq_save() call before kgdb_roundup_cpus().
430  *
431  *      On non-SMP systems, this is not called.
432  */
433 void kgdb_roundup_cpus(unsigned long flags)
434 {
435         apic->send_IPI_allbutself(APIC_DM_NMI);
436 }
437 #endif
438
439 /**
440  *      kgdb_arch_handle_exception - Handle architecture specific GDB packets.
441  *      @vector: The error vector of the exception that happened.
442  *      @signo: The signal number of the exception that happened.
443  *      @err_code: The error code of the exception that happened.
444  *      @remcom_in_buffer: The buffer of the packet we have read.
445  *      @remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
446  *      @regs: The &struct pt_regs of the current process.
447  *
448  *      This function MUST handle the 'c' and 's' command packets,
449  *      as well packets to set / remove a hardware breakpoint, if used.
450  *      If there are additional packets which the hardware needs to handle,
451  *      they are handled here.  The code should return -1 if it wants to
452  *      process more packets, and a %0 or %1 if it wants to exit from the
453  *      kgdb callback.
454  */
455 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
456                                char *remcomInBuffer, char *remcomOutBuffer,
457                                struct pt_regs *linux_regs)
458 {
459         unsigned long addr;
460         char *ptr;
461         int newPC;
462
463         switch (remcomInBuffer[0]) {
464         case 'c':
465         case 's':
466                 /* try to read optional parameter, pc unchanged if no parm */
467                 ptr = &remcomInBuffer[1];
468                 if (kgdb_hex2long(&ptr, &addr))
469                         linux_regs->ip = addr;
470         case 'D':
471         case 'k':
472                 newPC = linux_regs->ip;
473
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                 kgdb_correct_hw_break();
486
487                 return 0;
488         }
489
490         /* this means that we do not want to exit from the handler: */
491         return -1;
492 }
493
494 static inline int
495 single_step_cont(struct pt_regs *regs, struct die_args *args)
496 {
497         /*
498          * Single step exception from kernel space to user space so
499          * eat the exception and continue the process:
500          */
501         printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
502                         "resuming...\n");
503         kgdb_arch_handle_exception(args->trapnr, args->signr,
504                                    args->err, "c", "", regs);
505         /*
506          * Reset the BS bit in dr6 (pointed by args->err) to
507          * denote completion of processing
508          */
509         (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
510
511         return NOTIFY_STOP;
512 }
513
514 static int was_in_debug_nmi[NR_CPUS];
515
516 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
517 {
518         struct pt_regs *regs = args->regs;
519
520         switch (cmd) {
521         case DIE_NMI:
522                 if (atomic_read(&kgdb_active) != -1) {
523                         /* KGDB CPU roundup */
524                         kgdb_nmicallback(raw_smp_processor_id(), regs);
525                         was_in_debug_nmi[raw_smp_processor_id()] = 1;
526                         touch_nmi_watchdog();
527                         return NOTIFY_STOP;
528                 }
529                 return NOTIFY_DONE;
530
531         case DIE_NMI_IPI:
532                 /* Just ignore, we will handle the roundup on DIE_NMI. */
533                 return NOTIFY_DONE;
534
535         case DIE_NMIUNKNOWN:
536                 if (was_in_debug_nmi[raw_smp_processor_id()]) {
537                         was_in_debug_nmi[raw_smp_processor_id()] = 0;
538                         return NOTIFY_STOP;
539                 }
540                 return NOTIFY_DONE;
541
542         case DIE_NMIWATCHDOG:
543                 if (atomic_read(&kgdb_active) != -1) {
544                         /* KGDB CPU roundup: */
545                         kgdb_nmicallback(raw_smp_processor_id(), regs);
546                         return NOTIFY_STOP;
547                 }
548                 /* Enter debugger: */
549                 break;
550
551         case DIE_DEBUG:
552                 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
553                         if (user_mode(regs))
554                                 return single_step_cont(regs, args);
555                         break;
556                 } else if (test_thread_flag(TIF_SINGLESTEP))
557                         /* This means a user thread is single stepping
558                          * a system call which should be ignored
559                          */
560                         return NOTIFY_DONE;
561                 /* fall through */
562         default:
563                 if (user_mode(regs))
564                         return NOTIFY_DONE;
565         }
566
567         if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
568                 return NOTIFY_DONE;
569
570         /* Must touch watchdog before return to normal operation */
571         touch_nmi_watchdog();
572         return NOTIFY_STOP;
573 }
574
575 int kgdb_ll_trap(int cmd, const char *str,
576                  struct pt_regs *regs, long err, int trap, int sig)
577 {
578         struct die_args args = {
579                 .regs   = regs,
580                 .str    = str,
581                 .err    = err,
582                 .trapnr = trap,
583                 .signr  = sig,
584
585         };
586
587         if (!kgdb_io_module_registered)
588                 return NOTIFY_DONE;
589
590         return __kgdb_notify(&args, cmd);
591 }
592
593 static int
594 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
595 {
596         unsigned long flags;
597         int ret;
598
599         local_irq_save(flags);
600         ret = __kgdb_notify(ptr, cmd);
601         local_irq_restore(flags);
602
603         return ret;
604 }
605
606 static struct notifier_block kgdb_notifier = {
607         .notifier_call  = kgdb_notify,
608
609         /*
610          * Lowest-prio notifier priority, we want to be notified last:
611          */
612         .priority       = -INT_MAX,
613 };
614
615 /**
616  *      kgdb_arch_init - Perform any architecture specific initalization.
617  *
618  *      This function will handle the initalization of any architecture
619  *      specific callbacks.
620  */
621 int kgdb_arch_init(void)
622 {
623         return register_die_notifier(&kgdb_notifier);
624 }
625
626 static void kgdb_hw_overflow_handler(struct perf_event *event, int nmi,
627                 struct perf_sample_data *data, struct pt_regs *regs)
628 {
629         kgdb_ll_trap(DIE_DEBUG, "debug", regs, 0, 0, SIGTRAP);
630 }
631
632 void kgdb_arch_late(void)
633 {
634         int i, cpu;
635         struct perf_event_attr attr;
636         struct perf_event **pevent;
637
638         /*
639          * Pre-allocate the hw breakpoint structions in the non-atomic
640          * portion of kgdb because this operation requires mutexs to
641          * complete.
642          */
643         hw_breakpoint_init(&attr);
644         attr.bp_addr = (unsigned long)kgdb_arch_init;
645         attr.bp_len = HW_BREAKPOINT_LEN_1;
646         attr.bp_type = HW_BREAKPOINT_W;
647         attr.disabled = 1;
648         for (i = 0; i < 4; i++) {
649                 if (breakinfo[i].pev)
650                         continue;
651                 breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL);
652                 if (IS_ERR(breakinfo[i].pev)) {
653                         printk(KERN_ERR "kgdb: Could not allocate hw"
654                                "breakpoints\nDisabling the kernel debugger\n");
655                         breakinfo[i].pev = NULL;
656                         kgdb_arch_exit();
657                         return;
658                 }
659                 for_each_online_cpu(cpu) {
660                         pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
661                         pevent[0]->hw.sample_period = 1;
662                         pevent[0]->overflow_handler = kgdb_hw_overflow_handler;
663                         if (pevent[0]->destroy != NULL) {
664                                 pevent[0]->destroy = NULL;
665                                 release_bp_slot(*pevent);
666                         }
667                 }
668         }
669 }
670
671 /**
672  *      kgdb_arch_exit - Perform any architecture specific uninitalization.
673  *
674  *      This function will handle the uninitalization of any architecture
675  *      specific callbacks, for dynamic registration and unregistration.
676  */
677 void kgdb_arch_exit(void)
678 {
679         int i;
680         for (i = 0; i < 4; i++) {
681                 if (breakinfo[i].pev) {
682                         unregister_wide_hw_breakpoint(breakinfo[i].pev);
683                         breakinfo[i].pev = NULL;
684                 }
685         }
686         unregister_die_notifier(&kgdb_notifier);
687 }
688
689 /**
690  *
691  *      kgdb_skipexception - Bail out of KGDB when we've been triggered.
692  *      @exception: Exception vector number
693  *      @regs: Current &struct pt_regs.
694  *
695  *      On some architectures we need to skip a breakpoint exception when
696  *      it occurs after a breakpoint has been removed.
697  *
698  * Skip an int3 exception when it occurs after a breakpoint has been
699  * removed. Backtrack eip by 1 since the int3 would have caused it to
700  * increment by 1.
701  */
702 int kgdb_skipexception(int exception, struct pt_regs *regs)
703 {
704         if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
705                 regs->ip -= 1;
706                 return 1;
707         }
708         return 0;
709 }
710
711 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
712 {
713         if (exception == 3)
714                 return instruction_pointer(regs) - 1;
715         return instruction_pointer(regs);
716 }
717
718 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
719 {
720         regs->ip = ip;
721 }
722
723 struct kgdb_arch arch_kgdb_ops = {
724         /* Breakpoint instruction: */
725         .gdb_bpt_instr          = { 0xcc },
726         .flags                  = KGDB_HW_BREAKPOINT,
727         .set_hw_breakpoint      = kgdb_set_hw_break,
728         .remove_hw_breakpoint   = kgdb_remove_hw_break,
729         .remove_all_hw_break    = kgdb_remove_all_hw_break,
730         .correct_hw_break       = kgdb_correct_hw_break,
731 };