[RFC Patch 1/2] PPC64-HWBKPT: Disable interrupts for data breakpoint exceptions

["K.Prasad" <prasad@linux.vnet.ibm.com>]

Data address breakpoint exceptions are currently handled along with page-faults
which require interrupts to remain in enabled state. Since exception handling
for data breakpoints aren't pre-empt safe, we handle them separately.

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/exceptions-64s.S |   12 ++++++++++++
 arch/powerpc/mm/fault.c              |    2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

Index: linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/exceptions-64s.S
+++ linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S
@@ -735,6 +735,9 @@ _STATIC(do_hash_page)
 	std	r3,_DAR(r1)
 	std	r4,_DSISR(r1)
 
+	andis.  r0,r4,0x0040		/* Data Address Breakpoint match? */
+	bne-    handle_dabr_fault
+
 	andis.	r0,r4,0xa450		/* weird error? */
 	bne-	handle_page_fault	/* if not, try to insert a HPTE */
 BEGIN_FTR_SECTION
@@ -823,6 +826,15 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISER
 	bl	.raw_local_irq_restore
 	b	11f
 
+/* We have a data breakpoint exception - handle it */
+handle_dabr_fault:
+	/* Populate the pt_regs structure */
+	ld      r4,_DAR(r1)
+	ld      r5,_DSISR(r1)
+	addi    r3,r1,STACK_FRAME_OVERHEAD
+	bl      .do_dabr
+	b       .ret_from_except_lite
+
 /* Here we have a page fault that hash_page can't handle. */
 handle_page_fault:
 	ENABLE_INTS
Index: linux-2.6.ppc64_test/arch/powerpc/mm/fault.c
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/mm/fault.c
+++ linux-2.6.ppc64_test/arch/powerpc/mm/fault.c
@@ -151,7 +151,7 @@ int __kprobes do_page_fault(struct pt_re
 	if (!user_mode(regs) && (address >= TASK_SIZE))
 		return SIGSEGV;
 
-#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
+#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || defined(CONFIG_PPC64))
   	if (error_code & DSISR_DABRMATCH) {
 		/* DABR match */
 		do_dabr(regs, address, error_code);