[PATCH] powerpc64/hw_breakpoints: Handle data breakpoints in radix mode

[Naveen N. Rao]

On P9, trying to use data breakpoints throws the splat shown below (*).
This is because the check for a data breakpoint in DSISR is in
do_hash_page(). Move this check to handle_page_fault() so as to catch
data breakpoints in both hash and radix MMU modes.

While at it, also remove the label '11' that was made redundant by
commit a546498f3bf9aa ("powerpc: Call do_page_fault() with interrupts
off")

(*)
    Unable to handle kernel paging request for data at address 0xc000000000e19218
    Faulting instruction address: 0xc0000000001155e8
    cpu 0x0: Vector: 300 (Data Access) at [c0000000ef1e7b20]
    pc: c0000000001155e8: find_pid_ns+0x48/0xe0
    lr: c000000000116ac4: find_task_by_vpid+0x44/0x90
    sp: c0000000ef1e7da0
    msr: 9000000000009033
    dar: c000000000e19218
    dsisr: 400000
    current = 0xc0000000f1f59700
    paca    = 0xc00000000fd40000 softe: 0 irq_happened: 0x01
    pid   = 1192, comm = sh
    Linux version 4.12.0-rc3-nnr (root at ea605ec2993c) (gcc version 5.4.0 20160609 (Ubuntu/IBM 5.4.0-6ubuntu1~16.04.1) ) #74 SMP Tue Jun 13 16:52:49 UTC 2017
    enter ? for help
    [c0000000ef1e7dc0] c000000000116ac4 find_task_by_vpid+0x44/0x90
    [c0000000ef1e7de0] c000000000108800 SyS_setpgid+0x80/0x220
    [c0000000ef1e7e30] c00000000000ba6c system_call+0x38/0xfc
    --- Exception: c01 (System Call) at 00007fff94480890
    SP (7fffd91e7260) is in userspace

Fixes: caca285e5ab4a ("powerpc/mm/radix: Use STD_MMU_64 to properly
isolate hash related code")
Reported-by: Shriya R. Kulkarni <shriykul at in.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
---
 arch/powerpc/kernel/exceptions-64s.S | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index ae418b85c17c..17ee701b8336 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1411,10 +1411,8 @@ USE_TEXT_SECTION()
 	.balign	IFETCH_ALIGN_BYTES
 do_hash_page:
 #ifdef CONFIG_PPC_STD_MMU_64
-	andis.	r0,r4,0xa410		/* weird error? */
+	andis.	r0,r4,0xa450		/* weird error? */
 	bne-	handle_page_fault	/* if not, try to insert a HPTE */
-	andis.  r0,r4,DSISR_DABRMATCH at h
-	bne-    handle_dabr_fault
 	CURRENT_THREAD_INFO(r11, r1)
 	lwz	r0,TI_PREEMPT(r11)	/* If we're in an "NMI" */
 	andis.	r0,r0,NMI_MASK at h	/* (i.e. an irq when soft-disabled) */
@@ -1442,7 +1440,9 @@ do_hash_page:
 
 /* Here we have a page fault that hash_page can't handle. */
 handle_page_fault:
-11:	ld	r4,_DAR(r1)
+	andis.  r0,r4,DSISR_DABRMATCH at h
+	bne-    handle_dabr_fault
+	ld	r4,_DAR(r1)
 	ld	r5,_DSISR(r1)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	do_page_fault
-- 
2.12.2