[PATCH 4.11 33/58] powerpc/64s: Handle data breakpoints in Radix mode

Greg Kroah-Hartman
2017-06-27T14:25:29Z

From: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>

commit d89ba5353f301971dd7d2f9fdf25c4432728f38e upstream.

On Power9, 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(), which is not called when in Radix mode.

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

Move the check to handle_page_fault() so as to catch data breakpoints
in both Hash and Radix MMU modes.

We have to change the check in do_hash_page() against 0xa410 to use
0xa450, so as to include the value of (DSISR_DABRMATCH << 16).

There are two sites that call handle_page_fault() when in Radix, both
already pass DSISR in r4.

Fixes: caca285e5ab4 ("powerpc/mm/radix: Use STD_MMU_64 to properly isolate hash related code")
Reported-by: Shriya R. Kulkarni <shriykul@in.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
[mpe: Fix the fall-through case on hash, we need to reload DSISR]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/powerpc/kernel/exceptions-64s.S | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1425,10 +1425,8 @@ 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@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@h /* (i.e. an irq when soft-disabled) */
@@ -1452,11 +1450,16 @@ do_hash_page:

/* Error */
blt- 13f
+
+ /* Reload DSISR into r4 for the DABR check below */
+ ld r4,_DSISR(r1)
#endif /* CONFIG_PPC_STD_MMU_64 */

/* Here we have a page fault that hash_page can't handle. */
handle_page_fault:
-11: ld r4,_DAR(r1)
+11: andis. r0,r4,DSISR_DABRMATCH@h
+ bne- handle_dabr_fault
+ ld r4,_DAR(r1)
ld r5,_DSISR(r1)
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_page_fault