powerpc/64s: Handle data breakpoints in Radix mode

rnav · mpe · commit d89ba5353f30 · 2017-06-16T19:49:43.000+10:00
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: caca285 ("powerpc/mm/radix: Use STD_MMU_64 to properly isolate hash related code") Cc: stable@vger.kernel.org # v4.7+ 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>
diff --git 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@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) */
@@ -1438,11 +1436,16 @@ 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
