[PATCH 3.16 069/366] powerpc/ptrace: Fix enforcement of DAWR constraints

[Ben Hutchings]

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Neuling <mikey@xxxxxxxxxxx>

commit cd6ef7eebf171bfcba7dc2df719c2a4958775040 upstream.

Back when we first introduced the DAWR, in commit 4ae7ebe9522a
("powerpc: Change hardware breakpoint to allow longer ranges"), we
screwed up the constraint making it a 1024 byte boundary rather than a
512. This makes the check overly permissive. Fortunately GDB is the
only real user and it always did they right thing, so we never
noticed.

This fixes the constraint to 512 bytes.

Fixes: 4ae7ebe9522a ("powerpc: Change hardware breakpoint to allow longer ranges")
Signed-off-by: Michael Neuling <mikey@xxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/powerpc/kernel/hw_breakpoint.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -174,8 +174,8 @@ int arch_validate_hwbkpt_settings(struct
 	if (cpu_has_feature(CPU_FTR_DAWR)) {
 		length_max = 512 ; /* 64 doublewords */
 		/* DAWR region can't cross 512 boundary */
-		if ((bp->attr.bp_addr >> 10) != 
-		    ((bp->attr.bp_addr + bp->attr.bp_len - 1) >> 10))
+		if ((bp->attr.bp_addr >> 9) !=
+		    ((bp->attr.bp_addr + bp->attr.bp_len - 1) >> 9))
 			return -EINVAL;
 	}
 	if (info->len >