From cd6ef7eebf171bfcba7dc2df719c2a4958775040 Mon Sep 17 00:00:00 2001
From: Michael Neuling <mikey@neuling.org>
Date: Thu, 17 May 2018 15:37:14 +1000
Subject: [PATCH] powerpc/ptrace: Fix enforcement of DAWR constraints
Git-commit: cd6ef7eebf171bfcba7dc2df719c2a4958775040
Patch-mainline: v4.18-rc1
References: bsc#1099918

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")
Cc: stable@vger.kernel.org # v3.9+
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Coly Li <colyli@suse.de>

---
 arch/powerpc/kernel/hw_breakpoint.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index 4c1012b80d3b..80547dad37da 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -178,8 +178,8 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
 	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 >
-- 
2.17.1