powerpc/memcpy: Fix stack corruption for smaller sizes

For sizes lesser than 128 bytes, the code branches out early without saving
the stack frame, which when restored later drops frame of the caller.

Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190903214359.23887-1-santosh@fossix.org

diff --git a/arch/powerpc/lib/memcpy_mcsafe_64.S b/arch/powerpc/lib/memcpy_mcsafe_64.S
index 949976dc115dcc5f8a929b0ed1810e7945d9fade..cb882d9a6d8a3d897c41edb54b6d2b68c93852a0 100644 (file)
--- a/arch/powerpc/lib/memcpy_mcsafe_64.S
+++ b/arch/powerpc/lib/memcpy_mcsafe_64.S
@@ -84,7 +84,6 @@ err1; stw     r0,0(r3)
 
 3:     sub     r5,r5,r6
        cmpldi  r5,128
-       blt     5f
 
        mflr    r0
        stdu    r1,-STACKFRAMESIZE(r1)
@@ -99,6 +98,7 @@ err1; stw     r0,0(r3)
        std     r22,STK_REG(R22)(r1)
        std     r0,STACKFRAMESIZE+16(r1)
 
+       blt     5f
        srdi    r6,r5,7
        mtctr   r6