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 949976d..cb882d9 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