s390/fpu: signals vs. floating point control register

git commit 904818e2f229f3d94ec95f6932a6358c81e73d78
"s390/kernel: introduce fpu-internal.h with fpu helper functions"
introduced the fpregs_store / fp_regs_load helper. These function
fail to save and restore the floating pointer control registers.

The effect is that the FPC is not correctly handled on signal
delivery and signal return.

Cc: stable@vger.kernel.org # 4.4
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/fpu/internal.h

@@ -40,6 +40,7 @@ static inline void convert_fp_to_vx(__vector128 *vxrs, freg_t *fprs)
 static inline void fpregs_store(_s390_fp_regs *fpregs, struct fpu *fpu)
 {
 	fpregs->pad = 0;
+	fpregs->fpc = fpu->fpc;
 	if (MACHINE_HAS_VX)
 		convert_vx_to_fp((freg_t *)&fpregs->fprs, fpu->vxrs);
 	else
@@ -49,6 +50,7 @@ static inline void fpregs_store(_s390_fp_regs *fpregs, struct fpu *fpu)
 
 static inline void fpregs_load(_s390_fp_regs *fpregs, struct fpu *fpu)
 {
+	fpu->fpc = fpregs->fpc;
 	if (MACHINE_HAS_VX)
 		convert_fp_to_vx(fpu->vxrs, (freg_t *)&fpregs->fprs);
 	else