Re: [PATCH v10 02/14] unwind_user: Add frame pointer support

 int unwind_user_next(struct unwind_user_state *state)
 {
+	struct unwind_user_frame *frame;
+	unsigned long cfa = 0, fp, ra = 0;
+
+	if (state->done)
+		return -EINVAL;
+
+	if (fp_state(state))
+		frame = &fp_frame;
+	else
+		goto the_end;
+
+	cfa = (frame->use_fp ? state->fp : state->sp) + frame->cfa_off;
+
+	/* stack going in wrong direction? */
+	if (cfa <= state->sp)
+		goto the_end;
+
+	if (get_user(ra, (unsigned long *)(cfa + frame->ra_off)))
+		goto the_end;
+
+	if (frame->fp_off && get_user(fp, (unsigned long __user *)(cfa + frame->fp_off)))
+		goto the_end;
+
+	state->ip = ra;
+	state->sp = cfa;
+	if (frame->fp_off)
+		state->fp = fp;
+
+	return 0;
+
+the_end:
+	state->done = true;
 	return -EINVAL;
 }