+ struct mcontext __user *mctx;
+
+ /*
+ * old_ctx might not be 16-byte aligned, in which
+ * case old_ctx->uc_mcontext won't be either.
+ * Because we have the old_ctx->uc_pad2 field
+ * before old_ctx->uc_mcontext, we need to round down
+ * from &old_ctx->uc_mcontext to a 16-byte boundary.
+ */
+ mctx = (struct mcontext __user *)
+ ((unsigned long) &old_ctx->uc_mcontext & ~0xfUL);