Standard C lib. Functions Running Sector

Hi friends.

Now I have a project which needs that the whole standard C lib functions, such as "memcpy", "sin" ... runs in a specific ram sector.  If I dont operate like this, these functions would run on Extern Flash, As we know, it would Make the whole softWare run very slow。So I have to change the whole standard C lib functions' running sector.

How should I do? Look forward to your soonest reply