The OSKit provides a small library that can recognize and load program executables in a variety of formats. It is analogous to the GNU Binary File Descriptor (BFD) library, except that it only supports loading linked program executables rather than general reading and writing of all types of object files. For this reason, it is much smaller and simpler than BFD.
Furthermore, as with the other OSKit components, the executable interpreter library is designed to be as generic and environment-independent as possible, so that it can readily be used in any situation in which it is useful. For example, the library does not directly do any memory allocation; it operates purely using memory provided to it explicitly. Furthermore, it does not make any assumptions about how a program's code and data are to be written into the proper target address space; instead it uses generic callback functions for this purpose. All of the library functions are pure, not containing or relying on any global shared state.
All of the executable loading functions take pointers to two callback functions as parameters; the library calls these functions, which the client OS must provide, to load data from the executable and map or copy it into the address space of the program being loaded. Since all loading is done through these callback functions, the OSKit's executable interpreter code can be used to load executables either into the same address space as the program currently running (e.g., loading a kernel from a boot loader) or into a different address space. The prototypes and semantics of these callback functions are defined below, in Section 23.2.