Flat memory (MEM_FLAT)

The microkernel and all applications run in one unique, unprotected address space. This module provides simple memory allocation services.

The flat memory module, MEM_FLAT, is suited for systems that do not have a memory management unit (MMU), or when use of the memory management unit is required for reasons of efficiency only.

Virtual addresses match physical addresses directly. Applications cannot allocate more memory than is physically available.

Address Spaces

A unique supervisor address space, matching the physical address space, is featured. Any actor can access any part of physically mapped memory, such as ROM, memory mapped I/O, or anywhere in RAM.

On a given site, memory objects can be shared by several actors. Sharing of fractions of one memory object is not available.

At region creation time, the memory object is either allocated from free physical RAM memory or shared from the memory object of another region.

The concept of sharing of memory objects is provided to control the freeing of physical memory. The memory object associated with a region is returned to the pool of free memory when the associated region is removed from its last context. This concept of sharing does not prevent an actor from accessing any part of the physically mapped memory.

Regions

The context of an actor is a collection of non-overlapping regions. The microkernel associates a linear buffer of physical memory to each region, consisting of a memory object. The memory object and the region have the same address and size.

It is not possible to wait for memory at the moment of creation of a region. The memory object must be obtainable immediately, either by sharing or by allocating free physical memory.

Protections

There is no default protection mechanism.