5.3. Overlays

Overlays permit multiple sections of code and data to be linked to execute from the same address within the same image. Normally in a statically linked image code and data is linked at a unique location and the static linker does not allow multiple items to be placed at the same location.An executing image that uses overlays has to manage which code and data, normally referred to as an overlay or overlay region, is currently in the shared memory location. The image has to ensure that the correct overlay is active (in memory) when trying to execute code or access data from within it.An image normally has an overlay manager that handles which overlay is currently active and copies the code and data to the overlay memory region.

Figure 5.2. Overlays

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