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ARM Compiler Software Development Guide : Automatic overlay support

Automatic overlay support

For the linker to automatically allocate code sections to overlay regions, you must modify your C or assembly code to identify the parts to be overlaid. You must also set up a scatter file to locate the overlays.

The automatic overlay mechanism consists of:

  • Special section names that you can use in your object files to mark code as overlaid.
  • The AUTO_OVERLAY execution region attribute. Use this in a scatter file to indicate regions of memory where the linker assigns the overlay sections for loading into at runtime.
  • The command-line option --overlay-veneers to make the linker redirect calls between overlays to a veneer that lets an overlay manager unload and load the correct overlays.
  • A set of data tables and symbol names provided by the linker that you can use to write the overlay manager.
  • The armlink --emit_debug_overlay_section command-line options to add extra debug information to the image. This option permits an overlay-aware debugger to track which overlay is currently active.

This section contains the following subsections: