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Self Relocating Dynamically Loaded Modules and Loader

IP.com Disclosure Number: IPCOM000081720D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Myers, JJ: AUTHOR

Abstract

In operating systems in mini and small computers, there is normally required a permanently resident relocating loader program. Such requirement results in relatively high overhead, need for extra processing time, extra space for relocating programs as they are loaded and additional space for the relocation information.

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Self Relocating Dynamically Loaded Modules and Loader

In operating systems in mini and small computers, there is normally required a permanently resident relocating loader program. Such requirement results in relatively high overhead, need for extra processing time, extra space for relocating programs as they are loaded and additional space for the relocation information.

In the technique described, there is provided a mechanism for an operating system in a small or minicomputer, which has a direct access storage device attached thereto to dynamically load modules into memory at any location on demand, without the need for such permanently resident relocating loader program and the extra costs and disadvantages that such need entails.

With this technique, there is achieved the effect of relocation by providing macro instructions for each machine instruction which uses an address that has to be relocated. These macro instructions add the base address of the module (the load point which is passed as a parameter to the module) inline before using it. Thereby the code is dynamically relocated. The consequence of the technique is the requirement that modules have to be slightly larger than normal (5 - 10%) but the flexibility greatly outweighs this disadvantage, since the extra space required for the slightly larger modules is needed for only a small percentage of the time.

To summarize the foregoing, the technique described effects dynamic loading from direct access...