Patent ID: 7277998

Claim:
A method performed in a computer system for enabling a first software entity to use an address space of a second software entity while preventing the second software entity from accessing memory of the first software entity, the computer system implementing segmented memory and memory paging, the computer system having a first operating mode in which instructions are executed at a more-privileged level and in which a first set of one or more instructions accesses the memory of the first software entity and a second set of one or more instructions is to be prevented from accessing the memory of the first software entity, the computer system also having a second operating mode in which instructions are executed at a less-privileged level and in which a third set of instructions is to be prevented from accessing the memory of the first software entity, the method comprising: activating memory paging protection so that instructions executed at the less-privileged level cannot access the memory of the first software entity; during the first operating mode, using effectively truncated memory segments for the second set of instructions, the effectively truncated memory segments excluding the memory of the first software entity; and during the second operating mode, using one or more untruncated memory segments for the third set of instructions, at least one of the untruncated memory segments including at least a portion of the memory of the first software entity.