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Virtual memory allocation in a virtual address space having an inaccessible gap

  • US 6,125,430 A
  • Filed: 10/30/1998
  • Issued: 09/26/2000
  • Est. Priority Date: 05/03/1996
  • Status: Expired due to Term
First Claim
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1. A virtual memory system comprising:

  • a virtual address space formed by implementation of a subset of a full range of virtual addresses permitted by a virtual address size, such that the virtual address space has at least one gap of permanently inaccessible virtual addresses, among accessible virtual addresses within said virtual address space;

    a virtual memory allocation routine, responsive to a request for allocation of additional page table entries for accessible virtual addresses by a currently executing process, said request including a byte length and associated with a first free virtual address, for providing a starting address of a range of additional accessible virtual addresses to said currently executing process;

    a gap limit equal to a lowest virtual address greater than said permanently inaccessible range of virtual addresses within said virtual address space;

    means, within said virtual memory allocation routine, for calculating an end address of said request equal to a sum of said first free virtual address plus said byte length; and

    means, within said virtual memory allocation routine, for determining if said end address is within said permanently inaccessible range of virtual addresses, and for setting said starting address to said gap limit if said end address is within said permanently inaccessible range of virtual addresses.

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