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Methods for safe and efficient implementations of virtual machines

  • US 5,761,477 A
  • Filed: 12/04/1995
  • Issued: 06/02/1998
  • Est. Priority Date: 12/04/1995
  • Status: Expired due to Term
First Claim
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1. A computer implemented method for preventing transfer of control to illegal memory addresses during execution of a sequence of virtual machine instructions, operating in a computer system having memory, the method comprising the steps:

  • generating a sequence of machine executable instructions to carry out the operations defined by the sequence of virtual machine instructions;

    providing, in a computer storage medium, status information, said status information indicating the illegal memory addresses which the sequence of virtual machine instructions is not allowed to transfer control to, and legal memory addresses which the sequence of virtual machine instructions is allowed to transfer control to;

    analyzing the sequence of virtual machine instructions and generating a sequence of machine executable instructions to carry out operations defined by the sequence of virtual machine instructions; and

    encapsulating a machine executable instruction that can cause transfer of control to the illegal memory addresses with a predetermined sequence of machine executable checking instructions so that said predetermined sequence of machine executable checking instructions is executed in conjunction with said machine executable instruction that can cause transfer of control to said illegal memory addresses, the predetermined sequence of machine executable checking instructions signaling an error if said machine executable instruction that can cause transfer of control to the illegal memory addresses does attempt to transfer control to one of said illegal memory addresses.

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