Method for executing a 32-bit flat address program during a system management mode interrupt
AssigneeGeneral Software, Inc.
InventorStephen E. Jones
Life of this patent
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Abstract
A method and system for executing 32-bit flat address programs during a System Management Interrupt. The system provides a 16-bit SMI routine that is given control when an SMI occurs. That routine initially saves the state of the processor and then executes an instruction to switch to protected mode. When in protected mode, the routine transfers control to 32-bit code. The 32-bit code uses a global descriptor table that is different from that used by the interrupted operating system. When the 32-bit code completes, it restores the saved processor state and returns from the interrupt by executing an RSM instruction.
Claims19
A method in a computer system having a global descriptor table register for executing code during a system management mode interrupt (SMI), the method comprising:
- upon occurrence of the SMI,
- saving state of the computer system;
- switching the computer system to protected mode;
- replacing first contents of the global descriptor table register that point to a first global descriptor table in use when the system management mode interrupt occurred with second contents that point to a second global descriptor table that is distinct from the first global descriptor table;
- executing 32-bit code using the second global descriptor table;
- and
- upon completion of the execution of the 32-bit code,
- restoring the saved state of the computer system;
- and
- returning from the occurrence of the SMI.
Dependencies are inferred from the claim text.