Reentrant protected mode kernel using virtual 8086 mode interrup

Details Reentrant protected mode kernel using virtual 8086 mode interrup Reentrant protected mode kernel using virtual 8086 mode interrup

1991-05-21

1994-04-12

Shaw, Gareth D.

Boots, shoes, and leggings

395400, 3642808, 3642809, 364DIG1, G06F 1200

Patent

active

053033787

ABSTRACT:
A method for allowing a protected mode kernel to service, in virtual 8086 mode, hardware interrupts which occur during execution of ring 0 protected mode code. When an interrupt occurs during execution of ring 0 code, the microprocessor copies the state of the last virtual 8086 environment on the top of the ring 0 stack and modifies this state to begin execution of the appropriate interrupt service routine in virtual 8086 mode. The kernel utilizes a secondary stack to keep track of the last virtual 8086 environment saved on the ring 0 stack and updates the ring 0 stack pointer in the respective task's task state segment to the new beginning of the ring 0 stack each time a ring transition occurs from ring 3 V86 mode to ring 0 protected mode. By manipulating the ring 0 stack and utilizing the secondary stack to keep track of interrupted V86 environments, the kernel can allow interrupts to be nested down multiple levels.

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John Uffenbeck, Microcomputers and Microprocessors: The 8080, 8085, and Z-80 Programming, Interfacing, and Troubleshooting, 1985, pp. 257-273.
James Turley, "Advanced 80386 Programming Techniques", McGraw-Hill, 1988, pp. 283-315.

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