Reentrant protected mode kernel using virtual 8086 mode interrupt service routines
US5303378A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 21, 1991 |
| Grant date | Apr 12, 1994 |
| Priority date | — |
| Expiry date | May 21, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F12/1491
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.