User Mode Interrupt Red Zone Stack Offset Mechanism
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Solution Overview
Problem
Current techniques for handling interrupts in modern processors require user programs to be mediated by the operating system, leading to poor performance and excessive privilege requirements, as well as potential destructive race conditions.
Innovation Solution
The method involves determining the execution mode of a processor for each interrupt and translating it for delivery to user mode programs, using a special interrupt register and interrupt descriptor table to bypass the operating system, allowing direct interrupt processing by user mode code without OS-level privileges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If interrupts are mediated by the operating system, then system control and security are maintained, but performance deteriorates and latency increases
Solution Approach 1:
The patent segments interrupt handling into two distinct paths: kernel-mode interrupts that require OS mediation, and user-mode interrupts that can be handled directly by user programs. This segmentation allows performance-critical user-mode interrupts to bypass the OS, reducing latency while maintaining security for privileged operations.
Solution Approach 2:
The patent introduces an intermediary mechanism (the red zone stack area and modified stack pointer handling) that enables user-mode programs to safely receive and process interrupts without full OS mediation. This intermediary structure provides the necessary context preservation while allowing direct user-mode interrupt handling.
2Ease of operation
If user mode programs are given OS level privileges for interrupt processing, then direct interrupt handling is enabled, but system security and stability are compromised
Solution Approach 1:
The patent applies local quality by providing different privilege levels for different interrupt handling scenarios. User-mode programs receive limited privileges specifically for handling their own interrupts in the red zone, while the rest of the system maintains standard security boundaries. This localized privilege elevation enables direct interrupt handling without compromising overall system security.
Solution Approach 2:
The patent dynamically adjusts privilege levels based on the interrupt source and target. When an interrupt is directed to a user-mode program, the system temporarily elevates privileges for that specific context, then restores normal privilege levels afterward. This dynamic approach enables flexible interrupt handling while maintaining security boundaries.
3Productivity
If the stack pointer is adjusted by a red zone offset for user mode interrupts, then proper stack management is achieved, but complexity in stack handling increases
Solution Approach 1:
The patent performs preliminary action by pre-configuring the red zone offset and establishing the stack pointer adjustment mechanism before interrupts occur. The compiler and runtime system set up the red zone area and associated data structures in advance, so that when user-mode interrupts occur, the stack pointer can be immediately adjusted without complex runtime calculations.
Data Source
AI summary
A method includes for each processed interrupt: determining whether the interrupt is a user mode interrupt; upon determining that the interrupt is a user mode interrupt, determining a stack location to insert an entry corresponding to the user mode interrupt, the stack location being calculated by adjusting a current stack pointer by a red zone offset; and inserting the entry corresponding to the user mode interrupt into the stack at the stack location.