64-bit Application Exception Handling via 32-bit Kernel Mode Switching

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Solution Overview

Problem

Migrating from a 32-bit architecture to a 64-bit architecture is resource-intensive and time-consuming, requiring significant modifications to the operating system kernel and device drivers, leading to potential bugs and substantial engineering efforts.

Innovation Solution

A system that uses a 32-bit OS kernel to support 64-bit applications by switching to 32-bit mode for exception handling and mapping applications to virtual memory, allowing a 32-bit kernel to execute 64-bit processes while maintaining backward compatibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If extensive modifications are made to the OS kernel to support 64-bit architecture, then the system can natively support 64-bit applications, but the migration process becomes time-consuming and resource-intensive

Engineering Contradiction:

Improve64-bit application supportVSAvoidmigration time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent introduces a 64-bit user mode as an intermediary layer that allows 64-bit applications to execute on a 32-bit kernel. The kernel maintains its 32-bit architecture while providing controlled access to 64-bit user space, eliminating the need to modify the kernel for 64-bit support.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system is segmented into distinct 32-bit kernel space and 64-bit user space. This segmentation allows each part to operate independently with its native architecture, avoiding the need to modify the entire system for 64-bit compatibility.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If extensive modifications are made to the OS kernel, then 64-bit architecture support is achieved, but subtle bugs are introduced that take weeks or months to identify and fix

Engineering Contradiction:

Improve64-bit architecture supportVSAvoidkernel stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

By segmenting the system into 32-bit kernel and 64-bit user mode, the patent isolates the stable 32-bit kernel from 64-bit operations. This prevents bugs from being introduced into the kernel while still enabling 64-bit application execution in the user space.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The 64-bit user mode acts as an intermediary that handles 64-bit operations without requiring kernel modification. This protects the kernel's stability while providing 64-bit functionality through the intermediary layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If a new 64-bit OS kernel is created, then 64-bit applications can execute natively, but device drivers must be rewritten by third party vendors

Engineering Contradiction:

Improve64-bit application executionVSAvoiddevice driver compatibility

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The 32-bit kernel is designed to be universal, supporting both 32-bit and 64-bit applications through its dual-mode architecture. Existing device drivers continue to function without modification since the kernel interface remains compatible.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The 64-bit user mode serves as an intermediary that allows 64-bit applications to interact with the 32-bit kernel through existing driver interfaces, eliminating the need for driver rewriting while enabling 64-bit execution.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Ease of manufacture

If a 32-bit kernel is used to support 64-bit applications, then migration is simplified, but the system must switch processor modes for exception handling

Engineering Contradiction:

Improvemigration easeVSAvoidprocessor mode switching

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The system segments processor operation into 32-bit kernel mode and 64-bit user mode, allowing simple migration while managing mode switching as a controlled transition between segmented states rather than a system-wide complexity.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS7451298B2Processing exceptions from 64-bit application program executing in 64-bit processor with 32-bit OS kernel by switching to 32-bit processor mode

Publication Date: 2008.11.11 APPLE INC

AI summary

One embodiment of the present invention provides a system that uses an M-bit operating system (OS) kernel to support N-bit user processes. During operation, the system receives an exception. Note that the exception can be any event that needs to be handled by executing OS kernel code. Specifically, the exception can be a hardware interrupt, a software interrupt, an asynchronous interrupt, a synchronous interrupt, a signal, a trap, or a system call. Next, the system handles the exception by first switching the processor to the M-bit mode, and then executing M-bit OS kernel code which is designed to handle the exception. Note that the processor may primarily be designed to operate in the N-bit mode; the M-bit mode may primarily be provided for backward compatibility reasons.