Dynamic Address Translation with Access Control
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Solution Overview
Problem
Current dynamic address translation facilities lack enhanced functionality, capability, and protection mechanisms, which limits their ability to effectively manage and secure virtual address translations in computer systems with hierarchical translation tables.
Innovation Solution
An enhanced dynamic address translation facility is introduced, which includes a system, method, and computer program product that translates virtual addresses into real or absolute addresses using a hierarchy of translation tables, with features such as prefixing for absolute address formation, access validity and protection fields, and key-controlled access mechanisms to ensure secure data access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dynamic address translation is implemented using hierarchical translation tables, then virtual storage management capability is improved, but system complexity increases
Solution Approach 1:
The address translation function is segmented into multiple hierarchical levels (segment tables and page tables). Segment tables translate virtual addresses to segment frame addresses, while page tables translate virtual addresses to page frame addresses. This segmentation allows the system to manage large virtual storage spaces by dividing the translation process into manageable stages, resolving the contradiction between enhanced virtual storage management capability and system complexity.
2Reliability
If access control fields and protection fields are added to translation table entries, then security and access control capability are improved, but translation table entry size and processing overhead increase
Solution Approach 1:
Access control and protection fields are added locally to specific translation table entries (segment table entries and page table entries) rather than being implemented system-wide. Each entry can independently contain access control fields (0-3 bits) and protection fields, allowing fine-grained security control only where needed. This local implementation improves security capability while minimizing the increase in entry size and processing overhead.
3Reliability
If key-controlled access mechanisms are implemented, then access security is improved, but access operation complexity increases
Solution Approach 1:
The key-controlled access mechanism operates automatically through the address translation process. When a virtual address is translated, the system automatically retrieves the access key from the translation table entry and compares it with the program key without requiring explicit programming or manual intervention. This self-service approach improves access security while maintaining ease of operation, as the security check is transparent to the program execution.
Data Source
AI summary
What is provided is an enhanced dynamic address translation facility. In one embodiment, a virtual address to be translated and an initial origin address of a translation table of the hierarchy of translation tables are obtained. Based on the origin address, a segment table entry is obtained which contains a format control field and an access validity field. If the format control and access validity are enabled, the segment table entry further contains an access control and fetch protection fields, and a segment-frame absolute address. Store operations to the block of data are permitted only if the access control field matches a program access key provided by either a Program Status Word or an operand of a program instruction being executed. Fetch operations from the desired block of data are permitted only if the program access key associated with the virtual address is equal to the segment access control field.