Individually Revocable Capabilities for Temporal Memory Safety

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Solution Overview

Problem

Current memory safety mechanisms in hardware are inadequate in enforcing temporal memory safety and scalable compartmentalization, particularly failing to address temporal memory safety violations and non-adjacent spatial memory errors effectively, while also increasing pointer size and memory overhead.

Innovation Solution

The implementation of individually revocable capabilities (IRC) and encoded inline capabilities (EIC) within a zoned memory safety (ZMS) framework, which utilizes memory protection keys (MPK) and memory tagging to provide deterministic bounds checks and fine-grained access control without expanding pointer size, allowing for efficient compartmentalization and protection against various memory-related vulnerabilities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional memory safety mechanisms are used, then memory access can be protected, but temporal memory safety violations and non-adjacent spatial memory errors cannot be effectively addressed

Engineering Contradiction:

Improvememory safety enforcementVSAvoidtemporal and spatial memory violation coverage

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent segments memory safety enforcement into multiple independent capability checks: capability validity verification, bounds checking, and temporal safety verification. Each segment handles a specific aspect of memory safety, allowing comprehensive protection against various memory violations including temporal and spatial errors without requiring a monolithic complex system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces temporal safety bits as an additional dimension beyond traditional spatial memory protection. This temporal dimension tracks the lifecycle state of memory allocations, enabling detection of temporal memory safety violations such as use-after-free and double-free errors that conventional spatial-only mechanisms cannot detect.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If pointer size is increased to provide more memory safety information, then memory safety enforcement is improved, but memory overhead increases

Engineering Contradiction:

Improvememory safety enforcementVSAvoidmemory overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent merges multiple safety checks (capability validity, bounds checking, and temporal safety verification) into a single unified capability structure. This consolidation allows comprehensive memory safety enforcement without requiring multiple separate data structures or increasing pointer size, as all safety information is integrated into the existing capability mechanism.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent utilizes temporal safety bits as changeable parameters within the capability structure that can be dynamically set and cleared based on memory allocation lifecycle. These bits provide temporal safety information without requiring additional pointer size, as they are embedded within the existing capability fields rather than requiring separate storage.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If fine-grained access control is implemented, then compartmentalization is improved, but system complexity increases

Engineering Contradiction:

Improvecompartmentalization capabilityVSAvoidaccess control mechanism complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The capability-based access control mechanism is self-service in that capabilities are automatically verified by the memory management unit during memory access operations. The system self-enforces compartmentalization policies without requiring complex external validation logic, as the capability structure inherently contains all necessary authorization information that is automatically checked during access.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Capabilities are pre-configured with all necessary access control information, bounds, and temporal safety parameters before memory access occurs. This preliminary configuration allows the memory management unit to perform simple verification checks during runtime without requiring complex decision-making logic, as all authorization criteria are predetermined in the capability structure.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11782716B2Hardware apparatuses, methods, and systems for individually revocable capabilities for enforcing temporal memory safety

Publication Date: 2023.10.10 INTEL CORP

AI summary

Systems, methods, and apparatuses relating to circuitry to implement individually revocable capabilities for enforcing temporal memory safety are described. In one embodiment, a hardware processor comprises an execution unit to execute an instruction to request access to a block of memory through a pointer to the block of memory, and a memory controller circuit to allow access to the block of memory when an allocated object tag in the pointer is validated with an allocated object tag in an entry of a capability table in memory that is indexed by an index value in the pointer, wherein the memory controller circuit is to clear the allocated object tag in the capability table when a corresponding object is deallocated.