Control Flow Speculation State Tracking for Secure Execution
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Solution Overview
Problem
Speculative execution in data processing, particularly control flow speculation, can lead to security vulnerabilities such as unintended access to secured data, as processors may speculatively execute privileged code and fail to clear caches properly, allowing side-channel attacks.
Innovation Solution
An apparatus and method that generate sequences of instructions with indirect control flow instructions, storing a state of control flow speculation after execution, and using speculation barriers to inhibit data value speculation, ensuring correct control flow speculation tracking and secure data access by maintaining a state of control flow speculation across function calls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If control flow speculation is performed to improve processing speed, then execution speed is improved, but security vulnerabilities occur due to unauthorized access to privileged data
Solution Approach 1:
The patent applies preliminary action by performing control flow speculation before the actual control flow decision is resolved. The processor speculatively executes instructions along predicted control flow paths, and only after the speculation is validated or invalidated does the system commit or discard the speculative results. This allows speed improvement while maintaining security through subsequent validation.
Solution Approach 2:
The patent introduces intermediary mechanisms including speculation state tracking and validation logic that act as mediators between speculative execution and secure data access. These intermediaries monitor control flow speculation, track speculative states, and prevent unauthorized access to privileged data by validating speculation before allowing access to sensitive resources.
2Productivity
If speculative execution is allowed to improve performance, then processing throughput is improved, but data leaks occur through side-channel attacks
Solution Approach 1:
The patent implements feedback mechanisms where the processor continuously monitors control flow speculation outcomes and feeds this information back to validate or invalidate speculative execution paths. The speculation state tracking system provides feedback about whether speculative access to data was legitimate, preventing data leaks by using this feedback to control subsequent access and prevent side-channel attacks.
3Reliability
If control flow speculation tracking is implemented to prevent security issues, then data security is improved, but instruction complexity increases
Solution Approach 1:
The patent applies segmentation by dividing control flow speculation tracking into distinct components: speculation state tracking, validation logic, and control flow management. Each component handles a specific aspect of speculation management, making the overall system more manageable and less complex than a monolithic approach would require.
Data Source
AI summary
There is provided input circuitry to receive input data. Output circuitry outputs a sequence of instructions to be executed by data processing circuitry. Generation circuitry performs a generation process to generate the sequence of instructions using the input data with at least some of the instructions being grouped into functions. The sequence of instructions comprises an indirect control flow instruction comprising a field that indicates where a target of the indirect control flow instruction is stored. The target is an entry point to one of the functions and the generation process causes at least one of the instructions in the sequence of instructions to store a state of control flow speculation after execution of the indirect control flow instruction.