Summary BasicBlocker ISA Redesign for Spectre-Immune CPUs arxiv.org
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One Line
The text explains how the BasicBlocker ISA redesign addresses Spectre vulnerabilities by removing speculative execution.
Slides
Slide Presentation (9 slides)
Key Points
- BasicBlocker is a generic ISA modification that eliminates speculative execution in CPUs to mitigate the security vulnerabilities exploited by Spectre.
- BasicBlocker introduces a simple and efficient hardware implementation that minimizes the performance penalty of removing branch prediction and speculative fetching.
- A CPU supporting BasicBlocker can run code compiled for the old ISA without compromising security, improving deployability.
- The BasicBlocker ISA redesign introduces a new instruction called the basic block (bb) instruction, which provides information about the size and sequentiality of upcoming basic blocks.
- An attacker can manipulate the bb instruction to control certain parts of the control flow, such as flipping the sequential flag or decreasing the basic block size.
- The performance of BasicBlocker on the VexRiscv processor was evaluated, showing an average speedup of 2.88x compared to a non-control-flow-speculative processor.
- The research paper discusses the redesign of the BasicBlocker ISA to create CPUs that are immune to Spectre attacks and evaluates their performance using the Gem5 simulator.
- The excerpt includes references to related research papers on branch prediction, instruction fetching, and defenses against transient-execution attacks.
Summaries
18 word summary
This text discusses the BasicBlocker ISA redesign for Spectre-immune CPUs, which eliminates speculative execution and mitigates security vulnerabilities.
37 word summary
The text discusses the BasicBlocker ISA redesign for Spectre-immune CPUs. BasicBlocker is a generic ISA modification that eliminates speculative execution in CPUs to mitigate the security vulnerabilities exploited by Spectre. It introduces BasicBlocker, a simple and efficient
826 word summary
BasicBlocker is a generic ISA modification that eliminates speculative execution in CPUs to mitigate the security vulnerabilities exploited by Spectre. It introduces BasicBlocker, a simple and efficient hardware implementation that minimizes the performance penalty of removing branch prediction and speculative fetching.
To improve deployability, a CPU supporting BasicBlocker can run code compiled for the old ISA without compromising security. The BasicBlocker concept reduces the branch-misprediction cost by ensuring that instructions are executed consecutively and allowing the branch to
ISA extensions add new instructions to harden programs against specific attacks, but hardware changes are required to support them. Some ISAs remove control-flow speculation, while others introduce instruction-level parallelism. VLIW architectures rely on compiler heuristics and require
The BasicBlocker ISA redesign introduces a new instruction called the basic block (bb) instruction, which provides information about the size and sequentiality of upcoming basic blocks. This allows the CPU to fetch instructions in sequential order without needing to stall fetching until the
The basic block's target register defaults to +4 for sequential blocks, but points to the target address for control-flow operations. The code is compatible with all hardware architectures that support the bb instruction. Rescheduling control-flow instructions optimizes the code for hardware
Optimizations to the ISA can be made by replacing the 1-bit sequential flag with a multi-bit counter for control-flow instructions. Hardware loop counters can be supported by announcing loops to the hardware and using a new instruction (lcnt) to store
Secondary pipelines can pre-execute basic block (bb) instructions in parallel, increasing CPU state that needs to be saved during interrupts and context switches. A BasicBlocker CPU is backward-compatible and can be integrated into a secure enclave. BasicBlocker prevents
An attacker can manipulate the bb instruction to control certain parts of the control flow, such as flipping the sequential flag, decreasing or increasing the basic block size. Flipping the sequential flag leads to an exception, while decreasing the basic block size allows skipping critical
Linker relaxation is an optimization that can reduce the number of instructions by replacing calls with a short jumping distance with a single jump instruction. The researchers disabled linker relaxation but suggested modifying the linker to implement BasicBlocker-aware relaxation. The BasicBlocker modification
The performance of BasicBlocker on the VexRiscv processor was evaluated, comparing it to a non-control-flow-speculative processor. The average speedup over all benchmarks was 2.88x for the version using control-flow speculation and
The research paper discusses the redesign of the BasicBlocker ISA to create CPUs that are immune to Spectre attacks. The study evaluates the performance of the redesigned CPUs using the Gem5 simulator, which simulates a more advanced processor. The results show that
The text excerpt discusses the BasicBlocker ISA redesign for Spectre-immune CPUs. The authors present a universal countermeasure against control-flow speculation attacks like Spectre, challenging the assumption that speculation is necessary for performance. They propose a concept to transfer control
A list of references to related research papers on branch prediction, instruction fetching, and defenses against transient-execution attacks is provided. The papers cover topics such as the impact of if-conversion and branch prediction on program execution, measurement and analysis of instruction use
This excerpt includes various citations and references to different sources related to computer architecture and CPU optimization. It mentions the work of Joseph A Fisher on very long instruction word architectures, Agner Fog's optimization guide for assembly programmers and compiler makers, the Embench I
This summary presents a list of references cited in a document on the BasicBlocker ISA Redesign for Spectre-Immune CPUs. The references include papers on speculative buffer overflows, Spectre attacks, LLVM compilation framework, abstract PRET machines,
This excerpt is a list of references cited in a document about the redesign of the BasicBlocker ISA for Spectre-Immune CPUs. The references include various papers and articles related to microarchitectural side channels, attacks, and defenses, as
Hardware loop counters are a valuable concept for improving performance in programs with loops that do not terminate early. The hardware loop counter is set by a dedicated instruction and decrements after each iteration, inducing a branch back to the start of the loop. In the
We modified the st software to create st-opt, which computes the same results as st but at a higher speed. We used a profiler to identify bottlenecks on an existing CPU and removed inefficiencies while retaining portability. Three case studies were selected
Increased attention to RISC-V optimization will spur the development of branchless carryless algorithms for 64-bit operations, improving performance on existing CPUs. Inefficiencies in the original code arise from loop overhead and function-call overhead, which can be reduced by
Figures 31 to 45 of the document show graphs for Gem5. These graphs display pipeline delay, basic block (BB) information, BB rescheduling, and early decode for various scenarios. The figures include VexRiscv benchmarks such
The excerpted text provides information about the Gem5 simulation results for the BasicBlocker ISA Redesign for Spectre-Immune CPUs. The graphs and benchmark results are shown for various benchmarks, including Coremark, aha-mont, crc32