Partitioned Tags, Shared Data: Reconciling Strict Cache Isolation with Write-Shared Coherence
分区标签,共享数据:严格缓存隔离与写共享一致性的调和
Kartik Ramkrishnan, Stephen McCamant, Antonia Zhai, Pen Chung Yew
AI总结 提出SCP方法,通过仅分区标签、共享数据池并调整大小避免容量驱逐,结合时序混淆和写泄漏阈值,在严格隔离下实现写共享一致性,有效防御Prime+Probe和Flush+Reload攻击。
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缓存分区是针对基于驱逐的缓存侧信道攻击最强大的结构性防御之一,然而一个存在十年的设计问题阻碍了其在安全共享操作系统环境中的广泛部署。该问题是写共享一致性在严格分区下会崩溃。我们提出SCP(安全且一致的分区),它通过仅分区标签、共享单个数据池,并调整数据池大小以避免容量驱动的跨分区驱逐,从而将严格的驱逐隔离与写共享一致性结合起来。时序混淆将保护扩展到分区间的查找路径。通过将写操作在泄漏阈值超过后路由到LLC,减轻了共享可写行上的基于一致性的泄漏,这使得攻击者的写探测延迟与受害者活动无关。使用gem5实现,SCP缓解了Prime+Probe和Flush+Reload攻击,这些是更复杂缓存攻击的基础。我们还展示了一个共享可写行攻击被缓解。所有这些攻击的结果都不优于随机猜测。SCP的硬件成本是LLC SRAM适度增加2.8%。在我们评估的SPEC CPU2017基准测试中,性能在IPC上与DAWG相差在0.3%以内。共享密集型微基准测试展示了基于系统指定泄漏阈值的可调安全-性能权衡。
Cache partitioning is among the strongest structural defenses against eviction-based cache side channels, yet a decade-old design issue has blocked its widespread deployment in secure shared-OS settings. The issue is that write-shared coherence collapses under strict partitioning. We present SCP (Secure and Coherent Partitioning), which combines strict eviction isolation with write-shared coherence by partitioning only the tags, sharing a single data pool, and sizing the data pool so capacity-driven cross-partition eviction cannot occur. Timing obfuscation extends protections to the inter-partition lookup path. Coherence-based leakage on shared-writeable lines is mitigated by routing those writes through to the LLC once a leakage threshold is crossed, which makes attacker write probe latency independent of victim activity. Using gem5 for implementation, SCP mitigates Prime+Probe and Flush+Reload, which are the basis for more sophisticated cache attacks. We also demonstrate that a shared-writeable-line attack is mitigated. All these attacks yield results no better than random guessing. SCP's hardware cost is a modest +2.8% LLC SRAM. Performance matches DAWG within 0.3% IPC on the SPEC CPU2017 benchmarks that we evaluated. Sharing-intensive microbenchmarks demonstrate a tunable security-performance tradeoff based on a system-specified leakage threshold.