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Recent rapid strides in memory safety tools and hardware have improved software quality and security. While coarsegrained memory safety has improved, achieving memory safety at the granularity of individual objects remains a challenge due to high performance overheads which can be between ∼1.7x−2.2x. In this paper, we present a novel idea called Califorms, and associated program observations, to obtain a low overhead security solution for practical, bytegranular memory safety.The idea we build on is called memory blacklisting, which prohibits a program from accessing certain memory regions based on program semantics. State of the art hardwaresupported memory blacklisting while much faster than software blacklisting creates memory fragmentation (of the order of few bytes) for each use of the blacklisted location. In this paper, we observe that metadata used for blacklisting can be stored in dead spaces in a program's data memory and that this metadata can be integrated into microarchitecture by changing the cache line format. Using these observations, Califorms based system proposed in this paper reduces the performance overheads of memory safety to ∼1.02x−1.16x while providing byte-granular protection and maintaining very low hardware overheads.The low overhead offered by Califorms enables always on, memory safety for small and large objects alike, and the fundamental idea of storing metadata in empty spaces, and microarchitecture can be used for other security and performance applications.

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Many modern defenses against code reuse rely on hiding sensitive data such as shadow stacks in a huge memory address space. While much more efficient than traditional integritybased defenses, these solutions are vulnerable to probing attacks which quickly locate the hidden data and compromise security. This has led researchers to question the value of information hiding in real-world software security. Instead, we argue that such a limitation is not fundamental and that information hiding and integrity-based defenses are two extremes of a continuous spectrum of solutions. We propose a solution, ProbeGuard, that automatically balances performance and security by deploying an existing information hiding based baseline defense and then incrementally moving to more powerful integrity-based defenses by hotpatching when probing attacks occur. ProbeGuard is efficient, provides strong security, and gracefully trades off performance upon encountering more probing primitives. CCS Concepts • Security and privacy → Systems security; Software security engineering.

Much research has gone into making operating systems more amenable to recovery and more resilient to crashes. Traditional solutions rely on partitioning the operating system (OS) to contain the effects of crashes within compartments and facilitate modular recovery. However, state dependencies among the compartments hinder recovery that is globally consistent. Such recovery typically requires expensive runtime dependency tracking which results in high performance overhead, high complexity and a large Reliable Computing Base (RCB). We propose a lightweight strategy that limits recovery to cases where we can statically and conservatively prove that compartment recovery leads to a globally consistent statetrading recoverable surface for a simpler and smaller RCB with lower performance overhead and maintenance cost. We present OSIRIS, a research OS design prototype that demonstrates efficient and consistent crash recovery. Our evaluation shows that OSIRIS effectively recovers from important classes of real-world software bugs with a modest RCB and low overheads.