26 research outputs found
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CheriRTOS: A Capability Model for Embedded Devices
Embedded systems are deployed ubiquitously
among various sectors including automotive, medical, robotics
and avionics. As these devices become increasingly connected,
the attack surface also increases tremendously; new mechanisms
must be deployed to defend against more sophisticated attacks
while not violating resource constraints. In this paper we present
CheriRTOS on CHERI-64, a hardware-software platform atop
Capability Hardware Enhanced RISC Instructions (CHERI) for
embedded systems.
Our system provides efficient and scalable task isolation,
fast and secure inter-task communication, fine-grained memory
safety, and real-time guarantees, using hardware capabilities as
the sole protection mechanism. We summarize state-of-the-art se-
curity and memory safety for embedded systems for comparison
with our platform, illustrating the superior substrate provided
by CHERI’s capabilities. Finally, our evaluations show that a
capability system can be implemented within the constraints of
embedded systems
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Efficient tagged memory
We characterize the cache behavior of an in-memory tag table and
demonstrate that an optimized implementation can typically achieve a near-zero memory traffic overhead. Both industry and academia have repeatedly demonstrated tagged memory as a key mechanism to enable enforcement of powerful security invariants, including capabilities pointer integrity, watchpoints, and information-flow tracking. A single-bit tag shadowspace is the most commonly proposed requirement, as one bit is the minimum metadata needed to distinguish between an untyped data word and any number of new hardware-enforced types. We survey various tag shadowspace approaches and identify their common requirements and positive features of their implementations. To avoid non-standard memory widths, we identify the most practical implementation for tag storage to be an in-memory table managed next to the DRAM controller. We characterize the caching performance of such a tag table and demonstrate a DRAM traffic overhead below 5\% for the vast majority of applications. We identify spatial locality on a page scale as the primary factor that enables surprisingly high table cache-ability. We then demonstrate tag-table compression for a set of common applications. A hierarchical structure with elegantly simple optimizations reduces DRAM traffic overhead to below 1\% for most applications. These insights and optimizations pave the way for commercial applications making use of single-bit tags stored in commodity memory
The neuroscience of suicidal behaviors: what can we expect from endophenotype strategies?
Vulnerability to suicidal behavior (SB) is likely mediated by an underlying genetic predisposition interacting with environmental and probable epigenetic factors throughout the lifespan to modify the function of neuronal circuits, thus rendering an individual more likely to engage in a suicidal act. Improving our understanding of the neuroscience underlying SBs, both attempts and completions, at all developmental stages is crucial for more effective preventive treatments and for better identification of vulnerable individuals. Recent studies have characterized SB using an endophenotype strategy, which aims to identify quantitative measures that reflect genetically influenced stable changes in brain function. In addition to aiding in the functional characterization of susceptibility genes, endophenotypic research strategies may have a wider impact in determining vulnerability to SB, as well as the translation of human findings to animal models, and vice versa. Endophenotypes associated with vulnerability to SB include impulsive/aggressive personality traits and disadvantageous decision making. Deficits in realistic risk evaluation represent key processes in vulnerability to SB. Serotonin dysfunction, indicated by neuroendocrine responses and neuroimaging, is also strongly implicated as a potential endophenotype and is linked with impulsive aggression and disadvantageous decision making. Specific endophenotypes may represent heritable markers for the identification of vulnerable patients and may be relevant targets for successful suicide prevention and treatments