Browsing by Author "Sahu, Raj"

Now showing 1 - 4 of 4
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    Enabling BPF Runtime policies for better BPF management
    Sahu, Raj; Williams, Dan (ACM, 2023-09-10)
    As eBPF increasingly and rapidly gains popularity for observability, performance, troubleshooting, and security in production environments, a problem is emerging around how to manage the multitude of BPF programs installed into the kernel. Operators of distributed systems are already beginning to use BPF-orchestration frameworks with which they can set load and access policies for who can load BPF programs and access their resultant data. However, other than a guarantee of eventual termination, operators currently have little to no visibility into the runtime characteristics of BPF programs and thus cannot set policies that ensure their systems still meet crucial performance targets when instrumented with BPF programs. In this paper, we propose that having a runtime estimate will enable better policies that will govern the allowed latency in critical paths. Our key insight is to leverage the existing architecture within the verifier to statically track the runtime cost of all possible branches. Along with dynamically determined runtime estimates for helper functions and knowledge of loop-based helpers’ effects on control flow, we generate an accurate—although broad—range estimate for making runtime policy decisions. We further discuss some of the limitations of this approach, particularly in the case of broad estimate ranges as well as complementary tools for BPF runtime management.
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    Kernel extension verification is untenable
    Jia, Jinghao; Sahu, Raj; Oswald, Adam; Williams, Dan; Le, Michael V.; Xu, Tianyin (ACM, 2023-06-22)
    The emergence of verified eBPF bytecode is ushering in a new era of safe kernel extensions. In this paper, we argue that eBPF’s verifier—the source of its safety guarantees—has become a liability. In addition to the well-known bugs and vulnerabilities stemming from the complexity and ad hoc nature of the in-kernel verifier, we highlight a concerning trend in which escape hatches to unsafe kernel functions (in the form of helper functions) are being introduced to bypass verifier-imposed limitations on expressiveness, unfortunately also bypassing its safety guarantees. We propose safe kernel extension frameworks using a balance of not just static but also lightweight runtime techniques. We describe a design centered around kernel extensions in safe Rust that will eliminate the need of the in-kernel verifier, improve expressiveness, allow for reduced escape hatches, and ultimately improve the safety of kernel extensions.
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    Re-thinking termination guarantee of eBPF
    Sahu, Raj (Virginia Tech, 2024-06-10)
    In the rapidly evolving landscape of BPF as kernel extensions, where the industry is deploying an increasing count of simultaneously running BPF programs, the need for accounting BPF- induced overhead on latency-sensitive kernel functions is becoming critical. We also find that eBPF's termination guarantee is insufficient to protect systems from BPF programs running extraordinarily long due to compute-heavy operations and runtime factors such as contention. Operators lack a crucial mechanism to identify and avoid installing long-running BPF programs while also requiring a mechanism to abort such BPF programs when found to be adding high latency overhead on performance-critical kernel functions. In this work, we propose a runtime estimator and a dynamic termination mechanism to solve these two issues, respectively. We use a hybrid of static and dynamic analysis to provide a runtime range that we demonstrate to encompass the actual runtime of the BPF program. For safe BPF termination, we propose a short-circuiting approach to skip all costly operations and quickly reach completion. We evaluate the proposed solutions to find the obtained performance estimate as too broad, but when paired with the dynamic termination, can be used by a BPF Orchestrator to impose policies on the overhead due to BPF programs in a call path. The proposed dynamic termination solution has zero overhead on BPF programs for no-termination cases while having a verification overhead proportional to the number of helper calls in a BPF program. In the future, we aim to make BPF execution atomic to guarantee that kernel objects modified within a BPF program are always left in a consistent state in the event of program termination.
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    Team 3: Object Detection and Topic Modeling (Objects&Topics) CS 5604 F2022
    Devera, Alan; Sahu, Raj; Masrourisaadat, Nila; Amirthalingam, Nirmal; Mao, Chenyu (Virginia Tech, 2023-01-17)
    The CS 5604: Information Storage and Retrieval class (Fall 2022), led by Dr. Edward Fox, has been assigned the task of designing and implementing a state-of-the-art information retrieval and analysis system that will support Electronic Theses & Dissertations (ETDs). Given a large collection of ETDs, we want to run different kinds of learning algorithms to categorize them into logical groups, and by the end, be able to suggest to an end-user the documents which are strongly related to the one they are looking for. The overall goal for the project is to have a service that can upload, search, and retrieve ETDs with their derived digital objects, in a human-readable format. Specifically, our team is tasked with analyzing documents using object detection and topic models, with the final deliverable being the Experimenter web page for the derived objects and topics. The object detection team worked with Faster R-CNN and YOLOv7 models, and implemented post-processing rules for saving objects in a structured format. As the final deliverable for object detection, inference on 5k ETDs has been completed, and the refined objects have been saved to the Repository. The topic modeling team worked with clustering ETDs to 10, 25, 50, and 100 topics with different models (LDA, NeuralLDA, CTM, ProdLDA). As the final deliverable for topic modeling, we store the related topics and related documents for 5k ETDs in the Team 1 database, so that Team 2 could provide the related topic and documents on the documents page. By the end of the semester the team was able to deliver the Experimenter web page for the derived objects and topics, and the related objects and topics for 5k ETDs stored in the Team 1 database.