Pilote informatique | EPFL Graph Search

Un pilote informatique (driver), souvent abrégé en pilote, est un programme informatique destiné à permettre à un autre programme (souvent un système d'exploitation) d'interagir avec un périphérique. En général, chaque périphérique a son propre pilote. Dit de manière simplifiée, un pilote d'imprimante est un logiciel qui traduit les ordres de l'utilisateur (le système) dans le langage de l'imprimante. Sans pilote, l'imprimante ou la carte graphique par exemple ne pourraient pas être utilisées. Un pilote manquant peut être, lors de son besoin, recherché dans et déchargé d'un répertoire du Web pour son installation. Certains systèmes d'exploitation comme Windows proposent leurs propres pilotes génériques censés fonctionner de manière satisfaisante avec la plupart des périphériques pour une utilisation courante. Si ces pilotes gèrent les grandes fonctions communes à tous les matériels, ils n'ont pas toujours toutes les capacités des pilotes de constructeurs, qui seuls connaissent parf

Optimizing network performance in virtual machines

Aravind Menon

In recent years, there has been a rapid growth in the adoption of virtual machine technology in data centers and cluster environments. This trend towards server virtualization is driven by two main factors: the savings in hardware cost that can be achieved through the use of virtualization, and the increased flexibility in the management of hardware resources in a cluster environment. An important consequence of server virtualization is the negative impact it has on the networking performance of server applications running in virtual machines (VMs). In this thesis, we address the problem of efficiently virtualizing the network interface in Type-II virtual machine monitors. In the Type-II architecture, the VMM relies on a special, 'host' operating system to provide the device drivers to access I/O devices, and executes the drivers within the host operating system. Using the Xen VMM as an example of this architecture, we identify fundamental performance bottlenecks in the network virtualization architecture of Type-II VMMs. We show that locating the device drivers in a separate host VM is the primary reason for performance degradation in Type-II VMMs, because of two reasons: a) the switching between the guest and the host VM for device driver invocation, and, b) I/O virtualization operations required to transfer packets between the guest and the host address spaces. We present a detailed analysis of the virtualization overheads in the Type-II I/O architecture, and we present three solutions which explore the performance that can be achieved while performing network virtualization at three different levels: in the host OS, in the VMM, and in the NIC hardware. Our first solution consists of a set of packet aggregation optimizations that explores the performance achievable while retaining the Type-II I/O architecture in the Xen VMM. This solution retains the core functionality of I/O virtualization, including device driver execution, in the Xen 'driver domain'. With this set of optimizations, we achieve an improvement by a factor of two to four in the networking performance of Xen guest domains. In our second solution, we move the task of I/O virtualization and device driver execution from the host OS to the Xen hypervisor. We propose a new I/O virtualization architecture, called the TwinDrivers framework, which combines the performance advantages of Type-I VMMs with the safety and software engineering benefits of Type-II VMMs. (In a Type-I VMM, the device driver executes directly in the hypervisor, and gives much better performance than a Type-II VMM). The TwinDrivers architecture results in another factor of two improvements in networking performance for Xen guest domains. Finally, in our third solution, we describe a hardware based approach to network virtualization, in which we move the task of network virtualization into the network interface card (NIC). We develop a specialized network interface (CDNA) which allows guest operating systems running in VMs to directly access a private, virtual context on the NIC for network I/O, bypassing the host OS entirely. This approach also yields performance benefits similar to the TwinDrivers software-only approach. Overall, our solutions help significantly bridge the gap between the network performance in a virtualized environment and a native environment, eventually achieving network performance in a virtual machine within 70% of the native performance.

EPFL2009

USBFuzz: A Framework for Fuzzing USB Drivers by Device Emulation

Mathias Josef Payer, Hui Peng

The Universal Serial Bus (USB) connects external devices to a host. This interface exposes the OS kernels and device drivers to attacks by malicious devices. Unfortunately, kernels and drivers were developed under a security model that implicitly trusts connected devices. Drivers expect faulty hardware but not malicious attacks. Similarly, security testing drivers is challenging as input must cross the hardware/software barrier. Fuzzing, the most widely used bug finding technique, relies on providing random data to programs. However, fuzzing device drivers is challenging due to the difficulty in crossing the hardware/software barrier and providing random device data to the driver under test. We present USBFuzz, a portable, flexible, and modular framework for fuzz testing USB drivers. At its core, USBFuzz uses a software-emulated USB device to provide random device data to drivers (when they perform IO operations). As the emulated USB device works at the device level, porting it to other platforms is straight-forward. Using the USBFuzz framework, we apply (i) coverage-guided fuzzing to a broad range of USB drivers in the Linux kernel; (ii) dumb fuzzing in FreeBSD, MacOS, and Windows through cross-pollination seeded by the Linux inputs; and (iii) focused fuzzing of a USB webcam driver. USBFuzz discovered a total of 26 new bugs, including 16 memory bugs of high security impact in various Linux subsystems (USB core, USB sound, and network), one bug in FreeBSD, three in MacOS (two resulting in an unplanned reboot and one freezing the system), and four in Windows 8 and Windows 10 (resulting in Blue Screens of Death), and one bug in the Linux USB host controller driver and another one in a USB camera driver. From the Linux bugs, we have fixed and upstreamed 11 bugs and received 10 CVEs.

USENIX ASSOC2020

Virtual metrology applied to milling process

Paul Arthur Adrien Pierre Dreyfus

Production quality and process efficiency are the two main drivers that lead any industrial strategy. To ensure product quality, a duality historically existed between two approaches, namely batch sampling and systematic sampling. In batch sampling, the batch homogeneity is assumed, and a subset is measured, whereas, in systematic sampling, every part of the batch is measured independently. The latter approach is too expensive to be considered. Therefore, batch sampling is implemented, which, however, involves sacrifices product quality, as the homogeneity assumption cannot always be true. Today, virtual metrology (VM) is on the brink of enabling a new standard for quality control by offering a third approach that combines the benefits of the others. VM estimates product quality while preserving process efficiency. It enables continuous systematic monitoring of production in hidden time. To do so, it leverages process data and relates them to product quality through machine learning algorithms. This thesis proposes a proof of concept and guidelines on how to design, tune, implement, and maintain a VM solution for one of the most common industrial operations, namely milling.The literature lacked a comprehensive summary and a systematic review of the state of the art in VM. This motivated the realization of a systematic, complete, structured literature review of VM based on a content analysis of all research articles in the field published before 2021. The papers are classified thanks to a new framework highlighting shortcomings and future research directions. Finally, VM's use in various industrial fields is discussed, underlining its potential for every manufacturing industry. Two of the various findings of this literature review are the lack of development of VM for machine tool operations and the lack of research on the maintenance of data-based models to ensure their long-term performance. These two research gaps are addressed in the present thesis.Thereafter, a significant step toward VM for milling operations is made, with a specific focus on the estimation of the dimensional quality of single-pass milled parts. To do so, two experiments were conducted in an industrial environment. Various combinations of recorded process variables, data synchronization algorithms, dimensionality reduction algorithms, and regression algorithms were tested to maximize model accuracy. A new baseline for dimensional quality estimation in an industrial production environment is set with a mean absolute error of 14.4 µm. Besides the proof of concept, this part of the present thesis provides directions on how to design and tune a VM algorithm for milling operations.Finally, a methodology is proposed for implementing a problem-oriented complete solution to ensure the maintenance of industrial data-based models. This solution is structured based on an operational framework, including a sampling decision system and an updating system. Each methodology step is described thanks to guidelines, while research gaps are highlighted. The methodology starts with a concept drift identification phase; thereafter, solutions are pre-selected based on the identified concept drifts. An optimization problem is then designed to select the solution that most respects costs and constraints. This section of the present thesis provides a methodology to implement a solution for the maintenance of industrial data-based models such as VM.

EPFL2022