Approved for public release, distribution is unlimited / A dynamic subversion attack on the Windows XP Embedded operating system is demonstrated to raise awareness in developers and consumers of the risk of subversion in commercial operating systems that may be safety critical. SCADA (Supervisory Control and Data Acquisition) systems that monitor and control our critical infrastructure depend on embedded systems. The attack can be loaded onto a fielded system that has been subverted with a small software artifice. The artifice could be inserted into the system at any time in the system's lifecycle. The attack provides a flexible method for the attacker, who may not be the same individual who inserted the artifice, to gain total control of the subverted system. Due to the dynamic loading property of this subversion, the attacker does not have to decide the aspect of the system to be targeted until a time of her choice. The attack does not exploit an existing flaw in the target module but is possible because the initial artifice is inserted into the kernel of an operating system where adversaries have access to source code. This thesis discusses certain aspects of known methods for developing systems free from subversion. Several projects that utilized these methods are presented. / Civilian, Naval Postgraduate School

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ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / Recent emphasis has been placed on mobile robotics performing in unstructured environments. This realm of operations requires many different algorithms to interpret the various situations. This not only requires a system that is able to support, and facilitate, the fusion of the results, but it also needs to be tolerant of system errors. In modern operating systems, separate processes are able to fail without affecting other processes. Using this ability, along with fault tolerant inter-process communications, and supervisory process managers, allows the total system to continue to operate under adverse conditions. While this paper focuses primarily on the challenges faced by mobile robotics, the approach can be extended to a wide range of systems which must autonomously identify and adapt to failures/situations.

Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Users are not supposed to modify an operating system kernel, but it is often necessary to add a device driver for a new peripheral device. Device driver development is a difficult and time-consuming process that must be performed by an expert. Drivers are difficult to debug and a malfunctioning driver could cause the operating system to crash. Ways are therefore needed to make the development of device drivers safer and easier. A number of different device driver development methods are examined in this thesis. An existing micro-kernel that supports in-kernel device drivers as well as extensible device drivers has been modified to support user-level and loadable drivers. These extensions ensured that all the development methods were implemented in the same environment and a comparison could thus be made on a fair basis. A comparison of the different methods with respect to the efficiency of the resulting device driver, as well as the ease of the development process, is presented. / AFRIKAANSE OPSOMMING: Gebruikers is nie veronderstelom aan 'n bedryfstelsel te verander nie, maar tog is dit gereeld nodig om 'n toesteldrywer vir 'n nuwe randapparaat by te voeg. Die ontwikkeling van 'n toesteldrywer is 'n tydrowende en moeilike proses en moet deur 'n kundige aangepak word. Toesteldrywers is moeilik om te ontfout en kan deur verkeerde werking die hele stelsel tot stilstand bring. Daar is dus tegnieke nodig om die ontwikkeling van toestelhanteerders makliker en veiliger te maak. 'n Aantal verskillende ontwikkelingsmetodes vir toesteldrywers word in hierdie tesis ondersoek. 'n Bestaande mikro-kern wat in-kern, sowel as uitbreibare toesteldrywers ondersteun, is aangepas om gebruikersvlak en laaibare toestelhanteerders te ondersteun. Hierdie uitbreiding het verseker dat al die ontwikkelingsmetodes in dieselfde omgewing geïmplementeer is. Dit was dus moontlik om die metodes op 'n regverdige grondslag te vergelyk. Die vergelyking is gedoen ten opsigte van die effektiwiteit van die resulterende toesteldrywer sowel as die moeilikheidsgraad van die ontwikkelingsproses.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / This paper illustrates a device driver implementation used to support a PC compatible telemetry device. Device requirements included operation on Windows NT 4.0, Windows 95, Windows NT 5.0 and Windows 98 platforms. A single device driver was not possible due to the differences between driver requirements on the various operating systems. The Windows Driver Model (WDM) was considered for NT 5.0 and Win98, however, NT 4.0 and Win95 does not support the WDM. To minimize software development and support efforts, it was clear that an architecture compatible to both WDM, NT 4.0 and Windows 95 needed to be developed. The resulting layered device driver architecture provides a common upper interface and uses a register based model to describe the hardware at the lower interface. The common upper interface is compatible with all of the target operating systems and presents a consistent Applications Programming Interface (API) for the telemetry application developer. The lower interface is specific for each platform but contains minimal device specific functionality. A simple register I/O driver is easily implemented using all of the target operating systems. The layered architecture and register based interface to the hardware results in a multiple operating system code set which differs only at the lowest layer.

International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In this paper we present the REAL/STONE Real-Time Tester, a tool for performance evaluation of real-time UNIX operating systems. The REAL/STONE Real-Time Tester is a synthetic benchmark that simulates a typical real-time environment. The tool performs typical real-time operations, such as: (a) reads data from an external source and accesses it periodically, (b) processes data through a number of real-time processes, and © displays the final data. This study can help users in selecting the most-effective real-time UNIX operating system for a given application.

This dissertation describes the design and implementation of the file system component of the Saguaro operating system for computers connected by a local-area network. Systems constructed on such an architecture have the potential advantage of increased file availability due to their inherent redundancy. In Saguaro, this advantage is made available through two mechanisms that support semi-automatic file replication and access: reproduction sets and metafiles. A reproduction set is a collection of files that the system attempts to keep identical on a "best effort" basis, relying on the user to handle unusual situations that may arise. A metafile is a special file that contains symbolic path names of other files; when a metafile is opened, the system selects an available constituent file and opens it instead. These mechanisms are especially appropriate for situations that do not require guaranteed consistency or a large number of copies. Other interesting aspects of the Saguaro file system design are also described. The logical file system forms a single tree, yet any file can be placed in any of the physical file systems. This organization allows the creation of a logical association among files that is quite different from their physical association. In addition, the broken path algorithm is described. This algorithm makes it possible to bypass elements in a path name that are on inaccessible physical file systems. Thus, any accessible file can be made available, regardless of the availability of directories in its path. Details are provided on the implementation of the Saguaro file system. The servers of which the system is composed are described individually and a comprehensive operational example is supplied to illustrate their interation. The underlying data structures of the file system are presented. The virtual roots, which contain information used by the broken path algorithm, are the most novel of these. Finally, an implementation of reproduction sets and metafiles for interconnected networks running Berkeley UNIX is described. This implementation demonstrates the broad applicability of these mechanisms. It also provides insight into the way in which mechanisms to facilitate user controlled replication of files can be inexpensively added to existing file systems. Performance measurements for this implementation are also presented.

As the complexity of embedded systems grows, there is an increasing use of operating systems (OSes) in embedded devices, such as mobile phones, media players and other consumer electronics. Despite their convenience and flexibility, such operating systems can be overly general and contain features and code that are not needed in every application context, which incurs unnecessary performance overheads. In most embedded systems, resources, such as processing power, available memory, and power consumption, are strictly constrained. In particular, the amount of memory on embedded devices is often very limited. This, together with the popular usage of operating systems in embedded devices, makes it important to reduce the memory footprint of operating systems. This dissertation addresses this challenge and presents automated ways to reduce the memory footprint of OS kernels for embedded systems. First, we present kernel code compaction, an automated approach that reduces the code size of an OS kernel statically by removing unused functionality. OS kernel code tends to be different from ordinary application code, including the presence of a significant amount of hand-written assembly code, multiple entry points, implicit control flow paths involving interrupt handlers, and frequent indirect control flow via function pointers. We use a novel "approximated compilation" technique to apply source-level pointer analysis to hand-written assembly code. A prototype implementation of our idea on an Intel x86 platform and a minimally configured Linux kernel obtains a code size reduction of close to 24%.Even though code compaction can remove a portion of the entire OS kernel code, when exercised with typical embedded benchmarks, such as MiBench, most kernel code is executed infrequently if at all. Our second contribution is on-demand code loading, an automated approach that keeps the rarely used code on secondary storage and loads it into main memory only when it is needed. In order to minimize the overhead of code loading, a greedy node-coalescing algorithm is proposed to group closely related code together. The experimental results show that this approach can reduce memory requirements for the Linux kernel code by about 53%with little degradation in performance. Last, we describe dynamic data structure compression, an approach that reduces the runtime memory footprint of dynamic data structures in an OS kernel. A prototype implementation for the Linux kernel reduces the memory consumption of the slab allocators in Linux by 17.5%when running the MediaBench suite while incurring only minimal increases in execution time (1.9%).

The goal of this master thesis is to extend HelenOS operating system with the support for ccNUMA hardware. The text of the thesis contains a brief introduction to ccNUMA hardware, an overview of NUMA features and relevant features of HelenOS (memory management, scheduling, etc.). The thesis analyses various design decisions of the implementation of NUMA support -- introducing the hardware topology into the kernel data structures, propagating this information to user space, thread affinity to cores and nodes, memory allocation policies, load balancing, etc. The thesis also contains a prototype implementation of ccNUMA support in HelenOS for the AMD64 platform and a brief evaluation and comparison with ccNUMA support in other monolithic and microkernel-based operating systems.