Embedded C

Abstract: Traditional approaches to enforcing memory safety of programs rely heavily on runtime checks of memory accesses and on garbage collection, both of which are unattractive for embedded applications. The long-term goal of our work is to enable 100% static enforcement of memory safety for embedded programs through advanced compiler techniques and minimal semantic restrictions on programs. The key result of this paper is a compiler technique that ensures memory safety of dynamically allocated memory without programmer annotations, runtime checks, or garbage collection, and works for a large subclass of type-safe C programs. The technique is based on a fully automatic pool allocation (i.e., region-inference) algorithm for C programs we developed previously, and it ensures safety of dynamically allocated memory while retaining explicit deallocation of individual objects within regions (to avoid garbage collection). For a diverse set of embedded C programs (and using a previous technique to avoid null pointer checks), we show that we are able to statically ensure the safety of pointer and dynamic memory usage in all these programs. We also describe some improvements over our previous work in static checking of array accesses. Overall, we achieve 100% static enforcement of memory safety without new language syntax for a significant subclass of embedded C programs, and the subclass is much broader if array bounds checks are ignored. Overall, these techniques greatly expand the class of embedded programs for which 100% static enforcement of memory safety is possible, and furthermore can be achieved without new language support.

Abstract: Managing power concerns in icroprocessors has become a pressing research problem across the domains of computer architecture, CAD, and compilers. As a result, several parameterized cycle-level power simulators have been introduced. While these simulators can be quite useful for microarchitectural studies, their generality limits how accurate they can be for any one chip family. Furthermore, their hardware focus means that they do not explicitly enable studying the interaction of different software layers, such as Java applications and their underlying Runtime system software.This paper describes and evaluates XTREM, a power simulation tool tailored for the Intel XScale icroarchitecture. In building XTREM, our goals were to develop a icroarchitecture simulator that, while still offering size parameterizations for cache, TLB, etc., more accurately reflected a realistic processor pipeline. We present a detailed set of validations based on ultimeter power measurements and hardware performance counter sampling. Based on these validations across a wide range of stressmarks, Java benchmarks, and non-Java benchmarks, XTREM has an average performance error of only 6.5% and an even smaller average power error: 4%. The paper goes on to present a selection of application studies enabled by the simulator. For example, presenting power behavior vs. time for selected embedded C and Java CLDC benchmarks, we can make power distinctions between the two programming domains as well as distinguishing Java application (JITted code) power from Java Runtime system power. We also study how the Intel XScale core 's power consumption varies for different data activity factors, creating power swings as large as 50mW for a 200Mhz core. We are planning to release XTREM for wider use, and feel that it offers a useful step forward for compiler and embedded software designers.

Abstract: This paper presents a low-cost digital single-phase power-quality measurement device for consumer use with a wide range of features, including series arc-fault detection, load trip on failure, and phase/neutral line wiring mix up indication. A wavelet multiresolution analysis technique was utilized for the voltage transient event detection and the current drop pattern recognition, specifically to arc fault. The last feature also involved the use of adaptive thresholding, peak detection, and repetition frequency calculation. A computationally efficient and accurate Goertzel filter was used for total harmonic distortion calculation. In addition, this meter can measure phase fundamental frequency (using the zero-crossing technique), rms values, and power. MATLAB and MathCAD packages were used to build and simulate arc-fault model and phase voltage distortion, to design and test part of the developed algorithms, which were further implemented in Embedded C and Assembler programming languages. A prototype circuit board with the required sensors and relay, analog isolation, indication, user controls, communication link, and a low-cost microchip microcontroller (MCU) dsPIC33 was designed and built to validate implemented algorithms and conduct experiments.

Abstract: We propose a memory abstraction able to lift existing numerical static analyses to C programs containing union types, pointer casts, and arbitrary pointer arithmetics. Our framework is that of a combined points-to and data-value analysis. We abstract the contents of compound variables in a field-sensitive way, whether these fields contain numeric or pointer values, and use stock numerical abstract domains to find an overapproximation of all possible memory states--with the ability to discover relationships between variables. A main novelty of our approach is the dynamic mapping scheme we use to associate a flat collection of abstract cells of scalar type to the set of accessed memory locations, while taking care of byte-level aliases - i.e., C variables with incompatible types allocated in overlapping memory locations. We do not rely on static type information which can be misleading in C programs as it does not account for all the uses a memory zone may be put to. Our work was incorporated within the Astr\'{e}e static analyzer that checks for the absence of run-time-errors in embedded, safety-critical, numerical-intensive software. It replaces the former memory domain limited to well-typed, union-free, pointer-cast free data-structures. Early results demonstrate that this abstraction allows analyzing a larger class of C programs, without much cost overhead.