Testing embedded software in a simulated environment

Abstract. In this master’s thesis, a simulation environment that can be used to execute embedded software’s unit tests is implemented. The purpose of the simulation is to make the development of the embedded firmware easier, cheaper, and faster. Also, the purpose is to make remote work easier by enabling unit test and integration test execution on a laptop. This topic has been researched a lot before and many different solutions and tools exist for embedded system simulation. Some of these solutions are introduced in this paper. After the introduction, two of the solutions are implemented for one embedded system that uses monolithic firmware. The solutions implemented are emulation based on the Unicorn emulator and a simulation with native execution on a PC. Each solution has advantages and disadvantages. But in this case, the native execution on a PC was better, as the test execution was two times faster than in Unicorn emulator and three times faster than in an embedded device. Native execution was also easier to implement than Unicorn emulator and could use free compilers like GCC and Clang. The biggest disadvantage with native execution was the low fidelity.Sulautetun ohjelmiston testaaminen simuloidussa ympäristössä. Tiivistelmä. Tässä diplomityössä tehdään simulointiympäristö, jolla voidaan ajaa sulautetun järjestelmän yksikkö- ja integraatiotestejä. Simulaation tarkoitus on tehdä sulautetun järjestelmän ohjelmistokehitys helpommaksi, halvemmaksi ja nopeammaksi. Lisäksi simulaatiolla saadaan tehtyä etätyöskentely helpommaksi, kun yksikkö- ja integraatiotestit voidaan ajaa kannettavalla tietokoneella. Sulautetun järjestelmän simulointia on tutkittu paljon ja simulointiin on kehitetty monia eri ratkaisuja ja työkaluja. Osa näistä työkaluista esitellään tässä diplomityössä. Esittelyn jälkeen toteutetaan kaksi eri simulointi ympäristöä yhdelle sulautetulle järjestelmälle. Toteutetut simulaatiot ovat: emulaatio joka tehdään Unicorn emulaattorilla ja simulaatio joka toteutetaan natiiviajona PC:llä. Molemmilla ratkaisuilla on hyvät ja huonot puolet. Mutta kokonaisuutena natiiviajo oli parempi tälle sulautetulle järjestelmälle, koska natiiviajo oli kaksi kertaa nopeampi kuin Unicorn emulaattori ja kolme kertaa nopeampi kuin sulautettu järjestelmä. Lisäksi natiiviajo oli helpompi toteuttaa kuin Unicorn emulaattori ja natiiviajossa voitiin käytettään ilmaisia kääntäjiä kuten GCC ja Clang. Huonoin puoli natiiviajossa oli se, että natiiviajon tarkkuus ei ollut kovin hyvä, eikä sillä näin ollen pystynyt testaamaan kaikkia asioita koodista

Representing numeric data in 32 bits while preserving 64-bit precision

Data files often consist of numbers having only a few significant decimal digits, whose information content would allow storage in only 32 bits. However, we may require that arithmetic operations involving these numbers be done with 64-bit floating-point precision, which precludes simply representing the data as 32-bit floating-point values. Decimal floating point gives a compact and exact representation, but requires conversion with a slow division operation before it can be used. Here, I show that interesting subsets of 64-bit floating-point values can be compactly and exactly represented by the 32 bits consisting of the sign, exponent, and high-order part of the mantissa, with the lower-order 32 bits of the mantissa filled in by table lookup, indexed by bits from the part of the mantissa retained, and possibly from the exponent. For example, decimal data with 4 or fewer digits to the left of the decimal point and 2 or fewer digits to the right of the decimal point can be represented in this way using the lower-order 5 bits of the retained part of the mantissa as the index. Data consisting of 6 decimal digits with the decimal point in any of the 7 positions before or after one of the digits can also be represented this way, and decoded using 19 bits from the mantissa and exponent as the index. Encoding with such a scheme is a simple copy of half the 64-bit value, followed if necessary by verification that the value can be represented, by checking that it decodes correctly. Decoding requires only extraction of index bits and a table lookup. Lookup in a small table will usually reference cache; even with larger tables, decoding is still faster than conversion from decimal floating point with a division operation. I discuss how such schemes perform on recent computer systems, and how they might be used to automatically compress large arrays in interpretive languages such as R

Retrofitting Security in COTS Software with Binary Rewriting

We present a practical tool for inserting security features against low-level software attacks into third-party, proprietary or otherwise binary-only software. We are motivated by the inability of software users to select and use low-overhead protection schemes when source code is unavailable to them, by the lack of information as to what (if any) security mechanisms software producers have used in their toolchains, and the high overhead and inaccuracy of solutions that treat software as a black box. Our approach is based on SecondWrite, an advanced binary rewriter that operates without need for debugging information or other assist. Using SecondWrite, we insert a variety of defenses into program binaries. Although the defenses are generally well known, they have not generally been used together because they are implemented by different (non-integrated) tools. We are also the first to demonstrate the use of such mechanisms in the absence of source code availability. We experimentally evaluate the effectiveness and performance impact of our approach. We show that it stops all variants of low-level software attacks at a very low performance overhead, without impacting original program functionality

PeRISCVcope: a tiny teaching-oriented RISC-V interpreter

The fast advances of computer systems translate into a growing demand of methodologies and tools to introduce those novelties into classes. Among the plethora of those advances, virtualization has become an essential technology in almost every relevant system stack, from connected cars to hyperscaled cloud servers. However, introducing those technologies into the classroom remains a challenging task because of the huge complexity of their software components that may hinder the learning process of students. peRISCVcope aims to help in this area by proposing a tiny yet powerful interpreter to dig into virtualization technologies, such as the implementation of trap&emulate hypervisors. With less than 2,000 lines of code, and thanks to the conciseness of the RV32I base instruction set of RISC-V, peRISCVcope enables students to make virtualization knowledge their own. This paper presents our experiences developing and testing a virtualization laboratory where students implement parts of an interpreter. After the practical experience, peRISCVcope has been proved as a useful pedagogical tool, and, most importantly, students have positively rated the experience