ISGEN: A Byte Stream lnstruction Set Generator

Avaliação de Confiança Contextual em Grades Computacionais Multímodo usando Plataformas Seguras

F.D. L. ArciJ. P. Bennett

Ricardo de Barros CostaLuiz Fernando Rust da Costa Carmo

Various methodologies have been devised for the design of byte stream instruction sets (Tan78, SS82). The second author has proposed an opproach that is largely automatic (Ben88). A set of lnstructions is derived that is optimal occording to some criterion, such as the size of compiled code. The choice of instructions is driven by statisticol analysis of a large amount of high level language code intended for the instruction set under design. We describe a computer program which will produce such on instructlon set. The system hos been successtully used to produce bytestream instruction sets to support BCPL (RWS80), Poly(Mat85) and Eulisp (PN+90). We present quantitative results showing the success of these designs. Byte stream instruction sets are now largely restricted to interpretive intermediate codes, with the majority of linstructlon sets being RISC, or derived designs. We outline current work to produce ISGEN-GA which will generalise the methodology, so that RISC type instruction sets can be produced automotically. This paper investigates the joint use of secure platform (TPM), virtualization techniques and trust evaluation techniques in a GRID, for protecting its owns resources and users' applications. Grid is formatted within different operation modes, which one presenting a different protection level in function of its predefined security mechanisms. The operation mode of each application is selected according to the contextual trust exhibited by the user at submission time. Trust calculation is based on four different factors: identification process, platform robustness, communication mode and user's reputation. Simulations results provide subsidies for correlating operation mode and trust thresholds, aiming to optimize the Grid performance.

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