Désassembleur | EPFL Graph Search

A disassembler is a computer program that translates machine language into assembly language—the inverse operation to that of an assembler. Disassembly, the output of a disassembler, is often formatted for human-readability rather than suitability for input to an assembler, making it principally a reverse-engineering tool. Common uses of disassemblers include analyzing high-level programing language compilers output and their optimizations, recovering source code of a program whose original source was lost, malware analysis, modifying software (such as ROM hacking), and software cracking. A disassembler differs from a decompiler, which targets a high-level language rather than an assembly language. Assembly language source code generally permits the use of constants and programmer comments. These are usually removed from the assembled machine code by the assembler. If so, a disassembler operating on the machine code would produce disassembly lacking these constants and comments; the disassembled output becomes more difficult for a human to interpret than the original annotated source code. Some disassemblers provide a built-in code commenting feature where the generated output gets enriched with comments regarding called API functions or parameters of called functions. Some disassemblers make use of the symbolic debugging information present in object files such as ELF. For example, IDA allows the human user to make up mnemonic symbols for values or regions of code in an interactive session: human insight applied to the disassembly process often parallels human creativity in the code writing process. Writing a disassembler which produces code which, when assembled, produces exactly the original binary is possible; however, there are often differences. This poses demands on the expressivity of the assembler. For example, an x86 assembler takes an arbitrary choice between two binary codes for something as simple as MOV AX,BX. If the original code uses the other choice, the original code simply cannot be reproduced at any given point in time.

Disassembly scheduling

Hwa-Joong Kim

This dissertation focuses on disassembly scheduling, which is the problem of determining the quantity and timing of disassembling used or end-of-life products while satisfying the demand of their parts/components over a given planning horizon. The objective is to minimize the sum of purchase, setup, disassembly operation, and inventory holding costs. In general, disassembly scheduling is one of the important mid-term (or short-term) planning problems in disassembly systems. In contrast to assembly, disassembly systems have the special characteristic that a product diverges into multiple demand sources of parts/components. This makes the disassembly scheduling problem more complex than the ordinary production planning problems in assembly systems. We consider two versions of disassembly scheduling: the uncapacitated and capacitated version. For the uncapacitated version of the problem, three cases are considered: the two-level disassembly; the multi-level disassembly; and the multiple product types with parts commonality structures. The two-level disassembly structure describes the direct relationship between the product and its parts/components without intermediate subassemblies. Parts commonality implies that products or subassemblies share their parts and/or components. For the capacitated version of the problem, the case with single product type without parts commonality is considered. In the first part of this dissertation, we consider the case with the two-level disassembly structure. We propose a dynamic programming model after characterizing the properties of optimal solutions. Based on the dynamic programming model, an exact algorithm is proposed by which the optimal solutions can be obtained in polynomial time. The second part considers the case with the multi-level disassembly structure. An integer programming model is proposed to represent and optimally solve the case of single product type without parts commonality. Then, the model is extended to consider single and multiple product types with parts commonality. The results of computational experiments show that the proposed integer programming approach works well. The case with multiple product types and parts commonality is considered in the third part. A two-phase heuristic is proposed in which an initial solution is obtained using a linear programming relaxation, and then improved by perturbing the initial solution using a dynamic programming algorithm with look-ahead check, together with methods of generating new solutions and checking their feasibilities. The results of computational experiments show that the proposed heuristic can give good solutions within short computation time. We consider in the last part the resource capacity restrictions over the planning horizon, which makes the problem more realistic. To solve the problem, a heuristic is developed using a Lagrangean relaxation technique together with a method to find a good feasible solution while considering the trade-offs among different costs. The results of computational experiments show that the proposed heuristic can give near optimal solutions within a short amount of computation time.

EPFL2005

Disassembly scheduling

Hwa-Joong Kim

EPFL2005