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김지홍(Jeehong Kim),김인혁(Inhyuk Kim),엄영익(Young Ik Eom) 한국정보과학회 2011 한국정보과학회 학술발표논문집 Vol.38 No.1A
Dalvik 가상 머신은 최적화가 쉽지 않았던 스택 기반의 가상 머신인 자바 가상 머신(JVM)과 달리 레지스터 기반의 가상 머신이므로 여러 최적화 기법을 적용할 수 있다. 따라서 Dalvik 가상 머신을 위한 새로운 레지스터 할당기법이 필요하다. 본 논문에서는 dx tool을 거친 레지스터 기반의 Dalvik byte code를 레지스터 재 할당하여 최적화하고, 이를 Dalvik JIT으로 보내어 다시 한번 레지스터 재할당 함으로써 최적화 효율을 높일 수 있는 최적화 기법을 제안하였다. 또한 제안 기법과 Dalvik JIT의 복잡도를 비교함으로써 제안기법을 검증하였다.
가변형 단일 궤도를 이용한 장애물 극복방법에 관한 연구
김지홍(Jeehong Kim),이창구(Chang-Goo Lee) 제어로봇시스템학회 2010 제어·로봇·시스템학회 논문지 Vol.16 No.4
In our paper, we propose an asymmetric single-tracked wheel system, and describe its structure and the method for maintaining the length of a transformable track system. And the method is reducing the gap of lengths. Therefore, we propose an efficient structure for transforming and explain motions with kinematics. Our transformable shape single-tracked mobile system has an advantage to overcome an obstacle or stairs by the variable arms in the single unity track system. But we will make the variable shape of tracked system get a drive that has a force to stand against a wall. In this case, we can consider this system to a rigid body and have a notice that this single tracked system is able to get vary shape with the variable arm angle. Considering forces balance along x-axis and y-axis, and moments balance around the center of the mass we have. If this rigid body is standing against a wall and doesn’t put in motion, the force of flat ground and the rigid body sets an equal by a friction. In the same way, the force of a wall and the rigid sets an equal by a friction.
볼록 거울 및 단일 카메라를 이용한 실내에서의 전 방향 위치 검출 방법
김지홍(Jeehong Kim),김희선(Heesun Kim),이창구(Changgoo Lee) 제어로봇시스템학회 2008 제어·로봇·시스템학회 논문지 Vol.14 No.2
This article describes the methods of a decision of the location which user points to move by an optical device like a laser pointer and a moving to that location. Using a conic mirror and CCD camera sensor, a robot observes a spot of user wanted point among an initiative, computes the location and azimuth and moves to that position. This system offers the brief data to a processor with simple devices. In these reason, we can reduce the time of a calculation to process of images and find the target by user point for carrying a robot. User points a laser spot on a point to be moved so that this sensor system in the robot, detecting the laser spot point with a conic mirror, laid on the robot, showing a camera. The camera is attached on the robot upper body and fixed parallel to the ground and the conic mirror.
김지홍 ( Jeehong Kim ),엄영익 ( Young Ik Eom ) 한국정보처리학회 2013 한국정보처리학회 학술대회논문집 Vol.20 No.1
멀티코어 환경이 보편화됨에 따라 병렬프로그래밍 기법과 이에 대한 컴파일 기술의 중요성이 더해지고 있다. 하지만 각 병렬 프로그래밍 기법과 컴퓨팅 환경에 따라 컴파일 기술이 개발되어야 하는 단점이 있다. 따라서 본 논문에서는 다양한 병렬 프로그래밍 기법과 컴퓨팅 환경을 지원할 수 있는 범용 컴파일러의 개발을 위해 병렬프로그래밍 기법과 컴파일러에 따른 병렬 프로그램의 컴파일 성능을 비교하고, 높은 수행 성능을 가진 범용 병렬 프로그램 컴파일러의 설계 방안을 모색한다.
반환 지향 프로그래밍 공격에 대한 효율적인 방어 기법 설계 및 구현
김지홍(Jeehong Kim),김인혁(Inhyeok Kim),민창우(Changwoo Min),엄영익(Young Ik Eom) Korean Institute of Information Scientists and Eng 2014 정보과학회논문지 Vol.41 No.12
An ROP attack creates gadget sequences which consist of existing code snippets in a program, and hijacks the control flow of a program by chaining and executing gadget sequences consecutively. Existing defense schemes have limitations in that they cause high execution overhead, an increase in the binary size overhead, and a low applicability. In this paper, we solve these problems by introducing zero-sum defender, which is a fast and space-efficient mitigation scheme against ROP attacks. We find a fundamental property of gadget execution in which control flow starts in the middle of a function without a call instruction and ends with a return instruction. So, we exploit this property by monitoring whether the execution is abused by ROP attacks. We achieve a very low runtime overhead with a very small increase in the binary size. In our experimental results, we verified that our defense scheme prevents real world ROP attacks, and we showed that there is only a 2% performance overhead and a 1% binary size increase overhead in several benchmarks.
경량 동적 코드 변환 기법을 이용한 동적 인스트루멘테이션 기법 설계 및 구현
김지홍(Jeehong Kim),이동우(Dongwoo Lee),김인혁(Inhyeok Kim),엄영익(Young Ik Eom) Korean Institute of Information Scientists and Eng 2014 정보과학회논문지 Vol.41 No.11
Dynamic binary instrumentation is a code insertion technique for debugging a program without scattering its execution flow, while the program is running. Most dynamic instrumentations are implemented using dynamic binary translation techniques. Existing studies translated program codes dynamically by parsing the machine code stream to intermediate representation (IR) and then applying compilation techniques for IRs. However, they have high overhead during translation, which is a major cause of difficulty in applying the dynamic binary translation technique to the program which requires high responsiveness. In this paper, we introduce a light-weight dynamic binary instrumentation framework based on a novel dynamic binary translation technique which has low overhead while translating the program code. In order to reduce the translation overhead, our approach adopts a tabular-based address translation and exploits a translation bypassing scheme, which stores the translated address of a frequently called library function in advance. It then accesses the translated address and executes function codes without code translation when calling the function. Our experiment results demonstrated that the proposed approach outperforms the prior dynamic binary translation techniques from 2% up to 65%.