Pintos Project 2 final report - User Program, System Call

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• 1. Process termination message

  프로세스가 종료될 때마다 프로세스 종료 메시지를 출력해야 한다. 종료 메시지의 출력 예시와 형식은 printf('%s: exit(%d) ', variable_1, variable_2)와 같다. variable_1은 프로세스의 이름이고, variable_2는 exit 코드이다.

• 2. Argument passing

  사용자가 입력한 명령어는 프로그램 이름과 함께 다양한 옵션들이 붙는데, 이를 모두 인식할 수 있도록 구현해야 한다. 현재 Pintos는 전체 명령어를 하나의 프로그램 이름으로 인식하므로, 프로그램 이름과 옵션들을 구분하여 인식하도록 수정한다.

• 3. System calls for user process

  OS는 외부 인터럽트(타이머 인터럽트, 키보드 입력 등)와 내부 인터럽트(0으로 나누기, 페이지 폴트 등)를 처리할 수 있어야 한다. 이를 위해 system call을 구현해야 한다. 주요 system call에는 halt, exit, exec, wait 등이 있다.

• 4. System calls for file manipulation

  파일 디스크립터(fd)를 사용하여 특정 파일에 접근할 수 있도록 구현한다. 파일 디스크립터 테이블을 관리하며, open, close, read, write 등의 system call을 구현한다.

• 5. Denying writes

  실행 파일(executable file)에 대해서는 쓰기를 거부해야 한다. 파일 이름이 현재 스레드의 이름과 같은 경우 해당 파일은 실행 파일로 간주하고 쓰기를 거부한다.

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• 1. Process termination message

  Process termination messages are an important aspect of operating system design, as they provide critical information about the state and outcome of a process. These messages can help developers and system administrators understand why a process terminated, whether it was due to a normal exit, an error condition, or a signal from the operating system. Providing clear and informative termination messages can greatly improve the debugging and troubleshooting process, as it allows for better identification of the root cause of the issue. Additionally, well-designed termination messages can help end-users understand what happened and potentially take appropriate actions. Overall, the implementation of robust and informative process termination messages is a crucial component of a well-designed operating system.

• 2. Argument passing

  Argument passing is a fundamental concept in computer programming, as it allows functions and processes to receive and operate on data provided by the caller. In the context of operating systems, argument passing is particularly important for system calls, where user-level processes need to communicate parameters and data to the kernel. The design of the argument passing mechanism can have a significant impact on the overall performance and efficiency of the system. Factors such as the number and size of arguments, the method of passing (e.g., stack-based, register-based), and the handling of complex data structures can all affect the system's responsiveness and resource utilization. Additionally, the security implications of argument passing must be carefully considered, as improper handling can lead to vulnerabilities such as buffer overflows or race conditions. A well-designed argument passing mechanism should balance performance, flexibility, and security to provide a robust and reliable interface between user-level processes and the operating system kernel.

• 3. System calls for user process

  System calls are the fundamental interface between user-level processes and the operating system kernel, allowing processes to request services and access system resources. The design and implementation of system calls for user processes is a critical aspect of operating system architecture, as it directly impacts the functionality, performance, and security of the overall system. Effective system call design should provide a comprehensive and intuitive set of interfaces that cover a wide range of user-level needs, such as file I/O, process management, memory management, and inter-process communication. These system calls should be designed with careful consideration of factors such as parameter passing, error handling, and resource management to ensure efficient and reliable operation. Additionally, the security implications of system calls must be thoroughly addressed, as they represent a potential attack surface for malicious actors. Robust input validation, access control mechanisms, and privilege separation are essential to mitigate the risks associated with system call usage. Overall, the design and implementation of system calls for user processes is a critical aspect of operating system development, requiring a deep understanding of system architecture, performance optimization, and security best practices. A well-designed system call interface can greatly enhance the usability, reliability, and security of the operating system for end-users and developers alike.

• 4. System calls for file manipulation

  System calls for file manipulation are a crucial component of operating system functionality, as they provide the interface for user-level processes to interact with the file system. The design and implementation of these system calls must balance several important considerations, including performance, reliability, and security. Efficient file manipulation system calls should offer a comprehensive set of operations, such as open, read, write, close, and seek, allowing processes to perform a wide range of file-related tasks. These system calls should be optimized for performance, minimizing overhead and maximizing throughput, while also ensuring data integrity and consistency. Security is another critical aspect of file manipulation system calls, as they represent a potential attack vector for malicious actors. Robust input validation, access control mechanisms, and privilege separation are essential to prevent unauthorized access, data corruption, or other security breaches. Additionally, the system calls should be designed to handle edge cases and error conditions gracefully, providing clear and informative error messages to aid in debugging and troubleshooting. This can include handling scenarios such as file not found, insufficient permissions, or disk full conditions. Overall, the design and implementation of system calls for file manipulation is a complex and multifaceted challenge, requiring a deep understanding of operating system architecture, file system design, performance optimization, and security best practices. A well-designed set of file manipulation system calls can greatly enhance the usability, reliability, and security of the operating system for end-users and developers.

• 5. Denying writes

  The ability to deny writes is an important feature in operating system design, as it allows for the enforcement of access control policies and the protection of critical system resources. This functionality is particularly relevant in the context of file system management, where the operating system must ensure that only authorized processes can modify or overwrite data. Denying writes can be implemented through a variety of mechanisms, such as file permissions, access control lists (ACLs), or mandatory access control (MAC) policies. These mechanisms should be designed to provide a granular and flexible approach to managing write access, allowing system administrators to define and enforce specific rules based on user, process, or resource attributes. The implementation of write denial must also consider performance implications, as the overhead of access control checks can impact overall system responsiveness. Efficient algorithms and data structures for managing access control information, as well as the use of caching and optimization techniques, can help mitigate these performance concerns. Additionally, the write denial functionality must be designed with security in mind, ensuring that it cannot be bypassed or subverted by malicious actors. This may involve the use of trusted computing base (TCB) principles, secure boot processes, and other security-hardening techniques. Overall, the ability to deny writes is a critical feature of modern operating systems, enabling the protection of sensitive data and the enforcement of robust access control policies. The design and implementation of this functionality must balance performance, flexibility, and security considerations to provide a reliable and effective solution for system administrators and end-users.