Definitions 1. Process A program in execution, and all of the resources associated with that executing instance of the program · Memory · Program Counter · Open files, other devices Process collection of resources and instruction to make up one instance of a program; memory, shared resources, etc 2. Software Table Walk TLB miss generates a trap (i.e. interrupt). OS reads page table in RAM and loads new entry into TLB. MIPS, NIOS II. In paging systems, a software table walk is a process where the operating system handles the translation of a virtual address to a physical address during a TLB (Translation Lookaside Buffer) miss. When the requested address is not found in the TLB, the operating system searches the page table, typically stored in RAM, to find the correct mapping. It then updates the TLB with this information, allowing the process to resume with the correct address mapping. This method involves additional overhead due to the operating system's involvement. 3. Worm Worms (Distinction between worm and virus is the vector. Virus needs a human action to infect, worm contains code to attack the next machine) · Worms Automated program that breaks into another system and creates a copy on the new system 0 soon running on many vulnerable systems 0 can take a delayed action (Code Red) Major Commercial Activity (Organized Crime) - child pornography, software piracy, spam 4. Copy on Write system processes are given a shared copy of a resource (like memory), and a separate copy is created only if a process attempts to modify it How does Copy on Write minimize copying memory for unix fork() call
You copy the page table, and all the memory frames are shared between the two processes, and duplicates of the frames are only made when they are modified locally by one of the processes. Thereby, minimizing copying memory. system processes are given a shared copy of a resource (like memory), and a separate copy is created only if a process attempts to modify it In your course notes, "Copy on Write" (CoW) is described as a method where, during a `fork()' system call, all pages are initially shared between the parent and child process. A page is only copied when it is modified, which requires hardware support, such as a read-only bit in the Memory Management Unit (MMU). This bit causes a trap if the CPU tries to write to the page, indicating that the page needs to be copied. This approach is more efficient in memory usage and avoids wasting CPU cycles on copying memory that might not be used, especially when the 'execv' or 'execve` commands are called immediately after a fork. 5. Deadlock Avoidance d. Deadlock avoidance Computing a safe state to avoid deadlock. - note state is safe if there is an order that processes can complete while consuming maximum declared resources (not required for full mark) 6. Physical Security Physical Security Physical Security · Physical access to the machine · bios password helps