Xv6

(15 points) You will trace the read()system call. Assume that a user program executes the statement read(fd, *buf, count) but fd is undefined. Therefore, the result of the execution will be an exception. You are asked to write down in a document which lines in which files of xv6 are executed. Organize the lines of code into blocks of code and explain the purpose of each of block. The result will be a story of what happened when a non-existing file descriptor is given to a read(). The story starts in the user space when the system call first gets executed and ends with feedback to the user that fd is bad.