Getting Process Info from Kernel

Implement system call psinfo$()$ and the corresponding user program psinfo.c so that users can use

shell command psinfo to retrieve the same process information that shell command pstate provides.

psinfo$()$ however cannot use kernel$/$printf$.$c to directly print the process status. Instead, it should

pass the information to the user program.

Note that the I$/$O redirection in shell commands works in psinfo but not in pstate.

Make your own decision on the arguments of this system call, if needed.

Sample run: