how do i add a system call / utility in xv6

Question

Can any one tell me/ point me any references to how to add a system call / utility in XV6

exhaustive search on google was futile and hacking the hard way also was not productive so far .

the reference book also did not have any hello world example to start with any help greatly appreciated

Answer 1

To add a system call that can be called in xv6's shell, you should so something with the five files

• sysproc.c add the real implementation of your method here
• syscall.h define the position of the system call vector that connect to your implementation
• user.h define the function that can be called through the shell
• syscall.c external define the function that connect the shell and the kernel, use the position defined in syscall.h to add the function to the system call vector

• usys.S use the macro to define connect the call of user to the system call function

• defs.h add a forward declaration for your new system call

• sysfunc.h add the new system call handler into this file too like "int sys_newsystemcall(void)"