Perhaps the following will help you. Assuming you are using a 32-bit X86 2.6 Linux kernel .....
0x80 is the value of the software interrupt (INT) which performs the transfer to kernel mode via system_call(). See ../arch/x84/kernel/entry_32.S for the system_call() source.
The syscall interface for open() is defined in ../include/linux/syscalls.h
Code:
asmlinkage long sys_open(const char __user *filename, int flags, int mode);
