How to find a definition of a specific syscall in Linux sources?

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http://stackoverflow.com – I recently wanted to see how is open() system call implemented in Linux kernel. Looking at the syscall table suggested that the name of the function I'm looking for is sys_open(), so I grepped for it. I couldn't find any declaration though, the closest I could get was do_sys_open in fs/open.c. Is it somehow translated into this function? What may I have missed? (HowTos)