location of inbuilt system call implementation

Hi All, I am newbies to Linux and am going through system call in kernel-3.4. I just wanted to check how sys_read, sys_write or other system calls work but I was searching for the implementation but couldn't find it. I found that : System Call are added in /arch/x86/syscalls/syscall_32(or64).tbl. and they were declared in /incude/linux/sycalls.h But I was not able to find exactly where they are implemented. Thanking you all in advance.