The place where syscall information is gathered is:

arch/x86/include/asm/unistd_32.h
arch/x86/include/asm/unistd_64.h
arch/s390/include/asm/unistd.h
arch/powerpc/include/asm/unistd.h
arch/ia64/include/asm/unistd.h
arch/alpha/include/asm/unistd.h

