Arnd Bergmann [off-list ref] writes:

The _syscallX macros were originally used by libc implementations,
but now there is no libc that can be built against an up-to-date
kernel an relies on them.
The only users of these macros are the __KERNEL_SYSCALLS_, which
are now gone as well, after execve has been removed from the
kernel.

I would prefer to keep them on i386/x86-64 at least because
a lot of my test programs are using them.

-Andi