Re: [PATCH v14 09/10] arch, mm: wire up memfd_secret system call were relevant

[Andrew Morton]

On Thu,  3 Dec 2020 08:29:48 +0200 Mike Rapoport <rppt@xxxxxxxxxx> wrote:

> From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> 
> Wire up memfd_secret system call on architectures that define
> ARCH_HAS_SET_DIRECT_MAP, namely arm64, risc-v and x86.
> 
> ...
>
> --- a/include/uapi/asm-generic/unistd.h
> +++ b/include/uapi/asm-generic/unistd.h
> @@ -861,9 +861,13 @@ __SYSCALL(__NR_faccessat2, sys_faccessat2)
>  __SYSCALL(__NR_process_madvise, sys_process_madvise)
>  #define __NR_watch_mount 441
>  __SYSCALL(__NR_watch_mount, sys_watch_mount)
> +#ifdef __ARCH_WANT_MEMFD_SECRET
> +#define __NR_memfd_secret 442
> +__SYSCALL(__NR_memfd_secret, sys_memfd_secret)
> +#endif

Why do we add the ifdef?  Can't we simply define the syscall on all
architectures and let sys_ni do its thing?