Re: [PATCH v8 3/3] x86: vdso: Wire up getrandom() vDSO implementation

[Arnd Bergmann]

On Mon, Nov 28, 2022, at 12:18, Jason A. Donenfeld wrote:
> Hook up the generic vDSO implementation to the x86 vDSO data page. Since
> the existing vDSO infrastructure is heavily based on the timekeeping
> functionality, which works over arrays of bases, a new macro is
> introduced for vvars that are not arrays.
>
> Also enable the vgetrandom_alloc() syscall, which the vDSO
> implementation relies on.
>
> The vDSO function requires a ChaCha20 implementation that does not write
> to the stack, yet can still do an entire ChaCha20 permutation, so
> provide this using SSE2, since this is userland code that must work on
> all x86-64 processors.
>
> Reviewed-by: Samuel Neves <sneves@xxxxxxxxx> # for vgetrandom-chacha.S
> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
> ---
>  arch/x86/Kconfig                        |   1 +
>  arch/x86/entry/syscalls/syscall_64.tbl  |   1 +

I see that this enables the syscall in x86-64, while patch 1
adds it to the eight architecures that use 
include/uapi/asm-generic/unistd.h (with the __ARCH_WANT_*
guard at the moment, but you already said that will be removed)

I think ideally the syscall.tbl and unistd.h changes should be done
in one patch for all architectures that doesn't mix it with
any other changes. In particular I think it should be separate
from the vdso changes, but could be in the patch that implements
the syscall.

      Arnd