Re: [PATCH 2/6] x86: Enable seccomp architecture tracking

[Jann Horn]

On Thu, Sep 24, 2020 at 1:29 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> Provide seccomp internals with the details to calculate which syscall
> table the running kernel is expecting to deal with. This allows for
> efficient architecture pinning and paves the way for constant-action
> bitmaps.
[...]
> diff --git a/arch/x86/include/asm/seccomp.h b/arch/x86/include/asm/seccomp.h
[...]
> +#ifdef CONFIG_X86_64
[...]
> +#else /* !CONFIG_X86_64 */
> +# define SECCOMP_ARCH                                  AUDIT_ARCH_I386
> +#endif

If we are on a 32-bit kernel, performing architecture number checks in
the kernel is completely pointless, because we know that there is only
a single architecture identifier under which syscalls can happen.

While this patch is useful for enabling the bitmap logic in the
following patches, I think it adds unnecessary overhead in the context
of the previous patch.