linux-kernel - Re: [PATCH v6 7/9] x86: Enable Syscall User Dispatch

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Message-ID: <202009221236.04AA334C2@keescook>
Date:   Tue, 22 Sep 2020 12:37:02 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     luto@...nel.org, tglx@...utronix.de, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        willy@...radead.org, linux-kselftest@...r.kernel.org,
        shuah@...nel.org, kernel@...labora.com
Subject: Re: [PATCH v6 7/9] x86: Enable Syscall User Dispatch

On Fri, Sep 04, 2020 at 04:31:45PM -0400, Gabriel Krisman Bertazi wrote:
> Syscall User Dispatch requirements are fully supported in x86. This
> patch flips the switch, marking it as supported.  This was tested
> against Syscall User Dispatch selftest.
> 
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
> ---
>  arch/x86/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 7101ac64bb20..56ac8de99021 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -150,6 +150,7 @@ config X86
>  	select HAVE_ARCH_COMPAT_MMAP_BASES	if MMU && COMPAT
>  	select HAVE_ARCH_PREL32_RELOCATIONS
>  	select HAVE_ARCH_SECCOMP_FILTER
> +	select HAVE_ARCH_SYSCALL_USER_DISPATCH

Is this needed at all? I think simply "the architecture uses the generic
entry code" is sufficient to enable it. (Especially since there's a top
level config for SYSCALL_USER_DISPATCH, it feels like overkill).

-- 
Kees Cook