linux-kernel - Re: [PATCH RFC 0/1] UAPI,x86: export syscall numbers for all x86 archs

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Message-ID: <CAHse=S8dN+e6nhSrf=hVLsfGyrR191mrxj_wc_OauqNtUXxSCg@mail.gmail.com>
Date:	Tue, 28 Jul 2015 16:32:14 +0100
From:	David Drysdale <drysdale@...gle.com>
To:	Paul Moore <paul@...l-moore.com>
Cc:	X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Eric Paris <eparis@...hat.com>,
	Linux API <linux-api@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 0/1] UAPI,x86: export syscall numbers for all x86 archs

On Tue, Jul 28, 2015 at 1:20 PM, Paul Moore <paul@...l-moore.com> wrote:
> On Tue, Jul 28, 2015 at 4:05 AM, David Drysdale <drysdale@...gle.com> wrote:
>> A while ago I was trying to build a seccomp-bpf filter program that would
>> survive a change of x86 architecture.  This was complicated for all sorts of
>> reasons, but one of the problems was that the different syscall numbers aren't
>> all available at the same time -- hence this patch.
>
> Or just use libseccomp and let it take care of all the different ABI
> specific warts for you.  The library handles the undefined syscalls
> you describe, but also multiplexed syscalls (e.g. socket related
> syscalls on x86) and proper invalid arch/ABI filtering

Ah, I hadn't realized that libseccomp handled cross-architecture
stuff and the socketcall multiplexing -- very neat.  I'll look into whether
I can convert my stuff to use it.

I still think exporting all the sub-arch syscall numbers is a good idea
though (even if my need for it is potentially reduced by libseccomp)...

> (you are
> filtering x32 correctly on x86-64 right?).

Yep, I think so, but it's fiddly.  If I can leave the fiddliness
to libseccomp, so much the better...

Thanks for the pointer,
David

>  * https://github.com/seccomp/libseccomp
>
> --
> paul moore
> www.paul-moore.com
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