linux-kernel - Re: [PATCH v2 3/7] seccomp: Allow arch code to provide seccomp

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Date:	Fri, 18 Jul 2014 15:26:13 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Kees Cook <keescook@...omium.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Will Drewry <wad@...omium.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux MIPS Mailing List <linux-mips@...ux-mips.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	Alexei Starovoitov <ast@...mgrid.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 3/7] seccomp: Allow arch code to provide seccomp_data

On Fri, Jul 18, 2014 at 3:16 PM, Kees Cook <keescook@...omium.org> wrote:
> On Fri, Jul 18, 2014 at 2:18 PM, Andy Lutomirski <luto@...capital.net> wrote:
>> populate_seccomp_data is expensive: it works by inspecting
>> task_pt_regs and various other bits to piece together all the
>> information, and it's does so in multiple partially redundant steps.
>>
>> Arch-specific code in the syscall entry path can do much better.
>>
>> Admittedly this adds a bit of additional room for error, but the
>> speedup should be worth it.
>
> I still think we should gain either a note in the
> HAVE_ARCH_SECCOMP_FILTER help text in arch/Kconfig, or possibly a new
> section in Documentation/prctl/seccomp.txt (or similar) on how do
> implement filter support for an architecture, that mentions the
> arch-supplied seccomp_data and how two-phase can be done.

I would have sworn I did that.  I distinctly remember typing that
text.  I must have failed to commit it.

I'll send a followup patch.

--Andy

>
> -Kees
>
> --
> Kees Cook
> Chrome OS Security



-- 
Andy Lutomirski
AMA Capital Management, LLC
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