linux-kernel - Re: Edited seccomp.2 man page for review [v2]

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Message-ID: <54AD2549.9040107@redhat.com>
Date:	Wed, 07 Jan 2015 13:23:37 +0100
From:	Daniel Borkmann <dborkman@...hat.com>
To:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
CC:	Kees Cook <keescook@...omium.org>,
	Linux API <linux-api@...r.kernel.org>,
	"linux-man@...r.kernel.org" <linux-man@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Will Drewry <wad@...omium.org>, ast@...mgrid.com
Subject: Re: Edited seccomp.2 man page for review [v2]

On 01/07/2015 12:53 PM, Michael Kerrisk (man-pages) wrote:
...
> Still hoping to hear from Will Drewy regarding this FIXME in the
> page source:
>
> .\" FIXME What is the significance of the line
> .\"           ftest->code = BPF_LDX | BPF_W | BPF_ABS;
> .\"       in kernel/seccomp.c::seccomp_check_filter()?

This came in from our rework via commit bd4cf0ed331a ("net: filter:
rework/optimize internal BPF interpreter's instruction set"), and
is kernel-internal only, and unused in classic BPF. It translates
into A = *(u32 *) (ctx + K) and will basically load an offset from
the populated seccomp_data (= ctx) to A. For the man-page itself
it has therefore no relevance, hope that clarifies it.

Cheers,
Daniel
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