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Message-ID: <4F3D7DD4.6070103@zytor.com>
Date: Thu, 16 Feb 2012 14:06:12 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Will Drewry <wad@...omium.org>
CC: Markus Gutschke <markus@...omium.org>, linux-kernel@...r.kernel.org,
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Subject: Re: [PATCH v8 3/8] seccomp: add system call filtering using BPF
On 02/16/2012 01:51 PM, Will Drewry wrote:
>>
>> Put the bloody bit in there and let the pattern program make that decision.
>
> Easy enough to add a bit for the mode: 32-bit or 64-bit. It seemed
> like a waste of cycles for every 32-bit program or every 64-bit
> program to check to see that its calling convention hadn't changed,
> but it does take away a valid decision the pattern program should be
> making.
>
> I'll add a flag for 32bit/64bit while cleaning up seccomp_data. I
> think that will properly encapsulate the is_compat_task() behavior in
> a way that is stable for compat and non-compat tasks to use. If
> there's a more obvious way, I'm all ears.
>
is_compat_task() is not going to be the right thing for x86 going
forward, as we're introducing the x32 ABI (which uses the normal x86-64
entry point, but with different eax numbers, and bit 30 set.)
The actual state is the TS_COMPAT flag in the thread_info structure,
which currently matches is_compat_task(), but perhaps we should add a
new helper function syscall_namespace() or something like that...
Either that or we can just use another bit in the syscall number field...
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
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