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Message-ID: <4F3DAE5D.3080000@zytor.com>
Date: Thu, 16 Feb 2012 17:33:17 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Indan Zupancic <indan@....nu>
CC: Will Drewry <wad@...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 04:48 PM, Indan Zupancic wrote:
> On Thu, February 16, 2012 22:17, H. Peter Anvin wrote:
>
> I would go for something like:
>
> struct seccomp_data {
> int nr;
> __u32 arg_low[6];
> __u32 arg_high[6];
> __u32 instruction_pointer_low;
> __u32 instruction_pointer_high;
> __u32 __reserved[3];
> };
>
Uh, that is the absolutely WORST way to do it - not only are you
creating two fields, they're not even adjacent.
> (Not sure what use the IP is because that doesn't tell anything about how
> the system call instruction was reached.)
>
> The only way to avoid splitting args is to add 64-bit support to BPF.
> That is probably the best way forwards, but would require breaking the
> BPF ABI by either adding a 64-bit version directly or adding extra
> instructions.
Or the compiler or whatever generates the BPF code just is going to have
to generate two instructions -- just like we always have to handle
[u]int64_t on 32-bit platforms. There is no difference here.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
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