Re: [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF

[Will Drewry]

On Tue, Jan 17, 2012 at 10:45 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> On 01/16, Will Drewry wrote:
>>
>> On Mon, Jan 16, 2012 at 12:37 PM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
>> >
>> > Yes, thanks, I forgot about compat tasks again. But this is easy, just
>> > we need regs_64_to_32().
>>
>> Yup - we could make the assumption that is_compat_task is always
>> 32-bit and the pt_regs is always 64-bit, then copy_and_truncate with
>> regs_64_to_32.  Seems kinda wonky though :/
>
> much simpler/faster than what regset does to create the artificial
> user_regs_struct32.

True, I could collapse pt_regs to looks like the exported ABI pt_regs.
 Then only compat processes would get the copy overhead.  That could
be tidy and not break ABI.  It would mean that I have to assume that
if unsigned long == 64-bit and is_compat_task(), then the task is
32-bit.  Do you think if we ever add a crazy 128-bit "supercomputer"
arch that we will add a is_compat64_task() so that I could properly
collapse? :)

I like this idea!

>> > Doesn't matter. I think Indan has a better suggestion.
>>
>> I disagree, but perhaps I'm not fully understanding!
>
> I have much more chances to be wrong ;) I leave it to you and Indan.

We're being very verbose. I hope we can come to a good place!  I took
a break from my response to reply here :)

thanks!
will
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