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Subject: Re: svn commit: r274017 - head/sys/kern
From: Alfred Perlstein <bright@mu.org>
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Date: Tue, 4 Nov 2014 06:23:34 -0800
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References: <201411030746.sA37kpPu037113@svn.freebsd.org>
 <5457F771.3010509@freebsd.org> <20141104092558.GP53947@kib.kiev.ua>
 <88CC9FA2-D677-484A-8D6B-9DA66D8479AE@mu.org>
To: Konstantin Belousov <kostikbel@gmail.com>
Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>,
 "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>,
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 Mateusz Guzik <mjg@FreeBSD.org>
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> On Nov 4, 2014, at 6:22 AM, Alfred Perlstein <bright@mu.org> wrote:
>=20
>=20
>=20
>>> On Nov 4, 2014, at 1:25 AM, Konstantin Belousov <kostikbel@gmail.com> wr=
ote:
>>>=20
>>> On Mon, Nov 03, 2014 at 01:45:21PM -0800, Alfred Perlstein wrote:
>>> Isn't there a problem where the stack can be swapped out?
>>>=20
>>> I seem to recall a problem where a swapped out process was causing=20
>>> problems due to a buffer passed being stack allocated and that process=20=

>>> being swapped out...
>>>=20
>>> If this is not the case then please disregard.
>>=20
>> Sure, stack can be swapped out, but buffer passing is usually not a probl=
em.
>> At least, I am not aware of cases.
>>=20
>> In fact, many compat layers do exactly this, allocate the native-ABI
>> structure on the stack, copyin the foreighn-ABI structure in pieces
>> into the native-ABI one, and pass native to kern_foo() implementations.
>>=20
>> So I think you worries are not realized.
>=20
> Ok then as long as system will not pass this buffer as Dma target down to d=
river we are ok. =20

Also thank you for explanation.=20=