From: Michal Hocko <mhocko@kernel.org>
To: Florian Weimer <fweimer@redhat.com>
Cc: "Colm MacCárthaigh" <colm@allcosts.net>,
"Kees Cook" <keescook@chromium.org>,
"Mike Kravetz" <mike.kravetz@oracle.com>,
"Rik van Riel" <riel@redhat.com>,
"Will Drewry" <wad@chromium.org>,
akpm@linux-foundation.org, dave.hansen@intel.com,
kirill@shutemov.name, linux-api@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
luto@amacapital.net, mingo@kernel.org
Subject: Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK
Date: Fri, 11 Aug 2017 17:31:52 +0200 [thread overview]
Message-ID: <20170811153152.GR30811@dhcp22.suse.cz> (raw)
In-Reply-To: <6a04f59b-b72b-c468-ea5c-230764a24402@redhat.com>
On Fri 11-08-17 17:24:29, Florian Weimer wrote:
> On 08/11/2017 04:24 PM, Michal Hocko wrote:
> > On Fri 11-08-17 16:11:44, Florian Weimer wrote:
> >> On 08/11/2017 04:06 PM, Michal Hocko wrote:
> >>
> >>> I am sorry to look too insisting here (I have still hard time to reconcile
> >>> myself with the madvise (ab)use) but if we in fact want minherit like
> >>> interface why don't we simply add minherit and make the code which wants
> >>> to use that interface easier to port? Is the only reason that hooking
> >>> into madvise is less code? If yes is that a sufficient reason to justify
> >>> the (ab)use of madvise? If there is a general consensus on that part I
> >>> will shut up and won't object anymore. Arguably MADV_DONTFORK would fit
> >>> into minherit API better as well.
> >>
> >> It does, OpenBSD calls it MAP_INHERIT_NONE.
> >>
> >> Could you implement MAP_INHERIT_COPY and MAP_INHERIT_SHARE as well? Or
> >> is changing from MAP_SHARED to MAP_PRIVATE and back impossible?
> >
> > I haven't explored those two very much. Their semantic seems rather
> > awkward, especially map_inherit_share one. I guess MAP_INHERIT_COPY
> > would be doable. Do we have to support all modes or a missing support
> > would disqualify the syscall completely?
>
> I think it would be a bit awkward if we implemented MAP_INHERIT_ZERO and
> it would not turn a shared mapping into a private mapping in the child,
> or would not work on shared mappings at all, or deviate in any way from
> the OpenBSD implementation.
If we go with minherit API then I think we should adhere with the BSD
semantic and alloc MAP_INHERIT_ZERO for shared mappings as well
> MAP_INHERIT_SHARE for a MAP_PRIVATE mapping which has been modified is a
> bit bizarre, and I don't know how OpenBSD implements any of this. It
> could well be that the exact behavior implemented in OpenBSD is a poor
> fit for the Linux VM implementation.
yeah, it would be MAP_INHERIT_SHARE that I would consider problematic
and rather go with ENOSUPP or even EINVAL.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-08-11 15:31 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-06 14:04 [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK riel
2017-08-06 14:04 ` [PATCH 1/2] x86,mpx: make mpx depend on x86-64 to free up VMA flag riel
2017-08-06 14:04 ` [PATCH 2/2] mm,fork: introduce MADV_WIPEONFORK riel
2017-08-10 15:23 ` Michal Hocko
2017-08-11 15:23 ` Rik van Riel
2017-08-11 16:36 ` Mike Kravetz
2017-08-11 16:59 ` Rik van Riel
2017-08-11 17:07 ` Mike Kravetz
2017-08-07 13:22 ` [PATCH v2 0/2] mm,fork,security: " Michal Hocko
2017-08-07 13:46 ` Michal Hocko
2017-08-07 14:19 ` Florian Weimer
2017-08-10 13:06 ` Michal Hocko
2017-08-07 14:59 ` Rik van Riel
2017-08-09 9:59 ` Kirill A. Shutemov
2017-08-09 12:31 ` Rik van Riel
2017-08-09 12:42 ` Florian Weimer
2017-08-10 13:05 ` Michal Hocko
2017-08-10 13:23 ` Colm MacCárthaigh
2017-08-10 15:36 ` Michal Hocko
[not found] ` <CAAF6GDeno6RpHf1KORVSxUL7M-CQfbWFFdyKK8LAWd_6PcJ55Q@mail.gmail.com>
2017-08-10 17:01 ` Michal Hocko
2017-08-10 22:09 ` Colm MacCárthaigh
2017-08-11 14:06 ` Michal Hocko
2017-08-11 14:11 ` Florian Weimer
2017-08-11 14:24 ` Michal Hocko
2017-08-11 15:24 ` Florian Weimer
2017-08-11 15:31 ` Michal Hocko [this message]
[not found] ` <CAAF6GDcNoDUaDSxV6N12A_bOzo8phRUX5b8-OBteuN0AmeCv0g@mail.gmail.com>
2017-08-07 16:02 ` Colm MacCárthaigh
2017-08-10 13:21 ` Michal Hocko
2017-08-10 14:11 ` Michal Hocko
2017-08-07 18:23 ` Mike Kravetz
2017-08-08 9:58 ` Florian Weimer
2017-08-08 13:15 ` Rik van Riel
2017-08-08 15:19 ` Mike Kravetz
2017-08-08 15:22 ` Florian Weimer
2017-08-08 15:46 ` Rik van Riel
2017-08-08 16:48 ` Colm MacCárthaigh
2017-08-08 16:52 ` Matthew Wilcox
2017-08-08 18:45 ` Rik van Riel
2017-08-10 15:31 ` Michal Hocko
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