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Date: Fri, 11 Aug 2017 17:24:29 +0200 From: Florian Weimer <fweimer@...hat.com> To: Michal Hocko <mhocko@...nel.org> Cc: Colm MacCárthaigh <colm@...costs.net>, Kees Cook <keescook@...omium.org>, Mike Kravetz <mike.kravetz@...cle.com>, Rik van Riel <riel@...hat.com>, Will Drewry <wad@...omium.org>, akpm@...ux-foundation.org, dave.hansen@...el.com, kirill@...temov.name, linux-api@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, luto@...capital.net, mingo@...nel.org Subject: Re: [PATCH v2 0/2] mm,fork,security: introduce MADV_WIPEONFORK 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. 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. Florian
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