From: David Laight <David.Laight@ACULAB.COM>
To: "'Kevin Cernekee'" <cernekee@chromium.org>,
"steffen.klassert@secunet.com" <steffen.klassert@secunet.com>,
"herbert@gondor.apana.org.au" <herbert@gondor.apana.org.au>,
"davem@davemloft.net" <davem@davemloft.net>,
"paul@paul-moore.com" <paul@paul-moore.com>,
"sds@tycho.nsa.gov" <sds@tycho.nsa.gov>,
"eparis@parisplace.org" <eparis@parisplace.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"selinux@tycho.nsa.gov" <selinux@tycho.nsa.gov>,
"fw@strlen.de" <fw@strlen.de>,
"fan.du@windriver.com" <fan.du@windriver.com>,
"dianders@chromium.org" <dianders@chromium.org>,
"dtor@chromium.org" <dtor@chromium.org>
Subject: RE: [PATCH 0/4] Make xfrm usable by 32-bit programs
Date: Mon, 23 Jan 2017 16:45:39 +0000 [thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6DB026BC58@AcuExch.aculab.com> (raw)
In-Reply-To: <20170121000507.34381-1-cernekee@chromium.org>
From: Kevin Cernekee
> Sent: 21 January 2017 00:05
> Several of the xfrm netlink and setsockopt() interfaces are not usable
> from a 32-bit binary running on a 64-bit kernel due to struct padding
> differences. This has been the case for many, many years[0]. This
> patch series deprecates the broken netlink messages and replaces them
> with packed structs that are compatible between 64-bit and 32-bit
> programs.
Do you mean '__packed' or just structures with no holes?
The latter is really the best.
You can add a compile time assert on the structure sizes to ensure
that the user API is never accidentally broken.
I can't imagine any reason to change the 64bit structures except
(maybe) to make any padding explicit.
> It retains support for legacy user programs (i.e. anything
> that is currently working today), and allows legacy support to be
> compiled out via CONFIG_XFRM_USER_LEGACY if it becomes unnecessary in
> the future.
...
Isn't that effectively the same as doing a compat layer?
Otherwise you can't build a 32bit app that will work with an 'old'
32bit kernel and a new 64bit one.
Provided you've got the length of the user's buffer the compat code
ought to be trivial (if tedious).
David
next prev parent reply other threads:[~2017-01-23 16:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-21 0:05 Kevin Cernekee
2017-01-21 0:05 ` [PATCH 1/4] xfrm: Constify xfrm_user arguments and xfrm_mgr callback APIs Kevin Cernekee
2017-01-21 0:05 ` [PATCH 2/4] xfrm_user: Allow common functions to be called from another file Kevin Cernekee
2017-01-21 0:05 ` [PATCH 3/4] xfrm_user: Initial commit of xfrm_user_legacy.c Kevin Cernekee
2017-01-21 0:05 ` [PATCH 4/4] xfrm_user: Add new 32/64-agnostic netlink messages Kevin Cernekee
2017-01-21 8:21 ` kbuild test robot
2017-01-23 9:35 ` [PATCH 0/4] Make xfrm usable by 32-bit programs Steffen Klassert
2017-01-23 15:47 ` David Miller
2017-01-23 16:45 ` David Laight [this message]
2017-01-23 16:57 ` David Miller
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