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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Wed, 21 Feb 2018 17:59:34 +0100
Message-ID: <CAK8P3a2iFfrH5B8sha7GMEPN-pv995X_1b6-Bo4h=wBLGhhUPg@mail.gmail.com>
Subject: Re: [PATCH 00/31 v2] PTI support for x86_32
To:     Lorenzo Colitti <lorenzo@google.com>
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Mark D Rustad <mrustad@gmail.com>,
        Adam Borowski <kilobyte@angband.pl>,
        Joerg Roedel <jroedel@suse.de>,
        Andy Lutomirski <luto@kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>, X86 ML <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Juergen Gross <jgross@suse.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Borislav Petkov <bp@alien8.de>, Jiri Kosina <jkosina@suse.cz>,
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        Denys Vlasenko <dvlasenk@redhat.com>,
        Eduardo Valentin <eduval@amazon.com>,
        Will Deacon <will.deacon@arm.com>,
        "Liguori, Anthony" <aliguori@amazon.com>,
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On Wed, Feb 21, 2018 at 11:26 AM, Lorenzo Colitti <lorenzo@google.com> wrote:
> On Wed, Feb 14, 2018 at 5:54 PM, Greg KH <gregkh@linuxfoundation.org> wrote:
>> > > IPSEC doesn't work with a 64bit kernel and 32bit userspace right now.
>> > >
>> > > Back in 2015 someone started to work on that, and properly marked that
>> > > the kernel could not handle this with commit 74005991b78a ("xfrm: Do not
>> > > parse 32bits compiled xfrm netlink msg on 64bits host")
>> > >
>> > > This is starting to be hit by some Android systems that are moving
>> > > (yeah, slowly) to 4.4 :(
>> >
>> > Does anybody have test-programs/harnesses for this?
>>
>> Lorenzo (now on the To: line), is the one that I think is looking into
>> this, and should have some sort of test for it.  Lorenzo?
>
> Sorry for the late reply here. The issue is that the xfrm uapi structs
> don't specify padding at the end, so they're a different size on
> 32-bit and 64-bit archs. This by itself would be fine, as the kernel
> could just ignore the (lack of) padding. But some of these structs
> contain others (e.g., xfrm_userspi_info contains xfrm_usersa_info),
> and in that case the whole layout after the contained struct is
> different.

So this is x86 specific then and it already works correctly on all
other architectures (especially arm64 Android), right?

      Arnd