linux-kernel - Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO

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Message-ID: <6b4c2c4f-00db-22b7-db3a-a1e76899c6d0@redhat.com>
Date:   Wed, 23 May 2018 18:36:08 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>
Cc:     Andrew Lutomirski <luto@...nel.org>, mjw@...oraproject.org,
        "H.J. Lu" <hjl.tools@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        nickc@...hat.com, ccoutant@...il.com,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO

On 05/23/2018 05:06 PM, Linus Torvalds wrote:
> 
> 
> On Wed, May 23, 2018, 17:01 Andy Lutomirski <luto@...capital.net <mailto:luto@...capital.net>> wrote:
> 
> 
>     I don’t know whether I’m missing something obvious, but can’t this be in C?
> 
> 
> Yes, but I thought Laura wanted to limit it to linker file tricks (this thread has gone on for so long that I've forgotten the details of why).
> 
>         Linus
> 
> 

So we have to update the kernel and every module and the easiest way
to do that was the linker script. I was assuming I'd just use the
same approach for the vDSO but you're right that there's no reason
we can't apply a different technique. I notice there's already a
vdso-note.S which adds LINUX_VERSION_CODE as a note. This doesn't
include the extra version so it doesn't quite meet our needs.
There's no reason why we can't throw something else in there for
good measure.

Thanks,
Laura