linux-kernel - Re: Ubuntu 16.10 - Linux Kernel build fails

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Date:   Tue, 18 Oct 2016 17:56:51 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Shuah Khan <shuahkhan@...il.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>, mmarek@...e.com,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Ubuntu 16.10 - Linux Kernel build fails - GCC related

On Tue, Oct 18, 2016 at 09:48:17AM -0600, Shuah Khan wrote:
> On Tue, Oct 18, 2016 at 9:37 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
> > On Tue, Oct 18, 2016 at 09:24:20AM -0600, Shuah Khan wrote:
> >> After upgrading to Ubuntu 16.10, I can't build kernels anymore unless
> >> the following patch is applied to the kernel Makefile. A word of
> >> caution for anybody that is planning to update their development
> >> systems.
> >>
> >> https://patchwork.ozlabs.org/patch/616621/
> >>
> >> Please refer to the Ubuntu 16.10 release notes for more details.
> >>
> >> https://wiki.ubuntu.com/YakketyYak/ReleaseNotes#GCC
> >>
> >> Ubuntu is recommended applying this patch for building Linux kernels.
> >> I am not sure this is the right way to go. I am hoping this is
> >> work-around and patching the kernel Makefile will not be the solution
> >> going forward.
> >>
> >> I haven't seen any patch sent upstream to make this change, so I still
> >> hope this is a temporary work-around. Maybe be there is patch that
> >> came through and you are aware of this problem?
> >
> > Does commit 6d92bc9d483a solve this issue for you?  That should have
> > resolved a -pie issue, back in 4.6, or is this something else?
> >
> 
> This is a new problem because of a change Ubuntu made in their gcc
> version 6.2.0 20161005 (Ubuntu 6.2.0-5ubuntu12) it appears.
> 
> The Ubuntu 16.10 release notes says:
> 
> "We have modified GCC to by-default compile programs with position
> independent executable support to improve the security benefits
> provided by
> Address Space Layout Randomization.
> 
> This may cause difficulty when trying to compile Linux kernels that
> still need this patch applied.
> Other programs may experience other problems; some debugging
> guidelines are at https://wiki.ubuntu.com/SecurityTeam/PIE"
> 
> The above clearly states a patch needs to applied to the Linux Kernel
> makefile. This patch forces no-pie for distro compilers that enable
> pie by default
> 
> The error I am seeing on 4.9-rc1 is:
> 
>  CHK     include/config/kernel.release
> Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong
> not supported by compiler
> Makefile:1058: recipe for target 'prepare-compiler-check' failed
> make: *** [prepare-compiler-check] Error 1
> 
> I think CONFIG_CC_STACKPROTECTOR_STRONG is enabled in most distro
> configs. So I am not why this should fail now.
> 
> Here is the Ubuntu recommended patch for easy reference: (note cut and
> paste - probably won't apply) -
> https://patchwork.ozlabs.org/patch/616621/

Did you follow up with Steve about this?  Seems odd that no one ever
followed up on it.

thanks,

greg k-h