Re: Could the fix for broken gcc-plugins with gcc-11 be backported to 5.10?

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Dec 06, 2021 at 12:29:31PM -0800, Kees Cook wrote:
> On Mon, Dec 06, 2021 at 03:41:55PM +0100, Greg KH wrote:
> > On Mon, Dec 06, 2021 at 02:59:57PM +0100, Thomas Lindroth wrote:
> > > On 12/6/21 14:27, Greg KH wrote:
> > > > On Mon, Dec 06, 2021 at 02:24:29PM +0100, Thomas Lindroth wrote:
> > > > > On 12/6/21 14:04, Greg KH wrote:
> > > > > > On Mon, Dec 06, 2021 at 01:59:31PM +0100, Thomas Lindroth wrote:
> > > > > > > Build support for gcc-plugins are not detected with gcc-11 in lts kernels.
> > > > > > > Gentoo and Arch apply their own patch to fix the problem in their distribution
> > > > > > > kernels but I would prefer if a proper fix was applied upstream.
> > > > > > > 
> > > > > > > https://bugs.gentoo.org/814200 a gentoo report with the relevant info.
> > > > > > > 
> > > > > > > I've searched for any upstream discussions about the problem but I've only found
> > > > > > > one message saying the backport needs an additional fix. That was almost a year
> > > > > > > ago. https://www.spinics.net/lists/stable/msg438000.html
> > > > > > 
> > > > > > We can not take a patch in a stable kernel release unless it is already
> > > > > > in Linus's tree.  Please work to get a patch accepted there first,
> > > > > > before worrying about older kernel versions.
> > > > > > 
> > > > > > thanks,
> > > > > > 
> > > > > > greg k-h
> > > > > > 
> > > > > 
> > > > > The problem was fixed in Linus tree in commit 67a5a68013056cbcf0a647e36cb6f4622fb6a470
> > > > > "gcc-plugins: fix gcc 11 indigestion with plugins..." added in v5.11
> > > > > 
> > > > > That's the patch that needed some kind of additional fix before it could be backported
> > > > > but that fix never materialized.
> > > > 
> > > > If you have a working version, based on a distro's use, please provide
> > > > it and I will be glad to pick it up.
> > > > 
> > > > thanks,
> > > > 
> > > > greg k-h
> > > > 
> > > 
> > > https://dev.gentoo.org/~mpagano/genpatches/trunk/5.10/2910_fix-gcc-detection-method.patch
> > > 
> > > Here is the patch gentoo applies to 5.10. It seems to be a combination of two upstream
> > > commits:
> > > 67a5a68013056cbcf0a647e36cb6f4622fb6a470 "gcc-plugins: fix gcc 11 indigestion with plugins..."
> > > 1e860048c53ee77ee9870dcce94847a28544b753 "gcc-plugins: simplify GCC plugin-dev capability test"
> > 
> > That's not how I can take a patch, sorry.  Please submit these as
> > individual emails so that then could be applied.
> > 
> > > I can't vouch for the correctness of that fix. I'm just a regular user who stumbled upon this
> > > problem and found that gentoo bug report. Check with Kees Cook for that "additional fix". I
> > > don't know what fix that is.
> > 
> > I don't think either of them differ from what is in mainline, so I do
> > not know.
> 
> Hi!
> 
> Yeah, the two fixes that I think are needed for v5.10 are:
> 
> 1e860048c53ee77ee9870dcce94847a28544b753
> 67a5a68013056cbcf0a647e36cb6f4622fb6a470
> 
> This additionally appears to match the combo patch in gentoo:
> https://814200.bugs.gentoo.org/attachment.cgi?id=746715
> 
> Local build testing shows the plugins working...

Ok, both now queued up, thanks.

greg k-h