v4.14.9 on ARMv5: OK with gcc 4.8/5.4, NOK with gcc 7.2

[Russell King - ARM Linux]

On Thu, Jan 04, 2018 at 07:19:45PM +0100, Andrea Adami wrote:
> On Thu, Jan 4, 2018 at 6:16 PM, Russell King - ARM Linux
> <linux at armlinux.org.uk> wrote:
> > On Thu, Jan 04, 2018 at 06:02:38PM +0100, Thomas Petazzoni wrote:
> >> Hello,
> >>
> >> I'm pretty sure it has already been reported, but just in case: I'm
> >> testing v4.14.9 on an ARMv5 platform (Kirkwood-based OpenBlocks A7).
> >> mvebu_v5_defconfig boots fine when built with gcc 4.8 (good old
> >> Sourcery toolchain) or gcc 5.4 (some old Linaro toolchain), but doesn't
> >> boot at all when built with gcc 7.2 (Fedora toolchain). Even when
> >> configured and booted with earlyprintk, the kernel doesn't say anything.
> >>
> >> The toolchain being used is the default ARM toolchain provided by
> >> Fedora 27. It says:
> >>
> >> gcc version 7.2.1 20170915 (Red Hat Cross 7.2.1-1) (GCC)
> >> GNU ld version 2.29.1-1.fc27
> >>
> >> So it's quite bleeding edge.
> >>
> >> Let me know if this has already been fixed, or if I should test a
> >> patch. I have not tested 4.15-rc or next at this point, assuming that
> >> if a fix had been made, it would have been backported to 4.14-stable.
> >
> > It's a known issue -
> >
> > http://archive.armlinux.org.uk/lurker/message/20171018.095713.a56a717b.en.html
> >
> > but so far no patches have been forthcoming for the kernel, because
> > (I guess) it's deemed to be a gcc bug.
> >
> > It's one of those discussions that just seemed to die without any
> > real conclusion.
> >
> > --
> > RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> > FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
> > According to speedtest.net: 8.21Mbps down 510kbps up
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 
> 
> I am happy to report the gcc bug has been fixed in trunk.
> I am as well dubious where they say this should also fix gcc6 where we
> have no known issues with gcc6.
> 
> "
> This should also fix
> incorrect generation of ldrd/strd with unaligned accesses that could
> previously have occurred on ARMv5e where all such operations must be
> 64-bit aligned."
> 
> https://github.com/gcc-mirror/gcc/commit/f59996b56aaa1c1d62a16cbb4010775b624cbde0
> 
> In OpenEmbedded we backported the patch a while ago, see the
> discussion about qemu booting where real hw doesn't:
> http://lists.openembedded.org/pipermail/openembedded-core/2017-November/144045.html

Thanks for reporting the update Andrea!

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up