Re: [PATCH] ARM: Kconfig: default to AEABI w/ Clang

[Russell King - ARM Linux admin]

On Thu, Jul 04, 2019 at 10:29:35AM +0200, Arnd Bergmann wrote:
> On Thu, Jul 4, 2019 at 10:13 AM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> > On Tue, Jun 25, 2019 at 11:04 PM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote:
> >
> > > Clang produces references to __aeabi_uidivmod and __aeabi_idivmod for
> > > arm-linux-gnueabi and arm-linux-gnueabihf targets incorrectly when AEABI
> > > is not selected (such as when OABI_COMPAT is selected).
> > >
> > > While this means that OABI userspaces wont be able to upgraded to
> > > kernels built with Clang, it means that boards that don't enable AEABI
> > > like s3c2410_defconfig will stop failing to link in KernelCI when built
> > > with Clang.
> > >
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/482
> > > Link: https://groups.google.com/forum/#!msg/clang-built-linux/yydsAAux5hk/GxjqJSW-AQAJ
> > > Suggested-by: Arnd Bergmann <arnd@xxxxxxxx>
> > > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> >
> > As reflecting the state of things with CLANG it's:
> > Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> >
> > But I think we in general need to have some discussion on how to
> > proceed with OABI userspaces.
> >
> > I am well aware of distributions like OpenWrt using EABI even
> > on ARMv4 with "tricks" like this:
> > https://github.com/openwrt/openwrt/blob/master/toolchain/gcc/patches/9.1.0/840-armv4_pass_fix-v4bx_to_ld.patch
> 
> I did not expect that to be necessary in gcc as long as it supports
> building for armv4 (non-t), but I might be missing something here.
> 
> > I have one OABI that I can think of would be nice to live on
> > and it's the RedHat derivative on my Foorbridge NetWinder.
> > OK I wouldn't cry if we have to kill it because it is too hard to
> > keep supporting it, but it has been running the latest kernels
> > all along so if it's not a huge effort I'd be interested in knowing
> > the options.
> 
> But do you see any problems with cross-compiling kernels to
> EABI with CONFIG_OABI_COMPAT for machines like that?

Yes, there are a few ioctls that break.

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