Date:   Thu, 17 Jun 2021 10:47:54 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Helge Deller <deller@....de>
Cc:     Parisc List <linux-parisc@...r.kernel.org>,
        Meelis Roos <mroos@...ux.ee>,
        Linux Kernel Development <linux-kernel@...r.kernel.org>
Subject: Re: linux-parisc compile failure in current git

On Thu, Jun 10, 2021 at 4:04 PM Helge Deller <deller@....de> wrote:
>
> Hi Masahiro,
>
> On 6/10/21 4:03 AM, Masahiro Yamada wrote:
> > On Thu, Jun 10, 2021 at 7:50 AM Helge Deller <deller@....de> wrote:
> >>
> >> On 6/1/21 12:21 PM, Meelis Roos wrote:
> >>> Upstream Linux git fails to compile on gentoo hppa -  .config below.
> >>> I have 2 gcc-s as always:
> >>> $ gcc-config -l
> >>>    [1] hppa2.0-unknown-linux-gnu-9.3.0
> >>>    [2] hppa2.0-unknown-linux-gnu-10.2.0 *
> >>>
> >>>    [3] hppa64-unknown-linux-gnu-10.2.0 *
> >>
> >>
> >> I see the same issue too, but only when compiling natively on a parisc machine.
> >> Cross-compiling on a x86 box works nicely.
> >>
> >> First I thought it's a problem with setting the "cross_compiling" flag in ./Makefile.
> >> But that's not sufficient.
> >>
> >> On a x86 machine (which builds fine) I get
> >> SRCARCH=parisc SUBARCH=x86 UTS_MACHINE=parisc
> >> The arch/parisc/kernel/asm-offsets.c file gets preprocessed via:
> >> hppa64-linux-gnu-gcc
> >>
> >> On a native 32bit parisc machine I have:
> >> SRCARCH=parisc SUBARCH=parisc UTS_MACHINE=parisc
> >> Here the arch/parisc/kernel/asm-offsets.c file gets preprocessed via:
> >> gcc
> >> Instead here the native hppa64-linux-gnu-gcc (cross compiler) should have been used too, since
> >> we build a 64-bit hppa kernel (CONFIG_64BIT is set).
> >> Note, on hppa we don't have an "-m64" compiler flag as on x86.
> >
> > I see.
> > hppa is not a bi-arch compiler, in other words,
> > http- and hppa64- are separate compilers.
>
> Yes.
>
> >> Mashahiro, do you maybe have an idea what gets wrong here, or which
> >> patch has changed the behaviour how the asm-offsets.c file gets preprocessed?
> >
> > Presumably, commit 23243c1ace9fb4eae2f75e0fe0ece8e3219fb4f3
> >
> > Prior to that commit, arch/parisc/Makefile was like this:
> >
> > ifneq ($(SUBARCH),$(UTS_MACHINE))
> >          ifeq ($(CROSS_COMPILE),)
> >                      ...
> >
> > Now I understand why arch/parisc/Makefile was written this way.
> >
> > Reverting the change in arch/parisc/Makefile will restore the original behavior.
>
> Sadly, reverting this change (23243c1ace9fb4eae2f75e0fe0ece8e3219fb4f3) does not
> restore the original behavior.
>
> > But, please keep in mind that there is an issue remaining.
> >
> > Please see this code:
> >
> > ifdef CONFIG_64BIT
> > UTS_MACHINE := parisc64
> > CHECKFLAGS += -D__LP64__=1
> > CC_ARCHES = hppa64
> > LD_BFD := elf64-hppa-linux
> > else # 32-bit
> > CC_ARCHES = hppa hppa2.0 hppa1.1
> > LD_BFD := elf32-hppa-linux
> > endif
> >
> >
> > UTS_MACHINE is determined by CONFIG_64BIT.
> >
> > CONFIG_64BIT is defined only after Kconfig is finished.
> > When you are trying to configure the .config,
> > CONFIG_64BIT is not defined yet.
> > So UTS_MACHINE is always 'parisc'.
>
> Yes.
> See above, but it worked when I had SUBARCH=x86 (when running my laptop).
>
>
> > As you know, Kconfig files now have a bunch of 'cc-option' syntax
> > to check the compiler capability in Kconfig time.
> > Hence, you need to provide a proper compiler in Kconfig time too.
> >
> > When you build a 64-bit parisc kernel on a 32-bit parisc machine,
>
> Please note, that we don't have a 64-bit parisc userspace yet (just kernel).
> This means, that all builds on parisc machines are 32bit and do a
> cross-compilation to a parisc64 kernel if requested in the .config.
>
> > Kconfig is passed with CC=gcc since SUBARCH==UTS_MACHINE==parisc.
> > After Kconfig, CROSS_COMPILE=hppa64-* is set,
> > and the kernel is built by CC=hppa64-*-gcc.
>
> Right. That is the old behaviour. Based on the CONFIG_64BIT option
> the hppa64 compiler is choosen for CROSS_COMPILE.
>
> > So, Kconfig evaluated a compiletely different compiler. This is pointless.
>
> Yes, probably.
>
>
> > There are some options
> >
> > [option 1]
> >    revert the parisc bit of 23243c1ace9fb4eae2f75e0fe0ece8e3219fb4f3
> >    This will restore the functionality you may want, but
> >    as I said above, Kconfig is doing pointless things.
>
> as mentioned above: Doesn't solve the issue.
>
> > [option 2]
> >     Stop using cc-cross-prefix, and pass CROSS_COMPILE explicitly.
> >     This is what many architectures including arm, arm64 do.
> >     You need to explicitly pass CROSS_COMPILE=aarch64-linux-gnu- etc.
> >     if you are cross-compiling arm64.
>
> Might be an option, but it's not as handy as simply choosing CONFIG_64BIT
> and then things are done automatically.
>
> > [option 3]
> >     Introduce ARCH=parisc64.
> >
> >     When you are building 64-bit kernel, you can pass ARCH=parisc64
> >      A patch attached.  (but not tested much)
>
> Tried it, but doesn't work.
> asm-offsets.c is still preprocessed with 32bit compiler (gcc, not hppa20-gcc).
>
> Thanks for your help so far!
> If you like I'm happy to give you an account on a hppa64 machine to reproduce yourself.
> I'll now try to bisect where it goes wrong. There must be something else before commit 23243c1ace9fb4eae2f75e0fe0ece8e3219fb4f3.
>
> Helge


Sorry for my late reply.

Did git-bisect find something?

If necessary, I will be happy to try it on the hppa64 machine.



-- 
Best Regards
Masahiro Yamada

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