Re: Update on wip-arm-bootstrap

[Jan Nieuwenhuizen <janneke@gnu.org>]

Danny Milosavljevic writes:

Hey Danny,

> On Thu, 18 Feb 2021 22:52:57 +0100
> Jan Nieuwenhuizen <janneke@gnu.org> wrote:
>
>> # CONFIG_OABI_COMPAT is not set
>> 
>> ...certainly a lot easier to find when you know what you're looking
>> for.
>> 
>> @Danny: I'm wondering if we could (should?) try a kernel with OABI
>> compatibility?  I suppose it would be better to somehow target
>> EABI...but I'm not sure that's possible with glibc-2.2.5 / gcc-2.95.3.
>> Interesting choices here!
>
> OABI is older than year 2000, and the kernel docs say not to enable it.
> It also breaks seccomp.
> I doubt that people have it enabled, and thus would have trouble reproducing
> our stuff.

Okay, I agree; better to not go this route if we can avoid it.

> Since this only affects the syscall interface and since also our
> ELF headers specify EABI, I would just change the syscalls to EABI:
> Just put the syscall number into r7 and use svc 0.

Oh, if that's all we should be able to find and fix it?

> I'd do it myself but I don't see what libc the gcc 2.95 we built has been
> using.
> Is it ours?
> If so, how come it then uses svc 90000... in the first place? 
> We don't do that.
>
> Or is it using glibc ?

Not it's not ours, it's gcc-core-mesboot0-2.95.3 binaries built against
glibc-mesboot0-2.2.5.  So then it's probably glibc-2.2.5 that is
using/built for OABI.  I didn't know of OABI before, but did look for
EABI options and didn't find any in those early gcc/glibc's...

We'll have to see if that glibc can be built for OABI, possibly by
patching it.  If we need to upgrade glibc then that may be an
"interesting" undertaking...

From Vagrant's link, I found that Lenny (5.0) is the first armel (EABI)
release, it uses glibc-2.7, gcc-4.1, binutils-2.18.

> How do I build that gcc on novena?  Where would the syscall headers that
> I could change be?

On latest wip-arm-bootstrap

    3c78496c32 DRAFT gnu: mes: Update to 0.22-124-33cf5ea5e8.

then building

    ./pre-inst-env guix build -e '(@@ (gnu packages commencement) gcc-mesboot0)'

will be using the gcc,glibc,binutils that's broken and configure will
fail on running a conftest.  You can get the PATH and other environment
settings from that build.  I have those settings also in a script:

    novena:~janneke/src/guix/gcc-mesboot.sh

is a reproducer.

Greetings,
Janneke

-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
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