Re: Update on wip-arm-bootstrap

[Jan Nieuwenhuizen]

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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