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Re: wip-arm-bootstrap: Reduced binary seed bootstrap

From: Jan Nieuwenhuizen
Subject: Re: wip-arm-bootstrap: Reduced binary seed bootstrap
Date: Wed, 23 Dec 2020 13:14:49 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux)

Ludovic Courtès writes:


> Jan Nieuwenhuizen <janneke@gnu.org> skribis:
>> I pushed an initial wip-arm-bootstrap that builds up to tcc-boot:
>> ./pre-inst-env guix build -e '(@@ (gnu packages commencement) tcc-boot)'
>> Danny did a terrific job on armhf-linux support for GNU Mes and we are
>> getting close to release v0.23.  What's known to be missing is "setjmp"
>> support for tcc/gcc.  And, of course, for the Reduced binary seed
>> bootstrap to work on ARM!
> Woohoo, thumbs up for this great milestone, hackers! 🎉


>> Anyway, the problem I'm looking at now is that while tcc-boot builds on
>> an ARM box, it does not build on aarch64-linux, i.e. this
>> ./pre-inst-env guix build --system=armhf-linux \
>>   -e '(@@ (gnu packages commencement) tcc-boot0)'
>> fails on overdrive1.
> That’s “interesting”.  Did you eventually find a lead?

Yes, I added '|| BOOTSTRAP' in tccelf.c:

--8<---------------cut here---------------start------------->8---
#if defined (TCC_ARM_EABI) || BOOTSTRAP
    ehdr.e_ident[EI_OSABI] = 0;
    ehdr.e_flags = EF_ARM_EABI_VER4;
    if (file_type == TCC_OUTPUT_EXE || file_type == TCC_OUTPUT_DLL)
        ehdr.e_flags |= EF_ARM_HASENTRY;
    if (s1->float_abi == ARM_HARD_FLOAT)
        ehdr.e_flags |= EF_ARM_VFP_FLOAT;
        ehdr.e_flags |= EF_ARM_SOFT_FLOAT;
    ehdr.e_ident[EI_OSABI] = ELFOSABI_ARM;
--8<---------------cut here---------------end--------------->8---

this should be investigated a bit further.  Compiling with TCC_ARM_EABI
fails (which should work, really), but for this linking stage we need it
set to produce an aarch64-linux-compatible ELF header.  Dunno!

> Thanks for the update, it’s exciting!

You're welcome!  Meanwhile, I built gcc-core-mesboot0 (2.95.3).
However, that's using bash from %bootstrap-coreutils&co.

The last thing I did was to investigate into bash-2.05b and found that
bash depends on a working setjmp/longjmp for tinycc.  I tried several
versions of macro substitution on x86 instead of setjmp/longjmp, but
that doesn't seem possible: subshells and such.  So Danny, would you
like to look at that?


Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
Freelance IT http://JoyofSource.com | Avatar® http://AvatarAcademy.com

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