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Re: Update on wip-arm-bootstrap

From: Danny Milosavljevic
Subject: Re: Update on wip-arm-bootstrap
Date: Mon, 22 Feb 2021 02:03:21 +0100

> > Does that mean there are no old reference binaries known to work on
> > Novena?  
> Not if they are binaries from before Lenny (2009), unless we compile the
> kernel with OABI support, which as I understand from Danny, is a bad
> idea.  Weird.

It backdoors https://en.wikipedia.org/wiki/Seccomp if you enable the kernel
option CONFIG_OABI_COMPAT (it also breaks syscall auditing).

And it's very easy to just change the syscall facility in glibc to emit EABI
syscalls (load one new register with constant, and the swi number is different).

Also, binaries compiled with gcc already [say they] are EABI (while using
OABI syscalls :P).

So I think just using EABI syscalls is easier than figuring out how to get
gcc to emit OABI executables--which otherwise are an obsolete format.

GNU Mes for ARM does not use OABI for its own system calls either.

I mean as a test we could totally enable that kernel option and see
whether the bootstrap works.  But it's of limited long-term use.  If we want
regular people to be able to build our bootstrap binaries, we probably
shouldn't rely on them enabling obscure kernel options where the kernel docs
say you shouldn't enable those.

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