linux-kernel - RE: [PATCH] x86: Remove a.out support

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Date:   Mon, 4 Apr 2022 17:07:11 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "'Maciej W. Rozycki'" <macro@...am.me.uk>,
        Kees Cook <keescook@...omium.org>
CC:     James Jones <linux@...innocuous.com>,
        "bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] x86: Remove a.out support

From: Maciej W. Rozycki
> Sent: 04 April 2022 12:04
> 
> On Sat, 2 Apr 2022, Kees Cook wrote:
> 
> > > Chiming in late as I'm scanning outstanding mailing list traffic: if this
> > >is as you say all statically linked stuff, then converting from a.out to
> > >ELF might be as easy as:
> > >
> > >$ objcopy -I a.out-i386-linux -O elf32-i386 a.out-binary elf-binary
> >
> > Based on my research (and the wrapper I ended up writing), I don't think
> > this is sufficient because entry point handling is different between ELF
> > and a.out (specifically the stack layout and initial sp register value).
> 
>  Fair enough.  I guess the exact value of %esp doesn't matter that much
> (why would it?), but the arguments and environment may well be structured
> differently (and indeed based on a glance over binfmt_aout.c there's extra
> indirection involved compared to the ELF i386 psABI).

You could write a custom 'elf interpreter'.
Hacking at those isn't for the faint-hearted :-)

	David

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