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

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Message-ID: <67CF27C5-5013-4EF4-B24C-8D9EB52536FB@chromium.org>
Date:   Sat, 02 Apr 2022 19:24:26 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>,
        James Jones <linux@...innocuous.com>
CC:     bp@...en8.de, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Remove a.out support



On April 2, 2022 3:14:43 PM PDT, "Maciej W. Rozycki" <macro@...am.me.uk> wrote:
>On Wed, 16 Mar 2022, James Jones wrote:
>
>> Probably getting a bit off topic, but I did spend a few hours searching
>> around for any existing tools to convert a binary from a.out->ELF, and
>> trying to come up with something myself by extracting the sections with
>> objdump and re-combining them into an ELF using a linker script placing
>> the sections at the same locations. I couldn't get it working in an
>> evening or two messing with it so I moved on, but I agree something like
>> this seems possible in theory.
>
> 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).

-Kees

-- 
Kees Cook