RE: [PATCH] x86: Remove a.out support

David Laight
2022-03-16T17:05:15Z

From: Kees Cook
> Sent: 16 March 2022 16:11
>
> On Wed, Mar 16, 2022 at 05:06:10AM +0000, James Jones wrote:
> > I dug the scripts up in the state they were in when I gave up (September
> > 2020 according to mtime), and put them on github in case anyone wants to
> > have a go at it:
> >
> > https://github.com/cubanismo/aout-to-elf/
> >
> > It was an interesting problem in its own right, and I'd be curious to
> > know what I missed.
>
> Yeah, this is a good start. I think the main problem is with how program
> entry works, specifically that %esp is pointing to argc (with all the
> args in memory above there), which isn't the way ELF sets %esp.
>
> It might be possible to make a userspace loader, though. Hmm.

Could it be fixed up by a small bit of code that the elf interpreter
runs just before jumping the a.out entry point?

Depending on the elf layout it might be enough to just reset %esp.
But if the strings are the wrong side of argv[] and enpv[] the
vectors themselves might need copying further down the stack.

Should be possible to do it as PIC code.

David

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