Re: [gentoo-embedded] Tool for eliminating non used code or symbols?

[Kfir Lavi]

On Sat, Mar 30, 2013 at 4:09 AM, Markos Chandras <hwoarang@g.o>wrote:

> On 25 March 2013 07:01, Kfir Lavi <lavi.kfir@×××××.com> wrote:
> > Hi,
> > I'm looking for a way to reduce glibc code size.
> > It can be a way to make system smaller and minimize the impact
> > of attack vectors in glibc, as in return-to-libc attack.
> >
> > Lets say I'm deleting the program 'mkdir', and mkdir uses a function
> > in glibc that non of the other parts of the system uses.
> > Then I want to eliminate this function from glibc. This leads to smaller
> > code and if this function is used in some attack scenario, maybe prevent
> it.
> >
> > Is there a way to do it?
> > Can you help me think how to build a tool like this? or, integrate
> > with existing tools.
> >
> > Thanks,
> > Kfir
> >
>
> You can use -Os when you compile your packages to reduce the size of
> the resulting ELF file.
> As for the second part of your question, I am not sure if this is
> possible. I haven't thought this through, but
> assuming you know no other packages depend on the function you want to
> remove, you will have to mess
> with the ELF file and its plt and other section entries to remove all
> the references of that symbol. It's likely you
> will break the file in the end.
>
> --
> Regards,
> Markos Chandras - Gentoo Linux Developer
> http://dev.gentoo.org/~hwoarang
>
> Yes you right,
This is why I want to remove the function from the sources and compile it
again.

Kfir