Re: [edk2-devel] [PATCH v4 01/10] BaseTools: add BASETOOLS define

["Ard Biesheuvel" <ardb@kernel.org>]

On Tue, 18 Apr 2023 at 15:20, Gerd Hoffmann <kraxel@redhat.com> wrote:
>
> On Tue, Apr 18, 2023 at 01:59:43PM +0200, Ard Biesheuvel wrote:
> > On Tue, 18 Apr 2023 at 13:52, Gerd Hoffmann <kraxel@redhat.com> wrote:
> > >
> > > Seems to work fine on fedora 37, even without adding --relax, maybe this
> > > is enabled by default (there is a --no-relax switch after all).  I'll go
> > > try older distros / compilers / binutils too.
> > >
> > > What would be the failure mode?  Errors on ELF -> PE conversion because
> > > a GOT is present?  Or will things break at runtime?
> > >
> >
> > The problem here is that we rely on --emit-relocs to get at the
> > relocations in the binary, in order to convert the absolute ones into
> > PE/COFF relocations.
> >
> > However, --emit-relocs did not use to cover the GOT, as those are
> > added at the end by the linker and not by the compiler. So if the GOT
> > is non-empty, the resulting PE executable will be corrupt.
>
> So no build error.  And at runtime probably random effects, depending on
> whenever the execution path happens to hit a bad relocation or not.  So
> compile + boot testing doesn't cut it.  Lovely.
>
> So, what can I do instead?  Check **/DEBUG/*.debug and see whenever a
> .got section is present?
>

We should probably add an ASSERT() to the linker script, just like I
did for Linux:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e544ea57ac0734bc
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=262b5cae67a67240

> > Of course, the answer here is to dump GenFw altogether for ELF to PE
> > conversion, and implement something that consumes the dynamic
> > relocations generated when linking in PIE mode.
>
> Marvin's ImageTool is exactly that I think ...
>
> take care,
>   Gerd
>