[llvm-dev] Should lld support binary output ("--oformat binary")?

Sean Silva via llvm-dev llvm-dev at lists.llvm.org
Thu Aug 18 13:13:27 PDT 2016

On Thu, Aug 18, 2016 at 8:32 AM, Davide Italiano via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> On Thu, Aug 18, 2016 at 2:16 PM, Ed Maste via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > One remaining blocking issue for linking FreeBSD with lld is the
> > inability to build the bootloader components. We have a patch[1] in
> > review to address one of the problems by switching to using a linker
> > script instead of GNU ld's -N option. Another issue is that some
> > bootloader components are created by the linker directly as binary
> > objects, using --oformat binary. (Other bootloader components are
> > built by creating a temporary ELF object converting that to a raw
> > binary using objcopy.)
> >
> > Is binary output enough of an unusual use case that we're unlikely to
> > support it in lld?
> >
> On a related note. FreeBSD (and also a product on which I work on) uses
> -b for kernel modules. I really would like to avoid changing all the
> invocations to objcopy. Hw vendors (e.g. network drivers which ship
> with firmware) rely on this feature. With that in mind, I'm not
> exactly looking forward to make them unhappy and force to change their
> internal build, in particular considering how hard is to get driver
> support these days.

This is the next issue that Michael and I ran into after figuring out what
was needed to get the kernel to boot (the remaining patches for that are in

It turns out that implementing that is very simple (essentially identical
to the shader binary stuff that we already implemented for PS4, which
internally uses the same mechanism). Yesterday Michael ported that code
onto ToT and hopefully there will be a patch up soon.

-- Sean Silva

> --
> Davide
> "There are no solved problems; there are only problems that are more
> or less solved" -- Henri Poincare
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