Re: [RFC PATCH 1/2] kbuild: add CONFIG_LD_IS_BINUTILS

[Fangrui Song]

On 2020-04-24, Masahiro Yamada wrote:
> On Fri, Apr 24, 2020 at 3:44 AM Nick Desaulniers
> <ndesaulniers@xxxxxxxxxx> wrote:
> > On Sun, Apr 19, 2020 at 6:19 AM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> > >
> > > This patch is currently not mandatory but a prerequisites for the second one.
> > >
> > > Folks from ClangBuiltLinux project like the combination of Clang compiler
> > > and LLD linker from LLVM project to build their Linux kernels.
> > >
> > > Sami Tolvanen <samitolvanen@xxxxxxxxxx> has a patch for using LD_IS_LLD (see [1]).
> > >
> > > Documentation/process/changes.rst says and uses "binutils" that's why I called
> > > it LD_IS_BINUTILS (see [2] and [3]).
> > >
> > > The second patch will rename existing LD_VERSION to BINUTILS_VERSION to have
> > > a consistent naming convention like:
> > >
> > > 1. CC_IS_GCC and GCC_VERSION
> > > 2. CC_IS_CLANG and CLANG_VERSION
> > > 3. LD_IS_BINUTILS and BINUTILS_VERSION
> > >
> > > [1] https://github.com/samitolvanen/linux/commit/61889e01f0ed4f07a9d631f163bba6c6637bfa46
> > > [2] https://git.kernel.org/linus/tree/Documentation/process/changes.rst#n34
> > > [3] https://git.kernel.org/linus/tree/Documentation/process/changes.rst#n76
> > >
> > > Signed-off-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
> >
> > Just some background on Sami's patch.  Originally we were using
> > ld.gold (for LTO for Pixel 3) before moving to ld.lld (for LTO for
> > Pixel 4 and later).  Not sure if Kconfig would be a better place to
> > check if gold is used, then warn?  I kind of prefer the distinction
> > that binutils contains two different linkers, though if no one is
> > supporting ld.gold, and it doesn't work for the kernel, then maybe
> > that preference is moot?
>
>
> I prefer LD_IS_BFD, like this patch:
> https://lore.kernel.org/patchwork/patch/1039719/
>
> We do not need LD_IS_GOLD, though.
>
> --
> Best Regards
> Masahiro Yamada

+1 for CONFIG_LD_IS_BFD

Usually GNU ld is also installed as ld.bfd and can be referred to by -fuse-ld=bfd (GCC >= 9, or clang)

The repository binutils-gdb includes two linkers: GNU ld and GNU gold, so CONFIG_LD_IS_BINUTILS would be ambiguous.