Re: [PATCH v2 01/18] kbuild: add ld-name macro and support for GNU gold

Kees Cook
2017-11-15T21:53:33Z

On Wed, Nov 15, 2017 at 1:34 PM, Sami Tolvanen <samitolvanen@google.com> wrote:
> GNU gold may require different flags than GNU ld. Add a macro for
> detecting the linker and conditionally add gold specific flags from
> LDFLAGS_GOLD.
>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

(It does seem weird to have only LDFLAGS instead of KBUILD_LDFLAGS,
but that's not really a problem for this patch exactly.)

-Kees

> ---
> Makefile | 5 +++++
> scripts/Kbuild.include | 4 ++++
> 2 files changed, 9 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index 763ab35df12a..f976af9525bf 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -827,6 +827,11 @@ include scripts/Makefile.kasan
> include scripts/Makefile.extrawarn
> include scripts/Makefile.ubsan
>
> +# Add any flags specific to ld.gold
> +ifeq ($(ld-name),gold)
> +LDFLAGS += $(LDFLAGS_GOLD)
> +endif
> +
> # Add any arch overrides and user supplied CPPFLAGS, AFLAGS and CFLAGS as the
> # last assignments
> KBUILD_CPPFLAGS += $(ARCH_CPPFLAGS) $(KCPPFLAGS)
> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> index 9ffd3dda3889..584d6cecd7c0 100644
> --- a/scripts/Kbuild.include
> +++ b/scripts/Kbuild.include
> @@ -172,6 +172,10 @@ ld-option = $(call try-run,\
> # Important: no spaces around options
> ar-option = $(call try-run, $(AR) rc$(1) "$$TMP",$(1),$(2))
>
> +# ld-name
> +# Expands to either bfd or gold
> +ld-name = $(shell $(LD) -v 2>&1 | grep -q "GNU gold" && echo gold || echo bfd)
> +
> # ld-version
> # Note this is mainly for HJ Lu's 3 number binutil versions
> ld-version = $(shell $(LD) --version | $(srctree)/scripts/ld-version.sh)
> --
> 2.15.0.448.gf294e3d99a-goog
>

--
Kees Cook
Pixel Security