linux-kernel - Re: [PATCH 1/7] kbuild: add ld-name macro and support for GNU gold

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Message-ID: <CAKwvOdme29UPfaV1CCbMXRM=LzZJ-asytEjGm_F7ARN0WrMsEg@mail.gmail.com>
Date:   Wed, 29 Nov 2017 16:32:52 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Alex Matveev <alxmtvv@...il.com>, Andi Kleen <ak@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        linux-arm-kernel@...ts.infradead.org,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Maxim Kuvyrkov <maxim.kuvyrkov@...aro.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Yury Norov <ynorov@...iumnetworks.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Nicholas Piggin <npiggin@...il.com>
Subject: Re: [PATCH 1/7] kbuild: add ld-name macro and support for GNU gold

On Wed, Nov 29, 2017 at 3:44 PM, Sami Tolvanen <samitolvanen@...gle.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.

Right, but you're still only ever using one linker per build, correct?
 Can we get away without 2 distinct flags?

> +# Add any flags specific to ld.gold
> +ifeq ($(ld-name),gold)
> +LDFLAGS                += $(LDFLAGS_GOLD)
> +endif
> +

Patch 1 and 6 have this pattern of always assigning to LDFLAGS_GOLD,
then that to LDFLAGS.  Wouldn't it be better to check the ld-name and
conditionally assign to LDFLAGS? Then LDFLAGS_GOLD is not necessary.
For example, what I'm suggesting is what is done in patch 4.

> +# ld-name
> +# Expands to either bfd or gold
> +ld-name = $(shell $(LD) -v 2>&1 | grep -q "GNU gold" && echo gold || echo bfd)
> +

This part LGTM.