linux-kernel - Re: [PATCH v2 10/18] arm64: add a workaround for GNU gold with ARM64_MODULE

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Message-ID: <20171116115012.GE9361@arm.com>
Date:   Thu, 16 Nov 2017 11:50:12 +0000
From:   Will Deacon <will.deacon@....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@...r.kernel.org,
        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>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Yury Norov <ynorov@...iumnetworks.com>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [PATCH v2 10/18] arm64: add a workaround for GNU gold with
 ARM64_MODULE_PLTS

On Wed, Nov 15, 2017 at 01:34:20PM -0800, Sami Tolvanen wrote:
> CONFIG_CLANG_LTO depends on GNU gold and due to a known bug, the
> linker crashes when ARM64_MODULE_PLTS is enabled:
> 
>   https://sourceware.org/bugzilla/show_bug.cgi?id=14592
> 
> To work around the problem, this change removes NOLOAD from .plt
> and .init.plt, which allows us to link modules with ld.gold.

Why don't we just not do LTO if the toolchain is busted? This feels like
it will end up being a game of whack-a-mole as code could be introduced
that tickles known bugs on older toolchains.

Will