linux-kernel - Re: [PATCH v3] Makefile: lld: tell clang to use lld

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Message-ID: <CAGXu5jKZUP33Kz=nDPkUSj0Ksz5FOYTuuKAxv4N6xGEtFT645A@mail.gmail.com>
Date:   Fri, 5 Apr 2019 09:11:39 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nathan Lynch <nathan_lynch@...tor.com>
Subject: Re: [PATCH v3] Makefile: lld: tell clang to use lld

On Fri, Apr 5, 2019 at 3:17 AM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
> I want to propose alternative solution.
> Please check the attached patches.

In both patches:
> I changed the Makefile to use $(LD) rahter than $(CC). I confirmed
> the same vdso.so.raw was still produced.

typo: rahter -> rather

In the 0001 patch of arch/arm/vdso/Makefile:
> ...
> -VDSO_LDFLAGS += $(call cc-ldoption, -fuse-ld=bfd)
> +ldflags-y = -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
> +           -z max-page-size=4096 -z common-page-size=4096 \
> +           -nostdlib -shared \
> +           $(call ld-option, --hash-style=sysv) \
> +           $(call ld-option, --build-id) \
> +           -T

I see that "-fuse-ld=bfd" is explicitly dropped here, which could
reintroduce the problem fixed in d2b30cd4b722 ("ARM: 8384/1: VDSO:
force use of BFD linker") (and 3473f26592c1c). Does ld.gold still
exhibit this problem? If so, we'll need to detect gold and force bfd
still maybe?

-- 
Kees Cook