linux-kernel - Re: [PATCH v2] Makefile: fix GDB warning with CONFIG

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Date:   Wed, 26 May 2021 18:09:04 +0100
From:   Will Deacon <will@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Lee Jones <lee.jones@...aro.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Fangrui Song <maskray@...gle.com>,
        Elliot Berman <eberman@...cinc.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCH v2] Makefile: fix GDB warning with CONFIG_RELR

On Fri, May 21, 2021 at 06:26:24PM -0700, Nick Desaulniers wrote:
> GDB produces the following warning when debugging kernels built with
> CONFIG_RELR:
> 
> BFD: /android0/linux-next/vmlinux: unknown type [0x13] section `.relr.dyn'
> 
> when loading a kernel built with CONFIG_RELR into GDB. It can also
> prevent debugging symbols using such relocations.
> 
> Peter sugguests:
>   [That flag] means that lld will use dynamic tags and section type
>   numbers in the OS-specific range rather than the generic range. The
>   kernel itself doesn't care about these numbers; it determines the
>   location of the RELR section using symbols defined by a linker script.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1057
> Suggested-by: Peter Collingbourne <pcc@...gle.com>
> Reviewed-by: Nathan Chancellor <nathan@...nel.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
> Changes V1 -> V2:
> * rebase
> * pick up Nathan's reviewed by tag.
> 
>  Makefile                      | 2 +-
>  scripts/tools-support-relr.sh | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)

Does lld support RELR relocations for any architectures other than arm64? If
so, is the "--use-android-relr-tags" option supported on all of those as
well?

Will