Re: [PATCH v2] Makefile: fix GDB warning with CONFIG_RELR

From: Will Deacon <will@kernel.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	Lee Jones <lee.jones@linaro.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Fangrui Song <maskray@google.com>,
	Elliot Berman <eberman@quicinc.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	Peter Collingbourne <pcc@google.com>,
	Michal Marek <michal.lkml@markovi.net>,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	Nathan Chancellor <nathan@kernel.org>
Subject: Re: [PATCH v2] Makefile: fix GDB warning with CONFIG_RELR
Date: Wed, 26 May 2021 18:09:04 +0100	[thread overview]
Message-ID: <20210526170904.GB19831@willie-the-truck> (raw)
In-Reply-To: <20210522012626.2811297-1-ndesaulniers@google.com>

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@google.com>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.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