linux-kernel - Re: [PATCH] mips: vdso: Allow passing build path options

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Date:   Wed, 8 Jun 2022 11:11:31 +0200
From:   Alexander Sverdlin <alexander.sverdlin@...ia.com>
To:     Matija Glavinic Pecotic <matija.glavinic-pecotic.ext@...ia.com>,
        linux-mips@...r.kernel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Nemanja Rakovic <nemanja.rakovic@...mia.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mips: vdso: Allow passing build path options

Hello Matija, Thomas,

On 04/04/2022 10:36, Matija Glavinic Pecotic wrote:
> vdso image is not reproducible in different build directories as build
> path defines vdso image contents via .notes, build ID. Build ID is
> hashed across all sections (prior stripping), debug sections included.
> With debug sections containing build paths, hash is impacted. Finally
> vmlinux is not reproducible as it will differ in vdso_data.
> 
> For users wanting reproducible builds, irrespective of build path, it
> is unwanted behavior. Issue is sorted out by passing related options
> via KAFLAGS, KCFLAGS, however due to mips' picking out specific/subset
> options, these are not getting passed through.
> 
> Allow related option to be taken if user specified them.
> 
> Signed-off-by: Matija Glavinic Pecotic <matija.glavinic-pecotic.ext@...ia.com>

Reviewed-by: Alexander Sverdlin <alexander.sverdlin@...ia.com>

> ---
>  arch/mips/vdso/Makefile | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
> index f72658b3a53f..b8296ef2bfcf 100644
> --- a/arch/mips/vdso/Makefile
> +++ b/arch/mips/vdso/Makefile
> @@ -35,8 +35,12 @@ cflags-vdso := $(ccflags-vdso) \
>  	-O3 -g -fPIC -fno-strict-aliasing -fno-common -fno-builtin -G 0 \
>  	-mrelax-pic-calls $(call cc-option, -mexplicit-relocs) \
>  	-fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
> -	$(call cc-option, -fno-asynchronous-unwind-tables)
> +	$(call cc-option, -fno-asynchronous-unwind-tables) \
> +	$(filter -ffile-prefix-map%,$(KBUILD_CFLAGS)) \
> +	$(filter -fmacro-prefix-map%,$(KBUILD_CFLAGS)) \
> +	$(filter -fdebug-prefix-map%,$(KBUILD_CFLAGS))
>  aflags-vdso := $(ccflags-vdso) \
> +	$(filter --debug-prefix-map%,$(KBUILD_AFLAGS)) \
>  	-D__ASSEMBLY__ -Wa,-gdwarf-2
>  
>  ifneq ($(c-gettimeofday-y),)

-- 
Best regards,
Alexander Sverdlin.