linux-kernel - Re: [PATCH 4/5] kbuild: unify vdso

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Message-ID: <ZScBJp-nen5wDRkT@bergen.fjasle.eu>
Date:   Wed, 11 Oct 2023 22:10:14 +0200
From:   Nicolas Schier <nicolas@...sle.eu>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-parisc@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, linux-um@...ts.infradead.org,
        loongarch@...ts.linux.dev, sparclinux@...r.kernel.org,
        x86@...nel.org, Albert Ou <aou@...s.berkeley.edu>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        Guo Ren <guoren@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Russell King <linux@...linux.org.uk>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        WANG Xuerui <kernel@...0n.name>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH 4/5] kbuild: unify vdso_install rules

On Mon 09 Oct 2023 21:42:09 GMT, Masahiro Yamada wrote:
> Currently, there is no standard implementation for vdso_install,
> leading to various issues:
> 
>  1. Code duplication
> 
>     Many architectures duplicate similar code just for copying files
>     to the install destination.
> 
>     Some architectures (arm, sparc, x86) create build-id symlinks,
>     introducing more code duplication.
> 
>  2. Accidental updates of in-tree build artifacts
> 
>     The vdso_install rule depends on the vdso files to install.
>     It may update in-tree build artifacts. This can be problematic,
>     as explained in commit 19514fc665ff ("arm, kbuild: make
>     "make install" not depend on vmlinux").
> 
>  3. Broken code in some architectures
> 
>     Makefile code is often copied from one architecture to another
>     without proper adaptation or testing.
> 
>     The previous commits removed broken code from csky, UML, and parisc.
> 
>     Another issue is that 'make vdso_install' for ARCH=s390 installs
>     vdso64, but not vdso32.
> 
> To address these problems, this commit introduces the generic vdso_install.
> 
> Architectures that support vdso_install need to define vdso-install-y
> in arch/*/Makefile.
> 
> vdso-install-y lists the files to install. For example, arch/x86/Makefile
> looks like this:
> 
>   vdso-install-$(CONFIG_X86_64)           += arch/x86/entry/vdso/vdso64.so.dbg
>   vdso-install-$(CONFIG_X86_X32_ABI)      += arch/x86/entry/vdso/vdsox32.so.dbg
>   vdso-install-$(CONFIG_X86_32)           += arch/x86/entry/vdso/vdso32.so.dbg
>   vdso-install-$(CONFIG_IA32_EMULATION)   += arch/x86/entry/vdso/vdso32.so.dbg
> 
> These files will be installed to $(MODLIB)/vdso/ with the .dbg suffix,
> if exists, stripped away.
> 
> vdso-install-y can optionally take the second field after the colon
> separator. This is needed because some architectures install vdso
> files as a different base name.
> 
> The following is a snippet from arch/arm64/Makefile.
> 
>   vdso-install-$(CONFIG_COMPAT_VDSO)      += arch/arm64/kernel/vdso32/vdso.so.dbg:vdso32.so
> 
> This will rename vdso.so.dbg to vdso32.so during installation. If such
> architectures change their implementation so that the file names match,
> this workaround will go away.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---

Thanks for cleaning this up!

Reviewed-by: Nicolas Schier <nicolas@...sle.eu>