From:   Thomas Gleixner <tglx@linutronix.de>
To:     Rob Landley <rob@landley.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc:     Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Josh Poimboeuf <jpoimboe@kernel.org>
Subject: Re: [PATCH 2/5] X86-64 should not uniquely require a third ELF
 package to build.
In-Reply-To: <e184ece9-2779-675e-0c84-f0a62413c7fd@landley.net>
References: <b455394f-9faa-1f1a-f171-0b9d5e9ada35@landley.net>
 <e184ece9-2779-675e-0c84-f0a62413c7fd@landley.net>
Date:   Wed, 22 Feb 2023 00:12:26 +0100
Message-ID: <87wn4amx45.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Rob!

On Tue, Feb 21 2023 at 14:56, Rob Landley wrote:

The subject line is not compliant to documentation. Please read and
follow Documentation/process/* especially submitting-patches.rst and
maintainer-tip.rst

> x86-64 is the only architecture that can't compile without an extra
> ELF library installed on the host. (The kernel already has multiple ELF
> parse implementations built-in, so requiring another one is questionable
> at best.)

How are ELF parsers in the kernel itself related to a build requirement
for a tool, which is part of the kernel build process?

Next time you ask for removal of perl, python or whatever the kernel
requires to build.

> You can switch it back on in menuconfig if you want to, this
> just stops it being mandatory.

How do you switch on CONFIG_HAVE_OBJTOOL in menuconfig?

config HAVE_OBJTOOL
        bool

There is no knob.

> See https://lkml.iu.edu/hypermail/linux/kernel/2110.3/00402.html
> and https://lkml.iu.edu/hypermail/linux/kernel/2110.3/00278.html

Please use https://lore.kernel.org/lkml/ links.

> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 3604074a878b..b63510d79baf 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -243,7 +243,6 @@ config X86
>  	select HAVE_NOINSTR_HACK		if HAVE_OBJTOOL
>  	select HAVE_NMI
>  	select HAVE_NOINSTR_VALIDATION		if HAVE_OBJTOOL
> -	select HAVE_OBJTOOL			if X86_64

This prevents runtime features, optimizations, mitigations and build
time validations rom being selected as you can see from your patch
context.

Just to be clear: objtool is mandatory for x86_64 builds.

git grep 'select HAVE_OBJTOOL' will tell you that your claim about
x86_64 being the only architecture is slightly wrong.

Thanks,

        tglx