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Date: Mon, 2 Feb 2026 16:15:08 -0700
From: Nathan Chancellor <nathan@kernel.org>
To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= <thomas.weissschuh@linutronix.de>
Cc: Naman Jain <namjain@linux.microsoft.com>,
	Nicolas Schier <nsc@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@kernel.org>, 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>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Miguel Ojeda <ojeda@kernel.org>,
	Tamir Duberstein <tamird@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>, Kees Cook <kees@kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>, linux-kbuild@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	Saurabh Singh Sengar <ssengar@linux.microsoft.com>
Subject: Re: [RFC PATCH] kbuild: Make --build-id linker flag configurable
Message-ID: <20260202231508.GB2319189@ax162>
References: <20260202110631.978412-1-namjain@linux.microsoft.com>
 <20260202151101-d5558a6f-88d0-41dd-8816-18957a029ce8@linutronix.de>
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In-Reply-To: <20260202151101-d5558a6f-88d0-41dd-8816-18957a029ce8@linutronix.de>

On Mon, Feb 02, 2026 at 03:15:30PM +0100, Thomas Weißschuh wrote:
> On Mon, Feb 02, 2026 at 11:06:31AM +0000, Naman Jain wrote:
> > I am trying to implement reproducible builds for one of my product
> > kernel. I referred https://reproducible-builds.org/docs/build-path/
> > and tried to use both -fdebug-prefix-map=OLD=NEW and
> > -fmacro-prefix-map=OLD=NEW, but still could not achieve bit by bit
> > binary reproducibility without overwriting build-id to none. 
> > If I move the kernel to same path in other setup, I was able to create
> > same binary hash, however, without it, there is some difference in
> > build-id hash values.
> 
> Can you force the same build path during package building?
> That should avoid this issue.

Yeah, I think that it would be better to document this in
Documentation/kbuild/reproducible-builds.rst, as opposed to adding a
hack to disable the build ID altogether. It seems easy enough to make
the paths consistent between machines and environments by using a
container or such. The new scripts/container in -next could help there.

Cheers,
Nathan