linux-kernel - Re: [PATCH 2/4] media: atomisp: Fix startup() section placement with -ffunction-sections

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Message-ID: <20251114085657.GR278048@noisy.programming.kicks-ass.net>
Date: Fri, 14 Nov 2025 09:56:57 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	live-patching@...r.kernel.org, Hans de Goede <hansg@...nel.org>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	linux-toolchains@...r.kernel.org
Subject: Re: [PATCH 2/4] media: atomisp: Fix startup() section placement with
 -ffunction-sections

On Wed, Nov 12, 2025 at 03:47:49PM -0800, Josh Poimboeuf wrote:
> When compiling the kernel with -ffunction-sections (e.g., for LTO,
> livepatch, dead code elimination, AutoFDO, or Propeller), the startup()
> function gets compiled into the .text.startup section.  In some cases it
> can even be cloned into .text.startup.constprop.0 or
> .text.startup.isra.0.
> 
> However, the .text.startup and .text.startup.* section names are already
> reserved for use by the compiler for __attribute__((constructor)) code.
> 

Urgh, that's a 'fun' one. Is this not a -ffunction-sections bug? I mean,
the compiler should never put regular non-reserved user symbols in a
section it has reserved for itself, right?