linux-kernel - Re: [RFC] Don't create sframes during build

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Message-ID: <20250904163404.QMU7nfbA@linutronix.de>
Date: Thu, 4 Sep 2025 18:34:04 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Matthias Klose <doko@...ian.org>
Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-kbuild@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	Binutils <binutils@...rceware.org>
Subject: Re: [RFC] Don't create sframes during build

On 2025-09-04 16:02:42 [+0200], Matthias Klose wrote:
> [ CCing binutils@...rceware.org ]
> 
> On 9/4/25 15:18, Sebastian Andrzej Siewior wrote:
> > Hi,
> > 
> > gcc in Debian, starting with 15.2.0-2, 14.3.0-6 enables sframe
> > generation. Unless options like -ffreestanding are passed. Since this
> > isn't done, there are a few warnings during compile
> 
> If there are other options when sframe shouldn't be enabled, please tell.

No, I think this is okay.

…
> > We could drop the sframe during the final link but this does not get rid
> > of the objtool warnings so we would have to ignore them. But we don't
> > need it. So what about the following:
> > 
> > diff --git a/Makefile b/Makefile
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -886,6 +886,8 @@ ifdef CONFIG_CC_IS_GCC
> >   KBUILD_CFLAGS	+= $(call cc-option,--param=allow-store-data-races=0)
> >   KBUILD_CFLAGS	+= $(call cc-option,-fno-allow-store-data-races)
> >   endif
> > +# No sframe generation for kernel if enabled by default
> > +KBUILD_CFLAGS	+= $(call cc-option,-Xassembler --gsframe=no)
> >   ifdef CONFIG_READABLE_ASM
> >   # Disable optimizations that make assembler listings hard to read.
> This is what I chose for package builds that need disablement of sframe.

I think this would work for now. Longterm we would have to allow sframe
creation and keep section if an architecture decides to use it for its
backtracing. While orc seems fine on x86, there are arm64 patches to use
for as a stack unwinder.

Sebastian