linux-kernel - Re: [PATCH v7 6/6] x86/vdso: Enable sframe generation in VDSO

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Message-ID: <h34g66ujiebhuxzcqo4hg4zq2mbpbh5c3u7b7qlznaqxxwpczf@3kwv2wydbuiq>
Date: Fri, 6 Feb 2026 16:48:37 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Jens Remus <jremus@...ux.ibm.com>, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org, x86@...nel.org, linux-mm@...ck.org, 
	Steven Rostedt <rostedt@...nel.org>, Indu Bhagat <indu.bhagat@...cle.com>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Andrii Nakryiko <andrii@...nel.org>, 
	"Jose E. Marchesi" <jemarch@....org>, Beau Belgrave <beaub@...ux.microsoft.com>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Florian Weimer <fweimer@...hat.com>, Kees Cook <kees@...nel.org>, 
	Carlos O'Donell <codonell@...hat.com>, Sam James <sam@...too.org>, Dylan Hatch <dylanbhatch@...gle.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	David Hildenbrand <david@...hat.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Michal Hocko <mhocko@...e.com>, Mike Rapoport <rppt@...nel.org>, 
	Suren Baghdasaryan <surenb@...gle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, 
	"Steven Rostedt (Google)" <rostedt@...dmis.org>
Subject: Re: [PATCH v7 6/6] x86/vdso: Enable sframe generation in VDSO

On Fri, Feb 06, 2026 at 03:56:59PM -0800, H. Peter Anvin wrote:
> On February 6, 2026 9:48:24 AM PST, Jens Remus <jremus@...ux.ibm.com> wrote:
> >On 2/4/2026 1:49 AM, H. Peter Anvin wrote:
> >> On 2026-02-03 09:19, Jens Remus wrote:
> >>> -
> >>> +#if defined(__x86_64__) && defined(CONFIG_AS_SFRAME)
> >
> >My understanding is that you would like above changed to:
> >
> >#ifdef CONFIG_AS_SFRAME
> >
> >>> +	.cfi_sections .eh_frame, .debug_frame, .sframe
> >>> +#else
> >>>  	.cfi_sections .eh_frame, .debug_frame
> >>> +#endif
> >>>  
> >> 
> >> It would be better to:
> >> 
> >> #undef CONFIG_AS_SFRAME	/* i386 doesn't support .sframe */
> >> 
> >> in fake_32bit_build.h.
> >Due to (binutils 2.46 pre-release) GNU assembler supporting --gsframe-3,
> >but only for x86-64 not for x86-32 (nor x32) CONFIG_AS_SFRAME is enabled
> >even for my i386 cross build attempt.  This then wrongly causes the
> >.cfi_sections with .sframe to be selected (verified by adding an #error
> >for testing).
> >
> >IIUC the .cfi_sections is there to have DWARF in both .eh_frame and
> >.debug_frame.  For .sframe it basically has the same effect as
> >specifying the common assembler option --gsframe.  Given the more
> >specific option --gsframe-3 is explicitly specified I think it would
> >be better to drop the changes to both dwarf2.h and fake_32bit_build.h
> >and solely rely on --gsframe-3.
> >
> >Josh, Indu, do you agree?
> >
> >Thanks and rRegards,
> >Jens
> 
> Seems a lot cleaner to me, too, assuming it actually works.

+1

-- 
Josh