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

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Message-ID: <1AE3ED79-C094-46AE-B455-06199D5699DD@zytor.com>
Date: Fri, 06 Feb 2026 15:56:59 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: 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>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Indu Bhagat <indu.bhagat@...cle.com>
CC: 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 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.