linux-kernel - Re: [PATCH v9 05/15] x86: support ASM function sections

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Date:   Wed, 26 Jan 2022 15:49:52 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        linux-hardening@...r.kernel.org, x86@...nel.org,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Kristen Carlson Accardi <kristen@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Ard Biesheuvel <ardb@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Bruce Schlobohm <bruce.schlobohm@...el.com>,
        Jessica Yu <jeyu@...nel.org>,
        kernel test robot <lkp@...el.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Evgenii Shatokhin <eshatokhin@...tuozzo.com>,
        Jonathan Corbet <corbet@....net>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
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        Josh Poimboeuf <jpoimboe@...hat.com>,
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        Masami Hiramatsu <mhiramat@...nel.org>,
        Marios Pomonis <pomonis@...gle.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Nicolas Pitre <nico@...xnic.net>,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-arch@...r.kernel.org, live-patching@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH v9 05/15] x86: support ASM function sections

From: Borislav Petkov <bp@...en8.de>
Date: Fri, 21 Jan 2022 16:08:17 +0100

> On Thu, Dec 23, 2021 at 01:21:59AM +0100, Alexander Lobakin wrote:
> > Address places which need special care and enable
> > CONFIG_ARCH_SUPPORTS_ASM_FUNCTION_SECTIONS.
> > 
> > Notably:
> >  - propagate --sectname-subst to aflags in x86/boot/Makefile and
> >    x86/boot/compressed/Makefile as both override aflags;
> 
> s/aflags/KBUILD_AFLAGS/
> 
> Let's be more precise pls.
> 
> >  - symbols starting with a dot (like ".Lbad_gs") should be handled
> >    manually with SYM_*_START_SECT(.Lbad_gs, bad_gs) as "two dots"
> >    is a special (and CPP doesn't want to concatenate two dots in
> >    general);
> >  - some symbols explicitly need to reside in one section (like
> >    kexec control code, hibernation page etc.);
> >  - macros creating aliases for functions (like __memcpy() for
> >    memcpy() etc.) should go after the main declaration (as
> >    aliases should be declared in the same section and they
> >    don't have SYM_PUSH_SECTION() inside);
> >  - things like ".org", ".align" should be manually pushed to
> >    the same section the next symbol goes to;
> >  - expand indirect_thunk and .fixup wildcards in vmlinux.lds.S
> 
> $ git grep -E "\.fixup" arch/x86/*.S
> $
> 
> I guess I'll continue with your new version since a bunch of stuff
> has changed in arch/x86/ in the meantime so that that set would need
> refreshing.

Yeah, sure. .fixup usage was removed in particular.
I'll queue v10 soon.

> 
> Thx.
> 
> -- 
> Regards/Gruss,
>     Boris.

Thanks for the reviews,
Al

> 
> https://people.kernel.org/tglx/notes-about-netiquette