linux-hardening - Re: [PATCH v8 05/14] x86: conditionally place regular ASM functions into separate sections

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Message-ID: <20211203163424.GK16608@worktop.programming.kicks-ass.net>
Date:   Fri, 3 Dec 2021 17:34:24 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexander Lobakin <alexandr.lobakin@...el.com>
Cc:     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>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Marios Pomonis <pomonis@...gle.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-arch@...r.kernel.org, live-patching@...r.kernel.org,
        llvm@...ts.linux.dev, hjl.tools@...il.com
Subject: Re: [PATCH v8 05/14] x86: conditionally place regular ASM functions
 into separate sections

On Fri, Dec 03, 2021 at 03:10:51PM +0100, Alexander Lobakin wrote:
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Fri, 3 Dec 2021 10:44:10 +0100
> 
> > On Thu, Dec 02, 2021 at 11:32:05PM +0100, Alexander Lobakin wrote:
> > > Use the newly introduces macros to create unique separate sections
> > > for (almost) every "regular" ASM function (i.e. for those which
> > > aren't explicitly put into a specific one).
> > > There should be no leftovers as input .text will be size-asserted
> > > in the LD script generated for FG-KASLR.
> > 
> > *groan*...
> > 
> > Please, can't we do something like:
> > 
> > #define SYM_PUSH_SECTION(name)	\
> > .if section == .text		\
> > .push_section .text.##name	\
> > .else				\
> > .push_section .text		\
> > .endif
> > 
> > #define SYM_POP_SECTION()	\
> > .pop_section
> > 
> > and wrap that inside the existing SYM_FUNC_START*() SYM_FUNC_END()
> > macros.
> 
> Ah I see. I asked about this in my previous mail and you replied
> already (: Cool stuff, I'll use it, it simplifies things a lot.

Note, I've no idea if it works. GAS and me aren't really on speaking
terms. It would be my luck for that to be totally impossible, hjl?