linux-kernel - Re: [PATCH 20/22] x86,word-at-a-time: Remove .fixup usage

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YYuogZ+2Dnjyj1ge@hirez.programming.kicks-ass.net>
Date:   Wed, 10 Nov 2021 12:09:53 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Bill Wendling <morbo@...gle.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "seanjc@...gle.com" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "mbenes@...e.cz" <mbenes@...e.cz>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
        "linux-toolchains@...r.kernel.org" <linux-toolchains@...r.kernel.org>
Subject: Re: [PATCH 20/22] x86,word-at-a-time: Remove .fixup usage

On Wed, Nov 10, 2021 at 10:46:42AM +0000, David Laight wrote:
> From: Peter Zijlstra
> > Sent: 09 November 2021 21:08
> ...
> > 
> > GCC does the same, but I wanted to have the exception stuff be in
> > .text.cold, but alas it doesn't do that. I left the attribute because of
> > it's descriptive value.
> > 
> > >  Unless the cold attribute is helping move
> > > ("shrink-wrap"?) the basic block to a whole other section
> > > (.text.cold.)?
> > 
> > I was hoping it would do that, but it doesn't on gcc-11.
> 
> Wouldn't moving part of a function to .text.cold (or .text.unlikely)
> generate the same problems with the stack backtrace code as the
> .text.fixup section you are removing had??

GCC can already split a function into func and func.cold today (or
worse: func, func.isra.N, func.cold, func.isra.N.cold etc..).

I'm assuming reliable unwind and livepatch know how to deal with this.