linux-kernel - Re: [RFC][PATCH] objtool,x86_64: Replace recordmcount with objtool

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: <CABCJKufW8rYG-R7b=ad8E5oRd+1xrVknWcTd2VFuvE7=SPtoTA@mail.gmail.com>
Date:   Wed, 22 Jul 2020 13:03:12 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Will Deacon <will@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kbuild <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
        X86 ML <x86@...nel.org>, Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [RFC][PATCH] objtool,x86_64: Replace recordmcount with objtool

On Wed, Jul 22, 2020 at 12:09 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Wed, 22 Jul 2020 20:41:37 +0200
> Peter Zijlstra <peterz@...radead.org> wrote:
>
> > > That said, Andi Kleen added an option to gcc called -mnop-mcount which
> > > will have gcc do both create the mcount section and convert the calls
> > > into nops. When doing so, it defines CC_USING_NOP_MCOUNT which will
> > > tell ftrace to expect the calls to already be converted.
> >
> > That seems like the much easier solution, then we can forget about
> > recordmcount / objtool entirely for this.
>
> Of course that was only for some gcc compilers, and I'm not sure if
> clang can do this.
>
> Or do you just see all compilers doing this in the future, and not
> worrying about record-mcount at all, and bothering with objtool?

Clang appears to only support -mrecord-mcount and -mnop-mcount for
s390, so we still need recordmcount / objtool for x86.

Sami