linux-kernel - RE: [PATCH v9] kallsyms: Add self-test facility

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Date:   Fri, 16 Dec 2022 16:57:54 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Steven Rostedt' <rostedt@...dmis.org>
CC:     'Andreas Schwab' <schwab@...ux-m68k.org>,
        "'Leizhen (ThunderTown)'" <thunder.leizhen@...wei.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        "Joe Lawrence" <joe.lawrence@...hat.com>,
        "live-patching@...r.kernel.org" <live-patching@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Luis Chamberlain" <mcgrof@...nel.org>,
        "linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Subject: RE: [PATCH v9] kallsyms: Add self-test facility

From: Steven Rostedt 
> Sent: 16 December 2022 16:53
> 
> On Fri, 16 Dec 2022 16:32:08 +0000
> David Laight <David.Laight@...LAB.COM> wrote:
> 
> > From: Andreas Schwab
> > > Sent: 16 December 2022 16:12
> > > On Dez 16 2022, David Laight wrote:
> > >
> > > > The other issue is a missing "memory" clobber.
> > >
> > > strcmp is a pure read-only operation.
> >
> > Still needs the memory clobber.
> 
> What memory is being modified?
> 
> I don't know m68k assembly, but I'm guessing the (%O)+ and the (%1)+ only
> modifies the register being used, and no memory is being touched.

Memory is being read so a clobber is needed to ensure that all pending
writes have been done.
Although, in this case, the memory being read is effectively
read only so nothing should be pending.

But it really does look like something is 'smelly' with the
constraints.

	David

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