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

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Message-ID: <20221216121947.7d03b651@gandalf.local.home>
Date:   Fri, 16 Dec 2022 12:19:47 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     David Laight <David.Laight@...LAB.COM>
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

On Fri, 16 Dec 2022 16:57:54 +0000
David Laight <David.Laight@...LAB.COM> wrote:

> > 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

I would think that if the memory being read is the address of what the
input parameters being passed into it are, then the compiler should be
smart enough to know that there's a relation. Especially if the input
parameters are pointers.

I assumed that "memory" was for memory unrelated to the input constraints.

-- Steve