linux-kernel - Re: [PATCH V4 01/20] rv: Add Runtime Verification (RV) interface

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Message-ID: <YsXMEeqGr2vdJCa7@casper.infradead.org>
Date:   Wed, 6 Jul 2022 18:53:21 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Tao Zhou <tao.zhou@...ux.dev>
Cc:     Daniel Bristot de Oliveira <bristot@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Gabriele Paoloni <gpaoloni@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Clark Williams <williams@...hat.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-trace-devel@...r.kernel.org
Subject: Re: [PATCH V4 01/20] rv: Add Runtime Verification (RV) interface

On Thu, Jul 07, 2022 at 01:49:02AM +0800, Tao Zhou wrote:
> > +struct rv_monitor {
> > +	const char		*name;
> > +	const char		*description;
> > +	bool			enabled;
> 
> Can the 'bool enabled;' be put at the end like the definition of
> structure rv_monitor_def. If '8+8+sizeof(bool)+8+8+8' not the same
> as '8+8+8+8+8+sizeof(bool)', I mean is it possible that after the
> end of stucture there is a int or char not require to align to 8 as
> an example from my nonsense.

That will make no difference at all.  C doesn't allow other variables
to "fill in the hole" at the end of the structure like that.  For
example, one could legitimately do 'memset(&rvm, sizeof(rvm))',
and that would wipe out those other variables as well.