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

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

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.