linux-kernel - Re: [PATCH] kcsan: fix debugfs initcall return type

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Date:   Fri, 14 May 2021 12:36:57 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Arnd Bergmann <arnd@...nel.org>, Marco Elver <elver@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] kcsan: fix debugfs initcall return type

On Fri, May 14, 2021 at 11:29:18AM -0700, Nathan Chancellor wrote:
> On 5/14/2021 7:00 AM, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@...db.de>
> > 
> > clang points out that an initcall funciton should return an 'int':
> > 
> > kernel/kcsan/debugfs.c:274:15: error: returning 'void' from a function with incompatible result type 'int'
> > late_initcall(kcsan_debugfs_init);
> > ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
> > include/linux/init.h:292:46: note: expanded from macro 'late_initcall'
> >   #define late_initcall(fn)               __define_initcall(fn, 7)
> > 
> > Fixes: e36299efe7d7 ("kcsan, debugfs: Move debugfs file creation out of early init")
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> 
> For the record, this requires CONFIG_LTO_CLANG to be visible.
> 
> Reviewed-by: Nathan Chancellor <nathan@...nel.org>

Queued with the three Reviewed-by tags, thank you all!

Nathan, I lost the thread on exactly what it is that requires that
CONFIG_LTO_CLANG be visible.  A naive reader might conclude that the
compiler diagnostic does not appear unless CONFIG_LTO_CLANG=y, but
that would be surprising (and yes, I have been surprised many times).
If you are suggesting that the commit log be upgraded, could you please
supply suggested wording?

Once this is nailed down (or by Wednesday if I hear no more), I will
rebase it to the bottom of the current kcsan stack, let it soak in -next
for a couple of days, then send to Linus as a fix for a regression.
Hopefully some time next week.

							Thanx, Paul

> > ---
> >   kernel/kcsan/debugfs.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/kcsan/debugfs.c b/kernel/kcsan/debugfs.c
> > index c1dd02f3be8b..e65de172ccf7 100644
> > --- a/kernel/kcsan/debugfs.c
> > +++ b/kernel/kcsan/debugfs.c
> > @@ -266,9 +266,10 @@ static const struct file_operations debugfs_ops =
> >   	.release = single_release
> >   };
> > -static void __init kcsan_debugfs_init(void)
> > +static int __init kcsan_debugfs_init(void)
> >   {
> >   	debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops);
> > +	return 0;
> >   }
> >   late_initcall(kcsan_debugfs_init);
> > 
>