linux-kernel - Re: [PATCH] kernel: mark all struct k

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Message-ID: <20170523044851.GA15761@lst.de>
Date:   Tue, 23 May 2017 06:48:51 +0200
From:   Christoph Hellwig <hch@....de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Christoph Hellwig <hch@....de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel: mark all struct k_clock instances const

On Tue, May 23, 2017 at 12:17:31AM +0200, Thomas Gleixner wrote:
> On Mon, 15 May 2017, Christoph Hellwig wrote:
> 
> > And keep a pointer to it instead of a copy in the posix_clocks array.
> > 
> > Based on similar changes in the Grsecurity patchset, but redone from
> > scratch including a few tweaks.
> 
> Hmm, that adds another level of indirection, but yes, we can do it.
> 
> > diff --git a/drivers/char/mmtimer.c b/drivers/char/mmtimer.c
> > index 0e7fcb04f01e..e501403dd860 100644
> > --- a/drivers/char/mmtimer.c
> > +++ b/drivers/char/mmtimer.c
> > @@ -53,7 +53,7 @@ MODULE_LICENSE("GPL");
> >  
> >  #define RTC_BITS 55 /* 55 bits for this implementation */
> >  
> > -static struct k_clock sgi_clock;
> > +static const struct k_clock sgi_clock;
> 
> Bah. This mmtimer which is used by 3 people in the world requires that we
> keep the register_clock() function around after init and even export it.

We can require the driver to be built into the kernel, which seems pretty
reasonable for a timer.  It's only selectable on IA64 anyway.