linux-kernel - Re: x86/fpu: Don't export __kernel_fpu

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Message-ID: <20190110131132.GC20217@kroah.com>
Date:   Thu, 10 Jan 2019 14:11:32 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Marc Dionne <marc.c.dionne@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        x86@...nel.org
Subject: Re: x86/fpu: Don't export __kernel_fpu_{begin,end}()

On Wed, Jan 09, 2019 at 06:09:35PM +0100, Sebastian Andrzej Siewior wrote:
> On 2019-01-09 17:52:35 [+0100], Greg Kroah-Hartman wrote:
> > If there are no in-kernel users, the symbols should not be exported
> > anymore.  That's nothing new, we have always done this.
> 
> The thing is that we had
>   EXPORT_SYMBOL(__kernel_fpu_begin)
>   EXPORT_SYMBOL_GPL(kernel_fpu_begin)
> 
> and now __kernel_fpu_begin() is no longer exported and static only.

Ok, that is fine.

> All in kernel user (including the kvm module) use kernel_fpu_begin()
> which is not available to proprietary modules. Hence Marc's mail.

But since when did out-of-tree modules use __kernel_fpu_begin?  It's an
x86-only thing, and shouldn't really be used by anyone, right?

> > > On the other hand could we just drop EXPORT_SYMBOL_GPL? I doubt this
> > > helps in any way yet please correct me if I am wrong. 
> > 
> > Yes, it helps, please leave it as-is.
> 
> As you say. I only notice that certain things used to work and then no
> longer do because due to $rework it somehow become EXPORT_SYMBOL_GPL
> only and people complain and we tend to switch the export back to
> EXPORT_SYMBOL.

That is a different topic than the whole _GPL symbol export at all.
Please don't conflate the two.

> I'm not aware of a case where it actually helped in anyway.

The use of the _GPL symbol exports has helped in numerous places over
the years.  I'd be glad to discuss details over a beverage sometime :)

thanks,

greg k-h