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 for kexec@lists.infradead.org; Wed, 15 Jan 2014 14:12:41 +0000
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Subject: Re: [PATCH] kexec.h: stop exporting kexec_load() to userspace
From: Paul Bolle <pebolle@tiscali.nl>
Date: Wed, 15 Jan 2014 15:12:18 +0100
In-Reply-To: <20140115133838.GD8101@stro.at>
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To: Maximilian Attems <max@stro.at>
Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Eric Biederman <ebiederm@xmission.com>, "H. Peter Anvin" <hpa@zytor.com>, Andrew Morton <akpm@linux-foundation.org>, Linus Torvalds <torvalds@linux-foundation.org>

On Wed, 2014-01-15 at 14:38 +0100, Maximilian Attems wrote:
> On Wed, Jan 15, 2014 at 02:17:04PM +0100, Paul Bolle wrote:
> > Since v3.5 kexec.h is exported to userspace. That includes its
> > declaration of kexec_load():
> >     extern int kexec_load(void *, size_t, struct kexec_segment *,
> >                    unsigned long int);
> > 
> > This declaration isn't very useful to userspace programs on itself. They
> > still have to define a matching function (which basically wraps the
> > kexec_load syscall). I'm not aware of programs or libraries that actually
> > do that.
> > 
> > It can be removed. The programs that actually use it, if there
> > are any, should then provide their own declaration to keep compiling.
> > Already compiled binaries will not be affected.
> 
> nack, klibc uses the header and there was some discussion that glibc
> could/should use it too.

The versions of klibc I stumbled on (via codesearch.debian.net) didn't
use a kexec_load() that match that declaration. Has that changed? In
which version?

>  I didn't follow kexec git, but there is/was
> a version that just uses the kexec_load() if the c library provides it.
> Until Santa Claus materialises in form of a direct kernel user-space API,
> see follow ups on http://lwn.net/Articles/534682/ and proposal by hpa
>  
> > This gets rid of the headers_check warning that can be seen ever since
> > this header was exported:
> >     [...]/usr/include/linux/kexec.h:49: userspace cannot reference function or variable defined in the kernel
> > 
> 
> this is the wrong  way of fix.


Paul Bolle


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