linux-kernel - Re: [PATCH] x86/kconfig/32: Mark CONFIG

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Date:	Thu, 9 Jul 2015 11:03:28 +0200
From:	Pavel Machek <pavel@....cz>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] x86/kconfig/32: Mark CONFIG_VM86 as BROKEN

On Wed 2015-07-08 16:00:48, Thomas Gleixner wrote:
> On Tue, 7 Jul 2015, Arjan van de Ven wrote:
> 
> > On 7/7/2015 6:25 PM, Andy Lutomirski wrote:
> > > VM86 is entirely broken if ptrace, syscall auditing, or NOHZ_FULL is
> > > in use.  The code is a big undocumented mess, it's a real PITA to
> > > test, and it looks like a big chunk of vm86_32.c is dead code.  It
> > > also plays awful games with the entry asm.
> > > 
> > > No one should be using it anyway.  Use DOSBOX or KVM instead.
> > > 
> > > Mark it BROKEN.  I want to remove some (obviously incorrect) exit
> > > asm that it depends on, and I don't want to figure out how to run
> > > severely obsolete programs just to test something that no one uses
> > > for anything other than exploits anyway.
> > > 
> > 
> > while it is never great to deprecate features, in this case I am not sure
> > there is another choice unless someone steps up to seriously revamp this code.
> > (and look at it from a PREEMPT, NO_HZ etc etc angle)
> 
> Aside of being broken in so many aspects it's even more obsolete than
> 386 support, we should just remove it right away.

Bad news for you:

vbetool-0.5/lrmi.c:#include <asm/vm86.h>
vbetool-0.5/lrmi.c:#include <sys/vm86.h>
vbetool-0.5/lrmi.c:#include <machine/vm86.h>
vbetool-0.5/lrmi.c:	    struct vm86_struct vm;
vbetool-0.5/lrmi.c:	    	   struct vm86_init_args init;
...
vbetool-0.5/lrmi.c:lrmi_vm86(struct vm86_struct *vm)
vbetool-0.5/lrmi.c:#define lrmi_vm86 vm86
vbetool-0.5/lrmi.c:	   fputs("vm86() failed\n", stderr);
vbetool-0.5/lrmi.c:run_vm86(void)
vbetool-0.5/lrmi.c:		vret = lrmi_vm86(&context.vm);
vbetool-0.5/lrmi.c:vm86_callback(int sig, int code, struct sigcontext
*sc)
vbetool-0.5/lrmi.c:vm86_callback(int sig, int code, struct sigcontext
*sc)
vbetool-0.5/lrmi.c:run_vm86(void)
vbetool-0.5/lrmi.c:		fprintf(stderr, "run_vm86: callback
already installed\n");

vbetool depends on it, and s2ram depends on vbetool. When we get
proper kernel drivers, this one will be solved, but it is not "more
obsolete than 386".

								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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