From: Konrad Rzeszutek Wilk <konrad@kernel.org>
To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: "H. Peter Anvin" <hpa@linux.intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Dave Jones <davej@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Jeremy Fitzhardinge <jeremy@goop.org>,
Rusty Russell <rusty@rustcorp.com.au>,
David Woodhouse <dwmw2@infradead.org>,
Vivek Goyal <vgoyal@in.ibm.com>,
Andres Salomon <dilinger@queued.net>,
Yinghai Lu <yhlu.kernel@gmail.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RFC PATCH] x86-32: Start out eflags and cr4 clean
Date: Wed, 26 Sep 2012 07:29:56 -0400 [thread overview]
Message-ID: <20120926112955.GA7356@phenom.dumpdata.com> (raw)
In-Reply-To: <1348580900.11229.19.camel@zakaz.uk.xensource.com>
On Tue, Sep 25, 2012 at 02:48:20PM +0100, Ian Campbell wrote:
> On Tue, 2012-09-25 at 00:27 +0100, H. Peter Anvin wrote:
> > From: "H. Peter Anvin" <hpa@linux.intel.com>
> >
> > %cr4 is supposed to reflect a set of features into which the operating
> > system is opting in. If the BIOS or bootloader leaks bits here, this
> > is not desirable. Consider a bootloader passing in %cr4.pae set to a
> > legacy paging kernel, for example -- it will not have any immediate
> > effect, but the kernel would crash when turning paging on.
> >
> > A similar argument applies to %eflags, and since we have to look for
> > %eflags.id being settable we can use a sequence which clears %eflags
> > as a side effect.
> >
> > Note that we already do this for x86-64.
> >
> > I would like opinions on this especially from the PV crowd
>
> Xen PV guests don't pass through this code path so there is no danger
> there AFAICT, so from that PoV:
>
> Acked-by: Ian Campbell <ian.campbell@citrix.com>
>
> FWIW it looks correct to me from the native PoV too, but you probably
> already knew that ;-)
And sanity testing confirmed it.
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>
> Ian.
>
>
> --
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>
next prev parent reply other threads:[~2012-09-26 11:41 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-21 19:43 [PATCH 00/11] x86: Supervisor Mode Access Prevention H. Peter Anvin
2012-09-21 19:43 ` [PATCH 01/11] x86, cpufeature: Add feature bit for SMAP H. Peter Anvin
2012-09-21 19:43 ` [PATCH 02/11] x86-32, mm: The WP test should be done on a kernel page H. Peter Anvin
2012-09-21 19:58 ` [tip:x86/smap] " tip-bot for H. Peter Anvin
2012-09-21 19:43 ` [PATCH 03/11] x86, smap: Add CR4 bit for SMAP H. Peter Anvin
2012-09-21 19:59 ` [tip:x86/smap] " tip-bot for H. Peter Anvin
2012-09-21 19:43 ` [PATCH 04/11] x86, alternative: Use .pushsection/.popsection H. Peter Anvin
2012-09-21 20:00 ` [tip:x86/smap] " tip-bot for H. Peter Anvin
2012-09-21 19:43 ` [PATCH 05/11] x86, alternative: Add header guards to <asm/alternative-asm.h> H. Peter Anvin
2012-09-21 20:01 ` [tip:x86/smap] x86, alternative: Add header guards to <asm/ alternative-asm.h> tip-bot for H. Peter Anvin
2012-09-21 19:43 ` [PATCH 06/11] x86, smap: Add a header file with macros for STAC/CLAC H. Peter Anvin
2012-09-21 20:02 ` [tip:x86/smap] x86, smap: Add a header file with macros for STAC/ CLAC tip-bot for H. Peter Anvin
2012-09-21 19:43 ` [PATCH 07/11] x86, uaccess: Merge prototypes for clear_user/__clear_user H. Peter Anvin
2012-09-21 20:03 ` [tip:x86/smap] x86, uaccess: Merge prototypes for clear_user/ __clear_user tip-bot for H. Peter Anvin
2012-09-21 19:43 ` [PATCH 08/11] x86, smap: Add STAC and CLAC instructions to control user space access H. Peter Anvin
2012-09-21 20:04 ` [tip:x86/smap] " tip-bot for H. Peter Anvin
2012-09-22 0:16 ` [tip:x86/smap] x86-32, smap: Add STAC/ CLAC instructions to 32-bit kernel entry tip-bot for H. Peter Anvin
2012-09-21 19:43 ` [PATCH 09/11] x86, smap: Turn on Supervisor Mode Access Prevention H. Peter Anvin
2012-09-21 20:05 ` [tip:x86/smap] " tip-bot for H. Peter Anvin
2012-09-21 19:43 ` [PATCH 10/11] x86, smap: A page fault due to SMAP is an oops H. Peter Anvin
2012-09-21 20:06 ` [tip:x86/smap] " tip-bot for H. Peter Anvin
2012-09-21 19:43 ` [PATCH 11/11] x86, smap: Reduce the SMAP overhead for signal handling H. Peter Anvin
2012-09-21 20:07 ` [tip:x86/smap] " tip-bot for H. Peter Anvin
2012-09-21 19:54 ` [PATCH 00/11] x86: Supervisor Mode Access Prevention Linus Torvalds
2012-09-21 19:57 ` H. Peter Anvin
2012-09-21 20:08 ` Ingo Molnar
2012-09-21 21:03 ` H. Peter Anvin
2012-09-21 21:09 ` Linus Torvalds
2012-09-21 21:12 ` H. Peter Anvin
2012-09-21 22:07 ` Eric W. Biederman
2012-09-21 22:12 ` H. Peter Anvin
2012-09-22 0:41 ` Eric W. Biederman
2012-09-24 23:27 ` [RFC PATCH] x86-32: Start out eflags and cr4 clean H. Peter Anvin
2012-09-25 13:27 ` Konrad Rzeszutek Wilk
2012-09-25 13:48 ` Ian Campbell
2012-09-26 11:29 ` Konrad Rzeszutek Wilk [this message]
2012-09-27 6:11 ` [tip:x86/smap] " tip-bot for H. Peter Anvin
2012-11-24 3:49 ` Yuhong Bao
2012-11-24 5:06 ` H. Peter Anvin
2012-09-27 6:11 ` [tip:x86/smap] x86, suspend: On wakeup always initialize cr4 and EFER tip-bot for H. Peter Anvin
2012-10-01 22:04 ` [tip:x86/urgent] x86, suspend: Correct the restore of CR4, EFER; skip computing EFLAGS.ID tip-bot for H. Peter Anvin
2012-10-02 6:52 ` tip-bot for H. Peter Anvin
2012-10-10 19:59 ` [RFC PATCH] x86-32: Start out eflags and cr4 clean Andres Salomon
2013-01-19 0:40 ` Andres Salomon
2013-01-19 0:42 ` H. Peter Anvin
2013-01-19 1:05 ` [Techteam] " Mitch Bradley
2013-01-19 2:35 ` H. Peter Anvin
2013-01-19 7:44 ` Mitch Bradley
2013-01-19 12:34 ` Daniel Drake
2013-01-19 19:15 ` [tip:x86/urgent] x86-32: Start out cr0 clean, disable paging before modifying cr3/4 tip-bot for H. Peter Anvin
2012-09-21 22:08 ` [PATCH 00/11] x86: Supervisor Mode Access Prevention Dave Jones
2012-09-21 22:10 ` H. Peter Anvin
2012-09-22 11:32 ` Ingo Molnar
2012-09-24 20:31 ` H. Peter Anvin
2012-09-24 20:43 ` Kees Cook
2012-09-24 20:51 ` H. Peter Anvin
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