Date: Tue, 30 Oct 2012 17:13:27 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: amd64@freebsd.org, current@freebsd.org Cc: avg@freebsd.org Subject: Re: Small Ivy features: FSGSBASE and SMEP. Message-ID: <20121030151327.GW73505@kib.kiev.ua> In-Reply-To: <20120909202905.GP33100@deviant.kiev.zoral.com.ua> References: <20120908181019.GK33100@deviant.kiev.zoral.com.ua> <504C3A5D.4020402@fuckner.net> <20120909110255.GM33100@deviant.kiev.zoral.com.ua> <20120909202905.GP33100@deviant.kiev.zoral.com.ua>
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--MUnXZt0Uv08c1hBe Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Sep 09, 2012 at 11:29:05PM +0300, Konstantin Belousov wrote: > On Sun, Sep 09, 2012 at 02:02:55PM +0300, Konstantin Belousov wrote: > > On Sun, Sep 09, 2012 at 08:42:37AM +0200, Michael Fuckner wrote: > > > Hi all, > > >=20 > > > I changed your patch slightly to apply to specialreh.h on STABLE > > >=20 > > > root@c64:/root # diff smep.1.patch.bak smep.1.patch > > > 80c80 > > > < diff --git a/sys/x86/include/specialreg.h b/sys/x86/include/special= reg.h > > > --- > > > > diff --git a/sys/amd64/include/specialreg.h=20 > > > b/sys/amd64/include/specialreg.h > > > 82,83c82,83 > > > < --- a/sys/x86/include/specialreg.h > > > < +++ b/sys/x86/include/specialreg.h > > > --- > > > > --- a/sys/amd64/include/specialreg.h > > > > +++ b/sys/amd64/include/specialreg.h > > >=20 > > > I got a new kernel, but it is stuck immediately (kerneltrap 9 with=20 > > > interrupts disabled), system doesn't boot on E3-1230 V2 on Supermicro= =20 > > > X9SCM-IIF > > >=20 > > > Anything else I could check? > > I need the backtrace and the whole kernel messages. > At least, there was a typo in the definition of CR4_FSGSBASE. > I still need verbose dmesg and panic messages, if any, with the > http://people.freebsd.org/~kib/misc/smep.2.patch=20 > version of the patch. >=20 With a help from Andrey, who has access to the hardware supporting SMEP, I fixed the issue with double-fault on SMEP enable. The issue was due to loader(8) making a handoff to the kernel with 1GB identity mapping which has the PG_U bit set. As a result, after enabling the CR4.SMEP, the #pf was generated immediately. But since the handler, if any, is also mapped with PG_U, double-fault happen and machine was reset. Updated patch, also fixing other minor problems with the features display, is at http://people.freebsd.org/~kib/misc/smep.3.patch . Please test. > >=20 > > >=20 > > > Regards, > > > Michael! > > >=20 > > >=20 > > > On 09/08/2012 08:10 PM, Konstantin Belousov wrote: > > > >Please find at > > > >http://people.freebsd.org/~kib/misc/smep.1.patch > > > >the patch which should enable the FSGSBASE and SMEP features > > > >supposedly present in the IvyBridge CPUs. > > > > > > > >FSGSBASE are four new instructions available in the 64bit mode only. > > > >They allow to access bases for %fs and %gs without touching MSRs. > > > >This makes it possible to both read and write bases in the user mode, > > > >or in ring 0 with lower overhead. > > > > > > > >At the moment, WRFSBASE/WRGSBASE instructions should work, but are > > > >useless since any interrupt or context switch overrides bases with t= he > > > >values set by the arch syscall. Still, RDFSBASE/RDGSBASE might be us= eful > > > >for some code and I see no reason not to enable them. > > > > > > > >SMEP is the nice feature of the processor which makes it trap if ring > > > >0 tries to execute an instruction from usermode-accessible page. It = is > > > >another mitigation for things like calling user-controllable function > > > >pointer in kernel, as well as a protection for NULL function pointer > > > >dereference. > > > > > > > >I am sure that we never execute anything in kernel from user page, b= ut > > > >I did not tested the patch since I have no Ivy machine. > > > > > > > >I need your reports about boot on Ivy with patch applied. Please inc= lude > > > >the lines from verbose dmesg with CPU Features. In particular, the > > > >'Standard Extended Features' report should appear in output. > > > > > > > >Thanks. > > > > >=20 >=20 --MUnXZt0Uv08c1hBe Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) iEYEARECAAYFAlCP7pYACgkQC3+MBN1Mb4i4XgCeMbWPn1gy9FTlpXgomSgRMzlm JRsAoNo07WO49h+wnpyaOHBAO9d0Fb0T =0ClT -----END PGP SIGNATURE----- --MUnXZt0Uv08c1hBe--
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