Date: Sun, 9 Sep 2012 14:02:55 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Michael Fuckner <michael@fuckner.net> Cc: amd64@freebsd.org, current@freebsd.org Subject: Re: Small Ivy features: FSGSBASE and SMEP. Message-ID: <20120909110255.GM33100@deviant.kiev.zoral.com.ua> In-Reply-To: <504C3A5D.4020402@fuckner.net> References: <20120908181019.GK33100@deviant.kiev.zoral.com.ua> <504C3A5D.4020402@fuckner.net>
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--fFCOmqB+j1dkVc7M Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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/specialreg.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. >=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 the > >values set by the arch syscall. Still, RDFSBASE/RDGSBASE might be useful > >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, but > >I did not tested the patch since I have no Ivy machine. > > > >I need your reports about boot on Ivy with patch applied. Please include > >the lines from verbose dmesg with CPU Features. In particular, the > >'Standard Extended Features' report should appear in output. > > > >Thanks. > > --fFCOmqB+j1dkVc7M Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAlBMd18ACgkQC3+MBN1Mb4glMwCdGhoZUpGm7pNrVtaWckOZDDOt tbYAnAlMmwTeFVMWTWYHd2LkiaSdI7oB =/M8M -----END PGP SIGNATURE----- --fFCOmqB+j1dkVc7M--
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