From: Andy Lutomirski <luto@amacapital.net>
To: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: Brendan Shanks <bshanks@codeweavers.com>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>, X86 ML <x86@kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Andreas Rammhold <andi@notmuch.email>,
"Moger, Babu" <Babu.Moger@amd.com>
Subject: Re: [PATCH] x86/umip: Add emulation/spoofing for SLDT and STR instructions
Date: Wed, 3 Jun 2020 21:39:59 -0700 [thread overview]
Message-ID: <CALCETrXrvNZQUqfjF+-=jh1TMBpdB0PT-8J5wWDO83+i3B5Q1w@mail.gmail.com> (raw)
In-Reply-To: <20200604001243.GA24742@ranerica-svr.sc.intel.com>
On Wed, Jun 3, 2020 at 5:12 PM Ricardo Neri
<ricardo.neri-calderon@linux.intel.com> wrote:
>
> On Tue, Jun 02, 2020 at 11:42:12AM -0700, Brendan Shanks wrote:
> > Add emulation/spoofing of SLDT and STR for both 32- and 64-bit
> > processes.
> >
> > Wine users have found a small number of Windows apps using SLDT that
> > were crashing when run on UMIP-enabled systems.
> >
> > Reported-by: Andreas Rammhold <andi@notmuch.email>
> > Originally-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> > Signed-off-by: Brendan Shanks <bshanks@codeweavers.com>
> > ---
> > arch/x86/kernel/umip.c | 23 ++++++++++++++---------
> > 1 file changed, 14 insertions(+), 9 deletions(-)
> >
> > diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
> > index 8d5cbe1bbb3b..59dfceac5cc0 100644
> > --- a/arch/x86/kernel/umip.c
> > +++ b/arch/x86/kernel/umip.c
> > @@ -64,6 +64,8 @@
> > #define UMIP_DUMMY_GDT_BASE 0xfffffffffffe0000ULL
> > #define UMIP_DUMMY_IDT_BASE 0xffffffffffff0000ULL
> >
> > +#define UMIP_DUMMY_TASK_REGISTER_SELECTOR 0x40
> > +
> > /*
> > * The SGDT and SIDT instructions store the contents of the global descriptor
> > * table and interrupt table registers, respectively. The destination is a
> > @@ -244,16 +246,24 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst,
> > *data_size += UMIP_GDT_IDT_LIMIT_SIZE;
> > memcpy(data, &dummy_limit, UMIP_GDT_IDT_LIMIT_SIZE);
> >
> > - } else if (umip_inst == UMIP_INST_SMSW) {
> > - unsigned long dummy_value = CR0_STATE;
> > + } else if (umip_inst == UMIP_INST_SMSW || umip_inst == UMIP_INST_SLDT ||
> > + umip_inst == UMIP_INST_STR) {
> > + unsigned long dummy_value;
> > +
> > + if (umip_inst == UMIP_INST_SMSW)
> > + dummy_value = CR0_STATE;
> > + else if (umip_inst == UMIP_INST_STR)
> > + dummy_value = UMIP_DUMMY_TASK_REGISTER_SELECTOR;
> > + else
> > + dummy_value = 0;
>
> Perhaps you can return a non-zero value for SLDT if it has an LDT, as
> Andy had suggested. Maybe this can be implemented by looking at
> current->mm->context.ldt
>
> I guess the non-zero value can be (GDT_ENTRY_LDT*8).
You could probably even get away with always returning a nonzero
value. After all, an empty LDT is quite similar to no LDT.
--Andy
next prev parent reply other threads:[~2020-06-04 4:40 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-02 18:42 [PATCH] x86/umip: Add emulation/spoofing for SLDT and STR instructions Brendan Shanks
2020-06-04 0:12 ` Ricardo Neri
2020-06-04 4:39 ` Andy Lutomirski [this message]
[not found] ` <E32838F8-665E-488F-96E4-040DD7BDA284@codeweavers.com>
2020-06-05 22:42 ` Ricardo Neri
2020-06-08 18:13 ` Brendan Shanks
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