From: Jann Horn <jannh@google.com>
To: sean.j.christopherson@intel.com
Cc: Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
dalias@libc.org, Dave Hansen <dave.hansen@linux.intel.com>,
jethro@fortanix.com, jarkko.sakkinen@linux.intel.com,
Florian Weimer <fweimer@redhat.com>,
Linux API <linux-api@vger.kernel.org>,
"the arch/x86 maintainers" <x86@kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
kernel list <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
nhorman@redhat.com, npmccallum@redhat.com, serge.ayoun@intel.com,
shay.katz-zamir@intel.com, linux-sgx@vger.kernel.org,
andriy.shevchenko@linux.intel.com,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
carlos@redhat.com, adhemerval.zanella@linaro.org
Subject: Re: RFC: userspace exception fixups
Date: Sat, 3 Nov 2018 00:27:34 +0100 [thread overview]
Message-ID: <CAG48ez1+nGDbuBaKJVPAOzEwiBkXqHHs7vmyAqvbeM42r0nFHg@mail.gmail.com> (raw)
Message-ID: <20181102232734.YS1PbK6_Bcs0ilfMR7FcZHNPUUMhYCfe57PSfmFio4M@z> (raw)
In-Reply-To: <20181102220437.GI7393@linux.intel.com>
On Fri, Nov 2, 2018 at 11:04 PM Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
> On Fri, Nov 02, 2018 at 08:02:23PM +0100, Jann Horn wrote:
> > On Fri, Nov 2, 2018 at 7:27 PM Sean Christopherson
> > <sean.j.christopherson@intel.com> wrote:
> > > On Fri, Nov 02, 2018 at 10:48:38AM -0700, Andy Lutomirski wrote:
> > > > This whole mechanism seems very complicated, and it's not clear
> > > > exactly what behavior user code wants.
> > >
> > > No argument there. That's why I like the approach of dumping the
> > > exception to userspace without trying to do anything intelligent in
> > > the kernel. Userspace can then do whatever it wants AND we don't
> > > have to worry about mucking with stacks.
> > >
> > > One of the hiccups with the VDSO approach is that the enclave may
> > > want to use the untrusted stack, i.e. the stack that has the VDSO's
> > > stack frame. For example, Intel's SDK uses the untrusted stack to
> > > pass parameters for EEXIT, which means an AEX might occur with what
> > > is effectively a bad stack from the VDSO's perspective.
> >
> > What exactly does "uses the untrusted stack to pass parameters for
> > EEXIT" mean? I guess you're saying that the enclave is writing to
> > RSP+[0...some_positive_offset], and the written data needs to be
> > visible to the code outside the enclave afterwards?
>
> As is, they actually do it the other way around, i.e. negative offsets
> relative to the untrusted %RSP. Going into the enclave there is no
> reserved space on the stack. The SDK uses EEXIT like a function call,
> i.e. pushing parameters on the stack and making an call outside of the
> enclave, hence the name out-call. This allows the SDK to handle any
> reasonable out-call without a priori knowledge of the application's
> maximum out-call "size".
But presumably this is bounded to be at most 128 bytes (the red zone
size), right? Otherwise this would be incompatible with
non-sigaltstack signal delivery.
next prev parent reply other threads:[~2018-11-02 23:28 UTC|newest]
Thread overview: 163+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-01 17:53 RFC: userspace exception fixups Andy Lutomirski
2018-11-01 17:53 ` Andy Lutomirski
2018-11-01 18:09 ` Florian Weimer
2018-11-01 18:09 ` Florian Weimer
2018-11-01 18:30 ` Rich Felker
2018-11-01 18:30 ` Rich Felker
2018-11-01 19:00 ` Jarkko Sakkinen
2018-11-01 19:00 ` Jarkko Sakkinen
2018-11-01 18:27 ` Rich Felker
2018-11-01 18:27 ` Rich Felker
2018-11-01 18:33 ` Jann Horn
2018-11-01 18:33 ` Jann Horn
2018-11-01 18:52 ` Rich Felker
2018-11-01 18:52 ` Rich Felker
2018-11-01 19:10 ` Linus Torvalds
2018-11-01 19:10 ` Linus Torvalds
2018-11-01 19:31 ` Rich Felker
2018-11-01 19:31 ` Rich Felker
2018-11-01 21:24 ` Linus Torvalds
2018-11-01 21:24 ` Linus Torvalds
2018-11-01 23:22 ` Andy Lutomirski
2018-11-01 23:22 ` Andy Lutomirski
2018-11-02 16:30 ` Sean Christopherson
2018-11-02 16:30 ` Sean Christopherson
2018-11-02 16:37 ` Jethro Beekman
2018-11-02 16:37 ` Jethro Beekman
2018-11-02 16:52 ` Sean Christopherson
2018-11-02 16:52 ` Sean Christopherson
2018-11-02 16:56 ` Jethro Beekman
2018-11-02 16:56 ` Jethro Beekman
2018-11-02 17:01 ` Andy Lutomirski
2018-11-02 17:01 ` Andy Lutomirski
2018-11-02 17:05 ` Jethro Beekman
2018-11-02 17:05 ` Jethro Beekman
2018-11-02 17:16 ` Andy Lutomirski
2018-11-02 17:16 ` Andy Lutomirski
2018-11-02 17:32 ` Rich Felker
2018-11-02 17:32 ` Rich Felker
2018-11-02 17:12 ` Sean Christopherson
2018-11-02 17:12 ` Sean Christopherson
2018-11-02 22:42 ` Jarkko Sakkinen
2018-11-02 22:42 ` Jarkko Sakkinen
2018-11-02 16:56 ` Dave Hansen
2018-11-02 16:56 ` Dave Hansen
2018-11-02 17:06 ` Sean Christopherson
2018-11-02 17:06 ` Sean Christopherson
2018-11-02 17:13 ` Dave Hansen
2018-11-02 17:13 ` Dave Hansen
2018-11-02 17:33 ` Sean Christopherson
2018-11-02 17:33 ` Sean Christopherson
2018-11-02 17:48 ` Andy Lutomirski
2018-11-02 17:48 ` Andy Lutomirski
2018-11-02 18:27 ` Sean Christopherson
2018-11-02 18:27 ` Sean Christopherson
2018-11-02 19:02 ` Jann Horn
2018-11-02 19:02 ` Jann Horn
2018-11-02 22:04 ` Sean Christopherson
2018-11-02 22:04 ` Sean Christopherson
2018-11-02 23:27 ` Jann Horn [this message]
2018-11-02 23:27 ` Jann Horn
2018-11-02 23:32 ` Andy Lutomirski
2018-11-02 23:32 ` Andy Lutomirski
2018-11-02 23:36 ` Jann Horn
2018-11-02 23:36 ` Jann Horn
2018-11-06 15:37 ` Sean Christopherson
2018-11-06 15:37 ` Sean Christopherson
2018-11-06 16:57 ` Andy Lutomirski
2018-11-06 16:57 ` Andy Lutomirski
2018-11-06 17:03 ` Dave Hansen
2018-11-06 17:03 ` Dave Hansen
2018-11-06 17:19 ` Sean Christopherson
2018-11-06 17:19 ` Sean Christopherson
2018-11-06 18:20 ` Andy Lutomirski
2018-11-06 18:20 ` Andy Lutomirski
2018-11-06 18:41 ` Dave Hansen
2018-11-06 18:41 ` Dave Hansen
2018-11-06 19:02 ` Andy Lutomirski
2018-11-06 19:02 ` Andy Lutomirski
2018-11-06 19:22 ` Dave Hansen
2018-11-06 19:22 ` Dave Hansen
2018-11-06 20:12 ` Andy Lutomirski
2018-11-06 20:12 ` Andy Lutomirski
2018-11-06 21:00 ` Dave Hansen
2018-11-06 21:00 ` Dave Hansen
2018-11-06 21:07 ` Andy Lutomirski
2018-11-06 21:07 ` Andy Lutomirski
2018-11-06 21:41 ` Andy Lutomirski
2018-11-06 21:41 ` Andy Lutomirski
2018-11-06 21:59 ` Sean Christopherson
2018-11-06 21:59 ` Sean Christopherson
2018-11-06 23:00 ` Andy Lutomirski
2018-11-06 23:00 ` Andy Lutomirski
2018-11-06 23:35 ` Sean Christopherson
2018-11-06 23:35 ` Sean Christopherson
2018-11-06 23:39 ` Andy Lutomirski
2018-11-06 23:39 ` Andy Lutomirski
2018-11-07 0:02 ` Sean Christopherson
2018-11-07 0:02 ` Sean Christopherson
2018-11-07 1:17 ` Andy Lutomirski
2018-11-07 1:17 ` Andy Lutomirski
2018-11-07 6:47 ` Jethro Beekman
2018-11-07 6:47 ` Jethro Beekman
2018-11-07 15:34 ` Sean Christopherson
2018-11-07 15:34 ` Sean Christopherson
2018-11-07 19:01 ` Sean Christopherson
2018-11-07 19:01 ` Sean Christopherson
2018-11-07 20:56 ` Dave Hansen
2018-11-07 20:56 ` Dave Hansen
2018-11-08 15:04 ` Jarkko Sakkinen
2018-11-08 15:04 ` Jarkko Sakkinen
2018-11-08 19:54 ` Sean Christopherson
2018-11-08 19:54 ` Sean Christopherson
2018-11-08 20:05 ` Andy Lutomirski
2018-11-08 20:05 ` Andy Lutomirski
2018-11-08 20:10 ` Dave Hansen
2018-11-08 20:10 ` Dave Hansen
2018-11-08 21:16 ` Sean Christopherson
2018-11-08 21:16 ` Sean Christopherson
2018-11-08 21:50 ` Dave Hansen
2018-11-08 21:50 ` Dave Hansen
2018-11-08 22:04 ` Sean Christopherson
2018-11-08 22:04 ` Sean Christopherson
2018-11-09 7:12 ` Christoph Hellwig
2018-11-09 7:12 ` Christoph Hellwig
2018-11-06 23:17 ` Rich Felker
2018-11-06 23:17 ` Rich Felker
2018-11-06 23:26 ` Sean Christopherson
2018-11-06 23:26 ` Sean Christopherson
2018-11-07 21:27 ` Rich Felker
2018-11-07 21:27 ` Rich Felker
2018-11-07 21:33 ` Andy Lutomirski
2018-11-07 21:33 ` Andy Lutomirski
2018-11-07 21:40 ` Sean Christopherson
2018-11-07 21:40 ` Sean Christopherson
2018-11-08 15:11 ` Jarkko Sakkinen
2018-11-08 15:11 ` Jarkko Sakkinen
2018-11-06 17:00 ` Dave Hansen
2018-11-06 17:00 ` Dave Hansen
2018-11-02 22:37 ` Jarkko Sakkinen
2018-11-02 22:37 ` Jarkko Sakkinen
2018-11-01 19:06 ` Linus Torvalds
2018-11-01 19:06 ` Linus Torvalds
2018-11-02 22:07 ` Jarkko Sakkinen
2018-11-02 22:07 ` Jarkko Sakkinen
2018-11-18 7:15 ` Jarkko Sakkinen
2018-11-18 7:18 ` Jarkko Sakkinen
2018-11-18 13:02 ` Jarkko Sakkinen
2018-11-19 5:17 ` Jethro Beekman
2018-11-19 14:05 ` Jarkko Sakkinen
2018-11-19 14:59 ` Jarkko Sakkinen
2018-11-19 15:29 ` Andy Lutomirski
2018-11-19 16:02 ` Jarkko Sakkinen
2018-11-19 17:00 ` Andy Lutomirski
2018-11-20 10:11 ` Jarkko Sakkinen
2018-11-20 15:19 ` Andy Lutomirski
2018-11-20 22:55 ` Jarkko Sakkinen
2018-11-21 5:17 ` Jethro Beekman
2018-11-21 15:17 ` Jarkko Sakkinen
2018-11-24 17:07 ` Jarkko Sakkinen
2018-11-26 14:35 ` Sean Christopherson
2018-11-26 22:06 ` Jarkko Sakkinen
2018-11-20 18:09 ` Sean Christopherson
2018-11-20 22:46 ` Jarkko Sakkinen
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