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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
	Andrew Lutomirski <luto@kernel.org>, Jann Horn <jannh@google.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Rich Felker <dalias@libc.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Jethro Beekman <jethro@fortanix.com>,
	"Jarkko Sakkinen" <jarkko.sakkinen@linux.intel.com>,
	Florian Weimer <fweimer@redhat.com>,
	Linux API <linux-api@vger.kernel.org>, X86 ML <x86@kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>, <nhorman@redhat.com>,
	<npmccallum@redhat.com>, "Ayoun, Serge" <serge.ayoun@intel.com>,
	<shay.katz-zamir@intel.com>, <linux-sgx@vger.kernel.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"Carlos O'Donell" <carlos@redhat.com>,
	<adhemerval.zanella@linaro.org>
Subject: Re: RFC: userspace exception fixups
Date: Thu, 8 Nov 2018 13:16:00 -0800	[thread overview]
Message-ID: <20181108211600.GA17167@linux.intel.com> (raw)
In-Reply-To: <7027c3dc-addb-1b96-027e-a57fccf1f812@intel.com>

On Thu, Nov 08, 2018 at 12:10:30PM -0800, Dave Hansen wrote:
> On 11/8/18 12:05 PM, Andy Lutomirski wrote:
> > Hmm.  The idea being that the SDK preserves RBP but not RSP.  That's
> > not the most terrible thing in the world.  But could the SDK live with
> > something more like my suggestion where the vDSO supplies a normal
> > function that takes a struct containing registers that are visible to
> > the enclave?  This would make it extremely awkward for the enclave to
> > use the untrusted stack per se, but it would make it quite easy (I
> > think) for the untrusted part of the SDK to allocate some extra memory
> > and just tell the enclave that *that* memory is the stack.
> 
> I really think the enclave should keep its grubby mitts off the
> untrusted stack.  There are lots of ways to get memory, even with
> stack-like semantics, that don't involve mucking with the stack itself.
> 
> I have not heard a good, hard argument for why there is an absolute
> *need* to store things on the actual untrusted stack.

Convenience and performance are the only arguments I've heard, e.g. so
that allocating memory doesn't require an extra EEXIT->EENTER round trip.

> We could quite easily have the untrusted code just promise to allocate a
> stack-sized virtual area (even derived from the stack rlimit size) and
> pass that into the enclave for parameter use.

I agree more and more the further I dig.  AFAIK there is no need to for
the enclave to actually load %rsp.  The initial EENTER can pass in the
base/top of the pseudo-stack and from there the enclave can manage it
purely in software.

WARNING: multiple messages have this Message-ID (diff)
From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
	Andrew Lutomirski <luto@kernel.org>, Jann Horn <jannh@google.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Rich Felker <dalias@libc.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Jethro Beekman <jethro@fortanix.com>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	Florian Weimer <fweimer@redhat.com>,
	Linux API <linux-api@vger.kernel.org>, X86 ML <x86@kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	nhorman@redhat.com, npmccallum@redhat.com, "Ayoun,
	Serge" <serge.ayoun@intel.com>,
	shay.katz-zamir@intel.com, linux-sgx@vger.kernel.org,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Carlos O'Donell <carlos@redhat.com>,
	adhemerval.zanella@linaro.org
Subject: Re: RFC: userspace exception fixups
Date: Thu, 8 Nov 2018 13:16:00 -0800	[thread overview]
Message-ID: <20181108211600.GA17167@linux.intel.com> (raw)
Message-ID: <20181108211600.MH9dKZtGoKuzS9OMBQiGsHoLzb07YndIV99k-Nav3xY@z> (raw)
In-Reply-To: <7027c3dc-addb-1b96-027e-a57fccf1f812@intel.com>

On Thu, Nov 08, 2018 at 12:10:30PM -0800, Dave Hansen wrote:
> On 11/8/18 12:05 PM, Andy Lutomirski wrote:
> > Hmm.  The idea being that the SDK preserves RBP but not RSP.  That's
> > not the most terrible thing in the world.  But could the SDK live with
> > something more like my suggestion where the vDSO supplies a normal
> > function that takes a struct containing registers that are visible to
> > the enclave?  This would make it extremely awkward for the enclave to
> > use the untrusted stack per se, but it would make it quite easy (I
> > think) for the untrusted part of the SDK to allocate some extra memory
> > and just tell the enclave that *that* memory is the stack.
> 
> I really think the enclave should keep its grubby mitts off the
> untrusted stack.  There are lots of ways to get memory, even with
> stack-like semantics, that don't involve mucking with the stack itself.
> 
> I have not heard a good, hard argument for why there is an absolute
> *need* to store things on the actual untrusted stack.

Convenience and performance are the only arguments I've heard, e.g. so
that allocating memory doesn't require an extra EEXIT->EENTER round trip.

> We could quite easily have the untrusted code just promise to allocate a
> stack-sized virtual area (even derived from the stack rlimit size) and
> pass that into the enclave for parameter use.

I agree more and more the further I dig.  AFAIK there is no need to for
the enclave to actually load %rsp.  The initial EENTER can pass in the
base/top of the pseudo-stack and from there the enclave can manage it
purely in software.

  parent reply	other threads:[~2018-11-08 21:16 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
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 [this message]
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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