From: Sean Christopherson <sean.j.christopherson@intel.com> To: Dave Hansen <dave.hansen@intel.com> Cc: Andy Lutomirski <luto@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Rich Felker <dalias@libc.org>, Jann Horn <jannh@google.com>, 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: Fri, 2 Nov 2018 10:33:50 -0700 [thread overview] Message-ID: <20181102173350.GF7393@linux.intel.com> (raw) In-Reply-To: <a4d2b3ec-43ec-f062-e180-c6e5a0d9fab8@intel.com> On Fri, Nov 02, 2018 at 10:13:23AM -0700, Dave Hansen wrote: > On 11/2/18 10:06 AM, Sean Christopherson wrote: > > On Fri, Nov 02, 2018 at 09:56:44AM -0700, Dave Hansen wrote: > >> On 11/2/18 9:30 AM, Sean Christopherson wrote: > >>> What if rather than having userspace register an address for fixup, the > >>> kernel instead unconditionally does fixup on the ENCLU opcode? > >> > >> The problem is knowing what to do for the fixup. If we have a simple > >> action to take that's universal, like backing up %RIP, or setting some > >> other register state, it's not bad. > > > > Isn't the EENTER/RESUME behavior universal? Or am I missing something? > > Could someone write down all the ways we get in and out of the enclave? > > I think we always get in from userspace calling EENTER or ERESUME. We > can't ever enter directly from the kernel, like via an IRET from what I > understand. Correct, the only way to get into the enclave is EENTER or ERESUME. My understanding is that even SMIs bounce through the AEX target before transitioning to SMM. > We get *out* from exceptions, hardware interrupts, or enclave-explicit > EEXITs. Did I miss any? Remind me where the hardware lands the control > flow in each of those exit cases. And VMExits. There are basically two cases: EEXIT and everything else. EEXIT is a glorified indirect jump, e.g. %RBX holds the target %RIP. Everything else is an Asynchronous Enclave Exit (AEX). On an AEX, %RIP is set to a value specified by EENTER/ERESUME, %RBP and %RSP are restored to pre-enclave values and all other registers are loaded with synthetic state. The actual interrupt/exception/VMExit then triggers, e.g. the %RIP on the stack for an exception is always the AEX target, not the %RIP inside the enclave that actually faulted.
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@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Rich Felker <dalias@libc.org>, Jann Horn <jannh@google.com>, 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: Fri, 2 Nov 2018 10:33:50 -0700 [thread overview] Message-ID: <20181102173350.GF7393@linux.intel.com> (raw) Message-ID: <20181102173350.w9CyaVgxSj-3rhkJZw3hdgAj9Mkd_fx_-pV2xqyNqYI@z> (raw) In-Reply-To: <a4d2b3ec-43ec-f062-e180-c6e5a0d9fab8@intel.com> On Fri, Nov 02, 2018 at 10:13:23AM -0700, Dave Hansen wrote: > On 11/2/18 10:06 AM, Sean Christopherson wrote: > > On Fri, Nov 02, 2018 at 09:56:44AM -0700, Dave Hansen wrote: > >> On 11/2/18 9:30 AM, Sean Christopherson wrote: > >>> What if rather than having userspace register an address for fixup, the > >>> kernel instead unconditionally does fixup on the ENCLU opcode? > >> > >> The problem is knowing what to do for the fixup. If we have a simple > >> action to take that's universal, like backing up %RIP, or setting some > >> other register state, it's not bad. > > > > Isn't the EENTER/RESUME behavior universal? Or am I missing something? > > Could someone write down all the ways we get in and out of the enclave? > > I think we always get in from userspace calling EENTER or ERESUME. We > can't ever enter directly from the kernel, like via an IRET from what I > understand. Correct, the only way to get into the enclave is EENTER or ERESUME. My understanding is that even SMIs bounce through the AEX target before transitioning to SMM. > We get *out* from exceptions, hardware interrupts, or enclave-explicit > EEXITs. Did I miss any? Remind me where the hardware lands the control > flow in each of those exit cases. And VMExits. There are basically two cases: EEXIT and everything else. EEXIT is a glorified indirect jump, e.g. %RBX holds the target %RIP. Everything else is an Asynchronous Enclave Exit (AEX). On an AEX, %RIP is set to a value specified by EENTER/ERESUME, %RBP and %RSP are restored to pre-enclave values and all other registers are loaded with synthetic state. The actual interrupt/exception/VMExit then triggers, e.g. the %RIP on the stack for an exception is always the AEX target, not the %RIP inside the enclave that actually faulted.
next prev parent reply other threads:[~2018-11-02 17:33 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 [this message] 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 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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