From: Dave Hansen <dave.hansen@intel.com> To: Andy Lutomirski <luto@kernel.org> Cc: "Christopherson, Sean J" <sean.j.christopherson@intel.com>, 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: Tue, 6 Nov 2018 11:22:05 -0800 [thread overview] Message-ID: <b9c53669-cd27-e3bc-3d62-f47c77029c43@intel.com> (raw) In-Reply-To: <CALCETrWBV=1JbAKYn2Jy2LxkGZQvKRtFRnrWUMoejrwQe73VHw@mail.gmail.com> On 11/6/18 11:02 AM, Andy Lutomirski wrote: > On Tue, Nov 6, 2018 at 10:41 AM Dave Hansen <dave.hansen@intel.com> wrote: >> >> On 11/6/18 10:20 AM, Andy Lutomirski wrote: >>> I almost feel like the right solution is to call into SGX on its own >>> private stack or maybe even its own private address space. >> >> Yeah, I had the same gut feeling. Couldn't the debugger even treat the >> enclave like its own "thread" with its own stack and its own set of >> registers and context? That seems like a much more workable model than >> trying to weave it together with the EENTER context. > > So maybe the API should be, roughly > > sgx_exit_reason_t sgx_enter_enclave(pointer_to_enclave, struct > host_state *state); > sgx_exit_reason_t sgx_resume_enclave(same args); > > where host_state is something like: > > struct host_state { > unsigned long bp, sp, ax, bx, cx, dx, si, di; > }; > > and the values in host_state explicitly have nothing to do with the > actual host registers. So, if you want to use the outcall mechanism, > you'd allocate some memory, point sp to that memory, call > sgx_enter_enclave(), and then read that memory to do the outcall. Ah, so instead of the enclave rudely "hijacking" the EENTER context, we have it nicely return and nicely _hint_ to the calling context what it would like to do. Then, the EENTER context can make a controlled transition over to the requested context. > Actually implementing this would be distinctly nontrivial, and would > almost certainly need some degree of kernel help to avoid an explosion > when a signal gets delivered while we have host_state.sp loaded into > the actual SP register. Maybe rseq could help with this? As long as the memory pointed to by host_state.sp is valid and can hold the signal frame (grows down without clobbering anything), what goes boom? The signal handling would push a signal frame and call the handler. It would have a shallow-looking stack, but the handler could just do its normal business and return from the signal where the frame would get popped and continue with %rsp=host_state.sp, blissfully unaware of the signal ever having happened.
WARNING: multiple messages have this Message-ID (diff)
From: Dave Hansen <dave.hansen@intel.com> To: Andy Lutomirski <luto@kernel.org> Cc: "Christopherson, Sean J" <sean.j.christopherson@intel.com>, 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: Tue, 6 Nov 2018 11:22:05 -0800 [thread overview] Message-ID: <b9c53669-cd27-e3bc-3d62-f47c77029c43@intel.com> (raw) Message-ID: <20181106192205.R6tdR-MZBuTv2Y6cuairv1ZsHe6QZUgCWjrJfnq0X2c@z> (raw) In-Reply-To: <CALCETrWBV=1JbAKYn2Jy2LxkGZQvKRtFRnrWUMoejrwQe73VHw@mail.gmail.com> On 11/6/18 11:02 AM, Andy Lutomirski wrote: > On Tue, Nov 6, 2018 at 10:41 AM Dave Hansen <dave.hansen@intel.com> wrote: >> >> On 11/6/18 10:20 AM, Andy Lutomirski wrote: >>> I almost feel like the right solution is to call into SGX on its own >>> private stack or maybe even its own private address space. >> >> Yeah, I had the same gut feeling. Couldn't the debugger even treat the >> enclave like its own "thread" with its own stack and its own set of >> registers and context? That seems like a much more workable model than >> trying to weave it together with the EENTER context. > > So maybe the API should be, roughly > > sgx_exit_reason_t sgx_enter_enclave(pointer_to_enclave, struct > host_state *state); > sgx_exit_reason_t sgx_resume_enclave(same args); > > where host_state is something like: > > struct host_state { > unsigned long bp, sp, ax, bx, cx, dx, si, di; > }; > > and the values in host_state explicitly have nothing to do with the > actual host registers. So, if you want to use the outcall mechanism, > you'd allocate some memory, point sp to that memory, call > sgx_enter_enclave(), and then read that memory to do the outcall. Ah, so instead of the enclave rudely "hijacking" the EENTER context, we have it nicely return and nicely _hint_ to the calling context what it would like to do. Then, the EENTER context can make a controlled transition over to the requested context. > Actually implementing this would be distinctly nontrivial, and would > almost certainly need some degree of kernel help to avoid an explosion > when a signal gets delivered while we have host_state.sp loaded into > the actual SP register. Maybe rseq could help with this? As long as the memory pointed to by host_state.sp is valid and can hold the signal frame (grows down without clobbering anything), what goes boom? The signal handling would push a signal frame and call the handler. It would have a shallow-looking stack, but the handler could just do its normal business and return from the signal where the frame would get popped and continue with %rsp=host_state.sp, blissfully unaware of the signal ever having happened.
next prev parent reply other threads:[~2018-11-06 19:22 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 [this message] 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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