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Date:   Mon, 26 Nov 2018 14:06:27 -0800
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     Jethro Beekman <jethro@fortanix.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Florian Weimer <fweimer@redhat.com>,
        Linux API <linux-api@vger.kernel.org>,
        Jann Horn <jannh@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        X86 ML <x86@kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Rich Felker <dalias@libc.org>,
        "nhorman@redhat.com" <nhorman@redhat.com>,
        "npmccallum@redhat.com" <npmccallum@redhat.com>,
        "Ayoun, Serge" <serge.ayoun@intel.com>,
        "shay.katz-zamir@intel.com" <shay.katz-zamir@intel.com>,
        "linux-sgx@vger.kernel.org" <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>
Subject: Re: RFC: userspace exception fixups
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On Mon, Nov 26, 2018 at 06:35:34AM -0800, Sean Christopherson wrote:
> And how would you determine the #UD is related to SGX?  Hardware doesn't
> provide any indication that a #UD (or any other fault) is related to SGX
> or occurred in an enclave.  The only fault that is special-cased in a
> non-virtualized environment is #PF signaled by the EPCM, which gets the
> PF_SGX bit set in the error code.

Could you not detect #UD from address where it happened? Kernel knows
where enclaves are mapped. BTW, how does Intel run-time emulate opcodes
currently?

Anyway, I've fully discarded the whole idea because implementing single
stepping w/o well defined AEP handler is nasty. I think vDSO's are the
only viable path that at least I'm aware off...

/Jarkko