From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jethro Beekman <jethro@fortanix.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"x86@kernel.org" <x86@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
"H. Peter Anvin" <hpa@zytor.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
Josh Triplett <josh@joshtriplett.org>,
Haitao Huang <haitao.huang@linux.intel.com>,
"linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
"Dr. Greg" <greg@enjellic.com>
Subject: Re: [RFC PATCH v2 4/4] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions
Date: Fri, 14 Dec 2018 07:04:37 -0800 [thread overview]
Message-ID: <20181214150436.GA23255@linux.intel.com> (raw)
In-Reply-To: <f595c046-682c-0d4a-ce68-44d4634cedf2@fortanix.com>
On Sat, Dec 08, 2018 at 08:15:38AM +0000, Jethro Beekman wrote:
> On 2018-12-08 00:14, Dave Hansen wrote:
> >On 12/7/18 10:15 AM, Jethro Beekman wrote:
> >>This is not sufficient to support the Fortanix SGX ABI calling
> >>convention, which was designed to be mostly compatible with the SysV
> >>64-bit calling convention. The following registers need to be passed in
> >>to an enclave from userspace: RDI, RSI, RDX, R8, R9, R10. The following
> >>registers need to be passed out from an enclave to userspace: RDI, RSI,
> >>RDX, R8, R9.
> >
> >Are you asking nicely to change the new Linux ABI to be consistent with
> >your existing ABI? Or, are you saying that the new ABI *must* be
> >compatible with this previous out-of-tree implementation?
>
> What's being discussed here is one of the alternatives for SGX fault
> handling, meant to improve the current status quo of having to use a signal
> handler.
>
> I'm merely providing a data point that the currently proposed solution is
> not sufficient to support current use of the (ring 3) ENCLU instruction. You
> might find this useful in determining whether proposed kernel features will
> actually be used by users, and in further developing this solution or other
> solutions to the fault handling issue.
>
> If going with the vDSO solution, I think something with semantics closer to
> the actual instruction would be preferred, like the following:
>
> notrace __attribute__((naked)) long __vdso_sgx_enclu_with_aep()
> {
> asm volatile(
> " lea 2f(%%rip), %%rcx\n"
> "1: enclu\n"
> "2: ret\n"
> ".pushsection .fixup, \"ax\" \n"
> "3: jmp 2b\n"
> ".popsection\n"
> _ASM_VDSO_EXTABLE_HANDLE(1b, 3b)
> :::
> );
> }
Part of me likes this idea, but it's a documentation nightmare since
it's a completely customer register ABI. And the caller's exception
handling gets a bit weird since RAX implicitly defines whether or not
an exception occurred. I also think there's value in making the vDSO
function callable from standard C.
next prev parent reply other threads:[~2018-12-14 15:04 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20181206221922.31012-1-sean.j.christopherson@intel.com>
[not found] ` <20181206221922.31012-5-sean.j.christopherson@intel.com>
[not found] ` <CALCETrXRJ645=08fyeoMQ949fLB1TvhsgERFVx5mAHdViEjq8Q@mail.gmail.com>
2018-12-07 16:51 ` [RFC PATCH v2 4/4] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions Sean Christopherson
2018-12-07 17:56 ` Andy Lutomirski
2018-12-07 19:02 ` Sean Christopherson
2018-12-07 19:23 ` Andy Lutomirski
2018-12-07 20:09 ` Sean Christopherson
2018-12-07 20:16 ` Andy Lutomirski
2018-12-07 20:35 ` Sean Christopherson
2018-12-07 21:26 ` Sean Christopherson
2018-12-07 23:33 ` Andy Lutomirski
2018-12-11 19:31 ` Sean Christopherson
2018-12-11 20:04 ` Andy Lutomirski
2018-12-11 22:00 ` Sean Christopherson
2018-12-11 23:12 ` Andy Lutomirski
2018-12-07 18:15 ` Jethro Beekman
2018-12-07 18:44 ` Dave Hansen
2018-12-07 18:50 ` Andy Lutomirski
2018-12-08 8:15 ` Jethro Beekman
2018-12-14 15:04 ` Sean Christopherson [this message]
[not found] ` <20181207163127.GA23494@wind.enjellic.com>
2018-12-07 18:19 ` Jethro Beekman
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