From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jethro Beekman <jethro@fortanix.com>
Cc: 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>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
Josh Triplett <josh@joshtriplett.org>,
Haitao Huang <haitao.huang@linux.intel.com>,
"Dr . Greg Wettstein" <greg@enjellic.com>
Subject: Re: [RFC PATCH v4 5/5] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions
Date: Fri, 14 Dec 2018 07:38:30 -0800 [thread overview]
Message-ID: <20181214153830.GB22063@linux.intel.com> (raw)
In-Reply-To: <20181214151204.GA22063@linux.intel.com>
On Fri, Dec 14, 2018 at 07:12:04AM -0800, Sean Christopherson wrote:
> On Fri, Dec 14, 2018 at 09:55:49AM +0000, Jethro Beekman wrote:
> > On 2018-12-14 03:01, Sean Christopherson wrote:
> > >+2: pop %rbx
> > >+ pop %r12
> > >+ pop %r13
> > >+ pop %r14
> > >+ pop %r15
> > >+ pop %rbp
> > >+ ret
> >
> > x86-64 ABI requires that you call CLD here (enclave may set it).
>
> Ugh. Technically MXCSR and the x87 CW also need to be preserved.
>
> What if rather than treating the enclave as hostile we require it to be
> compliant with the x86-64 ABI like any other function? That would solve
> the EFLAGS.DF, MXCSR and x87 issues without adding unnecessary overhead.
> And we wouldn't have to save/restore R12-R15. It'd mean we couldn't use
> the stack's red zone to hold @regs and @e, but that's poor form anyways.
Grr, except the processor crushes R12-R15, FCW and MXCSR on asynchronous
exits. But not EFLAGS.DF, that's real helpful.
next prev parent reply other threads:[~2018-12-14 15:38 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-13 21:31 [RFC PATCH v4 0/5] x86: Add vDSO exception fixup for SGX Sean Christopherson
2018-12-13 21:31 ` [RFC PATCH v4 1/5] x86/vdso: Add support for exception fixup in vDSO functions Sean Christopherson
2018-12-13 21:31 ` [RFC PATCH v4 2/5] x86/fault: Add helper function to sanitize error code Sean Christopherson
2018-12-13 21:31 ` [RFC PATCH v4 3/5] x86/fault: Attempt to fixup unhandled #PF on ENCLU before signaling Sean Christopherson
2018-12-13 21:31 ` [RFC PATCH v4 4/5] x86/traps: Attempt to fixup exceptions in vDSO " Sean Christopherson
2018-12-13 21:31 ` [RFC PATCH v4 5/5] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions Sean Christopherson
2018-12-14 9:55 ` Jethro Beekman
2018-12-14 15:12 ` Sean Christopherson
2018-12-14 15:38 ` Sean Christopherson [this message]
2018-12-14 17:03 ` Sean Christopherson
2018-12-14 18:20 ` Josh Triplett
2018-12-14 18:37 ` Sean Christopherson
2018-12-14 18:44 ` Andy Lutomirski
2018-12-14 19:20 ` Sean Christopherson
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