linux-kernel - Re: [RFC PATCH v3 0/4] x86: Add exception fixup for SGX ENCLU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20181211150152.GA14731@linux.intel.com>
Date:   Tue, 11 Dec 2018 07:01:52 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     "Dr. Greg" <greg@...ellic.com>
Cc:     Josh Triplett <josh@...htriplett.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        linux-sgx@...r.kernel.org, Andy Lutomirski <luto@...capital.net>,
        Haitao Huang <haitao.huang@...ux.intel.com>,
        Jethro Beekman <jethro@...tanix.com>
Subject: Re: [RFC PATCH v3 0/4] x86: Add exception fixup for SGX ENCLU

On Tue, Dec 11, 2018 at 08:53:39AM -0600, Dr. Greg wrote:
> On Mon, Dec 10, 2018 at 03:24:50PM -0800, Josh Triplett wrote:
> 
> Good morning to everyone, I hope the week is progressing well.
> 
> > On Mon, Dec 10, 2018 at 03:21:37PM -0800, Sean Christopherson wrote:
> > > At that point I realized it's a hell of a lot easier to simply provide
> > > an IOCTL via /dev/sgx that allows userspace to register a per-process
> > > ENCLU exception handler.  At a high level, the basic idea is the same
> > > as the vDSO approach: provide a hardcoded fixup handler for ENCLU and
> > > attempt to fixup select unhandled exceptions that occurred in user code.
> 
> > So, on the one hand, this is *absolutely* much cleaner than the VDSO
> > approach. On the other hand, this is global process state and has
> > some of the same problems as a signal handler as a result.
> 
> Sean's architecture is very simple and straight forward and thus has a
> lot going for it.
> 
> As Sean's approach indicates, by linking the exception handler to
> current->mm, SGX is very much a per memory map concept.  The issue is
> that there can be multiple enclaves loaded and excecuting in a
> processes memory map, the problem is, execution and thus exception
> handling, is very much at the per thread level.

Right, but is there a need to have a per-thread code page?  The handler
isn't per-process any more than the AEP is per-process.