linux-kernel - Re: [PATCH v36 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call

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: <CALCETrVch_XW-oc_-LR8Dbgat9DpSKtCYTV9YZaU7tfu61FHEw@mail.gmail.com>
Date:   Mon, 10 Aug 2020 16:08:46 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Nathaniel McCallum <npmccallum@...hat.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        X86 ML <x86@...nel.org>, linux-sgx@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Jethro Beekman <jethro@...tanix.com>,
        Cedric Xing <cedric.xing@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        asapek@...gle.com, Borislav Petkov <bp@...en8.de>,
        chenalexchen@...gle.com, Conrad Parker <conradparker@...gle.com>,
        cyhanish@...gle.com, Dave Hansen <dave.hansen@...el.com>,
        "Huang, Haitao" <haitao.huang@...el.com>,
        Josh Triplett <josh@...htriplett.org>,
        "Huang, Kai" <kai.huang@...el.com>,
        "Svahn, Kai" <kai.svahn@...el.com>, Keith Moyer <kmoy@...gle.com>,
        Christian Ludloff <ludloff@...gle.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Neil Horman <nhorman@...hat.com>,
        Patrick Uiterwijk <puiterwijk@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>, yaozhangx@...gle.com
Subject: Re: [PATCH v36 21/24] x86/vdso: Implement a vDSO for Intel SGX
 enclave call

On Thu, Aug 6, 2020 at 7:55 AM Nathaniel McCallum <npmccallum@...hat.com> wrote:
>
> In a past revision of this patch, I had requested a void *misc
> parameter that could be passed through vdso_sgx_enter_enclave_t into
> sgx_enclave_exit_handler_t. This request encountered some push back
> and I dropped the issue. However, I'd like to revisit it or something
> similar.

Why do you need an exit handler at all?  IIRC way back when I
suggested that we simply not support it at all.  If you want to
call__vdso_sgx_enter_enclave() in a loop, call it in a loop.  If you
want to wrap it intelligently in Rust, you don't want a callback
anyway -- that forces you have an FFI (or non-Rust, anyway) frame on
the stack, which interacts poorly with panic handling and prevents you
from using await in your Rust callback handler.  If, on the other
hand, you just call __vdso_sg_enter_enclave() in a loop, all these
problems go away and, if you really want, you can pass in a callback
in Rust and call the callback from Rust.

What am I missing?  I still don't really understand why we are
supporting this mechanism at all.  Just the asm code to invoke the
callback seems to be about half of the entire function.