linux-kernel - Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call

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Date:   Fri, 25 Sep 2020 10:14:41 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>, x86@...nel.org,
        linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Jethro Beekman <jethro@...tanix.com>,
        Cedric Xing <cedric.xing@...el.com>, akpm@...ux-foundation.org,
        andriy.shevchenko@...ux.intel.com, asapek@...gle.com,
        chenalexchen@...gle.com, conradparker@...gle.com,
        cyhanish@...gle.com, dave.hansen@...el.com, haitao.huang@...el.com,
        josh@...htriplett.org, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, luto@...nel.org,
        nhorman@...hat.com, npmccallum@...hat.com, puiterwijk@...hat.com,
        rientjes@...gle.com, tglx@...utronix.de, yaozhangx@...gle.com
Subject: Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX
 enclave call

On Thu, Sep 24, 2020 at 05:38:10PM -0700, Sean Christopherson wrote:
> > Why not simply
> > 
> > arch/x86/entry/vdso/sgx.S
> > 
> > ?
> 
> I really like typing?

I'll say.

> Yes, to call out that there's a field there, but a field that the vDSO should
> never touch.

You wanna enforce that in the vdso code?

Because if it is there, luserspace will touch it.

> > > +#define SGX_ENCLAVE_RUN_EXCEPTION	4*8
> > > +
> > > +#define SGX_SYNCHRONOUS_EXIT		0
> > > +#define SGX_EXCEPTION_EXIT		1
> > 
> > Those are in ...uapi/asm/sgx.h too. Unify?
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

What about this here?

> > Are the CFI annotations for userspace?
> 
> Yes, though that's a 90% confident "yes".

Looks like we wanna support it:

f24f91088427 ("x86/vdso: Define BUILD_VDSO while building and emit .eh_frame in asm")

> Argh, it's actually supposed to be TCS, SGX_ENCLAVE_RUN_TSC is the one that's
> wrong.

Whoopsie :-)

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette