linux-kernel - Re: [PATCH v33 15/21] x86/vdso: Add support for exception fixup in vDSO functions

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Message-ID: <20200630084128.GA1093@zn.tnic>
Date:   Tue, 30 Jun 2020 10:41:28 +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>,
        akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
        asapek@...gle.com, cedric.xing@...el.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 v33 15/21] x86/vdso: Add support for exception fixup in
 vDSO functions

On Mon, Jun 29, 2020 at 11:00:55PM -0700, Sean Christopherson wrote:
> E.g. the vDSO function should get the fixup even if userspace screws
> up mmap() and invokes __vdso_sgx_enter_enclave() without being tagged
> an SGX task.

I sincerely hope you don't mean this seriously.

Please add a member to task_struct which denotes that a task is an
sgx task, test that member where needed and forget real quickly about
running *any* *fixup* for unrelated tasks.

> No hard dependency, it's normal kernel code.  My reasoning for dropping it
> in .../vdso was largely to co-locate it with vdso/extable.h due to the
> dependency on the format of 'struct vdso_exception_table_entry'.

A struct which you defined instead of simply using struct
exception_table_entry even if it has a handler member which would remain
unused?

Let's not put code in vdso/ if it doesn't really belong there pls.

> Ya, shouldn't be a problem to stub it out for SGX=n.

Thx.

-- 
Regards/Gruss,
    Boris.

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