linux-kernel - Re: [PATCH RESEND 0/3] x86/sgx: eextend ioctl

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Date:   Fri, 2 Apr 2021 10:38:19 +0200
From:   Jethro Beekman <jethro@...tanix.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        Raoul Strackx <raoul.strackx@...tanix.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 0/3] x86/sgx: eextend ioctl

On 2021-04-01 20:40, Dave Hansen wrote:
> On 4/1/21 10:49 AM, Raoul Strackx wrote:
>> On 4/1/21 6:11 PM, Dave Hansen wrote:
>>> On 4/1/21 7:56 AM, Raoul Strackx wrote:
>>>> SOLUTION OF THIS PATCH
>>>> This patch adds a new ioctl to enable userspace to execute EEXTEND leaf 
>>>> functions per 256 bytes of enclave memory. This enables enclaves to be 
>>>> build as specified by enclave providers.
>>> I think tying the user ABI to the SGX architecture this closely is a
>>> mistake.
>>>
>>> Do we need another ioctl() or can we just relax the existing add_pages
>>> ioctl() to allow unaligned addresses?
>>>
>> I've considered this. In order to do an EEXTEND without an EADD, we'd
>> need to add a flag DONT_ADD_PAGES flag to `add_pages` ioctl as well. Two
>> separate ioctls, one for adding, another for extending made more sense
>> to me.
> 
> So, we're talking here about pages that have been EEADDED, but for which
> we do not want to include the entire contents of the page?  Do these
> contents always include the beginning of the page, or can the holes be
> anywhere?

Holes can be anywhere, and EEXTEND calls need not be sequential in memory address or even relate to the most recently EADDed page.

--
Jethro Beekman | Fortanix



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