linux-kernel - Re: [PATCH v26 10/22] x86/sgx: Linux Enclave Driver

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Message-ID: <20200214171146.GD20690@linux.intel.com>
Date:   Fri, 14 Feb 2020 09:11:46 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Jethro Beekman <jethro@...tanix.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org, akpm@...ux-foundation.org,
        dave.hansen@...el.com, nhorman@...hat.com, npmccallum@...hat.com,
        haitao.huang@...el.com, andriy.shevchenko@...ux.intel.com,
        tglx@...utronix.de, kai.svahn@...el.com, bp@...en8.de,
        josh@...htriplett.org, luto@...nel.org, kai.huang@...el.com,
        rientjes@...gle.com, cedric.xing@...el.com, puiterwijk@...hat.com,
        linux-security-module@...r.kernel.org,
        Haitao Huang <haitao.huang@...ux.intel.com>
Subject: Re: [PATCH v26 10/22] x86/sgx: Linux Enclave Driver

On Fri, Feb 14, 2020 at 10:24:10AM +0100, Jethro Beekman wrote:
> On 2020-02-13 19:07, Sean Christopherson wrote:
> > On Thu, Feb 13, 2020 at 02:59:52PM +0100, Jethro Beekman wrote:
> >> On 2020-02-09 22:25, Jarkko Sakkinen wrote:
> >>> +/**
> >>> + * struct sgx_enclave_add_pages - parameter structure for the
> >>> + *                                %SGX_IOC_ENCLAVE_ADD_PAGE ioctl
> >>> + * @src:	start address for the page data
> >>> + * @offset:	starting page offset
> >>> + * @length:	length of the data (multiple of the page size)
> >>> + * @secinfo:	address for the SECINFO data
> >>> + * @flags:	page control flags
> >>> + * @count:	number of bytes added (multiple of the page size)
> >>> + */
> >>> +struct sgx_enclave_add_pages {
> >>> +	__u64	src;
> >>> +	__u64	offset;
> >>> +	__u64	length;
> >>> +	__u64	secinfo;
> >>> +	__u64	flags;
> >>> +	__u64	count;
> >>> +};
> >>
> >> Compared to the last time I looked at the patch set, this API removes the
> >> ability to measure individual pages chunks. That is not acceptable.
> > 
> > Why is it not acceptable?  E.g. what specific use case do you have that
> > _requires_ on measuring partial 4k pages of an enclave?
> 
> The use case is someone gives me an enclave and I want to load it. If I don't
> load it exactly as the enclave author specified, the enclave hash will be
> different, and it won't work.

And if our ABI says "thou shall measure in 4k chunks", then it's an invalid
enclave if its author generated MRENCLAVE using a different granularity.