linux-kernel - Re: [PATCH v29 00/20] Intel SGX foundations

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Date:   Wed, 6 May 2020 09:39:55 -0700
From:   Jordan Hand <jorhand@...ux.microsoft.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org
Cc:     akpm@...ux-foundation.org, dave.hansen@...el.com,
        sean.j.christopherson@...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
Subject: Re: [PATCH v29 00/20] Intel SGX foundations

On 4/21/20 2:52 PM, Jarkko Sakkinen wrote:
> Intel(R) SGX is a set of CPU instructions that can be used by applications
> to set aside private regions of code and data. The code outside the enclave
> is disallowed to access the memory inside the enclave by the CPU access
> control.
> 
> There is a new hardware unit in the processor called Memory Encryption
> Engine (MEE) starting from the Skylake microacrhitecture. BIOS can define
> one or many MEE regions that can hold enclave data by configuring them with
> PRMRR registers.
> 
> The MEE automatically encrypts the data leaving the processor package to
> the MEE regions. The data is encrypted using a random key whose life-time
> is exactly one power cycle.
> 
> The current implementation requires that the firmware sets
> IA32_SGXLEPUBKEYHASH* MSRs as writable so that ultimately the kernel can
> decide what enclaves it wants run. The implementation does not create
> any bottlenecks to support read-only MSRs later on.
> 
> You can tell if your CPU supports SGX by looking into /proc/cpuinfo:
> 
> 	cat /proc/cpuinfo  | grep sgx
> 
> v29:
> * The selftest has been moved to selftests/sgx. Because SGX is an execution
>    environment of its own, it really isn't a great fit with more "standard"
>    x86 tests.
> 
>    The RSA key is now generated on fly and the whole signing process has
>    been made as part of the enclave loader instead of signing the enclave
>    during the compilation time.
> 
>    Finally, the enclave loader loads now the test enclave directly from its
>    ELF file, which means that ELF file does not need to be coverted as raw
>    binary during the build process.
> * Version the mm_list instead of using on synchronize_mm() when adding new
>    entries. We hold the write lock for the mm_struct, and dup_mm() can thus
>    deadlock with the page reclaimer, which could hold the lock for the old
>    mm_struct.
> * Disallow mmap(PROT_NONE) from /dev/sgx. Any mapping (e.g. anonymous) can
>    be used to reserve the address range. Now /dev/sgx supports only opaque
>    mappings to the (initialized) enclave data.
> * Make the vDSO callable directly from C by preserving RBX and taking leaf
>    from RCX.
> 

Tested with the Open Enclave SDK on top of Intel PSW. Specifically built 
the Intel PSW with changes to support /dev/sgx mapping[1] new in v29.

Tested-by: Jordan Hand <jorhand@...ux.microsoft.com>

[1] https://github.com/intel/linux-sgx/pull/530