Signed-off-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
Tested-by: Serge Ayoun <serge.ay...@intel.com>
---
Documentation/index.rst | 1 +
Documentation/x86/intel_sgx.rst | 101 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 102 insertions(+)
create mode 100644 Documentation/x86/intel_sgx.rst
diff --git a/Documentation/index.rst b/Documentation/index.rst
index cb7f1ba5b3b1..ccfebc260e04 100644
--- a/Documentation/index.rst
+++ b/Documentation/index.rst
@@ -86,6 +86,7 @@ implementation.
:maxdepth: 2
sh/index
+ x86/index
Korean translations
-------------------
diff --git a/Documentation/x86/intel_sgx.rst b/Documentation/x86/intel_sgx.rst
new file mode 100644
index 000000000000..59049a35512f
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+++ b/Documentation/x86/intel_sgx.rst
@@ -0,0 +1,101 @@
+===================
+Intel(R) SGX driver
+===================
+
+Introduction
+============
+
+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.
+In a way you can think that SGX provides inverted sandbox. It protects the
+application from a malicious host.
+
+There is a new hardware unit in the processor called Memory Encryption Engine
+(MEE) starting from the Skylake microarchitecture. 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.
+
+You can tell if your CPU supports SGX by looking into ``/proc/cpuinfo``:
+
+ ``cat /proc/cpuinfo | grep sgx``
+
+Enclave data types
+==================
+
+SGX defines new data types to maintain information about the enclaves and their
+security properties.
+
+The following data structures exist in MEE regions:
+
+* **Enclave Page Cache (EPC):** memory pages for protected code and data
+* **Enclave Page Cache Map (EPCM):** meta-data for each EPC page
+
+The Enclave Page Cache holds following types of pages:
+
+* **SGX Enclave Control Structure (SECS)**: meta-data defining the global
+ properties of an enclave such as range of addresses it can access.
+* **Regular (REG):** containing code and data for the enclave.
+* **Thread Control Structure (TCS):** defines an entry point for a hardware
+ thread to enter into the enclave. The enclave can only be entered through
+ these entry points.
+* **Version Array (VA)**: an EPC page receives a unique 8 byte version number
+ when it is swapped, which is then stored into a VA page. A VA page can hold
up
+ to 512 version numbers.
+
+Launch control
+==============
+
+For launching an enclave, two structures must be provided for ENCLS(EINIT):
+
+1. **SIGSTRUCT:** a signed measurement of the enclave binary.
+2. **EINITTOKEN:** the measurement, the public key of the signer and various
+ enclave attributes. This structure contains a MAC of its contents using
+ hardware derived symmetric key called *launch key*.
+
+The hardware platform contains a root key pair for signing the SIGTRUCT
+for a *launch enclave* that is able to acquire the *launch key* for
+creating EINITTOKEN's for other enclaves. For the launch enclave
+EINITTOKEN is not needed because it is signed with the private root key.
+
+There are two feature control bits associate with launch control:
+
+* **IA32_FEATURE_CONTROL[0]**: locks down the feature control register
+* **IA32_FEATURE_CONTROL[17]**: allow runtime reconfiguration of
+ IA32_SGXLEPUBKEYHASHn MSRs that define MRSIGNER hash for the launch
+ enclave. Essentially they define a signing key that does not require
+ EINITTOKEN to be let run.
+
+The BIOS can configure IA32_SGXLEPUBKEYHASHn MSRs before feature control
+register is locked.
+
+It could be tempting to implement launch control by writing the MSRs
+every time when an enclave is launched. This does not scale because for
+generic case because BIOS might lock down the MSRs before handover to
+the OS.
+
+Debug enclaves
+--------------
+
+Enclave can be set as a *debug enclave* of which memory can be read or written
+by using the ENCLS(EDBGRD) and ENCLS(EDBGWR) opcodes. The Intel provided launch
+enclave provides them always a valid EINITTOKEN and therefore they are a low
+hanging fruit way to try out SGX.
+
+SGX uapi
+========
+
+.. kernel-doc:: drivers/platform/x86/intel_sgx_ioctl.c
+ :functions: sgx_ioc_enclave_create
+ sgx_ioc_enclave_add_page
+ sgx_ioc_enclave_init
+
+.. kernel-doc:: arch/x86/include/uapi/asm/sgx.h
+
+References
+==========
+
+* System Programming Manual: 39.1.4 Intel?? SGX Launch Control Configuration
--
2.14.1
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