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Wed, 19 Aug 2015 01:41:06 -0700 (PDT) Received: from localhost.localdomain ([85.235.11.236]) by smtp.gmail.com with ESMTPSA id g5sm5680487laf.33.2015.08.19.01.41.04 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 19 Aug 2015 01:41:05 -0700 (PDT) From: Jens Wiklander To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, Arnd Bergmann , Greg Kroah-Hartman , Kees Cook Subject: [PATCH v5 5/5] Documentation: tee subsystem and op-tee driver Date: Wed, 19 Aug 2015 10:40:29 +0200 Message-Id: <1439973629-19505-6-git-send-email-jens.wiklander@linaro.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1439973629-19505-1-git-send-email-jens.wiklander@linaro.org> References: <1439973629-19505-1-git-send-email-jens.wiklander@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150819_014126_961645_44E44048 X-CRM114-Status: GOOD ( 22.63 ) X-Spam-Score: -2.6 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: valentin.manea@huawei.com, Mark Rutland , javier@javigon.com, emmanuel.michel@st.com, Michal Simek , jean-michel.delorme@st.com, Jason Gunthorpe , Rob Herring , Jens Wiklander MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.8 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Signed-off-by: Jens Wiklander --- Documentation/00-INDEX | 2 + Documentation/tee.txt | 117 +++++++++++++++++++++++++++++++++++++++++++++++++ MAINTAINERS | 1 + 3 files changed, 120 insertions(+) create mode 100644 Documentation/tee.txt diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX index cd077ca..bd3f803 100644 --- a/Documentation/00-INDEX +++ b/Documentation/00-INDEX @@ -435,6 +435,8 @@ sysrq.txt - info on the magic SysRq key. target/ - directory with info on generating TCM v4 fabric .ko modules +tee.txt + - info on the TEE subsystem and drivers this_cpu_ops.txt - List rationale behind and the way to use this_cpu operations. thermal/ diff --git a/Documentation/tee.txt b/Documentation/tee.txt new file mode 100644 index 0000000..4ac91d2 --- /dev/null +++ b/Documentation/tee.txt @@ -0,0 +1,117 @@ +TEE subsystem +This document describes the TEE subsystem in Linux + +A TEE (Trusted Execution Environment) is a trusted OS running in some +secure environment, for example, TrustZone on ARM CPUs, or a separate +secure co-processor etc. A TEE driver handles the details needed to +communicate with the TEE. + +This subsystem deals with: + +- Registration of TEE drivers + +- Managing shared memory between Linux and the TEE + +- Providing a generic API to the TEE + +The TEE interface +================= + +include/uapi/linux/tee.h defines the generic interface to a TEE. + +User space (the client) connects to the driver by opening /dev/tee[0-9]* or +/dev/teepriv[0-9]*. + +- TEE_IOC_SHM_ALLOC allocates shared memory and returns a file descriptor which + user space can mmap. When user space doesn't need the file descriptor anymore + it should be closed. When shared memory isn't needed any longer it should be + unmapped with munmap() to allow the reuse of memory. + +- TEE_IOC_VERSION lets user space know which TEE this driver handles and + the its capabilities. + +- TEE_IOC_OPEN_SESSION opens a new session to a Trusted Application + +- TEE_IOC_INVOKE invokes a function in a Trusted Application + +- TEE_IOC_CANCEL may cancel an ongoing TEE_IOC_OPEN_SESSION or TEE_IOC_INVOKE + +- TEE_IOC_CLOSE_SESSION closes a session to a Trusted Application + +There are two classes of clients, normal clients and supplicants. The latter is +a helper process for the TEE to access resources in Linux, for example file +system access. A normal client opens /dev/tee[0-9]* and a supplicant opens +/dev/teepriv[0-9]. + +Much of the communication between clients and the TEE is opaque to the +driver. The main job for the driver is to receive requests from the +clients, forward them to the TEE and send back the results. In the case of +supplicants the communication goes in the other direction, the TEE sends +requests to the supplicant which then sends back the result. + +OP-TEE driver +============= + +The OP-TEE driver handles OP-TEE [1] based TEEs. Currently it is only the ARM +TrustZone based OP-TEE solution that is supported. + +Lowest level of communication with OP-TEE builds on ARM SMC Calling +Convention (SMCCC) [2], which is the foundation for OP-TEE's SMC interface +[3] used internally by the driver. Stacked on top of that is OP-TEE Message +Protocol [4]. + +OP-TEE SMC interface provides the basic functions required by SMCCC and some +additional functions specific for OP-TEE. The most interesting functions are: + +- OPTEE_SMC_FUNCID_CALLS_UID (part of SMCCC) returns the version information + which is then returned by TEE_IOC_VERSION + +- OPTEE_SMC_CALL_GET_OS_UUID returns the particular OP-TEE implementation, used + to tell, for instance, a TrustZone OP-TEE apart from an OP-TEE running on a + separate secure co-processor. + +- OPTEE_SMC_CALL_WITH_ARG drives the OP-TEE message protocol + +- OPTEE_SMC_GET_SHM_CONFIG lets the driver and OP-TEE agree on which memory + range to used for shared memory between Linux and OP-TEE. + +The GlobalPlatform TEE Client API [5] is implemented on top of the generic +TEE API. + +Picture of the relationship between the different components in the +OP-TEE architecture. + + User space Kernel Secure world + ~~~~~~~~~~ ~~~~~~ ~~~~~~~~~~~~ + +--------+ +-------------+ + | Client | | Trusted | + +--------+ | Application | + /\ +-------------+ + || +----------+ /\ + || |tee- | || + || |supplicant| \/ + || +----------+ +-------------+ + \/ /\ | TEE Internal| + +-------+ || | API | + + TEE | || +--------+--------+ +-------------+ + | Client| || | TEE | OP-TEE | | OP-TEE | + | API | \/ | subsys | driver | | Trusted OS | + +-------+----------------+----+-------+----+-----------+-------------+ + | Generic TEE API | | OP-TEE MSG | + | IOCTL (TEE_IOC_*) | | SMCCC (OPTEE_SMC_CALL_*) | + +-----------------------------+ +------------------------------+ + +RPC (Remote Procedure Call) are requests from secure world to kernel driver +or tee-supplicant. An RPC is identified by a special range of SMCCC return +values from OPTEE_SMC_CALL_WITH_ARG. RPC messages which are intended for the +kernel are handled by the kernel driver. Other RPC messages will be forwarded to +tee-supplicant without further involvement of the driver, except switching +shared memory buffer representation. + +References: +[1] https://github.com/OP-TEE/optee_os +[2] http://infocenter.arm.com/help/topic/com.arm.doc.den0028a/index.html +[3] drivers/tee/optee/optee_smc.h +[4] drivers/tee/optee/optee_msg.h +[5] http://www.globalplatform.org/specificationsdevice.asp look for + "TEE Client API Specification v1.0" and click download. diff --git a/MAINTAINERS b/MAINTAINERS index 2df3f03..a48d718 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -8646,6 +8646,7 @@ S: Maintained F: include/linux/tee_drv.h F: include/uapi/linux/tee.h F: drivers/tee/ +F: Documentation/tee.txt THUNDERBOLT DRIVER M: Andreas Noever