Trusted side of the TEE

@Victor Chong Victor Chong authored on 11 Nov 2016
core core: fix ta_private_vmem support 7 years ago
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keys TA as ELF + signature 9 years ago
lib libutee extension: check-access-right for secure/nonsec permissions 7 years ago
mk mk/checkconf.mk: allow spaces and double quotes in CFG_ config variables 7 years ago
scripts scripts: add wrapper script for checkpatch 7 years ago
ta ta_dev_kit.mk: get optional flags from $(CFLAGS_$(sm))/$(CPPFLAGS_$(sm)) 7 years ago
.gitignore Open-source the TEE Core 10 years ago
.travis.yml .travis.yml: Add Coverity addon 7 years ago
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LICENSE Changing from old STM CLA to the new DCO 9 years ago
MAINTAINERS.md plat-stm: discard orly2 flavor 7 years ago
Makefile Fix invalid default value of $(PLATFORM_FLAVOR) 8 years ago
Notice.md Changing from old STM CLA to the new DCO 9 years ago
README.md doc: update README.md, add info about VirtFS 7 years ago
README.md

OP-TEE Trusted OS

Contents

  1. Introduction
  2. License
  3. Platforms supported
    1. [Development board for community user] (#31-development-board-for-community-user)
  4. Get and build OP-TEE software
    1. Prerequisites
    2. Basic setup
    3. STMicroelectronics boards
    4. Allwinner A80
    5. Freescale MX6UL EVK
  5. repo manifests
    1. Install repo
    2. Get the source code
      1. Targets
      2. Branches
      3. Get the toolchains
    3. QEMU
    4. FVP
    5. HiKey
    6. MT8173-EVB
    7. Juno
      1. Update flash and its layout
      2. GlobalPlatform testsuite support
      3. GCC5 support
    8. Raspberry Pi 3
    9. Tips and tricks
      1. Reference existing project to speed up repo sync
      2. Use ccache
  6. Load driver, tee-supplicant and run xtest
  7. Coding standards
    1. checkpatch

1. Introduction

The optee_os git, contains the source code for the TEE in Linux using the ARMĀ® TrustZoneĀ® technology. This component meets the GlobalPlatform TEE System Architecture specification. It also provides the TEE Internal core API v1.1 as defined by the GlobalPlatform TEE Standard for the development of Trusted Applications. For a general overview of OP-TEE and to find out how to contribute, please see the Notice.md file.

The Trusted OS is accessible from the Rich OS (Linux) using the GlobalPlatform TEE Client API Specification v1.0, which also is used to trigger secure execution of applications within the TEE.


2. License

The software is distributed mostly under the BSD 2-Clause open source license, apart from some files in the optee_os/lib/libutils directory which are distributed under the BSD 3-Clause or public domain licenses.


3. Platforms supported

Several platforms are supported. In order to manage slight differences between platforms, a PLATFORM_FLAVOR flag has been introduced. The PLATFORM and PLATFORM_FLAVOR flags define the whole configuration for a chip the where the Trusted OS runs. Note that there is also a composite form which makes it possible to append PLATFORM_FLAVOR directly, by adding a dash in-between the names. The composite form is shown below for the different boards. For more specific details about build flags etc, please read the file build_system.md. Some platforms have different sub-maintainers, please refer to the file MAINTAINERS.md for contact details for various platforms.

Platform Composite PLATFORM flag Publicly available?
Allwinner A80 Board PLATFORM=sunxi No
ARM Juno Board PLATFORM=vexpress-juno Yes
FSL ls1021a PLATFORM=ls-ls1021atwr Yes
FSL i.MX6 Quad SABRE Lite Board PLATFORM=imx Yes
FSL i.MX6 Quad SABRE SD Board PLATFORM=imx Yes
FSL i.MX6 UltraLite EVK Board PLATFORM=imx Yes
ARM Foundation FVP PLATFORM=vexpress-fvp Yes
HiSilicon D02 PLATFORM=d02 No
HiKey Board (HiSilicon Kirin 620) PLATFORM=hikey Yes
MediaTek MT8173 EVB Board PLATFORM=mediatek-mt8173 No
QEMU PLATFORM=vexpress-qemu_virt Yes
QEMUv8 PLATFORM=vexpress-qemu_armv8a Yes
Raspberry Pi 3 PLATFORM=rpi3 Yes
Renesas RCAR PLATFORM=rcar No
STMicroelectronics b2260 - h410 (96boards fmt) PLATFORM=stm-b2260 No
STMicroelectronics b2120 - h310 / h410 PLATFORM=stm-cannes No
Texas Instruments DRA7xx PLATFORM=ti-dra7xx Yes
Xilinx Zynq UltraScale+ MPSOC PLATFORM=zynqmp-zcu102 Yes
Spreadtrum SC9860 PLATFORM=sprd-sc9860 No

3.1 Development board for community user

For community users, we suggest using HiKey board as development board. It provides detailed documentation including chip datasheet, board schematics, source code, binaries etc on the download link at the website.


4. Get and build OP-TEE software

There are a couple of different build options depending on the target you are going to use. If you just want to get the software and compile it, then you should follow the instructions under the "Basic setup" below. In case you are going to run for a certain hardware or FVP, QEMU for example, then please follow the respective section found below instead, having that said, we are moving from the shell script based setups to instead use repo, so for some targets you will see that we are using repo (section 5) and for others we are still using the shell script based setup (section 4), please see this transitions as work in progress.


4.1 Prerequisites

We believe that you can use any Linux distribution to build OP-TEE, but as maintainers of OP-TEE we are mainly using Ubuntu-based distributions and to be able to build and run OP-TEE there are a few packages that needs to be installed to start with. Therefore install the following packages regardless of what target you will use in the end.

$ sudo apt-get install android-tools-adb android-tools-fastboot autoconf bc \
    bison cscope curl flex gdisk libc6:i386 libfdt-dev libftdi-dev \
    libglib2.0-dev libhidapi-dev libncurses5-dev libpixman-1-dev \
    libstdc++6:i386 libtool libz1:i386 mtools netcat python-crypto \
    python-serial python-wand unzip uuid-dev xdg-utils xz-utils zlib1g-dev

4.2 Basic setup

4.2.1 Get the compiler

We strive to use the latest available compiler from Linaro. Start by downloading and unpacking the compiler. Then export the PATH to the compilers bin folder. Beware that we are using a couple of different toolchains depending on the target device. This includes both 64- and 32-bit toolchains. For the exact toolchain in use, please have a look at toolchain.mk and then look at the targets makefile (see build.git) to find out where the respective toolchain will be used. For example in the QEMU makefile you will see:

CROSS_COMPILE_NS_USER       ?= "$(CCACHE)$(AARCH32_CROSS_COMPILE)"
CROSS_COMPILE_NS_KERNEL     ?= "$(CCACHE)$(AARCH32_CROSS_COMPILE)"
CROSS_COMPILE_S_USER        ?= "$(CCACHE)$(AARCH32_CROSS_COMPILE)"
CROSS_COMPILE_S_KERNEL      ?= "$(CCACHE)$(AARCH32_CROSS_COMPILE)"

However, if you only want to compile optee_os, then you can do like this:

$ cd $HOME
$ mkdir toolchains
$ cd toolchains
$ wget http://releases.linaro.org/14.08/components/toolchain/binaries/gcc-linaro-arm-linux-gnueabihf-4.9-2014.08_linux.tar.xz
$ tar xvf gcc-linaro-arm-linux-gnueabihf-4.9-2014.08_linux.tar.xz
$ export PATH=$HOME/toolchains/gcc-linaro-arm-linux-gnueabihf-4.9-2014.08_linux/bin:$PATH

4.2.2 Download the source code

$ cd $HOME
$ mkdir devel
$ cd devel
$ git clone https://github.com/OP-TEE/optee_os.git

4.2.3 Build

$ cd $HOME/devel/optee_os
$ CROSS_COMPILE=arm-linux-gnueabihf- make

4.2.4 Compiler flags

To be able to see the full command when building you could build using following flag:

$ make V=1

To enable debug builds use the following flag:

$ make DEBUG=1

OP-TEE supports a couple of different levels of debug prints for both TEE core itself and for the Trusted Applications. The level ranges from 1 to 4, where four is the most verbose. To set the level you use the following flag:

$ make CFG_TEE_CORE_LOG_LEVEL=4

4.4 STMicroelectronics boards

Currently OP-TEE is supported Cannes family (b2120 both h310 and h410 chips) and the 96boards/cannes board (b2260-h410).

4.4.1 Get the compiler

Follow the instructions in the "4.2 Basic setup".

4.4.2 Download the source code

See section "4.2.2 Download the source code".

4.4.3 Build the images and files

For the 96boards/cannes:

$ make PLATFORM=stm-b2260

For the legacy cannes family:

$ make PLATFORM=stm-cannes

4.4.4 Prepare, install and run the software

For 96board/cannes: Copy the generated 'optee.bin' on target SD or USB stick and insure the boot media boot scripts defines optee and non-secure worlds boot.

More info to come...


4.5 Allwinner A80

4.5.1 Locked versus unlocked A80 boards

Important! All A80 boards sold to the general public are boards where secure side has been locked down, which means that you cannot use them for secure side development, i.e, it will not be possible to put OP-TEE on those devices. If you want to use A80 board for secure side development, then you will need to talk to Allwinner directly and ask if it is possible get a device from them.

4.5.2 Get the compiler and source

Follow the instructions in the "4.2 Basic setup".

4.5.3 Build

$ cd optee_os
$ export PLATFORM=sunxi
$ export CROSS_COMPILE=arm-linux-gnueabihf-
$ make

4.5.4 Prepare the images to run on A80 Board

Download Allwinner A80 platform SDK, the SDK refers to Allwinner A80 platform SDK root directory. A80 SDK directory tree looks like this:

SDK/
    Android
    lichee

Android contains all source code related to Android and lichee contains the bootloader and Linux kernel.

4.5.4.1 Copy OP-TEE output to package directory

Copy the OP-TEE output binary to SDK/lichee/tools/pack/sun9i/bin

$ cd optee_os
$ cp ./out/arm32-plat-sunxi/core/tee.bin SDK/lichee/tools/pack/sun9i/bin
4.5.4.2 Build Linux kernel

In the lichee directory, run the following commands:

$ cd SDK/lichee
$ ./build.sh
4.5.4.3 Build Android

In the Android directory, run the following commands:

$ cd SDK/android
$ extract-bsp
$ make -j
4.5.4.4 Create the Android image

In the Android directory, run the following commands:

$ cd SDK/android
$ pack

The output image will been signed internally when packed. The output image name is a80_android_board.img.

4.5.4.5 Download the Android image

Use Allwinner PhoenixSuit tool to download to A80 board. Choose the output image(a80_android_board.img), select download and wait for the download to complete.

4.5.5 Boot and run the software on A80 Board

When the host platform is Windows, use a console application to connect A80 board uart0. In the console window, You can install OP-TEE linux kernel driver optee.ko, load OP-TEE-Client daemon tee-supplicant and run the example "hello world" Trusted Application, do this by running:

$ insmod /system/vendor/modules/optee.ko
$ /system/bin/tee-supplicant &
$ /system/bin/tee-helloworld

4.6 Freescale MX6UL EVK

Get U-Boot source: https://github.com/MrVan/uboot/commit/4f016adae573aaadd7bf6a37f8c58a882b391ae6

Build U-Boot:

    make ARCH=arm mx6ul_14x14_evk_optee_defconfig
    make ARCH=arm
    Burn u-boot.imx to offset 0x400 of SD card

Get Kernel source: https://github.com/linaro-swg/linux/tree/optee

Patch kernel:

    diff --git a/arch/arm/boot/dts/imx6ul-14x14-evk.dts b/arch/arm/boot/dts/imx6ul-14x14-evk.dts
    index 6aaa5ec..2ac9c80 100644
    --- a/arch/arm/boot/dts/imx6ul-14x14-evk.dts
    +++ b/arch/arm/boot/dts/imx6ul-14x14-evk.dts
    @@ -23,6 +23,13 @@
        reg = <0x80000000 0x20000000>;
     };

    +    firmware {
    +        optee {
    +            compatible = "linaro,optee-tz";
    +            method = "smc";
    +        };
    +    };
    +
    regulators {
        compatible = "simple-bus";
        #address-cells = <1>;

Compile the Kernel:

make ARCH=arm imx_v6_v7_defconfig
make menuconfig
select the two entries
    CONFIG_TEE=y
    CONFIG_OPTEE
make ARCH=arm

Copy zImage and imx6ul_14x14_evk.dtb to SD card.

OPTEE OS Build:

    PLATFORM_FLAVOR=mx6ulevk make PLATFORM=imx
    ${CROSS_COMPILE}-objcopy -O binary out/arm-plat-imx/core/tee.elf optee.bin
    copy optee.bin to the first partition of SD card which is used for boot.

Run using U-Boot:

    run loadfdt;
    run loadimage;
    fatload mmc 1:1 0x9c100000 optee.bin;
    run mmcargs;
    bootz ${loadaddr} - ${fdt_addr};

Note: CAAM is not implemented now, this will be added later.

More steps: http://mrvan.github.io/optee-imx6ul


5. repo manifests

A Git repository is available at https://github.com/OP-TEE/manifest where you will find XML-files for use with the Android 'repo' tool.

5.1. Install repo

Follow the instructions under the "Installing Repo" section here.

5.2. Get the source code

First ensure that you have the necessary Ubuntu packages installed, see 4.1 Prerequisites (this is the only important step from section 4 in case you are setting up any of the target devices mentioned below).

$ mkdir -p $HOME/devel/optee
$ cd $HOME/devel/optee
$ repo init -u https://github.com/OP-TEE/manifest.git -m ${TARGET}.xml [-b ${BRANCH}]
$ repo sync

Notes

  • The folder could be at any location, we are just giving a suggestion by saying $HOME/devel/optee.
  • repo sync can take an additional parameter -j to sync multiple remotes. For example repo sync -j3 will sync three remotes in parallel.

5.2.1 Targets

Target Latest Stable
QEMU default.xml default_stable.xml
QEMUv8 qemu_v8.xml qemu_v8_stable.xml
FVP fvp.xml fvp_stable.xml
HiKey hikey.xml hikey_stable.xml
HiKey Debian hikey_debian.xml hikey_debian_stable.xml
MediaTek MT8173 EVB Board mt8173-evb.xml mt8173-evb_stable.xml
ARM Juno board juno.xml juno_stable.xml
Raspberry Pi 3 rpi3.xml rpi3_stable.xml

5.2.2 Branches

Currently we are only using one branch, i.e, the master branch.

5.2.3 Get the toolchains

This is a one time thing you run only once after getting all the source code using repo.

$ cd build
$ make toolchains
Note :

If you have been using GCC4.9 and are upgrading to GCC5 via [this commit] (https://github.com/OP-TEE/build/commit/69a8a37bc417d28d62ae57e7ca2a8df4bdec93c8), please make sure that you delete the toolchains directory before running make toolchains again, or else the toolchain binaries can get mixed up or corrupted, and generate errors during builds.


5.3. QEMU

After getting the source and toolchain, just run (from the build folder)

$ make all run

and everything should compile and at the end QEMU should start.


5.4. FVP

After getting the source and toolchain you must also obtain Foundation Model (link) binaries and untar it to the forest root, then just run (from the build folder)

$ make all run

and everything should compile and at the end FVP should start.


5.5. HiKey

5.5.1 Initramfs based

After getting the source and toolchain, just run (from the build folder)

$ make all

After that connect the board and flash the binaries by running:

$ make flash

(more information about how to flash individual binaries could be found here)

The board is ready to be booted.

5.5.2 Debian based / 96boards RPB

Start by getting the source and toolchain (see above), then continue by downloading the system image (root fs). Note that this step is something you only should do once.

$ make system-img

Which should be followed by

$ make all

When everything has been built, flash the files to the device:

$ make flash

Now you can boot up the device, note that OP-TEE normal world binaries still hasn't been put on the device at this stage. So by now you're basically booting up an RPB build. When you have a prompt, the next step is to connect the device to the network. WiFi is preferable, since HiKey has no Ethernet jack. Easiest is to edit /etc/network/interfaces. To find out what to add, run:

$ make help

When that's been added, reboot and when you have a prompt again, you're ready to push the OP-TEE client binaries and the kernel with OP-TEE support. First find out the IP for your device (ifconfig). Then send the files to HiKey by running:

$ IP=111.222.333.444 make send

Credentials for the image are:
username: linaro
password: linaro

When the files has been transfered, please follow the commands from the make send command which will install the debian packages on the device. Typically it tells you to run something like this on the device itself:

$ dpkg --force-all -i /tmp/out/optee_2.0-1.deb
$ dpkg --force-all -i /tmp/linux-image-*.deb

Now you are ready to use OP-TEE on HiKey using Debian, please goto step 6 below to continue.

Good to know

Just want to update secure side? Put the device in fastboot mode and

$ make arm-tf
$ make flash-fip

Just want to update OP-TEE client software? Put the device in fastboot mode and

$ make optee-client
$ make xtest

Boot up the device and follow the instructions from make send

$ IP=111.222.333.444 make send

5.6. MT8173-EVB

After getting the source and toolchain, just run (from the build folder)

$ make all run

When < waiting for device > prompt appears, press reset button and the flashing procedure should begin.


5.7 Juno

After getting the source and toolchain, just run (from the build folder)

$ make all

Enter the firmware console on the juno board and press enter to stop the auto boot flow

ARM V2M_Juno Firmware v1.3.9
Build Date: Nov 11 2015

Time :  12:50:45
Date :  29:03:2016

Press Enter to stop auto boot...

Enable ftp at the firmware prompt

Cmd> ftp_on
Enabling ftp server...
 MAC address: xxxxxxxxxxxx

 IP address: 192.168.1.158

 Local host name = V2M-JUNO-A2

Flash the binary by running (note the IP address from above):

make JUNO_IP=192.168.1.158 flash

Once the binaries are transferred, reboot the board:

Cmd> reboot

5.7.1 Update flash and its layout

The flash in the board may need to be updated for the flashing above to work. If the flashing fails or if ARM-TF refuses to boot due to wrong version of the SCP binary the flash needs to be updated. To update the flash please follow the instructions at Using Linaro's deliverable on Juno selecting one of the zips under "4.1 Prebuilt configurations" flashing it as described under "5. Running the software".

5.7.2 GlobalPlatform testsuite support

Warning :

Depending on the Juno pre-built configuration, the built ramdisk.img size with GlobalPlatform testsuite may exceed its pre-defined Juno flash memory reserved location (image.txt file). In that case, you will need to extend the Juno flash block size reserved location for the ramdisk.img in the image.txt file accordingly and follow the instructions under "5.7.1 Update flash and its layout".

Example with juno-latest-busybox-uboot.zip:

The current ramdisk.img size with GlobalPlatform testsuite is 8.6 MBytes.

Updated file is /JUNO/SITE1/HBI0262B/images.txt (limited to 8.3 MB)
NOR4UPDATE: AUTO                 ;Image Update:NONE/AUTO/FORCE
NOR4ADDRESS: 0x01800000          ;Image Flash Address
NOR4FILE: \SOFTWARE\ramdisk.img  ;Image File Name
NOR4NAME: ramdisk.img
NOR4LOAD: 00000000               ;Image Load Address
NOR4ENTRY: 00000000              ;Image Entry Point
Extended to 16MB
NOR4UPDATE: AUTO                 ;Image Update:NONE/AUTO/FORCE
NOR4ADDRESS: 0x01000000          ;Image Flash Address
NOR4FILE: \SOFTWARE\ramdisk.img  ;Image File Name
NOR4NAME: ramdisk.img
NOR4LOAD: 00000000               ;Image Load Address
NOR4ENTRY: 00000000              ;Image Entry Point

5.7.3 GCC5 support

Note :

In case you are using the Latest version of the ARM Juno board (this is juno.xml manifest), the built ramdisk.img size with GCC5 compiler, at the moment, exceeds its pre-defined Juno flash memory reserved location (image.txt file).

To solve this problem you will need to extend the Juno flash block size reserved location for the ramdisk.img and decrease the size for other images in the image.txt file accordingly and then follow the instructions under "5.7.1 Update flash and its layout".

Example with juno-latest-busybox-uboot.zip:

The current ramdisk.img size with GCC5 compiler is 29.15 MBytes we will extend it to 32 MBytes. The only changes that you need to do are those in bold

File to update is /JUNO/SITE1/HBI0262B/images.txt
NOR2UPDATE: AUTO                 ;Image Update:NONE/AUTO/FORCE
NOR2ADDRESS: 0x00100000          ;Image Flash Address
NOR2FILE: \SOFTWARE\Image        ;Image File Name
NOR2NAME: norkern                ;Rename kernel to norkern
NOR2LOAD: 00000000               ;Image Load Address
NOR2ENTRY: 00000000              ;Image Entry Point

NOR3UPDATE: AUTO                 ;Image Update:NONE/AUTO/FORCE
NOR3ADDRESS: 0x02C00000          ;Image Flash Address
NOR3FILE: \SOFTWARE\juno.dtb     ;Image File Name
NOR3NAME: board.dtb              ;Specify target filename to preserve file extension
NOR3LOAD: 00000000               ;Image Load Address
NOR3ENTRY: 00000000              ;Image Entry Point

NOR4UPDATE: AUTO                 ;Image Update:NONE/AUTO/FORCE
NOR4ADDRESS: 0x00D00000          ;Image Flash Address
NOR4FILE: \SOFTWARE\ramdisk.img  ;Image File Name
NOR4NAME: ramdisk.img
NOR4LOAD: 00000000               ;Image Load Address
NOR4ENTRY: 00000000              ;Image Entry Point

NOR5UPDATE: AUTO                 ;Image Update:NONE/AUTO/FORCE
NOR5ADDRESS: 0x02D00000          ;Image Flash Address
NOR5FILE: \SOFTWARE\hdlcdclk.dat ;Image File Name
NOR5LOAD: 00000000               ;Image Load Address
NOR5ENTRY: 00000000              ;Image Entry Point

5.8 Raspberry Pi 3

There is a separate document for Raspberry Pi 3 here. That document will tell you how to flash, how to debug, known problems and things still to be done.


5.9 Tips and tricks

5.9.1 Reference existing project to speed up repo sync

Doing a repo init, repo sync from scratch can take a fair amount of time. The main reason for that is simply because of the size of some of the gits we are using, like for the Linux kernel and EDK2. With repo you can reference an existing forest and by doing so you can speed up repo sync to instead taking ~20 seconds instead of an hour. The way to do this are as follows.

  1. Start by setup a clean forest that you will not touch, in this example, let us call that optee-ref and put that under for $HOME/devel/optee-ref. This step will take roughly an hour.
  2. Then setup a cronjob (crontab -e) that does a repo sync in this folder particular folder once a night (that is more than enough).
  3. Now you should setup your actual tree which you are going to use as your working tree. The way to do this is almost the same as stated in the instructions above, the only difference is that you reference the other local forest when running repo init, like this
    repo init -u https://github.com/OP-TEE/manifest.git --reference /home/jbech/devel/optee-ref
  4. The rest is the same above, but now it will only take a couple of seconds to clone a forest.

Normally step 1 and 2 above is something you will only do once. Also if you ignore step 2, then you will still get the latest from official git trees, since repo will also check for updates that aren't at the local reference.

5.9.2. Use ccache

ccache is a tool that caches build object-files etc locally on the disc and can speed up build time significantly in subsequent builds. On Debian-based systems (Ubuntu, Mint etc) you simply install it by running:

$ sudo apt-get install ccache

The helper makefiles are configured to automatically find and use ccache if ccache is installed on your system, so other than having it installed you don't have to think about anything.

5.9.3 Host-Guest folder sharing in QEMU/QEMUv8 configurations

To avoid changing rootfs CPIO archive each time you need to add additional files to it, you can also use VirtFS QEMU feature to share a folder between the guest and host operating systems. To use this feature enable VirtFS QEMU build in build/common.mk (set QEMU_VIRTFS_ENABLE ?= y), adjust QEMU_VIRTFS_HOST_DIR and rebuild QEMU.

To mount host folder in QEMU, simply run:

$ mount_shared <mount_point>

6. Load driver, tee-supplicant and run xtest

Since release v2.0.0 you don't have to load the kernel driver explicitly. In the standard configuration it will be built into the kernel directly. To actually run something on a device you however need to run tee-supplicant. This is the same for all platforms, so when a device has booted, then run

$ tee-supplicant &

and OP-TEE is ready to be used.

In case you want to try run something that triggers both normal and secure side code you could run xtest (the main test suite for OP-TEE), run

$ xtest

7. Coding standards

In this project we are trying to adhere to the same coding convention as used in the Linux kernel (see CodingStyle). We achieve this by running checkpatch from Linux kernel. However there are a few exceptions that we had to make since the code also follows GlobalPlatform standards. The exceptions are as follows:

  • CamelCase for GlobalPlatform types are allowed.
  • And we also exclude checking third party code that we might use in this project, such as LibTomCrypt, MPA, newlib (not in this particular git, but those are also part of the complete TEE solution). The reason for excluding and not fixing third party code is because we would probably deviate too much from upstream and therefore it would be hard to rebase against those projects later on (and we don't expect that it is easy to convince other software projects to change coding style).

7.1 checkpatch

Since checkpatch is licensed under the terms of GNU GPL License Version 2, we cannot include this script directly into this project. Therefore we have written the Makefile so you need to explicitly point to the script by exporting an environment variable, namely CHECKPATCH. So, suppose that the source code for the Linux kernel is at $HOME/devel/linux, then you have to export like follows:

$ export CHECKPATCH=$HOME/devel/linux/scripts/checkpatch.pl

thereafter it should be possible to use one of the different checkpatch targets in the Makefile. There are targets for checking all files, checking against latest commit, against a certain base-commit etc. For the details, read the Makefile.