2. Getting a working Environment

2.1. Download Software Components

In order to follow this manual, some software archives are needed. There are several possibilities how to get these: either as part of an evaluation board package or by downloading them from the Pengutronix web site.

The central place for OSELAS related documentation is http://www.oselas.com and http://www.ptxdist.org. These websites provide all required packages and documentation (at least for software components which are available to the public).

In order to build OSELAS.BSP-Pengutronix-Example, the following source archives have to be available on the development host:

  • ptxdist-2017.12.0.tar.bz2
  • OSELAS.BSP-Pengutronix-Example.tar.bz2 (or a similar source)
  • ptxdist-2016.06.0.tar.bz2
  • OSELAS.Toolchain-2016.06.1.tar.bz2

Main Parts of PTXdist

The most important software component which is necessary to build an OSELAS.BSP( ) board support package is the ptxdist tool. So before starting any work we’ll have to install PTXdist on the development host.

PTXdist consists of the following parts:

The ptxdist Program:
ptxdist is installed on the development host during the installation process. ptxdist is called to trigger any action, like building a software packet, cleaning up the tree etc. Usually the ptxdist program is used in a workspace directory, which contains all project relevant files.
A Configuration System:
The config system is used to customize a configuration, which contains information about which packages have to be built and which options are selected.
Patches:
Due to the fact that some upstream packages are not bug free – especially with regard to cross compilation – it is often necessary to patch the original software. PTXdist contains a mechanism to automatically apply patches to packages. The patches are bundled into a separate archive. Nevertheless, they are necessary to build a working system.
Package Descriptions:
For each software component there is a “recipe” file, specifying which actions have to be done to prepare and compile the software. Additionally, packages contain their configuration sniplet for the config system.
Toolchains:

PTXdist does not come with a pre-built binary toolchain. Nevertheless, PTXdist itself is able to build toolchains, which are provided by the OSELAS.Toolchain() project. More in-deep information about the OSELAS.Toolchain() project can be found here: http://www.pengutronix.de/oselas/toolchain/index_en.html

Building a toolchain is not part of this manual, refer for application note “Building Toolchains” instead.

Board Support Package
This is an optional component, mostly shipped aside with a piece of hardware. There are various BSP available, some are generic, some are intended for a specific hardware.

Extracting the Sources

Important

Do the following steps at best in your own home directory ($HOME). You need root permissions only in the make install step, and nowhere else.

To install PTXdist, the archive Pengutronix provides has to be extracted:

ptxdist-2017.12.0.tar.bz2
The PTXdist software itself

The PTXdist archive has to be extracted into some temporary directory in order to be built before the installation, for example the local/ directory in the user’s home. If this directory does not exist, we have to create it and change into it:

$ cd
$ mkdir local
$ cd local

Next step is to extract the archive:

$ tar -xjf ptxdist-2017.12.0.tar.bz2

If everything goes well, we now have a ptxdist-2017.12.0 directory, so we can change into it:

$ cd ptxdist-2017.12.0
$ ls -lF
total 396
-rw-r--r--   1 jbe ptx  18446 Apr 29 09:36 COPYING
-rw-r--r--   1 jbe ptx   3933 Apr 29 09:36 CREDITS
-rw-r--r--   1 jbe ptx     57 Apr 29 09:36 INSTALL
-rw-r--r--   1 jbe ptx   4483 Apr 29 09:36 Makefile.in
-rw-r--r--   1 jbe ptx   3501 Apr 29 09:36 README
-rw-r--r--   1 jbe ptx   2324 Apr 29 09:36 README.devel
-rwxr-xr-x   1 jbe ptx     28 Apr 29 09:36 autogen.sh*
drwxr-xr-x   2 jbe ptx   4096 Apr 29 09:36 bin/
drwxr-xr-x  16 jbe ptx   4096 Apr 29 09:36 config/
-rwxr-xr-x   1 jbe ptx 214583 Apr 29 15:55 configure*
-rw-r--r--   1 jbe ptx  12570 Apr 29 09:36 configure.ac
drwxr-xr-x   4 jbe ptx   4096 Apr 29 09:36 doc/
drwxr-xr-x   2 jbe ptx   4096 Jun 21 09:52 man/
drwxr-xr-x 263 jbe ptx  12288 Apr 29 09:36 patches/
drwxr-xr-x   2 jbe ptx   4096 Apr 29 09:36 platforms/
drwxr-xr-x   4 jbe ptx   4096 Apr 29 09:36 plugins/
drwxr-xr-x  11 jbe ptx   4096 Apr 29 09:36 projectroot/
drwxr-xr-x   6 jbe ptx  69632 Apr 29 09:36 rules/
drwxr-xr-x   9 jbe ptx   4096 Apr 29 09:36 scripts/
drwxr-xr-x   2 jbe ptx   4096 Apr 29 09:36 tests/

Prerequisites

Before PTXdist can be installed it has to check if all necessary programs are installed on the development host (e.g. external dependencies). The configure script will stop if it discovers that something is missing.

The PTXdist installation is based on GNU autotools, so the first thing to be done now is to configure the package:

$ ./configure

This will check your system for required components PTXdist relies on. If all required components are found the output ends with:

[...]
checking whether Python development files are present... yes
checking for patch... /usr/bin/patch
checking whether /usr/bin/patch will work... yes

configure: creating ./config.status
config.status: creating Makefile

ptxdist version 2017.12.0 configured.
Using '/usr/local' for installation prefix.

Report bugs to ptxdist@pengutronix.de

Without further arguments PTXdist is configured to be installed into /usr/local, which is the standard location for user installed programs. To change the installation path to anything non-standard, we use the --prefix argument to the configure script. The --help option offers more information about what else can be changed for the installation process.

The installation paths are configured in a way that several PTXdist versions can be installed in parallel. So if an old version of PTXdist is already installed, there is no need to remove it.

One of the most important tasks for the configure script is to find out if all the programs PTXdist depends on are already present on the development host. The script will stop with an error message in case something is missing. If this happens, the missing tools have to be installed from the distribution befor re-running the configure script.

When the configure script is finished successfully, we can now run

$ make

All program parts are being compiled, and if there are no errors we can now install PTXdist into it’s final location. In order to write to /usr/local, this step has to be performed as user root:

$ sudo make install
[enter password]
[...]

If we don’t have root access to the machine it is also possible to install PTXdist into some different directory with the --prefix option. We need to take care that the bin/ directory below the new installation dir is added to our $PATH environment variable (for example by exporting it in ~/.bashrc).

The installation is now done, so the temporary folder may now be removed:

$ cd ../../
$ rm -fr local

Configuring PTXdist

When using PTXdist for the first time, some setup properties have to be configured. Two settings are the most important ones: where to store the source archives and if a proxy must be used to gain access to the world wide web.

Run PTXdist’s setup:

$ ptxdist setup

Due to the fact that PTXdist is working with sources only, it needs various source archives from the world wide web. If these archives are not present on our host, PTXdist starts the wget command to download them on demand.

Proxy Setup

To do so, an internet access is required. If this access is managed by a proxy wget command must be advised to use it. PTXdist can be configured to advise the wget command automatically: navigate to entry Proxies and enter the required addresses and ports to access the proxy in the form:

<protocol>://<address>:<port>

Source Archive Location

Whenever PTXdist downloads source archives it stores these archives in a project local manner. This is the default behaviour. If we are working with more than one PTXdist based project, every project would download its own required archives in this case. To share all source archives between all projects, PTXdist can be configured to share only one archive directory for all projects it handles: navigate to menu entry Source Directory and enter the path to the directory where PTXdist should store archives to share between its projects.

2.2. Toolchains

Before we can start building our first userland we need a cross toolchain. On Linux, toolchains are no monolithic beasts. Most parts of what we need to cross compile code for the embedded target comes from the GNU Compiler Collection, gcc. The gcc packet includes the compiler frontend, gcc, plus several backend tools (cc1, g++, ld etc.) which actually perform the different stages of the compile process. gcc does not contain the assembler, so we also need the GNU Binutils package which provides lowlevel stuff.

Cross compilers and tools are usually named like the corresponding host tool, but with a prefix – the GNU target. For example, the cross compilers for ARM and powerpc may look like

arm-softfloat-linux-gnu-gcc

powerpc-unknown-linux-gnu-gcc

With these compiler frontends we can convert e.g. a C program into binary code for specific machines. So for example if a C program is to be compiled natively, it works like this:

$ gcc test.c -o test

To build the same binary for the ARM architecture we have to use the cross compiler instead of the native one:

$ arm-softfloat-linux-gnu-gcc test.c -o test

Also part of what we consider to be the “toolchain” is the run-time library (libc, dynamic linker). All programs running on the embedded system are linked against the libc, which also offers the interface from user space functions to the kernel.

The compiler and libc are very tightly coupled components: the second stage compiler, which is used to build normal user space code, is being built against the libc itself. For example, if the target does not contain a hardware floating point unit, but the toolchain generates floating point code, it will fail. This is also the case when the toolchain builds code for i686 CPUs, whereas the target is i586.

So in order to make things working consistently it is necessary that the run-time libc is identical with the libc the compiler was built against.

PTXdist doesn’t contain a pre-built binary toolchain. Remember that it’s not a distribution but a development tool. But it can be used to build a toolchain for our target. Building the toolchain usually has only to be done once. It may be a good idea to do that over night, because it may take several hours, depending on the target architecture and development host power.

Using existing Toolchains from different Vendors

If a toolchain from a different vendor than OSELAS is already installed which is known to be working, the toolchain building step with PTXdist may be omitted.

The OSELAS.BoardSupport() Packages shipped for PTXdist have been tested with the OSELAS.Toolchains() built with the same PTXdist version. So if an external toolchain is being used which isn’t known to be stable, a target may fail. Note that not all compiler versions and combinations work properly in a cross environment.

Every OSELAS.BoardSupport() Package checks for its OSELAS.Toolchain it’s tested against, so using a toolchain from a different vendor than OSELAS requires an additional step:

Open the OSELAS.BoardSupport() Package menu with:

$ ptxdist platformconfig

and navigate to architecture ---> toolchain and check for specific toolchain vendor. Clear this entry to disable the toolchain vendor check.

Preconditions a toolchain from a different vendor than OSELAS must meet:

  • it shall be built with the configure option --with-sysroot pointing to its own C libraries.
  • it should not support the multilib feature as this may confuse PTXdist which libraries are to select for the root filesystem

If we want to check if our toolchain was built with the --with-sysroot option, we just run this simple command:

$ mytoolchain-gcc -v 2>&1 | grep with-sysroot

If this command does not output anything, this toolchain was not built with the --with-sysroot option and cannot be used with PTXdist.

Omitting building a Toolchain

Pengutronix also provides ’ready to use’ toolchains in a binary manner. These toolchains are built from the OSELAS.Toolchain bundle, so they comply with all of Pengutronix’s board support packages and we can use them instead of building our own one.

The binary OSELAS toolchains are provided as Debian Distribution Packages. Also most non-Debian distributions can handle such packages.

In order to install the OSELAS binary toolchains on a Debian based system the following steps are required:

Add the OSELAS Server as a Package Source

To register the OSELAS package server to the list of known package servers, we add a new file with the name pengutronix.list into the directory /etc/apt/sources.list.d/. The basename of this file isn’t important, while the extension .list is.

The contents of this new file describe the Pengutronix server as an available package source. It is defined via one text line:

deb http://debian.pengutronix.de/debian/ sid main contrib non-free

Note: if the directory /etc/apt/sources.list.d/ does not exist, the text line mentioned above must be added to the file /etc/apt/sources.list instead.

Make the OSELAS Server Content available

The package manager now must update its packages list with the following command:

$ apt-get update

Install the Archive Keyring

To avoid warnings about untrusted package sources we can install the OSELAS archive keyring with the following command:

$ apt-get install pengutronix-archive-keyring

Install the binary OSELAS Toolchain

Now everything is in place to install the binary OSELAS toolchain for the board support package:

$ apt-get install oselas.toolchain-2016.06.1-arm-v5te-linux-gnueabi-<ptxdistCompilerVersion>

These package names are very long and hard to type without making typos. An easier way is to ask the package manager for available toolchains and just use the name by copy and paste it.

$ apt-cache search "oselas.toolchain-.*-arm.*v5te.*"
oselas.toolchain-2016.06.1-arm-v5te-linux-gnueabi-<ptxdistCompilerVersion>

The binary OSELAS Toolchain Package for non-Debian Distributions

The Debian Distribution Packages can be found on our server at http://debian.pengutronix.de/debian/pool/main/o/

The related OSELAS toolchain package can be found here:

Subpath is:

oselas.toolchain-2016.06.1-arm-v5te-linux-gnueabi-gcc-5.4.0-glibc-2.23-binutils-2.26-kernel-4.6-sanitized/

Package filename is:

oselas.toolchain-2016.06.1-arm-v5te-linux-gnueabi-gcc-5.4.0-glibc-2.23-binutils-2.26-kernel-4.6-sanitized*.deb

Package filenames for 32 bit host machines are ending on *_i386.deb and for 64 bit host machines on *_amd64.deb.

Building a Toolchain

If there is no different toolchain available yet, the next step is to build one at least for the desired target architecture.

PTXdist handles toolchain building as a simple project, like all other projects, too. So we can download the OSELAS.Toolchain bundle and build the required toolchain for the OSELAS.BoardSupport() Package.

Building any toolchain of the OSELAS.Toolchain-2016.06.1 is tested with PTXdist-2016.06.0. Pengutronix recommends to use this specific PTXdist to build the toolchain. So, it might be essential to install more than one PTXdist revision to build the toolchain and later on the Board Support Package if the latter one is made for a different PTXdist revision.

A PTXdist project generally allows to build into some project defined directory; all OSELAS.Toolchain projects that come with PTXdist are configured to use the standard installation paths mentioned below.

All OSELAS.Toolchain projects install their result into /opt/OSELAS.Toolchain-2016.06.1/.

Usually the /opt directory is not world writeable. So in order to build our OSELAS.Toolchain into that directory we need to use a root account to change the permissions. PTXdist detects this case and asks if we want to run sudo to do the job for us. Alternatively we can enter:

$ mkdir /opt/OSELAS.Toolchain-2016.06.1
$ chown <username> /opt/OSELAS.Toolchain-2016.06.1
$ chmod a+rwx /opt/OSELAS.Toolchain-2016.06.1

We recommend to keep this installation path as PTXdist expects the toolchains at /opt. Whenever we go to select a platform in a project, PTXdist tries to find the right toolchain from data read from the platform configuration settings and a toolchain at /opt that matches to these settings. But that’s for our convenience only. If we decide to install the toolchains at a different location, we still can use the toolchain parameter to define the toolchain to be used on a per project base.

Building the OSELAS.Toolchain for OSELAS.BSP-Pengutronix-Example

Do the following steps in your own home directory ($HOME). The final OSELAS.Toolchain gets installed to opt/, but must never be compiled in the opt/ directory. You will get many funny error messages, if you try to compile the OSELAS-Toolchain in opt/.

To compile and install an OSELAS.Toolchain we have to extract the OSELAS.Toolchain archive, change into the new folder, configure the compiler in question and start the build.

The required compiler to build the board support package is

arm-v5te-linux-gnueabi_gcc-5.4.0_glibc-2.23_binutils-2.26_kernel-4.6-sanitized.ptxconfig

Important

Please ensure the ’current directory’ (the . entry) is not part of your PATH environment variable. PTXdist tries to sort out this entry, but might not be successful in doing so. Check by running ptxdist print PATH if the output still contains any kind of ’current directory’ as a component. If yes, remove it first.

So the steps to build this toolchain are:

$ tar xf OSELAS.Toolchain-2016.06.1.tar.bz2
$ cd OSELAS.Toolchain-2016.06.1
$ ptxdist-2016.06.0 select ptxconfigs/arm-v5te-linux-gnueabi_gcc-5.4.0_glibc-2.23_binutils-2.26_kernel-4.6-sanitized.ptxconfig
$ ptxdist-2016.06.0 go

At this stage we have to go to our boss and tell him that it’s probably time to go home for the day. Even on reasonably fast machines the time to build an OSELAS.Toolchain is something like around 30 minutes up to a few hours.

Measured times on different machines:

  • Single Pentium 2.5 GHz, 2 GiB RAM: about 2 hours
  • Turion ML-34, 2 GiB RAM: about 1 hour 30 minutes
  • Dual Athlon 2.1 GHz, 2 GiB RAM: about 1 hour 20 minutes
  • Dual Quad-Core-Pentium 1.8 GHz, 8 GiB RAM: about 25 minutes
  • 24 Xeon cores 2.54 GHz, 96 GiB RAM: about 22 minutes

Another possibility is to read the next chapters of this manual, to find out how to start a new project.

When the OSELAS.Toolchain project build is finished, PTXdist is ready for prime time and we can continue with our first project.

Protecting the Toolchain

All toolchain components are built with regular user permissions. In order to avoid accidential changes in the toolchain, the files should be set to read-only permissions after the installation has finished successfully. It is also possible to set the file ownership to root. This is an important step for reliability, so it is highly recommended.

Building additional Toolchains

The OSELAS.Toolchain- bundle comes with various predefined toolchains. Refer the ptxconfigs/ folder for other definitions. To build additional toolchains we only have to clean our current toolchain project, removing the current selected_ptxconfig link and creating a new one.

$ ptxdist clean
$ rm selected_ptxconfig
$ ptxdist select ptxconfigs/any_other_toolchain_def.ptxconfig
$ ptxdist go

All toolchains will be installed side by side architecture dependent into directory

/opt/OSELAS.Toolchain-2016.06.1/<architecture>

Different toolchains for the same architecture will be installed side by side version dependent into directory

/opt/OSELAS.Toolchain-2016.06.1/<architecture>/<version>