15.4. Third-Party Packages¶

This section describes how to build and add an RTEMS third-party package to the RSB.

A third-party package is a library or software package built to run on RTEMS, examples are Curl, NTP, Net-Snmp, libjpeg and more. These pieces of software can be used to help build RTEMS applications. The package is built for a specific BSP and so requires a working RTEMS tool chain, an installed RTEMS Board Support Package (BSP), and a network stack if the package uses networking resources.

The RSB support for building third-party packages is based around the pkconfig files (PC) installed with the BSP. The pkgconfig support in RTEMS is considered experimental and can have some issues for some BSPs. This issue is rooted deep in the RTEMS build system.

15.4.1. Vertical Integration¶

The RSB supports horizontal integration with support for multiple architectures. Adding packages to the RSB as libraries is vertical integration. Building the GCC tool chain requires you build an assembler before you build a compiler. The same can be done for third-party libraries, you can create build sets that stack library dependences vertically to create a stack.

15.4.2. Building¶

To build a package you need to have a suitable RTEMS tool chain and RTEMS BSP installed. The set builder command line requires you provide the tools path, the RTEMS architecture (host), the BSP, and the prefix path used to the install RTEMS BSP.

The RSB prefix option (--prefix) provided when building a package is the path to:

The tools, RTEMS kernel and any dependent libraries such as LibBSD. The package will be installed into the prefix path. This build configuration can be used to make a complete set of development tools and libraries for a project or product under a single path.
The RTEMS kernel and any dependent libraries such as LibBSD. The tools path needs to be in the environment path (not recommended) or provided to the set builder command by the --with-tools option. The package will be installed into the prefix path. This build configuration can be used when you have a set of tools used with a number of RTEMS BSPs. The tools can be shared between the different BSPs.
The path the package is installed into. The tools path needs to be in the environment path (not recommended) or provided to the set builder command using the --with-tools option. The path to the RTEMS kernel and any dependent libraries such as LibBSD needs to be supplied to the set builder command using the --with-rtems option. This build configuration can be used when you have a set of libraries you are testing with a changing RTEMS kernel. Becareful using this configuration as changes in RTEMS interfaces may require rebuilding these packages.

The set builder command option --host is used to provide the RTEMS architecture the package is being built for. For example --host=arm-rtems5 is used for any ARM BSP.

The set builder command option --with-rtems-bsp is the RTEMS BSP the package is being built for. The BSP is searched for under the path provided by the command option --with-rtems and if this option is not provided the provided prefix is searched.

The following example builds and installs the Curl networking package for the ARM BeagleBone Black BSP installing it into the same path the tools, RTEMS kernel and LibBSD are installed in.

$ ../source-builder/sb-set-builder --prefix=$HOME/development/cs/rtems/5 \
      --log=curl.txt --host=arm-rtems5 --with-rtems-bsp=beagleboneblack ftp/curl
RTEMS Source Builder - Set Builder, 5 (2bdae1f169e4)
Build Set: ftp/curl
config: ftp/curl-7.65.1-1.cfg
package: curl-v7.65.1-arm-rtems5-1
download: https://curl.haxx.se/download/curl-7.65.1.tar.xz -> sources/curl-7.65.1.tar.xz
downloading: sources/curl-7.65.1.tar.xz - 2.3MB of 2.3MB (100%)
building: curl-v7.65.1-arm-rtems5-1
sizes: curl-v7.65.1-arm-rtems5-1: 87.055MB (installed: 2.238MB)
cleaning: curl-v7.65.1-arm-rtems5-1
reporting: ftp/curl-7.65.1-1.cfg -> curl-v7.65.1-arm-rtems5-1.txt
reporting: ftp/curl-7.65.1-1.cfg -> curl-v7.65.1-arm-rtems5-1.xml
installing: curl-v7.65.1-arm-rtems5-1 -> /Users/chris/development/cs/rtems/5
cleaning: curl-v7.65.1-arm-rtems5-1
Build Set: Time 0:01:10.006872

15.4.3. Adding¶

Adding a package requires you first build it manually by downloading the source for the package and building it for RTEMS using the command line of a standard shell. If the package has not been ported to RTEMS you will need to port it and this may require asking questions on the package’s user or development support lists as well as RTEMS’s developers list. Your porting effort may end up with a patch. RTEMS requires a patch be submitted upstream to the project’s community as well as RTEMS. The RTEMS submission is best as a patch attached to ticket in Trac. A patch attached to a ticket can be referenced by an RSB configuration file and used in a build.

A package may create executables, for example Curl normally creates an executable called curl how ever it will probailty not run because the needed RTEMS configuration is not suitable. If found the RSB automatically adds the RTEMS library librtemsdefaultconfig.a to the LIBS variable used to link executables. This library provides a limited configuraiton suitable for linking an executable however it is not a set up that allows the resulting executable to run correctly. As a result it is best not to install these executables.

A custom RTEMS patch to an executate’s source code can turn it into a function that can be called by the RTEMS shell. Users can call the function in their executables simulating the running of the package’s command. If the package does not export the code in a suitable manner please contact the project’s community and see if you can work with them to provide a way for the code to be exported. This may be difficult because exporting internal headers and functions opens the project up to API compatibility issues they did not have before. In the simplest case attempting to get the code into a static library with a single call entry point exported in a header would give RTEMS user’s access to the package’s main functionality.

A package requires at least three (3) files to be created:

Published Package Name:
The first file is the RTEMS build set file and it resides under the rtems/config path in a directory tree based on the FreeBSD ports collection. For the Curl package and RTEMS 5 this is rtems/config/ftp/curl.bset. If you do not know the FreeBSD port path for the package you are adding please ask. The build set file references a specific configuration file therefore linking the RTEMS version to a specific version of the package you are adding. Updating the package to a new version requires changing the build set to the new configuration file.

Package Version Configuration File:
The second file is an RTEMS version specific configuration file and it includes the RSB RTEMS BSP support. These configuration files reside in the rtems/config tree and under the FreeBSD port’s path name. For example the Curl package is found in the ftp directory of the FreeBSD ports tree so the Curl configuration path is rtems/config/ftp/curl-7.65.1-1.cfg for that specific version. The configuration file name typically provides version specific references and the RTEMS build set file references a specific version. This configuration file references the build configuration file held in the common configuration file tree. An SHA512 hash is required to verify the source package that is downloaded.

Build Configuration File:
The build configuration. This is a common script that builds the package. It resides in the source-builder/config directory and typically has the packages’s name with the major version number. If the build script does not change for each major version number a common base script can be created and included by each major version configuration script. The gcc compiler configuration is an example. This approach lets you branch a version if something changes that is not backwards compatible. It is important to keep existing versions building. The build configuration should be able to build a package for the build host as well as RTEMS as the RSB abstracts the RTEMS specific parts. See Configuration for more details.

15.4.4. Host and Build Flags¶

A package’s build is controlled by setting the compiler names and flags that are used when building. The RSB provides a macro called %{host_build_flags} to define these flags for you. Use this macro in the `%build section of your config script file to define the set up needed to build a native package or to cross-compile to a specific host such as RTEMS . The typical %build section is:

%build
  build_top=$(pwd)

  %{build_directory}

  mkdir -p ${build_dir}
  cd ${build_dir}

  %{host_build_flags}

  ../${source_dir_curl}/configure \
    --host=%{_host} \
    --prefix=%{_prefix} \
    --bindir=%{_bindir} \
    --exec_prefix=%{_exec_prefix} \
    --includedir=%{_includedir} \
    --libdir=%{_libdir} \
    --libexecdir=%{_libexecdir} \
    --mandir=%{_mandir} \
    --infodir=%{_infodir} \
    --datadir=%{_datadir}

  %{__make} %{?_smp_mflags} all

  cd ${build_top}

The %{host_build_flags} checks if the build is native for the development host or a cross-compile build.

For a cross-complication build the flags are:

CC, CC_FOR_HOST:: The C compiler used to build the package. For an RTEMS build this is the RTEMS C compiler. For example the ARM architecture and RTEMS 5 the value is set to arm-rtems5-gcc.
CXX, CXX_FOR_HOST:: The C++ compiler used to build the package. For an RTEMS build this is the RTEMS C++ compiler. For example the ARM architecture and RTEMS 5 the value is set to arm-rtems5-g++.
CPPFLAGS, CPPFLAGS_FOR_HOST:: The C compiler preprocessor flags used to build the package. Set any include paths in this variable as some configure scripts will warns you if include paths are set in the CFLAGS.
CFLAGS, CFLAGS_FOR_HOST:: The C compiler flags used when running the C compiler. Set any include paths in the CPPFLAGS variable as some configure scripts will warn you if include paths in this variable.
CXXFLAGS, CXXFLAGS_FOR_HOST:: The C++ compiler flags used when running the C++ compiler. Set any include paths in the CPPFLAGS variable as some configure scripts will warn you if include paths in this variable.
LDFLAGS, LDFLAGS_FOR_HOST:: The linker flags used whne link package executables. The C or C++ compiler is used to run the linker.
LIBS, LIBS_FOR_HOST:: A list of libraries passed to the linker when linking an executable.
CC_FOR_BUILD:: The native C compiler.
CXX_FOR_BUILD:: The native C++ compiler.
CPPFLAGS_FOR_BUILD:: The C preprocessor flags used when preprocessoring a native C source file.
CFLAGS_FOR_BUILD:: The native C compiler flags used when running the native C compiler.
CXXFLAGS_FOR_BUILD:: The native C++ compiler flags used when running the native C++ compiler.
LDFLAGS_FOR_BUILD:: The native linker flags used when linking a native executable.
LIBS_FOR_BUILD:: The native libraries used to when linking a native executable.

For a native build the flags are:

CC, CC_FOR_BUILD:: The native C compiler.
CXX, CXX_FOR_BUILD:: The native C++ compiler.
CPPFLAGS, CPPFLAGS_FOR_BUILD:: The C preprocessor flags used when preprocessoring a native C source file.
CFLAGS, CFLAGS_FOR_BUILD:: The native C compiler flags used when running the native C compiler.
CXXFLAGS, CXXFLAGS_FOR_BUILD:: The native C++ compiler flags used when running the native C++ compiler.
LDFLAGS, LDFLAGS_FOR_BUILD:: The native linker flags used when linking a native executable.
LIBS, LIBS_FOR_BUILD:: The native libraries used to when linking a native executable.

15.4.5. BSP Support¶

The RSB provides support to build packages for RTEMS. RTEMS applications can be viewed as statically linked executables operating in a single address space. As a result only the static libraries a package builds are required and these libraries need to be ABI compatible with the RTEMS kernel and application code. This means the compiler ABI flags used to build all the code in the executable must be the same. A 3rd party package must use the same compiler flags as the BSP used to build RTEMS.

Note

RTEMS’s dynamic loading support does not use the standard shared library support found in Unix and the ELF standard. RTEMS’s loader uses static libraries and the runtime link editor performs a similar function to a host based static linker. RTEMS will only reference static libraries even if dynamic libraries are created and installed.

The RSB provides the configuration file rtems/config/rtems-bsp.cfg to support building third-party packages and you need to include this file in your RTEMS version specific configuration file. For example the Curl configuration file rtems/config/curl/curl-7.65.1-1.cfg:

#
# Curl 7.65.1
#

%if %{release} == %{nil}
 %define release 1  <1>
%endif

%include %{_configdir}/rtems-bsp.cfg   <2>

#
# Curl Version
#
%define curl_version 7.65.1   <3>

%hash sha512 curl-%{curl_version}.tar.xz aba2d979a...72b6ac55df4   <4>

#
# Curl Build configuration
#
%include %{_configdir}/curl-1.cfg <5>

Items:

The release number.
Include the RSB RTEMS BSP support.
The Curl package’s version.
The SHA512 hash for the source file. The hash here has been shortened.
The Curl standard build configuration.

The RSB RTEMS BSP support file rtems/config/rtems-bsp.cfg checks to make sure the required RSB command line options are provided. These include --host and --with-rtems-bsp. If the --with-tools command line option is not given the ${_prefix} is used as the path to the tools. If the --with-rtems command line option is not given the ${_prefix} is used as the path to the installed RTEMS BSP.

Note

The RTEMS BSP and any dependent 3rd party packages must be installed to be seen as available. A path to the location the BSP has been built will not work.

The first check is to make sure a target is not specified. This is only used for Canadian cross-compilication builds and currently there is no support for RTEMS third party packages to build that way:

#
# The target is used by compilers or Cxc builds.
#
%if %{_target} != %{nil}
 %error RTEMS BSP builds use --host and not --target
%endif

A host is required using the --host option:

#
# We need a host from the user to specifiy the RTEMS architecture and major
# version.
#
%if %{_host} == %{nil} && %{rtems_bsp_error} <1>
 %error No RTEMS host or BSP specified: --host=<arch>-rtems<ver>
%endif

An RTEMS BSP is required using the --with-bsp option:

#
# We need a BSP from the user.
#
%ifn %{defined with_rtems_bsp}
 %if %{rtems_bsp_error}
  %error No RTEMS BSP specified: --rtems-bsp=arch/bsp (or --with-rtems-bsp=bsp)
 %endif
 %define with_rtems_bsp sparc/erc32
%endif

Check if the --with-tools or --with-rtems options have been provided and if they are not provided use the --prefix path:

#
# If no tools or RTEMS provided use the prefix.
#
%ifn %{defined with_tools}
 %define with_tools %{_prefix}
%endif

%ifn %{defined with_rtems}
 %define with_rtems %{_prefix}
%endif

Add the tools path to the envnironment path:

#
# Set the path to the tools.
#
%{path prepend %{with_tools}/bin}

RTEMS exports the build configuration in pkgconfig (.pc) files. The RSB can read these files even when there is no pkgconfig support installed on your development machine. The pkgconfig support provides a BSP’s configuration and the RSB uses it to set the followng RSB macros variables:

%{pkgconfig prefix %{_prefix}/lib/pkgconfig} <1>
%{pkgconfig crosscompile yes} <2>
%{pkgconfig filter-flags yes} <3>

#
# The RTEMS BSP Flags
#
%define rtems_bsp           %{with_rtems_bsp}
%define rtems_bsp_ccflags   %{pkgconfig ccflags %{_host}-%{rtems_bsp}} <4>
%define rtems_bsp_cflags    %{pkgconfig cflags  %{_host}-%{rtems_bsp}}
%define rtems_bsp_ldflags   %{pkgconfig ldflags %{_host}-%{rtems_bsp}}
%define rtems_bsp_libs      %{pkgconfig libs    %{_host}-%{rtems_bsp}}

Items:

Set the path to the BSP’s pkgconfig file.
Let pkgconfig know this is a cross-compile build.
Filter flags such as warnings. Warning flags are specific to a package and RTEMS exports it’s warnings flags in the BSP configuration settings.
Ask pkgconfig for the various settings we require.

The flags obtained by pkgconfig and given a rtems_bsp prefix are used to set the RTEMS host variables CFLAGS, LDFLAGS and LIBS. When we build a third party library your host computer is the build machine and RTEMS is the host machine therefore we set the host variables:

%define host_cflags  %{rtems_bsp_cflags}
%define host_ldflags %{rtems_bsp_ldflags}
%define host_libs    %{rtems_bsp_libs}

Finally we provide all the paths you may require when configuring a package. Packages by default consider the _prefix the base and install various files under this tree. The package you are building is specific to a BSP and needs to install it’s files into the RTEMS specific BSP path under the _prefix. This allows more than BSP build of this package to be installed under the same _prefix at the same time:

%define rtems_bsp_prefix  %{_prefix}/%{_host}/%{rtems_bsp} <1>
%define _exec_prefix      %{rtems_bsp_prefix}
%define _bindir           %{_exec_prefix}/bin
%define _sbindir          %{_exec_prefix}/sbin
%define _libexecdir       %{_exec_prefix}/libexec
%define _datarootdir      %{_exec_prefix}/share
%define _datadir          %{_datarootdir}
%define _sysconfdir       %{_exec_prefix}/etc
%define _sharedstatedir   %{_exec_prefix}/com
%define _localstatedir    %{_exec_prefix}/var
%define _includedir       %{_libdir}/include
%define _lib              lib
%define _libdir           %{_exec_prefix}/%{_lib}
%define _libexecdir       %{_exec_prefix}/libexec
%define _mandir           %{_datarootdir}/man
%define _infodir          %{_datarootdir}/info
%define _localedir        %{_datarootdir}/locale
%define _localedir        %{_datadir}/locale
%define _localstatedir    %{_exec_prefix}/var

Items:

The path to the installed BSP.

When you configure a package you can reference these paths and the RSB will provide sensible default or in this case map them to the BSP:

../${source_dir_curl}/configure \ <1>
  --host=%{_host} \
  --prefix=%{_prefix} \
  --bindir=%{_bindir} \
  --exec_prefix=%{_exec_prefix} \
  --includedir=%{_includedir} \
  --libdir=%{_libdir} \
  --libexecdir=%{_libexecdir} \
  --mandir=%{_mandir} \
  --infodir=%{_infodir} \
  --datadir=%{_datadir}

Items:

The configure command for Curl.

15.4.6. BSP Configuration¶

The following RSB macros are defined when building a package for RTEMS:

Note

A complete list can be obtained by building with the --trace flag. The log will contain a listing of all macros before and after the configuration is loaded.

%{rtems_bsp}:: The name of the RTEMS BSP.
%{rtems_bsp_cc}:: The C compiler name for the RTEMS BSP.
%{rtems_bsp_cflags}:: The C compiler flags for the RTEMS BSP.
%{rtems_bsp_ccflags}:: The C++ compiler flags for the RTEMS BSP.
%{rtems_bsp_incpath}:: The include path to teh RTEMS BSP header files.
%{rtems_bsp_ldflags}:: The linker flags for the RTEMS BSP.
%{rtems_bsp_libs}:: The libraries used when linking an RTEMS BSP executable.
%{rtems_bsp_prefix}:: The prefix for the RTEMS BSP.
%{rtems-libbsd}:: The variable is set to found if LibBSD is available.
%{rtems-defaultconfig}:: The path of the RSB helper script to locate find header files or libraries.
%{_host}: The host triplet passed on the command line to the set builder using the --host options. This is the RTEMS architecture and version. For example arm-rtems5.
%{host_cflags}:: The BSP CFLAGS returned by pkgconfig.
%{host_cxxflags}:: The BSP CXXFLAGS returned by pkgconfig.
%{host_includes}:: The BSP include paths returned by pkgconfig.
%{host_ldflags}:: The BSP LDFLAGS returned by pkgconfig.
%{host_libs}:: The libraries needed to be linked to create an executable. If LibBSD is installed the library -lbsd is added. If the BSP has installed the RTEMS default configuration library (-lrtemsdefaultconfig) it is added to the list of libraries.
%{host_build_flags}:: This macro is defined in defaults.mc and is a series of shell commands that set up the environment to build an RTEMS package. If the host and the build triplets are the same it is a native build for your development host. If the host is not the build machine it is a cross-complitation build. For either case the following are defined.
%{_host_os}:: The host operating system extracted from the --host command line option. For example the operating sstem for the host of arm-rtems5 is rtems5.
%{_host_arch}:: The host architecture extracted from the --host command line option. For example the architecture for the host of arm-rtems5 is arm.
%{_host_cpu}:: The host cpu extracted from the --host command line option. For example the cpu for the host of arm-rtems5 is arm.