From 72a62ad88f82fe1ffee50024db4dd0f3fa5806f7 Mon Sep 17 00:00:00 2001 From: Chris Johns Date: Thu, 3 Nov 2016 16:58:08 +1100 Subject: Rename all manuals with an _ to have a -. It helps released naming of files. --- bsp-howto/makefiles.rst | 190 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 190 insertions(+) create mode 100644 bsp-howto/makefiles.rst (limited to 'bsp-howto/makefiles.rst') diff --git a/bsp-howto/makefiles.rst b/bsp-howto/makefiles.rst new file mode 100644 index 0000000..b79437b --- /dev/null +++ b/bsp-howto/makefiles.rst @@ -0,0 +1,190 @@ +.. comment SPDX-License-Identifier: CC-BY-SA-4.0 + +.. COMMENT: COPYRIGHT (c) 1988-2002. +.. COMMENT: On-Line Applications Research Corporation (OAR). +.. COMMENT: All rights reserved. + +.. _Makefiles: + +Makefiles +######### + +This chapter discusses the Makefiles associated with a BSP. It does not +describe the process of configuring, building, and installing RTEMS. This +chapter will not provide detailed information about this process. Nonetheless, +it is important to remember that the general process consists of four phases as +shown here: + +- ``bootstrap`` + +- ``configure`` + +- ``build`` + +- ``install`` + +During the bootstrap phase, you are using the ``configure.ac`` and +``Makefile.am`` files as input to GNU autoconf and automake to generate a +variety of files. This is done by running the ``bootstrap`` script found at +the top of the RTEMS source tree. + +During the configure phase, a number of files are generated. These generated +files are tailored for the specific host/target combination by the configure +script. This set of files includes the Makefiles used to actually compile and +install RTEMS. + +During the build phase, the source files are compiled into object files and +libraries are built. + +During the install phase, the libraries, header files, and other support files +are copied to the BSP specific installation point. After installation is +successfully completed, the files generated by the configure and build phases +may be removed. + +Makefiles Used During The BSP Building Process +============================================== + +RTEMS uses the *GNU automake* and *GNU autoconf* automatic configuration +package. Consequently, there are a number of automatically generated files in +each directory in the RTEMS source tree. The ``bootstrap`` script found in the +top level directory of the RTEMS source tree is executed to produce the +automatically generated files. That script must be run from a directory with a +``configure.ac`` file in it. The ``bootstrap`` command is usually invoked in +one of the following manners: + +- ``bootstrap`` to regenerate all files that are generated by autoconf and + automake. + +- ``bootstrap -c`` to remove all files generated by autoconf and automake. + +- ``bootstrap -p`` to regenerate ``preinstall.am`` files. + +There is a file named ``Makefile.am`` in each directory of a BSP. This file is +used by *automake* to produce the file named ``Makefile.in`` which is also +found in each directory of a BSP. When modifying a ``Makefile.am``, you can +probably find examples of anything you need to do in one of the BSPs. + +The configure process specializes the ``Makefile.in`` files at the time that +RTEMS is configured for a specific development host and target. Makefiles are +automatically generated from the ``Makefile.in`` files. It is necessary for +the BSP developer to provide the ``Makefile.am`` files and generate the +``Makefile.in`` files. Most of the time, it is possible to copy the +``Makefile.am`` from another similar directory and edit it. + +The ``Makefile`` files generated are processed when configuring and building +RTEMS for a given BSP. + +The BSP developer is responsible for generating ``Makefile.am`` files which +properly build all the files associated with their BSP. Most BSPs will only +have a single ``Makefile.am`` which details the set of source files to build to +compose the BSP support library along with the set of include files that are to +be installed. + +This single ``Makefile.am`` at the top of the BSP tree specifies the set of +header files to install. This fragment from the SPARC/ERC32 BSP results in +four header files being installed. + +.. code-block:: makefile + + include_HEADERS = include/bsp.h + include_HEADERS += include/tm27.h + include_HEADERS += include/erc32.h + include_HEADERS += include/coverhd.h + +When adding new include files, you will be adding to the set of +``include_HEADERS``. When you finish editing the ``Makefile.am`` file, do not +forget to run ``bootstrap -p`` to regenerate the ``preinstall.am``. + +The ``Makefile.am`` also specifies which source files to build. By convention, +logical components within the BSP each assign their source files to a unique +variable. These variables which define the source files are collected into a +single variable which instructs the GNU autotools that we are building +``libbsp.a``. This fragment from the SPARC/ERC32 BSP shows how the startup +related, miscellaneous support code, and the console device driver source is +managed in the ``Makefile.am``. + +.. code-block:: makefile + + startup_SOURCES = ../../sparc/shared/bspclean.c ../../shared/bsplibc.c \ + ../../shared/bsppredriverhook.c \ + ../../shared/bsppost.c ../../sparc/shared/bspstart.c \ + ../../shared/bootcard.c ../../shared/sbrk.c startup/setvec.c \ + startup/spurious.c startup/erc32mec.c startup/boardinit.S + clock_SOURCES = clock/ckinit.c + ... + noinst_LIBRARIES = libbsp.a + libbsp_a_SOURCES = $(startup_SOURCES) $(console_SOURCES) ... + +When adding new files to an existing directory, do not forget to add the new +files to the list of files to be built in the corresponding ``XXX_SOURCES`` +variable in the ``Makefile.am`` and run``bootstrap``. + +Some BSPs use code that is built in ``libcpu``. If you BSP does this, then you +will need to make sure the objects are pulled into your BSP library. The +following from the SPARC/ERC32 BSP pulls in the cache, register window +management and system call support code from the directory corresponding to its +``RTEMS_CPU`` model. + +.. code-block:: makefile + + libbsp_a_LIBADD = ../../../libcpu/@RTEMS_CPU@/cache.rel \ + ../../../libcpu/@RTEMS_CPU@/reg_win.rel \ + ../../../libcpu/@RTEMS_CPU@/syscall.rel + +.. note: + +The ``Makefile.am`` files are ONLY processed by ``bootstrap`` and the resulting +``Makefile.in`` files are only processed during the configure process of a +RTEMS build. Therefore, when developing a BSP and adding a new file to a +``Makefile.am``, the already generated ``Makefile`` will not automatically +include the new references unless you configured RTEMS with the +``--enable-maintainer-mode`` option. Otherwise, the new file will not being be +taken into account! + +Creating a New BSP Make Customization File +========================================== + +When building a BSP or an application using that BSP, it is necessary to tailor +the compilation arguments to account for compiler flags, use custom linker +scripts, include the RTEMS libraries, etc.. The BSP must be built using this +information. Later, once the BSP is installed with the toolset, this same +information must be used when building the application. So a BSP must include +a build configuration file. The configuration file is ``make/custom/BSP.cfg``. + +The configuration file is taken into account when building one's application +using the RTEMS template Makefiles (``make/templates``). These application +template Makefiles have been included with the RTEMS source distribution since +the early 1990's. However there is a desire in the RTEMS user community to +move all provided examples to GNU autoconf. They are included in the 4.9 +release series and used for all examples provided with RTEMS. There is no +definite time table for obsoleting them. You are free to use these but be +warned they have fallen out of favor with many in the RTEMS community and may +disappear in the future. + +The following is a slightly shortened version of the make customization file +for the gen68340 BSP. The original source for this file can be found in the +``make/custom`` directory. + +.. code-block:: makefile + + # The RTEMS CPU Family and Model + RTEMS_CPU=m68k + RTEMS_CPU_MODEL=m68340 + include $(RTEMS_ROOT)/make/custom/default.cfg + # This is the actual bsp directory used during the build process. + RTEMS_BSP_FAMILY=gen68340 + # This contains the compiler options necessary to select the CPU model + # and (hopefully) optimize for it. + CPU_CFLAGS = -mcpu=cpu32 + # optimize flag: typically -O2 + CFLAGS_OPTIMIZE_V = -O2 -g -fomit-frame-pointer + +The make customization files have generally grown simpler and simpler with each +RTEMS release. Beginning in the 4.9 release series, the rules for linking an +RTEMS application are shared by all BSPs. Only BSPs which need to perform a +transformation from linked ELF file to a downloadable format have any +additional actions for program link time. In 4.8 and older, every BSP specified +the "make executable" or ``make-exe`` rule and duplicated the same actions. + +It is generally easier to copy a ``make/custom`` file from a BSP similar to the +one being developed. -- cgit v1.2.3