docs/overview.txt
author "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
Tue Apr 21 18:08:27 2009 +0000 (2009-04-21)
branch1.4
changeset 1304 94d732462aee
parent 1300 7acdd1de5b50
permissions -rw-r--r--
1.4: small documentation fix.

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File.........: overview.txt
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Content......: Overview of how crosstool-NG works.
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Copyrigth....: (C) 2007 Yann E. MORIN <yann.morin.1998@anciens.enib.fr>
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License......: Creative Commons Attribution Share Alike (CC-by-sa), v2.5
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____________________
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                   /
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Table Of Content  /
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_________________/
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Introduction
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History
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Installing crosstool-NG
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  Install method
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  The hacker's way
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  Preparing for packaging
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  Shell completion
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  Contributed code
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Configuring crosstool-NG
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  Interesting config options
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  Re-building an existing toolchain
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Running crosstool-NG
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  Stopping and restarting a build
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  Testing all toolchains at once
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  Overriding the number of // jobs
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Using the toolchain
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Toolchain types
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Internals
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  Makefile front-end
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  Kconfig parser
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  Architecture-specific
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  Adding a new version of a component
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  Build scripts
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________________
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               /
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Introduction  /
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_____________/
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crosstool-NG aims at building toolchains. Toolchains are an essential component
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in a software development project. It will compile, assemble and link the code
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that is being developed. Some pieces of the toolchain will eventually end up
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in the resulting binary/ies: static libraries are but an example.
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So, a toolchain is a very sensitive piece of software, as any bug in one of the
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components, or a poorly configured component, can lead to execution problems,
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ranging from poor performance, to applications ending unexpectedly, to
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mis-behaving software (which more than often is hard to detect), to hardware
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damage, or even to human risks (which is more than regrettable).
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Toolchains are made of different piece of software, each being quite complex
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and requiring specially crafted options to build and work seamlessly. This
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is usually not that easy, even in the not-so-trivial case of native toolchains.
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The work reaches a higher degree of complexity when it comes to cross-
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compilation, where it can become quite a nightmare...
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Some cross-toolchains exist on the internet, and can be used for general
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development, but they have a number of limitations:
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  - they can be general purpose, in that they are configured for the majority:
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    no optimisation for your specific target,
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  - they can be prepared for a specific target and thus are not easy to use,
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    nor optimised for, or even supporting your target,
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  - they often are using aging components (compiler, C library, etc...) not
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    supporting special features of your shiny new processor;
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On the other side, these toolchain offer some advantages:
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  - they are ready to use and quite easy to install and setup,
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  - they are proven if used by a wide community.
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But once you want to get all the juice out of your specific hardware, you will
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want to build your own toolchain. This is where crosstool-NG comes into play.
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There are also a number of tools that build toolchains for specific needs,
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which are not really scalable. Examples are:
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  - buildroot (buildroot.uclibc.org) whose main purpose is to build root file
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    systems, hence the name. But once you have your toolchain with buildroot,
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    part of it is installed in the root-to-be, so if you want to build a whole
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    new root, you either have to save the existing one as a template and
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    restore it later, or restart again from scratch. This is not convenient,
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  - ptxdist (www.pengutronix.de/software/ptxdist), whose purpose is very
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    similar to buildroot,
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  - other projects (openembedded.org for example), which are again used to
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    build root file systems.
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crosstool-NG is really targeted at building toolchains, and only toolchains.
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It is then up to you to use it the way you want.
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___________
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          /
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History  /
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________/
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crosstool was first 'conceived' by Dan Kegel, who offered it to the community
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as a set of scripts, a repository of patches, and some pre-configured, general
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purpose setup files to be used to configure crosstool. This is available at
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http://www.kegel.com/crosstool, and the subversion repository is hosted on
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google at http://code.google.com/p/crosstool/.
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I once managed to add support for uClibc-based toolchains, but it did not make
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into mainline, mostly because I didn't have time to port the patch forward to
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the new versions, due in part to the big effort it was taking.
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So I decided to clean up crosstool in the state it was, re-order the things
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in place, add appropriate support for what I needed, that is uClibc support
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and a menu-driven configuration, named the new implementation crosstool-NG,
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(standing for crosstool Next Generation, as many other comunity projects do,
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and as a wink at the TV series "Star Trek: The Next Generation" ;-) ) and
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made it available to the community, in case it was of interest to any one.
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___________________________
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                          /
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Installing crosstool-NG  /
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________________________/
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There are two ways you can use crosstool-NG:
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 - build and install it, then get rid of the sources like you'd do for most
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   programs,
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 - or only build it and run from the source directory.
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The former should be used if you got crosstool-NG from a packaged tarball, see
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"Install method", below, while the latter is most useful for developpers that
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checked the code out from SVN, and want to submit patches, see "The Hacker's
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way", below.
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Install method |
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---------------+
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If you go for the install, then you just follow the classical, but yet easy
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./configure way:
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  ./configure --prefix=/some/place
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  make
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  make install
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  export PATH="${PATH}:/some/place/bin"
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You can then get rid of crosstool-NG source. Next create a directory to serve
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as a working place, cd in there and run:
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  ct-ng help
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See below for complete usage.
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The Hacker's way |
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-----------------+
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If you go the hacker's way, then the usage is a bit different, although very
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simple:
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  ./configure --local
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  make
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Now, *do not* remove crosstool-NG sources. They are needed to run crosstool-NG!
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Stay in the directory holding the sources, and run:
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  ./ct-ng help
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See below for complete usage.
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Now, provided you checked-out the code, you can send me your interesting changes
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by running:
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  svn diff
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and mailing me the result! :-P
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Preparing for packaging |
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------------------------+
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If you plan on packaging crosstool-NG, you surely don't want to install it
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in your root file system. The install procedure of crosstool-NG honors the
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DESTDIR variable:
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  ./configure --prefix=/usr
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  make
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  make DESTDIR=/packaging/place install
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Shell completion |
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-----------------+
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crosstool-NG comes with a shell script fragment that defines bash-compatible
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completion. That shell fragment is currently not installed automatically, but
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this is planned.
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To install the shell script fragment, you have two options:
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 - install system-wide, most probably by copying ct-ng.comp into
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   /etc/bash_completion.d/
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 - install for a single user, by copying ct-ng.comp into ${HOME}/ and
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   sourcing this file from your ${HOME}/.bashrc
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Contributed code |
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-----------------+
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Some people contibuted code that couldn't get merged for various reasons. This
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code is available as patches in the contrib/ sub-directory. These patches are
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to be applied to the source of crosstool-NG, prior to installing.
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An easy way to use contributed code is to pass the --with-contrib= option to
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./configure. The possible values depend upon which contributions are packaged
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with your version, but you can get with it with passing one of those two
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special values:
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  --with-contrib=list
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    will list all available contributions
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  --with-contrib=all
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    will select all avalaible contributions
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There is no guarantee that a particuliar contribution applies to the current
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version of crosstool-ng, or that it will work at all. Use contributions at
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your own risk.
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____________________________
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                           /
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Configuring crosstool-NG  /
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_________________________/
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crosstool-NG is configured with a configurator presenting a menu-stuctured set
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of options. These options let you specify the way you want your toolchain
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built, where you want it installed, what architecture and specific processor it
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will support, the version of the components you want to use, etc... The
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value for those options are then stored in a configuration file.
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The configurator works the same way you configure your Linux kernel. It is
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assumed you now how to handle this.
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To enter the menu, type:
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  ct-ng menuconfig
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Almost every config item has a help entry. Read them carefully.
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String and number options can refer to environment variables. In such a case,
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you must use the shell syntax: ${VAR}. You shall neither single- nor double-
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quote the string/number options.
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There are three environment variables that are computed by crosstool-NG, and
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that you can use:
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CT_TARGET:
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  It represents the target tuple you are building for. You can use it for
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  example in the installation/prefix directory, such as:
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    /opt/x-tools/${CT_TARGET}
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CT_TOP_DIR:
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  The top directory where crosstool-NG is running. You shouldn't need it in
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  most cases. There is one case where you may need it: if you have local
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  patches and you store them in your running directory, you can refer to them
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  by using CT_TOP_DIR, such as:
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    ${CT_TOP_DIR}/patches.myproject
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CT_VERSION:
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  The version of crosstool-NG you are using. Not much use for you, but it's
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  there if you need it.
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Interesting config options |
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---------------------------+
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CT_LOCAL_TARBALLS_DIR:
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  If you already have some tarballs in a direcotry, enter it here. That will
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  speed up the retrieving phase, where crosstool-NG would otherwise download
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  those tarballs.
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CT_PREFIX_DIR:
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  This is where the toolchain will be installed in (and for now, where it
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  will run from). Common use is to add the target tuple in the directory
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  path, such as (see above):
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    /opt/x-tools/${CT_TARGET}
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CT_TARGET_VENDOR:
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  An identifier for your toolchain, will take place in the vendor part of the
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  target tuple. It shall *not* contain spaces or dashes. Usually, keep it
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  to a one-word string, or use underscores to separate words if you need.
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  Avoid dots, commas, and special characters.
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CT_TARGET_ALIAS:
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  An alias for the toolchian. It will be used as a prefix to the toolchain
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  tools. For example, you will have ${CT_TARGET_ALIAS}-gcc
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Also, if you think you don't see enough versions, you can try to enable one of
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those:
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CT_OBSOLETE:
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  Show obsolete versions or tools. Most of the time, you don't want to base
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  your toolchain on too old a version (of gcc, for example). But at times, it
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  can come handy to use such an old version for regression tests. Those old
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  versions are hidden behind CT_OBSOLETE. Those versions (or features) are so
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  marked because maintaining support for those in crosstool-NG would be too
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  costly, time-wise, and time is dear.
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CT_EXPERIMENTAL:
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  Show experimental versions or tools. Again, you might not want to base your
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  toolchain on too recent tools (eg. gcc) for production. But if you need a
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  feature present only in a recent version, or a new tool, you can find them
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  hidden behind CT_EXPERIMENTAL. Those versions (or features) did not (yet)
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  receive thorough testing in crosstool-NG, and/or are not mature enough to
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  be blindly trusted.
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Re-building an existing toolchain |
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----------------------------------+
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If you have an existing toolchain, you can re-use the options used to build it
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to create a new toolchain. That needs a very little bit of effort on your side
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but is quite easy. The options to build a toolchain are saved with the
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toolchain, and you can retrieve this configuration by running:
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  ${CT_TARGET}-config
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This will dump the configuration to stdout, so to rebuild a toolchain with this
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configuration, the following is all you need to do:
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  ${CT_TARGET}-config >.config
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  ct-ng oldconfig
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Then, you can review and change the configuration by running:
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  ct-ng menuconfig
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________________________
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                       /
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Running crosstool-NG  /
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_____________________/
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To build the toolchain, simply type:
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  ct-ng build
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This will use the above configuration to retrieve, extract and patch the
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components, build, install and eventually test your newly built toolchain.
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You are then free to add the toolchain /bin directory in your PATH to use
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it at will.
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In any case, you can get some terse help. Just type:
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  ct-ng help
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or:
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  man 1 ct-ng
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Stopping and restarting a build |
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--------------------------------+
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If you want to stop the build after a step you are debugging, you can pass the
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variable STOP to make:
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  ct-ng STOP=some_step
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Conversely, if you want to restart a build at a specific step you are
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debugging, you can pass the RESTART variable to make:
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  ct-ng RESTART=some_step
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Alternatively, you can call make with the name of a step to just do that step:
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  ct-ng libc_headers
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is equivalent to:
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  ct-ng RESTART=libc_headers STOP=libc_headers
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The shortcuts +step_name and step_name+ allow to respectively stop or restart
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at that step. Thus:
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  ct-ng +libc_headers        and:    ct-ng libc_headers+
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are equivalent to:
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  ct-ng STOP=libc_headers    and:    ct-ng RESTART=libc_headers
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To obtain the list of acceptable steps, please call:
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  ct-ng list-steps
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Note that in order to restart a build, you'll have to say 'Y' to the config
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option CT_DEBUG_CT_SAVE_STEPS, and that the previous build effectively went
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that far.
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Building all toolchains at once |
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--------------------------------+
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You can build all samples; simply call:
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  ct-ng build-all
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Overriding the number of // jobs |
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---------------------------------+
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If you want to override the number of jobs to run in // (the -j option to
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make), you can either re-enter the menuconfig, or simply add it on the command
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line, as such:
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  ct-ng build.4
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which tells crosstool-NG to override the number of // jobs to 4.
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You can see the actions that support overriding the number of // jobs in
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the help menu. Those are the ones with [.#] after them (eg. build[.#] or
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build-all[.#], and so on...).
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Note on // jobs |
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----------------+
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The crosstool-NG script 'ct-ng' is a Makefile-script. It does *not* execute
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in parallel (there is not much to gain). When speaking of // jobs, we are
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refering to the number of // jobs when making the *components*. That is, we
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speak of the number of // jobs used to build gcc, glibc, and so on...
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_______________________
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                      /
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Using the toolchain  /
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____________________/
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Using the toolchain is as simple as adding the toolchain's bin directory in
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your PATH, such as:
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  export PATH="${PATH}:/your/toolchain/path/bin"
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and then using the target tuple to tell the build systems to use your
yann@227
   395
toolchain:
yann@335
   396
  ./configure --target=your-target-tuple
yann@294
   397
or
yann@335
   398
  make CC=your-target-tuple-gcc
yann@294
   399
or
yann@335
   400
  make CROSS_COMPILE=your-target-tuple-
yann@294
   401
and so on...
yann@227
   402
yann@476
   403
It is strongly advised not to use the toolchain sys-root directory as an
yann@620
   404
install directory for your programs/packages. If you do so, you will not be
yann@476
   405
able to use your toolchain for another project. It is even strongly advised
yann@476
   406
that your toolchain is chmod-ed to read-only once successfully build, so that
yann@620
   407
you don't go polluting your toolchain with your programs/packages' files.
yann@476
   408
yann@476
   409
Thus, when you build a program/package, install it in a separate directory,
yann@476
   410
eg. /your/root. This directory is the /image/ of what would be in the root file
yann@620
   411
system of your target, and will contain all that your programs/packages have
yann@476
   412
installed.
yann@476
   413
yann@227
   414
When your root directory is ready, it is still missing some important bits: the
yann@227
   415
toolchain's libraries. To populate your root directory with those libs, just
yann@227
   416
run:
yann@335
   417
  your-target-tuple-populate -s /your/root -d /your/root-populated
yann@227
   418
yann@227
   419
This will copy /your/root into /your/root-populated, and put the needed and only
yann@227
   420
the needed libraries there. Thus you don't polute /your/root with any cruft that
yann@227
   421
would no longer be needed should you have to remove stuff. /your/root always
yann@227
   422
contains only those things you install in it.
yann@227
   423
yann@227
   424
You can then use /your/root-populated to build up your file system image, a
yann@227
   425
tarball, or to NFS-mount it from your target, or whatever you need.
yann@227
   426
yann@294
   427
populate accepts the following options:
yann@294
   428
yann@294
   429
 -s [src_dir]
yann@294
   430
    Use 'src_dir' as the 'source', un-populated root directory
yann@294
   431
yann@294
   432
 -d [dst_dir]
yann@294
   433
    Put the 'destination', populated root directory in 'dst_dir'
yann@294
   434
yann@294
   435
 -f
yann@294
   436
    Remove 'dst_dir' if it previously existed
yann@294
   437
yann@294
   438
 -v
yann@294
   439
    Be verbose, and tell what's going on (you can see exactly where libs are
yann@294
   440
    coming from).
yann@294
   441
yann@294
   442
 -h
yann@294
   443
    Print the help
yann@294
   444
yann@40
   445
___________________
yann@40
   446
                  /
yann@40
   447
Toolchain types  /
yann@40
   448
________________/
yann@40
   449
yann@40
   450
There are four kinds of toolchains you could encounter.
yann@40
   451
yann@40
   452
First off, you must understand the following: when it comes to compilers there
yann@40
   453
are up to four machines involved:
yann@40
   454
  1) the machine configuring the toolchain components: the config machine
yann@40
   455
  2) the machine building the toolchain components:    the build machine
yann@40
   456
  3) the machine running the toolchain:                the host machine
yann@203
   457
  4) the machine the toolchain is generating code for: the target machine
yann@40
   458
yann@40
   459
We can most of the time assume that the config machine and the build machine
yann@40
   460
are the same. Most of the time, this will be true. The only time it isn't
yann@40
   461
is if you're using distributed compilation (such as distcc). Let's forget
yann@40
   462
this for the sake of simplicity.
yann@40
   463
yann@40
   464
So we're left with three machines:
yann@40
   465
 - build
yann@40
   466
 - host
yann@40
   467
 - target
yann@40
   468
yann@40
   469
Any toolchain will involve those three machines. You can be as pretty sure of
yann@40
   470
this as "2 and 2 are 4". Here is how they come into play:
yann@40
   471
yann@40
   472
1) build == host == target
yann@40
   473
    This is a plain native toolchain, targetting the exact same machine as the
yann@40
   474
    one it is built on, and running again on this exact same machine. You have
yann@40
   475
    to build such a toolchain when you want to use an updated component, such
yann@40
   476
    as a newer gcc for example.
yann@197
   477
    crosstool-NG calls it "native".
yann@40
   478
yann@40
   479
2) build == host != target
yann@40
   480
    This is a classic cross-toolchain, which is expected to be run on the same
yann@40
   481
    machine it is compiled on, and generate code to run on a second machine,
yann@40
   482
    the target.
yann@197
   483
    crosstool-NG calls it "cross".
yann@40
   484
yann@40
   485
3) build != host == target
yann@40
   486
    Such a toolchain is also a native toolchain, as it targets the same machine
yann@40
   487
    as it runs on. But it is build on another machine. You want such a
yann@40
   488
    toolchain when porting to a new architecture, or if the build machine is
yann@40
   489
    much faster than the host machine.
yann@197
   490
    crosstool-NG calls it "cross-native".
yann@40
   491
yann@40
   492
4) build != host != target
yann@92
   493
    This one is called a canadian-toolchain (*), and is tricky. The three
yann@40
   494
    machines in play are different. You might want such a toolchain if you
yann@40
   495
    have a fast build machine, but the users will use it on another machine,
yann@40
   496
    and will produce code to run on a third machine.
yann@197
   497
    crosstool-NG calls it "canadian".
yann@40
   498
yann@197
   499
crosstool-NG can build all these kinds of toolchains (or is aiming at it,
yann@197
   500
anyway!)
yann@40
   501
yann@40
   502
(*) The term Canadian Cross came about because at the time that these issues
yann@40
   503
    were all being hashed out, Canada had three national political parties.
yann@40
   504
    http://en.wikipedia.org/wiki/Cross_compiler
yann@40
   505
yann@1
   506
_____________
yann@1
   507
            /
yann@1
   508
Internals  /
yann@1
   509
__________/
yann@1
   510
yann@92
   511
Internally, crosstool-NG is script-based. To ease usage, the frontend is
yann@92
   512
Makefile-based.
yann@92
   513
yann@92
   514
Makefile front-end |
yann@476
   515
-------------------+
yann@92
   516
yann@203
   517
The entry point to crosstool-NG is the Makefile script "ct-ng". Calling this
yann@203
   518
script with an action will act exactly as if the Makefile was in the current
yann@203
   519
working directory and make was called with the action as rule. Thus:
yann@203
   520
  ct-ng menuconfig
yann@294
   521
yann@203
   522
is equivalent to having the Makefile in CWD, and calling:
yann@203
   523
  make menuconfig
yann@203
   524
yann@203
   525
Having ct-ng as it is avoids copying the Makefile everywhere, and acts as a
yann@203
   526
traditional command.
yann@203
   527
yann@203
   528
ct-ng loads sub- Makefiles from the library directory $(CT_LIB_DIR), as set up
yann@203
   529
at configuration time with ./configure.
yann@203
   530
yann@437
   531
ct-ng also searches for config files, sub-tools, samples, scripts and patches in
yann@203
   532
that library directory.
yann@92
   533
yann@294
   534
Because of a stupid make behavior/bug I was unable to track down, implicit make
yann@294
   535
rules are disabled: installing with --local would triger those rules, and mconf
yann@294
   536
was unbuildable.
yann@294
   537
yann@182
   538
Kconfig parser |
yann@476
   539
---------------+
yann@92
   540
yann@965
   541
The kconfig language is a hacked version, vampirised from the Linux kernel
yann@965
   542
(http://www.kernel.org/), and (heavily) adapted to my needs.
yann@92
   543
yann@1040
   544
The list of the most notable changes (at least the ones I remember) follows:
yann@1040
   545
- the CONFIG_ prefix has been replaced with CT_
yann@1040
   546
- a leading | in prompts is skipped, and subsequent leading spaces are not
yann@1040
   547
  trimmed
yann@1040
   548
- otherwise leading spaces are silently trimmed
yann@1040
   549
yann@203
   550
The kconfig parsers (conf and mconf) are not installed pre-built, but as
yann@203
   551
source files. Thus you can have the directory where crosstool-NG is installed,
yann@203
   552
exported (via NFS or whatever) and have clients with different architectures
yann@203
   553
use the same crosstool-NG installation, and most notably, the same set of
yann@203
   554
patches.
yann@203
   555
yann@381
   556
Architecture-specific |
yann@476
   557
----------------------+
yann@381
   558
yann@628
   559
Note: this chapter is not really well written, and might thus be a little bit
yann@628
   560
complex to understand. To get a better grasp of what an architecture is, the
yann@628
   561
reader is kindly encouraged to look at the "arch/" sub-directory, and to the
yann@628
   562
existing architectures to see how things are laid out.
yann@628
   563
yann@381
   564
An architecture is defined by:
yann@381
   565
yann@381
   566
 - a human-readable name, in lower case letters, with numbers as appropriate.
yann@628
   567
   The underscore is allowed; space and special characters are not.
yann@628
   568
     Eg.: arm, x86_64
yann@903
   569
 - a file in "config/arch/", named after the architecture's name, and suffixed
yann@903
   570
   with ".in".
yann@903
   571
     Eg.: config/arch/arm.in
yann@903
   572
 - a file in "scripts/build/arch/", named after the architecture's name, and
yann@903
   573
   suffixed with ".sh".
yann@903
   574
     Eg.: scripts/build/arch/arm.sh
yann@628
   575
yann@903
   576
The architecture's ".in" file API:
yann@628
   577
 > the config option "ARCH_%arch%" (where %arch% is to be replaced with the
yann@628
   578
   actual architecture name).
yann@628
   579
   That config option must have *neither* a type, *nor* a prompt! Also, it can
yann@628
   580
   *not* depend on any other config option (EXPERIMENTAL is managed as above).
yann@628
   581
     Eg.:
yann@628
   582
       config ARCH_arm
yann@630
   583
   + mandatory:
yann@702
   584
       defines a (terse) help entry for this architecture:
yann@630
   585
       Eg.:
yann@630
   586
         config ARCH_arm
yann@630
   587
           help
yann@630
   588
             The ARM architecture.
yann@628
   589
   + optional:
yann@628
   590
       selects adequate associated config options.
yann@1038
   591
       Note: 64-bit architectures *shall* select ARCH_64
yann@628
   592
       Eg.:
yann@628
   593
         config ARCH_arm
yann@628
   594
           select ARCH_SUPPORTS_BOTH_ENDIAN
yann@628
   595
           select ARCH_DEFAULT_LE
yann@630
   596
           help
yann@630
   597
             The ARM architecture.
yann@1038
   598
       Eg.:
yann@1038
   599
         config ARCH_x86_64
yann@1038
   600
            select ARCH_64
yann@1038
   601
            help
yann@1038
   602
              The x86_64 architecture.
yann@628
   603
yann@628
   604
 > other target-specific options, at your discretion. Note however that to
yann@628
   605
   avoid name-clashing, such options shall be prefixed with "ARCH_%arch%",
yann@628
   606
   where %arch% is again replaced by the actual architecture name.
yann@628
   607
   (Note: due to historical reasons, and lack of time to clean up the code,
yann@628
   608
    I may have left some config options that do not completely conform to
yann@628
   609
    this, as the architecture name was written all upper case. However, the
yann@628
   610
    prefix is unique among architectures, and does not cause harm).
yann@381
   611
yann@903
   612
The architecture's ".sh" file API:
yann@965
   613
 > the function "CT_DoArchTupleValues"
yann@381
   614
   + parameters: none
yann@381
   615
   + environment:
yann@901
   616
     - all variables from the ".config" file,
yann@901
   617
     - the two variables "target_endian_eb" and "target_endian_el" which are
yann@901
   618
       the endianness suffixes
yann@381
   619
   + return value: 0 upon success, !0 upon failure
yann@381
   620
   + provides:
yann@391
   621
     - mandatory
yann@383
   622
     - the environment variable CT_TARGET_ARCH
yann@389
   623
     - contains:
yann@389
   624
       the architecture part of the target tuple.
yann@389
   625
       Eg.: "armeb" for big endian ARM
yann@389
   626
            "i386" for an i386
yann@389
   627
   + provides:
yann@391
   628
     - optional
yann@389
   629
     - the environment variable CT_TARGET_SYS
yann@456
   630
     - contains:
yann@383
   631
       the sytem part of the target tuple.
yann@383
   632
       Eg.: "gnu" for glibc on most architectures
yann@383
   633
            "gnueabi" for glibc on an ARM EABI
yann@383
   634
     - defaults to:
yann@383
   635
       - for glibc-based toolchain: "gnu"
yann@383
   636
       - for uClibc-based toolchain: "uclibc"
yann@383
   637
   + provides:
yann@383
   638
     - optional
yann@391
   639
     - the environment variable CT_KERNEL_ARCH
yann@383
   640
     - contains:
yann@391
   641
       the architecture name as understandable by the Linux kernel build
yann@391
   642
       system.
yann@391
   643
       Eg.: "arm" for an ARM
yann@391
   644
            "powerpc" for a PowerPC
yann@391
   645
            "i386" for an x86
yann@383
   646
     - defaults to:
yann@391
   647
       ${CT_ARCH}
yann@391
   648
   + provides:
yann@391
   649
     - optional
yann@767
   650
     - the environment variables to configure the cross-gcc (defaults)
yann@767
   651
       - CT_ARCH_WITH_ARCH    : the gcc ./configure switch to select architecture level         ( "--with-arch=${CT_ARCH_ARCH}"   )
yann@767
   652
       - CT_ARCH_WITH_ABI     : the gcc ./configure switch to select ABI level                  ( "--with-abi=${CT_ARCH_ABI}"     )
yann@767
   653
       - CT_ARCH_WITH_CPU     : the gcc ./configure switch to select CPU instruction set        ( "--with-cpu=${CT_ARCH_CPU}"     )
yann@767
   654
       - CT_ARCH_WITH_TUNE    : the gcc ./configure switch to select scheduling                 ( "--with-tune=${CT_ARCH_TUNE}"   )
yann@767
   655
       - CT_ARCH_WITH_FPU     : the gcc ./configure switch to select FPU type                   ( "--with-fpu=${CT_ARCH_FPU}"     )
yann@767
   656
       - CT_ARCH_WITH_FLOAT   : the gcc ./configure switch to select floating point arithmetics ( "--with-float=soft" or /empty/  )
yann@391
   657
   + provides:
yann@391
   658
     - optional
yann@767
   659
     - the environment variables to pass to the cross-gcc to build target binaries (defaults)
yann@391
   660
       - CT_ARCH_ARCH_CFLAG   : the gcc switch to select architecture level                     ( "-march=${CT_ARCH_ARCH}"            )
yann@456
   661
       - CT_ARCH_ABI_CFLAG    : the gcc switch to select ABI level                              ( "-mabi=${CT_ARCH_ABI}"              )
yann@391
   662
       - CT_ARCH_CPU_CFLAG    : the gcc switch to select CPU instruction set                    ( "-mcpu=${CT_ARCH_CPU}"              )
yann@391
   663
       - CT_ARCH_TUNE_CFLAG   : the gcc switch to select scheduling                             ( "-mtune=${CT_ARCH_TUNE}"            )
yann@391
   664
       - CT_ARCH_FPU_CFLAG    : the gcc switch to select FPU type                               ( "-mfpu=${CT_ARCH_FPU}"              )
yann@391
   665
       - CT_ARCH_FLOAT_CFLAG  : the gcc switch to choose floating point arithmetics             ( "-msoft-float" or /empty/           )
yann@391
   666
       - CT_ARCH_ENDIAN_CFLAG : the gcc switch to choose big or little endian                   ( "-mbig-endian" or "-mlittle-endian" )
yann@391
   667
     - default to:
yann@391
   668
       see above.
yann@767
   669
   + provides:
yann@767
   670
     - optional
yann@767
   671
     - the environement variables to configure the core and final compiler, specific to this architecture:
yann@767
   672
       - CT_ARCH_CC_CORE_EXTRA_CONFIG   : additional, architecture specific core gcc ./configure flags
yann@767
   673
       - CT_ARCH_CC_EXTRA_CONFIG        : additional, architecture specific final gcc ./configure flags
yann@767
   674
     - default to:
yann@767
   675
       - all empty
yann@767
   676
   + provides:
yann@767
   677
     - optional
yann@767
   678
     - the architecture-specific CFLAGS and LDFLAGS:
yann@767
   679
       - CT_ARCH_TARGET_CLFAGS
yann@767
   680
       - CT_ARCH_TARGET_LDFLAGS
yann@767
   681
     - default to:
yann@767
   682
       - all empty
yann@628
   683
yann@903
   684
You can have a look at "config/arch/arm.in" and "scripts/build/arch/arm.sh" for
yann@903
   685
a quite complete example of what an actual architecture description looks like.
yann@901
   686
yann@890
   687
Kernel specific |
yann@890
   688
----------------+
yann@890
   689
yann@890
   690
A kernel is defined by:
yann@890
   691
yann@890
   692
 - a human-readable name, in lower case letters, with numbers as appropriate.
yann@890
   693
   The underscore is allowed; space and special characters are not (although
yann@890
   694
   they are internally replaced with underscores.
yann@890
   695
     Eg.: linux, bare-metal
yann@890
   696
 - a file in "config/kernel/", named after the kernel name, and suffixed with
yann@890
   697
   ".in".
yann@890
   698
     Eg.: config/kernel/linux.in, config/kernel/bare-metal.in
yann@901
   699
 - a file in "scripts/build/kernel/", named after the kernel name, and suffixed
yann@901
   700
   with ".sh".
yann@901
   701
     Eg.: scripts/build/kernel/linux.sh, scripts/build/kernel/bare-metal.sh
yann@890
   702
yann@890
   703
The kernel's ".in" file must contain:
yann@890
   704
 > an optional lines containing exactly "# EXPERIMENTAL", starting on the
yann@890
   705
   first column, and without any following space or other character.
yann@890
   706
   If this line is present, then this kernel is considered EXPERIMENTAL,
yann@890
   707
   and correct dependency on EXPERIMENTAL will be set.
yann@901
   708
yann@890
   709
 > the config option "KERNEL_%kernel_name%" (where %kernel_name% is to be
yann@890
   710
   replaced with the actual kernel name, with all special characters and
yann@890
   711
   spaces replaced by underscores).
yann@890
   712
   That config option must have *neither* a type, *nor* a prompt! Also, it can
yann@890
   713
   *not* depends on EXPERIMENTAL.
yann@890
   714
     Eg.: KERNEL_linux, KERNEL_bare_metal
yann@890
   715
   + mandatory:
yann@890
   716
       defines a (terse) help entry for this kernel.
yann@890
   717
       Eg.:
yann@890
   718
         config KERNEL_bare_metal
yann@890
   719
           help
yann@890
   720
             Build a compiler for use without any kernel.
yann@890
   721
   + optional:
yann@890
   722
       selects adequate associated config options.
yann@890
   723
       Eg.:
yann@890
   724
         config KERNEL_bare_metal
yann@890
   725
           select BARE_METAL
yann@890
   726
           help
yann@890
   727
             Build a compiler for use without any kernel.
yann@890
   728
yann@890
   729
 > other kernel specific options, at your discretion. Note however that, to
yann@890
   730
   avoid name-clashing, such options should be prefixed with
yann@890
   731
   "KERNEL_%kernel_name%", where %kernel_name% is again tp be replaced with
yann@890
   732
   the actual kernel name.
yann@890
   733
   (Note: due to historical reasons, and lack of time to clean up the code,
yann@890
   734
    I may have left some config options that do not completely conform to
yann@890
   735
    this, as the kernel name was written all upper case. However, the prefix
yann@890
   736
    is unique among kernels, and does not cause harm).
yann@890
   737
yann@901
   738
The kernel's ".sh" file API:
yann@901
   739
 > is a bash script fragment
yann@901
   740
yann@965
   741
 > defines the function CT_DoKernelTupleValues
yann@965
   742
   + see the architecture's CT_DoArchTupleValues, except for:
yann@965
   743
   + set the environment variable CT_TARGET_KERNEL, the kernel part of the
yann@965
   744
     target tuple
yann@965
   745
   + return value: ignored
yann@965
   746
yann@901
   747
 > defines the function "do_kernel_get":
yann@901
   748
   + parameters: none
yann@901
   749
   + environment:
yann@901
   750
      - all variables from the ".config" file.
yann@901
   751
   + return value: 0 for success, !0 for failure.
yann@901
   752
   + behavior: download the kernel's sources, and store the tarball into
yann@901
   753
     "${CT_TARBALLS_DIR}". To this end, a functions is available, that
yann@901
   754
     abstracts downloading tarballs:
yann@901
   755
     - CT_DoGet <tarball_base_name> <URL1 [URL...]>
yann@901
   756
       Eg.: CT_DoGet linux-2.6.26.5 ftp://ftp.kernel.org/pub/linux/kernel/v2.6
yann@901
   757
     Note: retrieving sources from svn, cvs, git and the likes is not supported
yann@901
   758
     by CT_DoGet. You'll have to do this by hand, as it is done for eglibc in
yann@901
   759
     "scripts/build/libc/eglibc.sh"
yann@901
   760
yann@901
   761
 > defines the function "do_kernel_extract":
yann@901
   762
   + parameters: none
yann@901
   763
   + environment:
yann@901
   764
      - all variables from the ".config" file,
yann@901
   765
   + return value: 0 for success, !0 for failure.
yann@901
   766
   + behavior: extract the kernel's tarball into "${CT_SRC_DIR}", and apply
yann@901
   767
     required patches. To this end, a function is available, that abstracts
yann@901
   768
     extracting tarballs:
yann@901
   769
     - CT_ExtractAndPatch <tarball_base_name>
yann@901
   770
       Eg.: CT_ExtractAndPatch linux-2.6.26.5
yann@901
   771
yann@901
   772
 > defines the function "do_kernel_headers":
yann@901
   773
   + parameters: none
yann@901
   774
   + environment:
yann@901
   775
      - all variables from the ".config" file,
yann@901
   776
   + return value: 0 for success, !0 for failure.
yann@901
   777
   + behavior: install the kernel headers (if any) in "${CT_SYSROOT_DIR}/usr/include"
yann@901
   778
yann@901
   779
 > defines any kernel-specific helper functions
yann@901
   780
   These functions, if any, must be prefixed with "do_kernel_%CT_KERNEL%_",
yann@901
   781
   where '%CT_KERNEL%' is to be replaced with the actual kernel name, to avoid
yann@901
   782
   any name-clashing.
yann@901
   783
yann@901
   784
You can have a look at "config/kernel/linux.in" and "scripts/build/kernel/linux.sh"
yann@903
   785
as an example of what a complex kernel description looks like.
yann@901
   786
yann@620
   787
Adding a new version of a component |
yann@476
   788
------------------------------------+
yann@476
   789
yann@476
   790
When a new component, such as the Linux kernel, gcc or any other is released,
yann@476
   791
adding the new version to crosstool-NG is quite easy. There is a script that
yann@476
   792
will do all that for you:
yann@1095
   793
  scripts/addToolVersion.sh
yann@476
   794
yann@476
   795
Run it with no option to get some help.
yann@381
   796
yann@203
   797
Build scripts |
yann@476
   798
--------------+
yann@203
   799
yann@203
   800
To Be Written later...