1 File.........: overview.txt
2 Content......: Overview of how crosstool-NG works.
3 Copyrigth....: (C) 2007 Yann E. MORIN <yann.morin.1998@anciens.enib.fr>
4 License......: Creative Commons Attribution Share Alike (CC-by-sa), v2.5
11 crosstool-NG aims at building toolchains. Toolchains are an essential component
12 in a software development project. It will compile, assemble and link the code
13 that is being developed. Some pieces of the toolchain will eventually end up
14 in the resulting binary/ies: static libraries are but an example.
16 So, a toolchain is a very sensitive piece of software, as any bug in one of the
17 components, or a poorly configured component, can lead to execution problems,
18 ranging from poor performance, to applications ending unexpectedly, to
19 mis-behaving software (which more than often is hard to detect), to hardware
20 damage, or even to human risks (which is more than regrettable).
22 Toolchains are made of different piece of software, each being quite complex
23 and requiring specially crafted options to build and work seamlessly. This
24 is usually not that easy, even in the not-so-trivial case of native toolchains.
25 The work reaches a higher degree of complexity when it comes to cross-
26 compilation, where it can become quite a nightmare...
28 Some cross-toolchains exist on the internet, and can be used for general
29 development, but they have a number of limitations:
30 - they can be general purpose, in that they are configured for the majority:
31 no optimisation for your specific target,
32 - they can be prepared for a specific target and thus are not easy to use,
33 nor optimised for, or even supporting your target,
34 - they often are using aging components (compiler, C library, etc...) not
35 supporting special features of your shiny new processor;
36 On the other side, these toolchain offer some advantages:
37 - they are ready to use and quite easy to install and setup,
38 - they are proven if used by a wide community.
40 But once you want to get all the juice out of your specific hardware, you will
41 want to build your own toolchain. This is where crosstool-NG comes into play.
43 There are also a number of tools that build toolchains for specific needs,
44 which are not really scalable. Examples are:
45 - buildroot (buildroot.uclibc.org) whose main purpose is to build root file
46 systems, hence the name. But once you have your toolchain with buildroot,
47 part of it is installed in the root-to-be, so if you want to build a whole
48 new root, you either have to save the existing one as a template and
49 restore it later, or restart again from scratch. This is not convenient,
50 - ptxdist (www.pengutronix.de/software/ptxdist), whose purpose is very
52 - other projects (openembedded.org for example), which is again used to
53 build root file systems.
55 crosstool-NG is really targeted at building toolchains, and only toolchains.
56 It is then up to you to use it the way you want.
63 crosstool was first 'conceived' by Dan Kegel, who offered it to the community
64 as a set of scripts, a repository of patches, and some pre-configured, general
65 purpose setup files to be used to configure crosstool. This is available at
66 http://www.kegel.com/crosstool, and the subversion repository is hosted on
67 google at http://code.google.com/p/crosstool/.
69 I once managed to add support for uClibc-based toolchains, but it did not make
70 into mainline, mostly because I didn't have time to port the patch forward to
71 the new versions, due in part to the big effort it was taking.
73 So I decided to clean up crosstool in the state it was, re-order the things
74 in place, add appropriate support for what I needed, that is uClibc support
75 and a menu-driven configuration, named the new implementation crosstool-NG,
76 (standing for crosstool Next Generation, as many other comunity projects do,
77 and as a wink at the TV series "Star Trek: The Next Generation" ;-) ) and
78 made it available to the community, in case it was of interest to any one.
80 ___________________________
82 Installing crosstool-NG /
83 ________________________/
85 There are two ways you can use crosstool-NG:
86 - build and install it, then get rid of the sources like you'd do for most
88 - or only build it and run from the source directory.
90 The former should be used if you got crosstool-NG from a packaged tarball, see
91 "Install method", below, while the latter is most useful for developpers that
92 checked the code out from SVN, and want to submit patches, see "The Hacker's
98 If you go for the install, then you just follow the classical, but yet easy
100 ./configure --prefix=/some/place
103 export PATH="${PATH}:/some/place/bin"
105 You can then get rid of crosstool-NG source. Next create a directory to serve
106 as a working place, cd in there and run:
109 See below for complete usage.
114 If you go the hacker's way, then the usage is a bit different, although very
119 Now, *do not* remove crosstool-NG sources. They are needed to run crosstool-NG!
120 Stay in the directory holding the sources, and run:
123 See below for complete usage.
125 Now, provided you checked-out the code, you can send me your interesting changes
129 and mailing me the result! :-P
134 Some people contibuted code that couldn't get merged for various reasons. This
135 code is available as patches in the contrib/ sub-directory. These patches are
136 to be applied to the source of crosstool-NG, prior to installing.
138 ____________________________
140 Configuring crosstool-NG /
141 _________________________/
143 crosstool-NG is configured by a configurator presenting a menu-stuctured set of
144 options. These options let you specify the way you want your toolchain built,
145 where you want it installed, what architecture and specific processor it
146 will support, the version of the components you want to use, etc... The
147 value for those options are then stored in a configuration file.
149 The configurator works the same way you configure your Linux kernel. It is
150 assumed you now how to handle this.
152 To enter the menu, type:
155 Almost every config item has a help entry. Read them carefully.
157 String and number options can refer to environment variables. In such a case,
158 you must use the shell syntax: ${VAR}. You shall neither single- nor double-
159 quote the string/number options.
161 There are three environment variables that are computed by crosstool-NG, and
165 It represents the target tuple you are building for. You can use it for
166 example in the installation/prefix directory, such as:
167 /opt/x-tools/${CT_TARGET}
170 The top directory where crosstool-NG is running. You shouldn't need it in
171 most cases. There is one case where you may need it: if you have local
172 patches and you store them in your running directory, you can refer to them
173 by using CT_TOP_DIR, such as:
174 ${CT_TOP_DIR}/patches.myproject
177 The version of crosstool-NG you are using. Not much use for you, but it's
178 there if you need it.
180 Interesting config options |
181 ---------------------------+
183 CT_LOCAL_TARBALLS_DIR:
184 If you already have some tarballs in a direcotry, enter it here. That will
185 speed up the retrieving phase, where crosstool-NG would otherwise download
189 This is where the toolchain will be installed in (and for now, where it
190 will run from). Common use is to add the target tuple in the directory
191 path, such as (see above):
192 /opt/x-tools/${CT_TARGET}
195 An identifier for your toolchain, will take place in the vendor part of the
196 target tuple. It shall *not* contain spaces or dashes. Usually, keep it
197 to a one-word string, or use underscores to separate words if you need.
198 Avoid dots, commas, and special characters.
201 An alias for the toolchian. It will be used as a prefix to the toolchain
202 tools. For example, you will have ${CT_TARGET_ALIAS}-gcc
204 Also, if you think you don't see enough versions, you can try to enable one of
208 Show obsolete versions or tools. Most of the time, you don't want to base
209 your toolchain on too old a version (of gcc, for example). But at times, it
210 can come handy to use such an old version for regression tests. Those old
211 versions are hidden behind CT_OBSOLETE.
214 Show experimental versions or tools. Again, you might not want to base your
215 toolchain on too recent tools (eg. gcc) for production. But if you need a
216 feature present only in a recent version, or a new tool, you can find them
217 hidden behind CT_EXPERIMENTAL.
220 Show broken versions or tools. Some usefull tools are currently broken: they
221 won't compile, run, or worse, cause defects when running. But if you are
222 brave enough, you can try and debug them. They are hidden behind CT_BROKEN,
223 which itself is hidden behind CT_EXPERIMENTAL.
225 Re-building an existing toolchain |
226 ----------------------------------+
228 If you have an existing toolchain, you can re-use the options used to build it
229 to create a new toolchain. That needs a very little bit of effort on your side
230 but is quite easy. The options to build a toolchain are saved in the build log
231 file that is saved within the toolchain. crosstool-NG can extract those options
232 to recreate a new configuration:
233 ct-ng extractconfig </path/to/your/build.log
235 will extract those options, prompt you for the new ones, which you can later
236 edit with menuconfig.
238 Of course, if your build log was compressed, you'd have to use something like:
239 bzcat /path/to/your/build.log.bz2 |ct-ng extractconfig
241 ________________________
243 Running crosstool-NG /
244 _____________________/
246 To build the toolchain, simply type:
249 This will use the above configuration to retrieve, extract and patch the
250 components, build, install and eventually test your newly built toolchain.
252 You are then free to add the toolchain /bin directory in your PATH to use
255 In any case, you can get some terse help. Just type:
260 Stopping and restarting a build |
261 --------------------------------+
263 If you want to stop the build after a step you are debugging, you can pass the
264 variable STOP to make:
267 Conversely, if you want to restart a build at a specific step you are
268 debugging, you can pass the RESTART variable to make:
269 ct-ng RESTART=some_step
271 Alternatively, you can call make with the name of a step to just do that step:
274 ct-ng RESTART=libs_headers STOP=libc_headers
276 The shortcuts +step_name and step_name+ allow to respectively stop or restart
278 ct-ng +libc_headers and: ct-ng libc_headers+
280 ct-ng STOP=libc_headers and: ct-ng RESTART=libc_headers
282 To obtain the list of acceptable steps, please call:
285 Note that in order to restart a build, you'll have to say 'Y' to the config
286 option CT_DEBUG_CT_SAVE_STEPS, and that the previous build effectively went
289 Testing all toolchains at once |
290 -------------------------------+
292 You can test-build all samples; simply call:
295 Overriding the number of // jobs |
296 ---------------------------------+
298 If you want to override the number of jobs to run in // (the -j option to
299 make), you can either re-enter the menuconfig, or simply add it on the command
303 which tells crosstool-NG to override the number of // jobs to 4.
305 You can see the actions that support overriding the number of // jobs in
306 the help menu. Those are the ones with [.#] after them (eg. build[.#] or
307 regtest[.#], and so on...).
309 _______________________
311 Using the toolchain /
312 ____________________/
314 Using the toolchain is as simple as adding the toolchain's bin directory in
316 export PATH="${PATH}:/your/toolchain/path/bin"
318 and then using the target tuple to tell the build systems to use your
320 ./configure --target=your-target-tuple
322 make CC=your-target-tuple-gcc
324 make CROSS_COMPILE=your-target-tuple-
327 It is strongly advised not to use the toolchain sys-root directory as an
328 install directory for your programms/packages. If you do so, you will not be
329 able to use your toolchain for another project. It is even strongly advised
330 that your toolchain is chmod-ed to read-only once successfully build, so that
331 you don't go polluting your toolchain with your programms/packages' files.
333 Thus, when you build a program/package, install it in a separate directory,
334 eg. /your/root. This directory is the /image/ of what would be in the root file
335 system of your target, and will contain all that your programms/packages have
338 When your root directory is ready, it is still missing some important bits: the
339 toolchain's libraries. To populate your root directory with those libs, just
341 your-target-tuple-populate -s /your/root -d /your/root-populated
343 This will copy /your/root into /your/root-populated, and put the needed and only
344 the needed libraries there. Thus you don't polute /your/root with any cruft that
345 would no longer be needed should you have to remove stuff. /your/root always
346 contains only those things you install in it.
348 You can then use /your/root-populated to build up your file system image, a
349 tarball, or to NFS-mount it from your target, or whatever you need.
351 populate accepts the following options:
354 Use 'src_dir' as the 'source', un-populated root directory
357 Put the 'destination', populated root directory in 'dst_dir'
360 Remove 'dst_dir' if it previously existed
363 Be verbose, and tell what's going on (you can see exactly where libs are
374 There are four kinds of toolchains you could encounter.
376 First off, you must understand the following: when it comes to compilers there
377 are up to four machines involved:
378 1) the machine configuring the toolchain components: the config machine
379 2) the machine building the toolchain components: the build machine
380 3) the machine running the toolchain: the host machine
381 4) the machine the toolchain is generating code for: the target machine
383 We can most of the time assume that the config machine and the build machine
384 are the same. Most of the time, this will be true. The only time it isn't
385 is if you're using distributed compilation (such as distcc). Let's forget
386 this for the sake of simplicity.
388 So we're left with three machines:
393 Any toolchain will involve those three machines. You can be as pretty sure of
394 this as "2 and 2 are 4". Here is how they come into play:
396 1) build == host == target
397 This is a plain native toolchain, targetting the exact same machine as the
398 one it is built on, and running again on this exact same machine. You have
399 to build such a toolchain when you want to use an updated component, such
400 as a newer gcc for example.
401 crosstool-NG calls it "native".
403 2) build == host != target
404 This is a classic cross-toolchain, which is expected to be run on the same
405 machine it is compiled on, and generate code to run on a second machine,
407 crosstool-NG calls it "cross".
409 3) build != host == target
410 Such a toolchain is also a native toolchain, as it targets the same machine
411 as it runs on. But it is build on another machine. You want such a
412 toolchain when porting to a new architecture, or if the build machine is
413 much faster than the host machine.
414 crosstool-NG calls it "cross-native".
416 4) build != host != target
417 This one is called a canadian-toolchain (*), and is tricky. The three
418 machines in play are different. You might want such a toolchain if you
419 have a fast build machine, but the users will use it on another machine,
420 and will produce code to run on a third machine.
421 crosstool-NG calls it "canadian".
423 crosstool-NG can build all these kinds of toolchains (or is aiming at it,
426 (*) The term Canadian Cross came about because at the time that these issues
427 were all being hashed out, Canada had three national political parties.
428 http://en.wikipedia.org/wiki/Cross_compiler
435 Internally, crosstool-NG is script-based. To ease usage, the frontend is
441 The entry point to crosstool-NG is the Makefile script "ct-ng". Calling this
442 script with an action will act exactly as if the Makefile was in the current
443 working directory and make was called with the action as rule. Thus:
446 is equivalent to having the Makefile in CWD, and calling:
449 Having ct-ng as it is avoids copying the Makefile everywhere, and acts as a
452 ct-ng loads sub- Makefiles from the library directory $(CT_LIB_DIR), as set up
453 at configuration time with ./configure.
455 ct-ng also searches for config files, sub-tools, samples, scripts and patches in
456 that library directory.
458 Because of a stupid make behavior/bug I was unable to track down, implicit make
459 rules are disabled: installing with --local would triger those rules, and mconf
465 The kconfig language is a hacked version, vampirised from the toybox project
466 by Rob LANDLEY (http://www.landley.net/code/toybox/), itself coming from the
467 Linux kernel (http://www.kernel.org/), and (heavily) adapted to my needs.
469 The kconfig parsers (conf and mconf) are not installed pre-built, but as
470 source files. Thus you can have the directory where crosstool-NG is installed,
471 exported (via NFS or whatever) and have clients with different architectures
472 use the same crosstool-NG installation, and most notably, the same set of
475 Architecture-specific |
476 ----------------------+
478 An architecture is defined by:
480 - a human-readable name, in lower case letters, with numbers as appropriate.
481 The underscore is allowed. Eg.: arm, x86_64
482 - a boolean kconfig option named after the architecture (in capital letters
483 if possible) prefixed with "ARCH_". Eg.: ARCH_ARM, ARCH_x86_64
484 - a directory in "arch/" named after the architecture, with the same letters
485 as above. Eg.: arch/arm, arch/x86_64
486 This directory contains:
487 - a configuration file in kconfig syntax, named "config.in", which may be
488 empty. Eg.: arch/arm/config.in
489 - a function script in bash-3.0 syntax, named "functions", which shall
490 follow the API defined below. Eg.: arch/arm/functions
492 The "functions" file API:
493 > the function "CT_DoArchValues"
496 - all variables from the ".config" file,
497 - the two variables "target_endian_eb" and "target_endian_el" which are
498 the endianness suffixes
499 + return value: 0 upon success, !0 upon failure
502 - the environment variable CT_TARGET_ARCH
504 the architecture part of the target tuple.
505 Eg.: "armeb" for big endian ARM
509 - the environment variable CT_TARGET_SYS
511 the sytem part of the target tuple.
512 Eg.: "gnu" for glibc on most architectures
513 "gnueabi" for glibc on an ARM EABI
515 - for glibc-based toolchain: "gnu"
516 - for uClibc-based toolchain: "uclibc"
519 - the environment variable CT_KERNEL_ARCH
521 the architecture name as understandable by the Linux kernel build
523 Eg.: "arm" for an ARM
524 "powerpc" for a PowerPC
530 - the environment variables to configure the cross-gcc
537 - contain (defaults):
538 - CT_ARCH_WITH_ARCH : the gcc ./configure switch to select architecture level ( "--with-arch=${CT_ARCH_ARCH}" )
539 - CT_ARCH_WITH_ABI : the gcc ./configure switch to select ABI level ( "--with-abi=${CT_ARCH_ABI}" )
540 - CT_ARCH_WITH_CPU : the gcc ./configure switch to select CPU instruction set ( "--with-cpu=${CT_ARCH_CPU}" )
541 - CT_ARCH_WITH_TUNE : the gcc ./configure switch to select scheduling ( "--with-tune=${CT_ARCH_TUNE}" )
542 - CT_ARCH_WITH_FPU : the gcc ./configure switch to select FPU type ( "--with-fpu=${CT_ARCH_FPU}" )
543 - CT_ARCH_WITH_FLOAT : the gcc ./configure switch to select floating point arithmetics ( "--with-float=soft" or /empty/ )
546 - the environment variables to pass to the cross-gcc to build target binaries
552 - CT_ARCH_FLOAT_CFLAG
553 - CT_ARCH_ENDIAN_CFLAG
554 - contain (defaults):
555 - CT_ARCH_ARCH_CFLAG : the gcc switch to select architecture level ( "-march=${CT_ARCH_ARCH}" )
556 - CT_ARCH_ABI_CFLAG : the gcc switch to select ABI level ( "-mabi=${CT_ARCH_ABI}" )
557 - CT_ARCH_CPU_CFLAG : the gcc switch to select CPU instruction set ( "-mcpu=${CT_ARCH_CPU}" )
558 - CT_ARCH_TUNE_CFLAG : the gcc switch to select scheduling ( "-mtune=${CT_ARCH_TUNE}" )
559 - CT_ARCH_FPU_CFLAG : the gcc switch to select FPU type ( "-mfpu=${CT_ARCH_FPU}" )
560 - CT_ARCH_FLOAT_CFLAG : the gcc switch to choose floating point arithmetics ( "-msoft-float" or /empty/ )
561 - CT_ARCH_ENDIAN_CFLAG : the gcc switch to choose big or little endian ( "-mbig-endian" or "-mlittle-endian" )
565 Adding a new version of a conponent |
566 ------------------------------------+
568 When a new component, such as the Linux kernel, gcc or any other is released,
569 adding the new version to crosstool-NG is quite easy. There is a script that
570 will do all that for you:
571 tools/addToolVersion.sh
573 Run it with no option to get some help.
578 To Be Written later...