Add linux-2.6.22.{8,9}.
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 developped. 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 regretable).
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 ageing 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 builds toolchains for specific needs,
44 which is not really scalable. Examples are:
45 - buildroot (buildroot.uclibc.org) whose main puprpose 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 (openembeded.org for example), which is again used to
53 build root file systems.
55 crosstool-NG is really targetted 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, which 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 At the time of writing, crosstool only supports building with one C library,
70 namely glibc, and one C compiler, gcc; it is cripled with historical support
71 for legacy components, and is some kind of a mess to upgrade. Also, submited
72 patches take a loooong time before they are integrated mainline.
74 I once managed to add support for uClibc-based toolchains, but it did not make
75 into mainline, mostly because I don't have time to port the patch forward to
76 the new versions, due in part to the big effort it was taking.
78 So I decided to clean up crosstool in the state it was, re-order the things
79 in place, and add appropriate support for what I needed, that is uClibc
80 support. That was a disaster, as inclusion into mainline is slow as hell,
81 and the changes were so numerous.
83 The only option left to me was rewrite crosstool from scratch. I decided to go
84 this way, and name the new implementation crosstool-NG, standing for crosstool
85 Next Generation, as many other comunity projects do, and as a wink at the TV
86 series "Star Trek: The Next Generation". ;-)
89 ___________________________
91 Installing crosstool-NG /
92 ________________________/
94 There are two ways you can use crosstool-NG:
95 - build and install it, then get rid of the sources like you'd do for most
97 - or only build it and run from the source directory.
99 The former should be used if you got crosstool-NG from a packaged tarball, see
100 "Install method", below, while the latter is most usefull for developpers that
101 checked the code out from SVN, and want to submit patches, see "The Hacker's
107 If you go for the install, then you just follow the classical, but yet easy
109 ./configure --prefix=/some/place
112 export PATH="${PATH}:/some/place/bin"
114 You can then get rid of crosstool-NG source. Next create a directory to serve
115 as a working place, cd in there and run:
118 See below for complete usage.
123 If you go the hacker's way, then the usage is a bit different, although very
128 Now, *do not* remove crosstool-NG sources. They are needed to run crosstool-NG!
129 Stay in the directory holding the sources, and run:
132 See below for complete usage.
134 Now, provided you checked-out the code, you can send me your interesting changes
138 and mailing me the result! :-P
140 ____________________________
142 Configuring crosstool-NG /
143 _________________________/
145 crosstool-NG is configured by a configurator presenting a menu-stuctured set of
146 options. These options let you specify the way you want your toolchain built,
147 where you want it installed, what architecture and specific processor it
148 will support, the version of the components you want to use, etc... The
149 value for those options are then stored in a configuration file.
151 The configurator works the same way you configure your Linux kernel.It is
152 assumed you now how to handle this.
154 To enter the menu, type:
157 Almost every config item has a help entry. Read them carefully.
159 String and number options can refer to environment variables. In such a case,
160 you must use the shell syntax: ${VAR}. You shall neither single- nor double-
161 quote the string/number options.
163 There are three environment variables that are computed by crosstool-NG, and
167 It represents the target tuple you are building for. You can use it for
168 example in the installation/prefix directory, such as:
169 /opt/x-tools/${CT_TARGET}
172 The top directory where crosstool-NG is running. You shouldn't need it in
173 most cases. There is one case where you may need it: if you have local
174 patches and you store them in your running directory, you can refer to them
175 by using CT_TOP_DIR, such as:
176 ${CT_TOP_DIR}/patches.myproject
179 The version of crosstool-NG you are using. Not much use for you, but it's
180 there if you need it.
183 Interesting config options |
184 ---------------------------*
186 CT_LOCAL_TARBALLS_DIR:
187 If you already have some tarballs in a direcotry, enter it here. That will
188 speed up the retrieving phase, where crosstool-NG would otherwise download
192 This is where the toolchain will be installed in (and for now, where it
193 will run from). Common use it to add the target tuple in the directory
194 path, such as (see above):
195 /opt/x-tools/${CT_TARGET}
198 An identifier for your toolchain, will take place in the vendor part of the
199 target tuple. It shall *not* contain spaces or dashes. Usually, keep it
200 to a one-word string, or use underscores to separate words if you need.
201 Avoid dots, commas, and special characters.
204 An alias for the toolchian. It will be used as a prefix to the toolchain
205 tools. For example, you will have ${CT_TARGET_ALIAS}-gcc
207 Also, if you think you don't see enough versions, you can try to enable one of
211 Show obsolete versions or tools. Most of the time, you don't want to base
212 your toolchain on too old a version (of gcc, for example). But at times, it
213 can come handy to use such an old version for regression tests. Those old
214 versions are hidden behind CT_OBSOLETE.
217 Show experimental versions or tools. Again, you might not want to base your
218 toolchain on too recent tools (eg. gcc) for production. But if you need a
219 feature present only in a recent version, or a new tool, you can find them
220 hidden behind CT_EXPERIMENTAL.
223 Show broken versions or tools. Some usefull tools are currently broken: they
224 won't compile, run, or worse, cause defects when running. But if you are
225 brave enough, you can try and debug them. They are hidden behind CT_BROKEN,
226 which itself is hidden behind EXPERIMENTAL.
228 Re-building an existing toolchain |
229 ----------------------------------+
231 If you have an existing toolchain, you can re-use the options used to build it
232 to create a new toolchain. That needs a very little bit of effort on your side
233 but is quite easy. The options to build a toolchain are saved in the build log
234 file that is saved within the toolchain. crosstool-NG can extract those options
235 to recreate a new configuration:
236 ct-ng extractconfig </path/to/your/build.log
238 will extract those options, prompt you for the new ones, which you can later
239 edit with menuconfig.
241 Of course, if your build log was compressed, you'd have to use something like:
242 bzcat /path/to/your/build.log.bz2 |ct-ng extractconfig
244 ________________________
246 Running crosstool-NG /
247 _____________________/
249 To build the toolchain, simply type:
252 This will use the above configuration to retrieve, extract and patch the
253 components, build, install and eventually test your newly built toolchain.
255 You are then free to add the toolchain /bin directory in your PATH to use
258 In any case, you can get some terse help. Just type:
264 Stoping and restarting a build |
265 -------------------------------*
267 If you want to stop the build after a step you are debugging, you can pass the
268 variable STOP to make:
271 Conversely, if you want to restart a build at a specific step you are
272 debugging, you can pass the RESTART variable to make:
273 ct-ng RESTART=some_step
275 Alternatively, you can call make with the name of a step to just do that step:
278 ct-ng RESTART=libs_headers STOP=libc_headers
280 The shortcuts +step_name and step_name+ allow to respectively stop or restart
282 ct-ng +libc_headers and: ct-ng libc_headers+
284 ct-ng STOP=libc_headers and: ct-ng RESTART=libc_headers
286 To obtain the list of acceptable steps, please call:
289 Note that in order to restart a build, you'll have to say 'Y' to the config
290 option CT_DEBUG_CT_SAVE_STEPS, and that the previous build effectively went
294 Testing all toolchains at once |
295 -------------------------------*
297 You can test-build all samples; simply call:
301 Overriding the number of // jobs |
302 ---------------------------------*
304 If you want to override the number of jobs to run in // (the -j option to
305 make), you can either re-enter the menuconfig, or simply add it on the command
309 which tells crosstool-NG to override the number of // jobs to 4.
311 You can see the actions that support overriding the number of // jobs in
312 the help menu. Those are the ones with [.#] after them (eg. build[.#] or
313 regtest[.#], and so on...).
315 _______________________
317 Using the toolchain /
318 ____________________/
320 Using the toolchain is as simple as adding the toolchain's bin directory in
322 export PATH="${PATH}:/your/toolchain/path/bin"
324 and then using the target tuple to tell the build systems to use your
326 ./configure --target=your-target-tuple
328 make CC=your-target-tuple-gcc
330 make CROSS_COMPILE=your-target-tuple-
333 When your root directory is ready, it is still missing some important bits: the
334 toolchain's libraries. To populate your root directory with those libs, just
336 your-target-tuple-populate -s /your/root -d /your/root-populated
338 This will copy /your/root into /your/root-populated, and put the needed and only
339 the needed libraries there. Thus you don't polute /your/root with any cruft that
340 would no longer be needed should you have to remove stuff. /your/root always
341 contains only those things you install in it.
343 You can then use /your/root-populated to build up your file system image, a
344 tarball, or to NFS-mount it from your target, or whatever you need.
346 populate accepts the following options:
349 Use 'src_dir' as the 'source', un-populated root directory
352 Put the 'destination', populated root directory in 'dst_dir'
355 Remove 'dst_dir' if it previously existed
358 Be verbose, and tell what's going on (you can see exactly where libs are
369 There are four kinds of toolchains you could encounter.
371 First off, you must understand the following: when it comes to compilers there
372 are up to four machines involved:
373 1) the machine configuring the toolchain components: the config machine
374 2) the machine building the toolchain components: the build machine
375 3) the machine running the toolchain: the host machine
376 4) the machine the toolchain is generating code for: the target machine
378 We can most of the time assume that the config machine and the build machine
379 are the same. Most of the time, this will be true. The only time it isn't
380 is if you're using distributed compilation (such as distcc). Let's forget
381 this for the sake of simplicity.
383 So we're left with three machines:
388 Any toolchain will involve those three machines. You can be as pretty sure of
389 this as "2 and 2 are 4". Here is how they come into play:
391 1) build == host == target
392 This is a plain native toolchain, targetting the exact same machine as the
393 one it is built on, and running again on this exact same machine. You have
394 to build such a toolchain when you want to use an updated component, such
395 as a newer gcc for example.
396 crosstool-NG calls it "native".
398 2) build == host != target
399 This is a classic cross-toolchain, which is expected to be run on the same
400 machine it is compiled on, and generate code to run on a second machine,
402 crosstool-NG calls it "cross".
404 3) build != host == target
405 Such a toolchain is also a native toolchain, as it targets the same machine
406 as it runs on. But it is build on another machine. You want such a
407 toolchain when porting to a new architecture, or if the build machine is
408 much faster than the host machine.
409 crosstool-NG calls it "cross-native".
411 4) build != host != target
412 This one is called a canadian-toolchain (*), and is tricky. The three
413 machines in play are different. You might want such a toolchain if you
414 have a fast build machine, but the users will use it on another machine,
415 and will produce code to run on a third machine.
416 crosstool-NG calls it "canadian".
418 crosstool-NG can build all these kinds of toolchains (or is aiming at it,
421 (*) The term Canadian Cross came about because at the time that these issues
422 were all being hashed out, Canada had three national political parties.
423 http://en.wikipedia.org/wiki/Cross_compiler
430 Internally, crosstool-NG is script-based. To ease usage, the frontend is
436 The entry point to crosstool-NG is the Makefile script "ct-ng". Calling this
437 script with an action will act exactly as if the Makefile was in the current
438 working directory and make was called with the action as rule. Thus:
441 is equivalent to having the Makefile in CWD, and calling:
444 Having ct-ng as it is avoids copying the Makefile everywhere, and acts as a
447 ct-ng loads sub- Makefiles from the library directory $(CT_LIB_DIR), as set up
448 at configuration time with ./configure.
450 ct-ng also search for config files, sub-tools, samples, scripts and patches in
451 that library directory.
453 Because of a stupid make behavior/bug I was unable to track down, implicit make
454 rules are disabled: installing with --local would triger those rules, and mconf
460 The kconfig language is a hacked version, vampirised from the toybox project
461 by Rob LANDLEY (http://www.landley.net/code/toybox/), itself coming from the
462 Linux kernel (http://www.kernel.org/), and (heavily) adapted to my needs.
464 The kconfig parsers (conf and mconf) are not installed pre-built, but as
465 source files. Thus you can have the directory where crosstool-NG is installed,
466 exported (via NFS or whatever) and have clients with different architectures
467 use the same crosstool-NG installation, and most notably, the same set of
470 Architecture-specific |
471 ----------------------*
473 An architecture is defined by:
475 - a human-readable name, in lower case letters, with numbers as appropriate.
476 The underscore is allowed. Eg.: arm, x86_64
477 - a boolean kconfig option named after the architecture (in capital letters
478 if possible) prefixed with "ARCH_". Eg.: ARCH_ARM, ARCH_x86_64
479 - a directory in "arch/" named after the architecture, with the same letters
480 as above. Eg.: arch/arm, arch/x86_64
481 This directory contains:
482 - a configuration file in kconfig syntax, named "config.in", which may be
483 empty. Eg.: arch/arm/config.in
484 - a function script in bash-3.0 syntax, named "functions", which shall
485 follow the API defined below. Eg.: arch/arm/functions
487 The "functions" file API:
488 > the function "CT_DoArchValues"
491 - all variables from the ".config" file,
492 - the two variables "target_endian_eb" and "target_endian_el" which are
493 the endianness suffixes
494 + return value: 0 upon success, !0 upon failure
497 - the environment variable CT_TARGET_ARCH
499 the architecture part of the target tuple.
500 Eg.: "armeb" for big endian ARM
504 - the environment variable CT_TARGET_SYS
506 the sytem part of the target tuple.
507 Eg.: "gnu" for glibc on most architectures
508 "gnueabi" for glibc on an ARM EABI
510 - for glibc-based toolchain: "gnu"
511 - for uClibc-based toolchain: "uclibc"
514 - the environment variable CT_KERNEL_ARCH
516 the architecture name as understandable by the Linux kernel build
518 Eg.: "arm" for an ARM
519 "powerpc" for a PowerPC
525 - the environment variables to configure the cross-gcc
532 - contain (defaults):
533 - CT_ARCH_WITH_ARCH : the gcc ./configure switch to select architecture level ( "--with-arch=${CT_ARCH_ARCH}" )
534 - CT_ARCH_WITH_ABI : the gcc ./configure switch to select ABI level ( "--with-abi=${CT_ARCH_ARCH}" )
535 - CT_ARCH_WITH_CPU : the gcc ./configure switch to select CPU instruction set ( "--with-cpu=${CT_ARCH_ARCH}" )
536 - CT_ARCH_WITH_TUNE : the gcc ./configure switch to select scheduling ( "--with-tune=${CT_ARCH_ARCH}" )
537 - CT_ARCH_WITH_FPU : the gcc ./configure switch to select FPU type ( "--with-fpu=${CT_ARCH_ARCH}" )
538 - CT_ARCH_WITH_FLOAT : the gcc ./configure switch to select floating point arithmetics ( "--with-float=soft" or /empty/ )
541 - the environment variables to pass to the cross-gcc to build target binaries
547 - CT_ARCH_FLOAT_CFLAG
548 - CT_ARCH_ENDIAN_CFLAG
549 - contain (defaults):
550 - CT_ARCH_ARCH_CFLAG : the gcc switch to select architecture level ( "-march=${CT_ARCH_ARCH}" )
551 - CT_ARCH_ABI_CFLAG : the gcc switch to select ABI level ( "-mabi=${CT_ARCH_AABI}" )
552 - CT_ARCH_CPU_CFLAG : the gcc switch to select CPU instruction set ( "-mcpu=${CT_ARCH_CPU}" )
553 - CT_ARCH_TUNE_CFLAG : the gcc switch to select scheduling ( "-mtune=${CT_ARCH_TUNE}" )
554 - CT_ARCH_FPU_CFLAG : the gcc switch to select FPU type ( "-mfpu=${CT_ARCH_FPU}" )
555 - CT_ARCH_FLOAT_CFLAG : the gcc switch to choose floating point arithmetics ( "-msoft-float" or /empty/ )
556 - CT_ARCH_ENDIAN_CFLAG : the gcc switch to choose big or little endian ( "-mbig-endian" or "-mlittle-endian" )
564 To Be Written later...