Add latest Linux kernel versions.
/trunk/config/kernel/linux_headers_install.in | 12 12 0 0 ++++++++++++
1 file changed, 12 insertions(+)
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 An easy way to use contributed code is to pass the --with-contrib= option to
139 ./configure. The possible values depend upon which contributions are packaged
140 with your version, but you can get with it with passing one of those two
143 will list all available contributions
146 will select all avalaible contributions
148 There is no guarantee that a particuliar contribution applies to the current
149 version of crosstool-ng, or that it will work at all. Use contributions at
152 ____________________________
154 Configuring crosstool-NG /
155 _________________________/
157 crosstool-NG is configured with a configurator presenting a menu-stuctured set
158 of options. These options let you specify the way you want your toolchain
159 built, where you want it installed, what architecture and specific processor it
160 will support, the version of the components you want to use, etc... The
161 value for those options are then stored in a configuration file.
163 The configurator works the same way you configure your Linux kernel. It is
164 assumed you now how to handle this.
166 To enter the menu, type:
169 Almost every config item has a help entry. Read them carefully.
171 String and number options can refer to environment variables. In such a case,
172 you must use the shell syntax: ${VAR}. You shall neither single- nor double-
173 quote the string/number options.
175 There are three environment variables that are computed by crosstool-NG, and
179 It represents the target tuple you are building for. You can use it for
180 example in the installation/prefix directory, such as:
181 /opt/x-tools/${CT_TARGET}
184 The top directory where crosstool-NG is running. You shouldn't need it in
185 most cases. There is one case where you may need it: if you have local
186 patches and you store them in your running directory, you can refer to them
187 by using CT_TOP_DIR, such as:
188 ${CT_TOP_DIR}/patches.myproject
191 The version of crosstool-NG you are using. Not much use for you, but it's
192 there if you need it.
194 Interesting config options |
195 ---------------------------+
197 CT_LOCAL_TARBALLS_DIR:
198 If you already have some tarballs in a direcotry, enter it here. That will
199 speed up the retrieving phase, where crosstool-NG would otherwise download
203 This is where the toolchain will be installed in (and for now, where it
204 will run from). Common use is to add the target tuple in the directory
205 path, such as (see above):
206 /opt/x-tools/${CT_TARGET}
209 An identifier for your toolchain, will take place in the vendor part of the
210 target tuple. It shall *not* contain spaces or dashes. Usually, keep it
211 to a one-word string, or use underscores to separate words if you need.
212 Avoid dots, commas, and special characters.
215 An alias for the toolchian. It will be used as a prefix to the toolchain
216 tools. For example, you will have ${CT_TARGET_ALIAS}-gcc
218 Also, if you think you don't see enough versions, you can try to enable one of
222 Show obsolete versions or tools. Most of the time, you don't want to base
223 your toolchain on too old a version (of gcc, for example). But at times, it
224 can come handy to use such an old version for regression tests. Those old
225 versions are hidden behind CT_OBSOLETE.
228 Show experimental versions or tools. Again, you might not want to base your
229 toolchain on too recent tools (eg. gcc) for production. But if you need a
230 feature present only in a recent version, or a new tool, you can find them
231 hidden behind CT_EXPERIMENTAL.
234 Show broken versions or tools. Some usefull tools are currently broken: they
235 won't compile, run, or worse, cause defects when running. But if you are
236 brave enough, you can try and debug them. They are hidden behind CT_BROKEN,
237 which itself is hidden behind CT_EXPERIMENTAL.
239 Re-building an existing toolchain |
240 ----------------------------------+
242 If you have an existing toolchain, you can re-use the options used to build it
243 to create a new toolchain. That needs a very little bit of effort on your side
244 but is quite easy. The options to build a toolchain are saved in the build log
245 file that is saved within the toolchain. crosstool-NG can extract those options
246 to recreate a new configuration:
247 ct-ng extractconfig </path/to/your/build.log >.config
249 will extract those options, prompt you for the new ones, which you can later
250 edit with menuconfig.
252 Of course, if your build log was compressed, you'd have to use something like:
253 bzcat /path/to/your/build.log.bz2 |ct-ng extractconfig >.config
255 Then, once the configuration has been extracted, run:
258 ________________________
260 Running crosstool-NG /
261 _____________________/
263 To build the toolchain, simply type:
266 This will use the above configuration to retrieve, extract and patch the
267 components, build, install and eventually test your newly built toolchain.
269 You are then free to add the toolchain /bin directory in your PATH to use
272 In any case, you can get some terse help. Just type:
277 Stopping and restarting a build |
278 --------------------------------+
280 If you want to stop the build after a step you are debugging, you can pass the
281 variable STOP to make:
284 Conversely, if you want to restart a build at a specific step you are
285 debugging, you can pass the RESTART variable to make:
286 ct-ng RESTART=some_step
288 Alternatively, you can call make with the name of a step to just do that step:
291 ct-ng RESTART=libc_headers STOP=libc_headers
293 The shortcuts +step_name and step_name+ allow to respectively stop or restart
295 ct-ng +libc_headers and: ct-ng libc_headers+
297 ct-ng STOP=libc_headers and: ct-ng RESTART=libc_headers
299 To obtain the list of acceptable steps, please call:
302 Note that in order to restart a build, you'll have to say 'Y' to the config
303 option CT_DEBUG_CT_SAVE_STEPS, and that the previous build effectively went
306 Testing all toolchains at once |
307 -------------------------------+
309 You can test-build all samples; simply call:
312 Overriding the number of // jobs |
313 ---------------------------------+
315 If you want to override the number of jobs to run in // (the -j option to
316 make), you can either re-enter the menuconfig, or simply add it on the command
320 which tells crosstool-NG to override the number of // jobs to 4.
322 You can see the actions that support overriding the number of // jobs in
323 the help menu. Those are the ones with [.#] after them (eg. build[.#] or
324 regtest[.#], and so on...).
326 _______________________
328 Using the toolchain /
329 ____________________/
331 Using the toolchain is as simple as adding the toolchain's bin directory in
333 export PATH="${PATH}:/your/toolchain/path/bin"
335 and then using the target tuple to tell the build systems to use your
337 ./configure --target=your-target-tuple
339 make CC=your-target-tuple-gcc
341 make CROSS_COMPILE=your-target-tuple-
344 It is strongly advised not to use the toolchain sys-root directory as an
345 install directory for your programs/packages. If you do so, you will not be
346 able to use your toolchain for another project. It is even strongly advised
347 that your toolchain is chmod-ed to read-only once successfully build, so that
348 you don't go polluting your toolchain with your programs/packages' files.
350 Thus, when you build a program/package, install it in a separate directory,
351 eg. /your/root. This directory is the /image/ of what would be in the root file
352 system of your target, and will contain all that your programs/packages have
355 When your root directory is ready, it is still missing some important bits: the
356 toolchain's libraries. To populate your root directory with those libs, just
358 your-target-tuple-populate -s /your/root -d /your/root-populated
360 This will copy /your/root into /your/root-populated, and put the needed and only
361 the needed libraries there. Thus you don't polute /your/root with any cruft that
362 would no longer be needed should you have to remove stuff. /your/root always
363 contains only those things you install in it.
365 You can then use /your/root-populated to build up your file system image, a
366 tarball, or to NFS-mount it from your target, or whatever you need.
368 populate accepts the following options:
371 Use 'src_dir' as the 'source', un-populated root directory
374 Put the 'destination', populated root directory in 'dst_dir'
377 Remove 'dst_dir' if it previously existed
380 Be verbose, and tell what's going on (you can see exactly where libs are
391 There are four kinds of toolchains you could encounter.
393 First off, you must understand the following: when it comes to compilers there
394 are up to four machines involved:
395 1) the machine configuring the toolchain components: the config machine
396 2) the machine building the toolchain components: the build machine
397 3) the machine running the toolchain: the host machine
398 4) the machine the toolchain is generating code for: the target machine
400 We can most of the time assume that the config machine and the build machine
401 are the same. Most of the time, this will be true. The only time it isn't
402 is if you're using distributed compilation (such as distcc). Let's forget
403 this for the sake of simplicity.
405 So we're left with three machines:
410 Any toolchain will involve those three machines. You can be as pretty sure of
411 this as "2 and 2 are 4". Here is how they come into play:
413 1) build == host == target
414 This is a plain native toolchain, targetting the exact same machine as the
415 one it is built on, and running again on this exact same machine. You have
416 to build such a toolchain when you want to use an updated component, such
417 as a newer gcc for example.
418 crosstool-NG calls it "native".
420 2) build == host != target
421 This is a classic cross-toolchain, which is expected to be run on the same
422 machine it is compiled on, and generate code to run on a second machine,
424 crosstool-NG calls it "cross".
426 3) build != host == target
427 Such a toolchain is also a native toolchain, as it targets the same machine
428 as it runs on. But it is build on another machine. You want such a
429 toolchain when porting to a new architecture, or if the build machine is
430 much faster than the host machine.
431 crosstool-NG calls it "cross-native".
433 4) build != host != target
434 This one is called a canadian-toolchain (*), and is tricky. The three
435 machines in play are different. You might want such a toolchain if you
436 have a fast build machine, but the users will use it on another machine,
437 and will produce code to run on a third machine.
438 crosstool-NG calls it "canadian".
440 crosstool-NG can build all these kinds of toolchains (or is aiming at it,
443 (*) The term Canadian Cross came about because at the time that these issues
444 were all being hashed out, Canada had three national political parties.
445 http://en.wikipedia.org/wiki/Cross_compiler
452 Internally, crosstool-NG is script-based. To ease usage, the frontend is
458 The entry point to crosstool-NG is the Makefile script "ct-ng". Calling this
459 script with an action will act exactly as if the Makefile was in the current
460 working directory and make was called with the action as rule. Thus:
463 is equivalent to having the Makefile in CWD, and calling:
466 Having ct-ng as it is avoids copying the Makefile everywhere, and acts as a
469 ct-ng loads sub- Makefiles from the library directory $(CT_LIB_DIR), as set up
470 at configuration time with ./configure.
472 ct-ng also searches for config files, sub-tools, samples, scripts and patches in
473 that library directory.
475 Because of a stupid make behavior/bug I was unable to track down, implicit make
476 rules are disabled: installing with --local would triger those rules, and mconf
482 The kconfig language is a hacked version, vampirised from the toybox project
483 by Rob LANDLEY (http://www.landley.net/code/toybox/), itself coming from the
484 Linux kernel (http://www.kernel.org/), and (heavily) adapted to my needs.
486 The kconfig parsers (conf and mconf) are not installed pre-built, but as
487 source files. Thus you can have the directory where crosstool-NG is installed,
488 exported (via NFS or whatever) and have clients with different architectures
489 use the same crosstool-NG installation, and most notably, the same set of
492 Architecture-specific |
493 ----------------------+
495 An architecture is defined by:
497 - a human-readable name, in lower case letters, with numbers as appropriate.
498 The underscore is allowed. Eg.: arm, x86_64
499 - a boolean kconfig option named after the architecture (in capital letters
500 if possible) prefixed with "ARCH_". Eg.: ARCH_ARM, ARCH_x86_64
501 - a directory in "arch/" named after the architecture, with the same letters
502 as above. Eg.: arch/arm, arch/x86_64
503 This directory contains:
504 - a configuration file in kconfig syntax, named "config.in", which may be
505 empty. Eg.: arch/arm/config.in
506 - a function script in bash-3.0 syntax, named "functions", which shall
507 follow the API defined below. Eg.: arch/arm/functions
509 The "functions" file API:
510 > the function "CT_DoArchValues"
513 - all variables from the ".config" file,
514 - the two variables "target_endian_eb" and "target_endian_el" which are
515 the endianness suffixes
516 + return value: 0 upon success, !0 upon failure
519 - the environment variable CT_TARGET_ARCH
521 the architecture part of the target tuple.
522 Eg.: "armeb" for big endian ARM
526 - the environment variable CT_TARGET_SYS
528 the sytem part of the target tuple.
529 Eg.: "gnu" for glibc on most architectures
530 "gnueabi" for glibc on an ARM EABI
532 - for glibc-based toolchain: "gnu"
533 - for uClibc-based toolchain: "uclibc"
536 - the environment variable CT_KERNEL_ARCH
538 the architecture name as understandable by the Linux kernel build
540 Eg.: "arm" for an ARM
541 "powerpc" for a PowerPC
547 - the environment variables to configure the cross-gcc
554 - contain (defaults):
555 - CT_ARCH_WITH_ARCH : the gcc ./configure switch to select architecture level ( "--with-arch=${CT_ARCH_ARCH}" )
556 - CT_ARCH_WITH_ABI : the gcc ./configure switch to select ABI level ( "--with-abi=${CT_ARCH_ABI}" )
557 - CT_ARCH_WITH_CPU : the gcc ./configure switch to select CPU instruction set ( "--with-cpu=${CT_ARCH_CPU}" )
558 - CT_ARCH_WITH_TUNE : the gcc ./configure switch to select scheduling ( "--with-tune=${CT_ARCH_TUNE}" )
559 - CT_ARCH_WITH_FPU : the gcc ./configure switch to select FPU type ( "--with-fpu=${CT_ARCH_FPU}" )
560 - CT_ARCH_WITH_FLOAT : the gcc ./configure switch to select floating point arithmetics ( "--with-float=soft" or /empty/ )
563 - the environment variables to pass to the cross-gcc to build target binaries
569 - CT_ARCH_FLOAT_CFLAG
570 - CT_ARCH_ENDIAN_CFLAG
571 - contain (defaults):
572 - CT_ARCH_ARCH_CFLAG : the gcc switch to select architecture level ( "-march=${CT_ARCH_ARCH}" )
573 - CT_ARCH_ABI_CFLAG : the gcc switch to select ABI level ( "-mabi=${CT_ARCH_ABI}" )
574 - CT_ARCH_CPU_CFLAG : the gcc switch to select CPU instruction set ( "-mcpu=${CT_ARCH_CPU}" )
575 - CT_ARCH_TUNE_CFLAG : the gcc switch to select scheduling ( "-mtune=${CT_ARCH_TUNE}" )
576 - CT_ARCH_FPU_CFLAG : the gcc switch to select FPU type ( "-mfpu=${CT_ARCH_FPU}" )
577 - CT_ARCH_FLOAT_CFLAG : the gcc switch to choose floating point arithmetics ( "-msoft-float" or /empty/ )
578 - CT_ARCH_ENDIAN_CFLAG : the gcc switch to choose big or little endian ( "-mbig-endian" or "-mlittle-endian" )
582 Adding a new version of a component |
583 ------------------------------------+
585 When a new component, such as the Linux kernel, gcc or any other is released,
586 adding the new version to crosstool-NG is quite easy. There is a script that
587 will do all that for you:
588 tools/addToolVersion.sh
590 Run it with no option to get some help.
595 To Be Written later...