Add a directory to store contributed stuff.
It will server to hold unmerged stuff.
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.
81 ___________________________
83 Installing crosstool-NG /
84 ________________________/
86 There are two ways you can use crosstool-NG:
87 - build and install it, then get rid of the sources like you'd do for most
89 - or only build it and run from the source directory.
91 The former should be used if you got crosstool-NG from a packaged tarball, see
92 "Install method", below, while the latter is most useful for developpers that
93 checked the code out from SVN, and want to submit patches, see "The Hacker's
99 If you go for the install, then you just follow the classical, but yet easy
101 ./configure --prefix=/some/place
104 export PATH="${PATH}:/some/place/bin"
106 You can then get rid of crosstool-NG source. Next create a directory to serve
107 as a working place, cd in there and run:
110 See below for complete usage.
115 If you go the hacker's way, then the usage is a bit different, although very
120 Now, *do not* remove crosstool-NG sources. They are needed to run crosstool-NG!
121 Stay in the directory holding the sources, and run:
124 See below for complete usage.
126 Now, provided you checked-out the code, you can send me your interesting changes
130 and mailing me the result! :-P
132 ____________________________
134 Configuring crosstool-NG /
135 _________________________/
137 crosstool-NG is configured by a configurator presenting a menu-stuctured set of
138 options. These options let you specify the way you want your toolchain built,
139 where you want it installed, what architecture and specific processor it
140 will support, the version of the components you want to use, etc... The
141 value for those options are then stored in a configuration file.
143 The configurator works the same way you configure your Linux kernel.It is
144 assumed you now how to handle this.
146 To enter the menu, type:
149 Almost every config item has a help entry. Read them carefully.
151 String and number options can refer to environment variables. In such a case,
152 you must use the shell syntax: ${VAR}. You shall neither single- nor double-
153 quote the string/number options.
155 There are three environment variables that are computed by crosstool-NG, and
159 It represents the target tuple you are building for. You can use it for
160 example in the installation/prefix directory, such as:
161 /opt/x-tools/${CT_TARGET}
164 The top directory where crosstool-NG is running. You shouldn't need it in
165 most cases. There is one case where you may need it: if you have local
166 patches and you store them in your running directory, you can refer to them
167 by using CT_TOP_DIR, such as:
168 ${CT_TOP_DIR}/patches.myproject
171 The version of crosstool-NG you are using. Not much use for you, but it's
172 there if you need it.
175 Interesting config options |
176 ---------------------------*
178 CT_LOCAL_TARBALLS_DIR:
179 If you already have some tarballs in a direcotry, enter it here. That will
180 speed up the retrieving phase, where crosstool-NG would otherwise download
184 This is where the toolchain will be installed in (and for now, where it
185 will run from). Common use is to add the target tuple in the directory
186 path, such as (see above):
187 /opt/x-tools/${CT_TARGET}
190 An identifier for your toolchain, will take place in the vendor part of the
191 target tuple. It shall *not* contain spaces or dashes. Usually, keep it
192 to a one-word string, or use underscores to separate words if you need.
193 Avoid dots, commas, and special characters.
196 An alias for the toolchian. It will be used as a prefix to the toolchain
197 tools. For example, you will have ${CT_TARGET_ALIAS}-gcc
199 Also, if you think you don't see enough versions, you can try to enable one of
203 Show obsolete versions or tools. Most of the time, you don't want to base
204 your toolchain on too old a version (of gcc, for example). But at times, it
205 can come handy to use such an old version for regression tests. Those old
206 versions are hidden behind CT_OBSOLETE.
209 Show experimental versions or tools. Again, you might not want to base your
210 toolchain on too recent tools (eg. gcc) for production. But if you need a
211 feature present only in a recent version, or a new tool, you can find them
212 hidden behind CT_EXPERIMENTAL.
215 Show broken versions or tools. Some usefull tools are currently broken: they
216 won't compile, run, or worse, cause defects when running. But if you are
217 brave enough, you can try and debug them. They are hidden behind CT_BROKEN,
218 which itself is hidden behind EXPERIMENTAL.
220 Re-building an existing toolchain |
221 ----------------------------------+
223 If you have an existing toolchain, you can re-use the options used to build it
224 to create a new toolchain. That needs a very little bit of effort on your side
225 but is quite easy. The options to build a toolchain are saved in the build log
226 file that is saved within the toolchain. crosstool-NG can extract those options
227 to recreate a new configuration:
228 ct-ng extractconfig </path/to/your/build.log
230 will extract those options, prompt you for the new ones, which you can later
231 edit with menuconfig.
233 Of course, if your build log was compressed, you'd have to use something like:
234 bzcat /path/to/your/build.log.bz2 |ct-ng extractconfig
236 ________________________
238 Running crosstool-NG /
239 _____________________/
241 To build the toolchain, simply type:
244 This will use the above configuration to retrieve, extract and patch the
245 components, build, install and eventually test your newly built toolchain.
247 You are then free to add the toolchain /bin directory in your PATH to use
250 In any case, you can get some terse help. Just type:
256 Stopping and restarting a build |
257 -------------------------------*
259 If you want to stop the build after a step you are debugging, you can pass the
260 variable STOP to make:
263 Conversely, if you want to restart a build at a specific step you are
264 debugging, you can pass the RESTART variable to make:
265 ct-ng RESTART=some_step
267 Alternatively, you can call make with the name of a step to just do that step:
270 ct-ng RESTART=libs_headers STOP=libc_headers
272 The shortcuts +step_name and step_name+ allow to respectively stop or restart
274 ct-ng +libc_headers and: ct-ng libc_headers+
276 ct-ng STOP=libc_headers and: ct-ng RESTART=libc_headers
278 To obtain the list of acceptable steps, please call:
281 Note that in order to restart a build, you'll have to say 'Y' to the config
282 option CT_DEBUG_CT_SAVE_STEPS, and that the previous build effectively went
286 Testing all toolchains at once |
287 -------------------------------*
289 You can test-build all samples; simply call:
293 Overriding the number of // jobs |
294 ---------------------------------*
296 If you want to override the number of jobs to run in // (the -j option to
297 make), you can either re-enter the menuconfig, or simply add it on the command
301 which tells crosstool-NG to override the number of // jobs to 4.
303 You can see the actions that support overriding the number of // jobs in
304 the help menu. Those are the ones with [.#] after them (eg. build[.#] or
305 regtest[.#], and so on...).
307 _______________________
309 Using the toolchain /
310 ____________________/
312 Using the toolchain is as simple as adding the toolchain's bin directory in
314 export PATH="${PATH}:/your/toolchain/path/bin"
316 and then using the target tuple to tell the build systems to use your
318 ./configure --target=your-target-tuple
320 make CC=your-target-tuple-gcc
322 make CROSS_COMPILE=your-target-tuple-
325 When your root directory is ready, it is still missing some important bits: the
326 toolchain's libraries. To populate your root directory with those libs, just
328 your-target-tuple-populate -s /your/root -d /your/root-populated
330 This will copy /your/root into /your/root-populated, and put the needed and only
331 the needed libraries there. Thus you don't polute /your/root with any cruft that
332 would no longer be needed should you have to remove stuff. /your/root always
333 contains only those things you install in it.
335 You can then use /your/root-populated to build up your file system image, a
336 tarball, or to NFS-mount it from your target, or whatever you need.
338 populate accepts the following options:
341 Use 'src_dir' as the 'source', un-populated root directory
344 Put the 'destination', populated root directory in 'dst_dir'
347 Remove 'dst_dir' if it previously existed
350 Be verbose, and tell what's going on (you can see exactly where libs are
361 There are four kinds of toolchains you could encounter.
363 First off, you must understand the following: when it comes to compilers there
364 are up to four machines involved:
365 1) the machine configuring the toolchain components: the config machine
366 2) the machine building the toolchain components: the build machine
367 3) the machine running the toolchain: the host machine
368 4) the machine the toolchain is generating code for: the target machine
370 We can most of the time assume that the config machine and the build machine
371 are the same. Most of the time, this will be true. The only time it isn't
372 is if you're using distributed compilation (such as distcc). Let's forget
373 this for the sake of simplicity.
375 So we're left with three machines:
380 Any toolchain will involve those three machines. You can be as pretty sure of
381 this as "2 and 2 are 4". Here is how they come into play:
383 1) build == host == target
384 This is a plain native toolchain, targetting the exact same machine as the
385 one it is built on, and running again on this exact same machine. You have
386 to build such a toolchain when you want to use an updated component, such
387 as a newer gcc for example.
388 crosstool-NG calls it "native".
390 2) build == host != target
391 This is a classic cross-toolchain, which is expected to be run on the same
392 machine it is compiled on, and generate code to run on a second machine,
394 crosstool-NG calls it "cross".
396 3) build != host == target
397 Such a toolchain is also a native toolchain, as it targets the same machine
398 as it runs on. But it is build on another machine. You want such a
399 toolchain when porting to a new architecture, or if the build machine is
400 much faster than the host machine.
401 crosstool-NG calls it "cross-native".
403 4) build != host != target
404 This one is called a canadian-toolchain (*), and is tricky. The three
405 machines in play are different. You might want such a toolchain if you
406 have a fast build machine, but the users will use it on another machine,
407 and will produce code to run on a third machine.
408 crosstool-NG calls it "canadian".
410 crosstool-NG can build all these kinds of toolchains (or is aiming at it,
413 (*) The term Canadian Cross came about because at the time that these issues
414 were all being hashed out, Canada had three national political parties.
415 http://en.wikipedia.org/wiki/Cross_compiler
422 Internally, crosstool-NG is script-based. To ease usage, the frontend is
428 The entry point to crosstool-NG is the Makefile script "ct-ng". Calling this
429 script with an action will act exactly as if the Makefile was in the current
430 working directory and make was called with the action as rule. Thus:
433 is equivalent to having the Makefile in CWD, and calling:
436 Having ct-ng as it is avoids copying the Makefile everywhere, and acts as a
439 ct-ng loads sub- Makefiles from the library directory $(CT_LIB_DIR), as set up
440 at configuration time with ./configure.
442 ct-ng also searches for config files, sub-tools, samples, scripts and patches in
443 that library directory.
445 Because of a stupid make behavior/bug I was unable to track down, implicit make
446 rules are disabled: installing with --local would triger those rules, and mconf
452 The kconfig language is a hacked version, vampirised from the toybox project
453 by Rob LANDLEY (http://www.landley.net/code/toybox/), itself coming from the
454 Linux kernel (http://www.kernel.org/), and (heavily) adapted to my needs.
456 The kconfig parsers (conf and mconf) are not installed pre-built, but as
457 source files. Thus you can have the directory where crosstool-NG is installed,
458 exported (via NFS or whatever) and have clients with different architectures
459 use the same crosstool-NG installation, and most notably, the same set of
462 Architecture-specific |
463 ----------------------*
465 An architecture is defined by:
467 - a human-readable name, in lower case letters, with numbers as appropriate.
468 The underscore is allowed. Eg.: arm, x86_64
469 - a boolean kconfig option named after the architecture (in capital letters
470 if possible) prefixed with "ARCH_". Eg.: ARCH_ARM, ARCH_x86_64
471 - a directory in "arch/" named after the architecture, with the same letters
472 as above. Eg.: arch/arm, arch/x86_64
473 This directory contains:
474 - a configuration file in kconfig syntax, named "config.in", which may be
475 empty. Eg.: arch/arm/config.in
476 - a function script in bash-3.0 syntax, named "functions", which shall
477 follow the API defined below. Eg.: arch/arm/functions
479 The "functions" file API:
480 > the function "CT_DoArchValues"
483 - all variables from the ".config" file,
484 - the two variables "target_endian_eb" and "target_endian_el" which are
485 the endianness suffixes
486 + return value: 0 upon success, !0 upon failure
489 - the environment variable CT_TARGET_ARCH
491 the architecture part of the target tuple.
492 Eg.: "armeb" for big endian ARM
496 - the environment variable CT_TARGET_SYS
498 the sytem part of the target tuple.
499 Eg.: "gnu" for glibc on most architectures
500 "gnueabi" for glibc on an ARM EABI
502 - for glibc-based toolchain: "gnu"
503 - for uClibc-based toolchain: "uclibc"
506 - the environment variable CT_KERNEL_ARCH
508 the architecture name as understandable by the Linux kernel build
510 Eg.: "arm" for an ARM
511 "powerpc" for a PowerPC
517 - the environment variables to configure the cross-gcc
524 - contain (defaults):
525 - CT_ARCH_WITH_ARCH : the gcc ./configure switch to select architecture level ( "--with-arch=${CT_ARCH_ARCH}" )
526 - CT_ARCH_WITH_ABI : the gcc ./configure switch to select ABI level ( "--with-abi=${CT_ARCH_ARCH}" )
527 - CT_ARCH_WITH_CPU : the gcc ./configure switch to select CPU instruction set ( "--with-cpu=${CT_ARCH_ARCH}" )
528 - CT_ARCH_WITH_TUNE : the gcc ./configure switch to select scheduling ( "--with-tune=${CT_ARCH_ARCH}" )
529 - CT_ARCH_WITH_FPU : the gcc ./configure switch to select FPU type ( "--with-fpu=${CT_ARCH_ARCH}" )
530 - CT_ARCH_WITH_FLOAT : the gcc ./configure switch to select floating point arithmetics ( "--with-float=soft" or /empty/ )
533 - the environment variables to pass to the cross-gcc to build target binaries
539 - CT_ARCH_FLOAT_CFLAG
540 - CT_ARCH_ENDIAN_CFLAG
541 - contain (defaults):
542 - CT_ARCH_ARCH_CFLAG : the gcc switch to select architecture level ( "-march=${CT_ARCH_ARCH}" )
543 - CT_ARCH_ABI_CFLAG : the gcc switch to select ABI level ( "-mabi=${CT_ARCH_AABI}" )
544 - CT_ARCH_CPU_CFLAG : the gcc switch to select CPU instruction set ( "-mcpu=${CT_ARCH_CPU}" )
545 - CT_ARCH_TUNE_CFLAG : the gcc switch to select scheduling ( "-mtune=${CT_ARCH_TUNE}" )
546 - CT_ARCH_FPU_CFLAG : the gcc switch to select FPU type ( "-mfpu=${CT_ARCH_FPU}" )
547 - CT_ARCH_FLOAT_CFLAG : the gcc switch to choose floating point arithmetics ( "-msoft-float" or /empty/ )
548 - CT_ARCH_ENDIAN_CFLAG : the gcc switch to choose big or little endian ( "-mbig-endian" or "-mlittle-endian" )
556 To Be Written later...