Fix installing a glibc header for those archs that are in ports.
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". ;-)
88 ____________________________
90 Configuring crosstool-NG /
91 _________________________/
93 crosstool-NG is configured by a configurator presenting a menu-stuctured set of
94 options. These options let you specify the way you want your toolchain built,
95 where you want it installed, what architecture and specific processor it
96 will support, the version of the components you want to use, etc... The
97 value for those options are then stored in a configuration file.
99 The configurator works the same way you configure your Linux kernel.It is
100 assumed you now how to handle this.
102 To enter the menu, type:
105 Almost every config item has a help entry. Read them carefully.
107 String and number options can refer to environment variables. In such a case,
108 you must use the shell syntax: ${VAR}. You shall neither single- nor double-
109 quote the string options.
111 There are three environment variables that are computed by crosstool-NG, and
115 It represents the target triplet you are building for. You can use it for
116 example in the installation/prefix directory, such as:
117 /opt/x-tools/${CT_TARGET}
120 The top directory where crosstool-NG is running. You shouldn't need it in
121 most cases. There is one case where you may need it: if you have local
122 patches and you store them in your running directory, you can refer to them
123 by using CT_TOP_DIR, such as:
124 ${CT_TOP_DIR}/patches.myproject
127 The version of crosstool-NG you are using. Not much use for you, but it's
128 there if you need it.
131 Interesting config options |
132 ---------------------------*
134 CT_LOCAL_TARBALLS_DIR:
135 If you already have some tarballs in a direcotry, enter it here. That will
136 speed up the retrieving phase, where crosstool-NG would otherwise download
140 This is where the toolchain will be installed in (and for now, where it
141 will run from). Common use it to add the target triplet in the directory
142 path, such as (see above):
143 /opt/x-tools/${CT_TARGET}
146 An identifier for your toolchain, will take place in the vendor part of the
147 target triplet. It shall *not* contain spaces or dashes. Usually, keep it
148 to a one-word string, or use underscores to separate words if you need.
149 Avoid dots, commas, and special characters.
152 An alias for the toolchian. It will be used as a prefix to the toolchain
153 tools. For example, you will have ${CT_TARGET_ALIAS}-gcc
155 Also, if you think you don't see enough versions, you can try to enable one of
159 Show obsolete versions or tools. Most of the time, you don't want to base
160 your toolchain on too old a version (of gcc, for example). But at times, it
161 can come handy to use such an old version for regression tests. Those old
162 versions are hidden behind CT_BSOLETE.
165 Show experimental versions or tools. Again, you might not want to base your
166 toolchain on too recent tools (eg. gcc) for production. But if you need a
167 feature present only in a recent version, or a new tool, you can find them
168 hidden behind CT_EXPERIMENTAL.
171 Show broken versions or tools. Some usefull tools are currently broken: they
172 won't compile, run, or worse, cause defects when running. But if you are
173 brave enough, you can try and debug them. They are hidden behind CT_BROKEN,
174 which itself is hiddent behind EXPERIMENTAL.
176 Re-building an existing toolchain |
177 ----------------------------------+
179 If you have an existing toolchain, you can re-use the options used to build it
180 to create a new toolchain. That needs a very little bit of effort on your side
181 but is quite easy. The options to build a toolchain are saved in the build log
182 file that is saved within the toolchain. crosstool-NG can extract those options
183 to recreate a new configuration:
184 ct-ng extractconfig </path/to/your/build.log
186 will extract those options, prompt you for the new ones, which you can later
187 edit with menuconfig.
189 Of course, if your build log was compressed, you'd have to use something like:
190 bzcat /path/to/your/build.log.bz2 |ct-ng extractconfig
192 ________________________
194 Running crosstool-NG /
195 _____________________/
197 To build the toolchain, simply type:
200 This will use the above configuration to retrieve, extract and patch the
201 components, build, install and eventually test your newly built toolchain.
203 You are then free to add the toolchain /bin directory in your PATH to use
206 In any case, you can get some terse help. Just type:
212 Stoping and restarting a build |
213 -------------------------------*
215 If you want to stop the build after a step you are debugging, you can pass the
216 variable STOP to make:
219 Conversely, if you want to restart a build at a specific step you are
220 debugging, you can pass the RESTART variable to make:
221 ct-ng RESTART=some_step
223 Alternatively, you can call make with the name of a step to just do that step:
226 ct-ng RESTART=libs_headers STOP=libc_headers
228 The shortcuts -step_name and step_name- allow to respectively stop or restart
230 ct-ng -libc_headers and: ct-ng libc_headers-
232 ct-ng STOP=libc_headers and: ct-ng RESTART=libc_headers
234 To obtain the list of acceptable steps, please call:
237 Note that in order to restart a build, you'll have to say 'Y' to the config
238 option CT_DEBUG_CT_SAVE_STEPS, and that the previous build effectively went
242 Testing all toolchains at once |
243 -------------------------------*
245 You can test-build all samples; simply call:
248 _______________________
250 Using the toolchain /
251 ____________________/
253 Using the toolchain is as simple as adding the toolchain's bin directory in
255 export PATH="${PATH}:/your/toolchain/path/bin"
257 and then using the target triplet to tell the build systems to use your
259 ./configure --target=your-target-triplet
260 make CC=your-target-triplet-gcc
261 make CROSS_COMPILE=your-target-triplet-
264 When your root directory is ready, it is still missing some important bits: the
265 toolchain's libraries. To populate your root directory with those libs, just
267 your-target-triplet-populate -s /your/root -d /your/root-populated
269 This will copy /your/root into /your/root-populated, and put the needed and only
270 the needed libraries there. Thus you don't polute /your/root with any cruft that
271 would no longer be needed should you have to remove stuff. /your/root always
272 contains only those things you install in it.
274 You can then use /your/root-populated to build up your file system image, a
275 tarball, or to NFS-mount it from your target, or whatever you need.
282 There are four kinds of toolchains you could encounter.
284 First off, you must understand the following: when it comes to compilers there
285 are up to four machines involved:
286 1) the machine configuring the toolchain components: the config machine
287 2) the machine building the toolchain components: the build machine
288 3) the machine running the toolchain: the host machine
289 4) the machine the toolchain is generating code for: the target machine
291 We can most of the time assume that the config machine and the build machine
292 are the same. Most of the time, this will be true. The only time it isn't
293 is if you're using distributed compilation (such as distcc). Let's forget
294 this for the sake of simplicity.
296 So we're left with three machines:
301 Any toolchain will involve those three machines. You can be as pretty sure of
302 this as "2 and 2 are 4". Here is how they come into play:
304 1) build == host == target
305 This is a plain native toolchain, targetting the exact same machine as the
306 one it is built on, and running again on this exact same machine. You have
307 to build such a toolchain when you want to use an updated component, such
308 as a newer gcc for example.
309 crosstool-NG calls it "native".
311 2) build == host != target
312 This is a classic cross-toolchain, which is expected to be run on the same
313 machine it is compiled on, and generate code to run on a second machine,
315 crosstool-NG calls it "cross".
317 3) build != host == target
318 Such a toolchain is also a native toolchain, as it targets the same machine
319 as it runs on. But it is build on another machine. You want such a
320 toolchain when porting to a new architecture, or if the build machine is
321 much faster than the host machine.
322 crosstool-NG calls it "cross-native".
324 4) build != host != target
325 This one is called a canadian-toolchain (*), and is tricky. The three
326 machines in play are different. You might want such a toolchain if you
327 have a fast build machine, but the users will use it on another machine,
328 and will produce code to run on a third machine.
329 crosstool-NG calls it "canadian".
331 crosstool-NG can build all these kinds of toolchains (or is aiming at it,
334 (*) The term Canadian Cross came about because at the time that these issues
335 were all being hashed out, Canada had three national political parties.
336 http://en.wikipedia.org/wiki/Cross_compiler
343 Internally, crosstool-NG is script-based. To ease usage, the frontend is
349 The entry point to crosstool-NG is the Makefile script "ct-ng". Calling this
350 script with an action will act exactly as if the Makefile was in the current
351 working directory and make was called with the action as rule. Thus:
353 is equivalent to having the Makefile in CWD, and calling:
356 Having ct-ng as it is avoids copying the Makefile everywhere, and acts as a
359 ct-ng loads sub- Makefiles from the library directory $(CT_LIB_DIR), as set up
360 at configuration time with ./configure.
362 ct-ng also search for config files, sub-tools, samples, scripts and patches in
363 that library directory.
368 The kconfig language is a hacked version, vampirised from the toybox project
369 by Rob LANDLEY (http://www.landley.net/code/toybox/), itself coming from the
370 Linux kernel (http://www.linux.org/ http://www.kernel.org/), and (heavily)
373 The kconfig parsers (conf and mconf) are not installed pre-built, but as
374 source files. Thus you can have the directory where crosstool-NG is installed,
375 exported (via NFS or whatever) and have clients with different architectures
376 use the same crosstool-NG installation, and most notably, the same set of
382 To Be Written later...