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
14 Installing crosstool-NG
17 Preparing for packaging
20 Configuring crosstool-NG
21 Interesting config options
22 Re-building an existing toolchain
24 Stopping and restarting a build
25 Testing all toolchains at once
26 Overriding the number of // jobs
32 Seemingly-native toolchains
37 Adding a new version of a component
45 crosstool-NG aims at building toolchains. Toolchains are an essential component
46 in a software development project. It will compile, assemble and link the code
47 that is being developed. Some pieces of the toolchain will eventually end up
48 in the resulting binary/ies: static libraries are but an example.
50 So, a toolchain is a very sensitive piece of software, as any bug in one of the
51 components, or a poorly configured component, can lead to execution problems,
52 ranging from poor performance, to applications ending unexpectedly, to
53 mis-behaving software (which more than often is hard to detect), to hardware
54 damage, or even to human risks (which is more than regrettable).
56 Toolchains are made of different piece of software, each being quite complex
57 and requiring specially crafted options to build and work seamlessly. This
58 is usually not that easy, even in the not-so-trivial case of native toolchains.
59 The work reaches a higher degree of complexity when it comes to cross-
60 compilation, where it can become quite a nightmare...
62 Some cross-toolchains exist on the internet, and can be used for general
63 development, but they have a number of limitations:
64 - they can be general purpose, in that they are configured for the majority:
65 no optimisation for your specific target,
66 - they can be prepared for a specific target and thus are not easy to use,
67 nor optimised for, or even supporting your target,
68 - they often are using aging components (compiler, C library, etc...) not
69 supporting special features of your shiny new processor;
70 On the other side, these toolchain offer some advantages:
71 - they are ready to use and quite easy to install and setup,
72 - they are proven if used by a wide community.
74 But once you want to get all the juice out of your specific hardware, you will
75 want to build your own toolchain. This is where crosstool-NG comes into play.
77 There are also a number of tools that build toolchains for specific needs,
78 which are not really scalable. Examples are:
79 - buildroot (buildroot.uclibc.org) whose main purpose is to build root file
80 systems, hence the name. But once you have your toolchain with buildroot,
81 part of it is installed in the root-to-be, so if you want to build a whole
82 new root, you either have to save the existing one as a template and
83 restore it later, or restart again from scratch. This is not convenient,
84 - ptxdist (www.pengutronix.de/software/ptxdist), whose purpose is very
86 - other projects (openembedded.org for example), which are again used to
87 build root file systems.
89 crosstool-NG is really targeted at building toolchains, and only toolchains.
90 It is then up to you to use it the way you want.
97 crosstool was first 'conceived' by Dan Kegel, who offered it to the community
98 as a set of scripts, a repository of patches, and some pre-configured, general
99 purpose setup files to be used to configure crosstool. This is available at
100 http://www.kegel.com/crosstool, and the subversion repository is hosted on
101 google at http://code.google.com/p/crosstool/.
103 I once managed to add support for uClibc-based toolchains, but it did not make
104 into mainline, mostly because I didn't have time to port the patch forward to
105 the new versions, due in part to the big effort it was taking.
107 So I decided to clean up crosstool in the state it was, re-order the things
108 in place, add appropriate support for what I needed, that is uClibc support
109 and a menu-driven configuration, named the new implementation crosstool-NG,
110 (standing for crosstool Next Generation, as many other comunity projects do,
111 and as a wink at the TV series "Star Trek: The Next Generation" ;-) ) and
112 made it available to the community, in case it was of interest to any one.
114 ___________________________
116 Installing crosstool-NG /
117 ________________________/
119 There are two ways you can use crosstool-NG:
120 - build and install it, then get rid of the sources like you'd do for most
122 - or only build it and run from the source directory.
124 The former should be used if you got crosstool-NG from a packaged tarball, see
125 "Install method", below, while the latter is most useful for developpers that
126 checked the code out from SVN, and want to submit patches, see "The Hacker's
132 If you go for the install, then you just follow the classical, but yet easy
134 ./configure --prefix=/some/place
137 export PATH="${PATH}:/some/place/bin"
139 You can then get rid of crosstool-NG source. Next create a directory to serve
140 as a working place, cd in there and run:
143 See below for complete usage.
148 If you go the hacker's way, then the usage is a bit different, although very
153 Now, *do not* remove crosstool-NG sources. They are needed to run crosstool-NG!
154 Stay in the directory holding the sources, and run:
157 See below for complete usage.
159 Now, provided you used a clone of the repository, you can send me your changes.
160 See the file README, at the top of crosstool-NG source, for how to submit
163 Preparing for packaging |
164 ------------------------+
166 If you plan on packaging crosstool-NG, you surely don't want to install it
167 in your root file system. The install procedure of crosstool-NG honors the
170 ./configure --prefix=/usr
172 make DESTDIR=/packaging/place install
177 crosstool-NG comes with a shell script fragment that defines bash-compatible
178 completion. That shell fragment is currently not installed automatically, but
181 To install the shell script fragment, you have two options:
182 - install system-wide, most probably by copying ct-ng.comp into
183 /etc/bash_completion.d/
184 - install for a single user, by copying ct-ng.comp into ${HOME}/ and
185 sourcing this file from your ${HOME}/.bashrc
190 Some people contibuted code that couldn't get merged for various reasons. This
191 code is available as lzma-compressed patches, in the contrib/ sub-directory.
192 These patches are to be applied to the source of crosstool-NG, prior to
193 installing, using something like the following:
194 lzcat contrib/foobar.patch.lzma |patch -p1
196 There is no guarantee that a particuliar contribution applies to the current
197 version of crosstool-ng, or that it will work at all. Use contributions at
200 ____________________________
202 Configuring crosstool-NG /
203 _________________________/
205 crosstool-NG is configured with a configurator presenting a menu-stuctured set
206 of options. These options let you specify the way you want your toolchain
207 built, where you want it installed, what architecture and specific processor it
208 will support, the version of the components you want to use, etc... The
209 value for those options are then stored in a configuration file.
211 The configurator works the same way you configure your Linux kernel. It is
212 assumed you now how to handle this.
214 To enter the menu, type:
217 Almost every config item has a help entry. Read them carefully.
219 String and number options can refer to environment variables. In such a case,
220 you must use the shell syntax: ${VAR}. You shall neither single- nor double-
221 quote the string/number options.
223 There are three environment variables that are computed by crosstool-NG, and
227 It represents the target tuple you are building for. You can use it for
228 example in the installation/prefix directory, such as:
229 /opt/x-tools/${CT_TARGET}
232 The top directory where crosstool-NG is running. You shouldn't need it in
233 most cases. There is one case where you may need it: if you have local
234 patches and you store them in your running directory, you can refer to them
235 by using CT_TOP_DIR, such as:
236 ${CT_TOP_DIR}/patches.myproject
239 The version of crosstool-NG you are using. Not much use for you, but it's
240 there if you need it.
242 Interesting config options |
243 ---------------------------+
245 CT_LOCAL_TARBALLS_DIR:
246 If you already have some tarballs in a direcotry, enter it here. That will
247 speed up the retrieving phase, where crosstool-NG would otherwise download
251 This is where the toolchain will be installed in (and for now, where it
252 will run from). Common use is to add the target tuple in the directory
253 path, such as (see above):
254 /opt/x-tools/${CT_TARGET}
257 An identifier for your toolchain, will take place in the vendor part of the
258 target tuple. It shall *not* contain spaces or dashes. Usually, keep it
259 to a one-word string, or use underscores to separate words if you need.
260 Avoid dots, commas, and special characters.
263 An alias for the toolchian. It will be used as a prefix to the toolchain
264 tools. For example, you will have ${CT_TARGET_ALIAS}-gcc
266 Also, if you think you don't see enough versions, you can try to enable one of
270 Show obsolete versions or tools. Most of the time, you don't want to base
271 your toolchain on too old a version (of gcc, for example). But at times, it
272 can come handy to use such an old version for regression tests. Those old
273 versions are hidden behind CT_OBSOLETE. Those versions (or features) are so
274 marked because maintaining support for those in crosstool-NG would be too
275 costly, time-wise, and time is dear.
278 Show experimental versions or tools. Again, you might not want to base your
279 toolchain on too recent tools (eg. gcc) for production. But if you need a
280 feature present only in a recent version, or a new tool, you can find them
281 hidden behind CT_EXPERIMENTAL. Those versions (or features) did not (yet)
282 receive thorough testing in crosstool-NG, and/or are not mature enough to
285 Re-building an existing toolchain |
286 ----------------------------------+
288 If you have an existing toolchain, you can re-use the options used to build it
289 to create a new toolchain. That needs a very little bit of effort on your side
290 but is quite easy. The options to build a toolchain are saved with the
291 toolchain, and you can retrieve this configuration by running:
294 This will dump the configuration to stdout, so to rebuild a toolchain with this
295 configuration, the following is all you need to do:
296 ${CT_TARGET}-config >.config
299 Then, you can review and change the configuration by running:
302 ________________________
304 Running crosstool-NG /
305 _____________________/
307 To build the toolchain, simply type:
310 This will use the above configuration to retrieve, extract and patch the
311 components, build, install and eventually test your newly built toolchain.
313 You are then free to add the toolchain /bin directory in your PATH to use
316 In any case, you can get some terse help. Just type:
321 Stopping and restarting a build |
322 --------------------------------+
324 If you want to stop the build after a step you are debugging, you can pass the
325 variable STOP to make:
328 Conversely, if you want to restart a build at a specific step you are
329 debugging, you can pass the RESTART variable to make:
330 ct-ng RESTART=some_step
332 Alternatively, you can call make with the name of a step to just do that step:
335 ct-ng RESTART=libc_headers STOP=libc_headers
337 The shortcuts +step_name and step_name+ allow to respectively stop or restart
339 ct-ng +libc_headers and: ct-ng libc_headers+
341 ct-ng STOP=libc_headers and: ct-ng RESTART=libc_headers
343 To obtain the list of acceptable steps, please call:
346 Note that in order to restart a build, you'll have to say 'Y' to the config
347 option CT_DEBUG_CT_SAVE_STEPS, and that the previous build effectively went
350 Building all toolchains at once |
351 --------------------------------+
353 You can build all samples; simply call:
356 Overriding the number of // jobs |
357 ---------------------------------+
359 If you want to override the number of jobs to run in // (the -j option to
360 make), you can either re-enter the menuconfig, or simply add it on the command
364 which tells crosstool-NG to override the number of // jobs to 4.
366 You can see the actions that support overriding the number of // jobs in
367 the help menu. Those are the ones with [.#] after them (eg. build[.#] or
368 build-all[.#], and so on...).
373 The crosstool-NG script 'ct-ng' is a Makefile-script. It does *not* execute
374 in parallel (there is not much to gain). When speaking of // jobs, we are
375 refering to the number of // jobs when making the *components*. That is, we
376 speak of the number of // jobs used to build gcc, glibc, and so on...
381 Starting with gcc-4.3 come two new dependencies: GMP and MPFR. With gcc-4.4,
382 come three new ones: GMP, PPL and CLooG/ppl. These are libraries that enable
383 advanced features to gcc. Additionally, some of the libraries can be used by
384 binutils and gdb. Unfortunately, not all systems on which crosstool-NG runs
385 have all of those libraries. And for those that do, the versions of those
386 libraries may be older than the version required by gcc.
388 This is why crosstool-NG builds its own set of libraries as part of the
391 The libraries are built as shared libraries, because building them as static
392 libraries has some short-comings. This poses no problem at build time, as
393 crosstool-NG correctly points gcc (and binutils and gdb) to the correct
394 place where our own version of the libraries are installed. But it poses
395 a problem when gcc et al. are run: the place where the libraries are is most
396 probably not known to the host dynamic linker. Still worse, if the host system
397 has its own versions, then ld.so would load the wrong library!
399 So we have to force the dynamic linker to load the correct version. We do this
400 by using the LD_LIBRARY_PATH variable, that informs the dynamic linker where
401 to look for shared libraries prior to searching its standard places. But we
402 can't impose that burden on all the system (because it'd be a nightmare to
403 configure, and because two toolchains on the same system may use different
404 versions of the libraries); so we have to do it on a per-toolchain basis.
406 So we rename all binaries of the toolchain (by adding a dot '.' as their first
407 character), and add a small program, the so-called "tools wrapper", that
408 correctly sets LD_LIBRARY_PATH prior to running the real tool.
410 First, the wrapper was written as a POSIX-compliant shell script. That shell
411 script is very simple, if not trivial, and works great. The only drawback is
412 that it does not work on host systems that lack a shell, for example the
413 MingW32 environment. To solve the issue, the wrapper has been re-written in C,
414 and compiled at build time. This C wrapper is much more complex than the shell
415 script, and although it sems to be working, it's been only lightly tested.
416 Some of the expected short-comings with this C wrapper are;
417 - multi-byte file names may not be handled correctly
418 - it's really big for what it does
420 So, the default wrapper installed with your toolchain is the shell script.
421 If you know that your system is missing a shell, then you shall use the C
422 wrapper (and report back whether it works, or does not work, for you).
425 _______________________
427 Using the toolchain /
428 ____________________/
430 Using the toolchain is as simple as adding the toolchain's bin directory in
432 export PATH="${PATH}:/your/toolchain/path/bin"
434 and then using the target tuple to tell the build systems to use your
436 ./configure --target=your-target-tuple
438 make CC=your-target-tuple-gcc
440 make CROSS_COMPILE=your-target-tuple-
443 It is strongly advised not to use the toolchain sys-root directory as an
444 install directory for your programs/packages. If you do so, you will not be
445 able to use your toolchain for another project. It is even strongly advised
446 that your toolchain is chmod-ed to read-only once successfully build, so that
447 you don't go polluting your toolchain with your programs/packages' files.
449 Thus, when you build a program/package, install it in a separate directory,
450 eg. /your/root. This directory is the /image/ of what would be in the root file
451 system of your target, and will contain all that your programs/packages have
454 The 'populate' script |
455 ----------------------+
457 When your root directory is ready, it is still missing some important bits: the
458 toolchain's libraries. To populate your root directory with those libs, just
460 your-target-tuple-populate -s /your/root -d /your/root-populated
462 This will copy /your/root into /your/root-populated, and put the needed and only
463 the needed libraries there. Thus you don't polute /your/root with any cruft that
464 would no longer be needed should you have to remove stuff. /your/root always
465 contains only those things you install in it.
467 You can then use /your/root-populated to build up your file system image, a
468 tarball, or to NFS-mount it from your target, or whatever you need.
470 The populate script accepts the following options:
473 Use 'src_dir' as the un-populated root directory.
476 Put the populated root directory in 'dst_dir'.
479 Always add specified libraries.
482 Always add libraries listed in 'file'.
485 Remove 'dst_dir' if it previously existed; continue even if any library
486 specified with -l or -L is missing.
489 Be verbose, and tell what's going on (you can see exactly where libs are
495 See 'your-target-tuple-populate -h' for more information on the options.
497 Here is how populate works:
499 1) performs some sanity checks:
500 - src_dir and dst_dir are specified
502 - unless forced, dst_dir does not exist
505 2) copy src_dir to dst_dir
507 3) add forced libraries to dst_dir
508 - build the list from -l and -L options
509 - get forced libraries from the sysroot (see below for heuristics)
510 - abort on the first missing library, unless -f is specified
512 4) add all missing libraries to dst_dir
513 - scan dst_dir for every ELF files that are 'executable' or
515 - list the "NEEDED Shared library" fields
516 - check if the library is already in dst_dir/lib or dst_dir/usr/lib
517 - if not, get the library from the sysroot
518 - if it's in sysroot/lib, copy it to dst_dir/lib
519 - if it's in sysroot/usr/lib, copy it to dst_dir/usr/lib
520 - in both cases, use the SONAME of the library to create the file
522 - if it was not found in the sysroot, this is an error.
529 There are four kinds of toolchains you could encounter.
531 First off, you must understand the following: when it comes to compilers there
532 are up to four machines involved:
533 1) the machine configuring the toolchain components: the config machine
534 2) the machine building the toolchain components: the build machine
535 3) the machine running the toolchain: the host machine
536 4) the machine the toolchain is generating code for: the target machine
538 We can most of the time assume that the config machine and the build machine
539 are the same. Most of the time, this will be true. The only time it isn't
540 is if you're using distributed compilation (such as distcc). Let's forget
541 this for the sake of simplicity.
543 So we're left with three machines:
548 Any toolchain will involve those three machines. You can be as pretty sure of
549 this as "2 and 2 are 4". Here is how they come into play:
551 1) build == host == target
552 This is a plain native toolchain, targetting the exact same machine as the
553 one it is built on, and running again on this exact same machine. You have
554 to build such a toolchain when you want to use an updated component, such
555 as a newer gcc for example.
556 crosstool-NG calls it "native".
558 2) build == host != target
559 This is a classic cross-toolchain, which is expected to be run on the same
560 machine it is compiled on, and generate code to run on a second machine,
562 crosstool-NG calls it "cross".
564 3) build != host == target
565 Such a toolchain is also a native toolchain, as it targets the same machine
566 as it runs on. But it is build on another machine. You want such a
567 toolchain when porting to a new architecture, or if the build machine is
568 much faster than the host machine.
569 crosstool-NG calls it "cross-native".
571 4) build != host != target
572 This one is called a canadian-toolchain (*), and is tricky. The three
573 machines in play are different. You might want such a toolchain if you
574 have a fast build machine, but the users will use it on another machine,
575 and will produce code to run on a third machine.
576 crosstool-NG calls it "canadian".
578 crosstool-NG can build all these kinds of toolchains (or is aiming at it,
581 (*) The term Canadian Cross came about because at the time that these issues
582 were all being hashed out, Canada had three national political parties.
583 http://en.wikipedia.org/wiki/Cross_compiler
585 Seemingly-native toolchains |
586 ----------------------------+
588 Seemingly-native toolchains are toolchains that target the same architecture
589 as the one it is built on, and on which it will run, but the machine tuple
590 may be different (eg i686 vs. i386, or x86_64-unknown-linux-gnu vs.
591 x86_64-pc-linux-gnu). This also applies if the target architecture is of the
592 same kind (eg. x86 vs. x86_64, or ppc vs. ppc64).
594 Such toolchain is tricky to build, as the configure scripts may incorrectly
595 assume that files (headers and libs) from the build (or host) machine can be
596 used by the cross-compiler it is going to build. The problem seems to arise
597 only with glibc (and eglibc?) starting with version 2.7.
605 Internally, crosstool-NG is script-based. To ease usage, the frontend is
611 The entry point to crosstool-NG is the Makefile script "ct-ng". Calling this
612 script with an action will act exactly as if the Makefile was in the current
613 working directory and make was called with the action as rule. Thus:
616 is equivalent to having the Makefile in CWD, and calling:
619 Having ct-ng as it is avoids copying the Makefile everywhere, and acts as a
622 ct-ng loads sub- Makefiles from the library directory $(CT_LIB_DIR), as set up
623 at configuration time with ./configure.
625 ct-ng also searches for config files, sub-tools, samples, scripts and patches in
626 that library directory.
628 Because of a stupid make behavior/bug I was unable to track down, implicit make
629 rules are disabled: installing with --local would triger those rules, and mconf
635 The kconfig language is a hacked version, vampirised from the Linux kernel
636 (http://www.kernel.org/), and (heavily) adapted to my needs.
638 The list of the most notable changes (at least the ones I remember) follows:
639 - the CONFIG_ prefix has been replaced with CT_
640 - a leading | in prompts is skipped, and subsequent leading spaces are not
642 - otherwise leading spaces are silently trimmed
644 The kconfig parsers (conf and mconf) are not installed pre-built, but as
645 source files. Thus you can have the directory where crosstool-NG is installed,
646 exported (via NFS or whatever) and have clients with different architectures
647 use the same crosstool-NG installation, and most notably, the same set of
650 Architecture-specific |
651 ----------------------+
653 Note: this chapter is not really well written, and might thus be a little bit
654 complex to understand. To get a better grasp of what an architecture is, the
655 reader is kindly encouraged to look at the "arch/" sub-directory, and to the
656 existing architectures to see how things are laid out.
658 An architecture is defined by:
660 - a human-readable name, in lower case letters, with numbers as appropriate.
661 The underscore is allowed; space and special characters are not.
663 - a file in "config/arch/", named after the architecture's name, and suffixed
665 Eg.: config/arch/arm.in
666 - a file in "scripts/build/arch/", named after the architecture's name, and
668 Eg.: scripts/build/arch/arm.sh
670 The architecture's ".in" file API:
671 > the config option "ARCH_%arch%" (where %arch% is to be replaced with the
672 actual architecture name).
673 That config option must have *neither* a type, *nor* a prompt! Also, it can
674 *not* depend on any other config option (EXPERIMENTAL is managed as above).
678 defines a (terse) help entry for this architecture:
682 The ARM architecture.
684 selects adequate associated config options.
685 Note: 64-bit architectures *shall* select ARCH_64
688 select ARCH_SUPPORTS_BOTH_ENDIAN
689 select ARCH_DEFAULT_LE
691 The ARM architecture.
696 The x86_64 architecture.
698 > other target-specific options, at your discretion. Note however that to
699 avoid name-clashing, such options shall be prefixed with "ARCH_%arch%",
700 where %arch% is again replaced by the actual architecture name.
701 (Note: due to historical reasons, and lack of time to clean up the code,
702 I may have left some config options that do not completely conform to
703 this, as the architecture name was written all upper case. However, the
704 prefix is unique among architectures, and does not cause harm).
706 The architecture's ".sh" file API:
707 > the function "CT_DoArchTupleValues"
710 - all variables from the ".config" file,
711 - the two variables "target_endian_eb" and "target_endian_el" which are
712 the endianness suffixes
713 + return value: 0 upon success, !0 upon failure
716 - the environment variable CT_TARGET_ARCH
718 the architecture part of the target tuple.
719 Eg.: "armeb" for big endian ARM
723 - the environment variable CT_TARGET_SYS
725 the sytem part of the target tuple.
726 Eg.: "gnu" for glibc on most architectures
727 "gnueabi" for glibc on an ARM EABI
729 - for glibc-based toolchain: "gnu"
730 - for uClibc-based toolchain: "uclibc"
733 - the environment variable CT_KERNEL_ARCH
735 the architecture name as understandable by the Linux kernel build
737 Eg.: "arm" for an ARM
738 "powerpc" for a PowerPC
744 - the environment variables to configure the cross-gcc (defaults)
745 - CT_ARCH_WITH_ARCH : the gcc ./configure switch to select architecture level ( "--with-arch=${CT_ARCH_ARCH}" )
746 - CT_ARCH_WITH_ABI : the gcc ./configure switch to select ABI level ( "--with-abi=${CT_ARCH_ABI}" )
747 - CT_ARCH_WITH_CPU : the gcc ./configure switch to select CPU instruction set ( "--with-cpu=${CT_ARCH_CPU}" )
748 - CT_ARCH_WITH_TUNE : the gcc ./configure switch to select scheduling ( "--with-tune=${CT_ARCH_TUNE}" )
749 - CT_ARCH_WITH_FPU : the gcc ./configure switch to select FPU type ( "--with-fpu=${CT_ARCH_FPU}" )
750 - CT_ARCH_WITH_FLOAT : the gcc ./configure switch to select floating point arithmetics ( "--with-float=soft" or /empty/ )
753 - the environment variables to pass to the cross-gcc to build target binaries (defaults)
754 - CT_ARCH_ARCH_CFLAG : the gcc switch to select architecture level ( "-march=${CT_ARCH_ARCH}" )
755 - CT_ARCH_ABI_CFLAG : the gcc switch to select ABI level ( "-mabi=${CT_ARCH_ABI}" )
756 - CT_ARCH_CPU_CFLAG : the gcc switch to select CPU instruction set ( "-mcpu=${CT_ARCH_CPU}" )
757 - CT_ARCH_TUNE_CFLAG : the gcc switch to select scheduling ( "-mtune=${CT_ARCH_TUNE}" )
758 - CT_ARCH_FPU_CFLAG : the gcc switch to select FPU type ( "-mfpu=${CT_ARCH_FPU}" )
759 - CT_ARCH_FLOAT_CFLAG : the gcc switch to choose floating point arithmetics ( "-msoft-float" or /empty/ )
760 - CT_ARCH_ENDIAN_CFLAG : the gcc switch to choose big or little endian ( "-mbig-endian" or "-mlittle-endian" )
765 - the environement variables to configure the core and final compiler, specific to this architecture:
766 - CT_ARCH_CC_CORE_EXTRA_CONFIG : additional, architecture specific core gcc ./configure flags
767 - CT_ARCH_CC_EXTRA_CONFIG : additional, architecture specific final gcc ./configure flags
772 - the architecture-specific CFLAGS and LDFLAGS:
773 - CT_ARCH_TARGET_CLFAGS
774 - CT_ARCH_TARGET_LDFLAGS
778 You can have a look at "config/arch/arm.in" and "scripts/build/arch/arm.sh" for
779 a quite complete example of what an actual architecture description looks like.
784 A kernel is defined by:
786 - a human-readable name, in lower case letters, with numbers as appropriate.
787 The underscore is allowed; space and special characters are not (although
788 they are internally replaced with underscores.
789 Eg.: linux, bare-metal
790 - a file in "config/kernel/", named after the kernel name, and suffixed with
792 Eg.: config/kernel/linux.in, config/kernel/bare-metal.in
793 - a file in "scripts/build/kernel/", named after the kernel name, and suffixed
795 Eg.: scripts/build/kernel/linux.sh, scripts/build/kernel/bare-metal.sh
797 The kernel's ".in" file must contain:
798 > an optional lines containing exactly "# EXPERIMENTAL", starting on the
799 first column, and without any following space or other character.
800 If this line is present, then this kernel is considered EXPERIMENTAL,
801 and correct dependency on EXPERIMENTAL will be set.
803 > the config option "KERNEL_%kernel_name%" (where %kernel_name% is to be
804 replaced with the actual kernel name, with all special characters and
805 spaces replaced by underscores).
806 That config option must have *neither* a type, *nor* a prompt! Also, it can
807 *not* depends on EXPERIMENTAL.
808 Eg.: KERNEL_linux, KERNEL_bare_metal
810 defines a (terse) help entry for this kernel.
812 config KERNEL_bare_metal
814 Build a compiler for use without any kernel.
816 selects adequate associated config options.
818 config KERNEL_bare_metal
821 Build a compiler for use without any kernel.
823 > other kernel specific options, at your discretion. Note however that, to
824 avoid name-clashing, such options should be prefixed with
825 "KERNEL_%kernel_name%", where %kernel_name% is again tp be replaced with
826 the actual kernel name.
827 (Note: due to historical reasons, and lack of time to clean up the code,
828 I may have left some config options that do not completely conform to
829 this, as the kernel name was written all upper case. However, the prefix
830 is unique among kernels, and does not cause harm).
832 The kernel's ".sh" file API:
833 > is a bash script fragment
835 > defines the function CT_DoKernelTupleValues
836 + see the architecture's CT_DoArchTupleValues, except for:
837 + set the environment variable CT_TARGET_KERNEL, the kernel part of the
839 + return value: ignored
841 > defines the function "do_kernel_get":
844 - all variables from the ".config" file.
845 + return value: 0 for success, !0 for failure.
846 + behavior: download the kernel's sources, and store the tarball into
847 "${CT_TARBALLS_DIR}". To this end, a functions is available, that
848 abstracts downloading tarballs:
849 - CT_DoGet <tarball_base_name> <URL1 [URL...]>
850 Eg.: CT_DoGet linux-2.6.26.5 ftp://ftp.kernel.org/pub/linux/kernel/v2.6
851 Note: retrieving sources from svn, cvs, git and the likes is not supported
852 by CT_DoGet. You'll have to do this by hand, as it is done for eglibc in
853 "scripts/build/libc/eglibc.sh"
855 > defines the function "do_kernel_extract":
858 - all variables from the ".config" file,
859 + return value: 0 for success, !0 for failure.
860 + behavior: extract the kernel's tarball into "${CT_SRC_DIR}", and apply
861 required patches. To this end, a function is available, that abstracts
863 - CT_ExtractAndPatch <tarball_base_name>
864 Eg.: CT_ExtractAndPatch linux-2.6.26.5
866 > defines the function "do_kernel_headers":
869 - all variables from the ".config" file,
870 + return value: 0 for success, !0 for failure.
871 + behavior: install the kernel headers (if any) in "${CT_SYSROOT_DIR}/usr/include"
873 > defines any kernel-specific helper functions
874 These functions, if any, must be prefixed with "do_kernel_%CT_KERNEL%_",
875 where '%CT_KERNEL%' is to be replaced with the actual kernel name, to avoid
878 You can have a look at "config/kernel/linux.in" and "scripts/build/kernel/linux.sh"
879 as an example of what a complex kernel description looks like.
881 Adding a new version of a component |
882 ------------------------------------+
884 When a new component, such as the Linux kernel, gcc or any other is released,
885 adding the new version to crosstool-NG is quite easy. There is a script that
886 will do all that for you:
887 scripts/addToolVersion.sh
889 Run it with no option to get some help.
894 To Be Written later...