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 patches in the contrib/ sub-directory. These patches are
192 to be applied to the source of crosstool-NG, prior to installing.
194 An easy way to use contributed code is to pass the --with-contrib= option to
195 ./configure. The possible values depend upon which contributions are packaged
196 with your version, but you can get with it with passing one of those two
199 will list all available contributions
202 will select all avalaible contributions
204 There is no guarantee that a particuliar contribution applies to the current
205 version of crosstool-ng, or that it will work at all. Use contributions at
208 ____________________________
210 Configuring crosstool-NG /
211 _________________________/
213 crosstool-NG is configured with a configurator presenting a menu-stuctured set
214 of options. These options let you specify the way you want your toolchain
215 built, where you want it installed, what architecture and specific processor it
216 will support, the version of the components you want to use, etc... The
217 value for those options are then stored in a configuration file.
219 The configurator works the same way you configure your Linux kernel. It is
220 assumed you now how to handle this.
222 To enter the menu, type:
225 Almost every config item has a help entry. Read them carefully.
227 String and number options can refer to environment variables. In such a case,
228 you must use the shell syntax: ${VAR}. You shall neither single- nor double-
229 quote the string/number options.
231 There are three environment variables that are computed by crosstool-NG, and
235 It represents the target tuple you are building for. You can use it for
236 example in the installation/prefix directory, such as:
237 /opt/x-tools/${CT_TARGET}
240 The top directory where crosstool-NG is running. You shouldn't need it in
241 most cases. There is one case where you may need it: if you have local
242 patches and you store them in your running directory, you can refer to them
243 by using CT_TOP_DIR, such as:
244 ${CT_TOP_DIR}/patches.myproject
247 The version of crosstool-NG you are using. Not much use for you, but it's
248 there if you need it.
250 Interesting config options |
251 ---------------------------+
253 CT_LOCAL_TARBALLS_DIR:
254 If you already have some tarballs in a direcotry, enter it here. That will
255 speed up the retrieving phase, where crosstool-NG would otherwise download
259 This is where the toolchain will be installed in (and for now, where it
260 will run from). Common use is to add the target tuple in the directory
261 path, such as (see above):
262 /opt/x-tools/${CT_TARGET}
265 An identifier for your toolchain, will take place in the vendor part of the
266 target tuple. It shall *not* contain spaces or dashes. Usually, keep it
267 to a one-word string, or use underscores to separate words if you need.
268 Avoid dots, commas, and special characters.
271 An alias for the toolchian. It will be used as a prefix to the toolchain
272 tools. For example, you will have ${CT_TARGET_ALIAS}-gcc
274 Also, if you think you don't see enough versions, you can try to enable one of
278 Show obsolete versions or tools. Most of the time, you don't want to base
279 your toolchain on too old a version (of gcc, for example). But at times, it
280 can come handy to use such an old version for regression tests. Those old
281 versions are hidden behind CT_OBSOLETE. Those versions (or features) are so
282 marked because maintaining support for those in crosstool-NG would be too
283 costly, time-wise, and time is dear.
286 Show experimental versions or tools. Again, you might not want to base your
287 toolchain on too recent tools (eg. gcc) for production. But if you need a
288 feature present only in a recent version, or a new tool, you can find them
289 hidden behind CT_EXPERIMENTAL. Those versions (or features) did not (yet)
290 receive thorough testing in crosstool-NG, and/or are not mature enough to
293 Re-building an existing toolchain |
294 ----------------------------------+
296 If you have an existing toolchain, you can re-use the options used to build it
297 to create a new toolchain. That needs a very little bit of effort on your side
298 but is quite easy. The options to build a toolchain are saved with the
299 toolchain, and you can retrieve this configuration by running:
302 This will dump the configuration to stdout, so to rebuild a toolchain with this
303 configuration, the following is all you need to do:
304 ${CT_TARGET}-config >.config
307 Then, you can review and change the configuration by running:
310 ________________________
312 Running crosstool-NG /
313 _____________________/
315 To build the toolchain, simply type:
318 This will use the above configuration to retrieve, extract and patch the
319 components, build, install and eventually test your newly built toolchain.
321 You are then free to add the toolchain /bin directory in your PATH to use
324 In any case, you can get some terse help. Just type:
329 Stopping and restarting a build |
330 --------------------------------+
332 If you want to stop the build after a step you are debugging, you can pass the
333 variable STOP to make:
336 Conversely, if you want to restart a build at a specific step you are
337 debugging, you can pass the RESTART variable to make:
338 ct-ng RESTART=some_step
340 Alternatively, you can call make with the name of a step to just do that step:
343 ct-ng RESTART=libc_headers STOP=libc_headers
345 The shortcuts +step_name and step_name+ allow to respectively stop or restart
347 ct-ng +libc_headers and: ct-ng libc_headers+
349 ct-ng STOP=libc_headers and: ct-ng RESTART=libc_headers
351 To obtain the list of acceptable steps, please call:
354 Note that in order to restart a build, you'll have to say 'Y' to the config
355 option CT_DEBUG_CT_SAVE_STEPS, and that the previous build effectively went
358 Building all toolchains at once |
359 --------------------------------+
361 You can build all samples; simply call:
364 Overriding the number of // jobs |
365 ---------------------------------+
367 If you want to override the number of jobs to run in // (the -j option to
368 make), you can either re-enter the menuconfig, or simply add it on the command
372 which tells crosstool-NG to override the number of // jobs to 4.
374 You can see the actions that support overriding the number of // jobs in
375 the help menu. Those are the ones with [.#] after them (eg. build[.#] or
376 build-all[.#], and so on...).
381 The crosstool-NG script 'ct-ng' is a Makefile-script. It does *not* execute
382 in parallel (there is not much to gain). When speaking of // jobs, we are
383 refering to the number of // jobs when making the *components*. That is, we
384 speak of the number of // jobs used to build gcc, glibc, and so on...
389 Starting with gcc-4.3 come two new dependencies: GMP and MPFR. With gcc-4.4,
390 come three new ones: GMP, PPL and CLooG/ppl. These are libraries that enable
391 advanced features to gcc. Additionally, some of the libraries can be used by
392 binutils and gdb. Unfortunately, not all systems on which crosstool-NG runs
393 have all of those libraries. And for those that do, the versions of those
394 libraries may be older than the version required by gcc.
396 This is why crosstool-NG builds its own set of libraries as part of the
399 The libraries are built as shared libraries, because building them as static
400 libraries has some short-comings. This poses no problem at build time, as
401 crosstool-NG correctly points gcc (and binutils and gdb) to the correct
402 place where our own version of the libraries are installed. But it poses
403 a problem when gcc et al. are run: the place where the libraries are is most
404 probably not known to the host dynamic linker. Still worse, if the host system
405 has its own versions, then ld.so would load the wrong library!
407 So we have to force the dynamic linker to load the correct version. We do this
408 by using the LD_LIBRARY_PATH variable, that informs the dynamic linker where
409 to look for shared libraries prior to searching its standard places. But we
410 can't impose that burden on all the system (because it'd be a nightmare to
411 configure, and because two toolchains on the same system may use different
412 versions of the libraries); so we have to do it on a per-toolchain basis.
414 So we rename all binaries of the toolchain (by adding a dot '.' as their first
415 character), and add a small program, the so-called "tools wrapper", that
416 correctly sets LD_LIBRARY_PATH prior to running the real tool.
418 First, the wrapper was written as a POSIX-compliant shell script. That shell
419 script is very simple, if not trivial, and works great. The only drawback is
420 that it does not work on host systems that lack a shell, for example the
421 MingW32 environment. To solve the issue, the wrapper has been re-written in C,
422 and compiled at build time. This C wrapper is much more complex than the shell
423 script, and although it sems to be working, it's been only lightly tested.
424 Some of the expected short-comings with this C wrapper are;
425 - multi-byte file names may not be handled correctly
426 - it's really big for what it does
428 So, the default wrapper installed with your toolchain is the shell script.
429 If you know that your system is missing a shell, then you shall use the C
430 wrapper (and report back whether it works, or does not work, for you).
433 _______________________
435 Using the toolchain /
436 ____________________/
438 Using the toolchain is as simple as adding the toolchain's bin directory in
440 export PATH="${PATH}:/your/toolchain/path/bin"
442 and then using the target tuple to tell the build systems to use your
444 ./configure --target=your-target-tuple
446 make CC=your-target-tuple-gcc
448 make CROSS_COMPILE=your-target-tuple-
451 It is strongly advised not to use the toolchain sys-root directory as an
452 install directory for your programs/packages. If you do so, you will not be
453 able to use your toolchain for another project. It is even strongly advised
454 that your toolchain is chmod-ed to read-only once successfully build, so that
455 you don't go polluting your toolchain with your programs/packages' files.
457 Thus, when you build a program/package, install it in a separate directory,
458 eg. /your/root. This directory is the /image/ of what would be in the root file
459 system of your target, and will contain all that your programs/packages have
462 The 'populate' script |
463 ----------------------+
465 When your root directory is ready, it is still missing some important bits: the
466 toolchain's libraries. To populate your root directory with those libs, just
468 your-target-tuple-populate -s /your/root -d /your/root-populated
470 This will copy /your/root into /your/root-populated, and put the needed and only
471 the needed libraries there. Thus you don't polute /your/root with any cruft that
472 would no longer be needed should you have to remove stuff. /your/root always
473 contains only those things you install in it.
475 You can then use /your/root-populated to build up your file system image, a
476 tarball, or to NFS-mount it from your target, or whatever you need.
478 The populate script accepts the following options:
481 Use 'src_dir' as the un-populated root directory.
484 Put the populated root directory in 'dst_dir'.
487 Always add specified libraries.
490 Always add libraries listed in 'file'.
493 Remove 'dst_dir' if it previously existed; continue even if any library
494 specified with -l or -L is missing.
497 Be verbose, and tell what's going on (you can see exactly where libs are
503 See 'your-target-tuple-populate -h' for more information on the options.
505 Here is how populate works:
507 1) performs some sanity checks:
508 - src_dir and dst_dir are specified
510 - unless forced, dst_dir does not exist
513 2) copy src_dir to dst_dir
515 3) add forced libraries to dst_dir
516 - build the list from -l and -L options
517 - get forced libraries from the sysroot (see below for heuristics)
518 - abort on the first missing library, unless -f is specified
520 4) add all missing libraries to dst_dir
521 - scan dst_dir for every ELF files that are 'executable' or
523 - list the "NEEDED Shared library" fields
524 - check if the library is already in dst_dir/lib or dst_dir/usr/lib
525 - if not, get the library from the sysroot
526 - if it's in sysroot/lib, copy it to dst_dir/lib
527 - if it's in sysroot/usr/lib, copy it to dst_dir/usr/lib
528 - in both cases, use the SONAME of the library to create the file
530 - if it was not found in the sysroot, this is an error.
537 There are four kinds of toolchains you could encounter.
539 First off, you must understand the following: when it comes to compilers there
540 are up to four machines involved:
541 1) the machine configuring the toolchain components: the config machine
542 2) the machine building the toolchain components: the build machine
543 3) the machine running the toolchain: the host machine
544 4) the machine the toolchain is generating code for: the target machine
546 We can most of the time assume that the config machine and the build machine
547 are the same. Most of the time, this will be true. The only time it isn't
548 is if you're using distributed compilation (such as distcc). Let's forget
549 this for the sake of simplicity.
551 So we're left with three machines:
556 Any toolchain will involve those three machines. You can be as pretty sure of
557 this as "2 and 2 are 4". Here is how they come into play:
559 1) build == host == target
560 This is a plain native toolchain, targetting the exact same machine as the
561 one it is built on, and running again on this exact same machine. You have
562 to build such a toolchain when you want to use an updated component, such
563 as a newer gcc for example.
564 crosstool-NG calls it "native".
566 2) build == host != target
567 This is a classic cross-toolchain, which is expected to be run on the same
568 machine it is compiled on, and generate code to run on a second machine,
570 crosstool-NG calls it "cross".
572 3) build != host == target
573 Such a toolchain is also a native toolchain, as it targets the same machine
574 as it runs on. But it is build on another machine. You want such a
575 toolchain when porting to a new architecture, or if the build machine is
576 much faster than the host machine.
577 crosstool-NG calls it "cross-native".
579 4) build != host != target
580 This one is called a canadian-toolchain (*), and is tricky. The three
581 machines in play are different. You might want such a toolchain if you
582 have a fast build machine, but the users will use it on another machine,
583 and will produce code to run on a third machine.
584 crosstool-NG calls it "canadian".
586 crosstool-NG can build all these kinds of toolchains (or is aiming at it,
589 (*) The term Canadian Cross came about because at the time that these issues
590 were all being hashed out, Canada had three national political parties.
591 http://en.wikipedia.org/wiki/Cross_compiler
593 Seemingly-native toolchains |
594 ----------------------------+
596 Seemingly-native toolchains are toolchains that target the same architecture
597 as the one it is built on, and on which it will run, but the machine tuple
598 may be different (eg i686 vs. i386, or x86_64-unknown-linux-gnu vs.
599 x86_64-pc-linux-gnu). This also applies if the target architecture is of the
600 same kind (eg. x86 vs. x86_64, or ppc vs. ppc64).
602 Such toolchain is tricky to build, as the configure scripts may incorrectly
603 assume that files (headers and libs) from the build (or host) machine can be
604 used by the cross-compiler it is going to build. The problem seems to arise
605 only with glibc (and eglibc?) starting with version 2.7.
613 Internally, crosstool-NG is script-based. To ease usage, the frontend is
619 The entry point to crosstool-NG is the Makefile script "ct-ng". Calling this
620 script with an action will act exactly as if the Makefile was in the current
621 working directory and make was called with the action as rule. Thus:
624 is equivalent to having the Makefile in CWD, and calling:
627 Having ct-ng as it is avoids copying the Makefile everywhere, and acts as a
630 ct-ng loads sub- Makefiles from the library directory $(CT_LIB_DIR), as set up
631 at configuration time with ./configure.
633 ct-ng also searches for config files, sub-tools, samples, scripts and patches in
634 that library directory.
636 Because of a stupid make behavior/bug I was unable to track down, implicit make
637 rules are disabled: installing with --local would triger those rules, and mconf
643 The kconfig language is a hacked version, vampirised from the Linux kernel
644 (http://www.kernel.org/), and (heavily) adapted to my needs.
646 The list of the most notable changes (at least the ones I remember) follows:
647 - the CONFIG_ prefix has been replaced with CT_
648 - a leading | in prompts is skipped, and subsequent leading spaces are not
650 - otherwise leading spaces are silently trimmed
652 The kconfig parsers (conf and mconf) are not installed pre-built, but as
653 source files. Thus you can have the directory where crosstool-NG is installed,
654 exported (via NFS or whatever) and have clients with different architectures
655 use the same crosstool-NG installation, and most notably, the same set of
658 Architecture-specific |
659 ----------------------+
661 Note: this chapter is not really well written, and might thus be a little bit
662 complex to understand. To get a better grasp of what an architecture is, the
663 reader is kindly encouraged to look at the "arch/" sub-directory, and to the
664 existing architectures to see how things are laid out.
666 An architecture is defined by:
668 - a human-readable name, in lower case letters, with numbers as appropriate.
669 The underscore is allowed; space and special characters are not.
671 - a file in "config/arch/", named after the architecture's name, and suffixed
673 Eg.: config/arch/arm.in
674 - a file in "scripts/build/arch/", named after the architecture's name, and
676 Eg.: scripts/build/arch/arm.sh
678 The architecture's ".in" file API:
679 > the config option "ARCH_%arch%" (where %arch% is to be replaced with the
680 actual architecture name).
681 That config option must have *neither* a type, *nor* a prompt! Also, it can
682 *not* depend on any other config option (EXPERIMENTAL is managed as above).
686 defines a (terse) help entry for this architecture:
690 The ARM architecture.
692 selects adequate associated config options.
693 Note: 64-bit architectures *shall* select ARCH_64
696 select ARCH_SUPPORTS_BOTH_ENDIAN
697 select ARCH_DEFAULT_LE
699 The ARM architecture.
704 The x86_64 architecture.
706 > other target-specific options, at your discretion. Note however that to
707 avoid name-clashing, such options shall be prefixed with "ARCH_%arch%",
708 where %arch% is again replaced by the actual architecture name.
709 (Note: due to historical reasons, and lack of time to clean up the code,
710 I may have left some config options that do not completely conform to
711 this, as the architecture name was written all upper case. However, the
712 prefix is unique among architectures, and does not cause harm).
714 The architecture's ".sh" file API:
715 > the function "CT_DoArchTupleValues"
718 - all variables from the ".config" file,
719 - the two variables "target_endian_eb" and "target_endian_el" which are
720 the endianness suffixes
721 + return value: 0 upon success, !0 upon failure
724 - the environment variable CT_TARGET_ARCH
726 the architecture part of the target tuple.
727 Eg.: "armeb" for big endian ARM
731 - the environment variable CT_TARGET_SYS
733 the sytem part of the target tuple.
734 Eg.: "gnu" for glibc on most architectures
735 "gnueabi" for glibc on an ARM EABI
737 - for glibc-based toolchain: "gnu"
738 - for uClibc-based toolchain: "uclibc"
741 - the environment variable CT_KERNEL_ARCH
743 the architecture name as understandable by the Linux kernel build
745 Eg.: "arm" for an ARM
746 "powerpc" for a PowerPC
752 - the environment variables to configure the cross-gcc (defaults)
753 - CT_ARCH_WITH_ARCH : the gcc ./configure switch to select architecture level ( "--with-arch=${CT_ARCH_ARCH}" )
754 - CT_ARCH_WITH_ABI : the gcc ./configure switch to select ABI level ( "--with-abi=${CT_ARCH_ABI}" )
755 - CT_ARCH_WITH_CPU : the gcc ./configure switch to select CPU instruction set ( "--with-cpu=${CT_ARCH_CPU}" )
756 - CT_ARCH_WITH_TUNE : the gcc ./configure switch to select scheduling ( "--with-tune=${CT_ARCH_TUNE}" )
757 - CT_ARCH_WITH_FPU : the gcc ./configure switch to select FPU type ( "--with-fpu=${CT_ARCH_FPU}" )
758 - CT_ARCH_WITH_FLOAT : the gcc ./configure switch to select floating point arithmetics ( "--with-float=soft" or /empty/ )
761 - the environment variables to pass to the cross-gcc to build target binaries (defaults)
762 - CT_ARCH_ARCH_CFLAG : the gcc switch to select architecture level ( "-march=${CT_ARCH_ARCH}" )
763 - CT_ARCH_ABI_CFLAG : the gcc switch to select ABI level ( "-mabi=${CT_ARCH_ABI}" )
764 - CT_ARCH_CPU_CFLAG : the gcc switch to select CPU instruction set ( "-mcpu=${CT_ARCH_CPU}" )
765 - CT_ARCH_TUNE_CFLAG : the gcc switch to select scheduling ( "-mtune=${CT_ARCH_TUNE}" )
766 - CT_ARCH_FPU_CFLAG : the gcc switch to select FPU type ( "-mfpu=${CT_ARCH_FPU}" )
767 - CT_ARCH_FLOAT_CFLAG : the gcc switch to choose floating point arithmetics ( "-msoft-float" or /empty/ )
768 - CT_ARCH_ENDIAN_CFLAG : the gcc switch to choose big or little endian ( "-mbig-endian" or "-mlittle-endian" )
773 - the environement variables to configure the core and final compiler, specific to this architecture:
774 - CT_ARCH_CC_CORE_EXTRA_CONFIG : additional, architecture specific core gcc ./configure flags
775 - CT_ARCH_CC_EXTRA_CONFIG : additional, architecture specific final gcc ./configure flags
780 - the architecture-specific CFLAGS and LDFLAGS:
781 - CT_ARCH_TARGET_CLFAGS
782 - CT_ARCH_TARGET_LDFLAGS
786 You can have a look at "config/arch/arm.in" and "scripts/build/arch/arm.sh" for
787 a quite complete example of what an actual architecture description looks like.
792 A kernel is defined by:
794 - a human-readable name, in lower case letters, with numbers as appropriate.
795 The underscore is allowed; space and special characters are not (although
796 they are internally replaced with underscores.
797 Eg.: linux, bare-metal
798 - a file in "config/kernel/", named after the kernel name, and suffixed with
800 Eg.: config/kernel/linux.in, config/kernel/bare-metal.in
801 - a file in "scripts/build/kernel/", named after the kernel name, and suffixed
803 Eg.: scripts/build/kernel/linux.sh, scripts/build/kernel/bare-metal.sh
805 The kernel's ".in" file must contain:
806 > an optional lines containing exactly "# EXPERIMENTAL", starting on the
807 first column, and without any following space or other character.
808 If this line is present, then this kernel is considered EXPERIMENTAL,
809 and correct dependency on EXPERIMENTAL will be set.
811 > the config option "KERNEL_%kernel_name%" (where %kernel_name% is to be
812 replaced with the actual kernel name, with all special characters and
813 spaces replaced by underscores).
814 That config option must have *neither* a type, *nor* a prompt! Also, it can
815 *not* depends on EXPERIMENTAL.
816 Eg.: KERNEL_linux, KERNEL_bare_metal
818 defines a (terse) help entry for this kernel.
820 config KERNEL_bare_metal
822 Build a compiler for use without any kernel.
824 selects adequate associated config options.
826 config KERNEL_bare_metal
829 Build a compiler for use without any kernel.
831 > other kernel specific options, at your discretion. Note however that, to
832 avoid name-clashing, such options should be prefixed with
833 "KERNEL_%kernel_name%", where %kernel_name% is again tp be replaced with
834 the actual kernel name.
835 (Note: due to historical reasons, and lack of time to clean up the code,
836 I may have left some config options that do not completely conform to
837 this, as the kernel name was written all upper case. However, the prefix
838 is unique among kernels, and does not cause harm).
840 The kernel's ".sh" file API:
841 > is a bash script fragment
843 > defines the function CT_DoKernelTupleValues
844 + see the architecture's CT_DoArchTupleValues, except for:
845 + set the environment variable CT_TARGET_KERNEL, the kernel part of the
847 + return value: ignored
849 > defines the function "do_kernel_get":
852 - all variables from the ".config" file.
853 + return value: 0 for success, !0 for failure.
854 + behavior: download the kernel's sources, and store the tarball into
855 "${CT_TARBALLS_DIR}". To this end, a functions is available, that
856 abstracts downloading tarballs:
857 - CT_DoGet <tarball_base_name> <URL1 [URL...]>
858 Eg.: CT_DoGet linux-2.6.26.5 ftp://ftp.kernel.org/pub/linux/kernel/v2.6
859 Note: retrieving sources from svn, cvs, git and the likes is not supported
860 by CT_DoGet. You'll have to do this by hand, as it is done for eglibc in
861 "scripts/build/libc/eglibc.sh"
863 > defines the function "do_kernel_extract":
866 - all variables from the ".config" file,
867 + return value: 0 for success, !0 for failure.
868 + behavior: extract the kernel's tarball into "${CT_SRC_DIR}", and apply
869 required patches. To this end, a function is available, that abstracts
871 - CT_ExtractAndPatch <tarball_base_name>
872 Eg.: CT_ExtractAndPatch linux-2.6.26.5
874 > defines the function "do_kernel_headers":
877 - all variables from the ".config" file,
878 + return value: 0 for success, !0 for failure.
879 + behavior: install the kernel headers (if any) in "${CT_SYSROOT_DIR}/usr/include"
881 > defines any kernel-specific helper functions
882 These functions, if any, must be prefixed with "do_kernel_%CT_KERNEL%_",
883 where '%CT_KERNEL%' is to be replaced with the actual kernel name, to avoid
886 You can have a look at "config/kernel/linux.in" and "scripts/build/kernel/linux.sh"
887 as an example of what a complex kernel description looks like.
889 Adding a new version of a component |
890 ------------------------------------+
892 When a new component, such as the Linux kernel, gcc or any other is released,
893 adding the new version to crosstool-NG is quite easy. There is a script that
894 will do all that for you:
895 scripts/addToolVersion.sh
897 Run it with no option to get some help.
902 To Be Written later...