41c1cb44cd
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Acked-by: Luca Ceresoli <luca@lucaceresoli.net> Acked-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com> Reviewed-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr> Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
85 lines
4.0 KiB
Plaintext
85 lines
4.0 KiB
Plaintext
Using an external toolchain
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===========================
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Using an already existing toolchain is useful for different
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reasons:
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* you already have a toolchain that is known to work for your specific
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CPU
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* you want to speed up the Buildroot build process by skipping the
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long toolchain build part
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* the toolchain generation feature of Buildroot is not sufficiently
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flexible for you (for example if you need to generate a system with
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'glibc' instead of 'uClibc')
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Buildroot supports using existing toolchains through a mechanism
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called 'external toolchain'. The external toolchain mechanism is
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enabled in the +Toolchain+ menu, by selecting +External toolchain+ in
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+Toolchain type+.
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Then, you have three solutions to use an external toolchain:
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* Use a predefined external toolchain profile, and let Buildroot
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download, extract and install the toolchain. Buildroot already knows
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about a few CodeSourcery toolchains for ARM, PowerPC, MIPS and
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SuperH. Just select the toolchain profile in +Toolchain+ through the
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available ones. This is definitely the easiest solution.
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* Use a predefined external toolchain profile, but instead of having
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Buildroot download and extract the toolchain, you can tell Buildroot
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where your toolchain is already installed on your system. Just
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select the toolchain profile in +Toolchain+ through the available
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ones, unselect +Download toolchain automatically+, and fill the
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+Toolchain path+ text entry with the path to your cross-compiling
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toolchain.
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* Use a completely custom external toolchain. This is particularly
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useful for toolchains generated using crosstool-NG. To do this,
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select the +Custom toolchain+ solution in the +Toolchain+ list. You
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need to fill the +Toolchain path+, +Toolchain prefix+ and +External
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toolchain C library+ options. Then, you have to tell Buildroot what
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your external toolchain supports. If your external toolchain uses
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the 'glibc' library, you only have to tell whether your toolchain
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supports C++ or not. If your external toolchain uses the 'uclibc'
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library, then you have to tell Buildroot if it supports largefile,
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IPv6, RPC, wide-char, locale, program invocation, threads and
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C++. At the beginning of the execution, Buildroot will tell you if
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the selected options do not match the toolchain configuration.
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Our external toolchain support has been tested with toolchains from
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CodeSourcery, toolchains generated by
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http://crosstool-ng.org[crosstool-NG], and toolchains generated by
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Buildroot itself. In general, all toolchains that support the
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'sysroot' feature should work. If not, do not hesitate to contact the
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developers.
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We do not support toolchains from the
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http://www.denx.de/wiki/DULG/ELDK[ELDK] of Denx, for two reasons:
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* The ELDK does not contain a pure toolchain (i.e just the compiler,
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binutils, the C and C++ libraries), but a toolchain that comes with
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a very large set of pre-compiled libraries and programs. Therefore,
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Buildroot cannot import the 'sysroot' of the toolchain, as it would
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contain hundreds of megabytes of pre-compiled libraries that are
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normally built by Buildroot.
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* The ELDK toolchains have a completely non-standard custom mechanism
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to handle multiple library variants. Instead of using the standard
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GCC 'multilib' mechanism, the ARM ELDK uses different symbolic links
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to the compiler to differentiate between library variants (for ARM
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soft-float and ARM VFP), and the PowerPC ELDK compiler uses a
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+CROSS_COMPILE+ environment variable. This non-standard behaviour
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makes it difficult to support ELDK in Buildroot.
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We also do not support using the distribution toolchain (i.e the
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gcc/binutils/C library installed by your distribution) as the
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toolchain to build software for the target. This is because your
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distribution toolchain is not a "pure" toolchain (i.e only with the
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C/C++ library), so we cannot import it properly into the Buildroot
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build environment. So even if you are building a system for a x86 or
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x86_64 target, you have to generate a cross-compilation toolchain with
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Buildroot or crosstool-NG.
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