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diff --git a/doc/CROSS-COMPILE-GUTS b/doc/CROSS-COMPILE-GUTS new file mode 100644 index 0000000..8453a6e --- /dev/null +++ b/doc/CROSS-COMPILE-GUTS @@ -0,0 +1,284 @@ +----- +Intro +----- + +2006-06-08 Mike Frysinger <vapier@gentoo.org> + +brain dumpage of cross-compiling low level details + +target audience: +people who (for some stupid reason or another) really really want to create +their own cross compiler with binutils/(glibc|uclibc)/gcc all by themselves. + +what this isn't: +this document makes no attempt whatsoever to cover the myriad of build +failures you are likely to see along the way. if you need such help, see the +References section at the end of this file for some pointers. don't bug me :P + + +-------- +Overview +-------- + +There are generally two ways to build up your cross-compiler. The "accepted" +way, and the cheater's shortcut. + +The current "accepted" way is: + (1) binutils + (2) kernel headers + (3) libc headers + (4) gcc stage1 (c-only) + (5) libc + (6) gcc stage2 (c/c++/etc...) + +The cheater's shortcut is: + (1) binutils + (2) gcc stage1 (c-only) + (3) kernel headers + (4) libc + (5) gcc stage2 (c/c++/etc...) + +The reason people are keen on the shortcut is that the libc headers step tends +to take quite a while, especially on slower machines. It can also be kind of +a pain to setup kernel/libc headers without a usuable cross compiler. Note +though that if you seek help with cross-compilers, upstream projects will not +want to help you if you took the shortcut. + +Also note that the shortcut requires the gcc stage1 to be "crippled". Since +you're building without headers, you cannot enable the sysroot option nor can +you build up proper gcc libs. This is OK if the only thing you use the stage1 +is building the C library and a kernel, but beyond that you need a nice +sysroot based compiler. + +Below I will describe the "accepted" way as the steps are pretty much the +same. You just need some extra patches for gcc in order to take the shortcut. + + +------- +Targets +------- + +<explain target tuples here> + + +------- +Sysroot +------- + +We will be cross-compiling using the sysroot method. But wtf is sysroot ? + +From the gcc docs: + Tells GCC to consider dir as the root of a tree that contains a (subset of) + the root filesystem of the target operating system. Target system headers, + libraries and run-time object files will be searched in there. + +The structure of the sysroot dir is the same as the root filesystem of the +machine you're targeting with the cross-compiler. In Gentoo/portage terms, +it's like using ROOT. Let's look at the typical setup. + +The top level dir is commonly rooted in /usr/$CTARGET +/usr/$CTARGET/ +|-- bin/ +|-- lib/ critical runtime libs (libc/ldso/etc...) +`-- usr/ + |-- include/ development headers + | |-- linux/ like the linux kernel + | `-- asm/ like the arch-specific + `-- lib/ non critical runtime libs / development libs + +As you can see, it's just like the directory setup / but in /usr/$CTARGET. +This setup is on purpose so you can easily migrate applications/libraries +out of /usr/$CTARGET and into / on your target board. + +Non-sysroot note: +The old style of cross-compilers was to use --prefix=/usr/$CTARGET. If you +are using versions of binutils/gcc that predate sysroot support, you may have +to do just this. + + +-------- +Binutils +-------- + +Grab the binutils-2.16.1.tar.bz2 tarball and unpack it. + +The --disable-werror configure option is to prevent binutils from aborting +the compile due to warnings. Great feature for developers, pita for users. + +To configure/build/install: + +$ ./configure \ + --target=$CTARGET \ + --prefix=/usr \ + --with-sysroot=/usr/$CTARGET \ + --disable-werror +$ make +$ make install DESTDIR=$PWD/install-root + +The reason we install into the localdir is so we can remove crap that doesn't +belong. For example, a normal install will give us /usr/lib/libiberty.a which +doesn't belong in our host /usr/lib. So clean out stuff first: + +$ rm -rf install-root/usr/{info,lib,man,share} + +And install what's left: + +# cp -a install-root/* / + + +-------------- +Kernel headers +-------------- + +Grab the linux-2.6.16.tar.bz2 tarball and unpack it. + +$ yes "" | make ARCH=$ARCH oldconfig prepare + +With 2.6.x, this will probably end in an error because you don't have a gcc +cross-compiler yet, but you can ignore that. Just copy over the headers: + +# mkdir -p /usr/$CTARGET/usr/include +# cp -a include/linux include/asm-generic /usr/$CTARGET/usr/include/ +# cp -a include/asm-$ARCH /usr/$CTARGET/usr/include/asm + + +------------ +libc headers +------------ + + -- glibc -- + +Grab the glibc-2.4.tar.bz2 tarball and unpack it. Glibc is picky, so you'll +have to compile in a dir separate from the source code. + +Again, you'll probably see errors because you don't have a gcc cross-compiler +yet, but just ignore them. + +$ mkdir build +$ cd build +$ ../configure \ + --host=$CTARGET \ + --prefix=/usr \ + --with-headers=/usr/$CTARGET/usr/include \ + --disable-sanity-checks +# make -k install-headers install_root=/usr/$CTARGET + +glibc sucks at life so you have to do a few things by hand: + +# mkdir -p /usr/$CTARGET/usr/include/gnu +# touch /usr/$CTARGET/usr/include/gnu/stubs.h +# cp bits/stdio_lim.h /usr/$CTARGET/usr/include/bits/ + + + -- uClibc -- + +Grab the uClibc-0.9.28.tar.bz2 tarball and unpack it. + + +---------- +GCC stage1 +---------- + +We first have to help gcc find the current libc headers. + +# ln -s usr/include /usr/$CTARGET/sys-include + +Grab the gcc-4.1.1.tar.bz2 tarball and unpack it. + +$ mkdir build +$ cd build +$ ../configure \ + --target=$CTARGET \ + --prefix=/usr \ + --with-sysroot=/usr/$CTARGET \ + --enable-languages=c \ + --disable-shared \ + --disable-checking \ + --disable-werror \ + --disable-libmudflap \ + --disable-libssp +$ make +$ make install DESTDIR=$PWD/install-root + +Same as binutils, gcc leaves some stuff behind we don't want. + +$ rm -rf install-root/usr/{info,include,lib/libiberty.a,man,share} + +Install what's left: + +# cp -a install-root/* / + + +---------- +libc +---------- + + -- glibc -- + +Nuke the old glibc build dir and recreate it. + +$ rm -rf build +$ mkdir build +$ cd build +$ ../configure \ + --host=$CTARGET \ + --prefix=/usr +$ make +# make install install_root=/usr/$CTARGET + + -- uClibc -- + + + +---------- +GCC stage2 +---------- + +$ ./configure \ + --target=$CTARGET \ + --prefix=/usr \ + --with-sysroot=/usr/$CTARGET \ + --enable-languages=c,c++ \ + --enable-shared \ + --disable-checking \ + --disable-werror +$ make +# make install + + +---- +Help +---- + +Where to seek help: +The crossgcc mailing list: http://sourceware.org/ml/crossgcc/ +Google: http://www.google.com/ + + +---------- +References +---------- + +Gentoo Homepage: http://embedded.gentoo.org/ + +crosstool: http://www.kegel.com/crosstool/ + +Binutils Homepage: http://sourceware.org/binutils/ +Binutils Download: http://ftp.gnu.org/gnu/binutils/ +Binutils Manual: http://sourceware.org/binutils/docs-2.16/ + +GCC Homepage: http://gcc.gnu.org/ +GCC Download: http://ftp.gnu.org/gnu/gcc/ +GCC Manual: http://gcc.gnu.org/onlinedocs/ +GCC Install Docs: http://gcc.gnu.org/install/ + +Glibc Homepage: http://www.gnu.org/software/libc/ +Glibc Download: http://ftp.gnu.org/gnu/glibc/ +Glibc Manual: http://www.gnu.org/software/libc/manual/ +Glibc Install Docs: http://www.gnu.org/software/libc/manual/html_node/Installation.html#Installation + +uClibc Homepage: http://www.uClibc.org/ +uClibc Download: http://www.uclibc.org/downloads/ + +Linux Kernel Homepage: http://www.kernel.org/ +Linux Kernel Download: http://www.kernel.org/pub/linux/kernel/ |