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Building ARM toolchain? part 2: gcc and eglibc

Unfortunately after few tries of cross compiling eglibc using different source for instructions I alway end with hard to solve issues. Luckily, in the sources of eglibc I noticed instructions for cross-compiling written long time ago by Jim Blandy(I know i should start here). Lot of thanks to him for it. Below I describe my experience which I gained during eglibc cross compilation for arm-unknown-linux-gnueabi and procedure that I used. Commands below contain some constants that I used in previous works. See this post. Eglibc library and the compiler itself is built with many various parameters this post is not the place to explain their meaning, please RTFM.

Checkout eglibc from svn (as alwyas I try to use a latest sources possible). Version used r17815:

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svn co http://www.eglibc.org/svn/trunk eglibc

Link working ports to GNU/Linux on some machine architectures. They are not maintained in the official glibc source tree so we need to add it in this way:

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ln -s ../ports eglibc/libc/ports/

Create eglibc-headers directory:

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mkdir eglib-headers
cd eglib-headers

Configure eglibc and preliminary objects:

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BUILD_CC=gcc
CC=arm-unknown-linux-gnueabi-gcc
CXX=arm-unknown-linux-gnueabi-cpp
AR=arm-unknown-linux-gnueabi-ar
RANLIB=arm-unknown-linux-gnueabi-ranlib
../eglibc/libc/configure --prefix=/usr --with-headers=$TARGET/usr/include
    --build=x86_64-pc-linux-gnu --host=arm-unknown-linux-gnueabi --disable-profile
    --without-gd --without-cvs --enable-add-ons

Install eglibc headers:

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make install-headers install_root=$TARGET install-bootstrap-headers=yes

We need few object file to link shared libraries, which will be built and installed by hand:

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mkdir -p $TARGET/usr/lib
make csu/subdir_lib cp csu/crt1.o csu/crti.o csu/crtn.o $TARGET/usr/lib

To produce libgcc_s.so we need libc.so, but only need its dummy version because we’ll never use it. It doesn’t matter what we will point as a libc.so we use /dev/null as C file.

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arm-unknown-linux-gnueabi-gcc -nostdlib -nostartfiles -shared -x c /dev/null -o
$TARGET/usr/lib/libc.so

Get latest gcc sources using git repository mirror. Latest commit while writing this post was 5b9a8c3:

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cd ..
git clone git://repo.or.cz/official-gcc.git

Now, we can build gcc which can compile eglibc.

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mkdir eglibc-gcc
cd eglibc-gcc
../official-gcc/configure --target=arm-unknown-linux-gnueabi
    --prefix=$TARGET/arm-x-tools --with-sysroot=$TARGET --disable-libssp
    --disable-libgomp --disable-libmudflap --enable-languages=c
    --with-gmp=$TARGET/arm-x-tools --with-mpfr=$TARGET/arm-x-tools
    --with-mpc=$TARGET/arm-x-tools --disable-libquadmath --build=$MACHTYPE
    --host=$MACHTYPE --with-local-prefix=$TARGET/arm-x-tools --disable-multilib
    --with-float=soft --with-pkgversion="pietrushnic" --enable-threads=no
    --enable-target-optspace --disable-nls --enable-c99 --enable-long-long
make -j4
make install

Configure and compile final version of eglibc.

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mkdir eglibc-final
cd eglibc-final/
BUILD_CC=gcc CC=arm-unknown-linux-gnueabi-gcc CXX=arm-unknown-linux-gnueabi-cpp
AR=arm-unknown-linux-gnueabi-ar
RANLIB=arm-unknown-linux-gnueabi-ranlib
../eglibc/libc/configure --prefix=/usr --with-headers=$TARGET/usr/include
    --build=x86_64-pc-linux-gnu --host=arm-unknown-linux-gnueabi --disable-profile
    --without-gd --without-cvs --enable-add-ons
make
make install install_root=$TARGET

Install libelf library

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wget http://www.mr511.de/software/libelf-0.8.13.tar.gz
tar zxvf libelf-0.8.13.tar.gz
cd libelf-0.8.13/
./configure --prefix=$TARGET/arm-x-tools --disable-shared --enable-static
make
make install

Prepare final version of gcc.

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cd ..
mkdir final-gcc
cd final-gcc
../official-gcc/configure --target=arm-unknown-linux-gnueabi
    --prefix=$TARGET/arm-x-tools --with-sysroot=$TARGET --disable-libssp
    --disable-libgomp --disable-libmudflap --enable-languages=c,c++ --with-gmp=$TARGET/arm-x-tools
    --with-mpfr=$TARGET/arm-x-tools --with-mpc=$TARGET/arm-x-tools --disable-libquadmath
    --build=$MACHTYPE --host=$MACHTYPE --with-local-prefix=$TARGET/arm-x-tools --disable-multilib
    --with-float=soft --with-pkgversion="pietrushnic" --enable-threads=posix
    --enable-target-optspace --disable-nls --enable-c99 --enable-long-long
    --enable-__cxa_atexit --enable-symvers=gnu --with-libelf=$TARGET/arm-x-tools
    --enable-lto
make
make install

Few libraries should be copied manually

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cp -d $TARGET/arm-x-tools/arm-unknown-linux-gnueabi/lib/libgcc_s.so* $TARGET/lib
cp -d $TARGET/arm-x-tools/arm-unknown-linux-gnueabi/lib/libstdc++.so* $TARGET/lib

Compile and install chrpath - this is useful tool to remove the rpath or runpath setting from binary.

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cd ..
sudo apt-get install libc6-i386 gcc-multilib
apt-get source chrpath
cd chrpath-0.13/ CFLAGS=-m32
./configure --prefix=$TARGET/arm-x-tools --program-prefix=arm-unknown-linux-gnueabi-
make
make install

Strip debug symbols

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strip --strip-debug $TARGET/arm-x-tools/lib/*
$TARGET/arm-x-tools/arm-unknown-linux-gnueabi/lib/* $TARGET/arm-x-tools/libexec/*
strip --strip-unneeded $TARGET/arm-x-tools/bin/*
$TARGET/arm-x-tools/arm-unknown-linux-gnueabi/bin/*
arm-unknown-linux-gnueabi-strip --strip-debug $TARGET/lib/* $TARGET/usr/lib/*

At the end simple test to find out if basic functionality works:

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cat > hello.c << EOF
> #include <stdio.h>
> int
> main (int argc, char **argv)
> {
> puts ("Hello, world!");
> return 0;
> }
> EOF

Try to cross compile C file:

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$TARGET/arm-x-tools/bin/arm-unknown-linux-gnueabi-gcc -Wall hello.c -o hello
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cat > c++-hello.cc <<EOF
> #include <iostream>
> int
> main (int argc, char **argv)
> {
> std::cout return 0;
> }
> EOF

Try to cross compile C++ file:

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$TARGET/arm-x-tools/bin/arm-unknown-linux-gnueabi-g++ -Wall c++-hello.cc -o c++-hello

Displays the information contained in the ELF header and in the file’s segment headers:

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$TARGET/arm-x-tools/bin/arm-unknown-linux-gnueabi-readelf -hl hello $TARGET/arm-x-tools/bin/arm-unknown-linux-gnueabi-readelf -hl c++-hello

Result should look like that:

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ELF Header: Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 Class: ELF32 Data: 2's complement, little endian Version: 1 (current) OS/ABI: UNIX - System V ABI Version: 0 Type: EXEC (Executable file) Machine: ARM (...) Flags: 0x5000002, has entry point, Version5 EABI (...) Program Headers: (...) INTERP 0x000134 0x00008134 0x00008134 0x00013 0x00013 R 0x1 [Requesting program interpreter: /lib/ld-linux.so.3] LOAD 0x000000 0x00008000 0x00008000 0x004b8 0x004b8 R E 0x8000 (...) \``\`
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$TARGET/arm-x-tools/bin/arm-unknown-linux-gnueabi-readelf -d $TARGET/lib/libgcc_s.so.1

Result should look like that:

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(...)
Tag          Type           Name/Value
0x00000001 (NEEDED) Shared library: [libc.so.6]
0x0000000e (SONAME) Library soname: [libgcc_s.so.1]
0x0000000c (INIT) 0xcc2c (...)

I hope you find above manual useful. If you need more detailed descriptions it can be found here.


Piotr Król
Founder and Embedded Systems Consultant at 3mdeb as well as CTO of vitroTV. Passionate about building firmware that enables advanced hardware features in modern products. Dedicated to customers that treat embedded software security and upgradability as forethought. In favor of fixed price projects with the clear definition of success. Available as freelance CTO for startups and small business.