Build scripts and toolchain helpers and how to build a cross-compile and statically link gdbserver

First things first, I apologize for the poor documentation but I did not intend to write any. Hopefully it's better than nothing

What this repository is NOT

This repository is not a toolchain or a toolchain builder

What this repository kind of is

A HOWTO on building a statically linked gdbserver without much hacking

What this repository IS when fully utilized

This repository is for when you don't need something as heavy as crosstool-ng or buildroot. You just need to cross-compile and statically link a few binaries, for example gdbserver, and you have musl/uClibc/glibc toolchain to work from already built. This focuses on gdb-7.12, but you can use these scripts in one form or another when building just about anything, though you will need to modify them from time to time to suit your needs. While they function out of the box for my needs, it is best you think of them as living documentation / reference material for a simpleish task that can be confusing for first-timers, and slow for veterans

• activate-openwrt-toolchain.env - place file in prebuilt OpenWRT toolchain root, source it for productivity, etc.
• activate-musl-toolchain.env - place file in musl-cross-make toolchain root, source it for productivity, etc.
• gdbserver-7.12-static-build.sh - shell script to build a static gdb-7.12 gdbserver using a cross-compile toolchain. Should be executed from gdb-7.12-/gdb/gdbserver/

Note that you can use the --disable-build-with-cxx option when configuring gdb-7.12/gdb/gdbserver in some cases to make your life easier

ATTENTION!

If you just want to download a statically linked gdbserver for a specific MIPS(EL) or ARM platform, check the src/ directory

Just look in the in the prebuilt directory. I attempted to compile builds as portable as possible (i.e. emulating FP in software) and got a lot out of use of them, so you should find them somewhat reliable on Linux based embedded devices

If you want to build things other than gdbserver

Some open source projects have no build system, and many have very strange custom build systems that don't use the "standard" ./configure && make && make install style build system . You can check out embedded-toolkt and look in the src directory for examples of using these scripts before building various tools such as gawk, gdbserver, tcpdump, libpcap, lsof, etc which have some unique build systems, especially lsof- wtf?

OpenWrt: Use source activate-openwrt-toolchain.env with a pre-built OpenWrt Toolchain

To use activate-openwrt-toolchain.env with a pre-built OpenWrt Toolchain you can dollow these simple steps. First browse to https://downloads.openwrt.org/snapshots/trunk/ to find your toolchain

To use this script, assume you have a directory called /toolchains/ and that this is where you will keep the toolchains, one subdirectory per toolchain. You're a maniac- you're hoarding toolchains and probably up to no good. To get a new toolchain up in such a way to use active-openwrt-toolchain, grab a file like OpenWrt-Toolchain-brcm63xx-generic_gcc-5.3.0_musl-1.1.16.Linux-x86_64.tar.bz2

$ cd ~/ && git clone https://github.com/mzpqnxow/gdb-7.12-crossbuilder
$ cd gdb-7.12-crossbuilder
$ wget https://.../OpenWrt-Toolchain-brcm63xx-generic_gcc-5.3.0_musl-1.1.16.Linux-x86_64.tar.bz2
$ tar -xvjf OpenWrt-Toolchain-brcm63xx-generic_gcc-5.3.0_musl-1.1.16.Linux-x86_64.tar.bz2
$ cd OpenWrt-Toolchain-brcm63xx-generic_gcc-5.3.0_musl-1.1.16.Linux-x86_64/
$ TOOLCHAIN=$(echo toolchain-*)
$ mv "$TOOLCHAIN" /openwrt-toolchains/
$ cp ~/gdb-7.12-crossbuilder/activate-openwrt-toolchain.env /openwrt-toolchains/$TOOLCHAIN/activate
$ source /openwrt-toolchains/$TOOLCHAIN/activate

MUSL via musl-cross-make: Use source activate-musl-toolchain.env with an installed toolchain built by musl-cross-make

Using musl-cross-make is a nice experience- I recommend you try it. If you do, all you need to do is edit config.mak, use make -j and make install. That's it. You're done. The activate-musl-toolchain file is for you to place in the root of the installed toolchain to use as a convenience to "activate" the toolchain in your environment for use with weird build systems, or for software with no build system at all.

$ export TOOLCHAIN_DEST=/musl-cross-make-toolchains/toolchain-mips_mips32_musl/
$ cd ~/
$ git clone https://github.com/richfelker/musl-cross-make
$ cd musl-cross-make
$ vi config.mak
... assume you're installing to $TOOLCHAIN_DEST ...
$ make -j && make install
$ cd ~/
$ git clone https://github.com/mzpqnxow/gdb-7.12-crossbuilder
$ cd gdb-7.12-crossbuilder
$ cp activate-musl-toolchain.env $TOOLCHAIN_DEST/activate
$ source $TOOLCHAIN_DEST/activate
$ wget https://ftp.gnu.org/gnu/gdb/gdb-7.12.tar.xz
$ tar -xvf gdb-7.12.tar.xz
$ cp gdbserver-7.12-static-build.sh gdb-7.12/gdb/gdbserver
$ cd gdb-7.12/gdb/gdbserver
$ ./gdbserver-7.12-static-build.sh
$ file gdbserver
gdbserver: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), statically linked, not stripped

Capabilities provided by the shell source scripts

See the end of each .env file. You will see variables exported. Those variables can now be accessed in your shell while building software. Tools like gcc, ar, ld, g++, etc. will also now be in your path and there will be a cross_configure alias in the shell to simplify using software packages that utilize ./configure build systems

Sample environment variables after activating an OpenWrt toolchain

DL_STATIC=/opt/openwrt/armel-gnu-eabi5-sysv/lib/libdl.a
C_STATIC=/opt/openwrt/armel-gnu-eabi5-sysv/lib/libc.a
STDCXX_STATIC=/opt/openwrt/armel-gnu-eabi5-sysv/lib/libstdc++.a
UTIL_STATIC=/opt/openwrt/armel-gnu-eabi5-sysv/lib/libutil.a
PTHREAD_STATIC=/opt/openwrt/armel-gnu-eabi5-sysv/lib/libpthread.a
GCCEH_STATIC=/opt/openwrt/armel-gnu-eabi5-sysv/lib/gcc/arm-openwrt-linux-muslgnueabi/5.3.0/libgcc_eh.a
STAGING_DIR=/opt/openwrt/armel-gnu-eabi5-sysv
TOOLCHAIN_ROOT=/opt/openwrt/armel-gnu-eabi5-sysv
TOOLCHAIN_BIN=/opt/openwrt/armel-gnu-eabi5-sysv/bin
TOOLCHAIN_TARGET=arm-openwrt-linux-muslgnueabi
SYSTEM_ROOT=/opt/openwrt/armel-gnu-eabi5-sysv

Sample alias

alias cross_configure='./configure --host=arm-openwrt-linux-muslgnueabi --prefix=/opt/openwrt/armel-gnu-eabi5-sysv'

Doing a plain old build of gdbserver for the same host and target (i.e. no special toolchain)

This is not something you should really ever be doing- you will almost always be using a non-native toolchain. However, I wanted to include an example of how it can be cleanly done in a standard build environment. It assumes glibc, which is not really a good target for building non-trivial statically executables, but whatever...

Find static libraries you will need to link gdbserver with

You will need to make sure you have libstdc++.a and libgcc_eh.a on your system. If you don't know what you're doing, you can just use find. Try using the following:

$ find /l* /u* -name libgcc_eh.a
... choose the appropriate one if you have a multilib system ..
$ export LIBGCC=/usr/lib/gcc/x86_64-linux-gnu/4.9/libgcc_eh.a
$ find /l* /u* -name libstdc++.a
... choose the appropriate one if you have a multilib system ..
$ export LIBCXX=/usr/lib/gcc/x86_64-linux-gnu/4.9/libstdc++.a
$ export CC=gcc-4.9
... set this if you have multiple versions of gcc on your system ...

Perform the build

$ wget https://ftp.gnu.org/gnu/gdb/gdb-7.12.tar.xz
$ tar -xvf gdb-7.12.tar.xz
$ cd gdb-7.12/gdb/gdbserver
$ sed -i -e 's/srv_linux_thread_db=yes//' configure.srv
$ ./configure --prefix=/opt/gdbserver-7.12-static CXXFLAGS='-fPIC -static'
$ make -j gdbserver GDBSERVER_LIBS="$LIBGCC $LIBCXX"

You should now have a statically compiled GDB 7.12 gdbserver for your native OS. Read on for the cross-compile stuff, which is a little more involved but still pretty simple.

NOTE: You really should use uClibc or musl for your libc, not glibc, because getgrgid() and getpwuid() both load shared libraries. This could cause a problem if you intend to run the gdbserver executable on another machine with a different version of glibc- which more or less defeats the purpose of static linking. You will also run into issues with any application that uses libnss when linking against glibc

License

• The shell scripts and source files here are is released under the terms of GPLv2 by copyright@mzpqnxow.com
• Please see LICENSE or LICENSE.md for more information on GPLv2
• Third party software is included with license information intact