The ARM architecture receives a huge performance advantage by using a hard-float tool-chain, however most distributions only provide a soft-float tool-chain. CodeSourcery charges a fee for a hard-float tool-chain, but this post will show you how to build one using crosstool-NG.
I’ll specifically detail the process for a Cortex-A8, but the same principles apply for other ARM architectures. My build environment is Ubuntu 11.10 with a Freescale i.MX53 Quick Start development board.
This is a post for advanced gcc/Linux/Toolchain developers. Please do not proceed unless you fully understand concepts such as hard-float (vfp and neon), soft-float, ARM, Linux and gcc linking.
Firstly, download and install the latest crosstool-NG (This post uses 1.13.2)
tar -xvjf crosstool-ng-1.13.2.tar.bz2
cd crosstool-ng-1.13.2
./configure --prefix=$PWD
make
make install
Configure ct-ng:
Firstly, configure the paths and misc options. This is mostly user dependent, but I thought I would show my settings:
Then go into Target Options:
You must configure for the vfpv3 floating point engine in this step and you must use -mfloat-abi=hard. ARM processors will have different vfp options, such as vfpv3 or vfpv3-d16. You can also use neon here if you want. Choose the right one for your processor. The cortex-a8 tuning is an optimization step and is CPU dependent.
For reference the following are the equivalents in the configuration file:
CT_ARCH_CPU=”cortex-a8″
CT_ARCH_TUNE=”cortex-a8″
CT_ARCH_FPU=”vfpv3″
CT_TARGET_CFLAGS=”-mfloat-abi=hard -mfpu=vfpv3″
Then we configure the toolchain options. Nothing really hard here, I have decided to give the toolchain a vendor string (cortex_a8) and an alias (arm-):
Next, we look at the target Operating System. I have used Linux 3.0.4 as my target operating system.
Next we setup the binary utilities, nothing too exciting here:
Now we come to the interesting part, the C-compiler settings and C-library settings. To overcome the performance penalty of a soft-float toolchain, we need to rebuild everything as hard-float. This includes the gcc libraries and glibc.
Firstly the C-compiler settings:
You can setup any components of gcc that you require, but the important setup is Core gcc extra config and gcc extra config. These must be set to –with-float=hard.
For reference they are these elements in the config file:
CT_CC_CORE_EXTRA_CONFIG_ARRAY=”–with-float=hard”
CT_CC_EXTRA_CONFIG_ARRAY=”–with-float=hard”
Next, we setup the C-library options. We must build glibc (or equivalent C library) with the correct hard-float options.
In this case extra target CFLAGS and gcc extra flags must be set to -mfloat-abi=hard -mfpu=vfpv3. These options are different to the C-compiler setup because in this case we are passing these options into the gcc to build glibc. In the C-compiler setup, we were configuring gcc and gcc’s libraries (libgcc, libstdc++, etc).
For reference here are the equivalent parameters in the configuration file:
CT_LIBC_GLIBC_EXTRA_CFLAGS=”-U_FORTIFY_SOURCE -mfloat-abi=hard -mfpu=vfpv3″
CT_LIBC_EXTRA_CC_ARGS=”-mfloat-abi=hard -mfpu=vfpv3″
The next four configuration screens, Debug Facilities, Companion Libraries, Companian Tools and Test Suite, I will leave to the user to configure, but I will show the screen-shot of Companion Libraries in case you need it:
Ok, so the configuring is done. At this stage you may want to review the crosstool-NG instructions to make sure that your machine is setup correctly to build the toolchain.
Lets build the toolchain. Firstly, create the tarballs directory we used in configure:
Build the toolchain using ct-ng. My example uses 8 cores, but you should adjust this for your build machine:
Well, the toolchain will probably take 30 minutes to build on an i7. If all goes well you will end up with a build log like this:
[INFO ] Performing some trivial sanity checks [INFO ] Build started 20111204.164331 [INFO ] Building environment variables [EXTRA] Preparing working directories [EXTRA] Installing user-supplied crosstool-NG configuration [EXTRA] ================================================================= [EXTRA] Dumping internal crosstool-NG configuration [EXTRA] Building a toolchain for: [EXTRA] build = x86_64-unknown-linux-gnu [EXTRA] host = x86_64-unknown-linux-gnu [EXTRA] target = arm-cortex_a8-linux-gnueabi [EXTRA] Dumping internal crosstool-NG configuration: done in 0.10s (at 00:02) [INFO ] ================================================================= [INFO ] Retrieving needed toolchain components' tarballs [INFO ] Retrieving needed toolchain components' tarballs: done in 0.16s (at 00:02) [INFO ] ================================================================= [INFO ] Extracting and patching toolchain components [INFO ] Extracting and patching toolchain components: done in 3.87s (at 00:06) [INFO ] ================================================================= [INFO ] Installing GMP [EXTRA] Configuring GMP [EXTRA] Building GMP [EXTRA] Installing GMP [INFO ] Installing GMP: done in 43.53s (at 00:50) [INFO ] ================================================================= [INFO ] Installing MPFR [EXTRA] Configuring MPFR [EXTRA] Building MPFR [EXTRA] Installing MPFR [INFO ] Installing MPFR: done in 16.18s (at 01:06) [INFO ] ================================================================= [INFO ] Installing PPL [EXTRA] Configuring PPL [EXTRA] Building PPL [EXTRA] Installing PPL [INFO ] Installing PPL: done in 165.04s (at 03:51) [INFO ] ================================================================= [INFO ] Installing CLooG/ppl [EXTRA] Configuring CLooG/ppl [EXTRA] Building CLooG/ppl [EXTRA] Installing CLooG/ppl [INFO ] Installing CLooG/ppl: done in 7.06s (at 03:58) [INFO ] ================================================================= [INFO ] Installing MPC [EXTRA] Configuring MPC [EXTRA] Building MPC [EXTRA] Installing MPC [INFO ] Installing MPC: done in 9.58s (at 04:08) [INFO ] ================================================================= [INFO ] Installing binutils [EXTRA] Configuring binutils [EXTRA] Building binutils [EXTRA] Installing binutils [INFO ] Installing binutils: done in 39.71s (at 04:47) [INFO ] ================================================================= [INFO ] Installing static core C compiler [EXTRA] Configuring static core C compiler [EXTRA] Building static core C compiler [EXTRA] Installing static core C compiler [INFO ] Installing static core C compiler: done in 146.93s (at 07:14) [INFO ] ================================================================= [INFO ] Installing kernel headers [EXTRA] Installing kernel headers [EXTRA] Checking installed headers [INFO ] Installing kernel headers: done in 8.98s (at 07:23) [INFO ] ================================================================= [INFO ] Installing C library headers & start files [EXTRA] Configuring C library [EXTRA] Installing C library headers [EXTRA] Installing C library start files [INFO ] Installing C library headers & start files: done in 45.50s (at 08:09) [INFO ] ================================================================= [INFO ] Installing shared core C compiler [EXTRA] Configuring shared core C compiler [EXTRA] Building shared core C compiler [EXTRA] Installing shared core C compiler [INFO ] Installing shared core C compiler: done in 163.11s (at 10:52) [INFO ] ================================================================= [INFO ] Installing C library [EXTRA] Configuring C library [EXTRA] Building C library [EXTRA] Installing C library [INFO ] Installing C library: done in 483.20s (at 18:55) [INFO ] ================================================================= [INFO ] Installing final compiler [EXTRA] Configuring final compiler [EXTRA] Building final compiler [EXTRA] Installing final compiler [INFO ] Installing final compiler: done in 257.40s (at 23:13) [INFO ] ================================================================= [INFO ] Installing binutils for target [EXTRA] Configuring binutils for target [EXTRA] Building binutils' libraries (libiberty bfd) for target [EXTRA] Installing binutils' libraries (libiberty bfd) for target [INFO ] Installing binutils for target: done in 74.09s (at 24:27) [INFO ] ================================================================= [INFO ] Installing native gdb [EXTRA] Building static target ncurses [EXTRA] Building static target expat [EXTRA] Configuring native gdb [EXTRA] Building native gdb [EXTRA] Installing native gdb [EXTRA] Cleaning up ncurses [INFO ] Installing native gdb: done in 241.59s (at 28:28) [INFO ] ================================================================= [INFO ] Installing gdbserver [EXTRA] Configuring gdbserver [EXTRA] Building gdbserver [EXTRA] Installing gdbserver [INFO ] Installing gdbserver: done in 14.77s (at 28:43) [INFO ] ================================================================= [INFO ] Installing GCC test suite [INFO ] Installing GCC test suite: done in 34.60s (at 29:18) [INFO ] ================================================================= [INFO ] Cleaning-up the toolchain's directory [EXTRA] Installing the populate helper [EXTRA] Installing a cross-ldd helper [EXTRA] Creating toolchain aliases [EXTRA] Removing access to the build system tools [EXTRA] Removing installed documentation [INFO ] Cleaning-up the toolchain's directory: done in 0.79s (at 29:19) [INFO ] Build completed at 20111204.171250 [INFO ] (elapsed: 29:18.74) [INFO ] Finishing installation (may take a few seconds)...
One final word of note: This is a hard-float toolchain and you cannot link any soft-float code to it. You will have to rebuild all of your software with this toolchain and use the following options:
-mfloat-abi=hard -mfpu=vfpv3 -march=armv7-a -mtune=cortex-a8
Otherwise you will get linker errors like this:
Specifically note the "xxxx uses VFP register arguments, yyyy does not" error.
Hi,
After the below log the build is stuck. Please help.
manu@nadham:~/installs/crosstool-ng-1.13.2$ ./ct-ng build.2
[INFO ] Performing some trivial sanity checks
[INFO ] Build started 20120211.014729
[INFO ] Building environment variables
[INFO ] =================================================================
[INFO ] Retrieving needed toolchain components’ tarballs
[00:44] /
-regards
manu
Hi Manu,
At this stage of the build crosstool-ng is downloading all the components required. It will take a long time depending on your internet link. Look at build.log for more information about how it is progressing.