4.3. Build Variables

Setting Host and Target

During the building of the cross-compile tools, you will need to set a few variables that will be dependent on your particular needs. You will need to select the target triplet for the target architecture, the CPU architecture, the CPU floating point hardware availability, and (if available) the type of floating point hardware. If you do not know what values can be chosen for each of these, you can use the tables as a reference.

If your processor is an ARM9, good choices include: triplet of arm-linux-musleabi, ARM arch of armv5t, and float of soft. ARM9 processors do not usually have hardware floating point abilities. If your processor is a Cortex-A series, which often have hardware floating point capability, good choices include: triplet of arm-linux-musleabihf, ARM arch of armv7-a, float of hard, and fpu of vfpv3-d16.

If your target CPU has hardware floating point support (not all ARM CPUs do), then set the following CLFS_FLOAT variable to either "hard" or "softfp". Use "softfp" if you need to integrate binaries compiled with "soft". Use "hard" if you don't. If your target CPU does not have hard floating point support, set the following CLFS_FLOAT vairable to "soft".

export CLFS_FLOAT="[hard, softfp, or soft]"

If you chose either "hard" or "softfp" for CLFS_FLOAT, you now need to set which floating point hardware is actually included (see table below) with your ARM CPU:

export CLFS_FPU="[fpu version]"

Table 4.1. ARM Hard Floating Point Versions

fpa fpe2 fpe3 maverick
vfp vfpv3 vfpv3-fp16 vfpv3-d16
vfpv3-d16-fp16 vfpv3xd vfpv3xd-fp16 neon
neon-fp16 vfpv4 vfpv4-d16 fpv4-sp-d16

Then, set the host and target triplets:

export CLFS_HOST=$(echo ${MACHTYPE} | sed "s/-[^-]*/-cross/")
export CLFS_TARGET="[target triplet]"

Table 4.2. Target Triplets

Float Type Triplet
soft or softfp arm-linux-musleabi
hard arm-linux-musleabihf

Now set the architecture of the CPU:

export CLFS_ARCH=arm

Choose the ARM architecture (see table below):

export CLFS_ARM_ARCH="[architecture]"

Table 4.3. ARM Archiecture Choices

armv4t armv5 armv5t armv5te
armv6 armv6j armv6t2 armv6z
armv6zk armv6-m armv7 armv7-a
armv7-r armv7-m    

Now we will add this to ~/.bashrc, just in case you have to exit and restart building later:

echo export CLFS_HOST=\""${CLFS_HOST}\"" >> ~/.bashrc
echo export CLFS_TARGET=\""${CLFS_TARGET}\"" >> ~/.bashrc
echo export CLFS_ARCH=\""${CLFS_ARCH}\"" >> ~/.bashrc
echo export CLFS_ARM_ARCH=\""${CLFS_ARM_ARCH}\"" >> ~/.bashrc
echo export CLFS_FLOAT=\""${CLFS_FLOAT}\"" >> ~/.bashrc
echo export CLFS_FPU=\""${CLFS_FPU}\"" >> ~/.bashrc