How to cross compile for N2100?

[mwk]

I am interested in learning more about embedded Linux development, and first I would like to learn how to cross compile for N2100.

I know I have get the toolchain, but what's the next step?

Is there anyone who can write up simple howto for people to follow?

Thanks in advance.

[shlime]

Hi mwk,

I've been bashing my head against google with the same question. I'm keen to write some code for my new N2100. It'd be great if someone could do a quick how-to.

I think I'm pretty close. I've got cygwin, and the 3.4.3 gnu-arm cross compiler.

I'm doing:

arm-elf-gcc -march=armv5te test.c

where test.c is simply:

int main(void)
{
return 0;
}

I get an a.out which I then run on my thecus through ssh, and all I get is:

Segmentation fault

I've played with a ton of flags and settings (endian, fpu etc), and I always get the same result.

My best guess is that it's something to do with the fpu/vfp settings on my elf or those of the libraries I'm linking with. If I try and flag the compiler to use hardware fpu, I get linker errors.

If I dump the header of the bzip elf that comes with the N2100 utils module, I get this:

$ arm-elf-readelf -h bzip2
ELF Header:
Magic: 7f 45 4c 46 01 01 01 61 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: ARM
ABI Version: 0
Type: EXEC (Executable file)
Machine: ARM
Version: 0x1
Entry point address: 0x8b1c
Start of program headers: 52 (bytes into file)
Start of section headers: 80392 (bytes into file)
Flags: 0x2, has entry point, GNU EABI
Size of this header: 52 (bytes)
Size of program headers: 32 (bytes)
Number of program headers: 6
Size of section headers: 40 (bytes)
Number of section headers: 25
Section header string table index: 24

The only difference when I dump my elf is that it mentions software FP.

$ arm-elf-readelf -h a.out
ELF Header:
Magic: 7f 45 4c 46 01 01 01 61 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: ARM
ABI Version: 0
Type: EXEC (Executable file)
Machine: ARM
Version: 0x1
Entry point address: 0x8110
Start of program headers: 52 (bytes into file)
Start of section headers: 118332 (bytes into file)
Flags: 0x202, has entry point, GNU EABI, software FP
Size of this header: 52 (bytes)
Size of program headers: 32 (bytes)
Number of program headers: 1
Size of section headers: 40 (bytes)
Number of section headers: 24
Section header string table index: 21

If anyone could get me over this hump and into the land of running code, I'd be happy to write up a how-to for others.

Cheers.

[getmythe]

Setting up a toolchain is not an easy task. You need to start with the same versions of gcc and all the basic libriaries (binutils, libc, ...) as Thecus used. Otherwise your binaries will never be compatible (unless you intend to compile static binaries only).

I would recommend to install Ubuntu and use the existing toolchain from Thecus.

[shlime]

I'll give anything a shot

I've got Ubuntu 7.10 installed. Can you point me to the right tool chain to download? I haven't seen any 'official' tool chain from Thecus. Is it the one on this site?

www.freeside.ch/thecus/

I've extracted it into:

/usr/local/armv5l

but I'm guessing I need to configure some paths or something. If I try and build something it just says there's an installation problem and it can't exec ccl.

Thanks.

[getmythe]

You got the right toolchain.

Let's now add some important environment variables

export TPREFIX=/opt/local
export LINUX=/usr/local/armv5l/3.3.2/armv5l-linux
export TOOLBASE=/usr/local/armv5l/3.3.2/bin/armv5l-linux
export CC=$TOOLBASE-gcc
export CXX=$TOOLBASE-g++
export CPP=$TOOLBASE-cpp
export CXXCPP=$CPP
export AR=$TOOLBASE-ar
export RANLIB=$TOOLBASE-ranlib
export STRIP=$TOOLBASE-strip
export LDFLAGS="-L$TPREFIX/lib -L$LINUX/lib -L$LINUX/usr/lib"
export CFLAGS="-I$TPREFIX/include -I$LINUX/sys-include -I$LINUX/include -I$LINUX/usr/include"
export CPPFLAGS="-I$TPREFIX/include -I$LINUX/sys-include -I$LINUX/include -I$LINUX/usr/include"
export PKG_CONFIG_PATH=$LINUX/lib/pkgconfig

If you want to compile by hand it makes sense have these two as well (not required when using configure)

# export PATH=/usr/local/armv5l/3.3.2/armv5l-linux/bin:$PATH
# export PATH=/usr/local/armv5l/3.3.2/bin:$PATH

... and here is a simple example for you to try out your setup (openvpn)

./configure --target=arm-linux --host=arm-linux --prefix=$TPREFIX \
 --sysconfdir=/etc/openvpn --enable-password-save

have fun
getmythe

[shlime]

Thanks heaps for the help. It feels like I'm close, but still no luck

I configured my .bashrc with the exports you listed. At first it couldn't find cc1, so I added:

export PATH=/usr/local/armv5l/3.3.2/lib/gcc-lib/armv5l-linux/3.3.2:$PATH

and that seemed to fix it. I can now compile and assemble, but it doesn't link. I run 'armv5l-linux-gcc test.c' and I get :

...arm5vl-linux/bin/ld: cannot find libc.so.6

I'm guessing it's trying to find some specific version of the standard libraries or something. A quick search reveals there's no libc.so.6 in the toolchain zip, so I'm not sure what's going on.

I tried running the ./configure line you gave me, but it just says unknown command. Is that part of some standard build package I need to get for ubuntu or something?

Anyhow, thanks again for your time!

[getmythe]

Ok, here are the complete instructions on how to compile the latest openvpn sources from scratch.

• download openvpn.net/release/openvpn-2.0.9.tar.gz
  
• configure openvpn (see prev post, configure code statement)
  
• compile by calling make
  
• congratulations, you're done!
  

Configure is a script provided with almost every unix source package. It is generated specifically for that piece of code by the maintainer of the software. It checks that your setup is compatible with the provided sources and generates a makefile which matches your compile setup and your particular linux version.

getmythe