Cross-compilation

Many or even most tasks can be implemented using the integrated SDK with the C-like scripting language and the router API functions.

However, if for some reasons you want or have to cross-compile a C application, you will find the different Cross-compilation toolchains on our FTP server. The toolchains consists of a compiler ( GNU Compiler Collection (GCC) version 4.4.5), a assembler and linker ( GNU binutils) and a C standard library ( uClibc version 0.9.31), all built to produce binaries for NetModule Routers.

The following Cross-Compilation toolchains are available:

• PowerPC / NB1600, NB2700, NB2710, NB3700 and NB3710
• ARM / NB1800, NB1810, NB2800, NB3701, NB3711 and NB3800
• ARM / NB1601, NB800

For further introduction to GCC please refer to An Introduction to GCC, chapter 2 and following ones.

Please be ware that NetModule can not support systems with customer extensions.

1. Download and install the corresponding toolchain from above on your Linux x86 PC

wget https://share.netmodule.com/router/public/toolchain/netbox-ppc/toolchain-ppc-4.4.5-x86_64.tar.bz2
tar -xvf toolchain-ppc-4.4.5-x86_64.tar.bz2 -C /opt
export PATH=$PATH:/opt/toolchain-ppc-4.4.5-x86_64/bin

2. Write a program

hello.c

#include<stdio.h>
#include<features.h>
int main()
{
    printf("Hello World\n");
    #ifdef __UCLIBC__
    printf("We are coding against uClibc\n");
    printf("uClibc v%i %i.%i\n",__UCLIBC_MAJOR__, __UCLIBC_MINOR__, __UCLIBC_SUBLEVEL__);
    #endif
    return 0;
}

The Linux man-pages project documents the Linux kernel and C library interfaces that are employed by user-space programs. Section 2 documents the system calls provided by the Linux kernel and section 3 documents the functions provided by the standard C library. Another reference guide for the C standard library can be found here.

3. Compile it

PowerPC:

powerpc-openwrt-linux-gcc -Wall hello.c -o hello

ARM:

arm-openwrt-linux-gcc -Wall hello.c -o hello

4. Copy it to the router (e.g. via SCP) and run it.

This example shows you how to compile a program from source. The program in this example is jq

PowerPC

wget https://github.com/stedolan/jq/releases/download/jq-1.5/jq-1.5.tar.gz
tar -xzf jq-1.5.tar.gz
cd jq-1.5
CC=powerpc-openwrt-linux-gcc ./configure --host=powerpc --disable-maintainer-mode
make

ARM

wget https://github.com/stedolan/jq/releases/download/jq-1.5/jq-1.5.tar.gz
tar -xzf jq-1.5.tar.gz
cd jq-1.5
CC=arm-openwrt-linux-gcc ./configure --host=arm --disable-maintainer-mode
make

Note: Patch required to fix y0, y1, j0 and j1 related build issue on uClibc
Our default uClibc configuration does not have DO_XSI_MATH=y, so it lacks certain math functions. jq generates some wrappers for the libm functions, even for functions that are not actually used by jq. By simply removing those wrappers, we get jq to build on uClibc that have DO_XSI_MATH disabled.

We can now check the file type and we see, that the program has been compiled for PowerPC. Now we can copy jq to NB1600 and run it.

file jq
jq: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1 (SYSV), dynamically linked (uses shared libs), with unknown capability 0x41000000 = 0x13676e75, with unknown capability 0x10000 = 0xb0402, not stripped

For small projects or if you don't have a Linux environement you can also use the very small Virtual Box Image. The image uses Tiny Core Linux (http://tinycorelinux.net/). Please read the startup message carefully. This is only valid for the NB1600, NB2700/2710, NB3700/3710.