There are actually two floating point emulators available for ARM Linux. A version of the Acorn emulator was ported to ARM Linux by Russell King. He has a very specific licence which allows him to distribute this emulator as a module with most of the symbols stripped out from his web site. It is well established, in its third release. It is highly optimized, and written in ARM assembly language.
The licence restrictions on the Acorn FPE proved problematic for the NetWinder. It looked like it would be expensive to licence the emulator from Acorn. The ARM SDT route was also expensive. Neither route would satisfy one of our goals of a completely open source operating system for the NetWinder. Writing an emulator from scratch, was not really an option given our ship dates. After all, writing routines to implement the IEEE floating point algorithms in software is not what I would call a trivial short term programming exercise. The implementation as a kernel module also caused support headaches. If the module failed to load any program linked with the C libaries failed to run. Thus the shell would crash and the system would not run. (The __set_fpucw routine called from the C library startup code issues a WFS and RFS instruction).
It is possible to logically divide the construction of the emulator into two logically distinct parts; a library of IEEE floating point algorithms, and code to emulate the FPA11 floating point hardware. As luck would have it Phil Blundell had brought to my attention a free library of code implementing IEEE floating point algorithms. SoftFloat is a complete IEEE 754 floating point library written by John Hauser. Neil Carson had ported this software to run on the ARM platform, and Phil had modified it to create a library for use with the compiler when the -msoft-float compiler flag was used. With SoftFloat in hand, it was possible to concentrate on building just the emulation code for the floating point hardware. Thus the NWFPE was born.