Two important things:

1. I used gcc-3.0.4 to create this patch(because that was the only compiler 
available with 64-bit support that could be used on my Debian(sid) system), 
and hence it contains some bits in arch/um/Makefile, which are specific to 
gcc-3.0.4. If you want to use any other compiler with 64-bit support, you 
need to modify that section.

2. Gcc complains about _siginfo_fpu_t and sigcontext structures in files 
/usr/include/bits/sigcontext.h and
/usr/include/asm-sparc64/sigcontext.h, 
although the structures are defined identically in both files. 
Hence, I just added:

#ifndef <macro-name>
#define <macro-name>

around both structures in /usr/include/bits/sigcontext.h. And in
/usr/include/asm-sparc64/sigcontext.h, I added #ifndef <macro-name>, for
both struct's to make sure that only struct's from one of the 2 file's is 
getting included.