Rump Namespaces

Rump uses the concept of Namespacing to segregate system calls. Now the C Programming language does not incorporate the concept of Namespaces for function calls, something that got introduced with C++. Historically when the C language was designed, this was not a necessitiy at the time and introducing this feature into later revisions of C might actually have broken backward compatibility.

Which brings us to the original question how did the author of Rumpkernel (pooka@) manage to get namespacing into the existing NetBSD code base to segregate system / kernel calls that would be directed to stuff within the Rump vs the calls that would go into the Host Operating system.

He clevery used objcopy to create a new namespace by renaming the existing one after the creation of the libraries that rump uses. Anything that is not named as rump or RUMP is prefixed with rumpns_ which creates an isolated namespace where all calls are redirected to the Rump kernel system rather than the host kernel.

An small excerpt from Makefile.rump that shows how the renaming of namespace is done.

for renameobj in ${RUMP_SYMREN:U${.ALLSRC:C/(${RUMPOBJ_NORENAME:ts|})//g}}; do \
        ${NM} -go $${renameobj} | ${TOOL_AWK} ' \
		    $$NF!~/^'${_PQ}'(rump|RUMP|__|_GLOBAL_OFFSET_TABLE'${_SYMQUIRK}'${RUMP_SYM_NORENAME:D|${RUMP_SYM_NORENAME}})/ \
			  {s=$$NF;sub(/^'${_PQ}'/, "&rumpns_", s); print $$NF, s}'\
			| sort | uniq  > renametab.$${renameobj}; \
		${OBJCOPY} --preserve-dates --redefine-syms \
			renametab.$${renameobj} $${renameobj}; \
        rm -f renametab.$${renameobj}; \
done

So that being said, I still needed to figure out how to use this implementation to our advantage in uvm testing, what all should I rename, should I bring in the uvm_physseg implementation into Rump or just include the files directly and allow the compiler to do it’s job.