How come a 32 bit kernel can run a 64 bit binary?

Question

On my OS X box, the kernel is a 32 bit binary and yet it can run a 64 bit binary. How does this work?

cristi:~ diciu$ file ./a.out
./a.out: Mach-O 64-bit executable x         


        

Answer 1

For the kernel to be 64-bit would only bring the effective advantage that kernel extensions (i.e., typically drivers) could be 64-bit. In fact, you'd need to have either all 64-bit kernel extensions, or (as is the case now) all 32-bit ones; they need to be native to the architecture of the running kernel.