The code responsible for mapping the kernel sections worked under the
assumption that the linker would align all sections on a page boundary.
To figure out the page extents for a particular section, the
implementation would round the section VMA down to the nearest page and
add to that the section length rounded up to the nearest page size.
However, some sections (e.g. noptrbss) use 32 byte alignment. Depending
on the section length, the original implementation could in some cases
skip mapping of the last page in the section which would cause a page
fault when its contents were accessed.
The fix for this issue is quite simple: calculate the end page by
rounding up (section start addr + section length) to the next page.
vmm.IdentityMapRegion can be used by device drivers that want to
establish an identity mapping for a contiguous physical memory block in
order to access some hardware or table.
By setting up pwd as a Go workspace, we can trim import paths from
something like "github.com/achilleasa/gopher-os/kernel" to just
"kernel".
These changes make forking easier and also allows us to move the code to
a different git hosting provider without having to rewrite the imports.
