It's already loaded by PT_LOAD, we're only overwriting that page.

(Strictly speaking we should read the file instead of mapping it, since it
can be outside the loaded segment).

avoid conflicts

'program' will be used for cross-object linking

We need the headers so we can provide the symbols to loaded libraries.
This means we cannot use objcopy to munge the binary format to elf32-i386,
as the loader doesn't understand this format.

Instead, add a separate 32-bit only stage (in elf32-i386 format) that loads
the 64-bit image into memory as its payload.  This keeps multiboot happy and
leave our headers alone.

Used to encapsulate an already-loaded image, for providing symbols to later
objects.

Change the starting program counter to 0x201000 instead of 0; this allows the
ELF header to be present in the loaded image, and used for linking.

elf_object will be used where we have an elf image, but no file.
This corresponds to the core image and libc functions.

We still do not look up symbols completely, since shared libraries are not
provided yet.

These sections have memsz > filesz.  This means we need separate
map_file() and file_anon() with caller-specified addresses.

0x20000 will overflow into the 640k hole