The dynamic loader will now mark RELRO segments read-only after
performing relocations. This is pretty cool!
Note that this only applies to main executables so far,.
RELRO support for shared libraries will require some reorganizing
of the dynamic loader.
For a data segment that starts at a non-zero offset into a 4KB page and
crosses a 4KB page boundary, we were failing to pad the VM allocation,
which would cause the memcpy() to fail.
Make sure we round the segment bases down, and segment ends up, and the
issue goes away.
load_from_image() becomes map() and link(). This allows us to map
an object before mapping its dependencies.
This solves an issue where fixed-position executables (like GCC)
would clash with the ASLR placement of their own shared libraries.
Refactor DynamicLoader construction with a try_create() helper so that
we can call mmap() before making a loader. This way the loader doesn't
need to have an "mmap failed" state.
This patch also takes care of determining the ELF file size in
try_create() instead of expecting callers to provide it.
