vfs: 'struct file' to VOP_READ

Add 'struct file' to VOP_READ API. This is needed for procfs which
generates file contents at open() time and read() must operate on it,
not the vnode.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
mmu: procfs support

Add procfs_maps() function to core/mmu.cc that returns all the VMAs
formatted for Linux compatible "/proc/<pid>/maps" file.

This will be called by the procfs filesystem.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
proc filesystem

This patch adds a simple Linux compatible procfs filesystem.  It
currently implements a "/proc/self/maps" file which is looked up by
OpenJDK during startup.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
vfs: mount procfs at boot

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>