1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
|
Relocatable Dynamic Object File Format V2
%BRDOFF is a relocatable object file format%b whose design goals were
mainly to keep it simple, so that an RDOFF object can be loaded and
executed by a very small piece of code (primarily so that it can be
used by the microkernel of an operating system to store system
modules, which can then go on to load and execute more complex object
files, eg ELF, if so desired), yet still be able to be cope with
everything required by the operating system; linkage of multiple
modules together (possibly with automatic loading of new libraries
that are referred to by the object) at load time, allowing static or
dynamic linking as required by the application.
RDOFF was designed initially to test the object-file production
interface to NASM. It soon became apparent that it could be enhanced
for use in serious applications due to its simplicity; code to load
and execute an RDOFF object module is very simple. It also contains
enhancements to allow it to be linked with a dynamic link library at
either run- or load- time, depending on how complex you wish to make
your loader.
The overall format has changed somewhat since version 1, in order to
make RDOFF more flexible. After the file type identifier (which has
been changed to 'RDOFF2', obviously), there is now a 4 byte integer
describing the length of the object module. This allows multiple
objects to be concatenated, while the loader can easily build an
index of the locations of each object. This isn't as pointless as it
sounds; I'm using RDOFF in a microkernel operating system, and this
is the ideal way of loading multiple driver modules at boot time.
|
