VDL: Virtualizing Dynamic Linker/Loader
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1) What is this ?
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This is an ELF dynamic linker/loader. Its purpose is
to be a binary-compatible replacement of /lib/ld-linux.so.2
on a large variety of linux distributions for i386/x86-64
systems. Support for other hardware platforms is not planned
but non-intrusive patches are welcome :)
2) What is its purpose ?
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I need more features from the dynamic loader than what is
provided by the default glibc loader. I could have tried to
hack the glibc loader but since I did not know enough about
the details of how a loader work, and given the horrid
complexity/lack of documentation of the glibc loader, it
seemed easier to implement a new loader with the features I
needed.
Extra features:
- unlimited number of namespaces (lmid) with dlmopen (DL_LM_NEWID)
- dl_lmid_new
- dl_lmid_delete
- dl_lmid_add_callback
- dl_lmid_add_lib_remap
- dl_lmid_add_symbol_remap
API documentation for these new functions in doc/dl-lmid.txt
3) What is its status ?
-----------------------
Right now, this loader can load pretty complex programs, including
things like evolution and firefox. Supported systems are:
- fc11-64
- fc11-32
- fc12-64
- fc12-32
- ubuntu-0804-32
- ubuntu-0804-64
- ubuntu-0910-32
- ubuntu-0910-64
Other systems might work or not. If you find one which works,
please, let me know. If it does not work, you can ask me to
try to make it work.
4) How do I use it ?
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Obviously, you need to build it first. To do this, you need
some standard devel packages.
On fedora: yum install gcc gcc-c++ make mercurial glibc-debuginfo
On ubuntu: apt-get install gcc g++ make mercurial libc6-dbg
If you have selinux enabled, you will most likely have to run a
command such as this:
chcon -t textrel_shlib_t '/lib/libc-2.10.2.so'
Building the code:
make vdl-config.h
make
make test
If everything is allright, you should see a set of PASS
statements and you should be able to start using this loader
by:
a. elfedit your-binary /path/to/ldso
b. put /path/to/libvdl.so in LD_LIBRARY_PATH
c. run your-binary
LD_LOG=function is a nice debugging tool.
LD_LOG=symbol-ok shows the list of symbols successfully resolved
LD_LOG=symbol-fail shows the list of symbols unsuccessfully resolved