Unix Programming - How to disable a DLLs init() when using dlopen() ?

Author

How to disable a DLLs init() when using dlopen() ?

Adrian B.

2004-07-29, 7:52 am

I have a shared lib I'm opening with dlopen() but do not have access
to its source code. It automatically executes an init fn on loading
(and fini() in exiting) which do stuff I want to disable. Is there
any way to do this programatically?

Thanks
AB

Måns Rullgård

2004-07-29, 7:52 am

borg@swirve.com (Adrian B.) writes:

> I have a shared lib I'm opening with dlopen() but do not have access
> to its source code. It automatically executes an init fn on loading
> (and fini() in exiting) which do stuff I want to disable. Is there
> any way to do this programatically?

You could use objcopy to rename those symbols to something harmless.

--
Måns Rullgård
mru@kth.se

Paul Pluzhnikov

2004-07-30, 2:48 am

Måns Rullgård <mru@kth.se> writes:

> borg@swirve.com (Adrian B.) writes:
>

No, not really.
[vbcol=seagreen]
> You could use objcopy to rename those symbols to something harmless.

At least on ELF systems, these symbols are not referenced by the
dynamic loader "by name"; rather their address is recorded in the
the PT_DYNAMIC header as DT_INIT and DT_FINI at link time.

Renaming the _init/_fini will not do the OP any good.

OTOH, binary-editing the .dynamic section and setting DT_INIT/DT_FINI
to some other "harmless" address should do the trick.

Cheers,
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