runtime addresses of functions in shared objects

runtime addresses of functions in shared objects

[Collins, Tom]

Hello...

Is there a way to determine the runtime addresses of functions that
reside in shared object files?

I am writing a profiler for an application in which I supply the mcount,
mstartup, and moncontrol functions.  The mcount function obtains the
callers return address from the stack.  I have a small multi-threaded
(cloned) application that I have tested this on, and it works fine.

What I am wondering is what to do with shared objects.  Do they not 
undergo relocation when they are loaded?  If so, how do I find out
what those relocated addresses are for those functions in the shared
object?

Thanks

Re: runtime addresses of functions in shared objects

[Ingo Krabbe]

On Tue, 3 Jul 2001, Collins, Tom wrote:

> Hello...
>
> Is there a way to determine the runtime addresses of functions that
> reside in shared object files?
>
> I am writing a profiler for an application in which I supply the mcount,
> mstartup, and moncontrol functions.  The mcount function obtains the
> callers return address from the stack.  I have a small multi-threaded
> (cloned) application that I have tested this on, and it works fine.
>
> What I am wondering is what to do with shared objects.  Do they not
> undergo relocation when they are loaded?  If so, how do I find out
> what those relocated addresses are for those functions in the shared
> object?
>
> Thanks
>
You should look at dlopen of libdl.so (found in header dlfcn.h). The
dlopen functions can open these shared object files and with dlsym you can
finally get the runtime address of a symbol which you can use in your
program then. There is a Manual Page 'man dlopen' which is enough to
create a small example. It's easy, really !

CU INGO