Force specified function to be linked to a specified lib when compiling/linking

[Yubin Ruan <ablacktshirt at gmail dot com>]

Hi,

I am wondering whether it is possible to force the linker to use some
specified function to link to when compiling/linking.

I am using the LD_PRELOAD environment variable to hook some specified
functions but I am not so familiar with linker so there are some
troubles. I am hooking the standard `open' system call to add some
functionalities, so that when users use the `open' system call, I can
collect some data. Basically I am doing something like this:

    int open(int fd, int flags, ...) {   /* (1) */
        ...
        /* add some functionalities here */
        ...

        return open(...);   /* (2) return the original open function call */
    }

Obviously, this cannot work, as it would call into a infinite loop...
So I am wondering whether I can force the linker to link some function
to some specified dynamic library so that it would not cause infinite
loop. In the example above, it would be perfect for the `open()'
system call at (2) to be linked to the standard library, rather than
the one that I hook.

As for now, because I set the LD_PRELOAD as:

    export LD_PRELOAD=/path/to/my_open.so

whenever a program that have a `open()' function inside is loaded, the
dynamic linker would link that `open()' to my ``my_open.so''. And that
is the same for my ``open'': when the linker try to link the `open()'
at (2), it would also try to link that to my `open()' at (1),
resulting in a infinite loop.

Any idea?

--
Yubin