The runtime linker performs many operations including the mapping of objects into memory and the binding of symbols. Debugging programs often need to access information that describes these runtime linker operations as part of analyzing an application. These debugging programs run as a separate process from the application the debugger is analyzing.
This section describes the rtld-debugger interface for monitoring and modifying a dynamically linked application from another process. The architecture of this interface follows the model used in libc_db(3LIB).
When using the rtld-debugger interface, at least two processes are involved.
One or more target processes. The target processes must be dynamically linked and use the runtime linker /usr/lib/ld.so.1 for 32–bit processes, or /usr/lib/64/ld.so.1 for 64–bit processes.
A controlling process links with the rtld-debugger interface library and uses the interface to inspect the dynamic aspects of the target processes. A 64–bit controlling process can debug both 64–bit targets and 32–bit targets. However, a 32–bit controlling process is limited to 32–bit targets.
The most anticipated use of the rtld-debugger interface is when the controlling process is a debugger and its target is a dynamic executable.
The rtld-debugger interface enables the following activities with a target process.
Initial rendezvous with the runtime linker.
Notification of the loading and unloading of dynamic objects.
Retrieval of information regarding any loaded objects.
Stepping over procedure linkage table entries.
Enabling object padding.