Scanning Loadable Objects

Obtaining information for each object maintained on the runtime linkers link-map (see "Establishing a Name-space") is achieved using the following structure (defined in rtld_db.h):

typedef struct rd_loadobj {
        psaddr_t        rl_nameaddr;
        unsigned        rl_flags;
        psaddr_t        rl_base;
        psaddr_t        rl_data_base;
        unsigned        rl_lmident;
        psaddr_t        rl_refnameaddr;
        psaddr_t        rl_plt_base;
        unsigned        rl_plt_size;
        psaddr_t        rl_bend;
        psaddr_t        rl_padstart;
        psaddr_t        rl_padend;
} rd_loadobj_t;

Notice that all addresses given in this structure, including string pointers, are addresses in the target process and not in the address space of the controlling process itself:

rl_nameaddr

Pointer to a string which contains the name of the dynamic object.

rl_flags

Reserved for future use.

rl_base

Base address of dynamic object.

rl_data_base

Base address of data segment of dynamic object.

rl_lmident

The link-map identifier (see "Establishing a Name-space").

rl_refnameaddr

If the dynamic object is a filter (see "Shared Objects as Filters"), then this points to the name of the filtee(s).

rl_plt_base, rl_plt_size

These elements are present for backward compatibility and are currently unused.

rl_bend

End address of object (text + data + bss).

rl_padstart

Base address of padding before dynamic object (refer to "Dynamic Object Padding").

rl_padend

Base address of padding after dynamic object (refer to "Dynamic Object Padding").

The following routine uses this object data structure to access information from the runtime linkers link-map lists:

typedef int rl_iter_f(const rd_loadobj_t *, void *);
 
rd_err_e rd_loadobj_iter(rd_agent_t * rap, rl_iter_f * cb,
        void * clnt_data);

rd_loadobj_iter()

This function iterates over all dynamic objects currently loaded in the target process. On each iteration the imported function specified by cb is called. clnt_data can be used to pass data to the cb call. Information about each object is returned via a pointer to a volatile (stack allocated) rd_loadobj_t structure.

Return codes from the cb routine are examined by rd_loadobj_iter() and have the following meaning:

• 1 -- continue processing link-maps.

• 0 -- stop processing link-maps and return control to the controlling process.

rd_loadobj_iter() returns RD_OK on success. A return of RD_NOMAPS indicates the runtime linker has not yet loaded the initial link-maps.