ssize_t mdb_get_xdata(const char *name, void *buf, size_t nbytes);
Read the contents of the target external data buffer specified by name into the buffer specified by buf. The size of buf is specified by the nbytes parameter; no more than nbytes will be copied to the caller's buffer. The total number of bytes read will be returned upon success; -1 will be returned upon error. If the caller wants to determine the size of a particular named buffer, buf should be specified as NULL and nbytes should be specified as zero. In this case, mdb_get_xdata() will return the total size of the buffer in bytes but no data will be read. External data buffers provide module writers access to target data that is not otherwise accessible through the module API. The set of named buffers exported by the current target can be viewed using the ::xdata built-in dcmd.