Tornado Reference : Tornado Utilities
xsym - extract the symbol table from a BSD a.out object module
xsym < objMod > symTbl
This tool reads an object module (UNIX BSD 4.3 a.out format) from standard input, and writes an object module to standard output. The output module contains only the symbol table, with no code, but is otherwise a normal, executable object module.
This tool is used to generate the VxWorks symbol table, vxWorks.sym.
a_out.h - UNIX BSD 4.3 object module header file
xsym, makeSymTbl, UNIX BSD 4.3 a.out documentation