Interaction With exec
When a controlled user process performs a successful exec(2), the behavior of the
debugger is controlled by the ::set -o follow_exec_mode option, as described in Summary of Command-line Options. If
the debugger and victim process have the same data model, then the stop
and follow modes determine whether MDB automatically continues the target or returns to
the debugger prompt following the exec. If the debugger and victim process have a
different data model, then the follow behavior causes MDB to automatically re-exec the
MDB binary with the appropriate data model and re-attach to the process, still
stopped on return from the exec. Not all debugger state is
preserved across this re-exec.
If a 32-bit victim process execs a 64-bit program, then stop will return
to the command prompt, but the debugger will no longer be able to
examine the process because it is now using the 64-bit data model. To
resume debugging, execute the ::release -a dcmd, quit MDB, and then execute mdb -p pid
to re-attach the 64-bit debugger to the process.
If a 64-bit victim process execs a 32-bit program, then stop will return
to the command prompt, but the debugger will only provide limited capabilities for
examining the new process. All built-in dcmds will work as advertised, but
loadable dcmds will not since they do not perform data model conversion of
structures. The user should release and reattach the debugger to the
process as described above in order to restore full debugging capabilities.