12 | | * Possible cause of the problem: Fabrício could be running rdbmon debug monitor on his board, using it to download and start applications. rdbmon is an application on its own, and needs to insert its trap vectors into the rtems applications trap table. This is done by starting the application in user mode. The first priviledged instruction that occurs is a write to %tbr (trap base register). This instruction will trap and control is transfered to rdbmon. The monitor can read out the value of the new %tbr, insert its trap entries there, write the scaler value in 0x7e of the new |
13 | | trap table, and re-start the application is supervisor mode. What can not be done (and this is also mentioned in the |
14 | | leccs/rdbmon manual) is to single step through this procedure. What can also not be done is to use a custom loader that does not write 0x7e, or custom start up code that re-allocates the trap table. |
| 12 | * Possible cause of the problem: Fabrício could be running rdbmon debug monitor on his board, using it to download and start applications. rdbmon is an application on its own, and needs to insert its trap vectors into the rtems applications trap table. This is done by starting the application in user mode. The first priviledged instruction that occurs is a write to %tbr (trap base register). This instruction will trap and control is transfered to rdbmon. The monitor can read out the value of the new %tbr, insert its trap entries there, write the scaler value in 0x7e of the new trap table, and re-start the application is supervisor mode. What can not be done (and this is also mentioned in the leccs/rdbmon manual) is to single step through this procedure. What can also not be done is to use a custom loader that does not write 0x7e, or custom start up code that re-allocates the trap table. |