Specifications

Debugging a Device Driver
11.2 Using the OpenVMS AXP System-Code Debugger
Boot Command
The form of the boot command varies depending on the type of OpenVMS AXP
system you are using. However, all boot commands have the concept of boot flag
and boot devices as well as a way to save the default boot flags and devices. This
section uses syntax from a DEC 3000 Model 400 AXP Workstation in examples.
To use the system-code debugger, you must specify an Ethernet device with
the boot command on the target system. This device will be used by the target
system to communicate with the host debugger. It is currently a restriction that
this device must not be used for anything else (either for booting or network
software such as DECnet, TCP/IP products, and LAT products). Thus, you must
also specify a different device to boot from. For example, the following command
will boot a DEC 3000 Model 400 from the dkb100 disk, and the system-code
debugger will use the esa0 ethernet device.
>>> boot dkb100,esa0
To find out the Ethernet devices available on your system, enter the following
command:
>>> Show Device
In addition to devices, you can also specify flags on the boot command line. Boot
flags are specified as a hex number; each bit of the number represents a true or
false value for a flag. The following flag values are relevant to the system-code
debugger:
• 8000
This new boot flag enables operation of the target kernel. If this boot flag
is not set, not only will it be impossible to use the system-code debugger to
debug the system, but the additional XDELTA commands related to the target
kernel will generate an XDELTA error message. If this flag is set, SYSTEM_
DEBUG is loaded, and the system-code debugger is enabled.
• 0004
This boot flag’s function has not changed. It controls whether the system calls
INI$BRK at the beginning and end of EXEC_INIT. Notice that if the system-
code debugger is the default debugger, the first breakpoint is not as early as
it is for XDELTA. It is delayed until immediately after the PFN database is
set up.
• 0002
This boot flag, which has always controlled whether XDELTA is loaded,
behaves slightly differently when the system-code debugger boot flag is also
set.
If the system-code debugger boot flag is clear, this flag works as it always
has. If the system-code debugger boot flag is set, this flag determines whether
XDELTA or the system-code debugger is the default debugger. If the XDELTA
flag is set, XDELTA will be the default debugger. In this state, the initial
system breakpoints and any calls to INI$BRK trigger XDELTA, and you
must issue an XDELTA command to start using the system-code debugger.
If this flag is clear, the initial breakpoints and calls to INI$BRK go to the
system-code debugger. You cannot use XDELTA if the XDELTA flag is clear.
11–4