HP OpenVMS Delta/XDelta Debugger Manual
This manual describes the OpenVMS DELTA and XDELTA debuggers. OpenVMS
DELTA is used to debug programs that run in privileged processor mode
at interrupt priority level 0. OpenVMS XDELTA is used to debug system
software that runs at an elevated interrupt priority level.
This manual supersedes the HP OpenVMS Delta/XDelta Debugger Manual, OpenVMS I64 Version 8.2
OpenVMS Alpha Version 7.3
OpenVMS VAX Version 7.3
OpenVMS I64 Version 8.3 OpenVMS Alpha Version 8.3
Hewlett-Packard Company Palo Alto, California
© Copyright 2006 Hewlett-Packard Development Company, L.P.
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The information contained herein is subject to change without notice.
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Intel and Itanium are trademarks or registered trademarks of Intel
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Printed in the US.
The HP OpenVMS documentation set is available on CD-ROM.
This manual is written for programmers who debug system code for device
drivers and other images that execute in privileged processor-access
modes or at an elevated interrupt priority level (IPL).
This manual consists of the following chapters and appendixes:
- Chapter 1 provides an overview and descriptions for the DELTA
and XDELTA Debuggers and breakpoints.
- Chapter 2 describes the DELTA and XDELTA symbols.
- Chapter 3 describes how to debug programs.
- Chapter 4 describes the DELTA and XDELTA commands.
- Appendix A describes an OpenVMS I64 debugging session using DELTA.
- Appendix B describes an OpenVMS Alpha debugging session using
- Appendix C describes an OpenVMS VAX debugging session using DELTA.
This manual refers to several documents that contain the primary
descriptions of topics discussed in this manual. The following table
lists the topics and those documents.
Accessing OpenVMS VAX through a lower priority interrupt level
HP OpenVMS System Manager's Manual
Boot command qualifiers for Volume Shadowing
HP Volume Shadowing for OpenVMS
Device name parameters
HP OpenVMS System Manager's Manual
IPRs for OpenVMS Alpha
PALcode opcodes for OpenVMS Alpha
Alpha Architecture Reference Manual
Intel® Itanium® hardware architecture and environment
Intel® IA-64 Architecture Software Developer's Manual Volume 1:
IA-64 Application Architecture
Intel® IA-64 Architecture Software Developer's Manual Volume 2:
IA-64 System Architecture
For additional information about HP OpenVMS products and services,
visit the following World Wide Web address:
HP welcomes your comments on this manual. Please send comments to
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OSSG Documentation Group, ZKO3-4/U08
110 Spit Brook Rd.
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How to Order Additional Documentation
For information about how to order additional documentation, visit the
following World Wide Web address:
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Abbreviation representing "HP OpenVMS for Integrity servers".
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Invoking, Exiting, and Setting Breakpoints
This chapter presents an overview of the DELTA and XDELTA debuggers,
and provides the following information:
- Privileges required for running DELTA
- Guidelines for using XDELTA
- Invoking and terminating DELTA and XDELTA debugging sessions on
- Booting XDELTA, requesting interrupts, and accessing initial
breakpoints on OpenVMS systems
1.1 Overview of the DELTA and XDELTA Debuggers
The DELTA and XDELTA debuggers are used to monitor the execution of
user programs and the OpenVMS operating system. They use the same
commands and the same expressions, but they differ in how they operate.
DELTA operates as an exception handler in a process context. XDELTA is
invoked directly from the hardware SCB vector in a system context.
Use DELTA to debug process-context programs that execute at interrupt
priority level (IPL) 0 in any processor mode. You cannot use DELTA to
debug code that executes at an elevated IPL. To debug with DELTA,
invoke it from within your process by specifying it as the debugger (as
opposed to the symbolic debugger).
Use XDELTA to debug system software executing in any processor mode or
at any IPL level. Because XDELTA is not process specific, it is not
invoked from a process. To debug with XDELTA, you must boot the
processor with commands to include XDELTA in memory. XDELTA's existence
terminates when you reboot the processor without XDELTA.
1.2 Privileges Required for Running DELTA
No privileges are required to run DELTA to debug a program that runs in
user mode. To debug a program that runs in other processor-access
modes, the process in which you run the program must have the necessary
To use the ;M command, your process must have change-mode-to-kernel
(CMKRNL) privilege. The ;M command sets all processes writable.
To use the ;L command (List All Loaded Executive Modules), you must
have change-mode-to-executive (CMEXEC) privilege.
1.3 Guidelines for Using XDELTA
Because XDELTA is not process specific, privileges are not required.
When using XDELTA, you must use the console terminal. You should run
XDELTA only on a standalone system because all breakpoints are handled
at IPL 31.
You cannot redirect output from XDELTA. To determine if your system
maintains a log file, check your hardware manual. You can produce a log
of console sessions by connecting the console serial port of the system
that will boot with XDELTA to the serial port of a LAT server. Then,
from another system, use the command SET HOST/LAT/LOG to that LAT port.
1.4 Restrictions for XDELTA on OpenVMS I64 Systems
The following Intel® Itanium® hardware registers are not
supported by XDELTA on OpenVMS I64 systems:
- Debug Data Break Registers
- Debug Instruction Break Registers
- Region Registers
- Protection Key Registers
- Instruction Translation Registers
- Data Translation Registers
- Device Interrupt Control Register
1.5 Invoking DELTA
To invoke DELTA, perform the following steps after assembling (or
compiling) and linking your program:
- Define DELTA as the default debugger instead of the symbolic
debugger with the following command:
$ DEFINE LIB$DEBUG SYS$LIBRARY:DELTA
- Use the following RUN command to execute your program:
When DELTA begins execution, it displays its name and the first
executable instruction in the program with which it is linked. It
displays the address of that instruction, a separator---an exclamation
point (!) on I64 and Alpha, and a slash (/) on VAX---and the
instruction and its operands.
On I64, the name and starting address are displayed as follows:
HP OpenVMS Industry Standard 64 DELTA Debugger
Brk 0 at address
address! instruction operands
On Alpha, the name and starting address are displayed as follows:
OpenVMS Alpha DELTA Debugger
Brk 0 at address
address! instruction operands
On VAX, the name, current version number, and address are displayed as
DELTA Version 5.5
DELTA is then ready for your commands.
You can redirect output from a DELTA debugging session by assigning
DBG$DELTA to the I/O device.
The image activator on OpenVMS Alpha systems automatically activates
SYS$SHARE:SYS$SSISHR.EXE when an image is debugged using the RUN/DEBUG
command or is linked using the /DEBUG qualifier. The presence of this
image should not alter your program's correctness, but if your program
is sensitive to virtual address layout or if for some reason
SYS$SHARE:SYS$SSISHR.EXE is not installed properly on your system, you
may want to bypass its automatic activation.
To keep the image activator from activating SYS$SHARE:SYS$SSISHR.EXE
for you, define the logical name SSI$AUTO_ACTIVATE to be "OFF" before
running the program to be debugged with DELTA.
1.6 Exiting from DELTA
To exit from DELTA, type EXIT and press the Return key. When you are in
user mode, you exit DELTA and your process remains. When you are in a
privileged access mode, your process can be deleted.
1.7 Invoking XDELTA
To invoke XDELTA, perform the following steps:
- Boot the system using a console command or a command procedure that
- On VAX, an initial XDELTA breakpoint is taken so that you can set
additional breakpoints or examine and change locations in memory.
XDELTA displays the following breakpoint message:
1 BRK at address
Never clear breakpoint 1 from any code being debugged in XDELTA. If you
accidentally clear breakpoint 1 and no other breakpoints are set, you
cannot use XDELTA until you reboot again with XDELTA.
On I64 and Alpha, two initial XDELTA breakpoints are taken so that
you can set additional breakpoints or examine and change locations in
memory. XDELTA displays the following message for the first breakpoint:
BRK 0 at address
- On all processors, proceed from the initial breakpoint, using the
On VAX, the procedure for booting the system with XDELTA differs,
depending on the model of your system. Each procedure uses commands
that include XDELTA in memory and cause the execution of a breakpoint
in OpenVMS initialization routines. Execution of the breakpoint
instruction transfers program control to a fault handler located in
Some boot procedures require the use of the /R5 qualifier with the boot
command. The /R5 qualifier enters a value for a flag that controls the
way XDELTA is loaded. The flag is a 32-bit hexadecimal integer loaded
into R5 as input to VMB.EXE, the primary boot program. For a
description of the valid values for this flag, see Table 1-1.
When you deposit a boot command qualifier value in R5, make sure that
any other values you would normally deposit are included. For example,
if you were depositing the number of the system root directory from
which you were booting and an XDELTA value, R5 would contain both
For directions for booting XDELTA on VAX, see the OpenVMS VAX
supplement specific to your computer.
On Alpha, the procedure for booting all Alpha systems with XDELTA is
the same. For one example of how to boot XDELTA, use the boot command
On I64, the procedure for booting with XDELTA is the same. For an
example of how to boot XDELTA, use the boot command as follows:
fs0:\efi\vms\> vms_loader -fl 0,6
On I64 and Alpha, the flag for specifying boot qualifiers is a 64-bit
integer that is passed directly as input to the primary boot program;
IPB.EXE on I64 and APB.EXE on Alpha. For a description of the valid
values for this flag, see Table 1-1.
Table 1-1 Boot Command Qualifier Values
Normal, nonstop boot (default)
Stop in SYSBOOT
Include XDELTA, but do not take the initial breakpoint
Stop in SYSBOOT, include XDELTA, but do not take the initial breakpoint
Include XDELTA, and take the initial breakpoint
Include XDELTA, stop in SYSBOOT, and take the initial breakpoint at
1.8 Requesting an Interrupt
If you set the boot control flag to 6, XDELTA will stop at an initial
breakpoint during the system boot process. You can then set other
breakpoints or examine locations in memory.
Your program can also call the routine INI$BRK, which in turn executes
the first XDELTA breakpoint. For the breakpoint procedure, see
Once loaded into memory, XDELTA can also be invoked at any time from
the console by requesting a software interrupt. For example, you might
need to use a software interrupt to enter XDELTA if your program is in
an infinite loop or no INI$BRK call had been made.
On VAX, INI$BRK is defined as XDELTA's breakpoint 1.
On VAX, never clear breakpoint 1 from any code being debugged in
XDELTA. If you accidentally clear breakpoint 1 and no other breakpoints
are set, you cannot use XDELTA again until you reboot with XDELTA.
On I64 and Alpha, INI$BRK is defined as XDELTA's breakpoint 0. It is
not possible to clear breakpoint 0 from any code being debugged in