HP OpenVMS Systems Documentation

Order Number: AA--PWCAD--TE

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 programs that run at an elevated interrupt priority level.

Revision/Update Information: This manual supersedes the OpenVMS Delta/XDelta Debugger Manual, OpenVMS VAX Version 7.1
OpenVMS AXP Version 7.1.

Software Version: OpenVMS Alpha Version 7.3 OpenVMS VAX Version 7.3

Compaq Computer Corporation Houston, Texas

© 2001 Compaq Computer Corporation

Compaq, VAX, VMS, and the Compaq logo Registered in U.S. Patent and Trademark Office.

OpenVMS is a trademark of Compaq Information Technologies Group, L.P. in the United States and Other Countries.

All other product names mentioned herein may be the trademarks or registered trademarks of their respective companies.

Confidential computer software. Valid license from Compaq required for possession, use, or copying. Consistent with FAR 12.211 and 12.212, Commercial Computer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government under vendor's standard commercial license.

Compaq shall not be liable for technical or editorial errors or omissions contained herein. The information in this document is provided "as is" without warranty of any kind and is subject to change without notice. The warranties for Compaq products are set forth in the express limited warranty statements accompanying such products. Nothing herein should be construed as constituting an additional warranty.

ZK4540

The Compaq OpenVMS documentation set is available on CD-ROM.

Intended Audience

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).

Document Structure

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 VAX debugging session using DELTA.
• Appendix B describes an OpenVMS Alpha debugging session using DELTA.

Related Documents

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.

For additional information about Compaq OpenVMS products and services, access the following World Wide Web address:

http://www.openvms.compaq.com/

Reader's Comments

Compaq welcomes your comments on this manual. Please send comments to either of the following addresses:

How to Order Additional Documentation

Use the following World Wide Web address to order additional documentation:

http://www.openvms.compaq.com/

If you need help deciding which documentation best meets your needs, call 800-282-6672.

Conventions

The following conventions are used in this manual:

This chapter presents an overview of the Delta and XDelta Debuggers. It then describes the following:

• Privileges required for running DELTA
• Guidelines for using XDELTA
• Invoking and terminating DELTA and XDELTA debugging sessions on OpenVMS VAX and OpenVMS Alpha systems
• Booting XDELTA, requesting interrupts, and accessing initial breakpoints on OpenVMS VAX and OpenVMS Alpha systems

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.

Because DELTA operates in a process context, use it to debug user-mode programs or 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).

Because XDELTA is invoked directly from the hardware SCB vector, it can be used to debug programs executing in any processor mode or at any IPL level. Use it to debug programs that execute at an elevated IPL. 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 privileges.

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 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 Invoking DELTA

To invoke DELTA, perform the following steps after assembling (or compiling) and linking your program:

1. Define DELTA as the default debugger instead of the symbolic debugger with the following command:

   $ DEFINE LIB$DEBUG SYS$LIBRARY:DELTA

2. Use the following RUN command to execute your program:

   $ RUN/DEBUG MYPROG

When DELTA begins execution, it displays its name and current version number. DELTA displays the first executable instruction in the program with which it is linked. It displays the address of that instruction, a separator (a slash (/) on VAX and an exclamation point (!) on Alpha), and the instruction and its operands.

On VAX, the name, current version number, and address are displayed as follows:

DELTA Version 5.5
address/instruction operands

On Alpha, the name, current version number, and address are displayed as follows:

AlphaVMS DELTA Version 1.0
address!instruction operands

On Alpha and VAX, 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.

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.

1.6 Invoking XDELTA

To invoke XDELTA, perform the following steps:

1. Boot the system using a console command or a command procedure that includes XDELTA.
2. 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 address/instruction

   Note 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 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 address!instruction

3. On Alpha and VAX, proceed from the initial breakpoint, using the following command:

   ;P [Return]

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 XDELTA.

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. Refer to Table 1-1 for a description of the valid values for this flag.

For directions for booting XDelta on a VAX computer, refer to 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 as follows:

>>> BOOT -FLAG 0,7

The flag for specifying boot qualifiers is a 64-bit integer that is passed directly as input to APB.EXE, the primary boot program. Refer to Table 1-1 for a description of the valid values for this flag.

On Alpha and VAX, if you set the boot control flag to 7, 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. Refer to Section 1.8 for the breakpoint procedure.

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 Alpha, INI$BRK is defined as XDELTA's breakpoint 0. It is not possible to clear breakpoint 0 from any code being debugged in XDELTA.

1.7.1 Requesting Interrupts on VAX Computers

For a VAX 8530, 8550, 8600, 8650, 8810 (8700), 8820, 8820-N (8800), 8830, 8840, VAX-11/780, or VAX-11/785 computer, enter the following commands at the console terminal to request the interrupt:

$ [Ctrl/P]
>>> HALT
>>> D/I 14 E
>>> C

For a VAX 9000 computer, enter the following commands at the console terminal to request the interrupt:

$ [Ctrl/P]
>>> HALT/CPU=ALL
>>> D/I 14 E
>>> C/CPU=ALL

For a VAX 6000 series, 8200, 8250, 8300, 8350, VAX-11/730, or a VAX-11/750 computer, enter the following commands:

$ [Ctrl/P]
>>> D/I 14 E
>>> C

For a VAXstation 3520 or 3540 computer, perform the following steps:

1. Press and release the Halt button on the CPU control panel. When you release the Halt button, make sure it is popped out or the system will remain halted. You can also press the Break key (if enabled) on the console terminal.
2. Enter the following commands:

   >>> D/I 14 E >>> C/ALL

For a VAXft 3000, VAXft-410, VAXft-610, or VAXft-612 computer, enter the following commands at the console terminal to request the interrupt:

$  [Break] or [F5]
>>> HALT
>>> D/I 14 E
>>> CONT
>>> PIO

For a VAX 7000 or VAX 10000 series computer, enter the following commands at the console terminal to request the interrupt. If you are operating in secure mode, first set the keyswitch to ENABLE before entering these commands.

$  [Ctrl/P]
>>> D IPR:14 E
>>> CONT

For a VAXstation 2000, MicroVAX 2000, MicroVAX 3300/3400 series, MicroVAX or VAXstation 3500/3600 series, MicroVAX 3800/3900 series, VAX 4000 series, or MicroVAX II computer, perform the following steps:

1. Press and release the Halt button on the CPU control panel. When you release the Halt button, make sure it is popped out or the system will remain halted. You can also press the Break key (if enabled) on the console terminal.
2. Enter the following commands:

   >>> D/I 14 E >>> C

For an alternative method of accessing OpenVMS through a lower priority interrupt, refer to the OpenVMS System Manager's Manual.