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Document:	VMS 5.0 Delta Xdelta Utility Manual 198804
Order Number:	AA-LA86A-TE
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Pages:	69
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VMS

VMS Delta/XDelta Utility Manual

Order Number AA-LA86A-TE

VMS Delta/XDelta Utility
Manual
Order Number: AA-LA86A-TE

April 1988
This manual describes the VMS Delta/XDelta Utility. This utility is used
primarily to debug programs that run in privileged processor mode or at an
elevated interrupt priority level.

Revision/Update Information:

This document supersedes the
VAX/VMS Delta/XDelta Utility
Reference Manual, Version 4.0.

Software Version:

VMS Version 5.0

digital equipment corporation
maynard, massachusetts

April 1988
The information in this document is subject to change without notice and should
not be construed as a commitment by Digital Equipment Corporation. Digital
Equipment Corporation assumes no responsibility for any errors that may appear
in this document.
The software described in this document is furnished under a license and may be
used or copied only in accordance with the terms of such license.
No responsibility is assumed for the use or reliability of software on equipment
that is not supplied by Digital Equipment Corporation or its affiliated companies.
Copyright © 1988 by Digital Equipment Corporation
AIJ Rights Reserved.
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Contents
PREFACE

vii

NEW AND CHANGED FEATURES

DELTA/XDELTA Description
1
1.1
1.2
1.3
1.3. 1
1.3.2
1.3.3
1.3.4
1.3.5

1.3.6
1.4
1.5
1.6
1.7

2
2.1

2.2
3
3.1
3.2
3.3
3.4

DELTA-1

DELTA-1
ENTERING AND EXITING FROM DELTA/XDELTA
Invoking DELTA ~-------------- DELTA-1
Exiting from DELTA - - - - - - - - - - - - - DELTA-2
Invoking XDELTA - - - - - - - - - - - - - - DELTA-2
Bootstrapping XDEL TA on a VAX 8800, 8700, 8550, or
8530 • DELTA-2
Bootstrapping XDELTA on a VAX 8650 or a VAX
8600 • DELT A-3
Bootstrapping XDELTA on a VAX 8350, 8300, 8250, or
8200 • DELTA-4
Bootstrapping XDELTA on a V AX-11 /780 or a
VAX-11/785 • DELTA-4
Bootstrapping XDELTA on a V AX-11 /750, VAXstation
2000, MicroVAX 2000, MicroVAX 3500, MicroVAX 3600,
MicroVAX I, or MicroVAX II• DELTA-5
Bootstrapping the System Using the VMS Console
TU58 • DELTA-6
Requesting an Interrupt - - - - - - - - - - - - DELTA-6
Accessing the Initial Breakpoint - - - - - - - - - DELTA-7
Proceeding from Initial XDELTA Breakpoints _ _ _ _ _ DELTA-8
Exiting from XDELTA - - - - - - - - - - - - - DELTA-8
DELTA AND XDELTA SYMBOLS AND EXPRESSIONS
DELTA-8
Symbols Supplied by DELTA and XDELTA - - - - - - DELTA-9
Forming Numeric Expressions - - - - - - - - - - DELTA-9
GUIDELINES FOR DEBUGGING PROGRAMS WITH DELTA OR
XDELTA
DELTA-10
_
_
_
_
_
_
_
_
_
_
_
_
DELTA-10
Referencing Addresses
_
_
_
_
_
_
_
_
_
_
_
_
DELTA-13
Referencing Registers
Interpreting the Error Message ~---------DELTA-13
Using XDELTA on Multiprocessing Systems _ _ _ _ _ DELTA-13

DELTA/XDELTA Usage Summary

DELTA-14

Contents

DELTA/XDELTA Commands
[ (SET DISPLAY MODE)
/(OPEN LOCATION AND DISPLAY
CONTENTS IN PREVAILING
WIDTH MODE)
! (OPEN LOCATION AND DISPLAY
CONTENTS IN INSTRUCTION
MODE)
1.---Ll-NE-FE-E----.DI (CLOSE CURRENT
LOCATION, OPEN NEXT)
IEscl (OPEN LOCATION AND DISPLAY
PREVIOUS LOCATION)
ITABI (OPEN LOCATION AND DISPLAY
INDIRECT LOCATION)
11
(OPEN LOCATION AND DISPLAY
CONTENTS IN ASCII)
1.----RE-TU-R----.NI (CLOSE CURRENT LOCATION)
;B (BREAKPOINT)
;P (PROCEED FROM BREAKPOINT)
;G (GO)
S (STEP INSTRUCTION)
0 (STEP INSTRUCTION OVER
SUBROUTINE)
(DEPOSIT ASCII STRING)
;E (EXECUTE COMMAND STRING)
;X (LOAD BASE REGISTER)
(DISPLAY VALUE OF EXPRESSION)
;M (SET ALL PROCESSES WRITABLE)
;L (LIST NAMES AND LOCATIONS OF
LOADED EXECUTIVE IMAGES)
EXIT (EXIT FROM DELTA
DEBUGGING SESSION)
I

APPENDIX A SAMPLE DELTA DEBUG SESSION

DELTA-15
DELTA-16

DELTA-17

DELTA-20
DELTA-22
DELTA-23
DELTA-24
DELTA-25
DELTA-27
DELTA-28
DELTA-32
DELTA-33
DELTA-34
DELTA-35
DELTA-37
DELTA-38
DELTA-40
DELTA-42
DELTA-43
DELTA-44
DELTA-45

A-1

INDEX

TABLES

DELT A-1

Boot Command Qualifier Values

DELTA-2

DELTA/XDELTA Symbols

DELTA-9

DELT A-3

Arithmetic Operators

DELTA-10

DELTA-4

DELTA/XDELTA Command Summary

DELTA-15

Preface
Intended Audience
This document 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 document consists of the following four sections:
•

Description-Provides an overview and detailed usage information for
the Delta/XDelta Utility (DELTA/XDELTA).

•

Usage Summary-Outlines the following DELTA/XDELTA information:
-Invoking the utility
-Exiting from the utility
-Directing output
-Restrictions or privileges required

•

Commands-Describes DELTA/XDELTA commands, including format,
parameters, and examples.

•

Appendix A-Describes a debugging session using DELTA.

Associated Documents
For additional information on topics covered in this document, refer to the

VMS Device Support Manual.

vii

Preface

Conventions
Convention

Meaning
In examples, a key name (usually abbreviated)
shown within a box indicates that you press
a key on the keyboard; in text, a key name is
not enclosed in a box. In this example, the key
is the RETURN key. (Note that the RETURN
key is not usually shown in syntax statements
or in all examples; however, assume that you
must press the RETURN key after entering a
command or responding to a prompt.)

viii

CTRL/C

A key combination, shown in uppercase with a
slash separating two key names, indicates that
you hold down the first key while you press the
second key. For example, the key combination
CTRL/C indicates that you hold down the key
labeled CTRL while you press the key labeled C.
In examples, a key combination is enclosed in a
box.

$SHOW TIME
05-JUN-1988 11 :55:22

In examples, system output (what the system
displays) is shown in black. User input (what
you enter) is shown in red.

$ TYPE MYFILE.DAT

In examples, a vertical series of periods, or
ellipsis, means either that not all the data that
the system would display in response to a
command is shown or that not all the data a
user would enter is shown.

input-file, ...

In examples, a horizontal ellipsis indicates
that additional parameters, values, or other
information can be entered, that preceding
items can be repeated one or more times, or
that optional arguments in a statement have
been omitted.

[logical-name]

Brackets indicate that the enclosed item is
optional. (Brackets are not, however, optional
in the syntax of a directory name in a file
specification or in the syntax of a substring
specification in an assignment statement.)

quotation marks
apostrophes

The term quotation marks is used to refer
to double quotation marks ( " ) . The term
apostrophe ( · ) is used to refer to a single
quotation mark.

New and Changed Features
The Delta/XDelta Utility incorporates the following three changes for VMS
Version 5.0:
•

The ;L command-The ;L command has been added. It lists all loaded
executive modules and their locations.

•

Multiprocessing system-XDELTA runs on a multiprocessing system, but
only one processor at a time can enter XDEL TA.

•

Requesting interrupts-All software interrupt requests for invoking
XDELTA on all processors are at IPL 14 10 .

DELT A/XDELTA Description
The Delta/XDelta Utility (DELTA/XDELTA) consists of two debuggers:
DELTA and XDELTA. The debuggers are used to monitor the execution of
user programs and the VMS operating system. DELTA and XDELTA use the
same commands and the same expressions. 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. 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
debug programs executing in any processor mode or at any IPL level. Because
it is not process-specific, it is not invoked from a process. To use it, you must
boot the processor with commands to include XDELTA in memory. XDELTA's
existence terminates when you reboot the processor without XDEL TA.

Entering and Exiting from DELT A/XDELTA
This section describes how to invoke and how to terminate DELTA and
XDEL TA debug sessions.

1 .1

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.
Use the following command:
$ DEFINE LIB$DEBUG SYS$LIBRARY:DELTA

Use the RUN command to execute your program. Use the following
command:
$ RUN/DEBUG program-name

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 slash (/), and
the instruction and its operands.
The name, current version number, and address are displayed as follows:
DELTA Version 5.0
address/instruction operands

DELTA is then ready for your commands.

DELTA-1

DELTA/XDELTA Description

1.2

Exiting from DELTA
To exit from DELTA, type EXIT and press IRETURNL When you are in user
mode, you exit DELTA, and your process remains. When you are in a
privileged access mode, your process may be deleted as well.

1.3

Invoking XDELTA
To invoke XDEL TA, perform the following steps:

Bootstrap the system using a console command or a command procedure
that includes XDELTA.

An initial XDEL TA breakpoint is taken to allow setting of additional
breakpoints or examining and changing locations in memory. XDELTA
displays the following breakpoint message:
1 BRK at 8000EB63
8000EB63/NOP

Proceed from the initial breakpoint, using the following command:
;P

JRETURNJ

The procedure for bootstrapping the system with XDEL TA differs depending
on your processor. Each procedure uses commands that include XDELTA
in memory and cause the execution of a breakpoint in VMS initialization
routines. Execution of the breakpoint instruction transfers program control
to a fault handler located in XDEL TA. The following sections describe the
procedures for bootstrapping the processors, requesting an interrupt, and
setting breakpoints in program code.

1.3.1

Bootstrapping XDELTA on a VAX 8800, 8700, 8550, or 8530
To boot a VAX 8800, 8700, 8SSO, or 8S30, use the BOOT command in the
following format:

> > > B dddn /R5:f
Substitute BCI, BDA, or UDA for ddd. Substitute the unit number of the drive
holding the system disk for n. The /RS qualifier enters a value for a flag that
controls the way XDEL TA is loaded. The flag is a 32-bit hexadecimal integer
loaded into RS as input to VMS.EXE, the primary bootstrap program. Refer to
Table DEL TA-1 for a description of the valid values for this flag.
Table DELTA-1

DELTA-2

Boot Command Qualifier Values

Value

Description

Normal, nonstop bootstrap (default)

Stop in SYSBOOT (equivalent to @DxyGEN on the V AX-11 /780)

Include XDEL TA with the system, but do not take the initial breakpoint

Include XDELTA with the system, and take the initial breakpoint

Include XDEL TA with the system, stop in SYSBOOT, and take the
initial breakpoint at system initialization (equivalent to @DxyXDT on the
VAX-11 /750)

DELT A/XDELTA Description

Note: When you deposit a boot command qualifier value in RS, 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 as well as an XDEL TA value, RS would contain
both values. If the system root directory value were 40000000, and the
XDEL TA value were OOOOOOOS, the final RS value would be 4000000S.
For example, if you have a BCI-controlled system disk with a unit number
of two, the following command would load XDELTA and take the initial
breakpoint:
>»s BC12 /R5: 6

This command boots the system with BCIBOO.COM, deposits two in R3, and
deposits six in RS.
You can also boot with XDELTA by editing the appropriate dddGEN.COM
procedure so that the unit number of the drive is deposited in R3. Then you
can enter the BOOT command in the following format:
>>>@dddGEN

Substitute BCI, BDA, or UDA for ddd. For example, suppose the system disk
is on a BCI-controlled drive. Edit BCIGEN.COM so that the unit number of
the drive is deposited in R3. At the console-mode prompt, enter the following
command:
»>@BCIGEN

1.3.2

Bootstrapping XDELTA on a VAX 8650 or a VAX 8600
There are two ways to boot a VAX 8650 or VAX 8600 with XDELTA,
depending on whether the console RL02 includes a boot command file in
the ddOXDT format, where dd is the device code of the system disk.

If DUOXDT is present, follow the standard boot procedure except in the
following two steps:
•

When you specify the bootstrap device, enter the following command:
>»DEPOSIT R3 u

This command deposits the unit number of the drive holding the system
disk, u, from which to boot.
•

Then enter the following command to invoke DUOXDT:
>»@DUOXDT

The command procedure boots the processor and prompts you from
SYSBOOT. When the SYSBOOT> prompt appears, enter any SYSBOOT
command.
To continue the bootstrapping operation, enter CONTINUE.

If the console media does not have the DUOXDT file, perform a normal
bootstrap procedure using an available dduGEN.COM, dduBOO.COM, or
DEFBOO.COM procedure, including the following steps:
1

Include the /NOSTART qualifer to the BOOT command to cause the
processor to pause and prompt for console commands prior to starting the
VMB initialization routines.

DELTA-3

DELTA/XDELTA Description

Select a value for the boot flag to control the loading of XDEL TA from
Table DELTA-1 in Section 1.3.1.

Examine the value of the boot flag in RS. If it is not the value you want,
deposit the correct value.

For example, the following procedure is used to boot a VAX 8600 to include
XDELTA, stop in SYSBOOT, take the initial breakpoint (flag value of 7), and
continue the boot procedure:
>>> BOOT/NOSTART
>>> EXAMINE R5 40000000
>>> DEPOSIT R5 2 40000007
>» CONTINUE

1.3.3

Bootstrapping XDELTA on a VAX 8350, 8300, 8250, or 8200
To bootstrap a VAX 83SO, 8300, 82SO, or 8200 processor with XDELTA, use
the B command (the console BOOT command) as follows:
B[/R5:f] devname

The BOOT command qualifier, /RS:f, enters a value for a flag that controls
how to load XDELTA. The flag is a 32-bit hexadecimal integer loaded
into RS as input to VMB.EXE, the primary bootstrap program. Refer to
Table DELTA-1 for a description of the valid values for this flag. To use this
qualifier, you must first modify the boot command procedure to remove (or
comment out) the DEPOSIT RS command.
The boot command procedure is specified by devname in the BOOT command.
The devname format to use is ddxu, where x is the number of the VAXBI node
to which the boot device unit is attached. If you do not specify devname, the
default boot device is used.
If in RS you specified the flag to load SYSBOOT, the SYSBOOT> prompt

appears. Enter any SYSBOOT command.
For example, use the following commands to boot a VAX 8200 from the boot
disk at VAXBI node 4, load XDELTA, stop in SYSBOOT, and take the initial
breakpoint (that is, RS contains 7):
>» B/R5:7 DU40
SYSBOOT> CONTINUE

1.3.4

Bootstrapping XDELTA on a VAX-11/780 or a VAX-11/785
In addition to the normal system bootstrap command files, the VMS console
RXOl for a VAX-11/780 or VAX-11/78S contains the following command
files that bootstrap the system with XDEL TA:
•

DUAXDT.CMD

•

DMAXDT.CMD

•

DBAXDT.CMD

To bootstrap the system with XDEL TA, follow the procedures in the
operations guide for your processor, with the following exceptions:

DELTA-4

•

In R3, deposit the unit number of the drive holding the system disk.

•

Specify one of the preceding command files.

DELTA/XDELTA Description

For example, if the unit number of the drive holding the system disk is zero,
enter the following command:
>»DEPOSIT R3 0

Then specify the command file that corresponds to the drive holding the
system disk. For example, if the system disk is on an RASO drive with a
controller designation of A, enter the following command:
»>@DUAXDT

The command procedure boots the processor and prompts you from
SYSBOOT. When the SYSBOOT> prompt appears, enter any SYSBOOT
command.
To continue the bootstrapping operation, enter CONTINUE.
1.3.5

Bootstrapping XDELTA on a VAX-11/750, VAXstation 2000,
MicroVAX 2000, MicroVAX 3500, MicroVAX 3600, MicroVAX I, or
MicroVAX II
To bootstrap VMS with XDELTA on a VAX-11/7SO, a VAXstation 2000, a
MicroVAX2000, a MicroVAX 3SOO, a MicroVAX 3600, a MicroVAX I, or a
MicroVAX II, enter the following command to specify the boot device:
>»B/n devname

The B command is the console's BOOT command.
The devname parameter is the name of the device from which to bootstrap
the system. Specify the device name using the format ddcu. (See the Guide to
Maintaining a VMS System for a complete description. of the format of device
names.) You must specify identifiers for both the controller and the unit
identifiers; there are no defaults.
The /n qualifier loads the value n into RS. The contents of RS are passed
as input to VMB.EXE. The value of n must be one of the 32-bit hexadecimal
numbers described in Table DELTA-1 in Section 1.3.1.
For example, the following commands bootstrap VMS on a VAX-11/7SO from
DUAO with XDELTA included, stop at XDELTA's initial breakpoint, and stop
in SYSBOOT to allow setting of system parameters:
>»B/7 DUAO

The /7 qualifier includes XDELTA in the system and stops the booting process
in SYSBOOT, which issues a prompt. It also stops at the breakpoint in the
system initialization routine.
You can enter SYSBOOT commands when you see the SYSBOOT> prompt.
To continue the bootstrapping operation, enter CONTINUE.
See the installation guide for your processor for more information on the B
command.

DELTA-5

DELTA/XDELTA Description

1.3.6

Bootstrapping the System Using the VMS Console TU58
In addition to the normal system bootstrap command files, the VMS console
TUS8 for a VAX-11/730 or a VAX-11/725 contains the following command
files that bootstrap the system with XDELTA:

•

DQAXDT

•

DQOXDT

•

DLOXDT

•

DUAXDT

•

DUOXDT

To bootstrap a VAX-11/730 or VAX-11/725 with XDELTA, follow the
procedures outlined in the installation guide for the processor, but specify one
of the preceding command files.
For example, to bootstrap the VAX-11/730 from DQAl, enter the following
commands:
>» D/G/L 3 1
>» ©DQAXDT

The first command, D, deposits the unit number, one, in R3. The second
command, @DQAXDT, invokes the DQAXDT command procedure.
If the boot device is DQAO, invoke the DQOXDT command procedure, as
follows. You do not have to specify the unit number.
>» ©DQOXDT

Either of these procedures boots the processor and prompts you from
SYSBOOT. When SYSBOOT prompts you, enter any SYSBOOT command.
To continue the bootstrapping process, enter CONTINUE.
To bootstrap a VAX-11/750 with the console TU58, refer to the software
installation guide for the VAX-11/750 processor. The console TU58 contains
the command files DUAXDT, DMAXDT, and DBAXDT, which contain the
command procedures that boot the system from DU, DM, and DB devices,
respectively.

1 .4

Requesting an Interrupt
If you set the boot control flag in RS to 7, as described in Section 1.3, XDELTA
will stop at an initial breakpoint during the system bootstrap process. You
can then set other breakpoints or examine locations in memory.

Your program can also call the routine INI$BRK, which in turn executes
the first XDELTA breakpoint. Note that INI$BRK is defined as XDELTA's
breakpoint 1. Never clear breakpoint 1 from any code being debugged in
XDELTA. Refer to Section 1.5 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 XDEL TA if your program is in an infinite
loop or no INI$BRK call had been made.
To request a software interrupt for all processors, deposit the value E16 into
IPR 14 16 .
DELTA-6

DELTA/XDELTA Description

For a VAX 8800, 8700, 8650, 8600, 8550, 8530, VAX-11/785, or
VAX-11/780, enter the following commands at the console terminal to
request the interrupt:
$ icTRL/PI
»>HALT
»> D/I 14 E
>»c

On a VAX 8350, 8300, 8250, 8200, a VAX-11/750, a VAX-11/730, or a
VAX-11/725, enter the following commands:
$ lcTRL/PI
»> D/I 14 E
>» c

For the VAXstation 2000, MicroVAX 2000, MicroVAX 3500, MicroVAX 3600,
MicroVAX I or MicroVAX II, 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
remains halted. You can also press the BREAK key (if enabled) on the
console terminal.

Enter the following commands:
>» D/I 14 E
»> c

1 .5

Accessing the Initial Breakpoint
When debugging a program, you can set a breakpoint in the code so that
XDELTA gains control of program execution.
To set a breakpoint, place a call to the system routine INI$BRK in the source
code.
For example, the following command calls the INI$BRK system routine to
reach the breakpoint:
JSB G~INI$BRK

On systems that are not booted with XDELTA, the BPT instruction in
INI$BRK is replaced with a NOP instruction.
Note: INl$BRK is defined as XDELTA's breakpoint 1. Never clear breakpoint 1
from any code being debugged with XDEL TA.
The INI$BRK routine contains two instructions: BPT and RSB. You can use
the INI$BRK routine as a debugging tool, placing calls to this routine in any
part of the source code you want to debug. After the break is taken, the
return address (the address in the program to which control returns when you
proceed from the breakpoint) is on the top of the stack.

DELTA-7

DELTA/XDELTA Description

1.6

Proceeding from Initial XDELTA Breakpoints
When XDELTA reaches one of its breakpoints, it displays the following
message:
1 BRK AT nnnnnnnn
address/instruction operands

On multiprocessors, the XDEL TA breakpoint will be taken on the processor
upon which the XDEL TA software interrupt was requested, which is generally
the primary processor.
At this point, XDEL TA is waiting for input. If you want to proceed with
program execution, enter the ;P command. If you want to do step-by-step
program execution, enter the S command. If you know where you have
set breakpoints, examine them using the ;B command. You can also set
additional breakpoints or modify existing ones.
If you entered the ;P command to proceed with program execution, and
the system halts with a fatal bugcheck, the system prints the bugcheck
information on the console terminal. Bugcheck information consists of the
following:

•

Type of bugcheck

•

Contents of the registers

•

A dump of one or more stacks

•

A list of loaded executive images

The contents of the program counter (PC) and the stack indicate where the
failure was detected. Then, if the system parameter BUGREBOOT was set to
0, XDELTA issues a prompt. You can examine the system's state further by
entering XDELTA commands.

1 .7

Exiting from XDELTA
XDEL TA remains in memory with the operating system until you reboot
without it.

DELTA and XDELTA Symbols and Expressions
This section describes how to form the symbolic expressions used as
arguments to many DEL TA and XDEL TA commands.

DELTA-8

DELTA/XDELTA Description

2.1

Symbols Supplied by DELTA and XDELTA
DEL TA and XDELTA define symbols that are useful in forming expressions
and referring to registers. The symbols are described in Table DELTA-2.
Table DELTA-2
Symbol

DELTA/XDELTA Symbols

Description
The current address, the address of the current location. The value
of this symbol is set by the Open Location and Display Contents (/),
Open Location and Display Instruction (!), and the Open Location and
Display Indirect OTABD commands.

The last value displayed. The value of Q is set by every command
that causes DELTA or XDELTA to display the contents of memory or
the value of an expression.

Base register n, where n can range from 0 to F (hexadecimal). These
registers are used for storing values, most often the base addresses
of data structures in memory.
For XDELTA only, XE and XF contain the addresses of two command
strings that XDELTA stores in memory. See the Execute Command
String (;E) command for more information.
For XDELTA only, registers X4 and X5 contain specific addresses. X4
contains the address of the location that contains the address of the
PCB of the current process on the current processor. The address that
X4 contains is that of the per-CPU database for the current processor.
X5 contains SCH$GL_PCBVEC, the symbolic address of the start of
the PCB vector, the list of PCB slots.

2.2

General register n, where n can range from 0 to F (hexadecimal). RF+4
is the processor status longword (PSL), RE is the stack pointer, and RF
is the program counter (PC).

The internal processor register at processor address n, where n can
range from 0 to 3F (hexadecimal). See the VAX Hardware Handbook
for a description of these processor registers.

Axaooooooo, the prefix for system space addresses. G2E, for
example, is equivalent to AX8000002E.

AX7FFEOOOO, the prefix for addresses in the control region (P1 space).
H2E, for example, is equivalent to AX7FFE002E.

Forming Numeric Expressions
Expressions are combinations of numbers, symbols that have numeric values,
and arithmetic operators. Both DELTA and XDELTA store and display all
numbers in hexadecimal. They also interpret all numbers as hexadecimal.
Expressions are formed using regular (infix) notation, rather than Polish or
reverse Polish notation. Both DEL TA and XDELTA ignore operators that trail
the expression. Following is a typical expression (in hexadecimal):
G4A32+24

DELTA and XDELTA evaluate expressions from left to right. No operator
takes precedence over any other.
DELTA-9

DELTA/XDELTA Description

DEL TA and XDEL TA recognize five binary arithmetic operators, one of which
also acts as a unary operator. They are listed in Table DELTA-3.
Table DELTA-3

Arithmetic Operators

Operator

Action

+or !SPACE I

Addition
Subtraction when used as a binary operator, or negation
when used as a unary operator

Multiplication

Division

Arithmetic shift

The following example shows the arguments required by the arithmetic-shift
operator:
n©j

In this example, n is the number to be shifted, and j is the number of bits
to shift it. If j is positive, n is shifted to the left; if j is negative, n is shifted
to the right. Argument j must be less than 20 16 and greater than -20 16 . Bits
shifted beyond the limit of the longword are lost; therefore, the result must fit
into a longword.

Guidelines for Debugging Programs with DELTA or XDELTA
When you use DEL TA or XDEL TA, there are no prompts, few symbols, and
one error message. You move through program code by referring directly to
address locations. This section provides guidelines for the following actions:
•

Referencing addresses

•

Referencing registers, the PSL, and the stack

•

Interpreting the error message

For an example of a DELTA debug session, refer to Appendix A.

3.1

Referencing Addresses
When using DELTA or XDELTA to debug programs, you move through the
code by referring to addresses. To help you identify address locations within
your program, use a list file and a map file. The list file (.LIS) lists each
instruction and its offset value from the base address of the program section.
The full map file (.MAP) lists the base addresses for each section of your
program. To determine the base address of a device driver program, refer to
the VMS Device Support Manual.
Once you have the base addresses of the program sections, locate the
instruction in the list file where you want to start the debug work. Add the
offset from the list program to the base address from the map file. Remember
that all calculations of address locations are done in hexadecimal. You can
use DELTA/XDELTA to do the calculations for you with the = command.

DELTA-10

DELT A/XDELTA Description

To make address referencing easier, you can use offsets to a base address.
Then you do not have to calculate all address locations. First, place the base
address into a base register. Then move to a location using the offset to the
base address stored in the register.
The following example of a simple MACRO program (EXAMPLE.MAR) and
address referencing procedure shows how to reference addresses during a
DEL TA debug session. You can also use the same commands in an XDEL TA
debug session.
0000
0000
0000
0002
0004
0007
OOOA
0060
OOOE
OOOE

1
2
3
4
5

.title

example

.entry

10$:

7
8
9
10

start
clrl
movl
addl
sobgtr
ret

.end

AM<r3,r4>
r3
#5,r4
r4,r3
r4, 10$

start

The following procedure generates information to assist you with address
referencing:
1

Use the /LIST qualifier to assemble the program and generate the list file.
To generate the list file for the preceding example, use the following
command:
$ MACRO /LIST EXAMPLE

Use the /MAP qualifier with the link command to generate the full map
file (.MAP file). Make sure that the default /DEBUG or /TRACEBACK
qualifier is active for your link command. If not, specify /DEBUG or
/TRACEBACK along with the /MAP qualifier.
To generate the map file for the example program, use the following
command:
$ LINK/MAP EXAMPLE

Refer to the Program Section Synopsis of the map file. Locate the section
that you want to debug. Look up the base address.
For the example program, the map file is EXAMPLE.MAP. A portion of
the Program Section Synopsis is shown below. The first section of the
program has a base address of 200.

+--------------------------+
! Program Section Synopsis !

+--------------------------+
Psect Name

Module Name

. BLANK .
EXAMPLE

Base

End

Length

00000200 00000200 OOOOOOOE (
00000200 00000200 OOOOOOOE (

14.)
14.)

Refer to the list file for the location of the specific instruction where you
want to start debugging.
For the example program, start with the second instruction (MOVL #5,R4)
with an offset of 4.
DELTA-11

DELTA/XDELTA Description

Enable DEL TA using the following commands:
$ DEFINE LIB$DEBUG SYS$LIBRARY: DELTA
$ RUN/DEBUG EXAMPLE

If you want to store the base address in a base register, use the ;X
command to load the base register.

For the example program, use the following DEL TA/XDEL TA command
to store the base address 200 in base register 0.
200 '0;

x IRETURN I

Now you can move to specific address locations.
For example, if you wanted to place a breakpoint at the second instruction
(MOVL #S,R4), you would calculate the address as 200 (base address)
plus 4 (offset), or 204. Following is the DELTA/XDELTA command to set
the breakpoint at address 204:
204 ; B

IRETURN I

If you stored the base address in the base register, you could use
the address expression X0+4 (or "XO 4", where the + sign is implied).
Following is the command to set the breakpoint:
X0+4; B

IRETURN I

Reverse this technique to find an instruction displayed by DEL TA/XDEL TA in
the .LIS file, as follows:
1

Note the address of the instruction you want to locate in the .LIS file.
For example, DEL TA/XDEL TA displays the following instruction at
address 020A:
20A!SOBGTR

R4,00000207

The following steps allow you to find the instruction at location 207.

Refer to the .MAP file, and identify the PSECT and MODULE where
the address of the instruction is located. Check the base address value
and the end address value of each PSECT and MODULE. When the
instruction address is between the base and end address values, record
the PSECT and MODULE names.
In the example, the instruction address is located in the EXAMPLE
module (.BLANK. psect). The address instruction, 207, is between the
base address 200 and the end address 20D.

Subtract the base address from the instruction address. Remember that all
calculations are in hexadecimal and that you can use the DEL TA/XDEL TA
=command to do the calculations. The result is the offset.
For the example, subtract the base address 200 from the instruction
address 207. The offset is 7.

DELTA-12

Refer to the .LIS file. Look up the MODULE, and then find the correct
PSECT. Look for the offset value you calculated in the previous step.

DELTA/XDELTA Description

In the example, there is only one PSECT and MODULE. Look up
the instruction at offset 7. The program is branching to the following
instruction:
10$:

3. 2

addl r4,r3

Referencing Registers
To view the contents of the 16 general registers (including the program
counter and the stack pointer) and the processor status longword (PSL), use
the same DEL TA/XDELTA commands as you use to view the contents of
any memory location (for example, the /, luNEFEEDL and the IEscl commands).
The symbols to use to identify the locations of the registers and PSL are as
follows:

3.3

•

The general registers are referred to by the symbol R and a hexadecimal
number from 016 to F16 representing the number of the register. For
example, general register 110 is R1 16 , and general register 10 10 is RA 16 .
The stack pointer is located in general register 14 10 , RE 16 . The program
counter is in general register 1510, RF16·

•

Upon entry to DEL TA or XDEL TA, the PSL is stored in the longword
directly following the longword representing general register F16 .
Reference it by using the general register F16 symbol plus a longword
(RF+4).

Interpreting the Error Message
When you make an error entering a command in DEL TA or XDEL TA, you get
the EH? error message. This is the only error message generated by DELTA
or XDEL TA. It is displayed if you enter an invalid command or reference an
address that cannot be displayed.

3.4

Using XDELTA on Multiprocessing Systems
On multiprocessing systems, only one processor can use XDELTA at a time.
If a second processor attempts to enter XDELTA when another processor
has already entered it, the second processor waits until the first processor
has exited XDELTA. If the processor using XDEL TA sets a breakpoint, other
processors are aware of the breakpoint. Therefore, when the code with the
XDEL TA breakpoint is executed on another processor, that processor will
enter XDELTA and stop at the specified breakpoint.
When a breakpoint is taken by a processor in a multiprocessing environment,
the processor's physical identification number is displayed on the XDEL TA
breakpoint message line as a 2-digit hexadecimal number. The following is
an example of a breakpoint message in a multiprocessing environment:
1 BRK AT 00000400 ON CPU 03
00000400/MOVL #5,R4

XDEL TA uses its own system control block (SCB) to direct all interrupt
handling to an error handling routine in XDEL TA. Therefore, an error
encountered by XDELTA does not affect any other processors that share
the standard system SCB.
DELTA-13

DELT A/XDELTA Usage Summary

The Delta/XDelta Utility (DEL T A/XDEL TA) consists of two debuggers:
DELTA and XDEL TA. Use DELTA to debug user mode programs or
programs that execute at interrupt priority level (IPL) 0. Use XDEL TA to
debug programs that execute at an elevated IPL, such as VMS executive
routines, device drivers, and other privileged code.

usage summary
DELTA

To invoke DELTA, define DELTA as the default debugger, and run the
program, as follows:
$DEFINE LIB$DEBUG SYS$LIBRARY:DELTA
$ RUN/DEBUG program-name

To exit from DELTA, enter the EXIT command.
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 link the program must have the necessary privileges.
To use the ;M command (Set All Processes Writable), your process must have
change-mode-to-kernel (CMKRNL) privilege. To use the ;L command, (List
All Loaded Executive Modules) you must have change-mode-to-executive
(CMEXEC) privilege.
You cannot redirect output from a DEL TA debug session.
XDELTA

To invoke XDELTA, bootstrap the system using a console command
or command procedure that includes XDEL TA. At the initial XDEL TA
breakpoint, set additional breakpoints, or examine and change locations
in memory. Then proceed from the initial breakpoint. Refer to Section 1.3 for
detailed steps on invoking XDELTA for each processor family.
To terminate an XDELTA debug session, reboot without XDELTA.
Because XDELTA is not process specific, privileges are not required. However,
you must use the console terminal. You should run XDELTA only on a
standalone system because all breakpoints are handled at IPL 31 10 .
You cannot redirect output from XDEL TA. Because you use XDELTA at a
console terminal, you have a record of the debugging session. If your console
terminal is a hardcopy terminal, you will have a written record; otherwise,
output is typically stored in a console-maintained log file. MicroVAX systems
do not maintain log files.

DELTA-14

DELTA/XDELTA
DELTA/XDELTA Commands

DELTA/XDELTA This section describes how to use each DELTA and XDEL TA command to
debug a program.
COMMANDS
Only DELTA uses the EXIT and ;M commands and arguments that specify a
process identification. XDEL TA defines some base registers that DEL TA does
not (refer to Section 2). With those exceptions, DELTA and XDEL TA use the
same commands. Differences are noted in command descriptions.
Enter the ILINEFEED I. IESC I. IT AB I. and IRETURN I commands by pressing the
corresponding key.
Each command includes an example. The program used for the examples is
the same program listed in Appendix A.
Table DELTA-4
Command

DELTA/XDELTA Command Summary
Description
Set Display Mode

Open Location and Display Contents in Prevailing Width
Mode
Open Location and Display Contents in Instruction Mode

ILINEFEED I

Close Current Location, Open Next

IEscl

Open Location and Display Previous Location

ITABI

Open Location and Display Indirect Location

Open Location and Display Contents in ASCII Mode

IRETURN I

Close Current Location

Breakpoint

Proceed from Breakpoint

Step Instruction

Step Instruction Over Subroutine

'string'

Deposit ASCII String

;E
;X

Execute Command String
Load Base Register
Display Value of Expression

Set All Processes Writable (while running DELTA)

Lists Names and Locations of Loaded Executive Images

EXIT

Exit from DELTA debugging session.

DELTA-15

DELTA/XDELTA
[ (Set Display Mode)

[ (Set Display Mode)
Sets the width mode of displays produced by DELT A/XDELTA
commands.

FORMAT
ARGUMENTS

[

mode

mode
Specifies the display mode, as follows:

DESCRIPTION

Mode

Meaning

Byte mode. Subsequent open and display location commands display the
contents of one byte of memory.

Longword mode. Subsequent open and display location commands
display the contents of a longword of memory. This is the default mode.

Word mode. Subsequent open and display location commands display
the contents of one word of memory.

The Set Display Mode command changes the prevailing display width to
byte, word, or longword. The default display width is longword. The display
mode remains in effect until you enter another Set Display Mode command.

EXAMPLE
RO/

00000001 .,

RO/

01 0

[B fJ

DELTA-16

Contents of general register 0 (RO) are displayed using the / command.
The display is the default mode, longword.

Display mode is changed to byte mode using the [B command.

Contents of RO are displayed in byte mode. The least significant byte is
displayed.

DELTA/XDELTA
/ (Open Location and Display Contents in Prevailing Width Mode)

/ (Open Location and Display Contents in
Prevailing Width Mode)
Opens a location and displays its contents in the prevailing display mode.

FORMAT

ARGUMENTS

{pid: ][start-addr-exp][, end-addr-expJI current-contents
{new-exp]

pid
The internal process identification (PID) of a process you want to access. If
you specify zero or do not specify a PID, the default process is the current
process. This argument cannot be used with XDEL TA.
Subsequent open location and display contents commands entered after using
the pid argument display the contents of the location of the specified process
until you specify another PID with this command.
You can obtain the internal PID of processes by running the System Dump
Analyzer Utility (SDA). Use the SDA command SHOW SUMMARY to
determine the external PID. Then use the SDA command SHOW
PROCESS/INDEX to determine the internal PID. Refer to the VMS System
Dump Analyzer Utility Manual for more information about using SDA
commands.

start-addr-exp
The address of the location to be opened, or the start of a range of addresses
to be opened. If not specified, the address displayed is that currently specified
by the symbol Q (last quantity displayed). Use the following syntax to display
a single address location:
start-addr-exp/

You can also specify a register for this parameter. For example, if you want
to view the contents of general register 3 16 (R3), enter the following
DELTA/XDELTA command:
R3/

end-addr-exp
The address of the last location to be opened. Use the following syntax to
display a range of address locations:
start-addr-exp ,end-addr-exp /

You can also specify a range of registers. For example, if you want to view
the contents of general registers 3 16 through 5 16 , enter the following
DEL TA/XDELTA command:
R3,R5/

If you specify an address expression for end-addr-exp that is less than
start-addr-exp, DELTA/XDELTA displays the contents of start-addr-exp
only.

DELTA-17

DELTA/XDELTA
/ (Open Location and Display Contents in Prevailing Width Mode}

current-contents
You do not specify this parameter. It is a hexadecimal value, displayed by
DELTA/XDELTA, of the contents of the location (or range of locations) you
specified with the pid argument and the address expression. It is displayed in
the prevailing width display mode.

new-exp
An expression, the value of which is deposited into the location just
displayed. If you specify new-exp after a range of locations, the new value is
placed only in the last location (specified by end-addr-exp).
When you specify new-exp, terminate the command by pressing IRETURNI.
If you want to deposit a new value into a location in another process (that is,

you specified a PIO other than the current process), you must have already
set the target process to be writable using the ;M command.
If the value you deposit is longer than the last location where it will be

deposited, the new value overwrites subsequent locations. For example, the
values at address locations 202 and 204 are as follows:
202/ 05D053D4
204/ C05405DO

If you deposited the value FFFFFFFFF at address 202, the overflow value

would overwrite the value stored at address location 204, as follows:
202/ 05D053D4
204/ C054FFFF

DESCRIPTION

FFFFFFFFF IRETURNI

The Open Location and Display Contents command opens the location
or range of locations at start-addr-exp and displays current-contents, the
contents of that location, in hexadecimal format. You can place a new value
in the location by specifying an expression. A new value overwrites the last
value displayed.
To display a range of locations, give the start-addr-exp argument as the first
address in the range, followed by a comma, followed by the last address in
the range (the end-addr-exp argument). For example, if you want to display
all locations from 402 to 4FO, the command is as follows:
402,4FO/

This command changes the current address(. symbol) to the contents of the
opened location. A subsequent Close Location command dRETURND does not
change the current address. However, a subsequent Close Current Location
and Open Next command (IEscl or luNEFEEDD executes as follows:

DELTA-18

•

Writes any new-exp specified

•

Closes the location opened by the/ command

•

Adds the number of bytes (defined by the prevailing display width mode)
to the address just opened with the / command

•

Changes the current address to the new value

•

Opens the new location and displays the contents

DELTA/XDELTA
/ (Open Location and Display Contents in Prevailing Width Mode)

The display mode remains hexadecimal until the next Open Location and
Display Contents in Instruction Mode (!) command or Open Location and
Display Contents in ASCII Mode ( ") command.
In DELTA, not XDELTA, you can examine the address space of any existing
process, if your process has CMKRNL privilege. Use pid to specify the
internal PID of the process you want to examine. For example, if you wanted
to view address location 402 in the process with a PID of 20£00364, the
command is as follows:
20E00364:402/

EXAMPLE
RO,RF/00000001
Ri/00000000
R2/00000226
R3/7FF2AD94
R4/000019B4
R5/00000000
R6/7FF2AA49
R7/8001E4DD
R8/7FFED052
R9/7FFED25A
RA/7FFEDDD4
RB/7FFE33DC
RC/7FF2ADCC
RD/7FF2AD70
RE/7FF2AD68
RF/000006A7

Contents of all the general registers RO through RF are displayed.

DELTA-19

DELTA/XDELTA
! (Open Location and Display Contents in Instruction Mode)

! (Open Location and Display Contents in
Instruction Mode)
Displays an instruction and its operands.

FORMAT
ARGUMENTS

{pid:]{start-addr-expj{,end-addr-exp] !

pid
The internal process identification (PID) of a process you want to access. If
you specify zero, or do not specify any PID, the default process is the current
process. This argument cannot be used with XDELTA.
Subsequent open location and display contents commands issued after using
the pid argument display the contents of the location of the specified process
until you specify another PID with this command.
You can obtain the internal PID of processes by running the System Dump
Analyzer Utility (SDA). Use the SDA command SHOW SUMMARY to
determine the external PID. Then use the SDA command SHOW
PROCESS/INDEX: to d~~err'ine the internal PID. ~efer to the VMS System
Dump Analyzer Ut~lity Manual for more information about using SDA
commands.

start-addr-exp
The address of the instruction, or the first address of the range of instructions,
to display. If you do not specify this parameter, the address displayed is that
currently specified by Q (last quantity displayed). When you want to view
just one location, the syntax is as follows:
start-addr-exp!

end-addr-exp
The address of the last instruction in the range to display. When you want to
view several instructions, the syntax is as follows:
start-addr-exp,end-addr-exp!

Each location within the range is displayed with the address, a slash (/), and
the MACRO instruction.

DESCRIPTION

The Open Location and Display Contents in Instruction Mode command
displays the contents of a location or range of locations as a MACRO
instruction. DEL TA/XDEL TA does not make any distinction between
reasonable and unreasonable instructions or instruction streams.
This command does not allow you to modify the contents of the location.
The command sets a flag that causes subsequent Close Current Location and
Display Next (iUNEFEEDD and Open Location and Display Indirect Location
(iTABD commands to display MACRO instructions. You can clear the flag by
using the Open Location and Display Contents (/) command, which displays
the contents of the location as a hexadecimal number, or Open Location and

DELTA-20

DELTA/XDELTA
(Open Location and Display Contents in Instruction Mode)

Display Contents in ASCII Mode (" ), which displays the contents of the
location in ASCII.
When an address appears as an instruction's operand, DELTA/XDELTA
sets the Q symbol to that address. Then enter ! again to go to the address
specified in the instruction operand. DELTA/XDELTA changes Q only
for operands that use program-counter or branch-displacement addressing
modes; Q is not altered for operands that use literal and register addressing
modes. This feature is useful for following branches.

EXAMPLE
69B!BRB
!CLRQ

0000067A 0
-(SP) fJ

The instruction at address 69B is displayed using the ! command.
DELTA/XDELTA displays a branch instruction and sets Q (last address
location displayed) to the branch address 67A.

The instruction at address 67A is displayed using the ! command. The
value of Q is used as the address location.

DELTA-21

DELTA/XDELTA
lLINEFEEDI

(Close Current Location, Open Next)

ILINEFEEDI

(Close Current Location, Open Next)
Closes the currently open location and opens the next location, displaying
its contents.

FORMAT

lLINEFEEDl

DESCRIPTION

The Close Current Location Open Next command closes the currently open
location, then opens the next and displays its contents. This command
accepts no arguments, and thus can only be used to open the next location.
It is useful for examining a series of locations one after another. First, set the
location where you want to start (for example, with the / or (!) command).
Then, press lLINEFEEDl repeatedly to examine each successive location.
The ILINEFEEDl command displays the contents of the next location in the
prevailing display mode and display width. If the current display mode
is hexadecimal (the / command was used) and the display width is word,
the next location displayed is calculated by adding a word to the current
location. Its contents are displayed in hexadecimal. If the current display
mode is instruction, the next location displayed is the next instruction, and
the contents are displayed as a MACRO instruction.
On keyboards without a separate lLINEFEEDl key, press CTRL/J. The lLINEFEEDl
key on LK201 keyboards (VT220, VT240, VT340, and workstation keypoards)
generates different characters and cannot be used for the l LINEFEED I command.
You must use CTRL/J.
This command is useful for displaying a series of MACRO instructions, a
series of register values, or a series of values on the stack.
The values in the symbol Q and the symbol. are changed automatically.

EXAMPLE
6B9 ! CLRQ
- (SP) 0
ILINEFEED I 8
000006BB/CLRQ
- (SP)
\LINEFEED I
000006BD/PUSHL
X1 +002E ILINEFEED I
000006C1/PUSHAL
X1 +003A \LINEFEED\
000006C5/CLRQ
- (SP)
\LINEFEED\
000006C7/PUSHL
#00

Instruction at address 6B9 is displayed using the ! command.

e Five successive instructions are displayed by pressing ILINEFEED I five times.
ILINEFEED I is not echoed on the terminal.

DELTA-22

DELTA/XDELTA
IEscl (Open Location and Display Previous Location)

~ (Open Location and Display Previous Location)
Opens the previous location and displays its contents.

FORMAT
DESCRIPTION

The Open Location and Display Previous Location command decrements the
location counter (.) by the width (in bytes) of the prevailing display mode,
opens that many bytes, and displays the contents on a new line. The address
of the location is displayed on the new line in the prevailing mode, followed
by a slash(/) and the contents of that address.
This command is ignored if the prevailing display mode is instruction mode
(set by the ! command).
Use this command to move backwards through a series of locations. Set the
address where you want to start (for example, with the / command). Then
press IEscl repeatedly to display each preceding location. IEscl is echoed as a
dollar sign($) on the terminal.
On keyboards without a separate IEscl key, press CTRL/3. The IEscl key
on LK201 keyboards (VT220, VT240, VT340, and workstation keyboards)
generates different characters and cannot be used for the IEscl command. You
must use CTRL/3.

EXAMPLE
Ri/00000000 0
R0/00000001

The contents of general register 1 are displayed using the / command.

The contents of general reristr 0, the location prior to general register l,
are displayed by pressing ESC.

DELTA-23

DELTA/XDELTA
ITABI (Open Location and Display Indirect Location)

~ (Open Location and Display Indirect Location)
Opens the location addressed by the contents of the current location and
displays its contents.

FORMAT
DESCRIPTION

The Open Location and Display Indirect Location command opens the
location addressed by the contents of the current location and displays
the contents of the addressed location on a new line. The display is in
the prevailing display mode. This command is useful for examining data
structures that have been placed in a queue, or the operands of instructions.
To execute this command, press ITABL
This command changes the current address (.) to the location displayed.
This command does not affect the display mode.

EXAMPLE
69B ! BRB
0000067A 0 [ill_)
0000067A/CLRQ
-(SP) f)

DELTA-24

The instruction at 69B is displayed using the ! command.
DELTA/XDELTA displays a branch instruction.

The instruction at the address referred to by the branch instruction is
displayed by pressing ITABL DELTA/XDELTA displays the instruction at
address 6 7A.

DELTA/XDELTA
11

(Open Location and Display Contents in ASCII)

(Open Location and Display Contents in ASCII)
Displays the contents of a location as an ASCII string.

FORMAT
ARGUMENTS

[pid:] start-addr-exp[,end-addr-exp}"
pid
The internal process identification (PIO) of a process you want to access. If
you specify zero, or do not specify any PIO, the default process is the current
process. This argument cannot be used with XDELTA.
Subsequent open location and display contents commands issued after using
the pid argument display the contents of the location of the specified process
until you specify another PID with this command.
You can obtain the internal PIO of processes by running the System Dump
Analyzer Utility (SDA). Use the SDA command SHOW SUMMARY to
determine the external PIO. Then use the SDA command SHOW PROCESS
/INDEX to determine the internal PIO. Refer to the VMS System Dump
Analyzer Utility Manual for more information about using SDA commands.

start-addr-exp
The address of the location, or the start of a range of locations, to be
displayed. If you want to view one location, the syntax is as follows:
start-add-exp"

end-addr-exp
The last address within a range of locations to be viewed. If you want to
view a series of locations, the syntax is as follows:
start-add-exp ,end-addr-exp"

DESCRIPTION

The Open Location and Display Contents in ASCII command opens the
location or range of locations at start-addr-exp and displays the contents in
ASCII format. This command does not change the width of the display (byte,
word, longword) from the prevailing mode. If the prevailing mode is word
mode, two ASCII characters are displayed; if byte mode, one character is
displayed.
The display mode remains ASCII until you enter the next Open Location and
Display Contents command(/) or Open Location and Display Contents in
Instruction Mode command (!). These commands change the display mode to
hexadecimal or instruction, respectively.
You can modify the contents of the locations, starting at start-addr-exp, with
the Deposit ASCII string(') command.

DELTA-25

DELTA/XDELTA
" (Open Location and Display Contents in ASCII)

EXAMPLE
235FC2 [W/415A
235FC2"ZA 8
235FC4/PP

0
.---,
LI-N-EF-EED---.1

The current display mode is word (displays one word in hexadecimal).

The " command changes the prevailing display mode to ASCII but does
not affect the width of the display.

The next Close Current Location, Open Next command (ILINEFEEDD
determines the address of the location to open by adding the width, in
bytes, to the value contained in the symbol . (the current address). Then
it opens the number of bytes equal to the width of the prevailing display
mode, which in this example is two bytes.
The ASCII representation of the contents of the location presents the
bytes left to right, while the hexadecimal representation presents them
right to left.

DELTA-26

DELTA/XDELTA
!RETURN!

!RETURN!

(Close Current Location)

(Close Current Location)
Closes a location that has been opened by one of the open location and
display contents commands.

FORMAT

!RETURN!

DESCRIPTION

If you have opened a location with one of the open location and display

contents commands (/, luNEFEEDL IEscl, !, or "), press !RETURN I to close the
location. Use this command to make sure that a specific location has not been
left open with the possibility of being overwritten.
You also press !RETURN! to terminate the following DELTA/XDELTA
commands:

•

•
•

• ;B
• ;M
•
•
•

'string'
;L
EXIT (DELTA only)

You can also use IRETURN I as an ASCII character in a quoted string. Refer to
the Deposit ASCII String command (').

DELTA-27

DELTA/XDELTA
; B (Breakpoint)

;B (Breakpoint)
Shows, sets, and clears breakpoints.

FORMAT
ARGUMENTS

[ addr-exp}{, n}{, display-addr-exp}{, cmd-string-addr}; B

addr-exp
The address where you want the breakpoint.

n
The number to assign to the breakpoint. For DEL TA, the range is from 1
to 8. For XDEL TA, the range is from 2 to 8. If omitted, DEL TA/XDEL TA
assigns the first unused number to the breakpoint; if all numbers are in use,
DELTA/XDEL TA displays the error message, "EH?".

disp/ay-addr-exp
The address of a location, the contents of which are to be displayed
in hexadecimal in the prevailing width mode when the breakpoint is
encountered. If omitted, DELTA/XDEL TA displays only the instruction
that begins at the specified address.

cmd-string-addr
The address of the string of DEL TA/XDEL TA commands to execute when
this breakpoint is encountered. Refer to the Execute Command String (;E)
command. If omitted, DEL TA/XDEL TA executes no commands automatically
and waits for you to enter commands interactively.

DESCRIPTION

The breakpoint command shows, sets, and clears breakpoints. The action
of this command depends on the arguments used with it. Each action is
described below.
Displaying Breakpoints

To show all the breakpoints currently set, enter ;B. For each breakpoint,
DEL TA/XDELTA displays the following information:

DELTA-28

•

Number of the breakpoint

•

Address of the breakpoint

•

Address of a location the contents of which will be displayed when the
breakpoint is encountered

•

Address of the command string associated with this breakpoint (for
complex breakpoints, refer to the section in this Description on Setting
Complex Breakpoints)

DELTA/XDELTA
;B (Breakpoint)

Setting Simple Breakpoints

To set a breakpoint, enter an address expression followed by ;B. Then press
IRETURN Las follows:

addr- exp; BIRETURN I

DELTA/XDELTA sets a breakpoint at the specified location and assigns it the
first available breakpoint number.
When DELTA/XDELTA reaches the breakpoint, it completes the following
actions:
•

Suspends instruction execution.

•

Sets a flag to change the display mode to instruction mode. Any
subsequent Close Current Location, Open Next duNEFEEDD commands
and Open and Display Indirect Location dTABD commands will display
locations as MACRO instructions.

•

The following message is displayed, listing the number of the breakpoint,
the address of the breakpoint, and the instruction stored at the breakpoint
location:
n BRK at address
address/decoded-instruction

For XDELTA running in a multiprocessing environment, the number of the
processor where the breakpoint was taken is also displayed as a 2-digit
hexadecimal number.
After the breakpoint message is displayed, you can enter other
DELTA/XDELTA commands. You can reset the flag that controls the mode in
which instructions are displayed by entering the Open Location and Display
Contents(/) command.
Setting a Breakpoint and Assigning a Number to It

To set a breakpoint and assign it a number, enter the address where you
want the breakpoint, a comma, a single di •t for the breakpoint number, a
semicolon(;), the letter B, and then press RETURN. For DELTA, the breakpoint
number can be from 1 through 8. For XDELTA, breakpoint 1 is reserved for
INI$BRK. Therefore, the XDELTA breakpoint range is from 2 through 8.
For example, if you wanted to set breakpoint 4 at address 408, the command
is as follows:
408 , 4 ; B IRETURN I

DELTA/XDELTA sets a breakpoint at the specified location and assigns it the
specified breakpoint number.
Clearing Breakpoints

To clear a breakpoint, enter zero (0), followed by a comma, the number of the
breakpoint to remove, a semicolon (;), the letter B, and then press IRETURNL
DELTA/XDELTA clears the specified breakpoint. For example, if you wanted
to clear breakpoint 4, the command is as follows:
0 , 4 ; B IRETURN I

DELTA-29

DELTA/XDELTA
;B (B reakpoint)
1

When using XDEL TA, do not clear breakpoint 1. If you do, any calls to
INI$BRK in your program will not result in entry into XDELTA.
Setting Complex Breakpoints

A complex breakpoint completes one or more of the following actions:
•

Always displays the next instruction to be executed

•

Optionally displays the contents of another, specified location

•

Optionally executes a string of DEL TA/XDEL TA commands stored in
memory

To use the complex breakpoint, you must first create the string of DEL TA
commands you want executed. Then deposit those commands at a memory
location with the Deposit ASCII String command(').
To set a complex breakpoint, use the following syntax:
addr-exp,n,display-addr-exp,cmd-string-addr;B

The addr-exp argument is an expression whose value is the location at which
the breakpoint is to be set.
Then argument is the number to assign to this breakpoint. The number <?f
the breakpoint can range from 1 to 8 for DELTA and from 2 to 8 for XDEL TA.
The display-addr-exp argument is an expression, the value of which is the
address of a location whose contents are to be displayed when this breakpoint
is encountered. Omit this argument by specifying zero or two consecutive
commas.
The cmd-string-addr argument is an expression, the value of which is the
address of the string of DEL TA/XDELTA commands to be executed when
this breakpoint is encountered. DEL TA/XDEL TA displays the information
requested before executing the string of commands associated with complex
breakpoints. You must have previously deposited the string of commands
using the ' command or have coded the string into an identifiable location in
your program.

DELTA-30

DELTA/XDELTA
; B {Breakpoint)

EXAMPLE
;B

1 00000690
2 00000699 0
0,2;B f)
;B

1 00000690 •
;P

1 BRK AT 00000690
00000690/CMPL R0,#000009A8 0

Two breakpoints have already been set and are displayed. Using ;B,
DELTA/XDELTA displays each breakpoint number and the address
location of each breakpoint.

Breakpoint 2 is cleared.

Current breakpoints are displayed. Because breakpoint 2 has been
cleared, DELTA/XDELTA displays just breakpoint 1.

Program execution is continued using the ;P command.

At breakpoint 1, program execution halts. DELTA/XDELTA displays the
breakpoint message (the breakpoint number 1 and the address 690) and
the instruction.

DELTA-31

DELTA/XDELTA
; P (Proceed from Breakpoint)

;P (Proceed from Breakpoint)
Continue program execution following a breakpoint.

FORMAT

DESCRIPTION

The Proceed from Breakpoint command continues program execution at the
address contained in the PC of the program. Program execution continues
until the next breakpoint or until program completion.

EXAMPLE
;B

00000699 0

;P 8

2 BRK AT 00000699
00000699/BSBB
000006A2 8

DELTA-32

Current breakpoints are displayed using ;B (breakpoint 2 at address 699).

Program execution is continued using the ;P command.

Program execution halts at breakpoint 2. DEL TA/XDELTA displays the
breakpoint message (the breakpoint number and the address) and the
instruction.

DELTA/XDELTA
;G (GO)

;G (GO)
Continues program execution.

FORMAT
PARAMETERS

address-expression ;G
address-expression
The address at which to continue program execution.

DESCRIPTION

The GO command places the address you specified in address-expression
into the PC and continues execution of the program at that address. It
is useful when you want to skip over specific lines of code or return to a
previous program location to repeat execution.

EXAMPLE
6A2;G

Program execution is started at address 6A2.

DELTA-33

DELTA/XDELTA
S (Step Instruction)

S (Step Instruction)
Executes one instruction and displays the next. If the executed instruction
is a call to a subroutine, it steps into the subroutine and displays the next
instruction to be executed in the subroutine.

FORMAT

DESCRIPTION

The Step Instruction command executes one instruction and displays the next
instruction (in instruction mode) and its address. Use this command to do
single-step instruction execution, including single-step of all instructions in
subroutines. If you want to do single-step instruction execution excluding
single-step of instructions in subroutines, use the 0 command.
The instruction displayed has not yet been executed. This command sets
a flag to change the display mode to instruction mode. Any subsequent
Close Current Location, Open Next (ILINEFEEDD commands and Open and
Display Indirect Location (ITABD commands will display locations as MACRO
instructions. The Open Location and Display Contents(/) command clears
the flag, causing the display mode to revert to longword, hexadecimal mode.
If the instruction being executed is a BSBB, BSBW, JSB, CALLG, or CALLS
instruction, Step moves to the subroutine called by these instructions and
displays the first instruction within the subroutine.

In general, you would move to the instruction where you want to start singlestep execution with the GO (;G) command. Then press S to execute the first
instruction and display the next one.

EXAMPLE
00000690/CMPL
00000697/BEQL
00000699/BSBB
000006A2/PUSHL

DELTA-34

R0,#000009A8
00000690
000006A2
R2 0

so
s8
se

Step program execution is started at address 690. The instruction at
690 is executed, and the next instruction is displayed. Step execution is
continued using S.

At address 697, there is a branch instruction to the instruction at address
69D. However, because the condition (BEQL) is not met, program
execution continues at the next instruction. The next S command is
executed.

At address 699, there is a branch instruction to the instruction at address
6A2, a subroutine. The next S command is executed.

Program execution moves to the subroutine.

DELTA/XDELTA
0 (Step Instruction Over Subroutine)

0 (Step Instruction Over Subroutine)
Executes one instruction, steps over a subroutine by executing it, and
displays the instruction to which the subroutine returns control.

FORMAT

DESCRIPTION

The Step Instruction Over Subroutine command executes one instruction and
displays the address of the next instruction. If the instruction executed is
a call to a subroutine, the subroutine is executed, and the next instruction
displayed is the instruction to which the subroutine returns control. Use this
command to do single-step instruction execution excluding single-step of
instructions within subroutines. If you want to do single-step execution of all
instructions, including those in subroutines, use the S command.
This command sets a flag to change the display mode to instruction mode.
Any subsequent Close Current Location, Open Next dUNEFEEDD commands
and Open and Display Indirect Location (ITABD commands will display
locations as MACRO instructions. The Open Location and Display Contents
(/) command clears the flag, causing the display mode to revert to longword,
hexadecimal mode.
If the executed instruction is BSBB, BSBW, JSB, CALLG, or CALLS,
DELTA/XDEL TA executes the subroutine called by these instructions and
displays the instruction to which the subroutine returns control.
If you set a breakpoint in the subroutine and enter the 0 command, program
execution breaks at the subroutine breakpoint. When you enter a Proceed
command (;P), and program execution returns to the instruction to which the
subroutine returns control, a message is displayed, as follows:
STEPOVER BRK AT nnnnnnnn
instruction

The message informs you that program execution has returned from a
subroutine.
If you are using XDELTA in a multiprocessing environment, the physical
identification number of the processor where the break was taken is also
displayed as a 2-digit hexadecimal number.

DELTA-35

DELTA/XDELTA
0 (Step Instruction Over Subroutine)

EXAMPLE
6D5;B 0
;P 8

1 BRK AT 00000605
;Pf)
00000605/CALLS
#OC,©#7FFEOEOO
PIO= 0006
LOGINTIME= 12:50:29.45
2 BRK AT 00000699
00000699/8888
000006A2
;P 0
1 BRK AT 00000605
00000605/CALLS
#OC,©#7FFEOEOO
;P 0
PIO= 0007
LOGINTIME= 12:50:37.08
2 8RK AT 00000699
00000699/8888
000006A2
o0
1 8RK AT 00000605
00000605/CALLS
#OC,©#7FFEDEOO
;P 0
PID= 0008
LOGINTIME=
12:50:45.64
STEPOVER 8RK AT 00000698 0
00000698/8R8
X1+047A

One breakpoint has been set at address 699 in the main routine. A simple
breakpoint is set at 6D5 using ;B. This breakpoint is in a subroutine.

Program execution continues using ;P.

Program execution stops at breakpoint 1, which is in the subroutine.
DELTA/XDELTA displays the breakpoint message and the instruction at
the new breakpoint. Program execution continues using ;P.

The subroutine completes and displays some output. Program execution
continues until breakpoint 2. DEL TA/XDEL TA displays the breakpoint
message and the breakpoint 2 instruction. Program execution continues
with the ;P command.

Program execution stops at breakpoint 1. Program execution continues
with the ;P command. The subroutine completes execution and displays
the output.

Program execution stops at breakpoint 2. The subroutine is stepped over
to the next instruction using the 0 command.

Program execution stops at breakpoint 1 in the subroutine. Program
execution continues using the ;P command.

G The subroutine completes execution and displays output.
DEL TA/XDEL TA displays a STEPOVER break message that states the 0
command has been completed, returning control at address 69B.

DELTA-36

DELTA/XDELTA
' (Deposit ASCII String)

, (Deposit ASCII String)
Deposits the ASCII string at the current address.

FORMAT
ARGUMENTS

'string'
string
The string of characters to be deposited.

DESCRIPTION

The Deposit ASCII String command deposits string at the current location(.)
in ASCII format. The second apostrophe is required to terminate the string.
All characters typed between the first and second apostrophes are entered as
ASCII character text. Avoid embedding an apostrophe (') within the string
you want to deposit.
When you want to use key commands dLINEFEEDL IRETURNL IEScl, ITABD, press
the key. These commands are entered as text.
This command stores the characters in eight-bit bytes and increments the
current address (.) by one for each character stored.
This command does not change the prevailing display mode.

EXAMPLE
7FFE 1600 I , RO I I LINEFEED 11 LINEFEED I '

The ASCII string "RO/ILINEFEED!ILINEFEEDI" is stored at address 7FFE1600. This
string, if subsequently executed with the ;E command, examines the contents
of general register 0 (the command RO/), then examines two subsequent
registers (using two ILINEFEEDI commands).

DELTA-37

DELTA/XDELTA
;E (Execute Command String)

;E (Execute Command String)
Executes a string of DELTA/XDELTA commands stored in memory.

FORMAT
ARGUMENTS

address-expression; E

address-expression
The address of the string of DELTA/XDELTA commands to execute.

DESCRIPTION

The Execute Command String command executes a string of DELTA/XDEL TA
commands. Load the ASCII text command string to a specific location in
memory using the Deposit ASCII ,String command ('), or code the string in
your program into an identifiable location.
If you want DELTA/XDELTA to proceed with program execution after it
executes the string of commands, end the command string with the ;P
command. If you want DELTA/XDELTA to wait for you to enter a command
after it executes the string of commands, end the command string with a null
byte (a byte containing 0).

XDELTA, but not DELTA, provides two command strings in memory. The
addresses of these command strings are stored in base registers XE and
XF. The string addressed by XE displays the physical page number (PFN)
database for the PFN in XO. The string addressed by XF copies the PFN in RO
to base register XO, then displays the PFN database for that PFN.
You can use the command strings provided with XDELTA to obtain the
following information:

DELTA-38

•

Specified physical page number (PFN)

•

PFN state

•

PFN type

•

PFN reference count

•

PFN backward link or working-set-list index

•

PFN forward link or share count

•

Page table entry (PTE) that points to the PFN

•

PFN backing-store address

•

Virtual block number in the process swap image, the block to which the
page's entry in the SWPVBN array points

DELTA/XDELTA
;E (Execute Command String)

EXAMPLE
7FFE1600,0;X 0
7FFE1600 f)
XO;E 0
R0/00000001 0
Ri/00000000
R2/00000000

The address (7FFE1600) where an ASCII string is stored is placed into
base register 0 using ;X.

DELTA/XDELTA displays the value in XO.

The command string stored at address 7FFE1600, which is to examine the
contents of RO, Rl, and R2 (RO/ILINEFEEDI luNEFEEDD, is executed with ;E.

DELTA/XDELTA executes the commands and displays the contents of
RO, Rl, and R2.

DELTA-39

DELTA/XDELTA
;X (Load Base Register)

;X (Load Base Register)
Places an address in a base register.

FORMAT
ARGUMENTS

address-expression,n;X

address-expression
The address to place in the base register.

n
The number of the base register.

DESCRIPTION

To place an address in a base register, enter an expression followed by a
comma (,), a number from 0 to F16 , a semicolon (;), and the letter X.
DELTA/XDELTA places the address in the base register. DELTA/XDELTA
confirms that the base register is set by displaying the value deposited in the
base register.
For example, the following command places the address 402 in base register
0. DELTA/XDELTA then displays the value in the base register to verify it.
402 ' 0 ; x IRETURN I
00000402

When DELTA/XDEL TA displays an address that is within 2000 16 bytes of an
address stored in a base register, DELTA/XDEL TA displays the base register
identifier (Xn), followed by an offset that gives the address location in relation
to the address stored in the base register. If the address falls outside this
range, DELTA/XDEL TA displays it as a hexadecimal value.
For example, if base register 2 contains 800D046A, and the address
DELTA/XDELTA would display is 800D052E (offset of C4), DELTA/XDELTA
displays that address as X2+C4. DELTA/XDELTA computes relative addresses
for both opened and displayed locations and for addresses that are instruction
operands.
DELTA/XDEL TA provides symbols that make it easy to refer to processor
(Pn), general (Rn), and base registers (Xn). Refer to Section 2.1 for a
description of these symbols.

DELTA-40

DELTA/XDELTA
;X (Load Base Register)

EXAMPLE
00000664/CLRQ
00000200 •
X1 490!CMPL
X1 499!BSBB

-(SP)

200, 1 ;X 0

R0,#000009A8 0
X1+04A2 0

The base address of the program (determined from the map file) is virtual
address 200. The base address is stored in base register 1 with ;X.

DELTA/XDELTA displays the value in base register 1 just loaded, 200.

The instruction at offset 490 is displayed in instruction mode using
the ! command. The address reference is X1+490 (the+ sign is implied
when not specified). DELTA/XDELTA displays the instruction at address
X1+490.

G The instruction at offset 499 is displayed. This instruction is a branch
instruction. DELTA/XDELTA displays the address of the branch in offset
notation.

DELTA-41

DELTA/XDELTA

= (Display Value of Expression)
(Display Value of Expression)
Evaluates an expression and displays its value.

FORMAT
ARGUMENT

expression

expression
The expression to be evaluated.

DESCRIPTION

The Display Value of Expression command evaluates an expression and
displays its value in hexadecimal. The expression can be any valid
DELTA/XDELTA expression. See Section 2.1 for a description of DEL TA
/XDELTA expressions.
All calculations and displays are in hexadecimal in the prevailing length
mode.

EXAMPLE
FF+1=00000100 0
A-1=00000009 f)

DELTA-42

FF 16 and 116 are added together. DELTA/XDELTA displays the sum in
hexadecimal.

116 is subtracted from A16 . DELTA/XDELTA displays the result in
hexadecimal.

DELTA/XDELTA
;M (Set All Processes Writable)

;M (Set All Processes Writable)
Sets the address spaces of all processes to be writable or read-only by
your DELTA process. This command can be used only with DELTA. Use
of this command requires CMKRNL privilege.

FORMAT

n;M

ARGUMENT

DESCRIPTION

Specifies your process privileges for reading and writing at other processes. If
0, your DELTA process can only read locations in other processes; if 1, your
process can read or write any location in any process. If not specified, DELTA
returns the current value of the M (modify) flag (0 or 1).

The Set All Processes Writable command is useful for changing values in the
running system.

NOTE: This is an activity that must be used very carefully during timesharing.
For this reason, your process must have change-mode-to-kernel
(CMKRNL) privilege to use this command. It is safest to use this
command only on a standalone system.

DELTA-43

DELTA/XDELTA
;L (List Names and Locations of Loaded Executive Images}

;L (List Names and Locations of Loaded Executive
Images)
List the names and virtual addresses of all loaded executive images.

FORMAT

DESCRIPTION

Use the ;L command when you are debugging code that resides in system
space. Although you use this command mostly with XDEL TA, you can use
it with DELTA if your process has change-mode-to-executive (CMEXEC)
privilege, and you are running a program in executive mode.
This command lists the names and locations of the loaded modules of the
executive. A loading mechanism maps a number of images of the executive
into system space. The ;L command lists the currently loaded images with
their starting and ending virtual addresses. If you enter ;L before all the
executive image are loaded (for example, at an XDELTA initial breakpoint),
only those images which have been loaded will be displayed.

EXAMPLE
;L

PRIMITIVE_ IO. EXE
SYSTEM_SYNCHRONIZATION.EXE
SYSTEM_PRIMITIVES.EXE

800EAAOO
800EBCOO
800ED400

800EBCOO
800ED400
800F1000

The starting and ending virtual addresses of three loaded executive images
are listed.

DELTA-44

DELTA/XDELTA
EXIT {Exit From DELTA Debugging Session)

EXIT (Exit From DELTA Debugging Session)
Terminates the DELTA debugging session. Use with DELTA only.

FORMAT

EXIT

DESCRIPTION

Use the EXIT command to terminate a DELTA debugging session. You cannot
use EXIT in XDELTA.
You may have to enter EXIT twice, such as when your program terminates
execution via the $EXIT system service or via RET (to DCL).

DELTA-45

Sample DELTA Debug Session

This appendix gives an example of using DELTA. The program, LOGINTIM,
uses the system service SYS$GETJPI to obtain the login times of each process.
Although this is an example of using DELTA, most of the commands in the
example could be used in a XDELTA debug session.
To run this program without error, you need WORLD privilege.
The .LIS file is listed below. Only the offsets and source code are shown.
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
OOOE
0012
0012
0016
0016
0016
0018
001A
001E
0022
0026
0026
002E
002E
0032
0036
003A
043A
043A
0448
0454
045E
045E
0462
0462
0462
0462
0462
0464
0475
047A
047A
047A
0490
0497
0499
049B

1 ;++

2 This sample program uses the wildcard feature of GETJPI to get the
3 ; LOGINTIM for each active process. It outputs the PID and LOGINTIM
4 ; for each and exits when there are NOMOREPROCs.
5 •
6
7

Data areas.

10 DEVNAM: .ASCID /SYS$0UTPUT/

;Output device specifier

12 CHAN:
13
14 ITMLST:
15
16
17
18
19
20
21 TIME:
22
23 OUTLEN:
24 OUTBUF:
25
26 BUF:
27
28 CTRSTR:

.LONG 0

;Assigned output channel

.WORD 8
.WORD JPI$_LOGINTIM
.ADDRESS
TIME
.LONG 0
.LONG 0

;Item list for GETJPI call
Byte length of output buff er
; Specify LOGINTIM item code
; Address of output buff er
; Not interested in return length
;Item list terminator

.QUAD 0

;Buffer to hold LOGINTIM

.LONG 0
.LONG 1024
.ADDRESS BUF
.BLKB 1024

;FAD buffer length
;FAD buffer descriptor
;FAD buffer

.ASCID *!/!_PID= !XW!_LOGINTIME= !%T* ;FAO control string

29
30 PIDADR: .LONG -1
;Wildcard PID control longword
31
32 ;++
33 ; Start of program.
34 .
.WORD
0
;Entry mask
35 S:
$ASSIGN_S DEVNAM,CHAN
;Assign output channel
36
MOVAB
TIME,R2
;Load pointer to LOGINTIM
37
output buff er
38
$GETJPI_S
ITMLST=ITMLST,-;Get LOGINTIM for a process
39 LOOP:
PIDADR=PIDADR
40
RO,#SS$_NOMOREPROC ;Are we done?
CMPL
41
42
BEQL
5$
; If EQL yes
GOT_IT
;Process data for this process
43
BSBB
44
BRB
;Look for another process
LOOP

A-1

Sample DELTA Debug Session

049D
049D
04A1
04A2
04A2
04A2
04A2
04A2
04B9
04B9
04B9
04B9
04DC
04DD
04DD

45
46 5$:
47
48
49 GOT_IT:
50
51
52
53
54
55
56
57

58
59

MOVZBL
RET

#SS$_NORMAL,RO

;Set successful completion code
;Return, no more processes

$FAO_S

CTRSTR,;Format the output data
OUTLEN,OUTBUF,PIDADR,R2
$QIOW_S CHAN=CHAN,;Output to SYS$0UTPUT
FUNC=#IO$_WRITEVBLK,P1=BUF ,P2=0UTLEN
;Done with this process data
RSB
.END S

The .MAP file is listed below. Only the Program Section Synopsis with the
PSECT, MODULE, base address, end address, and length are listed.
+--------------------------+
! Program Section Synopsis !
+--------------------------+
Psect Name

Module Name

Base

. BLANK .

End

Length

00000200 000006E2 000004E3 (
00000200 000006E2 000004E3 (

.MAIN.

1251.)
1251.)

The DEL TA debug session is listed in the following example:
$ DEFINE LIB$DEBUG SYS$LIBRARY:DELTA Ct
$ RUN/DEBUG LOGINTIM fJ
DELTA Version 5.0
00000664/CLRQ
00000200

X1 490!CMPL
X1 499 !BSBB

-(SP)

200, 1;X C)

R0,#000009A8
X1+04A2

. ;B ti)
. ;B Ci)

;P 0

1 BRK AT 00000690
X1+0490/CMPL
R0,#000009A8 R0/00000001 ;~
2 BRK AT 00000699
X1+499/BSBB
X1+04A2
PID= 0000
LOGINTIME= 00:00:00.00 4D

A-2

Sample DELTA Debug Session

Xi+049B/BRB
Xi+047A
;P 4D
i BRK AT 00000690
Xi+0490/CMPL
R0,#000009A8 RO/OOOOOOOi ;P f>
2 BRK AT 00000699
Xi+0499/BSBB
Xi+04A2
PID= OOOi
LOGINTIME= 00:00:00.00
Xi+049B/BRB
Xi+047A
;P
i BRK AT 00000690
Xi+0490/CMPL
R0,#000009A8 CD

a•

;BCD

i 00000690
2 00000699 (!)
O,i;B 4f>
;B 4D

2 00000699 ~
;P ~

2 BRK AT 00000699
Xi+0499/BSBB
Xi+04A2
0
PIO= 0004
LOGINTIME= i2:50:20.40
Xi+049B/BRB
Xi+047A
;P~
2 BRK AT 00000699
Xi+0499/BSBB
Xi+04A2
;P
PIO= 0005
LOGINTIME= i2:50:25.61 fl>
2 BRK AT 00000699
-(SP)9
Xi+0499/BSBB
Xi+04A2
Xi 4B9!CLRQ
!LINEFEED! ~

Xi+04BB/CLRQ
Xi+04BO/PUSHL
Xi+04Ci/PUSHAL
Xi+04C5/CLRQ
Xi+04C7/PUSHL
Xi+04C9/MOVZWL
Xi+04CE/MOVZWL
Xi+0403/PUSHL
Xi+0405/CALLS
;B ~

-(SP)

!LINEFEED!

Xi +002E ILINEFEED I
Xi +003A ILINEFEED I
-(SP) !LINEFEED!
#00 ILINEFEED I
#0030; - (SP) ILINEFEED I
Xi+OOi2,-(SP) ILINEFEEDI
#00 ILINEFEED I
#OC,©#7FFEOEOO

.;B ~

i 00000605
2 00000699
;Pf>

i BRK AT 00000605
Xi+0405/CALLS
#OC,©#7FFEOEOO
;P fD
PIO= 0006
LOGINTIME= i2:50:29.45
2 BRK AT 00000699
Xi+0499/BSBB
Xi+04A2
;P G)
i BRK AT 00000605
Xi+0405/CALLS
#OC,©#7FFEOEOO
;P ~
PIO= 0007
LOGINTIME= i2:50:37.08
2 BRK AT 00000699
Xi+0499/BSBB
Xi+04A2
oG
i BRK AT 00000605

A-3

Sample DELTA Debug Session

X1+04D5/CALLS
#OC,©#7FFEDEOO
PIO= 0008
LOGINTIME=
STEPOVER BRK AT 0000069B ~
X1+049B/BRB
X1+047A
1 00000605
2 00000699 ~
0,2;B .,
0,1;B.,

;P @>

12:50:45.64
;B @D

;BG

;P@

PIO= 0009
PIO= OOOA
PIO= OOOB
PIO= OOOC
EXIT 00000001 $
80187E7E/POPR
#03

LOGINTIME=
LOGINTIME=
LOGINTIME=
LOGINTIME=

12:51:22.51
12:51:30.26
12:51:36.21
12:51:58.86 a&
EXIT~

DELTA is enabled as the debugger.

The example program LOGINTIM is invoked with DEL TA.

0 DELTA displays a version number and the first executable instruction.
The base address of the program (determined from the map file) is virtual
address 200. The base address is placed in base register 1 with ;X. Now
references to an address can use the address offset notation. For example,
a reference to the first instruction is Xl +464 (or base address 200 + offset
464). Also, DELTA displays some address locations as offsets to the base
address.

DELTA displays the value in base register 1 just loaded 200.

The instruction at address 690 is displayed in instruction mode using !.
Its address location is expressed as the base address plus an offset. In the
listing file, the offset is 490. The base address in base register Xl is 200.
The address reference, then, is X1+490. (NOTE: The + sign is implied
when not specified.)
A simple breakpoint is set at that address using the ;B command. The
address reference for ;Bis the . symbol, representing the current address.
X1+490;B would have done the same thing.

The same commands (! command to view the instruction and ;B to set a
breakpoint) are repeated for the instruction at offset 499. When DELTA
displays the instruction (BSBB GOT-1T), it displays the destination of the
branch (GOT-1T) as the address location. DELTA displays the value as
an offset to base register 1.

Program execution is begun using ;P.

Program execution halts at the first breakpoint. DELTA displays the
breakpoint message (1 BRK AT 00000690) with the breakpoint number
1 and the virtual address. The virtual address is 00000690, which is
the base address (200) plus the offset 490. DELTA then displays the
instruction in instruction mode (CMPL R0,#000009A8). The contents of
general register 0 are displayed with the / command. DEL TA displays
the contents of RO, which is 1. Program execution continues using the ;P
command.

0 Program execution halts at breakpoint 2. DELTA displays the breakpoint
message, then the instruction. Step-instruction execution, excluding
instructions in subroutines, is initiated with 0.

A-4

Sample DELTA Debug Session

The subroutine GOT-1T is executed, and the output (PIO and login time)
is displayed.

4D The 0 command halts program execution at the instruction where the
subroutine returns control (BRB LOOP). DELTA displays the instruction
in instruction mode (BRB X1+047A), where X1+047A is the address of the
first instruction in LOOP. Program execution continues with ;P.

48 Breakpoint 1 is encountered again, DELTA displays the breakpoint
message and the instruction. The contents of RO are examined
(/ command) and program execution continues (;P).
41>

Breakpoint 2 is encountered again, DELTA displays the breakpoint
message and the instruction. The subroutine is stepped over again
with the 0 command. The subroutine is executed, and the output
is displayed. The instruction where the subroutine returns control is
displayed. Program execution continues (;P command).

4D Breakpoint 1 is encountered; DELTA displays the breakpoint message and
the instruction.

4D All breakpoints in the program are listed with the ;B command.

e DELTA displays the breakpoints (by breakpoint number) and the address
locations.

4D Breakpoint 1 is cleared using O,[breakpoint #];B. (Never clear breakpoint 1
in XDELTA.)
Qi)

All breakpoints are listed again with ;B command.

DELTA displays breakpoint 2 (breakpoint 1 cleared).

Program execution continues using the ;P command.

fD Breakpoint 2 is encountered. DELTA displays the breakpoint message,
and the instruction. The subroutine is executed with the 0 command
and the subroutine output is displayed. The next instruction where the
subroutine returns control is displayed. Program execution continues with
the ;P command.
f)

Breakpoint 2 is encountered. DELTA displays the breakpoint message
and the instruction. Program execution continues to the next breakpoint
with the ;P command. The subroutine is executed, and the subroutine
output is displayed.

Breakpoint 2 is encountered again. The instruction at offset 4B9 (in the
subroutine) is displayed using !. This instruction is part of the set-up for
the call to the system service QIOW.

Successive address locations are displayed by pressing luNEFEEDI nine
times. These instructions are the remainder of the set up and the call to
the system service QIOW.

A breakpoint at X1+04DS (the current address) is set using the ;B
command. This breakpoint is in the subroutine. The . symbol represents
the current address.

The current breakpoints in the program are listed. The new breakpoint is
assigned breakpoint 1.

Program execution continues with the ;P command.

A-5

Sample DELTA Debug Session

Program execution stops at the new breakpoint 1, which is in the
subroutine GQT_JT. DELTA displays the breakpoint message and the
instruction at the new breakpoint. Program execution continues with the
;P command.

The subroutine completes and displays the output, and program execution
continues until breakpoint 2. DELTA displays the breakpoint message
and the breakpoint 2 instruction. Program execution continues with the
;P command.

G> Program execution stops at breakpoint 1 in the subroutine. Program
execution continues with the ;P command. The subroutine is executed,
and the output is displayed.

G Program execution stops at breakpoint 2. The 0 command is entered to
execute and step over the subroutine.

Program execution stops at breakpoint 1 in the subroutine. Program
execution continues with the ;P command.

G The subroutine completes execution and displays output. DELTA displays
a STEPOVER break message to state that the 0 command has been
completed, returning control at address 69B (an instruction in the main
routine).
~

The instruction where the subroutine returns is displayed, and program
execution is halted. The ;B command is entered to display all current
breakpoints.

The two current breakpoints are listed.

The command 0,2;B clears breakpoint 2.

The command 0,l;B clears breakpoint 1.

G> The ;B command is entered to display all current breakpoints. Because all
breakpoints have been cleared, DELTA does not display any.

G> Program execution continues with the ;P command. Because there are no
longer any breakpoints, the program executes to the end.
~

All current process login times are displayed.

4D Final exit status is displayed.
4B The DELTA EXIT command is entered to terminate the debugging session
and leave DEL TA.

A-6

Index

! command• DELT A-20
· command• DELT A-37
. symbol• DELT A-9
;B command• DELT A-28
;E command• DELT A-38
;G command• DEL T A-33
;L command• DELT A-44
privileges required for• DELT A-14
;M command• DELT A-43
privileges required for• DELT A-14
;P command• DELT A-32
;X command• DELT A-40
= command• DELT A-42
[ command •DELT A-16

A
Address location
changing the value• DELT A-18
closing current• DELT A-22, DELT A-27
command strings (XDELTA)• DELT A-38
displaying, from other processes• DELT A-17
displaying contents of current• DELT A-17
displaying in ASCII• DELT A-25
displaying location pointed to by current
location• DELT A-24
displaying next• DELT A-22
displaying previous• DELT A-23
display range of• DELT A-17
listing for executive images• DELT A-44
of command strings in XDELTA• DELT A-9
PCB• DELT A-9
referencing• DELT A-1 O
using base address and offsets for• DELT A-11
Address symbol, current• DELT A-9
Arithmetic operators• DELT A-1 O
Arithmetic shift• DELT A-10
ASCII
depositing string• DELTA-37
displaying contents in• DELT A-25

B
Base register
loading• DELT A-40
symbol for• DELT A-9
Bootstrap procedures for XDELTA•
DELT A-2 to DELT A-6, DELT A-8
see also individual processors
Breakpoint• DELT A-28 to DELT A-31
clearing• DELTA-28, DELT A-29
complex breakpoints• DELT A-30
initial, in XDELTA• DELT A-7
initial, XDELTA in multiprocessing environment•
DELTA-8
in multiprocessing environment• DELT A-13,
DELTA-35
proceeding from• DELT A-32
proceeding from XDELTA initial• DELT A-8
range for DELTA• DELT A-28
range for XDELTA• DELT A-28
setting• DELT A-28, DELT A-29
showing• DELT A-28
simple• DELT A-28
XDELTA restriction on breakpoint 1 • DELTA-7
Breakpoint command• DELT A-28
Bugcheck information• DELT A-8

c
Close Current Location, Open Next command•
DELTA-22
I command• DELT A-1 7, DELT A-25
Commands
list of• DELTA-15
Complex breakpoint• DELT A-30
Control region space prefix symbol• DELT A-9

D
Debugging
at elevated IPL• DELT A-1
at IPL O•DELTA-1

lndex-1

Index

Debugging (cont'd.)
privileged code• DEL T A-1
user mode programs• DELT A-1
Delta/XDelta Utility
exiting from DELTA• DELT A-2
exiting from XDEL TA• DELT A-8
invoking DELTA• DELT A-1
invoking XDELTA• DELT A-2
Deposit ASCII String command• DELT A-37
Display mode, how to set• DELT A-16
Display Value of Expression command• DELT A-42

E
EH? error message• DELT A-13
ESC command• DELT A-23
ESC key equivalent• DELT A-23
Evaluation precedence• DELT A-9
Execute Command String command• DELT A-38
Executive images, listing names and addresses•
DELTA-44
Exit command• DELT A-45
Exiting
from DELTA• DELT A-2, DELT A-45
from XDELTA• DELT A-8
Expressions
see Numeric expressions
precedence in• DELT A-9

G
General register symbol• DELT A-9, DELT A-13
GO command• DEL T A-33
G symbol• DELT A-9

H
H symbol• DELT A-9

I
IN1$BRK. DELTA-7 DELT A-29
Initial breakpoint in XDELTA• DELTA-7
Instructions, how to display• DELT A-20
I

lndex-2

Internal processor register
see Processor register symbol
Interrupt request for XDELTA• DELTA-6 to DELTA-7
see also individual processors
Invoking
see also Bootstrap procedures for XDELTA
see also Interrupt request for XDELTA
DELTA •DELTA-1
XDELTA• DELT A-2, DELT A-8

LINEFEED key command• DE~ T A-22
LINEFEED key equivalent• DELT A-22
LIS file•DELTA-10, DELTA-11, DELTA-12
List Names and Addresses of Loaded Executive
Images command• DELT A-44
Load Base Register command• DELT A-40

M
MAP file• DELT A-10, DELT A-11, DELT A-12
MicroVAX 2000
bootstrap procedure for XDELTA• DELT A-5
requesting interrupt• DELTA-7
MicroVAX 3500
bootstrap procedure for XDELTA• DELT A-5
requesting interrupt• DELTA-7
MicroVAX 3600
bootstrap procedure for XDELTA• DELT A-5
requesting interrupt• DELTA-7
MicroVAX I
bootstrap procedure for XDELTA• DELT A-5
requesting interrupt• DELTA-7
MicroVAX II
bootstrap procedure for XDELTA• DELT A-5
requesting interrupt• DELTA-7
Multiprocessing environment
initial XDELTA breakpoint• DELT A-8
XDELTA breakpoints• DELT A-13, DELT A-29,
DELTA-35
XDELTA operation •DELT A-13

Index

Numeric expressions• DELT A-9, DELT A-42

Q symbol• DELT A-9

0 command• DELT A-35
Open Location and Display Contents command•
DELTA-17
Open Location and Display Contents in Instruction
Mode command• DELT A-20
Open Location and Display Indirect Location
command• DELT A-24
Open Location and Display Previous Location
command• DELT A-23
Operators, arithmetic• DELT A-10
Output
from DELTA•DELTA-14
from XDELTA•DELTA-14

Redirecting output
DELTA• DELT A-14
XDELTA• DELT A-14
Registers
display contents• DELT A-17
loading base• DELT A-40
symbol for base• DELT A-9
symbol for general• DELT A-13
symbol for processor• DELT A-9
RETURN key command• DELT A-27
Rn symbol• DELT A-9

p
PCB address location• DELT A-9
PCB vector start symbolic address• DELT A-9
PFN
see Physical page number
Physical page number (PFN) •DELT A-38
Pn symbol• DELT A-9
Privileges
DELTA• DELT A-14
XDELTA• DELT A-14
Proceed from Breakpoint command• DELT A-32
Processes, how to set writable• DELT A-43
Processor register symbol• DELT A-9
Processor status longword symbol• DELT A-9,
DELTA-13
Program execution
continuing •DELT A-33
proceeding from breakpoint• DELT A-32
step execution• DELT A-34
step over subroutine execution• DELT A-35
PSL
see Processor status longword symbol

s
SCH$GL_CURPCB•DELTA-9
SCH$GL_PCBVEC•DELTA-9
S command• DELT A-34
Set All Processes Writable command• DELT A-43
Set Display Mode command• DELT A-16
Simple breakpoint• DELT A-28
Stack pointer symbol• DELT A-9, DELT A-13
Step Instruction command• DELT A-34
Step Instruction Over Subroutine command•
DELTA-35
String
depositing ASCII• DELT A-37
Symbols, list of• DELT A-9
System space prefix symbol • DELT A-9

T
TAB key command• DELT A-24
Terminating DELTA
see Exiting
Terminating DELT A/XDELTA commands•
DELTA-27
TU58 console bootstrap procedures• DELT A-6

lndex-3

Index

v
Value (last) displayed symbol• DELT A-9
VAX-11/780
bootstrap procedure for XDEL TA• DEL T A-4
requesting interrupt• DEL T A-6
VAX-11/785
bootstrap procedure for XDEL TA• DEL T A-4
requesting interrupt• DEL T A-6
VAX-11/750
bootstrap procedure for XDELTA• DEL T A-5
bootstrap procedure for XDELTA with TU58
console• DELT A-6
requesting interrupt• DELTA-7
VAX-11/730
bootstrap procedure for XDELTA• DELT A-6
requesting interrupt• DELTA-7
VAX-11/725
bootstrap procedure for XDELTA• DELT A-6
requesting interrupt• DELTA-7
VAX 8200
bootstrap procedure for XDELTA• DEL T A-4
requesting interrupt• DELTA-7
VAX 8250
bootstrap procedure for XDEL TA• DEL T A-4
requesting interrupt• DELTA-7
VAX 8300
bootstrap procedure for XDELTA• DEL T A-4
requesting interrupt• DELTA-7
VAX 8350
bootstrap procedure for XDELTA •DELT A-4
requesting interrupt• DELTA-7
VAX 8530
bootstrap procedure for XDELTA• DELT A-2
requesting interrupt• DELT A-6
VAX 8550
bootstrap procedure for XDELTA• DELT A-2
requesting interrupt• DEL T A-6
VAX 8600
bootstrap procedure for XDELTA• DELT A-3
requesting interrupt• DEL T A-6
VAX 8650
bootstrap procedure for XDEL TA• DEL T A-3
requesting interrupt• DEL T A-6
VAX 8700
bootstrap procedure for XDEL TA• DELT A-2
requesting interrupt• DELT A-6
VAX 8800
bootstrap procedure for XDELTA• DEL T A-2
requesting interrupt• DEL T A-6

lndex-4

V AXstation 2000
bootstrap procedure for XDELTA• DELT A-5
requesting interrupt• DELTA-7

x
X4 symbol• DEL T A-9
X5 symbol• DELT A-9
XE base register• DEL T A-9, DELT A-38
XF base register• DEL T A-9, DEL T A-38
Xn symbol• DEL T A-9

Reader's Comments

VMS Delta/XDelta Utility
Manual
AA-LA86A-TE

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