Copy Link
Add to Bookmark
Report
Chapter 4
CHAPTER 4 - Using Break Point Commands
04.00 Notationnal Conventions
04.01 Introduction
04.02 Setting Break Points
04.03 Manipulating Break Points
04.00 Notationnal Conventions
Section II contains syntax listings for each Soft-ICE command, and
explanations and examples for each command. All numbers are in
hexadecimal; any number can be an expression using +,-,/,*, or
registers. All commands are case-insensitive. Words that are in
italics the command syntax statements must be replaced by an actual
value, rather than typing in the italicized word.
The following notational conventions are used throughout this section
[ ]
Brackets enclose an optional syntax item.
< >
Angle brackets enclose a list of items or choices.
x | y
Vertical bars separate alternatives. Use item x or item y.
count
Count is a byte value that specifies the number of time break
point conditions must be met before the actual break point
occurs. If no count is specified, the default value is 1. Each
time the Soft-ICE window is brought up, the counts are reset to
the values originally specified.
verb
Verb is a value that specifies what type access the break point
will apply to. It can be set to 'R' for reads, 'W' for write RW'
for reads and writes, or 'X' for execute.
address
Address is a value that is made of two 16-bit words, separated by
a colon. The first word is the segment address, and the second
word is the segment offset. The addresses can be constructed of
registers expressions, and symbols. The address may also contain
the special characters "$", ".", and "@". See section 3-8
(Command Syntax) for a description of these special characters.
break-#
Break-number is an identification number that identifies the
break point to use when you are manipulating break points e.g.,
editing, deleting, enabling, or disabling them). The break-number
can be a hexadecimal digit from 0 to F.
list
List is a series of break-# separated by commas or spaces.
mask
Mask is a bitmask that is represented as: combination of 1's,
0's, and X's. X's are don't-care bits.
GT, LT GT and LT
Command qualifiers that unsigned comparisons of values.
Example : BPIO 21 W EQ M 1XXX XXXX
This command will cause a break point to occur if port 21H is written
to with the high order bit set.
04.01 Introduction
Soft-ICE has break point capability that has traditionally only been
available with hardware debuggers. The power and flexibility of the
80386 chip allows advanced break point capability without additional
hardware.
Break points can be set on memory location reads and writes, memory
range reads and writes, program execution and port accesses. Soft-ICE
assigns a one-digit hexadecimal number (0-F) to each break point. This
break-number is used to identify break points when you set delete,
disable, enable, or edit them.
All of Soft-ICE's break points are sticky. That means they don't
disappear automatically after they've been used; you must
intentionally clear or disable them using the BC or the BD commands.
Soft-ICE can handle 16 break points at one time. You can have up to
ten break points of a single type except for break points on memory
location (BPMs), of which you can only have four, due to restrictions
of the 80386 processor.
Break points can be specified with a count parameter. The count
parameter tells Soft-ICE how many times the break point should be
ignored before the break point action occurs.
04.02 Setting Break Points
BPM, BPMB, BPMW, BPMD Set break point on memory access or execution
BPR Set break point on memory range
BPIO Set break point on I/O port access
BPINT Set break point on interrupt
BPX Set/clear break point on execution
CSIP Set CS:IP range qualifier
BPAND Wait for multiple break points to occur
Set break point on memory access or execution
Syntax :
BPM[size]address[verb][qualifier value][C=count]
Size :
B(yte), W(ord), D(oubleword)
The size is actually a range covered by this break point.
For example, if double word is used, and the third byte of
the double is modified, then a break point will occur. The
size is also important if the optional qualifier is
specified (see below).
Verb :
R, W, RW, or X
Qualifier :
EQ(ual), NE (Not Equal), GT (Greater than), LT (Less Than),
M (Mask)
These qualifiers are only applicable to the read and write
break points.
Value
A byte, word, or double word value, depending on the size
specified.
Comments :
The BPM commands allow you to set a break point on memory reads
or writes or execution.
If a verb is not specified, RW is the default. If a size is not
specified, byte is the default.
All of the verb types except X cause the program to execute the
instruction that caused the break point. The current CS:IP will
be the instruction after the break point. If the verb type is X,
the current CS:IP will be the instruction where the break point
was set.
If R is specified, then the break point will occur on read access
and on write operations that do not change the value of the
memory location.
If the verb type is R, W or RW, executing an instruction at the
specified address will not cause the break point action to occur.
Notes :
If BPMW is used, the specified address must start on a word
boundary. If BPMD is used, the specified address must point to a
double word boundary.
Example :
BPM 1234:SI W EQ 10 C=3
This command defines a break point on memory byte access. The
third time that 10 hexadecimal is written to location 1234:SI,
the break point action will occur.
BPM CS:1235 X
This command defines a break point on execution. The break point
action will occur the first time that the instruction at address
CS:1235 is reached. The current CS:IP will be the instruction
where the break point was set.
BPMW DS:FOO W EQ M 0XXX XXXX XXXX XXX1
This command defines a word break point on memory write. The
break point action will occur the first time that location DS:FOO
has a value written to it that sets the high order bit to 0 and
the low order bit to 1. The other bits can be any value.
BPM DS:1000 W GT 5
This command defines a byte break point on memory write. The
break point action will occur the first time that location
DS:1000 has a value written to it that is greater than 5.
Set break point on memory range
Syntax :
BPR start-address end-address [verb] [C=count]
Start-address, end-address :
start-address and end-address specify memory range.
Verb :
R, W, RW, T or TW
Comments :
The BPR command allows you to set a break point across a range of
memory.
All of the verb types except T or TW cause the program to execute
the instruction that caused the break point. The current CS:IP
will be the instruction after the break point.
There is no range break point on execution. If a range break
point is desired on execution, R must be used. An instruction
fetch is considered a read for range break points.
If a verb is not specified, W is the default.
The range break point will degrade system performance in certain
circumstances. Any read or write within the 4K page that contains
the break point range is analyzed by Soft-ICE. This performance
degradation is usually not noticeable, however, degradation could
be extreme in exception cases.
The T and TW verbs enable back trace ranges on the specified
range. They do not cause break points, but instead log
instruction information that can be displayed later with the SHOW
or TRACE commands. For more information on back trace ranges, see
chapter 9.
Example :
BPR B000:0 B000:1000 W
This command defines a break point on memory range. The break
point will occur if there are any writes to the monochrome
adapter video memory region.
Set break point on I/O port access
Syntax :
BPIO port [verb] [qualifier value] [C=count]
Port :
A byte or word value.
Verb :
R (IN), W (OUT), or RW
Qualifier :
EQ(ual), NE (Not Equal), GT (Greater than), LT (Less Than),
M (Mask)
Comments :
The BPIO command allows you to set a break point on I/O port
reads or writes.
If value is specified, it is compared with the actual data value
read or written by the IN or OUT instruction causing the break
point. The value may be a byte or a word. If the I/O is to a byte
port, then the lower 8 bits are used in the comparison.
The instruction pointer (CS:IP) will point to the instruction
after the IN or OUT instruction that caused the break point.
If a verb is not specified, RW is the default.
Example :
BPIO 21 W NE FF
This command defines a break point on I/O port access. The break
point will occur if the interrupt controller one mask register is
written with a value other than FFH.
BPIO 3FE R EQ M 11XX XXXX
This command defines a byte break point on I/O port read. The
break point action will occur the first time that I/0 port 3FE is
read with a value that has the two high order bits set to 1. The
other bits can be any value.
Set break point on interrupt
Syntax :
BPINT int-number [ < AL | AH | AX >= value] [C = count]
Int-number :
Interrupt number from 0 - FF hex
Value :
A byte or a word value
Comments :
The BPINT command allows breaking on the execution of a hardware
or a software interrupt. By optionally qualifying the AX register
with a value, specific DOS or BIOS calls can be easily isolated.
If no value is specified, a break point will occur when the
interrupt specified by int-number occurs. This interrupt can be a
hardware, software, or internal interrupt.
The optional value is compared with the specified register (AH,
AL, or AX) when the interrupt occurs. If the value matches the
specified register, then the break point will occur.
When the break point occurs, if the interrupt was a hardware
interrupt, the instruction pointer (CS:IP) will point to the
first instruction within the interrupt routine. The INT? command
can be used to see where execution was when the interrupt
occurred. If the interrupt was a software interrupt, when the
break point occurs, the instruction pointer (CS:IP) will point to
the INT instruction causing the interrupt.
Example :
BPINT 21 AH=4C
This command defines a break point on interrupt 21H The break
point will occur when DOS function call 4CH (terminate program)
is called.
Set/Clear break point on execution
Syntax :
BPX [address] [C=count]
Comments :
The BPX command allows you to set or clear a point-and-shoot
execution break point in source. When the cursor is in the code
window the address is not required. The execution break point is
set at the address of the current cursor location. If an
execution break point has already been set at the address of the
current cursor location, then the break point is cleared.
If the code window is not visible or the cursor is not in the
code window then the address must be specified. If an offset only
is specified then the current CS register value used as the
segment.
Technical Note :
BPX uses an interrupt 3 style of break point unless the specified
address is ROM. This is used instead of a break point register to
make more execution break points available. If your circumstances
require the use of a break point register for some reason (code
not loaded yet for example) you can set an execution break point
with the BPM command.
Example :
BPX.1234
This sets an execution break point at source line 1234.
Set CS:IP range qualifier
Syntax :
CSIP [OFF | [NOT] start-address end-address]
NOT :
When NOT is specified, the break point will only occur if
the CS:IP pointer is outside the specified range.
OFF :
Turns off CS:IP checking
Comments :
The CSIP command causes a break point to be dependent upon the
location of the instruction pointer when the break point
conditions are met. This function is often useful when a program
is suspected of accidentally modifying code outside of its
boundaries.
When break point conditions are met, the CS:IP registers are
compared with a specified range. If they are within the range,
the break point is activated. To activate the break point when
CS:IP is outside the range, use the NOT parameter.
When a CSIP range is specified, it applies to ALL break points
that are currently active.
If no parameters are specified, the current CSIP range is
displayed.
Example :
CSIP NOT F000:0 FFFF:0
This command causes the break points to occur only the CS:IP is
NOT in the ROM BIOS when the break point conditions are met.
Wait for multiple break points to occur
Syntax :
BPAND list | * | OFF
List :
A series of break-numbers separated by commas or spaces
* :
ANDs together all break points
Comments :
The BPAND command does a logical AND of two or more break points,
activating the break point only when conditions for all break
points are met.
Sometimes conditions arise when you don't want a break point to
occur until several different conditions are met. The BPAND
command allows specifying two or more break points that must
occur before the action is generated. This function allows more
complex break point conditions to be set.
Each time the BPAND command is used, the specified break point
numbers are added to the list until BPAND OFF is used.
You can tell which of the break-numbers are ANDed together by
listing the break points with the BL command. The break points
that are ANDed together will have an ampersand (&) after their
break-number.
Once break points have been ANDed together, each remains ANDed
until it is cleared, or until BPAND is turned off.
Example :
BPAND 0,2,3
This command causes the conditions of the break points 0, 2, and
3 to be logically tied together. The break occurs only when the
conditions of all three are met. For example, if the conditions
of break points 2 and 3 have both been met at least once, but the
conditions of break point 0 have not been met at all yet, then
the action will not occur until break point 0 conditions are met.
04.03 Manipulating Break Points
Soft-ICE provides several commands for manipulating break points.
Manipulation commands allow listing, modifying, deleting, enabling,
and disabling of break points. Break points are identified by
break-numbers which are hexadecimal digits from 0 to F. The break
point manipulation commands are:
BD Disable break points
BE Enable break points
BL List break points
BPE Edit break point
BPT Use break point as a template
BC Clear break points
Disable break points
Syntax :
BD list | *
List :
A series of break-numbers separated by commas or spaces
* :
Disables all break points
Comments :
The BD command is used to temporarily deactivate break points.
The break points can be reactivated with the BE (Enable break
points) command.
You can tell which of the break-numbers are disabled by listing
the break points with the BL command. The break points that are
disabled will have an asterisk (*) after their break-number.
Example :
BD 1,3
This command temporarily disables break points 1 and 3.
Enable break points
Syntax :
BE list | *
List :
A series of break-numbers separated by commas or spaces
* :
Enables all break points
Comments :
The BE command is used to reactivate break points that were
deactivated by the BD (Disable break points) command.
Note that a break point is automatically enabled when defined.
Example :
BE 3 his command enables break point 3.
List break points
Syntax :
BL
Comments :
The BL command displays all break points that are currently set.
For each break point, BL lists the break-number, break point
conditions, break point state, and count.
The state of a break point is either enabled or disabled. If the
break point is disabled, an asterisk (*) is displayed after its
break-number. If an enabled break point was used in a BPAND
command, an ampersand (&) is displayed after its break-number.
The break point that most recently caused an action to occur is
highlighted.
The BL command has no parameters.
Example :
BL
This command displays all the break points that have been
defined. A sample display, which shows four break points,
follows:
0) BPMB 1234:0000 W EQ 0010 C=03
1)*BPR B000:0000 B000:1000 W C=01
2) BPIO 0021 W NE 00FF C=01
3) BPINT 21 AH=4C C=01
Note that in this example, break point 1 is preceded with an
asterisk (*), showing that it has been disabled.
Edit break point
Syntax :
BPE break-number
Comments :
The BPE command loads the break point description into the edit
line for modification. The command can then be edited using the
editing keys, and re-entered by pressing the ENTER . This command
offers a quick way to modify the parameters of an existing break
point.
Example :
BPE 1
This command moves a description of break point 1 into the edit
line and removes break point 1. Pressing the ENTER key will cause
the break point to be re-entered.
Use break point as a template
Syntax :
BPT break-number
Comments :
The BPT command uses an existing break point description as a
template for a new break point.
A description of the existing break point is loaded into the edit
line. The break point referenced by break-number is not altered.
This command offers a quick way to create a new break point that
is similar to an existing break point.
Example :
BPT 3
This command moves a template of break point 3 into the edit
line. When the ENTER key is pressed, a new break point is added.
Clear break points
Syntax :
BC list | *
List :
A series of break-numbers separated by commas or spaces
* :
ANDs together all break points
Comments :
The BC command is used to permanently delete one or more break
points.
Example :
BC *
This command clears all break points.
