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Debug only Privileged Mode Sets a data breakpoint. Syntax | |
DATAB virtaddr [:pin|@] [byte_count] [count] [loudness] [cmdlist]
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Data breakpoints "break" when the indicated address is written to. The
debugger stops at the instruction that is about to perform the write
operation. The DATAB command is used to set process-local and global (system-wide) data breakpoints. Setting a breakpoint for another process is implemented so that it
appears the target process set the breakpoint itself. Therefore, when
the target process encounters the breakpoint, it enters Debug with
its output directed to the LDEV associated with that process. Parameters | |
- virtaddr
The virtual address at which to set the data breakpoint. Virtaddr can be a short pointer, a long pointer, or a full
logical code pointer. - pin | @
The process identification number (PIN) of the process for which the breakpoint
is to be set. If omitted, the breakpoint is set for the current
process. The character "@" can be used to set a global breakpoint at which
all processes stop. - byte_count
Byte_count specifies the number of bytes
to "protect" with the data breakpoint.
If no value is given, one byte is assumed. - count
Count has a twofold meaning: it specifies to break every nth time the
breakpoint is encountered, and it is used to set permanent/temporary
breakpoints. count is positive, the
breakpoint is permanent. If count is negative,
the breakpoint is temporary and is deleted as soon as the process
attempts to modify the protected address. For example, a count of 4 means
break every fourth time the protected address range is modified;
a count of -4 means break on the fourth time, and
immediately delete the breakpoint. If count is omitted, +1 is used,
which breaks every time the address range is written to, permanently.
- loudness
Either LOUD or QUIET. If QUIET is selected the debugger does not
print out a message that the breakpoint has been hit. This is useful for
performing a command list a great number of times before stopping without
being inundated with screen after screen of breakpoint messages. These
keywords may be abbreviated as desired. The default value is LOUD. - cmdlist
A single Debug command or
a list of Debug commands that are executed immediately when the
breakpoint is encountered.
Command lists for breakpoints are limited to
80 characters. (If this is too few characters, write a macro and have the
command list invoke the macro). Cmdlist has the form:
CMD1
{ CMD1; CMD2; CMD3; ... }
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Examples | |
$ nmdebug > datab dp+c14,8
added: [1] 49.40150c68 for 8 bytes
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Set a data breakpoint at DP+c14. (We will assume it's a global variable.)
Protect 8 bytes starting at that address.
$ nmdebug > datab r24,c4,-1
added: T[2] 49.401515d4 for c4 bytes
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Set a temporary data breakpoint at the address pointed to by general
register 24. For this example we assume that r24 contains a pointer to
the user's dynamic heap space. Protect c4 bytes starting at that address.
The breakpoint is a temporary breakpoint (that is, it is deleted after it is
encountered for the first time).
$ nmdebug > databl
[1] 49.40150c68 for 8 bytes
T[2] 49.401515d4 for c4 bytes
count 0/1
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Now list the data breakpoints we have just set. |
