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Debug only Arms/disarms/lists various traps that are monitored by Debug. Syntax | |
TRAP [LIST]
TRAP [trap-name] [option]
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Parameters | |
- trap-name
Traps can be classified into several classes. The trap names for each
class are presented together. In general, this parameter specifies
which trap to arm, disarm, or list. Only enough characters to make the
name recognizable are required. Hardware Traps These are traps that are documented in the Precision Architecture Control Document (ACD). They are trapped directly by the hardware. - BRANCH
The BRANCH trap is the taken branch trap. Any time a branch instruction is executed the debugger stops.
MPE XL X-Traps These traps correspond to the MPE XL user
intrinsics of similar name. (Refer to the MPE XL Intrinsics Reference Manual (32650-90028) for descriptions of the each of these traps.) By arming these traps, the debugger obtains control of the process before the system trap mechanism. You may have the system ignore the trap (pretend it never happened) or process it as if
the debugger had not been notified. To have the trap ignored use the C[ontinue]IGNORE command. Typing C[ontinue] or
C[ontinue] NOIGNORE causes the trap subsystem to process the trap as if Debug has not been notified. - XARITHMETIC
The trap mask indicating the cause of the trap is displayed. - XCODE
The code trap number is displayed. - XLIBRARY
Not implemented. - XSYSTEM
Not implemented.
Refer to the MPE XL Intrinsics Reference Manual (32650-90028) for a description of the format of the various trap masks and codes displayed by Debug when one of the above traps is encountered. Trace Traps The currently defined trace events are based on compiler generated
breakpoints. These breakpoints are inserted into the code by the
compilers only if the symbolic debug compiler option is used. If
the debugger arms any of these events, it stops at the
indicated event. - BEGIN_PROCEDURE
Stop at the entry to procedure. - END_PROCEDURE
Stop at the exit from procedure. - LABELS
Stop at all labels. - STATEMENTS
Stop at each source statement (requires compiler support). - EXIT_PROGRAM
Stop at the program exit point. - ENTER_PROGRAM
Stop at the program entry point. - TRACE_ALL
All of the trace events.
- option
Three options are supported. If none is given, LIST is assumed. - LIST
List the current setting of the trap(s). - ARM
Arm the indicated trap(s). - DISARM
Disarm the indicated trap(s).
Examples | |
$nmdebug > trap list
XLIBRARY DISABLED
XARITHMETIC DISABLED
XSYSTEM DISABLED
XCODE DISABLED
BRANCH DISABLED
BEGIN_PROCEDURE DISABLED
END_PROCEDURE DISABLED
LABELS DISABLED
STATEMENTS DISABLED
ENTER_PROGRAM DISABLED
EXIT_PROGRAM DISABLED
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List the status of all the defined traps (initial status is disabled).
$nmdebug > trap branch arm
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Arm the branch taken trap and the arithmetic traps.
$nmdebug > trap
XLIBRARY DISABLED
XARITHMETIC DISABLED
XSYSTEM DISABLED
XCODE DISABLED
BRANCH DISABLED
BEGIN_PROCEDURE DISABLED
END_PROCEDURE ARMED
LABELS DISABLED
STATEMENTS DISABLED
ENTER_PROGRAM DISABLED
EXIT_PROGRAM DISABLED
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Show the status of the traps.
$nmdebug > c
Branch Taken at: 6a8.00005d84 processstudent+$60
to: 6a8.000056b8 lr_wa_10
$nmdebug > c
Branch Taken at: 6a8.00005708 lr_wa_1+$8
to: 6a8.00005d88 processstudent+$64
$nmdebug > c
Branch Taken at: 6a8.00005d94 processstudent+$70
to: 6a8.00005990 ?_start+$3c
$nmdebug > c
Branch Taken at: 6a8.000059ac ?_start+$58
to: a.fff7b004
$nmdebug > c
Branch Taken at: a.fff7b024
to: 730.00015c6c ?average
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The above example shows the use of the branch taken trap. Every time any form of branch instruction is executed, Debug stops just before the branch occurs.
$nmdebug > trap xari arm
$nmdebug > trap xari list
XLIBRARY ARMED
$nmdebug > c
XARI Trap at: 730.00015d38 average+$b0
trap mask = 00000002
$nmdebug > wl pc,#13
GRP $730.15d38
$nmdebug > dc pc-20,#13
GRP $730.15d18
00015d18 average+$90 b6b60802 ADDIO 1,21,22
00015d1c average+$94 6bd63f81 STW 22,-64(0,30)
00015d20 average+$98 e81f1f77 B,N average+$58
00015d24 average+$9c 20000009 ** Stmt 9
00015d28 average+$a0 4bc13ee9 LDW -140(0,30),1
00015d2c average+$a4 b4390fff ADDIO -1,1,25 /* Trap occurred in
00015d30 average+$a8 ebff0595 BL divoI,31 /* <-- this routine.
00015d34 average+$ac 4bda3f89 LDW -60(0,30),26
00015d38 average+$b0 4bdf3ed9 LDW -148(0,30),31 /* <-- PC is here
00015d3c average+$b4 6bfd0000 STW 29,0(0,31)
00015d40 average+$b8 e840c000 BV 0(2)
00015d44 average+$bc 37de3f31 LDO -104(30),30
$nmdebug > dr r29
R29=$0
$nmdebug > mr r29 4
R29=$0 := $4
$nmdebug > c ignore
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The above example starts by arming the XARI trap. The process is
allowed to run. During execution, an arithmetic trap was detected.
Debug stops to allow the user to inspect the state of the process.
After viewing the code, it can be seen that the trap occurred in the
divoI millicode routine. By analyzing the trap mask
it is determined that the trap was caused by attempting to divide by
zero. The millicode divide routine returns the result of its operation
in general register 29. After looking at the source code, the bug in the program was discovered. It was determined that at this point in
process execution, the result of the divide should have been "4".
The millicode return register is updated with the correct value.
The continue command with the IGNORE option is issued to resume the
process as if the trap never happened. (If the IGNORE option had
been specified, the process would have been terminated by the trap subsystem.) |
