The Kernel debugger included with the OS/2 Toolkit is a low-level debugger oriented toward system and device-driver debugging. The kernel debugger can assist in debugging Workplace Shell applications until higher-level debuggers, such as IPMD, can provide adequate debugging functions in complex situations.
When the Kernel debugger is installed, two files are copied to the root directory of the boot drive: OS2KRNL and OS2KRNL.SYM. OS2KRNL is a hidden file, which will be renamed OS2KRNL.RTL when debugging is active. Because the Kernel debugger supports symbolic debugging, numerous symbol files (.SYM files) are copied to the \OS2\DEBUG\DLL directory. These symbol files contain information on symbols defined and used by OS/2.
To make symbols defined in your Workplace Shell application available to the Kernel debugger, use the MAPSYM program. MAPSYM converts the .MAP file generated by the linker to a .SYM file. The .SYM file should reside in the same directory as the .EXE or .DLL executable file it represents and it should have the same name.
When using the Kernel debugger, it is a good idea to use the functionprefix= modifier in the IDL file implementation statement. There are three reasons for this:
In the following sample code, the methods generated are called Dogdisplay and Dogbark.
/****************************************************************//* By adding the functionprefix= modifier to the class, all */
/* methods defined will be unique, for example, Dogbark. */
/* This is useful when debugging, because every method in the */
/* class will start with this prefix and will not be static. */
/****************************************************************/
#ifndef dogdbug_idl
#define dogdbug_idl
#include <somobj.idl>
interface Dog : SOMObject
{
attribute string breed;
// The breed for the dog
void display();
// Display characteristics for this dog
void bark();
// Have the dog bark
#ifdef __SOMIDL__
implementation
{
releaseorder: _get_breed, _set_breed, display, bark;
//# Class modifiers
functionprefix = Dog; // This will help when debugging
callstyle = oidl;
majorversion = 1;
minorversion = 2;
}; #endif /* __SOMIDL__ */
}; #endif
As soon as the Kernel debugger is active, use the .p command to display process information. The Process ID (pid) of the Shell process and the Workplace process can be located quickly using this command. The following figure shows an example of the information you obtain when using the .p command:
## .p
Slot Pid Ppid Csid Ord Sta Pri pTSD pPTDA pTCB Disp SG Name
0001 0001 0000 0000 0001 blk 0100 ffe3a000 ffe3c7d4 ffe3c620 1e7c 00 *ager
0002 0001 0000 0000 0002 blk 0200 7b92a000 ffe3c7d4 7bb28020 1f3c 00 *tsd
0003 0001 0000 0000 0003 blk 0200 7b92c000 ffe3c7d4 7bb281d4 1f50 00 *ctxh
0004 0001 0000 0000 0004 blk 081f 7b92e000 ffe3c7d4 7bb28388 1f48 00 *kdb
0005 0001 0000 0000 0005 blk 0800 7b930000 ffe3c7d4 7bb2853c 1f20 00 *lazyw
0006 0001 0000 0000 0006 blk 0800 7b932000 ffe3c7d4 7bb286f0 1f3c 00 *asyncr
0008 0005 0001 0005 0001 blk 0200 7b936000 7bb458a4 7bb28a58 00 cmd
*0009# 0006 0005 0006 0001旼컴컴컴컴컴컴컴컴컴컴컴컴커7bb28c0c 1eb8 01 pmshell
000d 0006 0005 0006 0002� �7bb292dc 01 pmshell
000e 0006 0005 0006 0003� In this example, �7bb29490 01 pmshell
000f 0006 0005 0006 0004� Pid #6 is the first �7bb29644 01 pmshell
0010 0006 0005 0006 0005� PMSHELL process, or �7bb297f8 01 pmshell
0007 0006 0005 0006 0006� the "Shell process". �7bb288a4 1ecc 01 pmshell
0013 0006 0005 0006 0007� �7bb29d14 01 pmshell
0015 0006 0005 0006 0008읕컴컴컴컴컴컴컴컴컴컴컴컴켸7bb2a07c 01 pmshell
0016 0006 0005 0006 0009 blk 0200 7b952000 7bb44020 7bb2a230 01 pmshell
0017 0006 0005 0006 000a blk 0800 7b954000 7bb44020 7bb2a3e4 01 pmshell
0018 0006 0005 0006 000b blk 0800 7b956000 7bb44020 7bb2a598 01 pmshell
0019 0006 0005 0006 000c blk 0800 7b958000 7bb44020 7bb2a74c 01 pmshell
001a 0006 0005 0006 000d blk 0804 7b95a000 7bb44020 7bb2a900 01 pmshell
001b 0006 0005 0006 000e blk 0804 7b95c000 7bb44020 7bb2aab4 01 pmshell
001c 0006 0005 0006 000f blk 0500 7b95e000 7bb44020 7bb2ac68 01 pmshell
001d 0006 0005 0006 0010 blk 0800 7b960000 7bb44020 7bb2ae1c 1bb0 01 pmshell
Slot Pid Ppid Csid Ord Sta Pri pTSD pPTDA pTCB Disp SG Name
001e 0006 0005 0006 0011 blk 0800 7b962000 7bb44020 7bb2afd0 1b8c 01 pmshell
001f 0006 0005 0006 0012 blk 0200 7b964000 7bb44020 7bb2b184 01 pmshell
000a 0003 0000 0003 0001 blk 0200 7b93a000 7bb4484c 7bb28dc0 00 lanmsgex
000b 0004 0000 0004 0001 blk 0200 7b93c000 7bb45078 7bb28f74 00 lsdaemon
000c 0007 0006 0007 0001 blk 0800 7b93e000 7bb460d0 7bb29128 00 harderr
0011 0007 0006 0007 0002 blk 0800 7b948000 7bb460d0 7bb299ac 00 harderr
0012 0007 0006 0007 0003 blk 0800 7b94a000 7bb460d0 7bb29b60 00 harderr
0014 0008 0000 0008 0001 blk 0200 7b94e000 7bb468fc 7bb29ec8 01 stoplan
0020 0009 0006 0009 0001 blk 0500 7b966000 7bb47128 7bb2b338 1eb8 10 pmshell
0021 0009 0006 0009 0002 blk 0200 7b968000 7bb47128 7bb2b4ec 10 pmshell
0022 0009 0006 0009 0003旼컴컴컴컴컴컴컴컴컴컴컴컴커7bb2b6a0 1eb8 10 pmshell
0023 0009 0006 0009 0004� �7bb2b854 1ecc 10 pmshell
0024 0009 0006 0009 0005� In this example, �7bb2ba08 10 pmshell
0025 0009 0006 0009 0006� Pid #9 is the second �7bb2bbbc 10 pmshell
0026 0009 0006 0009 0007� PMSHELL process, or �7bb2bd70 10 pmshell
0027 0009 0006 0009 0008� the "Workplace �7bb2bf24 10 pmshell
0028 0009 0006 0009 0009� process". �7bb2c0d8 10 pmshell
002a 0009 0006 0009 000b� �7bb2c440 1eac 10 pmshell
002b 0009 0006 0009 000c읕컴컴컴컴컴컴컴컴컴컴컴컴켸7bb2c5f4 1eb8 10 pmshell
0029 000a 0006 000a 0001 blk 0200 7b978000 7bb47954 7bb2c28c 11 cmd
002c 000b 0006 000b 0001 blk 0200 7b97e000 7bb48180 7bb2c7a8 12 cmd
002f 001f 0006 001f 0001 blk 0200 7b984000 7bb4a230 7bb2ccc4 15 cmd
Slot Pid Ppid Csid Ord Sta Pri pTSD pPTDA pTCB Disp SG Name
0030 001d 0006 001d 0001 blk 0200 7b986000 7bb49a04 7bb2ce78 13 cmd
##
The Kernel debug command VSF * sets the trap vectors. This allows traps in the Workplace Shell application to be located quickly. The Kernel debugger stops on the instruction that is about to cause a trap when these vectors are set. In this way, it is possible to examine the stack and registers to determine the cause of the trap.