ARCHIVE MY LIFE, CLEAN MYSELF UP: 2006/09

2006-09-18

2006-09-15

UnKG patched

Unlock your Treo keyguard when SMS/MMS arrives.

Get it here.

2006-09-10

Debug Palm OS programs

Palm OS programs can be debugged using Palm Debugger at the ASM level.

BASIC USAGE

Standard method to attach:

Use the debug version of palm simulator or emulator.
Use the highest version of Palm Debugger.
Choose "Emulator" in the "Connection" menu.
Install and RUN your program on the simulator.
Draw on the shortcut according to the doc from palm os.
If the methods on the documents do not work, try to use 1 as the last symbol to draw.
If you enter the debug mode successfully, your program to debug will hang.
Type att and enter in the Debugger window of Palm Debugger
Break! Set your break point and let the program continue.

Another method to attach:

Follow the 1-3 steps of "Standard method to attach"
Run your program till the simulator complain the error
Select "Debug" in the simulator error dialog.
Type att and enter in the Debugger window of Palm Debugger

BASIC DEBUG COMMANDS

Memory commands
1. sc list A6 call stack
2. il disassemble the code, tips:
  - il pc, disassemble from the current PC
  - <enter> after an il command, continue to disassemble
  - il <immediate address>, disassemble from the address
Break point commands
1. br <address> break at address
2. brd display all break points
3. brc clear all break points
Flow control commands
1. g continue the program
2. s step into
3. t step over

UNDERSTAND THE PROGRAM

It's hard to understand the program in the palm debugger as I do not know how to load the Palm OS core system trap symbols into the debugger. Now I use a static disassembler to help me understand the program.

The static analysis tools:

Resource extractor: prc2bin
Disassembler: pilotdis

Usage:

Extract the resources using prc2bin: prc2bin <target.prc>
Disassemble the code segment: pilotdis code0001.bin

FIND YOUR PilotMain()

If the program is compiled using Metrowerks CodeWarrior, you may found the similar asm code at the top of code segment:

PEA	-74(A6)
PEA	-78(A6)
PEA	-4(A6)
TRAP	#15,$A08F = sysTrapSysAppStartup

This fragment indicates the program is starting.

L26	DC.B	'Error launching application'
DC.B	#0
L27	DC.B	'PalmOS_Startup.cpp'

These strings means the code is compiled and linked into PalmOS_Startup.cpp. You can find the file under your CodeWarrior directory.

Between the two parts, you should be able to find the following or similar code:

MOVEA.L	-4(A6),A0
MOVE.W	6(A0),-(A7)
MOVE.L	2(A0),-(A7)
MOVE.W	(A0),-(A7)
JSR	L349
MOVE.L	D0,D5
TST.B	D3
ADDQ.W	#8,A7

Please note the "JSR L349" line, it's a pretty long func call. The distance tells you the func should be your PilotMain. You may also analysis the PalmOS_Startup.cpp to find the PilotMain call point:

/* Call the PilotMain routine and get the result */
result = PilotMain(
    (UInt16) appInfoP->cmd, 
    appInfoP->cmdPBP, 
    appInfoP->launchFlags);

/* Call destrcutor code provided by the compiler */
if (globals_are_setup)
{
    __destroy_global_chain();
}