For the last couple of years I’ve been working (on and off) on reverse engineering a DOS game from my childhood - Maupiti Island.

I’ve still haven’t made enough progress, but the other evening I was playing around with the disassembler Cutter, just to see what the newer version are like, and noticed it’s showing me a group of strings Ghidra and IDA didn’t.

Symbols

These strings looked like debug symbols especially after seeing they mention source code files.
And… turns out they actually are!

Googling around, I found thet debug information for MZ executables was usually stuck at the end of the file, and this stack overflow answer pointed me to a page that had the structure of the debug information header produced by Borland Tools.

Format of Borland debugging information header (following load image):
Offset	Size	Description	)
 00h	WORD	signature 52FBh
 02h	WORD	version ID
 04h	DWORD	size of name pool in bytes
 08h	WORD	number of names in name pool
 0Ah	WORD	number of type entries
 0Ch	WORD	number of structure members
 0Eh	WORD	number of symbols
 10h	WORD	number of global symbols
 12h	WORD	number of modules
 14h	WORD	number of locals (optional)
 16h	WORD	number of scopes in table
 18h	WORD	number of line-number entries
 1Ah	WORD	number of include files
 1Ch	WORD	number of segment records
 1Eh	WORD	number of segment/file correlations
 20h	DWORD	size of load image after removing uninitialized data and debug
		  information
 24h	DWORD	debugger hook; pointer into debugged program whose meaning
		  depends on program flags
 28h	BYTE	program flags
		bit 0: case-sensitive link
		bit 1: pascal overlay program
 29h	WORD	no longer used
 2Bh	WORD	size of data pool in bytes
 2Dh	BYTE	padding
 2Eh	WORD	size of following header extension (currently 00h, 10h, or 20h)
 30h	WORD	number of classes
 32h	WORD	number of parents
 34h	WORD	number of global classes (currently unused)
 36h	WORD	number of overloads (currently unused)
 38h	WORD	number of scope classes
 3Ah	WORD	number of module classes
 3Ch	WORD	number of coverage offsets
 3Eh	DWORD	offset relative to symbol base of name pool
 42h	WORD	number of browser information records
 44h	WORD	number of optimized symbol records
 46h	WORD	debugging flags
 48h  8 BYTEs	padding
Note:	additional information on the Borland debugging info may be found in
	  Borland's Open Architecture Handbook
SeeAlso: #01600

Pretty well documented. And the extra data at the end of the game’s executable did start with the 52FBh magic number!

Did some more googling I found Borland’s Open Architecture Handbook and started writing a template for 010 Editor to help parse the information and see if it’s actually useful.

After playing around with it for an evening, I got to a point where I see all the symbol debug information for functions and globals!

010Editor

I’ll probably write a Ghidra script to use this info, but for now I’m happy to manually modify the labels when I need to.

If anyone is interested in the template for 010 Editor, it is here. not a full MZ template as it only parses whatever is needed to parse Borland’s debug information.

The debug info in the games isn’t complete, but had enough to clarify some things I was struggling with, and probably saved my a lot of time.

Hope you find this useful :)