v2.0

Author: Baron-von-Riedesel

DEBUG.TXT

@@ -858,7 +858,7 @@
  its tty i/o it calls out to the "loader" program, which is responsible to
  route those calls to the OS or handle them on its own.
 
- Once loaded, DebugR can debug programs running in both ring-0 and ring-3
+  Once loaded, DebugR can debug programs running in both ring-0 and ring-3
  protected-mode. Since it doesn't use DOS or BIOS, a few commands implemented
  in the standard Debug/X aren't available: DM, DX, L, N, Q, W, Xx. OTOH, DebugR
  has a few special commands:
@@ -874,14 +874,17 @@
 
  Vectors that can be trapped are vectors 0, 1, 3, 6, 0Dh and 0Eh.
 
- At the debugger prompt, when an address is to be parsed, the prefix '%' will
+  At the debugger prompt, when an address is to be parsed, the prefix '%' will
  tell the debugger to interpret the following offset as linear address.
+  For the a(ssemble and u(nassemble) commands, one may precede the segment part
+ of the range argument with a '$' to make DebugR interpret it as real-mode
+ address and translate the segment to a selector.
 
- Some GPFs occuring in non-privileged code are not handled by DebugR: CLI/STI
+  Some GPFs occuring in non-privileged code are not handled by DebugR: CLI/STI
  executed by programs with IOPL 0; trapped IN/INS/OUT/OUTS instructions; INT XX
  with DPL==0 in the IDT.
 
- DebugR understand commandline option -m, that will instruct it to assume that
+  DebugR understand commandline option -m, that will instruct it to assume that
  exception and IRQ vectors ( interrupts 08-0Fh ) do not overlap.
 
 

HISTORY.TXT

@@ -261,35 +261,37 @@
          intercepted protected-mode int 21h and refuses to quit.
        - another variant - DEBUGXV - may be created. It allows to flip video
          screen between debugger and debuggee.
-    2.00 [3 December 2022]
-       - ensure the correct video page is used when debugger has to display
-         something if the InDOS flag is set AND page swapping is active.
-       - DEBUGX: hook into protected-mode debug interface Int 41h and make
-         debugger visible there.
-       - DEBUGX: restore hooked protected-mode interrupts when client
-         terminates.
-       - DEBUGXV: break if SYSREQ is pressed.
+    2.00 [5 December 2022]
        - fixed: routine int21ah9 did use DOS, even if InDos flag was set.
-       - DEBUGX: added cmdline option /2.
-       - mktables.c: fixed, didn't generate a valid debugtbl.inc.
        - fixed: reading stdin from file wasn't fully MS Debug compatible.
-       - DI cmd may be activated for standard DEBUG.COM.
-       - added a "boot" variant of the debugger - it's supposed to be loaded
-         before DOS by boot loader code.
        - fixed: correctly handle tabs if output is via BIOS.
-       - added a ring0 variant of the debugger - DebugR.bin.
+       - fixed L/W cmds: error msg for read/write drive was crumbled since
+         v1.18.
+       - ensured the correct video page is used when debugger has to display
+         something if the InDOS flag is set AND page swapping is active.
+       - mktables.c fix: didn't generate a valid debugtbl.inc.
+       - added a "boot" variant of the debugger - DebugB.bin.
+       - added a ring0 (PL0) variant of the debugger - DebugR.bin.
+       - DI cmd may be activated for standard DEBUG.COM.
+       - DEBUGX fix: restore hooked protected-mode interrupts when client
+         terminates.
        - DEBUGX fix: c & s cmds finally work with 32-bit offsets.
        - DEBUGX fix, e cmd: generate a GPF if no data alias can be found for
          a code segment ( instead of silently skip the write ).
        - DEBUGX fix: disassembly of [CS:IP] in register dump may have caused
          a GPF in debugger if the memory address was beyond seg limit - 3.
-       - fix L/W cmds: error msg for read/write drive was crumbled since v1.18.
-       - DEBUGX fix, g cmd: if multiple breakpoints with different segment parts
-         were set in protected-mode, hazardous writes may have happened.
+       - DEBUGX fix, g cmd: if multiple breakpoints with different segment
+         parts were set in protected-mode, hazardous writes may have happened.
+       - DEBUGX fix, m cmd: '$' qualifier for the source address segment was
+         rejected.
+       - DEBUGX fix, c & m cmds: if both source and destination segment parts
+         were readonly, the scratch selector was used twice.
+       - DEBUGX: added cmdline option /2.
+       - DEBUGX: hook into protected-mode debug interface Int 41h and make
+         debugger visible there.
        - DEBUGX, a & e cmd: usage of scratch descriptor for readonly segments
          now hidden, so the displayed address' segment part isn't changed.
        - DEBUGX, a & d cmd: default segments are no longer automatically
          converted to selectors during initial switch to protected-mode.
-       - DEBUGX fix, m cmd: '$' qualifier for the source address segment was
-         rejected.
        - DEBUGX: exceptions 0dh/0eh are set/reset on debugger entry/exit.
+       - DEBUGXV: stop in debugger if SYSREQ is pressed.

src/DEBUG.ASM

@@ -930,9 +930,13 @@ prompt1	db @CatStr(!',%PROMPT,!')
 else
 prompt1	db '-'	;main prompt
 endif
+
 prompt2	db ':'	;prompt for register value
-if ?DPMI
+
+if ?PM
+ if ?DPMI
 	db '!'
+ endif
 prompt3	db '#'	;protected-mode prompt
 endif
 
@@ -1388,19 +1392,6 @@ _DATA ends
 
 endif
 
-if EXCCSIP
-_DATA segment
- if EXCCSEIP
-intexceip label dword
- endif
-intexcip  dw 0	;IP if internal exception
- if EXCCSEIP
-		dw 0
- endif
-intexccs  dw 0	;CS if internal exception
-_DATA ends
-endif
-
 if ?DPMI
 
 intcall proto stdcall :word, :word
@@ -1911,10 +1902,14 @@ if LCMDFILE
 @@:
 endif
 	mov cx,1
+ife ?PM
+	mov dx,offset prompt1
+else
+ if ?DPMI
 	mov dx,offset prompt1
-if ?DPMI
 	call ispm_dbe			; debuggee in rm/pm?
 	jz @F
+ endif
 	mov dx,offset prompt3
 @@:
 endif
@@ -5129,7 +5124,8 @@ endif
 ;--- E/SI=src offset, E/DX=end src
 
 dd2:
-	mov [lastcmd],offset lastddd
+;	mov [lastcmd],offset lastddd
+	mov [lastcmd],offset d_cmd
 	call prephack	;set up for faking int vectors 23 and 24
 dd_loop:
 ;	mov ax,[d_addr+4]
@@ -5782,7 +5778,9 @@ if ?DPMI
 	pop dx			;get old MSW
 endif
 
+ife RING0
 	@dprintf "g_cmd: run returned, [spadjust]=%X, [spsav]=%lX", [spadjust], dword ptr ds:[SPSAV]
+endif
 
 if ?PM
 	call getcsattr
@@ -7178,6 +7176,36 @@ error:
 
 IsWriteableBX endp
 
+ if RING0
+
+;--- hack to make 'u' work with a real-mode segment
+
+setscratchsel proc
+	pushad
+	mov bp, sp
+	sub sp, 6
+	sgdt [bp-6]
+	pop ax
+	pop eax
+	movzx ebx, [scratchsel]
+	add ebx, eax
+	movzx eax, word ptr [bp+5*4]	;get DX
+	shl eax, 4
+	push ds
+	mov ds, [wFlat]
+	mov word ptr [ebx+0], -1
+	mov word ptr [ebx+2], ax
+	shr eax, 16
+	mov byte ptr [ebx+4], al
+	mov word ptr [ebx+5], 9Bh
+	mov byte ptr [ebx+7], ah
+	pop ds
+	popad
+	mov bx, [scratchsel]
+	ret
+setscratchsel endp
+ endif
+
  if ?DPMI
 setrmsegm:
 	.286
@@ -8183,7 +8211,8 @@ t_cmd proc
 	cmp ax,'tm'
 	jz tm_cmd
 tt0:
-	mov [lastcmd], offset tt0
+;	mov [lastcmd], offset tt0
+	mov [lastcmd], offset t_cmd
 	call parse_pt	;process arguments
 @@:
 	push cx
@@ -8365,8 +8394,9 @@ endif
 
 trace1 endp
 
-;--- test if memory at CS:E/IP can be written to
+;--- test if memory at CS:E/IP can be written to.
 ;--- return C if not
+;--- used by T cmd.
 ;--- IN: CX=offset for (E)IP
 
 iswriteablecseip proc
@@ -8412,7 +8442,7 @@ ctos_1:
 clear_tf_onstack endp
 
 ;--- Print message about unexpected interrupt, dump registers, and end
-;--- command.  This code is also used by the G and P commands.
+;--- command.  This code is used by G, P and T cmds.
 
 ue_int:
 	mov dl, [run_int]
@@ -8427,17 +8457,21 @@ endif
 @@:
 	jmp cmdloop		;back to the start
 
+;--- "unexpected" exception in real-mode inside debugger
+
 ife RING0
  if CATCHINT07 or CATCHINT0C or CATCHINT0D
 ue_intxx:
   if EXCCSIP
-	pop cs:[intexcip]
-	pop cs:[intexccs]
+	pop cx
+	pop dx
   endif
 	push cs
 	pop ss
 	mov sp,cs:[top_sp]
-	push ax
+	push cx	; ip
+	push dx	; cs
+	push ax	; msg
 
 ;--- fall thru
 
@@ -8447,8 +8481,8 @@ endif
 
 if ?PM or CATCHINT07 or CATCHINT0C or CATCHINT0D
 
-;--- unexpected exception occured inside debugger
-;--- [SP] = msg
+;--- "unexpected" exception occured inside debugger
+;--- [SP] = msg, cs, [e]ip
 
 ue_intx proc
 	cld
@@ -8472,15 +8506,15 @@ if EXCCSIP
 	mov di,offset line_out
 	mov si,offset excloc	; "CS:IP="
 	call copystring
-	mov ax, [intexccs]
+	pop ax
 	call hexword
 	mov al,':'
 	stosb
  if EXCCSEIP
-	mov eax, [intexceip]
+	pop eax
 	call hexdword
  else
-	mov ax, [intexcip]
+	pop ax
 	call hexword
  endif
 	call putsline
@@ -8493,7 +8527,8 @@ endif
 ;--- U command - disassemble.
 
 u_cmd proc
-	mov [lastcmd],offset lastuu
+;	mov [lastcmd],offset lastuu
+	mov [lastcmd],offset u_cmd
 	cmp al,CR
 	je lastuu		;if no address was given
 	sizeprfX		;xor ecx, ecx
@@ -10685,8 +10720,9 @@ glfbx_2:
 getlenforbx endp
 
 ;   getrange - Get address range from input line.
-;    a range consists of either start and end address
-;    or a start address, a 'L' and a length.
+;    a range consists of:
+;       1. a start address: [segment:]start-offset
+;       2. an end-offset or a 'L' followed by a length.
 ;   Entry   AL  First character of range
 ;       SI  Address of next character
 ;       BX  Default segment to use
@@ -10801,6 +10837,23 @@ if ?PM
 	mov bx, cs:[wFlat]
 	jmp ga3
 @@:
+;--- hack for a/u cmds: allow to enter a real-mode address.
+;--- since the debugger cannot handle v86-mode exceptions yet,
+;--- this hack allows to at least (dis)assemble real-mode code parts.
+	cmp al, '$'
+	jnz normseg
+	cmp [lastcmd], offset u_cmd	; u cmd?
+	jz @F
+	cmp [errret], offset cmdloop; a cmd?
+	jz normseg
+@@:
+	lodsb
+	call getword
+	cmp al,':'
+	jnz errorj2
+	call setscratchsel	; set BX to scratchsel
+	jmp ga3
+normseg:
  endif
 endif
 	call getofsforbx

src/TRAPD.INC

@@ -46,13 +46,16 @@ excxx_16:
 	cmp [bInDbg],0				;did the exception occur inside DEBUG?
 	jz isdebuggee16
 if EXCCSIP
-	mov [intexcip], ax
-	mov [intexccs], bx
+	mov si, bx
 endif
 	mov [bp].EXFR16.rIP,offset ue_intx
 	mov bx, [top_sp]
-	sub bx, 2
-	mov [bx], di
+	sub bx, 3*2
+	mov [bx+0], di
+if EXCCSIP
+	mov [bx+2], si
+	mov [bx+4], ax
+endif
 	mov [bp].EXFR16.rSP, bx
 	and byte ptr [bp].EXFR16.rFL+1, not 1	;reset TF
 	pop ax
@@ -128,19 +131,30 @@ exc_xx:
 if EXCCSIP
 ;--- it's assumed that an exception in DEBUG is always in 16-bit code,
 ;--- but this isn't necessarily true, since the debuggee may have hooked
-;--- exceptions. Since v2.0, this is less probably, because DebugX will
+;--- exceptions. Since v2.0, this is less probable, because DebugX will
 ;--- always restore exception handlers 0D/0E on entry.
- if EXCCSEIP
-	mov [intexceip], eax
- else
-	mov [intexcip], ax
- endif
-	mov [intexccs], bx
+	mov si, bx
 endif
 	mov [ebp].EXFR32.rEIP,offset ue_intx
 	movzx ebx,[top_sp]
+if EXCCSIP
+ if EXCCSEIP
+	sub bx, 2*2+4
+ else
+	sub bx, 3*2
+ endif
+else
 	sub bx, 2
-	mov [bx], di
+endif
+	mov [bx+0], di	; msg
+ if EXCCSIP
+	mov [bx+2], si	; cs
+  if EXCCSEIP
+	mov [bx+4], eax
+  else
+	mov [bx+4], ax
+  endif
+ endif
 	mov [ebp].EXFR32.rESP, ebx
 	and byte ptr [ebp].EXFR32.rEFL+1, not 1	;reset TF
 	pop ax