Re: [hatari-devel] Hatari debugger questions

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 26/02/2018 à 11:46, Nicolas Pomarède a écrit :

> > Further, when I change the pc value and then enter 's' my expectation is
> > that the first command at the new pc location is executed. What happens
> > instead is that the instruction at the previous (old) pc location is
> > executed.
> >
> > Am I doing something wrong? What do I have to do in order to change the
> > pc value and then to single-step starting at the new pc location?
>
> I will write a small asm test code to check if I can reproduce this.

It seems to work for me. Consider this small example :

        moveq   #0,d0
        moveq   #0,d1
        moveq   #0,d2

        moveq   #1,d1
        moveq   #2,d2
        moveq   #3,d3

        nop

attached is the resulting .prg.

Now, run hatari and press alt+pause to enter debugger when gem desktop 
appears for example.

Load the program at address $40000 for a quick test :

loadbin debug.prg $40000

set 2 breakpoints at $40022 and $40028 and set pc=$4001c :

a $40022
a $40028
r pc=$4001c

This is the code in RAM :

$0004001c : 7000                               moveq     #0,d0
$0004001e : 7200                               moveq     #0,d1
$00040020 : 7400                               moveq     #0,d2
$00040022 : 7201                               moveq     #1,d1
$00040024 : 7402                               moveq     #2,d2
$00040026 : 7603                               moveq     #3,d3
$00040028 : 4e71                               nop

Type 'r', you can see that d0/d1/d2/d3 have various non null values

Now type 'c', program will run from $4001e until breakpoint at $40022 -> 
-> d0/d1/d2 are correctly set to '0'

Skip instr at $40022 by changing PC
> r pc=$40024

type 's' to continue and execute only 1 instruction and type 'r' after.

> s

CPU=$40026, VBL=2862, FrameCycles=2480, HBL=4, LineCycles=432, DSP=N/A
$00040026 : 7603                               moveq     #3,d3
> r
  D0 00000000   D1 00000000   D2 00000002   D3 00000000

So, only D2 was changed (by instruction at PC=40024) and program goes 
back to debugger correctly with PC=$40026.
-> The 1st instruction at the new PC was correctly executed.

Can you try this ? I checked with 68000 cpu, do you use 68030 ?

This requires hatari 2.1, as 2.0 could have prefetch issue when changing PC.


Nicolas

Attachment: debug.prg
Description: Binary data

	moveq	#0,d0
	moveq	#0,d1
	moveq	#0,d2

	moveq	#1,d1
	moveq	#2,d2
	moveq	#3,d3

	nop