[Qemu-devel] Re: [PATCH 0/5] Debugger enhancements

[Jan Kiszka <jan.kiszka@web.de>]

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Fabrice Bellard wrote:
> Paul Brook wrote:
>>> 2) The current watchpoint code is not implemented correctly so it is not
>>> safe to improve it using the same system (IMHO it should not have been
>>> commited in its current state). A correct implementation should not
>>> delay the DEBUG exception. It should be implemented like the "normal"
>>> MMU exceptions.
>> On most targets watchpoint traps occur after the instruction completes, so you 
>> have to defer the DEBUG exception.
>> Normal MMU faults occur before the instruction completes.
> 
> If this is the wanted behavior then the same system as the Self
> Modifying Code on x86 should be used. Basically it consists in doing as
> a MMU fault and single stepping one instruction after. Unfortunately I
> fear the implementation will be complicated.

It isn't, in fact, and it allows for a few nice cleanups. I've a working
version here now, based on a new singlestep_enable flag. Will re-post my
whole series once I've integrated your other remarks.

Jan


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