Re: [Qemu-devel] ARM softmmu breakpoint misbehavior

[Sergey Fedorov <serge.fdrv@gmail.com>]

28.08.2015 22:21, Peter Maydell wrote:
> I think what we need to do is have the translate-a64.c
> code be smarter, and actually generate the real code
> if we're not going to really hit the bp. Except that we
> don't really have all the info in the flags to know for
> sure about that. So we probably need to do something like
> generating a call to a helper which checks whether this
> bp should hit and doesn't throw the exception unless it
> has to, with the actual code for the insn following.
> I need to think about how this ought to work...

I think we should only generate a CPU breakpoint TCG exception when it 
is really going to become a CPU exception (or a GDB exception). It could 
be done by moving the logic of check_breakpoints() to a helper called 
from TB.

> The watchpoint code has a chance of cpu_resume_from_signal
> doing the right thing, because we really did have the
> code to do the load/store. However I have a feeling this
> won't interact properly with the fact that ARM needs
> BP_STOP_BEFORE_ACCESS on its watchpoints (unlike x86, which
> is where I was looking at when I wrote the ARM wp handling
> code.) So we may well be broken there as well in the
> case where check_watchpoints() returns false.

As of watchpoints, I'm going to check that a bit later as well.