Re: ntdll:exception crashes some Windows 10

[Paul Gofman]

On 12/8/20 17:39, Francois Gouget wrote:
> On Mon, 7 Dec 2020, Paul Gofman wrote:
> > On 12/7/20 17:07, Francois Gouget wrote:
>
> [...]
> > > dreg_test.dr0 = 0x42424240;
> > > dreg_test.dr2 = 0x126bb070;
> > > dreg_test.dr3 = 0x0badbad0;
> > > dreg_test.dr7 = 0xffff0115;
> > > run_exception_test(dreg_handler, &dreg_test, &segfault_code, sizeof(segfault_code), 0);
>
> [...]
> > While it looks like a definite VM bug, it is maybe interesting to know
> > for a start what exactly triggers the error. Is it possible to see if
> > disabling the setting of the debug registers in dreg_handler() above
> > (lines context->Dr<n> = test->dr<n>;) avoids the crash, and if yes,
> > which exactly register(s) setting trigger that.
>
> It does not matter which register is set (dr0, dr2, dr3 or dr7), Windows 
> crashes with any of them. It's only if I comment all of them out that it 
> does not crash :-(

Are you commenting out here in the cited code or (better) in dreg_handler?