Re: [ros-dev] Kernel-mode stack layout (FPU save area, trap frames, etc.)

[Anich Gregor]

Hello!

I have tried to get some initial FPU save code working the last few days, but 
it always crashed on fsave or after frstor (math-fault)... I tried to reseve 
an FX_SAVE_AREA on top of the kernel stack by changing 
Ke386InitThreadWithContext to decrement the kernel stack pointer by sizeof 
(FX_SAVE_AREA) and changing the PsBeginThreadWithContext (in bthread.S) to 
not pop (frstor + decl esp) a FLOATING_AREA from the initial stack, so the 
FX_SAVE_AREA which is at the top of the stack should not be touched since the 
stack grows downwards, but it got either overwritten at some point or 
InitialThread in KTHREAD changes from time to time... Do you know if I should 
change the allocation size for the stack to MM_STACK_SIZE + sizeof 
(FX_SAVE_AREA) and use InitialThread instead of InitialThread - sizeof 
(FX_SAVE_AREA) for the FX_SAVE_AREA?

 - blight

On Friday 15 October 2004 19:02, Hartmut Birr wrote:
>   Hi,
>
>  I think we need two floating save areas, one for user mode and one for
>  kernel mode. The area for kernel mode is necessary because win32k and
>  freetype are using the fpu. The kernel mode area is not necessary if we
>  protect some function in win32k with
>  KeSaveFloatingPointState/KeRestoreFloatingPointState. The start of the
>  areas should be calculate as a offset from the top of the kernel stack and
>  not as offset from the user mode trap frame. The state of the fpu must be
>  saved on a thread switch and if the fpu was used. At this point the start
>  of the user mode trap frame is only known as an offset from the top of the
>  stack.
>
>  - Hartmut
>
> >   -----Original Message-----
> >  From: ros-dev-bounces(a)reactos.com
> >  [mailto:[e-mail]] On Behalf Of KJK::Hyperion
> >  Sent: Wednesday, October 13, 2004 8:13 AM
> >  To: ros-dev(a)reactos.com
> >  Subject: [ros-dev] Kernel-mode stack layout (FPU save area,
> >  trap frames,etc.)
> >
> >
> >  I've finally taken the time to write it all down:
> >
> >  <http://mok.lvcm.com/cgi-bin/reactos/roswiki?KernelModeStackLayout>
> >
> >  Let me know if you see any mistakes or omissions 
>