Re: [PATCH] ntdll: Initialize StatusWord and TagWord in i386 init_thread_context.

[Jefferson Carpenter]

This does not resolve the bug, but moves toward resolving it.

I have not been able to get a consistent read on what to initialize the 
remaining members to.

Thanks,
Jefferson

[PATCH] ntdll: Initialize StatusWord and TagWord in i386 init_thread_context.

[Jefferson Carpenter]

I know this adds yet another copy/paste of XMM_SAVE_AREA32.  I feel this 
patch is a separate concern from merging all of those into one though.

On 7/3/2020 6:56 AM, Jefferson Carpenter wrote:
> This does not resolve the bug, but moves toward resolving it.
>
> I have not been able to get a consistent read on what to initialize the 
> remaining members to.
>
> Thanks,
> Jefferson

[PATCH] ntdll: Initialize StatusWord and TagWord in i386 init_thread_context.

[Alexandre Julliard]

Jefferson Carpenter  writes:
> @@ -2270,7 +2270,11 @@ static void init_thread_context( CONTEXT *context, LPTHREAD_START_ROUTINE entry,
>      context->Esp    = (DWORD)NtCurrentTeb()->Tib.StackBase - 16;
>      context->Eip    = (DWORD)relay;
>      context->FloatSave.ControlWord = 0x27f;
> - context->FloatSave.StatusWord  = 0;
> - context->FloatSave.TagWord     = 0xffff;
> ((XMM_SAVE_AREA32 *)context->ExtendedRegisters)->ControlWord = 0x27f;
> - ((XMM_SAVE_AREA32 *)context->ExtendedRegisters)->StatusWord  = 0;
> - ((XMM_SAVE_AREA32 *)context->ExtendedRegisters)->TagWord     = 0;
> ((XMM_SAVE_AREA32 *)context->ExtendedRegisters)->MxCsr = 0x1f80;

The entire context is already initialized to 0, this shouldn't be
necessary.

[PATCH] ntdll: Initialize StatusWord and TagWord in i386 init_thread_context.

[Jefferson Carpenter]

I will look into this.  Zeroing the entire thing in this function clears 
up the valgrind warning (this could be a valgrind bug).  However at 
least setting TagWord is a correction that sets the FPU to the correct 
state (all floats empty).

On 7/3/2020 9:47 AM, Alexandre Julliard wrote:
> Jefferson Carpenter  writes:
> > @@ -2270,7 +2270,11 @@ static void init_thread_context( CONTEXT *context, LPTHREAD_START_ROUTINE entry,
> >       context->Esp    = (DWORD)NtCurrentTeb()->Tib.StackBase - 16;
> >       context->Eip    = (DWORD)relay;
> >       context->FloatSave.ControlWord = 0x27f;
> > - context->FloatSave.StatusWord  = 0;
> > - context->FloatSave.TagWord     = 0xffff;
> >  ((XMM_SAVE_AREA32 *)context->ExtendedRegisters)->ControlWord = 0x27f;
> > - ((XMM_SAVE_AREA32 *)context->ExtendedRegisters)->StatusWord  = 0;
> > - ((XMM_SAVE_AREA32 *)context->ExtendedRegisters)->TagWord     = 0;
> >  ((XMM_SAVE_AREA32 *)context->ExtendedRegisters)->MxCsr = 0x1f80;
>
> The entire context is already initialized to 0, this shouldn't be
> necessary.