Re: [ros-dev] [ros-diffs] [fireball] 48745: [NTOS] - Daniel Zimmermann: Fix POPF bugs in VDM mode, namely truncation of the stackpointer to 16 bit and setting proper flags in the trapframe eflags register. This fixes proble...

[Timo Kreuzer]

fireball(a)svn.reactos.org wrote:
>   Author: fireball
>  Date: Sat Sep 11 09:20:26 2010
>  New Revision: 48745
>     
...
>            /* Save EFlags */
>  +        Esp -= 4;
>  +        *(PULONG)(Esp - 2) = V86EFlags;
>     
This looks wrong to me. The (Esp - 2) I mean.


>   +    if (KiVdmGetPrefixFlags(Flags) &
> PFX_FLAG_OPER32)
>  +    {
>  +        /* Read EFlags */
>  +        EFlags = *(PULONG)Esp;
>  +        Esp += 4;
>  +    }
>  +    else
>  +    {
>  +        /* Read EFlags */
>  +        EFlags = *(PUSHORT)Esp;
>  +        Esp += 2;
>           /* Read correct flags and use correct stack address */
>  -        Esp -= 2;
>           EFlags &= 0xFFFF;
>     
Here the comment got broken a bit.

>        /* Set new ESP */
>  -    TrapFrame->HardwareEsp = Esp;
>  +    TrapFrame->HardwareEsp = (USHORT)Esp;
>     
This is not correct. We earlier calculated the flat Esp from Ss and Sp.
Example:
HardwareSegSs = 0x10, HardwareEsp = 0x10 -> flat Esp = 0x110, then you
substract 4, and get 0x10C. But this is not the value of the new
HardwareEsp. TrapFrame->HardwareEsp needs to be either modified in
parallel to the flat Esp or calculated like (USHORT)(Esp -
(TrapFrame->HardwareSegSs << 4)).

Regards,
Timo