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]

[e-mail] 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