Re: [ros-dev] [ros-diffs] [aandrejevic] 65441: [FAST486] Attempt to write the value to the stack before subtracting from the actual ESP register in Fast486StackPush.

[Timo Kreuzer]

Are you sure this is the correct order of execution? The instruction is 
documented as first lowering the stack pointer, then writing to the new 
location.
If a stack exception occurs, you might have esp off by 4.

Am 21.11.2014 10:46, schrieb [e-mail]:
> Author: aandrejevic
> Date: Fri Nov 21 09:46:57 2014
> New Revision: 65441
>
> URL: http://svn.reactos.org/svn/reactos?rev=65441&view=rev
> Log:
> [FAST486]
> Attempt to write the value to the stack before subtracting from the actual ESP register
> in Fast486StackPush.
>
> Modified:
>      trunk/reactos/lib/fast486/common.inl
>
> Modified: trunk/reactos/lib/fast486/common.inl
> URL: http://svn.reactos.org/svn/reactos/trunk/reactos/lib/fast486/common.inl?rev=...
> ==============================================================================
> --- trunk/reactos/lib/fast486/common.inl	[iso-8859-1] (original)
> +++ trunk/reactos/lib/fast486/common.inl	[iso-8859-1] Fri Nov 21 09:46:57 2014
> @@ -317,15 +317,19 @@
>               return FALSE;
>           }
>    /* Store the value in SS:[ESP - 4] */
>    if (!Fast486WriteMemory(State,
>                            FAST486_REG_SS,
>                            State->GeneralRegs[FAST486_REG_ESP].Long - sizeof(ULONG),
>                            &Value,
>                            sizeof(ULONG)))
>    {
>        /* Exception occurred */
>        return FALSE;
>    }
>     /* Subtract ESP by 4 */
>     State->GeneralRegs[FAST486_REG_ESP].Long -= sizeof(ULONG);
>    /* Store the value in SS:ESP */
>    return Fast486WriteMemory(State,
>                              FAST486_REG_SS,
>                              State->GeneralRegs[FAST486_REG_ESP].Long,
>                              &Value,
>                              sizeof(ULONG));
> }
> else
> {
>
> @@ -339,16 +343,22 @@
>               return FALSE;
>           }
>    /* Store the value in SS:[SP - 2] */
>    if (!Fast486WriteMemory(State,
>                            FAST486_REG_SS,
>                            LOWORD(State->GeneralRegs[FAST486_REG_ESP].LowWord - sizeof(USHORT)),
>                            &ShortValue,
>                            sizeof(USHORT)))
>    {
>        /* Exception occurred */
>        return FALSE;
>    }
>     /* Subtract SP by 2 */
>     State->GeneralRegs[FAST486_REG_ESP].LowWord -= sizeof(USHORT);
>    /* Store the value in SS:SP */
>    return Fast486WriteMemory(State,
>                              FAST486_REG_SS,
>                              State->GeneralRegs[FAST486_REG_ESP].LowWord,
>                              &ShortValue,
>                              sizeof(USHORT));
> }
>
> }
>
> return TRUE;
> }
>
> FORCEINLINE