OpenEuphoria

Re: WinXP SP2 and inline machine code calling

• Posted by Tommy Carlier <tommy.carlier at telenet.be> Sep 15, 2004
• 450 views

unknown wrote:
> I  haven't  tried  SP2, and possibly never, but SP2 has Data Execution
> Prevention <a href="http://fype.com/sp2dep">http://fype.com/sp2dep</a>
> 
> Will it be preventing this kind of code execution?
> (because the code will be executed from data area, CMIIW)
> 
> 
> (taken from bit.e)
> poke(SHL_SPACE, {
>      -- first int argument is at stack offset +4, 2nd int is at +8
>      -- returns a *signed* 32-bit number
>      #8B, #44, #24, #04,      -- mov  eax, [esp+4]
>      #8A, #4C, #24, #08,      -- mov  cl,  [esp+8]
>      #D3, #E0,                -- shl  eax, cl
>      #C2, #08, #00            -- ret  8  -- pop 8 bytes off the stack
>     })
> 
> SHIFT_LEFT = define_c_func("", SHL_SPACE, {C_INT, C_INT}, C_INT)

Only if your CPU has a mechanism to block execution from a data area. And only
the very recent CPUs have such a mechanism. But that's an interesting and perhaps
disturbing thought, given your example.

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