[fpc-pascal] assign code to a method

[Sven Barth]

Am 18.02.2011 13:46, schrieb Sven Barth:
> Am 18.02.2011 12:16, schrieb Marco van de Voort:
>> In our previous episode, Jonas Maebe said:
>>>> because this is not a problem in Delphi nor it was in an old version
>>>> of fpc-Lazarus 32 bits. Please give me a tip.
>>>> Many thanks in advance.
>>>
>>> You probably have to mark the memory in which you write the code as
>>> "executable" first (this has to be done using an OS-specific function;
>>> I know next to nothing about Windows programming, but you should be
>>> able to find the necessary information in MSDN).
>>>
>>> In fact, you should also do this on 32 bit platforms, since more and
>>> more systems mark memory by default as not executable for security
>>> purposes.
>>
>> This is called DEP (Data Execution Protection, which is an amalgam of
>> resp
>> AMD and Intel hardware protection and some software forms). IIRC it is
>> always on for 64-bit, and for 32-bit server versions that use a PAE
>> kernel.
>> (client OSes don't have PAE version on windows afaik)
>>
>
> This is not entirely correct. Quote from Wikipedia regarding PAE:
> ===quote begin===
> Windows XP SP2 and later, by default, on processors with the no-execute
> (NX) or execute-disable (XD) feature, runs in PAE mode in order to allow
> NX.
> ===quote end===
>
>> Afaik it can only be turned on before starting a binary. An executable
>> can't
>> disable it while running (since then it would be useless, as a virus
>> could
>> simply disable it)
>>
>> See e.g.
>> http://techblissonline.com/enable-disable-dep-in-windows-xp-vista/
>>
>> Searching for "disable dep" or so will probably yield more results.
>>
>> Of course, this is not healthy and supportable application behaviour,
>> but I
>> assume this is already known.
>
> I personally would say that mapping a page with the Execute flag set and
> storing the to-be-executed content there should be enough. After all JIT
> compilers must do that as well. ;)

Also according to here: 
http://en.wikipedia.org/wiki/Data_Execution_Prevention#Configuration DEP 
is not enabled by default for all applications.

Regards,
Sven