Re: [Valgrind-developers] debugging valgrind

[Sebastian B. <sb...@bi...>]

Nicholas Nethercote wrote:
> On Mon, 30 Aug 2004, Sebastian Biallas wrote:
> 
>>> That would catch some of them.  But the problem, AFAICT, with all 
>>> self-modifying code detection schemes is how to handle code on the 
>>> stack. For example, GCC generates snippets of code on the stack when 
>>> using nested functions.
>>
>> What? I thought this is highly undefined or at least deprecated,
> 
> Seemingly not, see http://bugs.kde.org/show_bug.cgi?id=69511.

Indeed, gcc emits "call %esp".

> 
>> and with NX-aware processores and kernels it will no longer work.
> 
> I'm no expert on that stuff, but I believe that GCC just turns off the 
> no-exec functionality in such systems in these cases.  Nasty, huh?

Very nasty:
http://www.ussg.iu.edu/hypermail/linux/kernel/0406.0/1056.html

Yesterdays technology tomorrow.

> 
> N
> 

Sebastian