[LLVMdev] Stack smashing

[Bill Wendling]

On Tue, Mar 10, 2009 at 2:12 PM, Eric Christopher <echristo at apple.com> wrote:
>
> On Mar 10, 2009, at 3:07 PM, Jon Harrop wrote:
>
>> On Tuesday 10 March 2009 21:47:59 someguy wrote:
>>> From a cursory glance, it looks like something is messing with the
>>> stack canarys. Probably a stack buffer overflow.
>>
>> In case it is relevant, HLVM uses libsigsegv to detect stack
>> overflows and
>> that stack handler is initialized in my JITted code which LLVM's
>> runFunction
>> should be calling.
>>
>> Could libsigsegv be conflicing with the stack smashing code?
>
> If it changes known values on the stack - yes.
>
> Basically it all works by placing a sentinel value on the stack
> initialized with a
> random number that's then checked at the end of the function. If that
> has been
> changed it calls abort().  IIRC the feature is turned on by default on
> modern
> versions of linux. I do not believe it is yet turned on by default for
> darwin.
>
It's not turned on by default for Leopard. If you don't want these
stack protectors (which is sounds like in this case), just use
-fno-stack-protector. At least on the particular files you know that
libsigsegv is messing with...

-bw