Re: [Gnustep-cvs] r26723 - in /libs/base/trunk: ChangeLog Headers/Additions/GNUstepBase/config.h.in Source/GSFFIInvocation.m configure configure.ac

[Richard Frith-Macdonald]

On 29 Jun 2008, at 08:54, David Ayers wrote:

> Hello David
>
> David Chisnall schrieb:
> > I think calling mmap directly is the wrong solution here.  You  
> > should be
> > using valloc() with the requested size rounded up to the nearest page

I'm not sure what advantage valloc() has over mmap() ... all the  
examples/recommendations I found on the web were for mmap().

> > size, and then use mprotect to set it as executable.  Note that most
> > sane operating systems (and Vista) are moving to W^X, so you need  
> > to set
> > it as writeable while creating it, then executable while using it  
> > (i.e.
> > call mprotect immediately before the return).

Good, point ... the code already uses mprotect if available, but I  
also changed it to refrain from trying to map the memory as executable  
in the case where we can later use mprotect.  This should avoid  
problems on systems (I don't have one to test on) where an attempt to  
map memory which is both writable and executable would fail.

> My man page for vmalloc states:
>       The  obsolete  function  valloc()  allocates  size bytes and
> returns a pointer to the allocated memory.  The memory address will  
> be a
> multiple of the page
>       size.  It is equivalent to memalign(sysconf(_SC_PAGESIZE),size).
>
> I'm not sure whether you are aware of the fact that this function is
> considered obsolete.
>
> Hi Richard,
>
> My man page for mmap states:
>       MAP_ANON
>              Synonym for MAP_ANONYMOUS.  Deprecated.
>
> So to me it seems the new #ifndef logic is inverted.

Thanks ... I changed that round to use MAP_ANONYMOUS preferentially.