SharedUnixLibrary and the System Heap

Alex Waugh alex at
Tue Mar 28 14:36:38 PST 2006

Matt Edgar <matt at> wrote:

> Alex Waugh wrote:
> > I'm glad to see such improvements are being considered.
> >
> >>Unfortunately SUL does this, so protecting the heap would break a lot of 
> >>things.
> > 
> > 
> > Do you mean memory allocated by OS_Module 6, executing module code
> > from user mode, the module private word, or something else? Those are
> > the only things I can think of that may be accessed from user mode in
> > the SUL.
> I have not spent much time tracking this down, but probably all of the 
> above are issues.

Accessing the private word could probably be sorted out fairly easily.
OS_Module allocated memory could be worked around in a backwards
compatible manner e.g. by SUL maintaining a heap in a DA to allocate
from. Executing module code from user mode could not not be prevented
without breaking backwards compatibility, and may well have large
issues even if you didn't care about backwards compatibility.


Alex Waugh                                           alex at

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