[GitHub] [incubator-nuttx] patacongo commented on issue #3168: Move internal globals to TLS to protect mutual access on FLAT mode

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patacongo commented on issue #3168:
URL: https://github.com/apache/incubator-nuttx/issues/3168#issuecomment-808191946


   I meant to copy this here yesterday but I accientally put this in PR #3182:
   
   > > From PR #3170
   > > I am beginning to think that the best way to implement per-process globals might be the same way that we already implement other per-process, application data like file descriptor, streams, etc. Allocate then with umm_malloc(), but retain them in the group structure with the system call to access them.
   > 
   > Yes, it's another approach, but why not move all pure userspace stuff to the main stack? So we don't have to put some special FILE function inside the kernel space.
   
   I don't know how to do that and moving ALL of the userspace stuff to the main stack is more than I can offer to do now.  There is no interface that will support a thread's access to data stored in the main thread's stack.  How would you do that?  A new non-standard OS interface?
   
   I think would need:
   
   - A correctly working getpid(), and
   - A new TLS interface that will get the TLS data from the main thread (or perhaps any thread given the pid?  No, that would be a security problem).
   
   So I think we are dead in the water for now:
   
   - getopt() needs process-specific data (It does not need TLS or a pthread data destructor).
   - We don't have agreement on how to do process-specific data
   
   I will do something else today.  This is not ready to implement.
   
   


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