Sharing a normal memory mapping is not necessarily what is required here though. What you want is to share the same GPU-side memory buffer between two processes. It may not even be mappable to cpu side memory.
If it's mapped into the CPU address space, then it can be shared. If not, then there is a copy going on and you may as well just do it in the non-sandboxed process, no?
There is no copy. You have a reference to a GPU side buffer, and you want to pass a reference to that buffer to another process, where it will continue to use the GPU to access it.
