add initial draft of Valid Usage and Undefined Behavior section (#1105)

api/opencl_architecture.asciidoc

@@ -2278,3 +2278,33 @@ include::{generated}/api/structs/cl_name_version.txt[]
     containing a null-terminated string, whose maximum length is therefore
     {CL_NAME_VERSION_MAX_NAME_SIZE} minus one.
 --
+
+[[valid-usage]]
+=== Valid Usage and Undefined Behavior
+
+The OpenCL specification describes valid usage and how to use the API correctly.
+For some conditions where an API is used incorrectly, behavior is well-defined,
+such as returning an error code.
+For other conditions, behavior is undefined, and may include program
+termination.
+However, OpenCL implementations must always ensure that incorrect usage by an
+application does not affect the integrity of the operating system, the OpenCL
+implementation, or other OpenCL client applications in the system.
+In particular, any guarantees made by an operating system about whether memory
+from one process can be visible to another process or not must not be violated
+by an OpenCL implementation for any memory allocation.
+OpenCL implementations are not required to make additional security or integrity
+guarantees beyond those provided by the operating system unless explicitly
+directed by the application’s use of a particular feature or extension.
+
+[NOTE]
+--
+For instance, if an operating system guarantees that data in all its memory
+allocations are set to zero when newly allocated, the OpenCL implementation must
+make the same guarantees for any allocations it controls.
+
+Similarly, if an operating system guarantees that use-after-free of host
+allocations will not result in values written by another process becoming
+visible, the same guarantees must be made by the OpenCL implementation for
+memory accessible to an OpenCL device.
+--