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+* Application name: Dynamic Callgraph
+* Contact: William Cohen, wochen@redhat.com
+
+* Motivation:
+
+Dynamic Callgraph would provide information to allow developers to see
+what other functions a function is calling. This could show that some
+unexpected functions are getting called. DTrace has a instrumentation
+provider that generates a trace of the functions called and returned.
+
+* Background:
+
+There have been times that people in Red Hat support have narrowed a
+problem to a specific function and the functions it calls.  Rather
+than instrumenting the function's children by hand, a tapset that
+provides a dynamic callgraph would allow quicker determination of the
+things called.  There are cases in the kernel code where determining
+the function being called cannot be determined statically,
+e.g. function to call is stored in a data structure.
+
+* Target software:
+
+Ideally both kernel and user space, but kernel space only would
+be sufficient for many cases.
+
+* Type of description:  tapset and scripting command
+  tapset to provide to support to capture call return information
+  scripting commands to turn on and off the capture
+
+* Interesting probe points:
+
+* Interesting values:
+
+* Dependencies:
+- P6/x86-64 processors have the debug hardware to trap control flow chgs.
+- Need to have the kernel maintain the debug hardware on a per process basis.
+       The DebugCtlMSR is not currently stored in the context
+	   (only debug registers 0, 1, 2, 3, 6, and 7 are virtualized)
+
+* Restrictions:
+  May be difficult to implement on ppc: returns may look like regular jumps
+      and trapping on all branches could cause problems with atomic operations
+  Won't work on pre p6 x86 processors
+  Won't provide data for inlined funcions
+
+* Data collection:
+  Track whether the instruction was a call or a return and the target address.
+
+* Data presentation:
+  -processing address in userspace to convert addresses into function names
+  -trace showing calls and returns
+  -maybe further post process to build dynamic callgraph
+	 determine that a function is being called way too often
+
+* Competition:
+  DTrace already implements tracing of function calls and returns.
+
+* Cross-references:
+
+* Associated files:
+
+  $dynamic_call_graph = 1; // turn on tracing of calls for thread
+  $dynamic_call_graph = 0; // turn off tracing of calls for thread
+