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|Home > Writing OS Awareness for DS-5 Debugger > Enabling the OS awareness|
The below implementation in provider.py, assumes
myos has a global variable called
tasks listing the OS tasks in an array and another global variable
scheduler_running indicating that the OS has started scheduling tasks.
# this script implements the Java interface IOSProvider from osapi import DebugSessionException def areOSSymbolsLoaded(debugger): return debugger.symbolExists("tasks") \ and debugger.symbolExists("scheduler_running") def isOSInitialised(debugger): try: result = debugger.evaluateExpression("scheduler_running") return result.readAsNumber() == 1 except DebugSessionException: return False def getOSContextProvider(): return None def getDataModel(): return None
osapi module in the import statement at the top of
provider.py is a collection of wrappers around Java objects
and utility functions. The file osapi.py itself can be found in
JAR file com.arm.debug.extension_<version>.jar.
Connecting to a running target and loading symbols manually for the OS shows both
At this point,
has been called and returned true, and the debugger is now waiting for the
target to stop to call
At this point,
isOSInitialised() has been called and returned
Active Threads and
Threads folders are always empty until you implement thread
Coresfolder by enabling the Always Show Cores option in the View Menu of the Debug Control view.
false. This can happen for instance when connecting to a stopped target, loading both the kernel image to the target and associated symbols in the debugger and starting debugging from a point in time earlier than the OS initialization, for example, debugging from the image entry point.
In this case, the Debug
Control view shows Waiting for
the OS to be initialised as
scheduler_running is not set to
1 yet, but symbols are loaded:
Without the call to
isOSInitialised() the debugger lets the awareness
implementation start reading potentially uninitialized memory, which is why
this callback exists. The debugger keeps calling back to
isOSInitialised() on subsequent stops until it
returns true, and the OS awareness can finally be enabled.