question: @ Uninterruptible public static Address unwindNativeStackFrame ( Address currfp ) { if ( VM . BuildForIA32 ) { return currfp ; } Address callee_fp ; Address fp = Magic . getCallerFramePointer ( currfp ) ; Address ip ; do { callee_fp = fp ; ip = Magic . getReturnAddressUnchecked ( fp ) ; fp = Magic . getCallerFramePointer ( fp ) ; } while ( ! MemoryManager . addressInVM ( ip ) && fp . NE ( StackFrameLayout . getStackFrameSentinelFP ( ) ) ) ; if ( VM . BuildForPowerPC ) { return fp ; } else { return callee_fp ; } }
target:  Skip over all frames below currfp with saved code pointers outside of heap (C frames), stopping at the native frame immediately preceding the glue frame which contains the method ID of the native method (this is necessary to allow retrieving the return address of the glue frame).