sdt Probe Arguments

The arguments for each sdt probe are the arguments that are specified in the kernel source code in the corresponding DTRACE_PROBE macro reference. When declaring your sdt probes, you can minimize their disabled probe effect by not dereferencing pointers and by not loading from global variables in the probe arguments. Both pointer dereferencing and global variable loading may be done safely in D actions that enable probes, so DTrace users can request these actions only when they are needed.