access pointer and global variables

[Wenji Huang <wenji dot huang at oracle dot com>]

 Hi guru,

   I just began to know about the project and ran into some problems.

   a. dereference pointer
      probe kernel.function("schedule").return{
         $prev can be accessed, but just treated as long type
         $prev->pid can't be accessed
       }
  
   b. Global variable
       how to get the value of global variables, seems that only local 
variables are accessible in probe point.

   c. char *
       probe kernel.function("sys_open") {
          //parameter list in source:   const char __user *filename, 
int flags, int mode)  

          $filename can be accessed, but how to get the string of 
filename point ?
       }

Thanks in advance!
*
Wenji*