RB Tree parsing in crash utility

Requirement: see all the virual address allocated to a process.

This is just for the demo purpose of tree command. If you want to do this you can do using command
crash>vm -p

from the ps output,

we pick the process ".android.chrome" whose task_struct address is 0xe22f6200

crash> struct task_struct 0xe22f6200
----strip-------
 mm = 0xedab1500,
----strip-------

we got the value of mm.

 crash> struct mm_struct 0xe22f6200
 struct mm_struct {          
  mmap = 0x1,                
  mm_rb = {                  
    rb_node = 0xc2b00000    
  },                        
  mmap_cache = 0x2,          

Now to list all vm_area(vm_start and vm_end)
crash> tree -t rbtree -r mm_struct.mm_rb 0xedab1500 -o 16 -s vm_area_struct.vm_start,vm_end

the value passed to -o is calulate as follows,
 crash> struct vm_area_struct.vm_rb  
struct vm_area_struct {              
  [16] struct rb_node vm_rb;        
}