acess permission in vm_area_struct

["Manoj Awasthi" <lkml.manoj@xxxxxxxxx>]

Hi,

 

I was going through vm_area_struct definition, a part of which is as shown below:

 

struct vm_area_struct {
62         struct mm_struct * vm_mm;       /* The address space we belong to. */
63         unsigned long vm_start;         /* Our start address within vm_mm. */
64         unsigned long vm_end;           /* The first byte after our end address
65                                            within vm_mm. */
66
67         /* linked list of VM areas per task, sorted by address */
68         struct vm_area_struct *vm_next;
69
70         pgprot_t vm_page_prot;          /* Access permissions of this VMA. */
71         unsigned long vm_flags;         /* Flags, listed below. */
72

 

I am confused about the fields vm_page_prot and vm_flags. confusion arose because vm_flags can be following too - 

 /*
136 * vm_flags..
137 */
138 #define VM_READ         0x00000001      /* currently active flags */
139 #define VM_WRITE        0x00000002
140 #define VM_EXEC         0x00000004
141 #define VM_SHARED       0x00000008
142
 

so what other access permissions are defined by vm_page_prot  and what is the stand in case of a conflict of permissions ?

 

can someone clear my doubt ?

 

thanks,

-Manoj