linux page table entry struct

Page Table Entry

The access control information is held in the PTE and is CPU specific; figure bit fields have the following meanings:

V

Valid, if set this PTE is valid,       页表是否可用

FOE

``Fault on Execute'', Whenever an access of this type occurs, the CPU reports a page fault and passes control to the operating system,  执行错误

FOW

``Fault on Write'',    写错误

FOR

``Fault on Read'',   读错误

ASM

Address Space Match. This is used when the operating system wishes to clear only some of the entries from the Translation Buffer,  是否允许操作系统从页表绶存中清除

KRE

Code running in kernel mode can read this page,        内核模式可读

URE

Code running in user mode can read this page,         用户模式可读

GH

Granularity hint used when mapping an entire block with a single Translation Buffer entry rather than many,

KWE

Code running in kernel mode can write to this page,   内核模式可写

UWE

Code running in kernel mode can write this page,      用户模式可写

PFN

For PTEs with the V bit set, this field contains the physical Page Frame Number (PFN) for this PTE. For invalid PTEs, if this field is not zero, it contains information about where the page is in the swap file.    页帧号

The following two bits are defined and used by Linux:

__PAGE__DIRTY

if set, the page needs to be written out to the swap file,     如果被设备的话，可写到交换分区文件当中

__PAGE__ACCESSED

Used by Linux to mark a page as having been accessed.    标志是否之前被访问