MIT6.s081 lab3记录：页表

Print a page table

page table 0x0000000087f6e000
 ..0: pte 0x0000000021fda801 pa 0x0000000087f6a000
 .. ..0: pte 0x0000000021fda401 pa 0x0000000087f69000
 .. .. ..0: pte 0x0000000021fdac1f pa 0x0000000087f6b000
 .. .. ..1: pte 0x0000000021fda00f pa 0x0000000087f68000
 .. .. ..2: pte 0x0000000021fd9c1f pa 0x0000000087f67000
 ..255: pte 0x0000000021fdb401 pa 0x0000000087f6d000
 .. ..511: pte 0x0000000021fdb001 pa 0x0000000087f6c000
 .. .. ..509: pte 0x0000000021fdd813 pa 0x0000000087f76000
 .. .. ..510: pte 0x0000000021fddc07 pa 0x0000000087f77000
 .. .. ..511: pte 0x0000000020001c0b pa 0x0000000080007000

• What does page 0 contain?

  code and data

  

• What is in page 2?

user stack

• When running in user mode, could the process read/write the memory mapped by page 1?

  pte: 0x0000000021fda00f

  

  can’t read , write, and execute in user mode, this could be the guard page

• What does the third to last page contain?

  the last page is the trapoline page, but the last two i am not sure, may be the heap and trapframe

Detecting which pages have been accessed (hard)

Task

• implement pgaccess()：报告哪些页被访问了
• 参数：
  • 第一个用户页的起始虚拟地址
  • 需要检查的页的数量
  • 用来存结果的用户缓存地址