Hi all,

  Please let me explain what I am trying to do first. First, I compile
a 64 bit binary so that it'll be loaded above 4G virtual space, so the
virtual space below 4G is empty. I want to make a virtual address below
4G share the same phys page with another virtual address above 4G, so
that read/write vadd1 just like vaddr2. 


               PGD/PUD/PMD       Page Table
                                 ----------             Phys Page 2
                                |          |             --------
                                |----------|            |        |
                     vaddr2     |   pte 2  | ---------> |        |
                                |----------|            |        |
                                |          |             --------
                                |          |                ^
  4G above                      |          |                |
 ---------------------------------------------              |
                                |          |                |
                                |          |                |
                                |----------|                |
                     vaddr1     |   pte 1  | ---------------
                                |----------|            
                                |          |            
                                |__________|


Currently, I choose to manually create PUD/PMD/PT associated with vaddr1
, and set pte1 to point to phys page 2 (you can see the attach example
syscall, vadd1 is fixed to 0x10000000 for simplicity). However, the page
I create for PMD in the example will cause memory leak (see below). What
is the proper way to do so that kernel can free the page I allocated
automatically when the application calling the syscall is terminated?

    pmd = pmd_offset(pud, vaddr);
    if(pmd_none(*pmd)) {
        page = pte_alloc_one(current->mm, vaddr);
        pmd_n = mk_pmd(page, pgprot);
        set_pmd(pmd, pmd_n);
    }
 
  Thanks!

Regards,
chenwj

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj