On 2012年07月31日 17:20, Dhyan wrote: > Thank You Bill !!! > > I dont know my approach is correct or not,But the actual purpose was to > dump only written pages of a user process using a kernel module.I have > a kernel thread which will dump user process memory in specific > interval.So i thought of updating this flag (L_PTE_DEBUG) from > handle_pte_fault and clear from my clear thread so that i can dump only > the written pages after my last dump. Yes, you can do that, only if your accounting memory doesn't get swapped out. If I understand correctly, when writing a page, you mark corresponding linux pte entry with L_PTE_DEBUG. Then your kernel module periodically loops all linux pte table, find pte entry marked with L_PTE_DEBUG..... I don't think it's wise to do so, you have 768 1st level pgd entries for user space, followed by 256 pte entries with each pgd entry. it's much slower to find out the right one. moreover, you probably need to remap those L_PTE_DEBUG physical pages into your own current process address space. IMHO, I don't follow such idea could be feasible. > > if you have some suggestions could you please share wth me? I understand how you plan to do this, could I ask why you need to dump the written pages? > > -- > Thanks > Dhyan > > On Tue, Jul 31, 2012 at 12:43 PM, bill4carson <bill4carson@xxxxxxxxx > <mailto:bill4carson@xxxxxxxxx>> wrote: > > > > On 2012年07月30日 17:39, Dhyan wrote: > > Dear All, > > From linux(2.6.35) arm page table architecture i can see we > have one > hardware page table and there is corresponding Linux page table > Entry > (L_PTE_*).The "Linux" PTE definitions are as like below from > arch/arm/include/asm/pgtable.__h. > > |#define L_PTE_PRESENT (1<< 0) > #define L_PTE_FILE (1<< 1) > #define L_PTE_YOUNG (1<< 1) > #define L_PTE_BUFFERABLE(1<< 2) > #define L_PTE_CACHEABLE (1<< 3) > #define L_PTE_USER (1<< 4) > #define L_PTE_WRITE (1<< 5) > #define L_PTE_EXEC (1<< 6) > #define L_PTE_DIRTY (1<< 7) > #define L_PTE_COHERENT (1<< 9) > #define L_PTE_SHARED (1<< 10) > | > > So is it possible to add one more #|define L_PTE_DEBUG (1 << > 11)| for my > > debugging purpose (basically to trap all the write to that page > and set > this bit when write happens and clear it off in another thread > )? Or > is there any limitation like we can use only L_PTE till 10th bit ? > > > No such limitation on bit 11, so you can use define L_PTE_DEBUG (1 > << 11) > However I don't follow why you want to do so? > > > So could you please help > > -- > > Thanks & Regards > > Dhayn > > > > _________________________________________________ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.__org > <mailto:Kernelnewbies@xxxxxxxxxxxxxxxxx> > http://lists.kernelnewbies.__org/mailman/listinfo/__kernelnewbies <http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies> > > > -- > Love each day! > > --bill > > -- Love each day! --bill _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
