static int __do_vmalloc_fault(unsigned long addr, struct mm_struct *mm)
{
	/* Synchronise this task's top level page-table
	 * with the 'reference' page table.
	 */
	int offset = __pgd_offset(addr);
	pgd_t *pgd, *pgd_k;
	pmd_t *pmd, *pmd_k;

	pgd_k = init_mm.pgd + offset;
	if (!pgd_present(*pgd_k))
		goto bad_area;

	pgd = mm->pgd + offset;
#if 0	/* note that we are two-level */
	if (!pgd_present(*pgd))
		set_pgd(pgd, *pgd_k);
#endif

	pmd_k = pmd_offset(pgd_k, addr);
	if (pmd_none(*pmd_k))
		goto bad_area;

	pmd = pmd_offset(pgd, addr);
	if (!pmd_none(*pmd))
		goto bad_area;
	set_pmd(pmd, *pmd_k);
	return 1;

bad_area:
	return -2;
}

static int find_num_contig(struct mm_struct *mm, unsigned long addr,
			   pte_t *ptep, pte_t pte, size_t *pgsize)
{
	pgd_t *pgd = pgd_offset(mm, addr);
	pud_t *pud;
	pmd_t *pmd;

	*pgsize = PAGE_SIZE;
	if (!pte_cont(pte))
		return 1;
	if (!pgd_present(*pgd)) {
		VM_BUG_ON(!pgd_present(*pgd));
		return 1;
	}
	pud = pud_offset(pgd, addr);
	if (!pud_present(*pud)) {
		VM_BUG_ON(!pud_present(*pud));
		return 1;
	}
	pmd = pmd_offset(pud, addr);
	if (!pmd_present(*pmd)) {
		VM_BUG_ON(!pmd_present(*pmd));
		return 1;
	}
	if ((pte_t *)pmd == ptep) {
		*pgsize = PMD_SIZE;
		return CONT_PMDS;
	}
	return CONT_PTES;
}

static int handle_tlbmiss(struct mm_struct *mm,
              unsigned long long protection_flags,
              unsigned long long textaccess,
              unsigned long address)
{
    pgd_t *dir;
    pud_t *pud;
    pmd_t *pmd;
    pte_t *pte;
    pte_t entry;

    /* NB. The PGD currently only contains a single entry - there is no
       page table tree stored for the top half of the address space since
       virtual pages in that region should never be mapped in user mode.
       (In kernel mode, the only things in that region are the 512Mb super
       page (locked in), and vmalloc (modules) +  I/O device pages (handled
       by handle_vmalloc_fault), so no PGD for the upper half is required
       by kernel mode either).

       See how mm->pgd is allocated and initialised in pgd_alloc to see why
       the next test is necessary.  - RPC */
    if (address >= (unsigned long) TASK_SIZE)
        /* upper half - never has page table entries. */
        return 0;

    dir = pgd_offset(mm, address);
    if (pgd_none(*dir) || !pgd_present(*dir))
        return 0;
    if (!pgd_present(*dir))
        return 0;

    pud = pud_offset(dir, address);
    if (pud_none(*pud) || !pud_present(*pud))
        return 0;

    pmd = pmd_offset(pud, address);
    if (pmd_none(*pmd) || !pmd_present(*pmd))
        return 0;

    pte = pte_offset_kernel(pmd, address);
    entry = *pte;

    if (pte_none(entry) || !pte_present(entry))
        return 0;

    /*
     * If the page doesn't have sufficient protection bits set to
     * service the kind of fault being handled, there's not much
     * point doing the TLB refill.  Punt the fault to the general
     * handler.
     */
    if ((pte_val(entry) & protection_flags) != protection_flags)
        return 0;

        __do_tlb_refill(address, textaccess, pte);

    return 1;
}

asmlinkage long sys_my_syscall( int pid, unsigned long address)
{
   
   struct task_struct* task;
   struct mm_struct* mm;
   pgd_t* pgd;
   pud_t* pud;
   pmd_t* pmd;
   pte_t* pte;
   unsigned long pte_val ;
   printk(KERN_INFO "PID: %d, VIRTUAL_ADDR: 0x%lx\n", pid, address);
   for_each_process(task)
   {
     if(task->pid == pid)
     {           
      printk(KERN_INFO "Task %d found\n", task->pid);
      mm = task->mm;
      
      pgd = pgd_offset(mm, address);
      printk(KERN_INFO "PGD INFO: PRESENT: %d, BAD: %d, NONE: %d\n", pgd_present(*pgd), pgd_bad(*pgd), pgd_none(*pgd));
      if(!(pgd_none(*pgd) || pgd_bad(*pgd)) && pgd_present(*pgd))
      {
        printk(KERN_INFO "PGD INFO: PRESENT: %d, BAD: %d, NONE: %d\n", pgd_present(*pgd), pgd_bad(*pgd), pgd_none(*pgd));
        pud = pud_offset(pgd, address);
        printk(KERN_INFO "PUD INFO: PRESENT: %d, BAD: %d, NONE: %d\n", pud_present(*pud), pud_bad(*pud), pud_none(*pud));
           
        if(!(pud_none(*pud) || pud_bad(*pud)) && pud_present(*pud))
        {
          printk(KERN_INFO "PUD INFO: PRESENT: %d, BAD: %d, NONE: %d\n", pud_present(*pud), pud_bad(*pud), pud_none(*pud));
          pmd = pmd_offset(pud, address);
          printk(KERN_INFO "PMD INFO: PRESENT: %d, BAD: %d, NONE: %d\n", pmd_present(*pmd), pmd_bad(*pmd), pmd_none(*pmd));
           
          if(!(pmd_none(*pmd) || pmd_bad(*pmd)) && pmd_present(*pmd))
          {
            printk(KERN_INFO "PMD INFO: PRESENT: %d, BAD: %d, NONE: %d\n", pmd_present(*pmd), pmd_bad(*pmd), pmd_none(*pmd));
            pte = pte_offset_map(pmd, address);
            printk(KERN_INFO "PTE INFO: PRESENT: %d PTE: 0x%lx \n ", pte_present(*pte), pte->pte);


            pte_val = pte->pte;
            
            if(pte_val == 0)
                pte_val = __pte_to_swp_entry(*pte).val;
            
            pte_unmap(pte);
            printk(KERN_INFO "pte_val: %lx\n" , pte_val);
            return pte_val;
            
            }
        }
      }
    }
  }
  printk(KERN_INFO "Data not found!\n");
  return 0;
}

static void walk_pgd_level(struct seq_file *m)
{
#ifdef CONFIG_X86_64
	pgd_t *start = (pgd_t *) &init_level4_pgt;
#else
	pgd_t *start = swapper_pg_dir;
#endif
	int i;
	struct pg_state st;

	memset(&st, 0, sizeof(st));

	for (i = 0; i < PTRS_PER_PGD; i++) {
		st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
		if (!pgd_none(*start)) {
			pgprotval_t prot = pgd_val(*start) & PTE_FLAGS_MASK;

			if (pgd_large(*start) || !pgd_present(*start))
				note_page(m, &st, __pgprot(prot), 1);
			else
				walk_pud_level(m, &st, *start,
					       i * PGD_LEVEL_MULT);
		} else
			note_page(m, &st, __pgprot(0), 1);

		start++;
	}

	/* Flush out the last page */
	st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
	note_page(m, &st, __pgprot(0), 0);
}

static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
{
	unsigned index = pgd_index(address);
	pgd_t *pgd_k;
	pud_t *pud, *pud_k;
	pmd_t *pmd, *pmd_k;

	pgd += index;
	pgd_k = init_mm.pgd + index;

	if (!pgd_present(*pgd_k))
		return NULL;

	pud = pud_offset(pgd, address);
	pud_k = pud_offset(pgd_k, address);
	if (!pud_present(*pud_k))
		return NULL;

	pmd = pmd_offset(pud, address);
	pmd_k = pmd_offset(pud_k, address);
	if (!pmd_present(*pmd_k))
		return NULL;
	if (!pmd_present(*pmd)) {
		set_pmd(pmd, *pmd_k);
		arch_flush_lazy_mmu_mode();
	} else
		BUG_ON(pmd_ptfn(*pmd) != pmd_ptfn(*pmd_k));
	return pmd_k;
}

pte_t *
lookup_pte(pgd_t *page_dir, unsigned long pf_address)
{
	/*
	 * find the page table entry within the page table hierarchy
	 */
	pte_t *pte = NULL;
	pgd_t *pgd = page_dir + pgd_index(pf_address);

#ifdef DEBUG_LOOKUP_PTABS
	if ((int)page_dir < 0x1000) {
		printk("%s: page_dir=%x\n", __func__, (int)page_dir);
		enter_kdebug("page_dir<4096");
	}
	printk("%s: %lx pdir = %p\n", __func__, pf_address, pgd);
#endif
	if (pgd_present(*pgd)) {
		pmd_t *pmd = pmd_offset(pgd, pf_address);
#ifdef DEBUG_LOOKUP_PTABS
		printk("pgd_present(*%x) is true\n", pgd);
		printk(" pmd = %p\n", pmd);
#endif
		if (pmd_present(*pmd)) {
#ifdef DEBUG_LOOKUP_PTABS
			printk("pmd_present(*%x) is true\n", pmd);
#endif
			pte = pte_offset_map(pmd, pf_address);
		}
	}
#ifdef DEBUG_LOOKUP_PTABS
	printk("returning:  pte = %p\n", pte);
#endif
	return pte;
}

static bool kvm_mips_flush_gpa_pgd(pgd_t *pgd, unsigned long start_gpa,
				   unsigned long end_gpa)
{
	pud_t *pud;
	unsigned long end = ~0ul;
	int i_min = pgd_index(start_gpa);
	int i_max = pgd_index(end_gpa);
	bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PGD - 1);
	int i;

	for (i = i_min; i <= i_max; ++i, start_gpa = 0) {
		if (!pgd_present(pgd[i]))
			continue;

		pud = pud_offset(pgd + i, 0);
		if (i == i_max)
			end = end_gpa;

		if (kvm_mips_flush_gpa_pud(pud, start_gpa, end)) {
			pgd_clear(pgd + i);
			pud_free(NULL, pud);
		} else {
			safe_to_remove = false;
		}
	}
	return safe_to_remove;
}

static int handle_vmalloc_fault(unsigned long address)
{
	/*
	 * Synchronize this task's top level page-table
	 * with the 'reference' page table.
	 */
	pgd_t *pgd, *pgd_k;
	pud_t *pud, *pud_k;
	pmd_t *pmd, *pmd_k;

	pgd = pgd_offset_fast(current->active_mm, address);
	pgd_k = pgd_offset_k(address);

	if (!pgd_present(*pgd_k))
		goto bad_area;

	pud = pud_offset(pgd, address);
	pud_k = pud_offset(pgd_k, address);
	if (!pud_present(*pud_k))
		goto bad_area;

	pmd = pmd_offset(pud, address);
	pmd_k = pmd_offset(pud_k, address);
	if (!pmd_present(*pmd_k))
		goto bad_area;

	set_pmd(pmd, *pmd_k);

	/* XXX: create the TLB entry here */
	return 0;

bad_area:
	return 1;
}

int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
			      unsigned long pstart, unsigned long pend)
{
	unsigned long addr = pstart + info->offset;
	unsigned long end = pend + info->offset;
	unsigned long next;
	int result;

	for (; addr < end; addr = next) {
		pgd_t *pgd = pgd_page + pgd_index(addr);
		pud_t *pud;

		next = (addr & PGDIR_MASK) + PGDIR_SIZE;
		if (next > end)
			next = end;

		if (pgd_present(*pgd)) {
			pud = pud_offset(pgd, 0);
			result = ident_pud_init(info, pud, addr, next);
			if (result)
				return result;
			continue;
		}

		pud = (pud_t *)info->alloc_pgt_page(info->context);
		if (!pud)
			return -ENOMEM;
		result = ident_pud_init(info, pud, addr, next);
		if (result)
			return result;
		set_pgd(pgd, __pgd(__pa(pud) | _KERNPG_TABLE));
	}

	return 0;
}

int oleole_flush_guest_virt_memory(oleole_guest_system_t *gsys)
{
	unsigned long flags;
	unsigned long start, end;
	struct vm_area_struct	*vma;
	struct mm_struct *mm;
	pgd_t *pgd;

	spin_lock_irqsave(&gsys->lock, flags);
	vma = gsys->vma;
	spin_unlock_irqrestore(&gsys->lock, flags);

	if (!vma)
		return -1;

	mm = vma->vm_mm;

	if (!mm)
		return -1;

	start = vma->vm_start + OLEOLE_GUSET_VIRT_SPACE_OFFSET;
	end   = start         + 0x100000000UL;

	down_write(&mm->mmap_sem);

	pgd = pgd_offset(mm, start);
	if (!pgd_present(*pgd))
		goto miss;

	for (; start < end ; start += PUD_SIZE) {
		pud_t *pud;
		pmd_t *pmd;
		struct page *page;

		pud = pud_offset(pgd, start);
		if (!pud_present(*pud))
			goto miss;

		free_pmd_range(pud);

		pmd = pmd_offset(pud, 0);
		page = virt_to_page(pmd);
		__free_page(page);
		pud_clear(pud);
	}
miss:

	up_write(&mm->mmap_sem);

	__flush_tlb();

	return 0;
}

static int page_present(struct mm_struct *mm, void __user *uptr, int wr)
{
	unsigned long addr = (unsigned long)uptr;
	pgd_t *pgd = pgd_offset(mm, addr);
	if (pgd_present(*pgd)) {
		pmd_t *pmd = pmd_offset(pgd, addr);
		if (pmd_present(*pmd)) {
			pte_t *pte = pte_offset_map(pmd, addr);
			return (pte_present(*pte) && (!wr || pte_write(*pte)));
		}
	}
	return 0;
}

pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
{
	pgd_t *pgdp;
	pud_t *pudp;
	pmd_t *pmdp = NULL;

	pgdp = pgd_offset(mm, addr);
	if (pgd_present(*pgdp)) {
		pudp = pud_offset(pgdp, addr);
		if (pud_present(*pudp))
			pmdp = pmd_offset(pudp, addr);
	}
	return (pte_t *) pmdp;
}

/*
 * This routine puts a long into any process space by following the page
 * tables. NOTE! You should check that the long isn't on a page boundary,
 * and that it is in the task area before calling this: this routine does
 * no checking.
 *
 * Now keeps R/W state of page so that a text page stays readonly
 * even if a debugger scribbles breakpoints into it.  -M.U-
 */
static void put_long(struct task_struct * tsk, struct vm_area_struct * vma, unsigned long addr,
	unsigned long data)
{
	pgd_t *pgdir;
	pmd_t *pgmiddle;
	pte_t *pgtable;
	unsigned long page;
		
repeat:
	pgdir = pgd_offset(vma->vm_mm, addr);
	if (!pgd_present(*pgdir)) {
		do_no_page(tsk, vma, addr, 1);
		goto repeat;
	}
	if (pgd_bad(*pgdir)) {
		printk("ptrace: bad page directory %08lx\n", pgd_val(*pgdir));
		pgd_clear(pgdir);
		return;
	}
	pgmiddle = pmd_offset(pgdir,addr);
	if (pmd_none(*pgmiddle)) {
		do_no_page(tsk, vma, addr, 1);
		goto repeat;
	}
	if (pmd_bad(*pgmiddle)) {
		printk("ptrace: bad page directory %08lx\n",
		       pmd_val(*pgmiddle));
		pmd_clear(pgmiddle);
		return;
	}
	pgtable = pte_offset(pgmiddle, addr);
	if (!pte_present(*pgtable)) {
		do_no_page(tsk, vma, addr, 1);
		goto repeat;
	}
	page = pte_page(*pgtable);
	if (!pte_write(*pgtable)) {
		do_wp_page(tsk, vma, addr, 2);
		goto repeat;
	}
/* this is a hack for non-kernel-mapped video buffers and similar */
	if (page < high_memory) {
		*(unsigned long *) (page + (addr & ~PAGE_MASK)) = data;
		flush_page_to_ram (page);
	}
/* we're bypassing pagetables, so we have to set the dirty bit ourselves */
/* this should also re-instate whatever read-only mode there was before */
	*pgtable = pte_mkdirty(mk_pte(page, vma->vm_page_prot));
	flush_tlb_all();
}

pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
{
    pgd_t *pgd;
    pud_t *pud;
    pmd_t *pmd = NULL;

    pgd = pgd_offset(mm, addr);
    if (pgd_present(*pgd)) {
        pud = pud_offset(pgd, addr);
        if (pud_present(*pud))
            pmd = pmd_offset(pud, addr);
    }
    return (pte_t *) pmd;
}

static void shmedia_mapioaddr(unsigned long pa, unsigned long va,
			      unsigned long flags)
{
	pgd_t *pgdp;
	pud_t *pudp;
	pmd_t *pmdp;
	pte_t *ptep, pte;
	pgprot_t prot;

	pr_debug("shmedia_mapiopage pa %08lx va %08lx\n",  pa, va);

	if (!flags)
		flags = 1; /* 1 = CB0-1 device */

	pgdp = pgd_offset_k(va);
	if (pgd_none(*pgdp) || !pgd_present(*pgdp)) {
		pudp = (pud_t *)sh64_get_page();
		set_pgd(pgdp, __pgd((unsigned long)pudp | _KERNPG_TABLE));
	}

	pudp = pud_offset(pgdp, va);
	if (pud_none(*pudp) || !pud_present(*pudp)) {
		pmdp = (pmd_t *)sh64_get_page();
		set_pud(pudp, __pud((unsigned long)pmdp | _KERNPG_TABLE));
	}

	pmdp = pmd_offset(pudp, va);
	if (pmd_none(*pmdp) || !pmd_present(*pmdp)) {
		ptep = (pte_t *)sh64_get_page();
		set_pmd(pmdp, __pmd((unsigned long)ptep + _PAGE_TABLE));
	}

	prot = __pgprot(_PAGE_PRESENT | _PAGE_READ     | _PAGE_WRITE  |
			_PAGE_DIRTY   | _PAGE_ACCESSED | _PAGE_SHARED | flags);

	pte = pfn_pte(pa >> PAGE_SHIFT, prot);
	ptep = pte_offset_kernel(pmdp, va);

	if (!pte_none(*ptep) &&
	    pte_val(*ptep) != pte_val(pte))
		pte_ERROR(*ptep);

	set_pte(ptep, pte);

	flush_tlb_kernel_range(va, PAGE_SIZE);
}

/*
 * First Level Translation Fault Handler
 *
 * We enter here because the first level page table doesn't contain
 * a valid entry for the address.
 *
 * If the address is in kernel space (>= TASK_SIZE), then we are
 * probably faulting in the vmalloc() area.
 *
 * If the init_task's first level page tables contains the relevant
 * entry, we copy the it to this task.  If not, we send the process
 * a signal, fixup the exception, or oops the kernel.
 *
 * NOTE! We MUST NOT take any locks for this case. We may be in an
 * interrupt or a critical region, and should only copy the information
 * from the master page table, nothing more.
 */
int do_translation_fault(unsigned long addr, unsigned int fsr,
			 struct pt_regs *regs)
{
	struct task_struct *tsk;
	int offset;
	pgd_t *pgd, *pgd_k;
	pmd_t *pmd, *pmd_k;

	if (addr < TASK_SIZE)
		return do_page_fault(addr, fsr, regs);

	offset = __pgd_offset(addr);

	/*
	 * FIXME: CP15 C1 is write only on ARMv3 architectures.
	 * You really need to read the value in the page table
	 * register, not a copy.
	 */
	pgd = cpu_get_pgd() + offset;
	pgd_k = init_mm.pgd + offset;

	if (pgd_none(*pgd_k))
		goto bad_area;

#if 0	/* note that we are two-level */
	if (!pgd_present(*pgd))
		set_pgd(pgd, *pgd_k);
#endif

	pmd_k = pmd_offset(pgd_k, addr);
	pmd   = pmd_offset(pgd, addr);

	if (pmd_none(*pmd_k))
		goto bad_area;

	set_pmd(pmd, *pmd_k);
	return 0;

bad_area:
	tsk = current;

	do_bad_area(tsk, tsk->active_mm, addr, fsr, regs);
	return 0;
}

/*
 * First Level Translation Fault Handler
 *
 * We enter here because the first level page table doesn't contain
 * a valid entry for the address.
 *
 * If the address is in kernel space (>= TASK_SIZE), then we are
 * probably faulting in the vmalloc() area.
 *
 * If the init_task's first level page tables contains the relevant
 * entry, we copy the it to this task.  If not, we send the process
 * a signal, fixup the exception, or oops the kernel.
 *
 * NOTE! We MUST NOT take any locks for this case. We may be in an
 * interrupt or a critical region, and should only copy the information
 * from the master page table, nothing more.
 */
int do_translation_fault(unsigned long addr, int error_code, struct pt_regs *regs)
{
	struct task_struct *tsk;
	struct mm_struct *mm;
	int offset;
	pgd_t *pgd, *pgd_k;
	pmd_t *pmd, *pmd_k;

	if (addr < TASK_SIZE)
		return do_page_fault(addr, error_code, regs);

	offset = __pgd_offset(addr);

	/*
	 * FIXME: CP15 C1 is write only on ARMv3 architectures.
	 */
	pgd = cpu_get_pgd() + offset;
	pgd_k = init_mm.pgd + offset;

	if (pgd_none(*pgd_k))
		goto bad_area;

#if 0	/* note that we are two-level */
	if (!pgd_present(*pgd))
		set_pgd(pgd, *pgd_k);
#endif

	pmd_k = pmd_offset(pgd_k, addr);
	pmd   = pmd_offset(pgd, addr);

	if (pmd_none(*pmd_k))
		goto bad_area;

	set_pmd(pmd, *pmd_k);
	return 0;

bad_area:
	tsk = current;
	mm  = tsk->active_mm;

	do_bad_area(tsk, mm, addr, error_code, regs);
	return 0;
}

int exit_mm(struct mm_struct *mm)
{
	pmd_t *pmd;
	pgd_t *pgd;
	uint32_t pgdno, pmdno;
	physaddr_t pa;

	struct vm_area_struct* vma = mm->mmap;
	struct page *page;
	
	if(!mm || !mm->mm_pgd)
		return 0;

	if(!atomic_dec_and_test(&mm->mm_count))
		return 0;

	delete_all_vma(mm);

	for (pgdno = 0; pgdno < pgd_index(KERNEL_BASE_ADDR); pgdno++) {
		pgd = mm->mm_pgd + pgdno;
		if(!pgd_present(*pgd) || pgd_none(*pgd))
			continue;
		pmd_t* tmp = (pmd_t *)pgd_page_vaddr(*pgd);
		
		for (pmdno = 0; pmdno < PTRS_PER_PMD; pmdno++) {
			pmd = tmp +  pmdno;
			if(!pmd_present(*pmd) || pmd_none(*pmd))
				continue;
			struct page* p = virt2page(pmd_page_vaddr(*pmd));
			page_decref(p);
			pmd_set(pmd,0,0);
		}
		struct page* p = virt2page(pgd_page_vaddr(*pgd));
		page_decref(p);
		pgd_set(pgd,0,0);
	}

	page = virt2page((viraddr_t)mm->mm_pgd);
	page_free(page);
	kfree(mm);

	return 0;
}

/*
 * Insert the gateway page into a set of page tables, creating the
 * page tables if necessary.
 */
static void insert_gateway_page(pgd_t *pgd, unsigned long address)
{
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	BUG_ON(!pgd_present(*pgd));

	pud = pud_offset(pgd, address);
	BUG_ON(!pud_present(*pud));

	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd)) {
		pte = alloc_bootmem_pages(PAGE_SIZE);
		set_pmd(pmd, __pmd(_PAGE_TABLE | __pa(pte)));
	}

	pte = pte_offset_kernel(pmd, address);
	set_pte(pte, pfn_pte(__pa(gateway_page) >> PAGE_SHIFT, PAGE_READONLY));
}