C++ pmd_clear函数代码示例

void free_pgd_slow(pgd_t *pgd)
{
	pmd_t *pmd;
	pte_t *pte;

	if (!pgd)
		return;

	/* pgd is always present and good */
	pmd = (pmd_t *)pgd;
	if (pmd_none(*pmd))
		goto free;
	if (pmd_bad(*pmd)) {
		pmd_ERROR(*pmd);
		pmd_clear(pmd);
		goto free;
	}

	pte = pte_offset(pmd, 0);
	pmd_clear(pmd);
	pte_free(pte);
	pmd_free(pmd);
free:
	free_pages((unsigned long) pgd, 2);
}

void free_pgd_slow(struct mm_struct *mm, pgd_t *pgd)
{
	unsigned long flags;
	pmd_t *pmd;
	pgtable_t pte;

	if (!pgd)
		return;

	/* pgd is always present and good */
	pmd = pmd_off(pgd + pgd_index(fcse_va_to_mva(mm, 0)), 0);
	if (pmd_none(*pmd))
		goto free;
	if (pmd_bad(*pmd)) {
		pmd_ERROR(*pmd);
		pmd_clear(pmd);
		goto free;
	}

	pte = pmd_pgtable(*pmd);
	pmd_clear(pmd);
	pte_free(mm, pte);
	pmd_free(mm, pmd);
free:
	pgd_list_lock(flags);
	pgd_list_del(pgd);
	pgd_list_unlock(flags);
	free_pages((unsigned long) pgd, 2);
}

void free_pgd_slow(struct mm_struct *mm, pgd_t *pgd)
{
	pmd_t *pmd;
	pgtable_t pte;

	if (!pgd)
		return;

	/* pgd is always present and good */
	pmd = pmd_off(pgd, 0);
	if (pmd_none(*pmd))
		goto free;
	if (pmd_bad(*pmd)) {
		pmd_ERROR(*pmd);
		pmd_clear(pmd);
		goto free;
	}

	pte = pmd_pgtable(*pmd);
	pmd_clear(pmd);
	pte_free(mm, pte);
	pmd_free(mm, pmd);
free:
	free_pages((unsigned long) pgd, 2);
}

static void clear_pmd_entry(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr)
{
	if (kvm_pmd_huge(*pmd)) {
		pmd_clear(pmd);
		kvm_tlb_flush_vmid_ipa(kvm, addr);
	} else {
		pte_t *pte_table = pte_offset_kernel(pmd, 0);
		pmd_clear(pmd);
		kvm_tlb_flush_vmid_ipa(kvm, addr);
		pte_free_kernel(NULL, pte_table);
	}
	put_page(virt_to_page(pmd));
}

/*
 * Note: this doesn't free the actual pages themselves. That
 * has been handled earlier when unmapping all the memory regions.
 */
static inline void free_one_pmd(pmd_t * dir)
{
	pte_t * pte;

	if (pmd_none(*dir))
		return;
	if (pmd_bad(*dir)) {
		printk("free_one_pmd: bad directory entry %08lx\n", pmd_val(*dir));
		pmd_clear(dir);
		return;
	}
	pte = pte_offset(dir, 0);
	pmd_clear(dir);
	pte_free(pte);
}

/*
 * Note: this doesn't free the actual pages themselves. That
 * has been handled earlier when unmapping all the memory regions.
 */
static inline void free_one_pmd(pmd_t * dir)
{
	pte_t * pte;

	if (pmd_none(*dir))
		return;
	if (pmd_bad(*dir)) {
		pmd_ERROR(*dir);
		pmd_clear(dir);
		return;
	}
	pte = pte_offset(dir, 0);
	pmd_clear(dir);
	pte_free(pte);
}

static inline int unuse_pmd(struct vm_area_struct * vma, pmd_t *dir,
	unsigned long address, unsigned long size, unsigned long offset,
	unsigned int type, unsigned long page)
{
	pte_t * pte;
	unsigned long end;

	if (pmd_none(*dir))
		return 0;
	if (pmd_bad(*dir)) {
		printk("unuse_pmd: bad pmd (%08lx)\n", pmd_val(*dir));
		pmd_clear(dir);
		return 0;
	}
	pte = pte_offset(dir, address);
	offset += address & PMD_MASK;
	address &= ~PMD_MASK;
	end = address + size;
	if (end > PMD_SIZE)
		end = PMD_SIZE;
	do {
		if (unuse_pte(vma, offset+address-vma->vm_start, pte, type, page))
			return 1;
		address += PAGE_SIZE;
		pte++;
	} while (address < end);
	return 0;
}

static inline void unswap_pmd(struct vm_area_struct * vma, pmd_t *dir,
			      unsigned long address, unsigned long size,
			      unsigned long offset, unsigned long entry,
			      unsigned long page /* , int isswap */)
{
	pte_t * pte;
	unsigned long end;

	if (pmd_none(*dir))
		return;
	if (pmd_bad(*dir)) {
		printk("unswap_pmd: bad pmd (%08lx)\n", pmd_val(*dir));
		pmd_clear(dir);
		return;
	}
	pte = pte_offset(dir, address);
	offset += address & PMD_MASK;
	address &= ~PMD_MASK;
	end = address + size;
	if (end > PMD_SIZE)
		end = PMD_SIZE;
	do {
		unswap_pte(vma, offset+address-vma->vm_start, pte, entry,
			   page /* , isswap */);
		address += PAGE_SIZE;
		pte++;
	} while (address < end);
}

static inline pte_t *get_one_pte(struct mm_struct *mm, unsigned long addr)
{
	pgd_t * pgd;
	pmd_t * pmd;
	pte_t * pte = NULL;

	pgd = pgd_offset(mm, addr);
	if (pgd_none(*pgd))
		goto end;
	if (pgd_bad(*pgd)) {
		pgd_ERROR(*pgd);
		pgd_clear(pgd);
		goto end;
	}

	pmd = pmd_offset(pgd, addr);
	if (pmd_none(*pmd))
		goto end;
	if (pmd_bad(*pmd)) {
		pmd_ERROR(*pmd);
		pmd_clear(pmd);
		goto end;
	}

	pte = pte_offset(pmd, addr);
	if (pte_none(*pte))
		pte = NULL;
end:
	return pte;
}

/*
 * Section support is unsafe on SMP - If you iounmap and ioremap a region,
 * the other CPUs will not see this change until their next context switch.
 * Meanwhile, (eg) if an interrupt comes in on one of those other CPUs
 * which requires the new ioremap'd region to be referenced, the CPU will
 * reference the _old_ region.
 *
 * Note that get_vm_area_caller() allocates a guard 4K page, so we need to
 * mask the size back to 4MB aligned or we will overflow in the loop below.
 */
static void unmap_area_sections(unsigned long virt, unsigned long size)
{
	unsigned long addr = virt, end = virt + (size & ~(SZ_4M - 1));
	pgd_t *pgd;

	flush_cache_vunmap(addr, end);
	pgd = pgd_offset_k(addr);
	do {
		pmd_t pmd, *pmdp = pmd_offset((pud_t *)pgd, addr);

		pmd = *pmdp;
		if (!pmd_none(pmd)) {
			/*
			 * Clear the PMD from the page table, and
			 * increment the kvm sequence so others
			 * notice this change.
			 *
			 * Note: this is still racy on SMP machines.
			 */
			pmd_clear(pmdp);

			/*
			 * Free the page table, if there was one.
			 */
			if ((pmd_val(pmd) & PMD_TYPE_MASK) == PMD_TYPE_TABLE)
				pte_free_kernel(&init_mm, pmd_page_vaddr(pmd));
		}

		addr += PGDIR_SIZE;
		pgd++;
	} while (addr < end);

	flush_tlb_kernel_range(virt, end);
}

/*
 * This function zeroes out partial mmap'ed pages at truncation time..
 */
static void partial_clear(struct vm_area_struct *vma, unsigned long address)
{
	pgd_t *page_dir;
	pmd_t *page_middle;
	pte_t *page_table, pte;

	page_dir = pgd_offset(vma->vm_mm, address);
	if (pgd_none(*page_dir))
		return;
	if (pgd_bad(*page_dir)) {
		printk("bad page table directory entry %p:[%lx]\n", page_dir, pgd_val(*page_dir));
		pgd_clear(page_dir);
		return;
	}
	page_middle = pmd_offset(page_dir, address);
	if (pmd_none(*page_middle))
		return;
	if (pmd_bad(*page_middle)) {
		printk("bad page table directory entry %p:[%lx]\n", page_dir, pgd_val(*page_dir));
		pmd_clear(page_middle);
		return;
	}
	page_table = pte_offset(page_middle, address);
	pte = *page_table;
	if (!pte_present(pte))
		return;
	flush_cache_page(vma, address);
	address &= ~PAGE_MASK;
	address += pte_page(pte);
	if (address >= high_memory)
		return;
	memset((void *) address, 0, PAGE_SIZE - (address & ~PAGE_MASK));
	flush_page_to_ram(pte_page(pte));
}

static inline void zap_pte_range(pmd_t * pmd, unsigned long address, unsigned long size)
{
	pte_t * pte;

	if (pmd_none(*pmd))
		return;
	if (pmd_bad(*pmd)) {
		printk("zap_pte_range: bad pmd (%08lx)\n", pmd_val(*pmd));
		pmd_clear(pmd);
		return;
	}
	pte = pte_offset(pmd, address);
	address &= ~PMD_MASK;
	if (address + size > PMD_SIZE)
		size = PMD_SIZE - address;
	size >>= PAGE_SHIFT;
	for (;;) {
		pte_t page;
		if (!size)
			break;
		page = *pte;
		pte++;
		size--;
		if (pte_none(page))
			continue;
		pte_clear(pte-1);
		free_pte(page);
	}
}

static inline int copy_pte_range(pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long address, unsigned long size, int cow)
{
	pte_t * src_pte, * dst_pte;
	unsigned long end;

	if (pmd_none(*src_pmd))
		return 0;
	if (pmd_bad(*src_pmd)) {
		printk("copy_pte_range: bad pmd (%08lx)\n", pmd_val(*src_pmd));
		pmd_clear(src_pmd);
		return 0;
	}
	src_pte = pte_offset(src_pmd, address);
	if (pmd_none(*dst_pmd)) {
		if (!pte_alloc(dst_pmd, 0))
			return -ENOMEM;
	}
	dst_pte = pte_offset(dst_pmd, address);
	address &= ~PMD_MASK;
	end = address + size;
	if (end >= PMD_SIZE)
		end = PMD_SIZE;
	do {
		/* I would like to switch arguments here, to make it
		 * consistent with copy_xxx_range and memcpy syntax.
		 */
		copy_one_pte(src_pte++, dst_pte++, cow);
		address += PAGE_SIZE;
	} while (address < end);
	return 0;
}

static void unmap_area_sections(unsigned long virt, unsigned long size)
{
    unsigned long addr = virt, end = virt + (size & ~(SZ_1M - 1));
    pgd_t *pgd;
    pud_t *pud;
    pmd_t *pmdp;

    flush_cache_vunmap(addr, end);
    pgd = pgd_offset_k(addr);
    pud = pud_offset(pgd, addr);
    pmdp = pmd_offset(pud, addr);
    do {
        pmd_t pmd = *pmdp;

        if (!pmd_none(pmd)) {
            pmd_clear(pmdp);
            init_mm.context.kvm_seq++;

            if ((pmd_val(pmd) & PMD_TYPE_MASK) == PMD_TYPE_TABLE)
                pte_free_kernel(&init_mm, pmd_page_vaddr(pmd));
        }

        addr += PMD_SIZE;
        pmdp += 2;
    } while (addr < end);

    if (current->active_mm->context.kvm_seq != init_mm.context.kvm_seq)
        __check_kvm_seq(current->active_mm);

    flush_tlb_kernel_range(virt, end);
}

static void teardown_huge_pte(hugepte_t *ptep)
{
	int i;

	for (i = 0; i < HUGEPTE_BATCH_SIZE; i++)
		pmd_clear((pmd_t *)(ptep+i));
}