Function pmap_change_props_locked

freebsd/amd64/amd64/pmap.c:9184–9423

}

static int
pmap_change_props_locked(vm_offset_t va, vm_size_t size, vm_prot_t prot,
    int mode, int flags)
{
	vm_offset_t base, offset, tmpva;
	vm_paddr_t pa_start, pa_end, pa_end1;
	pdp_entry_t *pdpe;
	pd_entry_t *pde, pde_bits, pde_mask;
	pt_entry_t *pte, pte_bits, pte_mask;
	int error;
	bool changed;

	PMAP_LOCK_ASSERT(kernel_pmap, MA_OWNED);
	base = trunc_page(va);
	offset = va & PAGE_MASK;
	size = round_page(offset + size);

	/*
	 * Only supported on kernel virtual addresses, including the direct
	 * map but excluding the recursive map.
	 */
	if (base < DMAP_MIN_ADDRESS)
		return (EINVAL);

	/*
	 * Construct our flag sets and masks.  "bits" is the subset of
	 * "mask" that will be set in each modified PTE.
	 *
	 * Mappings in the direct map are never allowed to be executable.
	 */
	pde_bits = pte_bits = 0;
	pde_mask = pte_mask = 0;
	if (mode != -1) {
		pde_bits |= pmap_cache_bits(kernel_pmap, mode, true);
		pde_mask |= X86_PG_PDE_CACHE;
		pte_bits |= pmap_cache_bits(kernel_pmap, mode, false);
		pte_mask |= X86_PG_PTE_CACHE;
	}
	if (prot != VM_PROT_NONE) {
		if ((prot & VM_PROT_WRITE) != 0) {
			pde_bits |= X86_PG_RW;
			pte_bits |= X86_PG_RW;
		}
		if ((prot & VM_PROT_EXECUTE) == 0 ||
		    va < VM_MIN_KERNEL_ADDRESS) {
			pde_bits |= pg_nx;
			pte_bits |= pg_nx;
		}
		pde_mask |= X86_PG_RW | pg_nx;
		pte_mask |= X86_PG_RW | pg_nx;
	}

	/*
	 * Pages that aren't mapped aren't supported.  Also break down 2MB pages
	 * into 4KB pages if required.
	 */
	for (tmpva = base; tmpva < base + size; ) {
		pdpe = pmap_pdpe(kernel_pmap, tmpva);