Function pmap_protect

freebsd/arm64/arm64/pmap.c:3286–3401

* Set the physical protection on the * specified range of this map as requested. */

 *	specified range of this map as requested.
 */
void
pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
{
	vm_offset_t va, va_next;
	pd_entry_t *l0, *l1, *l2;
	pt_entry_t *l3p, l3, mask, nbits;

	PMAP_ASSERT_STAGE1(pmap);
	KASSERT((prot & ~VM_PROT_ALL) == 0, ("invalid prot %x", prot));
	if (prot == VM_PROT_NONE) {
		pmap_remove(pmap, sva, eva);
		return;
	}

	mask = nbits = 0;
	if ((prot & VM_PROT_WRITE) == 0) {
		mask |= ATTR_S1_AP_RW_BIT | ATTR_SW_DBM;
		nbits |= ATTR_S1_AP(ATTR_S1_AP_RO);
	}
	if ((prot & VM_PROT_EXECUTE) == 0) {
		mask |= ATTR_S1_XN;
		nbits |= ATTR_S1_XN;
	}
	if (mask == 0)
		return;

	PMAP_LOCK(pmap);
	for (; sva < eva; sva = va_next) {
		l0 = pmap_l0(pmap, sva);
		if (pmap_load(l0) == 0) {
			va_next = (sva + L0_SIZE) & ~L0_OFFSET;
			if (va_next < sva)
				va_next = eva;
			continue;
		}

		va_next = (sva + L1_SIZE) & ~L1_OFFSET;
		if (va_next < sva)
			va_next = eva;
		l1 = pmap_l0_to_l1(l0, sva);
		if (pmap_load(l1) == 0)
			continue;
		if ((pmap_load(l1) & ATTR_DESCR_MASK) == L1_BLOCK) {
			KASSERT(va_next <= eva,
			    ("partial update of non-transparent 1G page "
			    "l1 %#lx sva %#lx eva %#lx va_next %#lx",
			    pmap_load(l1), sva, eva, va_next));
			MPASS((pmap_load(l1) & ATTR_SW_MANAGED) == 0);
			if ((pmap_load(l1) & mask) != nbits) {
				pmap_store(l1, (pmap_load(l1) & ~mask) | nbits);
				pmap_invalidate_page(pmap, sva);
			}
			continue;
		}

		va_next = (sva + L2_SIZE) & ~L2_OFFSET;
		if (va_next < sva)
			va_next = eva;