Function pmap_copy

freebsd/amd64/amd64/pmap.c:7565–7736

* Copy the range specified by src_addr/len * from the source map to the range dst_addr/len * in the destination map. * * This routine is only advisory and need not do anything. */

 *	This routine is only advisory and need not do anything.
 */
void
pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr, vm_size_t len,
    vm_offset_t src_addr)
{
	struct rwlock *lock;
	pml4_entry_t *pml4e;
	pdp_entry_t *pdpe;
	pd_entry_t *pde, srcptepaddr;
	pt_entry_t *dst_pte, PG_A, PG_M, PG_V, ptetemp, *src_pte;
	vm_offset_t addr, end_addr, va_next;
	vm_page_t dst_pdpg, dstmpte, srcmpte;

	if (dst_addr != src_addr)
		return;

	if (dst_pmap->pm_type != src_pmap->pm_type)
		return;

	/*
	 * EPT page table entries that require emulation of A/D bits are
	 * sensitive to clearing the PG_A bit (aka EPT_PG_READ). Although
	 * we clear PG_M (aka EPT_PG_WRITE) concomitantly, the PG_U bit
	 * (aka EPT_PG_EXECUTE) could still be set. Since some EPT
	 * implementations flag an EPT misconfiguration for exec-only
	 * mappings we skip this function entirely for emulated pmaps.
	 */
	if (pmap_emulate_ad_bits(dst_pmap))
		return;

	end_addr = src_addr + len;
	lock = NULL;
	if (dst_pmap < src_pmap) {
		PMAP_LOCK(dst_pmap);
		PMAP_LOCK(src_pmap);
	} else {
		PMAP_LOCK(src_pmap);
		PMAP_LOCK(dst_pmap);
	}

	PG_A = pmap_accessed_bit(dst_pmap);
	PG_M = pmap_modified_bit(dst_pmap);
	PG_V = pmap_valid_bit(dst_pmap);

	for (addr = src_addr; addr < end_addr; addr = va_next) {
		KASSERT(addr < UPT_MIN_ADDRESS,
		    ("pmap_copy: invalid to pmap_copy page tables"));

		pml4e = pmap_pml4e(src_pmap, addr);
		if (pml4e == NULL || (*pml4e & PG_V) == 0) {
			va_next = (addr + NBPML4) & ~PML4MASK;
			if (va_next < addr)
				va_next = end_addr;
			continue;
		}

		va_next = (addr + NBPDP) & ~PDPMASK;
		if (va_next < addr)
			va_next = end_addr;