Function vm_map_lookup

freebsd/vm/vm_map.c:4940–5103

* vm_map_lookup: * * Finds the VM object, offset, and * protection for a given virtual address in the * specified map, assuming a page fault of the * type specified. * * Leaves the map in question locked for read; return * values are guaranteed until a vm_map_lookup_done * call is performed. Note that the map argument * is in/out; the returned map must be used in * the call to vm_map_l

 *	remain the same.
 */
int
vm_map_lookup(vm_map_t *var_map,		/* IN/OUT */
	      vm_offset_t vaddr,
	      vm_prot_t fault_typea,
	      vm_map_entry_t *out_entry,	/* OUT */
	      vm_object_t *object,		/* OUT */
	      vm_pindex_t *pindex,		/* OUT */
	      vm_prot_t *out_prot,		/* OUT */
	      boolean_t *wired)			/* OUT */
{
	vm_map_entry_t entry;
	vm_map_t map = *var_map;
	vm_prot_t prot;
	vm_prot_t fault_type;
	vm_object_t eobject;
	vm_size_t size;
	struct ucred *cred;

RetryLookup:

	vm_map_lock_read(map);

RetryLookupLocked:
	/*
	 * Lookup the faulting address.
	 */
	if (!vm_map_lookup_entry(map, vaddr, out_entry)) {
		vm_map_unlock_read(map);
		return (KERN_INVALID_ADDRESS);
	}

	entry = *out_entry;

	/*
	 * Handle submaps.
	 */
	if (entry->eflags & MAP_ENTRY_IS_SUB_MAP) {
		vm_map_t old_map = map;

		*var_map = map = entry->object.sub_map;
		vm_map_unlock_read(old_map);
		goto RetryLookup;
	}

	/*
	 * Check whether this task is allowed to have this page.
	 */
	prot = entry->protection;
	if ((fault_typea & VM_PROT_FAULT_LOOKUP) != 0) {
		fault_typea &= ~VM_PROT_FAULT_LOOKUP;
		if (prot == VM_PROT_NONE && map != kernel_map &&
		    (entry->eflags & MAP_ENTRY_GUARD) != 0 &&
		    (entry->eflags & (MAP_ENTRY_STACK_GAP_DN |
		    MAP_ENTRY_STACK_GAP_UP)) != 0 &&
		    vm_map_growstack(map, vaddr, entry) == KERN_SUCCESS)
			goto RetryLookupLocked;
	}
	fault_type = fault_typea & VM_PROT_ALL;