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prove: cursor_mut_at at mm::frame::linked_list #454

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prove: cursor_mut_at at mm::frame::linked_list #454

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4 changes: 3 additions & 1 deletion ostd/specs/mm/frame/linked_list/linked_list_owners.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -229,7 +229,8 @@ pub tracked struct LinkedListOwner<M: AnyFrameMeta + Repr<MetaSlotSmall>> {

impl<M: AnyFrameMeta + Repr<MetaSlotSmall>> Inv for LinkedListOwner<M> {
open spec fn inv(self) -> bool {
forall|i: int| 0 <= i < self.list.len() ==> self.inv_at(i)
&&& self.list.len() > 0 ==> self.list_id != 0
&&& forall|i: int| 0 <= i < self.list.len() ==> self.inv_at(i)
}
}

Expand Down Expand Up @@ -258,6 +259,7 @@ impl<M: AnyFrameMeta + Repr<MetaSlotSmall>> LinkedListOwner<M> {
}
&&& self.list[i].inv()
&&& self.list[i].in_list == self.list_id
&&& self.perms[i].inner_perms.in_list.value() == self.list_id
}

pub open spec fn view_helper(owners: Seq<LinkOwner>) -> Seq<LinkModel>
Expand Down
68 changes: 51 additions & 17 deletions ostd/src/mm/frame/linked_list.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -426,46 +426,79 @@ impl<M: AnyFrameMeta + Repr<MetaSlotSmall>> LinkedList<M> {
Tracked(owner): Tracked<LinkedListOwner<M>>,
-> cursor_owner: Tracked<Option<CursorOwner<M>>>,
requires
old(self).wf(owner),
owner.inv(),
old(regions).inv(),
has_safe_slot(frame)
&& !(exists|i: int| 0 <= i < owner.list.len() && owner.list[i].paddr == frame)
==> old(regions).slots.contains_key(frame_to_index(frame)),
has_safe_slot(frame)
&& !(exists|i: int| 0 <= i < owner.list.len() && owner.list[i].paddr == frame)
==> old(regions).slot_owners[frame_to_index(frame)].inner_perms.in_list.is_for(
old(regions).slots[frame_to_index(frame)].mem_contents().value().in_list,
),
has_safe_slot(frame)
&& !(exists|i: int| 0 <= i < owner.list.len() && owner.list[i].paddr == frame)
==> old(regions).slot_owners[frame_to_index(frame)].inner_perms.in_list.value() == 0,
ensures
// has_safe_slot(frame) && owner.list_id != 0 ==> r is Some,
!has_safe_slot(frame) ==> r is None,
r is Some ==> cursor_owner@ is Some,
r is Some ==> cursor_owner@.unwrap().inv(),
r is Some ==> cursor_owner@.unwrap().current().unwrap().paddr == frame,
r is Some ==> r.unwrap().wf(cursor_owner@.unwrap()),
)]
#[verifier::external_body]
pub fn cursor_mut_at(&mut self, frame: Paddr) -> Option<CursorMut<'_, M>>
{
let tracked mut slot_own = regions.slot_owners.tracked_remove(frame_to_index(frame));
let tracked mut inner_perms = slot_own.take_inner_perms();

if let Ok(slot_ptr) = get_slot(frame) {
let slot = slot_ptr.borrow(Tracked(&regions.slots[frame_to_index(frame)]));
proof_decl! {
let tracked slot_perm: &vstd::simple_pptr::PointsTo<MetaSlot>;
let tracked in_list_perm: &PermissionU64;
}
proof {
if exists|i: int| 0 <= i < owner.list.len() && owner.list[i].paddr == frame {
let ghost index = choose|i: int| 0 <= i < owner.list.len() && owner.list[i].paddr == frame;
assert(owner.inv_at(index));
owner.perms[index].pptr_implies_addr();
slot_perm = &owner.perms.tracked_borrow(index).points_to;
in_list_perm = &owner.perms.tracked_borrow(index).inner_perms.in_list;
} else {
regions.inv_implies_correct_addr(frame);
let tracked slot_own = regions.slot_owners.tracked_borrow(frame_to_index(frame));
slot_perm = regions.slots.tracked_borrow(frame_to_index(frame));
in_list_perm = &slot_own.inner_perms.in_list;
}
}
let slot = slot_ptr.borrow(Tracked(slot_perm));

let in_list = slot.in_list.load(Tracked(&mut inner_perms.in_list));
let in_list = slot.in_list.load(Tracked(in_list_perm));

let contains = in_list == #[verus_spec(with Tracked(&owner))]
self.lazy_get_id();

#[verus_spec(with Tracked(&regions.slots[frame_to_index(frame)]))]
#[verus_spec(with Tracked(slot_perm))]
let meta_ptr = slot.as_meta_ptr::<Link<M>>();

if contains {
proof {
slot_own.sync_inner(&inner_perms);
regions.slot_owners.tracked_insert(frame_to_index(frame), slot_own);
assert(exists|i: int| 0 <= i < owner.list.len() && owner.list[i].paddr == frame);
}

let ghost link = owner.list.filter(|link: LinkOwner| link.paddr == frame).first();
let ghost index = owner.list.index_of(link);
let ghost index = choose|i: int| 0 <= i < owner.list.len() && owner.list[i].paddr == frame;
let tracked cursor_owner = CursorOwner::cursor_mut_at_owner(owner, index);

proof {
assert(cursor_owner.inv());
assert(cursor_owner.current().unwrap().paddr == frame);
assert(cursor_owner.list_own.inv_at(index));
cursor_owner.list_own.perms[index].pptr_implies_addr();
assert(meta_ptr.addr() == frame);
assert(cursor_owner.list_own.perms[index].pptr().addr() == meta_ptr.addr());
assert(cursor_owner.list_own.perms[index].points_to.pptr().addr() == meta_ptr.ptr.addr());
assert(cursor_owner.list_own.perms[index].points_to.pptr() == meta_ptr.ptr);
}
proof_with!(|= Tracked(Some(cursor_owner)));
Some(CursorMut { list: self, current: Some(MetadataAsLink::cast_from_metadata(meta_ptr)) })
} else {
proof {
slot_own.sync_inner(&inner_perms);
regions.slot_owners.tracked_insert(frame_to_index(frame), slot_own);
}

proof_with!(|= Tracked(None));
None
}
Expand Down Expand Up @@ -556,6 +589,7 @@ impl<M: AnyFrameMeta + Repr<MetaSlotSmall>> LinkedList<M> {
)]
fn lazy_get_id(&mut self) -> (id: u64)
ensures
id != 0,
owner.list_id != 0 ==> id == owner.list_id,
{
unimplemented!()/* // FIXME: Self-incrementing IDs may overflow, while `core::pin::Pin`
Expand Down