1 use std::cell::RefCell;
3 use std::collections::hash_map::Entry;
8 use rustc_data_structures::fx::FxHashMap;
9 use rustc_target::abi::{Size, HasDataLayout};
13 pub type MemoryExtra = RefCell<GlobalState>;
15 #[derive(Clone, Debug)]
16 pub struct GlobalState {
17 /// This is used as a map between the address of each allocation and its `AllocId`.
18 /// It is always sorted
19 pub int_to_ptr_map: Vec<(u64, AllocId)>,
20 /// The base address for each allocation. We cannot put that into
21 /// `AllocExtra` because function pointers also have a base address, and
22 /// they do not have an `AllocExtra`.
23 /// This is the inverse of `int_to_ptr_map`.
24 pub base_addr: FxHashMap<AllocId, u64>,
25 /// This is used as a memory address when a new pointer is casted to an integer. It
26 /// is always larger than any address that was previously made part of a block.
27 pub next_base_addr: u64,
30 impl Default for GlobalState {
31 fn default() -> Self {
33 int_to_ptr_map: Vec::default(),
34 base_addr: FxHashMap::default(),
35 next_base_addr: STACK_ADDR,
40 impl<'mir, 'tcx> GlobalState {
43 memory: &Memory<'mir, 'tcx, Evaluator<'mir, 'tcx>>,
44 ) -> InterpResult<'tcx, Pointer<Tag>> {
45 let global_state = memory.extra.intptrcast.borrow();
46 let pos = global_state.int_to_ptr_map.binary_search_by_key(&int, |(addr, _)| *addr);
48 // The int must be in-bounds after being cast to a pointer, so we error
49 // with `CheckInAllocMsg::InboundsTest`.
52 let (_, alloc_id) = global_state.int_to_ptr_map[pos];
53 // `int` is equal to the starting address for an allocation, the offset should be
54 // zero. The pointer is untagged because it was created from a cast
55 Pointer::new_with_tag(alloc_id, Size::from_bytes(0), Tag::Untagged)
57 Err(0) => throw_ub!(DanglingIntPointer(int, CheckInAllocMsg::InboundsTest)),
59 // This is the largest of the adresses smaller than `int`,
60 // i.e. the greatest lower bound (glb)
61 let (glb, alloc_id) = global_state.int_to_ptr_map[pos - 1];
62 // This never overflows because `int >= glb`
63 let offset = int - glb;
64 // If the offset exceeds the size of the allocation, this access is illegal
65 if offset <= memory.get_size_and_align(alloc_id, AllocCheck::MaybeDead)?.0.bytes() {
66 // This pointer is untagged because it was created from a cast
67 Pointer::new_with_tag(alloc_id, Size::from_bytes(offset), Tag::Untagged)
69 throw_ub!(DanglingIntPointer(int, CheckInAllocMsg::InboundsTest))
77 memory: &Memory<'mir, 'tcx, Evaluator<'mir, 'tcx>>,
78 ) -> InterpResult<'tcx, u64> {
79 let mut global_state = memory.extra.intptrcast.borrow_mut();
80 let global_state = &mut *global_state;
81 let id = ptr.alloc_id;
83 // There is nothing wrong with a raw pointer being cast to an integer only after
84 // it became dangling. Hence `MaybeDead`.
85 let (size, align) = memory.get_size_and_align(id, AllocCheck::MaybeDead)?;
87 let base_addr = match global_state.base_addr.entry(id) {
88 Entry::Occupied(entry) => *entry.get(),
89 Entry::Vacant(entry) => {
90 // This allocation does not have a base address yet, pick one.
91 // Leave some space to the previous allocation, to give it some chance to be less aligned.
93 let mut rng = memory.extra.rng.borrow_mut();
94 // This means that `(global_state.next_base_addr + slack) % 16` is uniformly distributed.
97 // From next_base_addr + slack, round up to adjust for alignment.
98 let base_addr = global_state.next_base_addr.checked_add(slack).unwrap();
99 let base_addr = Self::align_addr(base_addr, align.bytes());
100 entry.insert(base_addr);
102 "Assigning base address {:#x} to allocation {:?} (slack: {}, align: {})",
109 // Remember next base address. If this allocation is zero-sized, leave a gap
110 // of at least 1 to avoid two allocations having the same base address.
111 global_state.next_base_addr = base_addr.checked_add(max(size.bytes(), 1)).unwrap();
112 // Given that `next_base_addr` increases in each allocation, pushing the
113 // corresponding tuple keeps `int_to_ptr_map` sorted
114 global_state.int_to_ptr_map.push((base_addr, id));
120 // Sanity check that the base address is aligned.
121 debug_assert_eq!(base_addr % align.bytes(), 0);
122 // Add offset with the right kind of pointer-overflowing arithmetic.
123 let dl = memory.data_layout();
124 Ok(dl.overflowing_offset(base_addr, ptr.offset.bytes()).0)
127 /// Shifts `addr` to make it aligned with `align` by rounding `addr` to the smallest multiple
128 /// of `align` that is larger or equal to `addr`
129 fn align_addr(addr: u64, align: u64) -> u64 {
132 rem => addr.checked_add(align).unwrap() - rem,
142 fn test_align_addr() {
143 assert_eq!(GlobalState::align_addr(37, 4), 40);
144 assert_eq!(GlobalState::align_addr(44, 4), 44);