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