1 use std::cell::RefCell;
2 use std::collections::{HashMap, hash_map::Entry};
7 use rustc::ty::layout::HasDataLayout;
8 use rustc_mir::interpret::{AllocId, Pointer, InterpResult, Memory, AllocCheck, PointerArithmetic};
9 use rustc_target::abi::Size;
11 use crate::{Evaluator, Tag, STACK_ADDR};
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: HashMap<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: HashMap::default(),
35 next_base_addr: STACK_ADDR,
40 impl<'mir, 'tcx> GlobalState {
43 memory: &Memory<'mir, 'tcx, Evaluator<'tcx>>,
44 ) -> InterpResult<'tcx, Pointer<Tag>> {
45 let global_state = memory.extra.intptrcast.borrow();
47 match global_state.int_to_ptr_map.binary_search_by_key(&int, |(addr, _)| *addr) {
49 let (_, alloc_id) = global_state.int_to_ptr_map[pos];
50 // `int` is equal to the starting address for an allocation, the offset should be
51 // zero. The pointer is untagged because it was created from a cast
52 Ok(Pointer::new_with_tag(alloc_id, Size::from_bytes(0), Tag::Untagged))
54 Err(0) => err!(DanglingPointerDeref),
56 // This is the largest of the adresses smaller than `int`,
57 // i.e. the greatest lower bound (glb)
58 let (glb, alloc_id) = global_state.int_to_ptr_map[pos - 1];
59 // This never overflows because `int >= glb`
60 let offset = int - glb;
61 // If the offset exceeds the size of the allocation, this access is illegal
62 if offset <= memory.get(alloc_id)?.bytes.len() as u64 {
63 // This pointer is untagged because it was created from a cast
64 Ok(Pointer::new_with_tag(alloc_id, Size::from_bytes(offset), Tag::Untagged))
66 err!(DanglingPointerDeref)
74 memory: &Memory<'mir, 'tcx, Evaluator<'tcx>>,
75 ) -> InterpResult<'tcx, u64> {
76 let mut global_state = memory.extra.intptrcast.borrow_mut();
77 let global_state = &mut *global_state;
79 // There is nothing wrong with a raw pointer being cast to an integer only after
80 // it became dangling. Hence `MaybeDead`.
81 let (size, align) = memory.get_size_and_align(ptr.alloc_id, AllocCheck::MaybeDead)?;
83 let base_addr = match global_state.base_addr.entry(ptr.alloc_id) {
84 Entry::Occupied(entry) => *entry.get(),
85 Entry::Vacant(entry) => {
86 // This allocation does not have a base address yet, pick one.
87 // Leave some space to the previous allocation, to give it some chance to be less aligned.
89 let mut rng = memory.extra.rng.as_ref().unwrap().borrow_mut();
90 // This means that `(global_state.next_base_addr + slack) % 16` is uniformly distributed.
93 // From next_base_addr + slack, round up to adjust for alignment.
94 let base_addr = Self::align_addr(global_state.next_base_addr + slack, align.bytes());
95 entry.insert(base_addr);
97 "Assigning base address {:#x} to allocation {:?} (slack: {}, align: {})",
98 base_addr, ptr.alloc_id, slack, align.bytes(),
101 // Remember next base address. If this allocation is zero-sized, leave a gap
102 // of at least 1 to avoid two allocations having the same base address.
103 global_state.next_base_addr = base_addr + max(size.bytes(), 1);
104 // Given that `next_base_addr` increases in each allocation, pushing the
105 // corresponding tuple keeps `int_to_ptr_map` sorted
106 global_state.int_to_ptr_map.push((base_addr, ptr.alloc_id));
112 debug_assert_eq!(base_addr % align.bytes(), 0); // sanity check
113 // Add offset with the right kind of pointer-overflowing arithmetic.
114 let dl = memory.data_layout();
115 Ok(dl.overflowing_offset(base_addr, ptr.offset.bytes()).0)
118 /// Shifts `addr` to make it aligned with `align` by rounding `addr` to the smallest multiple
119 /// of `align` that is larger or equal to `addr`
120 fn align_addr(addr: u64, align: u64) -> u64 {
123 rem => addr + align - rem
133 fn test_align_addr() {
134 assert_eq!(GlobalState::align_addr(37, 4), 40);
135 assert_eq!(GlobalState::align_addr(44, 4), 44);