1 //! This module contains everything needed to instantiate an interpreter.
2 //! This separation exists to ensure that no fancy miri features like
3 //! interpreting common C functions leak into CTFE.
5 use std::borrow::{Borrow, Cow};
8 use rustc::hir::def_id::DefId;
10 use rustc::ty::{self, Ty, TyCtxt};
14 Allocation, AllocId, InterpResult, Scalar, AllocationExtra,
15 InterpCx, PlaceTy, OpTy, ImmTy, MemoryKind, Pointer, Memory,
19 /// Data returned by Machine::stack_pop,
20 /// to provide further control over the popping of the stack frame
21 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
22 pub enum StackPopInfo {
23 /// Indicates that we have just started unwinding
24 /// as the result of panic
27 /// Indicates that we performed a normal return
30 /// Indicates that we should stop unwinding,
31 /// as we've reached a catch frame
35 /// Whether this kind of memory is allowed to leak
36 pub trait MayLeak: Copy {
37 fn may_leak(self) -> bool;
40 /// The functionality needed by memory to manage its allocations
41 pub trait AllocMap<K: Hash + Eq, V> {
42 /// Tests if the map contains the given key.
43 /// Deliberately takes `&mut` because that is sufficient, and some implementations
44 /// can be more efficient then (using `RefCell::get_mut`).
45 fn contains_key<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> bool
48 /// Inserts a new entry into the map.
49 fn insert(&mut self, k: K, v: V) -> Option<V>;
51 /// Removes an entry from the map.
52 fn remove<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> Option<V>
55 /// Returns data based the keys and values in the map.
56 fn filter_map_collect<T>(&self, f: impl FnMut(&K, &V) -> Option<T>) -> Vec<T>;
58 /// Returns a reference to entry `k`. If no such entry exists, call
59 /// `vacant` and either forward its error, or add its result to the map
60 /// and return a reference to *that*.
64 vacant: impl FnOnce() -> Result<V, E>
67 /// Returns a mutable reference to entry `k`. If no such entry exists, call
68 /// `vacant` and either forward its error, or add its result to the map
69 /// and return a reference to *that*.
73 vacant: impl FnOnce() -> Result<V, E>
74 ) -> Result<&mut V, E>;
77 fn get(&self, k: K) -> Option<&V> {
78 self.get_or(k, || Err(())).ok()
82 fn get_mut(&mut self, k: K) -> Option<&mut V> {
83 self.get_mut_or(k, || Err(())).ok()
87 /// Methods of this trait signifies a point where CTFE evaluation would fail
88 /// and some use case dependent behaviour can instead be applied.
89 pub trait Machine<'mir, 'tcx>: Sized {
90 /// Additional memory kinds a machine wishes to distinguish from the builtin ones
91 type MemoryKinds: ::std::fmt::Debug + MayLeak + Eq + 'static;
93 /// Tag tracked alongside every pointer. This is used to implement "Stacked Borrows"
94 /// <https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html>.
95 /// The `default()` is used for pointers to consts, statics, vtables and functions.
96 type PointerTag: ::std::fmt::Debug + Copy + Eq + Hash + 'static;
98 /// Machines can define extra (non-instance) things that represent values of function pointers.
99 /// For example, Miri uses this to return a fucntion pointer from `dlsym`
100 /// that can later be called to execute the right thing.
101 type ExtraFnVal: ::std::fmt::Debug + Copy;
103 /// Extra data stored in every call frame.
106 /// Extra data stored in memory. A reference to this is available when `AllocExtra`
107 /// gets initialized, so you can e.g., have an `Rc` here if there is global state you
108 /// need access to in the `AllocExtra` hooks.
111 /// Extra data stored in every allocation.
112 type AllocExtra: AllocationExtra<Self::PointerTag> + 'static;
114 /// Memory's allocation map
118 (MemoryKind<Self::MemoryKinds>, Allocation<Self::PointerTag, Self::AllocExtra>)
123 /// The memory kind to use for copied statics -- or None if statics should not be mutated
124 /// and thus any such attempt will cause a `ModifiedStatic` error to be raised.
125 /// Statics are copied under two circumstances: When they are mutated, and when
126 /// `tag_allocation` or `find_foreign_static` (see below) returns an owned allocation
127 /// that is added to the memory so that the work is not done twice.
128 const STATIC_KIND: Option<Self::MemoryKinds>;
130 /// Whether memory accesses should be alignment-checked.
131 const CHECK_ALIGN: bool;
133 /// Whether to enforce the validity invariant
134 fn enforce_validity(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool;
136 /// Called before a basic block terminator is executed.
137 /// You can use this to detect endlessly running programs.
138 fn before_terminator(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx>;
140 /// Entry point to all function calls.
142 /// Returns either the mir to use for the call, or `None` if execution should
143 /// just proceed (which usually means this hook did all the work that the
144 /// called function should usually have done). In the latter case, it is
145 /// this hook's responsibility to call `goto_block(ret)` to advance the instruction pointer!
146 /// (This is to support functions like `__rust_maybe_catch_panic` that neither find a MIR
147 /// nor just jump to `ret`, but instead push their own stack frame.)
148 /// Passing `dest`and `ret` in the same `Option` proved very annoying when only one of them
151 ecx: &mut InterpCx<'mir, 'tcx, Self>,
152 instance: ty::Instance<'tcx>,
153 args: &[OpTy<'tcx, Self::PointerTag>],
154 dest: Option<PlaceTy<'tcx, Self::PointerTag>>,
155 ret: Option<mir::BasicBlock>,
156 unwind: Option<mir::BasicBlock>
157 ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>>;
159 /// Execute `fn_val`. it is the hook's responsibility to advance the instruction
160 /// pointer as appropriate.
162 ecx: &mut InterpCx<'mir, 'tcx, Self>,
163 fn_val: Self::ExtraFnVal,
164 args: &[OpTy<'tcx, Self::PointerTag>],
165 dest: Option<PlaceTy<'tcx, Self::PointerTag>>,
166 ret: Option<mir::BasicBlock>,
167 ) -> InterpResult<'tcx>;
169 /// Directly process an intrinsic without pushing a stack frame.
170 /// If this returns successfully, the engine will take care of jumping to the next block.
172 ecx: &mut InterpCx<'mir, 'tcx, Self>,
174 instance: ty::Instance<'tcx>,
175 args: &[OpTy<'tcx, Self::PointerTag>],
176 dest: Option<PlaceTy<'tcx, Self::PointerTag>>,
177 ) -> InterpResult<'tcx>;
179 /// Called for read access to a foreign static item.
181 /// This will only be called once per static and machine; the result is cached in
182 /// the machine memory. (This relies on `AllocMap::get_or` being able to add the
183 /// owned allocation to the map even when the map is shared.)
185 /// This allocation will then be fed to `tag_allocation` to initialize the "extra" state.
186 fn find_foreign_static(
189 ) -> InterpResult<'tcx, Cow<'tcx, Allocation>>;
191 /// Called for all binary operations where the LHS has pointer type.
193 /// Returns a (value, overflowed) pair if the operation succeeded
195 ecx: &InterpCx<'mir, 'tcx, Self>,
197 left: ImmTy<'tcx, Self::PointerTag>,
198 right: ImmTy<'tcx, Self::PointerTag>,
199 ) -> InterpResult<'tcx, (Scalar<Self::PointerTag>, bool, Ty<'tcx>)>;
201 /// Heap allocations via the `box` keyword.
203 ecx: &mut InterpCx<'mir, 'tcx, Self>,
204 dest: PlaceTy<'tcx, Self::PointerTag>,
205 ) -> InterpResult<'tcx>;
207 /// Called to read the specified `local` from the `frame`.
209 _ecx: &InterpCx<'mir, 'tcx, Self>,
210 frame: &Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>,
212 ) -> InterpResult<'tcx, Operand<Self::PointerTag>> {
213 frame.locals[local].access()
216 /// Called before a `StaticKind::Static` value is accessed.
217 fn before_access_static(
218 _allocation: &Allocation,
219 ) -> InterpResult<'tcx> {
223 /// Called to initialize the "extra" state of an allocation and make the pointers
224 /// it contains (in relocations) tagged. The way we construct allocations is
225 /// to always first construct it without extra and then add the extra.
226 /// This keeps uniform code paths for handling both allocations created by CTFE
227 /// for statics, and allocations ceated by Miri during evaluation.
229 /// `kind` is the kind of the allocation being tagged; it can be `None` when
230 /// it's a static and `STATIC_KIND` is `None`.
232 /// This should avoid copying if no work has to be done! If this returns an owned
233 /// allocation (because a copy had to be done to add tags or metadata), machine memory will
234 /// cache the result. (This relies on `AllocMap::get_or` being able to add the
235 /// owned allocation to the map even when the map is shared.)
237 /// For static allocations, the tag returned must be the same as the one returned by
238 /// `tag_static_base_pointer`.
239 fn tag_allocation<'b>(
240 memory_extra: &Self::MemoryExtra,
242 alloc: Cow<'b, Allocation>,
243 kind: Option<MemoryKind<Self::MemoryKinds>>,
244 ) -> (Cow<'b, Allocation<Self::PointerTag, Self::AllocExtra>>, Self::PointerTag);
246 /// Return the "base" tag for the given static allocation: the one that is used for direct
247 /// accesses to this static/const/fn allocation.
249 /// Be aware that requesting the `Allocation` for that `id` will lead to cycles
250 /// for cyclic statics!
251 fn tag_static_base_pointer(
252 memory_extra: &Self::MemoryExtra,
254 ) -> Self::PointerTag;
256 /// Executes a retagging operation
259 _ecx: &mut InterpCx<'mir, 'tcx, Self>,
260 _kind: mir::RetagKind,
261 _place: PlaceTy<'tcx, Self::PointerTag>,
262 ) -> InterpResult<'tcx> {
266 /// Called immediately before a new stack frame got pushed
267 fn stack_push(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx, Self::FrameExtra>;
269 /// Called immediately after a stack frame gets popped
271 _ecx: &mut InterpCx<'mir, 'tcx, Self>,
272 _extra: Self::FrameExtra,
273 ) -> InterpResult<'tcx, StackPopInfo> {
274 // By default, we do not support unwinding from panics
275 Ok(StackPopInfo::Normal)
279 _mem: &Memory<'mir, 'tcx, Self>,
281 ) -> InterpResult<'tcx, Pointer<Self::PointerTag>> {
283 err_unsup!(InvalidNullPointerUsage)
285 err_unsup!(ReadBytesAsPointer)
290 _mem: &Memory<'mir, 'tcx, Self>,
291 _ptr: Pointer<Self::PointerTag>,
292 ) -> InterpResult<'tcx, u64>;